BINDING UST m , m
CARNEGIE INSTITUTION OF WASHINGTON
Publication No. 289, Vol. II
1928
/
CLIMATIC CYCLES AND TREE-GROWTH
VOLUME II
A STUDY OF THE ANNUAL RINGS OF TREES IN
RELATION TO CLIMATE AND SOLAR ACTIVITY
BY
A. E. DOUGLASS
Director of Steward Observatory, University of Arizona
Published by the Carnegie Institution of Washington
Washington, 1928
i
7vr
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J. B. LIPPINCOTT COMPANY
EAST WASHINGTON SQUARE
PHILADELPHIA, PENNA.
CONTENTS
PAGE
I. Introduction 3
Affiliations 3
Development 4
Cooperation 5
Acknowledgments 6
Previous work 7
II. Tree selection 8
Species 8
Location: grouping, soil, topography,
altitude 12
Condition: injuries, fire scars 14
Collection purposes: cycles and secu-
lar changes, age estimates 15
III. Radials 17
Selection 17
Living trees: place and direction of
boring 17
Fallen trees 19
Stumps: v-cut and its location 19
Preparing the radial 21
Radial studies 22
Circuit uniformity: eccentricity,
lobes and gross rings 22
Vertical uniformity: tests at
different heights 24
IV. Rings 28
Selection in group 28
Mean conformity 28
Mean sensitivity 29
Selection within record 30
Parts of tree's record: infancy,
youth, maturity, age 30
Ring errors : superfluous, missing,
reinforced, and false rings 31
V. Instruments and technique 34
Collecting tools : saws, borers, paraffin
treatment 34
Measuring instruments 37
Early forms 37
Plotting micrometer; auto-plot . . 37
Longitudinal plotter; long-plot. . 39
Clerical operations 40
Standardizing 40
Cycle plots: skeleton plots,
smoothing, Hanning 42
The cyclograph (periodograph) 45
Comparison of analyzing methods 45
Principle of the cyclograph 46
The White cyclograph 47
Cycloscope 50
VI. Tree records: length 51
Old sequoia records 51
Third sequoia trip, 1919 51
Fourth sequoia trip, 1924 52
Fifth sequoia trip, 1925 54
Coast redwood records 55
Santa Cruz group, 1921 55
Scotia trip, 1925 55
Deficiency of the coast redwood 56
PAGE
VI. Tree records: length — continued
Old pine records 57
Search for old trees; 500- and
640-year pines, burnt centers . 57
Prehistoric material 59
California and Arizona cross-
dating 61
Charleston Mountain trip 61
VII. Tree records: geographical dis-
tribution 63
Western circuit, 1925 63
Western contours and rainfall ... 64
The three zones 64
The Pueblo area 65
Southwestern contours 66
Western pine groups: statistics and
treatment 67
Arizona region 68
First Flagstaff group 68
Flagstaff 500-year group 69
Fort Valley group 69
High-level group 71
Flagstaff shadow group 71
Flagstaff northeast group 72
Grand Canyon group 72
Dixie Forest (Utah) group 73
Upper Rim group 73
Lower Rim group 74
Cibecue group 74
Pinal Mountain group 75
Catalina Mountain group 75
Santa Rita group 76
The Rocky Mountain zone 77
Yellowstone group 77
Laramie, Wyoming, group 77
Clements's Pike's Peak group . . 77
Pike's Peak Timberline group . . 79
Pike's Peak Basin group 79
Upper North Transect group ... 79
Lower North Transect group ... 80
South Transect group 80
Brook group of Douglas fir ... . 80
Brook group of Engelmann
Spruce 81
Cloudcroft, New Mexico, group. 81
Santa Fe group 82
Basin Mountain Upper group ... 82
Basin Mountain Lower group ... 83
Aztec East group 83
The Coast zone 83
Boise, Idaho, group 83
Baker, Oregon, group 85
Dalles group 85
Oregon Coast group 85
Klamath Falls group 86
Plumas County group 86
Calaveras group of pines 87
Big Creek group 87
Springville group of pines 88
Mount Wilson group 88
VI
CONTENTS
PAGE
VII. Tree records: geographical dis-
tribution. The Coast zone —
continued
San Bernardino group 89
Charleston Mountain group .... 89
Pine Valley group 90
Miscellaneous groups 90
Sequoias 90
Coast redwoods 91
Arizona groups 91
Other western groups 91
North American groups 92
Foreign groups 93
VIII. Environment 94
Effects in trees 94
Climate : single and double rings . 94
Rainfall correlations: Prescott,
Flagstaff, Cibecue drought
record; sequoia 97
Conservation: reversed and dis-
torted effects 10°
Other climatic correlations; wind 102
Topography 102
Sequoia topography: ring type
and moisture, sensitivity and
cycle lag 103
Pike's Peak topography; kind
of tree I06
San Francisco Peaks; altitude,
shadow effect, and soil 107
Changing conditions : shade, drain-
age, soil, and grouping 110
Environment indicators Ill
Evidence in individual rings .... Ill
PAGE
VIII. Environment. Environment indi-
cators— continued
Evidence in single trees Ill
Changing ring-size 112
IX. Cycles H3
Cycle origins 1 13
Solar theory: sunspots, rotation,
radiation 113
Terrestrial reaction: tempera-
tures, droughts, electrostatics,
glacial varves, ocean rotation,
etc H5
Cycles in tree-growth 117
Cycle reliability: short and long
cycles, criteria and tests 117
The periodocrite 1 19
Zone centers and their mean
curves 120
Meteorological areas; the prob-
lem of combination 122
Cycles in western zones: arcigram,
zone summaries, sequoia cycles 123
Solar records in tree-growth ; histori-
cal confirmation, dearth cycles,
wet and dry climatic effects. . . . 125
Solar cycles, historical changes, cli-
matic patterns 127
Cyclograms 130
Cycles and climate; cautions; possible
future Flagstaff variations 133
Summary 136
Appendix 139
Tables or group averages, standard-
ized 139
Bibliography 159
ILLUSTRATIONS
PLATES
PAGE
Plate 1.
A. Fire injury on D-12 (stump) showing
repair and gross rings and in-
closed bark 14
B. Center of oldest sequoia, D-21, show-
ing ring grown in 1305 B.C.; three
pins stand at 1300 b.c 14
Plate 2.
A. Weathering in 60 years, CV-4; bark
gone, sap wood mostly gone; Cala-
veras Grove 20
B. Weathering in 125 years; CV-3,
sapwood and center entirely
gone ; Calaveras Grove 20
Plate 3.
A. Forms of v-cut on stumps 22
B. Complacent sequoia rings, D-8,
grown in wet basin 22
C. Sensitive sequoia rings, D-4, grown
in uplands 22
D. Hyper-sensitive or erratic yellow
pine rings, Pr. 62, grown near
lowest yellow pine levels, Arizona 22
Plate 4.
A. Fallen sequoia, Enterprise, in which
vertical uniformity tests were
made 26
Plate 4 — continued.
PAGE
B. Sequoia "California," Enterprise;
and Mr. C. A. Elster 26
Plate 5.
A. Plotting micrometer 38
B. Longitudinal plotter 38
C. White cyclograph 38
Plate 6.
A. Site of 500-year pines, Flagstaff,
Fl. 35, in foreground; looking
south 58
B. Stump of 640-year pine, Fisher's
Tank, Flagstaff 58
Plate 7.
A. Sequoia topography, ridges; area of
D-l, 2, 3, 4, 5, 18, 19, 28, 29
and 30 104
B. Sequoia topography, basins; area of
D-6, 7, 8, 9, 10, 11 and 27 104
Plate 8.
Spruce, S-14, from South Sweden, show-
ing sunspot cycle; wet climate
reaction. Dots give dates of sun-
spot maxima beginning with 1830 126
Plate 9.
Cyclograms 132
TEXT-FIGURES
PAGE
1. Heartwood rings at different heights in
the sequoia 25
2. Sapwood rings in fallen sequoia 26
3. Mean sensitivity and soil moisture .... 29
4. Arizona zone, smoothed group curves. . 70
5. Rocky Mountain zone, smoothed
group curves 78
6. Coast zone, smoothed group curves ... 84
7. Prescott rainfall and tree-growth 98
8. Flagstaff rainfall and tree-growth,
with comparison curves; tree-growth
shows close relation to winter pre-
cipitation 99
9. Cibecue drought record traced directly
from autoplot 100
10. Sequoia growth and rainfall 100
11. Land contours and annual growth of
sequoias in Redwood Basin 104
PAGE
12. Ring-size, sensitivity, and rainfall
correlations, Prescott 105
13. Pike's Peak area mean curve, PPM;
average of six groups, standardized
and smoothed 121
14. Sierra Nevada area mean curve, SNM ;
average of four groups, standardized
and smoothed 121
15. Cycles in western zones 124
16. Sequoia cycles 125
17. Flagstaff century curve, FLC, a.d.
1285-1700 ; standardized and smoothed 127
18. (1) Flagstaff area mean curve, FAM;
average of eight groups, standardized
and smoothed; (2) synthetic curve;
(3) residuals 128
19. Details of cyclogram patterns in
Plate 9 132
CLIMATIC CYCLES AND TREE-GROWTH
VOLUME II
A STUDY OF THE ANNUAL RINGS OF TREES IN
RELATION TO CLIMATE AND SOLAR ACTIVITY
By A. E. Douglass
Director of Steward Observatory, University of Arizona
With nine plates and nineteen text figures
CLIMATIC CYCLES AND TREE-GROWTH
VOLUME II
I. INTRODUCTION
In a dry region the dominating physical factor in tree-growth is
moisture. It is impossible for anyone to realize how vital it is
without actual residence — a mere trip through a desert is far from
sufficient, for it lacks the time element. One must live in it by night
and by day, in rainy and in dry season, in drought and in wet cycle.
One must see the burning sun, the sparse shrubs, the clear skies, the
striking colors of earth, rock, and sky, without the green of vegetation,
followed by the strong primitive atmospheric colors when the sun is
just below the horizon; he must see the round green cedars and the
ever watchful isolated pines of higher elevations; he must see green
valley bottoms and herds escaping from sight through deep range
grass at one time, and later on he must travel through cactus wastes
and dead cattle lying beside dried-up water-holes. And all this must
be lived with to afford full realization. The visitor from wet climates
does not sense it all for the first year or two, for day by day he
unconsciously expects a change, as has always happened in his pre-
vious experience. But after a year or more he is able to realize the
excessive value of moisture and even to recognize the evidence of
climatic changes.
This was the approach in the present study of climate and trees.
Many investigators have come to the study of growth variations
from other viewpoints. For example, a large number think of them
in terms of pests, for economic necessity has demanded their study,
especially in wet climates, where timber is abundant and they are
nature's agents for maintaining an equilibrium. It is true that the
relation of the abundance of animal life, even pests, to climatic con-
ditions is receiving more and more consideration, but the supreme
r61e of rain in a dry climate needs to be a matter of constant
experience in order to bring appreciation of the relation of tree-growth
to moisture in the Southwest.
AFFILIATIONS
At the outset this work was recognized as on the borderland
between astronomy, meteorology, and botany, and as needing help
and information from each with some expectation of ultimate return.
To some degree this return is realized in the present volume, which
gives for the astronomers some evidence of a real history of solar
3
4 CLIMATIC CYCLES AND TREE-GROWTH
changes for many centuries, for the meteorologists certain drought
conditions and climatic changes over a similar length of time, and
for the botanists an opportunity for learning how vegetation reacts
to certain phases of its environment. In addition, various problems
of dating, such as the chronology of the prehistoric ruins of the South-
west, have received a new approach, but solar and climatic cycles
with an ultimate view to seasonal prediction have continued the
central theme.
Prediction possibility has been one of the great incentives to recent
work upon tree-rings. There seem to be two approaches to long-range
forecasting. One is by direct tracing of the physical causes and the
other is by learning the history of past changes and working out
empirical methods. Each needs the other; so the climatic history
written in trees is doubly useful, for it may of itself give means of
foretelling the future, if such can be found, and, on the other hand,
if the physical causation is traced first, the derived line of causes
must agree with and explain this known history in trees. Thus pre-
diction will gain at once greater reliability. The last chapter in the
book deals with the various climatic cycles found in trees.
The effort to find a basis of seasonal prediction is the modern phase
of an age-old problem. In our day of newspapers, calendars, and clocks
it is hard to realize that at the beginning of prehistoric agriculture
farmers knew little of the time of day or the time of year except as
signs in the heavens told it to the rare man who had learned the
language of the sky. We are now in the same stage of ignorance
regarding yet longer cycles and hope to find our time in relation to
them so that we may know better when and what to produce each
season for modern needs.
DEVELOPMENT
With a conviction of the climatic value of tree-ring studies, one
can see two general lines of development, roughly described as exten-
sion in space about the world at the present time and extension in
time to past eras. The former has economic and scientific value,
because, in this way, climatic variations in different hemispheres,
continents, and latitudes may, within limits, be studied, in spite of
absence of formal instrumental records; so also the effects of mountain
ranges, continental contours, different orientation of exposure, and
the reaction of vegetation under different conditions. A beginning
is made in this volume along these lines. A set of yellow pine ring
records has been obtained from the Western States, and especially
the Southwest, by which a large area can be reviewed and a first
estimate made of effects such as those just mentioned.
Similar information regarding past climates is contained in fossil
trees. Without knowing exact dates, we can learn something about
INTRODUCTION O
the climatic and solar changes in various geologic periods, Tertiary,
Pleistocene, Prehistoric, and Protohistoric. The methods and instru-
ments developed in this research give us an improved approach to
various types of geologic material besides fossil woods. Chief among
these are the clay layers of de Geer and Antevs, dealing with the
retreat of the ice-sheet, the andesite laminations of Udden in Texas,
and the stalagmite deposits of Allison. This geologic material, with
much more that will come to light, will not be included in the present
volume, but will be reserved for future discussion.
One can see that in all this we are measuring the lapse of time by
means of a slow- geared clock within the trees. For this study the
name "dendro-chronology" has been suggested, or " tree-time." This
expression covers all the dating and historic problems referred to in
the following chapters, as well as the study of cyclic variations and
the distribution of climatic conditions.
COOPERATION
But with this development there is added need of information
from other sciences. The relationship of solar activity to weather
is a part of a rather specialized department of astronomical science
called astrophysics. There is help which one needs from that science,
but which one can not yet obtain; for example, the hourly variations
in the solar constant. One would like to know whether the relative
rate of rotation and the relative temperatures of different solar lati-
tudes vary in terms of the 11-year sunspot period. These questions
have to do with some of the theories proposed in attempting to explain
the sunspot periodicity. We do not know the cause of the 11-year
sunspot period. Here, then, is work for the astronomers. Climate
is a part of meteorology, and the data which we use are obtained
largely from the Weather Bureau. The observing stations are usually
located in cities, and therefore we can not get data from proper places
in the Sierra Nevada Mountains of California, where the giant sequoia
lives. Considering that this big tree gives us the longest uninterrupted
series of climatic effects whose dates are accurately known, which we
have so far obtained from any source, it must be greatly regretted
that we have no long modern records by which to interpret the writing
in those wonderful trees. So far as I am aware, only one attempt is
now being made to get complete records for the future.*
From the botanists and ecologists we need to know the exact
time of ring formation, the ability of the tree to conserve moisture
against the day of drought, the soil-moisture gradients at different
months, the different action of the tree in putting on a different color
of wood in the spring and autumn growth.
In dating problems, this study has developed another important
*CoJ. John R. White, in Sequoia National Park.
6 CLIMATIC CYCLES AND TREE-GROWTH
contact. The rings in the beams of ancient ruins tell a story of the
time of building, both as to its climate and the number of years
involved and the order of building, perhaps ultimately the date of
building. All this is anthropology, and much data from the archae-
ologists will help in identifying the rings in beams and supply valuable
climatic records of long-past times.
ACKNOWLEDGMENTS
The author's acknowledgments with thanks are most cordially
tendered to many sources of help. First of all, to the Carnegie Institu-
tion of Washington for bearing the expenses of publication and for
the yearly appropriations through its Division of Ecological Research,
to aid this study by securing suitable help and occasional field trips and
instruments ; and equally to the University of Arizona for so reducing the
author's teaching hours as to permit this investigation; to Mr. Clarence
G. White, of Redlands, California, for the White Research Fund,
which permitted the building of the periodograph in its latest and
most effective form; to Major L. F. Brady, whose interest in the
Flagstaff "buried trees," in prehistoric beams, and in the "burnt
trees" has brought in valuable material; to Dr. F. N. Guild, who
identified and described the white crystals found in buried trees and
named the mineral "fiagstaffite"; to Vilhjalmar Stefansson and the
Canadian Geological Survey for specimens from the American Arctic;
to Dr. W. P. Wilson and the Commercial Museum in Philadelphia for
access to the fine sections of Brazilian pines; to Mr. Percy J. Brown
and nephew, of Scotia, for their hospitality and cordial help in collect-
ing coast redwoods; to Mr. R. E. Burton for help with the Santa
Cruz redwoods; to Dr. E. S. Miller, of Flagstaff, Arizona, for help
with "buried trees "and in collecting the group called "Flagstaff
Northeast"; to the Whitesides, at Calaveras Grove, California, for
opportunity to compare the growth records there with those at the
southern sequoia groves; to Col. W. B. Greeley, of the U. S. Forest
Service, and Mr. Stephen Mathers and Mr. Arno Commerer, of the
National Park Service, for letters of permission to secure material
in such places; to the many officials of the U. S. Forest Service who
have helped me, especially Mr. G. A. Pearson, of Flagstaff, through
whose efforts the 640-year yellow pine was found and who has secured
many borings for me; to Mr. T. A. Riordan and Mr. M. J. Riordan
for the largest yellow pine section yet obtained in northern Arizona,
and many other kindly bits of assistance; to the National Geographic
Society and Mr. Neil M. Judd, director of its field work at Chaco
Canyon, and to Dr. J. A. Jeancon, of Denver, and Dr. A. V. Kidder,
of Andover, Massachusetts, also to Dr. Clark Wissler, of the American
Museum, and Mr. Earl H. Morris, for the trip to Aztec and entertain-
ment at Chaco Canyon and extensive contributions to the large
INTRODUCTION 7
collection of prehistoric beams; to the Toll Roads Company and to
Dr. W. S. Adams, of the Carnegie Institution, for permission to collect
samples on Mount Wilson; to Mr. E. W. Griffith, of Las Vegas,
Nevada, for a trip to the Charleston Mountains; to Mr. N. P. Wheeler,
jr., for the trip and collection of white pines near Endeavor, in north-
western Pennsylvania; to the forest supervisor at Klamath Falls,
Oregon, and Mr. Emanuel Fritz, for collections in Oregon and northern
California; to the directors and curators in the American Museum,
the Metropolitan Museum, and the Museum of the American Indian,
New York; Peabody Museum, Cambridge; National Museum, Wash-
ington; and the Field Museum, Chicago, for cooperation and help
in measuring specimens; and especially to Dr. John C. Merriam,
President, and Dr. F. E. Clements, ecologist, of the Carnegie Institu-
tion, for their continued help and interest in this line of investigation.
PREVIOUS WORK
The first publication by the author was in 1909, in the Monthly
Weather Review. This was followed by other articles until the whole
was summarized in 1919 in a volume with the same title as the present
one and published under the same auspices. At that time identifica-
tion and measurement had been made of about 75,000 rings in some
230 different trees from the States of Oregon, California, Arizona,
Colorado, and Vermont, as well as from England, Norway, Sweden,
Germany, and Bohemia (near Pilsen). That volume dealt with
studies upon the yellow pine about Flagstaff, Arizona, climatic con-
ditions there, the yearly identity of rings, cross-identification, time
of year of ring formation, number of trees necessary, the actual collec-
tion of yellow and Scotch pine and sequoia samples, methods of
curve production, correlation with rainfall and with solar activity,
and cycles and methods of determining them. The present book
opens with the development of technique in collecting and treating
specimens.
1
II. TREE SELECTION
Rings of trees have told many stories of the past. By their mere
enumeration the historian has built up our realization of great events
injhuman progress; by more careful counting the forester has dis-
covered the dates of ancient destructive fires; by changes in the rings
ecologists have determined historic changes in lakes and rivers and
settled questions of legal ownership. The present study of climate
and solar activity uses the accurate dating and width of rings over
wide geographical areas and into times long past for several purposes,
but chiefly to derive an understanding of that immensely complex
process by which climatic forces reach the earth and distribute them-
selves about it. This, it is hoped, will eventually lead to safe long-
range prediction of climatic conditions. In the present approach to
the subject, the recent development of technique is given first, and
this chapter deals with the selection of trees for climatic study.
SPECIES
Pines — The western yellow pine is perhaps the best tree for climatic
studies, on account of its precision and length of record and its wide
distribution. It is normally a dry-climate tree and does well in a
sandy soil, for its thick bark prevents evaporation from the trunk
and thus enables it to live when other trees could not survive. Thus
it endures relatively trying conditions and has little competing vegeta-
tion, so that the Arizona forest is said to be the largest "pure" stand
in the country. It can be injured by too much moisture in the soil,
and draining then improves it. Its age is very favorable, reaching
over 500 years. It is commonly free from burns and defects and its
rings are very readable. The immense area over which the yellow
pine grows adds to its value in this study, as its use avoids the com-
plexities arising from the use of different species. For all these reasons
it is considered the standard tree.
The Scotch pine of north Europe is very similar, but not usually
so large. However, this is because the European regions have been
cut over so much that very old trees are rare. The white pine in the
Appalachian Mountains cross-identifies very well. The pines in
eastern Massachusetts are less satisfactory, probably because the
region is too much cultivated. Very old hemlocks in the Green
Mountains of Vermont have rings extraordinarily like those of the
western yellow pine and almost as perfect in cross-identification.
White pines in the Yellowstone are good, and a few white or limber
pines near Flagstaff give records that are readable, but the locations
in which they grow are so rugged and variable that a complete test has
not been made of them. The foxtail pine at high altitudes sometimes
8
TREE SELECTION 9
reaches a great age, but its rings are more complacent than those of
the yellow pine. It reminds one of a cedar.
Sugar pine — Sugar pines are fine, large trees, but the rings are
large and the age is often disappointing. The distribution is much
more limited than the yellow pine; from which one assumes that it
will not stand so great a variation of moisture. Ring records of this
species on Mount Wilson resemble very closely similar records from
the adjacent yellow pines. Like the Douglas fir, it is a good occasional
substitute for the yellow pine, but is far from its equal as a standard
tree in southwestern climatic study. Substitute trees have given so
many cases of satisfactory records that one feels it always worth while
to use some other tree than the yellow pine where such standard trees
are scarce.
Douglas fir (spruce) — In the Arizona Mountains this tree borders
the pine belt on the upper, which is the colder and more rainy side.
It mixes with the yellow pine to a small degree and is the first choice
as substitute when the pines are infrequent in any site. The trees,
even if bigger, are apt to be younger, with larger growth each year.
The rings are usually well marked and free from errors and cross-
identify perfectly with neighboring yellow pines. It is somewhat apt
to exaggerate climatic influences.
Other spruces — The Sitka spruce of our northwest coast (tested
in Oregon and Washington) has heavy, emphatic rings of a complacent
sort and so far has not seemed a desirable tree. It grows to exceedingly
large size. A fine specimen some 9 feet through, in the American
Museum in New York, gives a good idea of what it is. This particular
specimen exhibits some very unusual spiral gross-rings whose origin
it would be interesting to determine. This spruce grows at low, well-
watered levels near the coast, and so its value as a climatic record is
probably low.
The Engelmann spruce of high altitudes is even less valuable in
this respect. It grows at elevations over 8,000 feet at Pike's Peak
and at 10,000 on the San Francisco Peaks (Arizona). Its rings have
very little variation and do not cross-identify with neighboring pines
and Douglas firs. Owing to these characteristics it has practically
no value as a climatic record.
The European spruce, Picea excelsa, is much better. While more
complacent than the very satisfactory Scotch pine there, it does show
good ring variations which can be dated and in one or two special
cases give a remarkable record of solar variations. Such is No. S 14
from southern Sweden, whose photograph is given here (see Plate 9)
because it did not come in time for insertion in the first volume. Its
curve of growth was given in Volume I, page 75, figure 22. It is
therefore unusual and interesting.
10 CLIMATIC CYCLES AND TREE-GROWTH
Sequoias — In this review of western trees the mountain sequoia
(Sequoia gigantea) easily takes a leading part in company with the
yellow pine, for besides its great age it has a fundamental feature of
greatest importance, namely, cross-identification over large areas.
In this character we recognize climatic influences. The ring-growth
in the big sequoia is not so sensitive as in the yellow pine, and perhaps
any individual tree is a little less certain to identify with its neighbors,
but yet cross-identification is very sure in that species and extends
through all the mountain sequoia groves from Calaveras on the north
to Springville on the south, 200 miles. The southern groves, which
yield the best results, give a record obviously similar to that of the
yellow pines in neighboring locations. It is true that the sequoia
needs a large moisture supply, probably more than it usually gets,
but its location is so high on the mountains that the winters com-
pletely interrupt the growth and therefore make the record in the
rings very reliable as to its annual character. The great age of this
tree gives it a second fundamental value. It is astonishing, for ex-
ample, to find over considerable areas similar identifiable rings near
1,000 b. c Further study upon the sequoia will improve our knowl-
edge of the normal growth-curve in relation to age, so that we can by
extrapolation tell with some precision what the climate was 3,000
years ago. This requires many corrections, such as that for flare of
the base, for slanting rings, and lor the indentations of the trunk which
come from root relationship. All these factors differ so much in indi-
vidual trees that it would seem profitable to study each tree specially,
and in recent collecting I have made notes about every stump and have
distributed the ages more carefully. (See Huntington, 1914.)
Coast redwood — The coast redwood (Sequoia semper •virens) has
been a disappointment, because after most careful tests it has failed
entirely to show cross-identification. This is undoubtedly due to its
climatic environment. Various attempts to make use of this tree are
described below (Chapter VI).
Junipers — The junipers and cedars are important in this review,
because in Arizona mountains they border the yellow pines on the
lower and therefore the warmer and drier side. As one ascends from
the desert to the forest areas, the first dark-green rounded trees are
the junipers of several different species. The growth of the juniper is
slow and the rings are often attractive, but for actual use disappointing.
One species branches at the ground and so seems impossible; another
has deep vertical indentations in the trunk, with erratic rings. The
growth can rarely be traced from lobe to lobe of a cross-section. Often
the rings condense so that identity is hopelessly lost.* The more
promising species is the pachyphlcea or alligator-bark juniper, which
* Some successful work has recently been done on the junipers.
TREE SELECTION 11
grows close to or in the pine belt. Its rings are apt to be complacent,
with considerable difference in mean size due to locality. From the
average rate of growth of junipers measured near Cibecue, 500 to 700
years would seem to be the usual maximum age of this tree.
This species has one idiosyncrasy which often rules out an attractive
tree. A vertical half may die and the other half live. This may happen
to the trunk and follow up some of the larger branches nearly to the
top of the tree. Close to Elden Spring at Flagstaff is a juniper of this
sort which is 4 feet through east and west and is still growing actively
in those directions, but north and south it is only a foot through and
completely dead. The alligator-bark juniper is more promising than
the other species and may become a valuable tree on more complete
investigation.
The cedars are somewhat like the last-mentioned juniper. They
are rather complacent, but do show some variations. The west
coast cedars take a good deal of water-supply. Some extremely large
ones are occasionally found, but they have not seemed promising.
The rings are generally larger than the sequoia rings and for the same
size the trees are not so old. Many cedars growing in the vicinity
of the sequoias have been examined and the ring record is considered
below the big tree record in quality.
Oak and other hardwoods — The oak is less generally distributed
in the Southwest than the yellow pine, but there are large and im-
portant areas over which it is the available tree. Various samples col-
lected seem very promising, but it has not been available extensively
in the form of stumps and it is too hard to bore, so no final tests can
be reported here. Kapteyn's first work in the Rhine Valley was on
oaks, and in the last few years (1921) Professor William J. Robbins,
of Columbia, Missouri, has traced a fine relationship between oaks and
spring rainfall. This tree was used in the Swiss lake dwellings, and
fossil oaks are very common, showing some of the best ring records
to be found in museum specimens. Undoubtedly it is a valuable tree.
Beech rings in northwestern Pennsylvania show good variations
and seem very promising. This is well to keep in mind, because there
are great beech forests in South America whose rings may contain
important climatic information.
Tropical hardwoods have been examined in museums in large
numbers. The annual rings are mostly very hard to make out and
naturally that is what we would expect where the trees have over-
abundant rain and sun. Yet there are pines from tropical areas
whose rings look very attractive and well worth a careful test for
climatic effects. They grow mostly at higher levels. Two Araucanian
pines from southern Brazil, showing 500 years of age, were measured
in the Commercial Museum at Philadelphia. Their variations looked
very attractive, but there was no success in finding cross-identity.
12 CLIMATIC CYCLES AND TREE-GROWTH
Cedar of Lebanon and archaeological material — This cedar is
chiefly found in mummy cases, which from the earlier dynasties show
beautiful ring systems, very pronounced but somewhat complacent.
The wood is not so good as yellow pine or sequoia, but as approximate
dates are known its records are valuable.
The prehistoric ruins of the Southwest have large numbers of pine
and fir logs used as beams. These offer the finest records and a very
valuable collection has been made. Even the charred ends of beams
that remain in some walls of burnt-out kivas give perfectly good ring
records which permit the "relative" dating of the construction period.
Juniper, cedar, and pinyon have been used in the same ruins and many
sections have been saved, but so far little relative dating has been done
on them. Engelmann spruce also occasionally is found, but it has failed
to be of value. Several cottonwoods give too short sequences to be
worth while. Certain buried pines from the vicinity of Flagstaff give
very fine ring records with other interesting features.
LOCATION OF TREE
Regions which have been recently cut over will offer the best
facilities in getting good specimens from the stumps. A full day or more
may well be spent in marking the stumps from which pieces will be cut
later by workmen. This selection is very important, for one wants a
group that will cross-identify and at the same time will fully represent
the forest and the general locality.
Homogeneous area — One needs, in the first place, to collect from
a homogeneous area, that is, an area in which the various trees have
somewhat similar conditions, enough to give similarity in rings, for
on this recognition of the same rings in each depends assurance of
climatic effects in the trees and reliability of dating of rings. To limit
one's self to a homogeneous area means that the group will not extend
to opposite sides of a large mountain. In northern Arizona differences
of a few hundred feet in altitude do not usually affect the rings, but
differences of 1,000 or 2,000 feet do sometimes affect them. Westerly
or southwesterly exposures are somewhat preferable, as that is the
direction from which the storms come and there can be no "shadow"
or other local effect.
Wide sampling — On the other hand, the group should not be con-
densed, but should extend a good portion of a mile at the least, so that
no alteration can arise from some special condition affecting a part of
the group.
Grouping — The tree bored, or the stump cut, is better if not near
other trees. Trees under 10 feet apart are apt to have an effect one upon
another by undue shading or appropriation of moisture. This causes
eccentric growth of the rings, throwing the major radius away from the
TREE SELECTION 13
center of the group. Such eccentricity is rarely harmful to the ring
sequence unless very conspicuous, but it may mean erratic or slanting
growth and therefore is to be avoided as a rule. While the Arizona
pines are naturally isolated, the sequoias are habitually close-grouped;
but in spite of this the latter tree rarely shows any effect that can be
attributed to nearness of other trees, unless two are almost in con-
tact. But in the coast redwoods close grouping is doubtless an
important cause of its failure to cross-identify.
The big tree is surrounded by dense vegetation in the basins and
loose vegetation on the ridges; the coast redwood has a jungle about
it; the yellow pines, however, wherever they grow, have sparse or
actually deficient vegetation about them.
Ridge and basin selection — This is a question of soil moisture and
underground drainage, most important factors in the life of the tree,
for while other influences may alter groups of rings and completely
spoil parts of the record, the moisture-supply in the soil may change
the character of the entire record or even make it totally useless. The
evident topographic features which control the situation are of course
hill and valley, but to make it more specific by naming the extremes,
it is called ridge and basin. Ridge and basin sequoias cross-identify
perfectly, but there is a great difference in their immediate response to
climatic changes, so that the ridge trees show much smaller average
growth with vastly greater differences from year to year. This goes
so far that the ridge trees nearly always omit many rings in the radius
one chooses to study. Only by accurate cross-identification can these
omitted rings be determined and correct dating carried past them.
In the yellow pines, ridge and basin contours have the same effect,
producing quick-growing, complacent trees in the latter and slow-
growing, sensitive trees in the former. With these facts in mind one
can usually pick the kind of tree desired.
Bedrock and soils — Lavas and clay soils give usually a small
complacent growth to the Arizona pines, while limestone and the
porous soil above it give more sensitive growth, which may be increased
in size by a richer soil.
Pines and altitude — The Arizona yellow pines at low levels, such as
5,000 feet, are so sensitive to rain that rings are frequently doubled
by the two rainy seasons. This characteristic nearly disappears in
1,000 and 2,000 feet of greater elevation, where the most usable
records are found. At still greater heights the accuracy of the rainfall
record diminishes, as soil and air moisture are more permanent and
the tree in its type of ring record becomes more like the California
yellow pine and sequoia.
East and west mountain slope — In the southwestern part of the
United States, the winter storms coming from the west supply nearly
14 CLIMATIC CYCLES AND TREE-GROWTH
all of the growth-moisture for the trees. The result is that the east
and west sides of a large mountain have a distinct difference in climate
which shows in the trees (see shadow effect, p. 108). At corresponding
levels the west side is wet and the east side is dry. Around the San
Francisco Peaks, in northern Arizona, the pines extend to 1,000 or
1,500 feet lower elevation on the west than on the east. Pines on
westerly slopes are to be preferred as less likely to be altered by local
conditions.
North and south mountain slope — Snow lingers longer on north
slopes, and pine trees are able to live under such conditions at lower
altitudes. But in the middle elevations of the pine belt no sensible
difference has been noted in ring record between minor north and south
slopes.
CONDITION OF TREE
Lightning scars — In standing timber this commonly appears as a
white streak from top to bottom of the tree, about 1 inch in width
where the bark has been blown away and the wood revealed. The heat
of the electric flash has suddenly vaporized the sap and exploded the
tree along this narrow line. This usually heals and has no important
effect on the climatic record in the tree. The scar is easily recognized
on the stump. It is very common in the "buried trees" found in the
valley terrace above Flagstaff, which doubtless means that summer
thunderstorms were more common in that particular past climate
than they are now. Lightning scars are rarely seen in petrified wood,
but the writer has a photograph of one in a beautiful specimen from
Tertiary levels in Yellowstone Park.
Injured and fire-scarred trees — The major injury to western trees
is from fire. This is not always caused by the careless camper or
«moker, for the greater number of forest fires come from lightning.
A single summer storm at Flagstaff has been seen to start fires in four
different trees. In a precipitous country it is the up-hill side of the
tree which is more likely to have fire injury, for it is the brush and
leaves and needles collected there which hold the fire till it injures the
tree. The fire scar is a large burnt area covering from 10° to 150° of
the circumference and extending from 3 to 20 feet or more above
ground. The tree may recover by covering a small area with new
growth or by abandoning all attempts to reclothe the burnt section
and using only the root system on the normal side.
Different trees and fire — Fire injuries rarely give trouble in the
yellow pine, for they are largely on nearly level ground and there is
little vegetation about them. Hence, there is little accumulation of
rubbish and a general fire does not finger about an individual tree.
The sequoias represent an enormously greater interval of time and so
.are more likely to show fire scars. Their ages are from 700 to 3,000
Carnegie Inst, of Wash. Pub. 289, Vol. II (Douglass)
fU
wtmm x
A. Fire injury on D-12 (stump) showing repair and gross rings and
inclosed bark
B. Center of oldest Sequoia, D-21, showing ring grown in 1305 b.c. ; three
pins stand at 1300 b.c.
TREE SELECTION 15
years, compared with 200 to 500 for the pines. The sequoias also
grow close together, and in the basins are closely surrounded by other
vegetation. So fire once in them lingers and injures the tree. Amongst
thousands examined the uninjured trunk has been very rare, perhaps
less than 1 in 10, as one looks on top of the stump and sees the history
of each tree. The large groves of coast redwood show similar history.
Though the custom of burning over the area right after cutting may
lead to overestimation of the number of ancient fires, the impression
is gained from hundreds of stumps that large fire injury is very nearly
as common as in the giant sequoia.
In tree selection the effect of a lightning scar is negligible. The
effect of a fire which kills small trees about but does not externally
injure the tree under examination is to cause a slight possible diminu-
tion in size of rings. In this connection one remembers that fires are
more frequent in times of drought and hence exaggerate climatic
effects already in the trees. But the effort of a tree to repair a large
burnt area changes the ring-size for some distance from the injury and
sometimes all about the tree. Hence trees showing large fire injury should
not be used.
COLLECTION PURPOSES
In securing records of climate in trees, necessarily length and
accuracy of record are the two primary considerations. In the previous
pages we have dealt with accuracy alone; now we deal with length,
always modified by the necessity of preserving accuracy also.
Cycles and secular changes — The original thought in this study
emphasized the tracing of cycles. These are found in relative ring-
sizes which can be taken almost at once from the trees without a
knowledge of the absolute rain or climatic equivalent. Perfect dating
was absolutely necessary and all specimens have received the most
careful laboratory handling. It was found by early tests that no especial
gain was made by using large numbers of trees (Vol. I, pp. 21-22).
But when Huntington studied the big tree for absolute values and
secular changes, he did his work on the stump and obtained material
which served his purpose without accurate dating. He used many
specimens of all ages in order to work out a compensation for age, for
that was fundamental.
Best collection methods — To allow for the needs of each of these
purposes the best collection includes, first, long records; second, a few
younger trees for the sake of certainty in dating the older trees if
recent rings are compressed and doubtful and in order to develop a
compensation formula for age of tree; and third, borings in the outer
parts of living trees in order to get present-day climatic comparisons
and to be perfectly sure of the ring of the current year, which sometimes
fails to show on the stump.
16 CLIMATIC CYCLES AND TREE-GROWTH
Long-record trees — (1) Pines. If very large living pines are in
moist valley-bottoms, they are not likely to be of maximum age,
that is, over five centuries; but if they are near 60 inches in diameter
and growing on a ridge or hillside, especially above a dry valley, they
are likely to contain a valuable record. Of course, in such cases one
checks the estimate by a core from the increment borer. (2) Sequoias.
The oldest sequoias are not close to running water nor yet on exposed
ridges, where stress of storms does not permit great age, but they are
somewhat between these situations and usually near, though not at, the
higher levels of the grove. This description applies well to the 3,200-
year tree at Converse Hoist and the 3,100- and 3,000-year trees at
Enterprise. A 2,800-year tree at Converse Hoist was nearer the top
of a low ridge than one would have expected. A number of 2,200-year
trees were well outside and yet not far from the thickly covered swampy
basins, and they extended up the valleys to the highest levels of the
groves. In the lower levels the trees were apt to have a large supply
of ground water and some very large trees had only 1,500 to 2,000
years of age, such as the "Big stump" at Wigger's (General Grant
Park) and the Dance Hall stump at Calaveras Grove.
Collection for age compensation — Samples for this purpose must
obviously be taken from the immediate vicinity of the old trees whose
records are to be checked, and in the same topography.
Climatic comparison — In collection for climatic comparison, one
uses the general principles of selection already enumerated, remember-
ing that one gets little if anything from young trees. Mature trees
are much preferred, and even the largest and oldest, for in such cases
the 9 or 10 inches of core cover a great number of years. On the
other hand, very slow growing trees from the tops of dry ridges may
be impossible to date without some neighboring younger trees, and
it is safe nearly always to include a very few younger trees to assist in
this operation. Trees very near a road are apt to be erratic from injury.
Age estimates in sequoias — Age estimates are a necessary part
of collecting, especially in sequoias. The best criterion is the size of
the outer rings, coupled with the total diameter of the tree. A promis-
ing tree should be over 20 feet in diameter above the bulging base,
or near 25 feet at the very maximum. The rings at various places in
the outer parts should get down to a few tenths of a millimeter or
about a hundredth of an inch. On most of the very old trees there is
a burnt space in which a few chips or bits of charcoal will give a sample
of the rings. An increment borer is still better and may be used through
a thin place on the bark of a living unburnt tree. The largest tree,
showing over 30 feet in maximum or bulge diameter, if near running
water, is not likely to add much to our climatic record. But if such a
tree is on a dry hillside its age is worth investigating, and if it still
promises well, some apparatus for boring it to the center could be devised.
III. RADIALS
SELECTION
An essential part of this study of climate and trees has been the
laboratory work on the rings, by which the actual wood from the tree
is placed under microscope and measuring-machine. In this way
specimens from different trees may be compared together and an
accuracy reached which would be hopeless in work on the stump.
By laboratory means, cross-identification and correct dating are
obtained before measuring and the measuring can be done to any
desired accuracy which the rings permit. Hence it is essential to secure
ring specimens which represent the tree, to get them to the laboratory
without injury, and then preserve them in such a way that they can
be used over again or referred to subsequently for any desired purpose.
Definitions — It is obvious that such ring specimens must be cut
across the rings in order to display the proper sequence. The ideal
form, therefore, is a radius of the tree, carrying an unbroken series
of rings over all parts of the tree's history which are worth while.
Such pieces are here referred to as tree-samples, ring records, radial
pieces, or simply radials. Of course, they may take different forms,
depending on various conditions of collection; for example, whether
they come from living trees, fallen trees, or stumps.
LIVING TREES
The main point in sampling living trees is to get a short radial
sequence of rings without injury to the tree. The best instrument for
this is the Swedish increment borer, which will be more fully described
in a subsequent chapter on instruments. These borers will not go
into hard woods nor even into junipers, but they work well in pines.
Direction of boring — If the tree is on a steep hillside, it is usually
more convenient and customary to bore on the up-hill side. Theo-
retically there could be a difference in the rings between the up-hill
and down-hill side of a tree, but no such difference has been noticed.
Other things equal, it is well to eliminate the possibility by being
consistent throughout a group. If the ground is generally free from
steep inclination, one should adopt a certain compass direction and
use that consistently in the group. Early investigation showed about
Flagstaff a slight average increase of growth on the north or northeast
side of a tree, due to lingering of snow in the shade of the tree, but this
is probably of little or no importance in radial selection.
Height above ground — Height from the ground, if well below the
branches, has not been found to introduce error. So far as observed,
17
18 CLIMATIC CYCLES AND TREE-GROWTH
the differences at different heights are less than the differences between
different trees. Of course, in most cases the differences are practically
none at all. This subject of taper study or vertical uniformity will be
treated on a later page. A boring within a foot of the ground makes
one feel that complex and difficult corrections are needed because of the
root influence, and the ring record therefore is inferior. On the other
hand, if the boring-hole is made over 2 feet from the ground, it
may injure slightly the value of the tree for lumber. The average
height of pine stumps about Flagstaff is 16 to 20 inches, sometimes
going to 2 feet. The lumberman knows that interior defects increase
toward the root, and there is always a little waste at the lower end of
the butt log. In choosing the exact spot to bore it is better to try a
slightly projecting part of the trunk, for there is less danger of encoun-
tering absent rings which might render dating difficult. One must be
careful in boring fallen trees to note whether they still have roots in
the ground and are dry or moist. If they are still rooted or not thor-
oughly dried, the sapwood may be distorted with irregular growth or
irregular swelling from moisture.
Root rings — Ring sequences have been identified from roots of
trees and in some cases such records seem usable. These, however,
have never been included in the averages, from the feeling that root
rings, even in large branches of the root, must be subject to other
conditions than the trunk and may not be consistent. Sometimes,
in well-watered pines, early rings in the lower trunk near the root may
be very large.*
Crown rings — Rings near the top of the tree and in larger branches
show close similarity to rings in the lower trunk. Though their
actual size is smaller and sometimes microscopic, the sequence of sizes,
of the tree record, is nearly the same (see fig. 1, p. 24).
Boring the sequoia — Using the increment borer on the sequoia
has rarely seemed worth while, except for some special purpose, such
as tests on young trees for infancy rings, estimates of age, and so
forth. The reason is the enormous thickness of bark of the sequoia,
especially in the lower 15 feet, and the distortion of rings due to bulges
in the same region. With a ladder one could get useful specimens.
The i-inch tubular borer — The tubular borer so far has not been
satisfactory on living trees, not because it hurts the tree but because
it is slow and difficult in operation. An 18-inch core from a 350-year
*This was observed in a tree which once stood in the flat south of the county hospital at
Flagstaff, about 2 miles north of town. The tree was cut down in the 1880 's and was renowned for
its size. Recently Mr. L. F. Brady copied on paper the rings in the stump, which was badly
burned. When I saw it, the stump had been blasted out and thrown away, but fragments showed
extremely large and complacent rings near the root. The dating was uncertain, but it was prob-
ably nearly 500 years old at time of cutting.
RADIALS 19
tree in the lava-bed near Flagstaff took nearly two hours of very hard
work. When it is needed, no doubt a suitable borer will be easy to
construct.
FALLEN TREES
The chief work on fallen trees was done in the Calaveras Grove of
sequoias. The bark of these trees lasts 10 years or so after the tree
has fallen. The sap wood weathers off in something over half a cen-
tury. Heartwood has lasted a hundred years in the open air, but in
the case examined the wood was badly decayed and little of it was
left, as shown in Plate 2. It has been a disappointment not to find
logs lasting far longer, for example, a thousand years; for if very
large ones could be found they might have very old ring records.
Apparently even the wonderful qualities of the sequoia sap will not
preserve the wood indefinitely. Fallen trees give the chance of boring
at any height and from that arose the vertical uniformity or "taper"
tests given below.
In the Calaveras Grove there were three classes of fallen trees,
so far as dated records were concerned: (1) old tree- trunks without
sapwood, so that the date was unknown; (2) trees showing sap wood,
with approximate date of falling; and (3) those whose date of recent
f ailing was known. So to insure correct dating, all three were included.
Thus an overlapping group was obtained, which by cross-identification
produced correct dating for the Calaveras trees. But all this care
proved unnecessary, for the first radial examined, as well as all the
rest, readily dated in terms of the trees in the southern groves.
STUMPS
Collection from stumps permits many forms of which the full
section is only possible in the case of small trees. Thus full sections
have come from the white pines of the American Arctic and from the
beams of the ancient ruins. At the start, full sections were made of
the early Arizona yellow pines, but they have proved so unwieldy
and difficult to provide space for that even from these radial samples
have been cut, which give the ring sequence from center to outside.
So methods of collection necessarily adapt themselves to the size of
the trees. In the vast majority of cases a piece is cut from the stump,
and that process is described below.
Shape of stump — In felling a tree a notch is first cut on the side
toward which the tree leans and will fall. This undercut goes perhaps
one-fourth way through. In big trees it becomes large enough for
men to stand up in. Then a two-man saw is started in horizontally
from the opposite side at a slightly higher level. As the saw enters the
tree, the weight of the tree will pull away from it and not make it
bind. Sometimes the tree is leaning so heavily that as the saw gets
20 CLIMATIC CYCLES AND TREE-GROWTH
deep into the trunk, the strain on the remaining wood is tremendous
and it cracks badly in lines parallel to the saw. If its own weight does
not keep it from binding the saw, steel wedges are driven in the cut
to force the tree up on that side. The tree usually begins to fall
some time before it is completely cut from the stump, the portion that
is uncut breaking off at the level of the undercut. The stump then
shows the sawed surface for two-thirds of the diameter on one side,
the chopped surface of the undercut a foot or two lower on the other
side (in the big trees), and between these a broken and splintered
space where the wood broke in falling. Sometimes the tree does not
fall of itself when the saw is approaching the undercut, and then
instead of sawing it completely in two, which would be dangerous,
sticks of dynamite are placed in the remaining attached portion and
the tree blown loose. This is apt to blow the stump to pieces, as
happened with D-18 of the early sequoia group. That sample was
therefore cut from the end of a log which had been 50 feet or so above
the ground. So nearly all stumps have a flat top, which will exhibit
from a little over one-half the diameter to more than three-quarters.
This restricts the choice of radius a little, but reduces the amount of
sawing in making the cuts for the radial piece.
Selection of radius — In visiting a cut-over area with multitudes
of stumps, the first consideration is the apparent excellence of the
rings and the ease of cutting a radius which contains good readable
ones. In the Arizona pines this gives very little trouble. In these
trees the radius chosen and marked merely fulfills consistency regard-
ing points of the compass and contour of ground, and avoids fire-scars,
lobes, and knots in the stump-top itself. The piece cut out very often
takes the whole diameter. In the sequoias perhaps only 10 per cent are
without defects, and the inspection of stump-tops becomes an impor-
tant matter requiring from half a day to a couple of days. Deep fire
wounds in healing often inclose large masses of bark, and frequently
such scars have a considerable area of sapwood which has never
turned to heartwood. Such defects are always interesting for the
history they tell and are easily avoided in picking a radius. This
appears in the photograph of sequoia D-12 in Plate 1.
One of the greatest difficulties with small fire-scars is the extensive
break they sometimes cause in the continuity of the rings. The fire
so alters the growing layer that for some distance away from the burnt
area the wood will crack and it may be very hard to say whether the
crack is within one annual ring or between two. Lumbermen say
that this cracking or checking takes place in the living tree. It is
attributed sometimes to temperature changes — frosts in the weakened
wood — and sometimes to wind. At any rate, in a weathered stump
such a crack becomes worse and makes it difficult to use otherwise
good material. In such cases it is always best to cut a separate small
Carnegie Inst, of Wash. Pub. 289, Vol. II (Douglass)
to
A. Weathering in 60 years, CV-4; bark gone, sapwood mostly gone;
Calaveras Grove
B. Weathering in 125 years; CV-3, sapwood and center entirely gone;
Calaveras Grove
RADIALS 21
radial piece extending a hundred years or more on each side of the
questionable years, from some other perfect part of the stump. This
new piece bridges over the doubtful point. It is just such procedure
as this which makes the dating entirely reliable. Knots or buried
branches give practically no trouble, except at the very center. The
lower parts of a sequoia whose bark has turned to the notable tan
color of youth seem to have no branches. They probably all disappear
as the rings lose that immense size called the "infancy" stage. So in
selecting a radius for cutting it is highly important to escape gross-
rings, lobes, and fire-scars. Items to be recorded are the length of
radius, bulges or slope, direction and amount of slope of the ground,
and neighbors. If the tree has grown eccentrically one would slightly
prefer an average radius if the rings are not too much inclined. Bulges
as a rule are below the level of cutting, but they may affect the slope
or vertical inclination of the rings from the enlargement they produce
in the base of the tree. In recent collections the slope of the outside
has been measured with a simple inclinometer.
The v-cut — Even in small trees the v-cut illustrated in Plate 3
is now the standard form found practicable. Such small pieces are
v-shaped or triangular in cross-section and made by two slanting
cuts with a saw, meeting at a depth of 1 to 6 inches below the surface.
With a long saw on large stumps the slanting cut is made by driving
two spikes at a slant into the stump top, placing a board against the
spikes, and resting the saw against the board.
The size and weight of the radial piece cut out depends on the
spacing of these cuts. Two inches is taken as the standard practical
width and depth in big trees. If the v-cut is made from a weathered
stump, as is usually the case, the cracks in it allow it to drop to pieces
as the saw releases it. To aid in fitting these together the distance from
the bark in inches is marked on each piece as it comes loose. These
pieces are collected by an assistant who accompanies the sawyers and
are all put in one bag, which is marked with the radial or tree num-
ber. These small bags are finally collected in a large canvas bag for
transportation.*
PREPARING THE RADIAL
Arrived at the laboratory, the pieces are taken from the sacks
and carefully fitted and glued together and wired or screwed to a
right-angle mount of standard size which permits stacking. This
mounting consists of a base and back, each 4 inches wide by 8 feet
long, 1-inch wood, with heavy square end-pieces. These mounts,
being all of the same size, will stack one on top of another against a
♦When this work is done by a lumberman who can not bother with bags, the spacing of the
cuts should be wide enough to make the specimen hold together.
22 CLIMATIC CYCLES AND TREE-GROWTH
wall or with very slight bracing, so that at a glance one may look over
the entire collection.
The original surface of the stump is placed downward in the mount-
ing, thus showing the freshly cut surfaces, which at a little distance
below the stump-top are in better condition. One or both of these
surfaces is smoothed with a rasp or file; then after careful inspection
of the rings a line or band is marked where the measuring and dating
will be done. For this purpose two parallel lines a half inch or more
apart are put on, as nearly straight as possible. The space between
these lines is then shaved with a sharp razor. This leaves a superb
surface for measuring the rings. The lighting direction is important,
but by a little practice the best position is readily found. The only
special caution at this stage is that each break in the wood which
has been glued should be marked and shaved along the crack so that
dating and measuring can be carried past it without the slightest
chance of error, but this rarely presents any difficulty.
RADIAL STUDIES
CIRCUIT UNIFORMITY
By circuit uniformity is meant the close similarity of the ring
records in all directions from the center of the tree. The funda-
mental importance of this was fully recognized in the first formative
period of this investigation. Cross-identification between different
trees was first used as an essential in 1911, but this identity between
different radii in the same tree was noticed in the very first trees
measured in 1904. To describe where it has been found would be to
enumerate almost every tree worked upon. Even groups that do not
cross-identify well show circuit uniformity. This does not mean that
the different radii are equal, but that the relative ring values are
closely the same in all directions. So the present topic is for the pur-
pose of calling attention to a few exceptions. Circuit uniformity
is modified in three ways — by eccentricity, lobes, and gross-rings.
Eccentricity — Slight eccentricity is very common. It becomes
noticeable in perhaps one-third of the stumps examined and occurs in
perhaps one-quarter to one-twentieth of the trees sampled. It merely
means more growth on some one side than on the opposite. It is a
common effect of group pressure and frequently occurs when two
trees grow very close together. The maximum growth is then away
from each other. It may be due to other causes. In the first 25
Flagstaff yellow pines there was 12 per cent more growth to the north-
east than in the opposite quadrant, attributed to better moisture con-
servation in the shade of the tree. Eccentricity, unless excessive, need
have no effect whatever on the tree record, and even if excessive it can
usually be evaded. The most extraordinary case ever noted was a
Carnegie Inst, of Wash. Pub. 289, Vol. II (Douglass)
i V5u
A. Forms of v-cut on stumps
B. Complacent sequoia rings, D-8, grown in wet basin
C. Sensitive sequoia rings, D-4, grown in uplands
& §«r f '*? f?f Iff !P»«J
__j£4? - •*» "* *
*,v ? •■ ' ■P2h-&m£& : ■-■■
D. Hyper-sensitive or erratic yellow pine rings, Pr. 62, grown near lowest
yellow pine levels, Arizona
RADIALS 23
Scotch pine from Os, Norway, which had a 3-inch radius on one side
and a 9-inch radius on the other. The maximum radius was used and
it cross-identified in a perfectly satisfactory manner. Several of the
trees from that locality showed a very rare characteristic in having
the eccentricity change its direction as the tree grew older, due prob-
ably to change in surrounding growth. This was less easily avoided.
Forest Service men usually prefer a mean radius in eccentricities, but
in this work it is not desirable, because in that kind of a radial the
rings are apt to be inclined, making perpendicular measurement more
difficult.
Missing rings — In eccentricity the crowding in the shorter radius
causes some rings to disappear altogether instead of merely becoming
more minute. The same failure of rings is very apt to occur between
lobes, especially in junipers. Hence in boring trees it is safer to choose
the lobe itself than the depression between lobes.
Lobes — In the case of lobes, or the scalloped outline of a tree-trunk,
the variations observed in eccentricity are greatly exaggerated, in
fact, so much so that trees like juniper and pinyon that go strongly
to lobes can not well be used in ring studies. In an extreme, a given
ring can not be traced from lobe to lobe. Such a tree of course has
doubtful value.
Pines and sequoias, however, have only a negligible lobe effect,
except during the "infancy" period of the sequoias, when the lobes
are very marked. They disappear in the early "youth" rings, which
are really the earliest ones of any chronological value. When not
pronounced, either the lobe itself or the depression between two lobes
may be taken as the location of a radial, for the rings remain at right
angles to its direction.
Root influence — Lobes are usually more pronounced at the base
of the trunk and show evident connection with the roots. Since the
root supplies the sap which passes up the trunk and, in passing, forms
the ring, the rings, it would seem, depend upon the way the sap spreads
out around the tree as well as upon vertical movement. So in old
trees whose rings are naturally crowded, we find some missing here
and there in the circuit without much lobe effect being evident. In
the general use of at least five trees in a group, such lapses practically
always come to light.
Gross-rings — A difficulty in the selection of radius in sequoias
has been occasional radii where the rings are greatly enlarged. These
are called "gross-rings." They are probably associated with the
success of some certain root and therefore formed lobes or projecting
curves about the trunk when the tree was growing at that size. Some-
times these areas extend directly to a projecting curve of the stump
outline and their relationship is evident. They not merely exaggerate
3
24 CLIMATIC CYCLES AND TREE-GROWTH
immensely the average growth in certain parts of a radial line, but
they do not hold to one radial direction and any straight line; cutting
them at an angle has inclined rings, which therefore have an added
fictitious size.
Gross-rings only moderately represent climatic change. In an
old study it was found that gross-rings in one tree corresponded to
similar rings at that date in about half the other trees. They probably
occur when for some reason the tree is having rather successful growth,
and so they roughly indicate favorable conditions. It would probably
improve the curve of the tree's growth if they were reduced to a size
somewhat less than half-way between normal and their actual size.
The inclination which they so often exhibit can be corrected by meas-
uring in a different angle or by a multiplying factor. But either one
adds greatly to the labor of handling large quantities of data in tables.
Spiral gross-rings — A prehistoric section, H-9, from the Aztec
ruins has a spiral of enlarged rings, which took about 12 years to make
the circuit. It is impossible to tell from the specimen which way the
enlargement rotated. The 9-foot Sitka spruce in the American
Museum of Natural History shows at some 8 or 10 places about the
circuit spiral enlargements with a very slow rotation.
VERTICAL UNIFORMITY
Outside tests — The close resemblance between ring records at
different heights in the same tree was assured for the yellow pine a
score of years ago, but has only recently been tested formally for the
sequoia. During the trip of 1925, a windfall in the Springville region
offered such a good opportunity for tests of this sort that it seemed
worth while to take advantage of it. This tree, whose uniform trunk
was about 15 feet in diameter, had been blown down in 1901, according
to Mr. Elster, close to the houses at Enterprise, which had been started
as a mill-site some three years before. The tree is lying there in excel-
lent condition. The Swedish increment borer was used at 9, 15,
and 35 feet from the base of the roots and thereafter at each 20 feet,
to a distance of 235 feet from the base. At 255 feet small pieces were
cut with a saw, in wood which had been a living branch and in a dead
part which had been the main stem. This last showed nearly a
thousand years in the radial and has not yet been identified, probably
on account of the smallness of the rings. Yet 900 years in the living
branch were readily dated, and at 20 feet below this point the cross-
identification is perfect, though the branches begin nearly a hundred
feet lower down. The lowest boring was well within the root system,
close to ground-level, and does not identify well after 1700. With
this exception, similarity in heartwood record, which extends to about
1800, is striking at all heights above the ground. But the sapwood
rings show profound differences, due it is thought (p. 101) to irregular
RADIALS
25
swelling from the moisture which has filled them for years. Figure 1
shows parts of the heartwood curves, from 1550 to 1590, including
the year 1580, which is very distinctive when taken together with
1548 and others. Figure 2 shows the variable sizes of sapwood rings,
interfering greatly with dating and presenting a most unusual con-
dition in the sequoia.
The curious fact became evident that the tree grew in places a
long time after falling, for most of the borings show a serious injury
about 1901 and some show no growth after that. But some show
continued growth up to 1915. This appears in figure 2. Evidently
roots still in the ground supplied moisture and supported growth for
more than a dozen years after the tree had fallen.
115
95
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YEARS
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Fig. 1 — Heartwood rings at different heights in the sequoia; total height 265 feet; vertical
uniformity nearly perfect. Scale X 7.5; horizontal line with each curve represents 1 mm.
growth
Naturally, this matter of longitudinal or vertical uniformity was
considered and tried out informally in the early work on this subject,
and, so far as the eye could tell, the same rings existed at different
heights. The fact that cross-identification applied equally at different
heights in the trunk of the tree was held sufficient at the time. For
example, D-18 and D-20 were each cut about 50 feet above ground-
level, and yet they cross-identify and otherwise appear exactly as
sections near the ground. The recent work of MacDougal and Shreve
on the longitudinally bisected tree is adding to our knowledge, and it
26
CLIMATIC CYCLES AND TREE-GROWTH
is desirable to see such studies applied to mature big trees and to
yellow pines, each in its natural home.
Central tests — A recent test at the center of a sequoia came about
in this way. Stump numbered D-22, whose picture is shown in
Volume I, Plate 7, A, was sampled in 1918. It had over 3,000 rings,
but other innermost ones were missing on account of a large hole in the
center. The earliest ring found was 1087 b. c. The estimated radial
loss in wood at the center was 12 cm. (some 5 inches) or about 75
rings (Volume I, p. 52, table 5). The "butt" log from this stump was
lying not far away. In 1925, it appeared that in the upper end of this
115
95
75
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1850 60 70 80 90 1900 10 20 1850 60 70 80 90 1900 10 20
YEARS
Fig. 2 — Sapwood rings in fallen sequoia; irregular growth after falling (in 1901) is shown with
distortion due to water-soaked condition. Scale X 7.5; horizontal line with each curve
represents 1 mm. growth
log there was no hole and the rings originally filling the hole in the
stump might be found and measured at this point. So a special cut
was made crossing the center and extending a few hundred years
along the best radius. This direction proved to be away from the
original radius, but in the sequoias that practically never makes any
difference. This cut was 12 feet above the original cut. It was hoped
that the new piece would carry a record even beyond D-21, the oldest
of all the sequoias. But this wish was not fulfilled, although this
center v-cut proved very interesting. It cross-identified with perfect
ease and entire certainty. The central growth was in 1115 B.C. So
only 30 years were gained, but it thus carried a record back very nearly
as far as D-23 nearby, whose innermost complete ring was 1122 b. c.
Carnegie Inst, of Wash. Pub. 289, Vol. II (Douglass)
**
A. Fallen sequoia, Enterprise, on which vertical uniformity tests
were made
B. Sequoia "California," Enterprise; and Mr. C. A. Elster
RADIALS 27
At the same visit in 1925, it was remembered that D-23, whose
earliest ring has just been given, also had a large hole in the center,
with an estimated loss of 14 cm. or 80 years. This D-23 or Centennial
stump, has a large fragment lying near it on the ground, but a search
showed that only some outside pieces were there and the central
parts were entirely missing. Thus, there is no chance of extending
the record of D-23. In this connection it may be added that the
oldest tree, D-21, whose earliest complete ring is 1305 b. c, has only
an inch missing at the center, perhaps a half-dozen years, and so there
is no chance of material extension of that record. The central part of
that stump is carefully preserved and mounted in the laboratory.* It is
shown in Plate 1.
A tree known at Springville as "California" and numbered D-47
in my series was cut years ago for the purpose of building a sequoia
hut. It stood isolated, about half a mile from the Centennial stump
in a southerly direction. The stump has a very high, projecting
center, with steep ax-cut slope to north and a walk-way all around
where slabs of wood were removed. The top and nearly all the trunk
He off to the east, with a smooth sawed face 15 feet in diameter, as
shown in Plate 4. My v-cut was made on this face, extending past
the center. Almost at the last moment of my visit one of Hunting-
ton 's grooves (but no number) was found on this stump, showing that
he had counted the rings. So for comparison we made a short central
v-cut. This was about 12 feet above the ground and also about
12 feet below the full radial taken from the log. This will be studied
in connection with ancient records.
♦The smallness of this hole where the infancy rings used to be, suggests that this cutting-
level was 20 or 30 feet high on the tree when it was a sapling. If so, the ground about this tree
has filled rather than eroded. The adjacent contours make this possible.
IV. RINGS
During and following the processes of cross-identification and
dating, described in the previous volume, the best ring records are
picked out by a form of selection, first between the different trees of
the group, and second between different parts of each tree record.
SELECTION IN GROUP
During cross-identification it is very easy to see which specimens
conform best to the group type and which ones conform so little as to
be discordant, for in all the groups used a group type is evident. It
becomes, then, easy to recognize any specimen which for some reason
or other, perhaps a fire injury or a different water-supply, does not
agree with its group. Such specimens are obviously so far from the
average that probable errors are diminished by their omission and
their values are not included in the group average. Such individuals
are usually very few in number, in the majority of groups none at all,
and they include of course the ones which can not be cross-identified.
MEAN CONFORMITY
In judging whether any tree should be retained in the group a
criterion called "mean conformity" has been very extensively used.
It is the agreement which any individual shows to its group or type.
In effect, it is an added weight given to individual specimens which
have the best support from other members of the group.
Quantitative conformity — An actual numerical value of this con-
formity could be derived by mathematics (by mean residuals from
group averages), but it would be a long process and the results at the
present stage would not be worth the labor; for after familiarity is
reached a conformity coefficient can be estimated, as in a multitude
of different scientific observations. However, in connection with the
selection of best sequoia records for comparison with Arizona pines,
a quantitative value was reached in a practical way. The Arizona
variations were kept fresh in mind as each sequoia record was reviewed.
The number of Arizona features found in each sequoia for each of the
last five centuries was carefully recorded and the total placed against
each sequoia as its weight or conformity. Those having the best con-
formity were then selected for certain comparison problems. This is a
good practical method. Other selections have not been made on so
large a scale and did not need such formal organization, but nearly all
have been based on some modification of this process.
Weighted means — After mean conformity of each member of a
group has been obtained, it may be used simply to exclude poor
28
RINGS
29
records, so that the average of the remainder will be improved. If
some approach is made to a numerical value of this conformity, then
it may be used to obtain a weighted mean. This was done in the case
of the four best sequoias selected for dating comparisons with Arizona.
This was a long process, but its application did not make enough
difference for one to feel that its universal use is necessary.
MEAN SENSITIVITY
Another criterion which helps in selecting the best record has
come into practical and important use, even though the computation
of numerical values is a refinement not usually applied. It is called
mean sensitivity (see also p. 104) and is an inherent character in each
individual. It may be denned as
Moist
upland
Dry
limate
V ' s
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1.00 0.33
1.00 0.64
the difference between each two
successive rings divided by their
mean. The quotients are arranged
in groups of 10 or some other
number of years, and listed as the
mean sensitivity of that period.
Plate 3 shows the appearance of
rings of different sensitivity. The
first section (B) came from a
sequoia which grew in a swampy
basin about 15 miles east of the
General Grant National Park.
The tree had a "complacent"
growth, with all rings of nearly
the same size. Its mean sensitivity
is 0.11. The second is a sensitive
sequoia which grew near the top
of the mountain, 800 feet higher
up, with a limited water-supply and therefore more dependent on
the moisture of each year as it came. Its rings have more character
and individuality, and the changes from ring to ring are much more
evident. The mean sensitivity is 0.33. The third is a hypersensitive
dry-climate yellow pine near Prescott, one of the 10 used in the curves
of Prescott tree-growth already described. It grew near the lowest
limit of the yellow pine. Some of its rings, such as 1841 and 1857,
are so small as to be found with difficulty. Its variations from year to
year are extremely large, and its mean sensitivity is 0.64.
The way these variations in sensitiveness look in plotted curves
is shown in figure 3, in which the curves of growth of these three trees
show percentage departures, each from its own mean. The different
character resulting from the different environment is at once apparent
to the eye.
1840 1850 I860
Three types of sensitivity
Fig. 3 — Mean sensitivity and soil moisture
30 CLIMATIC CYCLES AND TREE-GROWTH
Practical application — The practical method of handling mean
sensitivity is to take the sum of all the changes in 10 years without
regard to sign and divide by the sum of the 10 years' growth. This is
the way it has been used in the limited mathematical tests. As a
matter of fact, high sensitivity in a ring sequence is often apparent
to the eye, as anyone can see in the illustrations, and in much exploring
work the eye estimates have been the practical and rapid way for
using this criterion in judging between ring records.
SELECTION WITHIN RECORD
The recognition of the preferable parts of a sequence of rings comes
from an understanding of the natural divisions of a tree's ring system
due to age and the recognition of the various kinds of errors and
difficulties in the rings themselves. Most important of all perhaps is a
knowledge of the meaning of rings in terms of their environment.
This last part of the subject is discussed in Chapter VIII.
PARTS OF A TREES RECORD
All parts of a tree 's record are not equally useful. For purposes of
description a good record may roughly be divided into infancy, youth,
maturity, and age. These are largely recognized by the size and
character of the rings.
Infancy rings — These are most easily found in the sequoia and
consist of a central series of extraordinarily large rings, sometimes
2 cm. in width, 10 to 50 in number, showing practically no variation
except a successively diminishing size. They are very soft and in very
old trees often disappear, leaving a conical hole extending to some
height from the ground up into the tree. This is probably the explana-
tion of the rather common central hole, sometimes untouched by fire,
as shown by study of stumps. This was formerly attributed to other
causes, but some recent identification of the central parts of very old
trees described above under "Vertical uniformity" have favored this
view.
Youth — The youth of a tree is evidenced by large complacent
rings, usually largest in the center and outwardly growing regularly
smaller. Speaking from an economic point of view, the tree at this
time has to build a large trunk in order to support the growing top
and resist wind. It is true, as Antevs pointed out, that at this stage
the tree shows large, less sensitive rings. In the yellow pine this
period is likely to be 20 to 40 years, but even in these immature rings
in many trees cross-identification is perfect almost to the center.
This is not always so, and often it is best to drop the inner 20 rings.
The youth rings of the sequoia cover perhaps 300 to 800 years.
It is the region where the rings are large and show a gradual diminu-
RINGS 31
tion. Cross-identity carries through it usually with perfect ease. It
is not always easy to recognize the end of this period. In rare cases a
tree gets down to small growth in 200 years. It is possible that tests
of mean sensitivity would provide a means of judging. In addition,
actual climatic change enters here as a variable. A considerable
number of the dated trees started near 300 b. c. and show the reduc-
tion in ring-size near 400 to 600 a. d. It is probable that there was a
climatic drying at about that time which helped these trees to reduce
ring-growth.
Maturity and age — Maturity in pines and sequoias covers the
time from the attainment of full height to the decay at the top which
indicates old age. During this period the rings have their best sensi-
tiveness, though almost equal sensitiveness may last into old age, when
the rings become smaller and possibly a trifle less sensitive and yet a
trace more erratic. That is, there are longer periods with little varia-
tion, broken by a little more frequent complete disappearance of a
ring from the sample under study. The growth has gone to some
other part of the circumference. These are the unusual cases. It has
never seemed desirable to discard the outer parts of a tree so long as
the rings were certainly identified.
RING ERRORS
Superfluous rings — The one fundamental quality which makes tree
rings of value in the study of climate is their yearly identity. This is
sometimes disturbed by the presence of too many or too few rings.
Superfluous rings are due to doubling. This is a climatic phenomenon
to which some trees are especially liable, probably from their location
and rapid growth. But let us keep clearly in mind that superfluous
ring formation is the exception. Out of 75 trees collected near
Prescott, only 4 or 5 were discarded for this reason. Out of hundreds
near Flagstaff, none have been discarded on this account.
Nearly 200 yellow pines and spruces from northwestern New Mexico
have produced no single case of this difficulty. The sequoias from
California, the Douglas firs from Oregon, the hemlocks from Vermont,
and the Scotch pines from north Europe give no sign of it. On the
other hand, 10 out of 16 yellow pines from the lower levels of the
Santa Rita Mountains south of Tucson have had to be discarded, and
the junipers of northern Arizona have so many suspicious rings that
it is almost impossible to work with them. Cypress trees also give
much trouble. Trees whose extra rings can not be exactly identified
are always excluded in part or as a whole.
Missing rings — The other difficulty connected with yearly identity
is the omission of rings. Missing rings occur in many trees without
lessening the value of the tree, unless there are extensive intervals
32 CLIMATIC CYCLES AND TREE-GROWTH
over which the absence produces uncertainty. A missing ring here
and there can be located with perfect exactness and causes no uncer-
tainty of dating. In fact, so many missing rings have been found after
careful search that they often increase the feeling of certainty in the
dating of rings.
Missing rings occur when autumn rings merge together in the
absence of any spring growth. This rarely, if ever, occurs about the
entire circumference of the tree. There are a few cases in which, if
the expression may be excused, I have traced a missing ring entirely
around a tree without finding it. I have observed many cases in which
the missing ring has been evident in less than 10 per cent of the circum-
ference. Some are absent in only a small part of their circuit. I have
observed change in this respect at different heights in the tree, but
have not followed that line of study further. It can be studied in the
longitudinally bisected tree. A missing ring is often represented by a
slight enlargement of the red autumn ring of the previous year.
One sees from this discussion what the probable errors may be in
mere counting of rings. In the first work on the yellow pines, the
dating was done by simple counting. Accurate dating in the same
trees (19 of them) later showed that the average error in counting
through the last 200 years was 4 per cent, due practically always to
missing rings. A comparison in 7 sequoias between very careful
counting on the stump and accurate dating in 2,000 years shows an
average counting error of 35 years, which is only 1.7 per cent (Volume
I, pp. 15 and 45).
Simulated doubles — In the process of counting and dating rings
in Arizona pines, two sharp red rings sometimes occur close together,
giving the appearance of a double and leaving one in doubt as to
whether one year or two is involved. In such cases the following
probabilities apply: If the tree has other obvious doubles, the case
in hand is likely but not certain to be another doubling. If the two
red rings are unequal in size and the smaller one is inside, that is,
nearer the center, it is likely to be a real double formed by the spring
drought. If the smaller one is outside the larger, it is probably a
separate year. If the two rings are equal and either one shows a
further doubling, the two rings in question are separate years. If
the case is still doubtful, cross-identification may settle it. But if
that fails, the doubtful part should be discarded. The most tantalizing
case of this kind that I have is an early historic beam from Pecos,
KL-I, in which all kinds of doubles are exhibited.
Reinforced rings — Certain groups of prehistoric specimens from
the Wupatki National Monument, northeast of Flagstaff, show heavy
reinforcement in the youth rings of many trees. That consists of
very hard tissue formed during the rapid spring growth, so that each
RINGS 33
ring is greatly expanded in one direction and somewhat diminished
on the opposite side. This gives the appearance of a series of cres-
cents on one side of the tree section. It usually interferes completely
with the rain record in the tree, but at the same time has a strong
climatic significance as an indicator of heavy spring winds.
Other false rings — Other abnormal rings are sometimes produced.
Sequoia radials occasionally show certain "pitch" or "pith" rings.
These are white, very narrow, and totally different in color from the
rest of the wood. If they seem very soft, they have been noted as
pith rings; if hard, as pitch rings. They may come either within a
year's growth or between two years. They therefore are very annoy-
ing, for they destroy the count, it being impossible to tell whether the
normal rings on each side belong to one year or to two. I have made
it a rule to discard entirely regions of ring record thrown into doubt
by such rings. Doubtless they come from injury and usually from
fires. In the yellow pines no similar rings have been noted, but in
each tree abnormally large rings occur close to large fire injuries during
the early period of recovery and diminished rings in other parts of
the tree circuit.
Effect on means — In all cases of ring errors that leave any uncer-
tainty in dating, the uncertain part, or even the whole tree, is omitted
from the means. In large groups, of course, the omission of a tree is
usually a small matter, but in the early years of the group record it
may be serious, for the number of individuals decreases as we go back
to earlier and earlier dates. In such cases only the uncertain part
is omitted. But here another difficulty is introduced, namely, the
break in the averages at the beginning and end of the omitted part. If
the tree in question agrees very closely with the mean of the rest in
size of rings, the break does not introduce error; but if it is very
different, it has to be merged with the average of the rest in some way.
This becomes the same problem as that of introducing a tree of late
starting-date into a long group record.
V. INSTRUMENTS AND TECHNIQUE
In dealing with the 175,000 growth-rings, dated, measured, and
used in these volumes, special tools have been adopted or developed
at every stage of the process to secure material and to hasten and
improve results.
COLLECTING TOOLS
Saws — The articles needed in field trips include a chisel for marking
numbers, paper and cloth bags for holding fragments cut from individ-
ual trees, a recording notebook, marking crayon, a shoulder-bag,
camera, and various saws and borers. The best handsaw is known
as a flooring saw, in which the teeth are on a curved edge of steel,
as shown in Plate 2, A. With this, one can make a v-cut in the middle
of a stump without touching the edge at all, or the saw can cut in from
one side to the center without touching the other half. In working
without help this has saved many hours of labor and energy. The
convenient size of saw has a blade about 20 inches long. A 3-foot
cross-cut saw used by lumbermen does at times prove very useful,
but its extra weight and awkwardness in packing have always been
against it.
Swedish increment borer — Since 1920 the Swedish increment borer
has been used extensively to get records from living trees. It is very
successful in softwoods such as pine and fir. Hardwoods and juniper
are too tough for penetration without great danger of breaking the
instrument. The cores obtained are very slender, smaller than a pencil,
and reach to slight depth in large trees, but the method of mounting
has been raised to such a degree of efficiency and the collection of
material becomes so rapid that the deficient length and occasional
worthless specimens are counterbalanced. In most regions the incre-
ment-borer material can be supplemented by a few cuts from stumps
carrying the tree record back into the past as far as the forest permits.
Thus the borer supplies the contemporary record, that is, the last 100
years or so from many trees, and the saw supplies the historic record
going back for centuries.
In countries where native timber has been cut off and the yearly
"crop" of lumber comes from planted and reforested areas, it is very
important to know how growth is progressing. So Swedish ingenuity
produced this tool for sampling the outer rings of a tree. The borer
is a tube of 4 to 5 mm. inside diameter (i to i inch) with a sharp
cutting-edge and prominent spiral threads to draw the tool into the
tree by twisting, as with an auger. Near the cutting-edge is the largest
outside diameter of the tube, about half an inch. A tubular cross-
34
INSTRUMENTS AND TECHNIQUE 35
piece handle, which at the same time serves as carrying-case for the
cutting-tube, gives a strong purchase in turning the borer. When the
tree is bored as far as desired or practicable, a long, fine wedge is
thrust into the cutting-tube from the open end outside to hold the
core tightly in the cutting-tube while the borer is screwed out from
the tree. The first turn, of course, breaks the core away from the
tree and the core may be pulled out intact by the wedge. A difficulty
with this tool is the fact that in soft and watersoaked wood the outer
and softer layers are sometimes compressed and twisted. This is
usually negligible, but on one occasion in a dead sequoia the water-
soaked wood wedged in the borer so firmly that it had to be removed
by boring another tree and thus pushing out the wedged fragments
(boring in fallen sequoia at 215 feet from base of root, shown in part
in figs. 1 and 2).
Core mounting — The cores usually come out intact, but gluing
pieces together is so satisfactory that breakage is no drawback. The
core is at once numbered in pencil every inch or two of its length, so
that its pieces may be identified if it breaks. It is then put in a paper
bag long enough to hold it and a full record made on the outside of the
bag. Other numbered cores and their records are added in the same
bag, as they help to keep each other from breaking.
These cores are mounted on half-round strips of wood 12 inches
long and f inch wide. A shallow saw-cut is made lengthwise at the
rounded top, and this cut is rounded with a small round file so that the
core will he snugly in it. It is then glued with the bark end to the
right and about 1 inch from the end of the mount. The number is
placed at once on the mount at that end. In gluing, the vertical grain
of the tree is turned over into a horizontal position. This gives a
chance for just the right stroke with the razor blade in "shaving" the
surface so that the rings are brought out into the greatest prominence.
Identification and dating notes are placed on the wooden mount.
The various groups of these mounted specimens are tied in bundles and
filed in drawers of the proper width and depth. Such samples resist
very rough handling, last indefinitely in this form, and are always
ready for further study.
Mr. Duncan Dunning, of the Forest Service office at San Francisco,
has made a temporary clamp of great convenience, in which the core
may be held while measures of its rings are made. Considering the
vast number of cores used by the Forest Service and the ease of
replacing lost or injured specimens, this temporary mounting is
extremely valuable.
Borer extension — The 12-inch borer is the one commonly used,
giving a practical 10-inch core. A 10-inch borer was first tried and a
14-inch has been under examination, but seems too heavy. Very long
36 CLIMATIC CYCLES AND TREE-GROWTH
borers for greater depth in the tree will probably have to be made in
single pieces of tubing.
The tubular borer — This borer was designed especially for the
dried and sometimes very hard logs in the prehistoric ruins. It will
work on pine trees and junipers. It gives a core 1 inch in diameter,
which means a better chance of finding obscure rings than in the
increment-borer cores. The borer is a 1-inch steel tube with small
sawteeth at one end and a projection at the other for insertion in a
common brace. Collections to date include some 30 or 40 very valuable
cores made with this instrument. In actual operation the core has
been broken off and drawn out about every 3 inches in order to help
get rid of sawdust. This extraction is done by a i-inch steel rod
with a wedge at one end for breaking the core off and a screw at the
other end to catch the core fragment and draw it out.
There are two chief problems with a borer of this sort — sawdust
and the labor in pressing the borer into the tree or log. For the former
a 1-inch auger hole carried below the borer hole and a little in
advance has been used advantageously, but frequent breaking of the
core is more certain. For the latter a chain-drill attachment was tried
unsuccessfully, as it cracked the borer. An auger guide for limited
depths is working extremely well in some cases. This guide is a hollow
cylinder 4 inches long and 2 inches diameter, with thick walls. Length-
wise down these walls i-inch holes are placed fairly close to each
other. This guide is screwed to the tree or log with the guide-holes
pointing toward the center of the tree. Then a small auger bores into
the tree through the holes in succession. The guide is then removed
and the tubular borer quickly frees the core. In this arrangement
the auger holes take care of the sawdust and the auger itself needs no
pressure for forcing it into the wood. The core is not so presentable
in appearance, but is easily rounded to a desirable form. This makes
a very good form for use on prehistoric beams, but does not solve the
problem of deep boring in living trees. A device using the principle
of the chain-drill attachment is now under test. There is no doubt
that a suitable depth borer can be developed. An effective length of
28 or 30 inches would be enough for the yellow pines. A borer to go
12 feet into big sequoias would probably have to be designed for use
with an engine or motor. One would have to be sure beforehand that
living trees would supply data worth the trouble.
Injury to living trees — It has been an invariable custom to plug
the holes made in living trees so as to keep out any possible infection.
This is easily done with a small branch from the same tree, cutting
the bark entirely away, so that only healthy sapwood goes into the
hole. This amounts to grafting a young branch onto the trunk. Even
without this precaution it is not probable that any harm results, as the
holes quickly fill with sap or pitch.
INSTRUMENTS AND TECHNIQUE 37
Razor-blade holder — In giving a final superb finish to the wood
surface, nothing has been found to replace the razor-blade. Files,
emery cloth, and scrapers always leave the edges of the wood cells in
a ragged state. This may be overcome to some extent with kerosene,
oil, or furniture polish, but after clean cutting with a sharp razor-blade
the oil finish is far superior. Also, in decayed or burnt wood, after
treatment with paraffin, the razor leaves a surface which will permit
adequate magnification. Different forms of mounts could easily be
made, but a round steel handle split down an inch with a hack-saw
and a good screw to draw the split ends together serves as a very
convenient mount for the safety-razor blade.
Paraffin treatment — Soft or mealy wood or charcoal is rendered
workable by a treatment with paraffin dissolved in gasoline or benzine.
This solution should be applied copiously, so that it may enter deeply
before it dries. Putting the whole specimen into a jar containing the
solution has been found very satisfactory where practicable. Boiling a
frail specimen in paraffin is an excellent method of preservation to
apply while out in the field.
MEASURING INSTRUMENTS
EARLY FORMS
Ruler — As would be expected, the first measures were made by
readings from a steel ruler on edge against the wood. These measures
were all made by the writer and were subject to the errors of estimating
tenths of a millimeter, but in coarse rings such errors play very little
part.
Cathetometer method — This method was worked out for the very
long sequoia records and is still regarded as the standard method.
It was described in Volume I and need not be repeated here.
PLOTTING MICROMETER
It seemed possible to save a large amount of time by some method
of plotting direct from the wood and a special instrument has been
designed and constructed for the purpose.
General plan — In general plan the instrument has a fairly inexpen-
sive screw, 6 inches long by about 1 cm. in diameter, with threads
having a pitch of 1 mm. A knurled head and a graduated head are
attached at the right end for turning and for special reading if desired,
but the graduations have not been used (see Plate 5) .
The nut on this screw, by a single point of contact, moves a carriage
supported on a separate track. The carriage has two upright pieces,
between which a small telescope swings on a horizontal longitudinal
axis. The left end of the main screw opposite the graduated head has a
knurled head which is removable. Below this head, but not in contact,
38 CLIMATIC CYCLES AND TREE-GROWTH
is a similar head, also removable. The latter is attached to a small
drum with spiral thread about it, in which works a catgut string.
Between these two knurled heads, but not touching them, is an alumi-
num disk on the end of an arm, so made that by pressure on a lever
the disk comes into contact with both these knurled heads and thus
transmits the motion from one to the other and so from the main screw
to the catgut string. Several pairs of these knurled heads of different
relative sizes are supplied, so that motion in the catgut will be 20, 40,
or 100 times the motion of the carriage and telescope. By this means
change may be made in the vertical scale of the plot.
Below the main screw and parallel to it is the plotting cylinder.
This is so arranged that the same lever-arm that brings contact between
the knurled heads moves this cylinder 2 mm. in rotation, measured
on the surface of the record paper. The ends of the catgut string pass
over rollers and extend parallel to the recording cylinder, and after
one end turns back on a small wheel the two ends meet and are attached
to the pen carriage, which travels on its own track parallel to the
recording cylinder. Thus, when the lever-arm is pressed and the
micrometer screw moves the telescope thread across a ring, from one
sharp outer edge to the next, the pen draws a line in proportion trans-
versely on the record sheet. The release of the lever-arm at the left
moves the cylinder, and the pen is restored to zero position. Thus a
columnar plot, here called "auto-plot", is made by setting on one ring
after another.
Accuracy — The rapidity and mechanical accuracy of this instru-
ment are high. The graduations of a steel ruler were measured with
a very small percentage of error; that is, the accuracy is greater than
the accuracy of setting on a ring.
Advantages — The instrument saves much time, because it makes
automatically the plotted records which in the cathetometer method
were plotted from the readings: These automatic records are called
auto-plots. The distance of the wood from the telescope does not
have to be fixed. In fact, I have measured rings in wood lying in
glass cases by placing the instrument on the outside of the case.
The records are in a convenient form and may be very long. They are
made on coordinate paper to definite scale, so that values may be
read off from the plots for use in tabulation. The plot is also ready
at once for a standardizing line, such as will be discussed below.
Disadvantages — While the rapidity and accuracy of this method
exceed any other, its disadvantage lies in the difficulty of checking and
correcting the work after it is done. Coarse rings are readily handled
by inexperienced helpers, but the fine ones under 0.5 millimeter are
subject to mistakes. This is usually a question of identification, but
the difficulty in checking work immediately after it is done (without
Carnegie Inst, of Wash. Pub. 289, Vol. II (Douglass)
<}?
A. Plotting micrometer
B. Longitudinal plotter
\ff\
l^^ll ' > ilM
C. White cyclograph
INSTRUMENTS AND TECHNIQUE 39
doing it completely a second time) is great, and so these errors of
identity are not discovered until a careful revision is made by the
writer. All this refers, of course, to the measurement of records care-
fully dated beforehand.
Measuring directions — The best plan for preventing errors in
measuring is a written set of measuring directions, telling where to
begin and end, what rings, if any, to omit, which are small or micro-
scopic or absent, and where dangerous doubles occur. When a radial
sample is specially illuminated during measuring in order to see the
rings well in a telescope, marks and directions on the sample may
easily be overlooked, but a separate list on a paper at the side can be
followed with greater success.
Other applications — Extensive experience with the ordinary filar
micrometer in astronomical work led to a design of this instrument
which could be used on a telescope for the repeated measurement of
the same distance, such as planetary diameters, separation of double
stars, and so forth. The box of the plotter was arranged to receive
on one side a bushing adapted to the slide-tube of a big telescope and
on the other a positive eyepiece. Close to the eyepiece is a plate
carrying a stationary thread, while another plate attached to the
carriage has the movable thread. The latter is first placed on the
left side of the planetary disk and the stationary thread on the right.
Then the lever-arm above described is pressed and the movable thread
carried to the right until it reaches the right edge of the disk when
the other is at the left edge. Thus the double diameter is measured.
This may be repeated as many times as desired before looking at the
record. A thread stretched along the tops of the columns will give the
mean value. This same method can be used in the measurement of
average seed diameters under the microscope or the sizes of grains of
sand or other objects under special study.
LONGITUDINAL PLOTTER
The measuring instruments so far described all require accurate
dating beforehand, for corrections are hard to enter after the ordinary
transverse plot has once been made. It happened that considerable
material came to the laboratory with groups of very small rings
which I did not have time to date, but at a time when there was
available the help of an assistant. It was therefore desirable for him
to put on a ring-count and make measures which I could correct at
my leisure. This was accomplished by the longitudinal plotter (Plate
5, B). It simply reproduces the spacings which exist on the wood on a
large scale that can be varied to suit the needs of the rings. It repro-
duces very rapidly and two independent records are placed side by side
on the long paper tape such as is used in adding machines. This is
called the longitudinal plot, or more briefly, the "long-plot." The
4
40 CLIMATIC CYCLES AND TREE-GROWTH
instrument consists simply of a slow-moving carriage on which lies
the wood sample and a fast-moving drum upon which hangs the record-
ing tape. These are connected by gearing which normally permits the
surface of the drum to move 12 times as fast as the carriage. A pair of
gears may be removed and another pair substituted, giving different
ratios, so that the range of magnification is from about 4 to about 34
times. In this way a convenient size is entered on the recording tape
and the record becomes partially standardized. The motion of the
carriage and specimen is watched through a small stationary telescope
placed a few inches above and f ocussed upon the rings and the motion
of the drum is recorded on the tape by a pencil line drawn across it
against a fixed wire.
Accuracy — On the whole, an inexperienced assistant can handle
this plotter better than any other form of measuring instrument.
The duplicate records side by side check each other nicely. It is still
subject to errors of identification, but a large quantity of dated speci-
mens have gone through this process with good success. It is doubtful
if the settings have been quite as accurate as in the auto-plot, but they
are still as good as the sharpness of the rings permits.
Graph and table — A sheet of coordinate paper is marked with dates
and then each ordinate is entered simply as the sum of the lengths
of that year in the two adjacent longitudinal plots. This gives an
ordinary graph on which a standardizing fine may be drawn, as
described below. Suitable ring values for entering in a group table
are then read off directly from the graph.
CLERICAL OPERATIONS
STANDARDIZING
Need of equalizing trees — The groups of trees used in this study
represent different regions. Therefore, the individuals of each group
were selected to represent a considerable area rather than a localized
spot. Hence the individuals differ in rate of growth. What we want
in an average of a group is the common character which has come from
climatic variation. In the tables in Volume I a simple average was
used, as that was the easiest process and commonly used in scientific
reports. But it is perfectly evident that a straight average does not
represent an average of the common character, because in ordinary
averaging the big rings in quick-growing trees dominate and variations
in the slow-growing trees are practically lost. Logarithmic averaging
has been considered; for example, multiplying the values from the
different trees together and extracting the root corresponding to the
number of trees used. But that is a long and expensive process, and
it renders serious the occasional microscopic or omitted ring in very
slow growing trees. The effect in such cases would be greatly over-
INSTRUMENTS AND TECHNIQUE 41
done. So the practical method of standardizing or equalizing trees,
which has been used extensively for actual curve production (commonly
modified as in the next paragraph), is to divide individual values by
the mean value of the tree, so that the annual values of each tree will
enter the group table as percentage departures from its own mean.
Simple averages are then taken for each year in the group. This
avoids some of the exaggerated effect of extreme departures. It
places all the trees on an equality, but does not place all departures on
an equality. It is averaging by weight, in which the weight is inversely
proportional to the mean growth of the tree.
Age correction — Young trees have to develop the trunk rapidly
in order to stand the strain of wind and snow. Hence the early rings
are larger and somewhat less sensitive to climatic effects. When the
tree curve is plotted, it usually rises at the early end, sometimes very
rapidly. A reduction to percentage departures does not correct this.
One can correct it by getting percentage departures from a type curve
developed mathematically, as Huntington did (1914), but it can be
done far more rapidly and with sufficient accuracy by drawing a curved
or broken standardizing line on the individual plot and getting the
percentage departures from this line. Such a line is usually straight
and horizontal for a large part of the record and slants upward at the
early end. A curve is more accurate than a broken fine, but there is
little real difference and the broken line is more easily described if it is
necessary to state its position in words.
Other corrections — Huntington used a " flaring" correction for the
increased measured width of outer rings near the base of the big trees,
where the spread of the root system is felt and a horizontal measure-
ment is not perpendicular to the rings. Evidently, in drawing a
standardizing line this can be taken care of. It is evident that in
studies of cycles not exceeding half a century or so in length the flaring
effect is negligible. But in estimates of very long periods or of secular
values, this effect must be nicely gauged.
It is much the same with his " longevity" effect. This effect simply
recognizes that a slow-growing tree has a different normal age-curve
from a quick-growing tree. The slow grower more quickly reaches
the normal slow growth. This, too, is important in getting early abso-
lute ring values, but plays little part in studies of periodic variation.
Comment on standardizing — It is felt that standardizing serves
two purposes: first, correction for age, injury and flare, and second, it
compensates for few numbers in a group, so that 5 or 10 trees will give
practically the same results as 25 or 100. It is not thought important
to use it if the number of trees used in a group average is over 15 and
the age variations are small.
42 CLIMATIC CYCLES AND TREE-GROWTH
Averaging — The sums are usually made on an adding machine
and the divisions by slide-rule. Once or twice an average by weight
has been made. If some character is recognized that makes the record
in one tree better than that in another, a suitable weight can be
included in the standardizing process by placing the standardizing
line at a different ordinate. In the table the same effect has been
produced by repeating the same tree in two or more lines, giving it
double or more weight.
CYCLE PLOTS
Uses of tree-growth curves — There are three main purposes in
producing tree-record curves and certain advantageous characters
vary in these uses. They follow.
Cross-identification — Curves for this purpose must display certain
special characters like single small rings or drought groups of small
rings, which from their extreme and unusual character are likely to
extend over a considerable district. The single small deficient ring
is the best characteristic to use in dating. Good years seem to spread
their effects over a longer period of time and are not definite.
Skeleton plot — In consequence, a special "skeleton" curve has
sometimes been successfully used in cross-dating. Such curve is a
long, narrow strip of coordinate paper, dated or numbered as usual
and showing only the dates of very small microscopic or absent rings,
which are indicated by vertical lines whose conspicuousness is propor-
tional to the deficiency of the rings. No other rings are represented in
these plots. Two of these skeleton curves from different trees, one
known and the other unknown as to date, can be moved slowly past
each other until similarity of spacing discloses identity in dates.
Plotting climatic curves — By comparison of growth-curves the
climatic origin of many tree variations is established; hence these
curves need to show all the individual years. The scale should not
be too great, as then it is difficult to compare two plots. Therefore,
the ordinary form, consisting of points connected by straight lines,
made on such a scale that slopes dominate, is the more convenient.
It has been found most advantageous to use coordinate paper whose
smallest divisions are 2 mm. and whose major fines are spaced at 5
(not 10) of these small divisions. On this paper the smallest horizontal
division commonly represents one year and rather commonly 2 vertical
centimeters represent 1 mm. of tree-growth.
Cycle plots — These are the curves arranged specially for studying
the cycles. At first it was thought that the usual unsmoothed plots
just described were well adapted for this purpose, but it was noticed
that in searching out some cycle with the periodograph, or cyclograph
as it will usually be called in this volume, several possible settings
INSTRUMENTS AND TECHNIQUE 43
were obtained differing by exactly one year, such as 17.1, 18.1, and
19.1 years. This, of course, arose from retaining annual points in
the plot and in the cycle one was apt to select some multiple of unity,
that is, simply a whole number or very close to it, instead of an actual
fractional value.
Smoothing — Accordingly, some form of smoothing is now always
used, and the Bloxam formula, which I have sometimes called Hann's
formula, is generally accepted. But there are several variations of
this process.
Numerical Harm — The first is the simple application of the Hann
or Bloxam formula, in which three successive (overlapping) values are
merged into a substitute for the middle one by averaging the three,
with double weight given to the second. It is this double weight
applied to the original whose substitute is desired that differentiates
this formula from a running mean of three. The place of this emphasis
will be referred to below. This process may be done on a set of tabu-
lated values by two successive sets of intermediates, as explained in a
previous volume.
Geometric Hann — This is the same process, done graphically on a
curve already plotted, by taking each three successive points as the
corners of a triangle. Consider that the first and third points form
the base. From the center of the base, one-third of the way to the
middle point will be the running mean of three, while one-half of the
way from the base to the middle point will be the weighted mean or
the "Hanned" value. This forms in practice a very easy way of
smoothing a curve and has been very largely used in a slightly abbre-
viated form which I have called the graphic Hann.
Graphic Hann — The plotting paper used in the cyclograph needs
to be 4 inches wide by some 45 inches long, fairly opaque, and with
parts of the curve cut out so that light may pass through. All this is
best done on rough brown paper cut in strips of the proper size. The
present process, therefore, is to plot the tabular averages directly on a
long strip of coordinate paper, using a rather large vertical scale, so
that variations will generally be an inch or two high. This strip is
placed upon the heavy strip of brown paper with carbon paper between
and a blunted needle or pointer is passed slowly along the plotted
curve, touching the points which by eye estimation and occasional
measure should constitute the geometric Hann. Century dates at
the same time are touched, so that the curve thus transferred becomes
a satisfactory working smoothed plot of the standardized group
average. This is called the graphic Hann and can be done quickly
and accurately. This process of smoothing has a perfectly definite
ideal to look to in case of doubt and I believe is almost entirely free
44 CLIMATIC CYCLES AND TREE-GROWTH
from erratic estimations, on account of which ordinary eye-smoothing
may be criticized. The graphic Hann thus formed is the basis of the
cycle plot whose process of formation will be continued below.
Emphasis point — In the Hanning process just described the
emphasis is laid on the middle point of the three. This has been used
in so large a part of this curve-production that it is here given pref-
erence. But there is some question about its use when conservation
is considered, for it intimates a reversed or negative conservation in
the last year of the three (see p. 101). If rainfall is retroactive, that
is, if it affects rings already formed, the tree records ought to show
some anticipation of abrupt changes in the rainfall. On the other hand,
placing the emphasis on the last of the three years used amounts to
admitting a conservation of moisture from the two preceding years.
On the whole, it is felt that middle-point emphasis has given more
satisfactory curves than emphasis on the final year.
Cutting-line — The cycle plot has the maxima of the curve cut out
so that light may pass through. The curve produced by the graphic
Hann forms the upper side of this area to be cut, but the position of
the base of the cut area has proved very important in the successful
use of the analyzing instrument and therefore I have always had the
curves at that stage returned to me to have the base or "cutting-line"
marked. In any analysis the variations of the curve are the important
features; hence, if the cutting-line is placed along the X-axis or the true
base of the curve, the variations are reduced to very small percentages
of the total light coming through and can not be seen. Even when
the cutting-line is placed at the lower minima, the light is so abundant
that it is very hard to get the variations visually or photographically.
After extensive trials of every sort of height for this line, I have come
to the general plan of sacrificing about one-third of the vertical height
at the bottom of the minima and marking a long, sweeping line nearly
straight, but not entirely so, as that brings the best display of varia-
tions within the range of the instrument and has not been found to
affect the results.
The range of the instrument as now in use is confined to periods
between 6 and 32 years (see "Recent changes," below). The cutting-
line, therefore, to show these best, may be curved so as to cut out or
reduce longer periods. They, however, are taken care of by plotting
at a reduced scale. This has been done extensively with long sequence
of rings extending 500 years or more.
Cutting the plots — The final work on the cycle plots is cutting out
the maxima, which, of course, is a simple matter usually done with a
razor blade.
INSTRUMENTS AND TECHNIQUE 45
THE CYCLOGRAPH (PERIODOGRAPH)
COMPARISON OF ANALYZING METHODS
This study of tree-rings has become a study of the history of
climatic cycles. The technique so far described covers the production
of tree-record curves ready for analysis by a special instrument
designed for the purpose and called a cyclograph. The number of
curves to be analyzed is so great and the data sought so complex that
this work would hardly have been done by a mathematical process.
Harmonic analysis in its mathematical form has been so successful in
numberless studies that many investigators have come to regard it as
essential. A very clever illustration of its power is Miller's reduction
of a facial contour to a mathematical formula which when plotted
reproduces the contour. Of course, this was done by combining a
long descending scale of period lengths with the distribution of empha-
sis (amplitudes) on just the right ones. But after this beautiful illus-
tration we must not forget that this form of contour analysis has
nothing to do with the physical causes of the contour, nor does it help
us in predicting other contours. It is like a photographic plate: it
merely places that one on record.
So in the case of the sunspot cycle, we can reproduce the known
historic sunspot curve by 20 harmonics with different amplitudes, but
when done we can not insist that the sunspot variation is really built
of those harmonics. So also with climatic cycles, we do not know yet
how far their physical causes are harmonic, and therefore the expression
of climatic variations in a Fourier series begs the question. Evidence
in a later chapter suggests distinctly that climatic cycles are simple
fractions rather than harmonics of a fundamental. So the photo-
metric process described below is permissible. Add to this its rapidity,,
which is of the order of 50 times as great as the mathematical process,
while its flexibility belongs to a different class altogether. The mathe-
matical process is not flexible at all in the sense this is. The process
here used bears somewhat the relation to the mathematical process
that calculus does to algebra; it is differential. In applying a cycle
to a long sequence of values, one sees at once at every point how far
the values depart from the cycle. A varying cycle enters simply as a
curved line, while a fixed period appears as a straight one. Two
interfering cycles, forming a false third, enter as two straight lines or
bands intersecting and their intersections form the third. In this
process the operator not merely gets an analysis of the whole sequence
of values, but of every possible fraction of them, an accomplishment of
the highest difficulty in any mathematical solution. For example,
Schuster analyzed the sunspot variations since 1750, dividing the
whole series into two parts, and missed the points of discontinuity
near 1788, 1830, and so forth. These discontinuous points are the
most conspicuous features of the cyclograph analysis here used.
46 CLIMATIC CYCLES AND TREE-GROWTH
On the other hand, some will object, and correctly, that the cy olo-
graph process does not give in figures the harmonic constants. Two
points answer this; the first is that the cycle must first be caught out
of a very complex combination of variables, and second, when the
cycle is known it is easy to get its constants by mathematics, if desired
(or by photometric means from a cyclogram).
PRINCIPLE OF THE CYCLOGRAPH
The earlier forms of the instrument have been described in the
previous volume and need no repetition. The principle also was
explained, and is briefly outlined here only as an introduction to the
present form. The maxima of the curve to be analyzed are cut out,
so that light passes through in proportion to the ordinates, as already
described under the title Cycle plots. The horizontal spacing of the
maxima of light is emphasized if the cutting-line is high, leaving the
extreme minima without illumination. Now let us imagine a plot of
this sort consisting of a series of evident maxima which seem to be
equally spaced (as in the sunspot curve), and we wish to find if they
are strictly periodic. We illuminate the curve from the back, place
a lens at some distance before it, find the image cast by the lens, and
compare the white spots in the image with an adjacent series of dots
which we have placed on exactly equal spaces. If the dots are closer
than the maxima, the lens is carried farther from the curve, reducing
the separation of the focal images until they coincide in the average
with the equally spaced dots. Then we see clearly that the maxima
largely match the dots but in certain places; let us say, they draw
away. These departures let us call differentials.
So long as differentials take place in their own line (like the longi-
tudinal vibrations of sound) it is hard to estimate them, but if these
differentials can be turned out perpendicular to the line of the curve,
that is, made transverse (like fight- waves), it is very easy to see and
measure them. This is very easily done by extending both maxima
and dots indefinitely in the transverse direction but at a small angle
to each other. This effect is produced on the curve image by adding
a cylindrical lens which converts each maximum of the focal image
into a vertical band. The same effect is produced on the dots by
inserting in their place a series of equally spaced nearly vertical opaque
parallel lines. To give these lines accurately, a ruled screen such as
that used in photo-engraving is placed at the focus of the lens and
the row of vertical bands comes through the slightly inclined trans-
parent spaces between the lines. This produces an interference which
should be seen to be appreciated. If the maxima are equally spaced,
they come through as straight horizontal rows of white spots, but
where differentials occur, the spots are displaced above or below the
i straight line. Departures from a perfect period are at once recognized,
INSTEUMENTS AND TECHNIQUE 47
because longitudinal displacement has been turned to transverse,
thus making a departure from a straight line which is at once apparent.
Invention and name — This pattern was first designed by the writer
in 1913 and published in 1914 under the name of a multiple plot.*
Its automatic production by this method of interference was worked
out that same year and published in 1915. It was then called a
differential pattern and was used as the basis from which to photo-
graph a true periodogram, as described in Volume I. In the present
volume, however, the periodogram is omitted, since there has been
very little use for it in comparison with the pattern. With the con-
struction of small portable instruments for producing this pattern,
the word cycloscope has come into use as their name. In a correspond-
ing way the large analyzing instrument with its photographic attach-
ment, constructed with the fund given by Mr. Clarence G. White, of
Redlands, California, has come to be called the White cyclograph;
the photographs obtained by it are here called cyclograms.
THE WHITE CYCLOGRAPH
During the building of the previous instrument in 1918 the thought
in mind was the production of a periodogram as suggested by Schuster.
But with the extensive use of that instrument it became apparent
that the differential pattern or cyclogram designed as merely one
stage in the process was far more important than the periodogram.
The periodogram merely produces the kind of results that come from
a mathematical process; the cyclogram contains far more than that.
At the same time, the long track of the periodograph compelled
the observer to walk indefinitely back and forth in an awkward
position. So it was first intended to arrange a mechanism to eliminate
this walking, but as it took form the lessening importance of the
periodogram was realized and the attachment for producing it was
omitted. It could, however, be added at any time if thought worth while.
Illuminator — The arrangement for mounting the cycle plot so
that fight comes through in the proper way is called the illuminator.
For a long time daylight was used, thrown onto the curve in a dark-
ened room by a slant mirror at the base of a window. Then thin
white tracing-paper replaced the mirror and gave a broad area for
comparing different curves. One curve some 40 inches long and 4
wide was insufficient and a second could be put above it. But for close
comparison of many curves for dating purposes a light frame sliding
vertically was arranged to carry 10 curves at once. This frame was
suspended by a cord over a pulley and analysis could pass from one
curve to another at any desired speed.
*It appears to be identical with Clayton's "phasogram" in World Weather, page 379. The
multiple-plot method of making a periodogram was described to him in conversation in the
summer of 1913, and he remarked, "Well, you might expect an astronomer to work out an optical
method."
48 CLIMATIC CYCLES AND TREE-GROWTH
When it became necessary to move the instrument to a locality
where a suitable window was not available, 10 electric lights in a row
were used, with a mirror behind and several thicknesses of ground
glass between the lights and the curve to spread the light evenly.
This is mounted on a table or stand, but it is planned to combine all
this equipment with an attachment which will permit the curve to
turn on its center through a horizontal angle, for by this means the
range of analysis can be greatly extended beyond the previous 32
years. This slanting of the curve can only be done when it is at
maximum distance from the lens, for the two ends would come in at
obviously different scales. To do this the whole illuminator will have
to turn on a central vertical axis.
Track and carriage — The cyclograph track is 18 feet long (see
Plate 5, C), made of light beams well braced, carrying cross-pieces,
notched at each end to hold two lengths of i-inch round steel shafting
which serve as rails. The rails are 18 inches apart. The carriage has
two grooved wheels on one side to run on one rail and hold the align-
ment. On the other side is a single flat wheel.* The carriage holds a
vertical mirror 30 inches wide and 15 inches high, facing the illumin-
ator and the analyzing-box. Seen from the mirror, the former appears
slightly, but directly, above the latter. The carriage is moved by a cord
passing over a small wheel at the outer end and a drum with small spiral
groove about it at the observer's end. This drum has a handle within
reach of the observer as he sits at the side of the analyzing camera.
Scale — The scale runs along the side of the track and the carriage
has a mirror and light so arranged that the observer may see the
lighted scale at any position of the carriage. A small telescope is
provided for reading the distant positions. The graduation is put on
from standardized curves, which are always kept on hand and measured
and tried from time to time. In dry climates all curves shrink per-
ceptibly and thus scales have to be watched.
Range extension — The actual length of the track covers a range of
periods from 5 to 18 years. In order to increase this to 32 years, two
mirrors have been used, one fixed high above the track, throwing a
beam back toward the analyzing-box, and the other at the front of
the box in this beam, so placed that when it is raised in position it
catches the beam from the first extra mirror and sends it to the mirror
on the carriage, at the same time cutting off the direct light from the
curve to the carriage. This nearly doubles the maximum path of the
fight from the curve to the analyzing-box and increases the range of
periods tested from 18 years to over 32 years.
Camera inclination — One bit of awkwardness remains in this
design, namely, the necessary change of slant of the camera-box when
♦This same carriage was used on September 10, 1923, in photographing the total solar
eclipse from the University of Arizona station at Port Libertad, Sonora, Mexico, with a 40-
foot horizontal telescope.
INSTRUMENTS AND TECHNIQUE 49
the movable mirror is changed in distance. In order to get the reflec-
tion from the mirror properly placed, the box has to have its plate end
lowered when the mirror comes near.
Cyclograph camera — By the track-and-mirror arrangement, above
described, the observer can stay at one point while the moving mirror
changes the effective distance between the curve and the lens, and
by changing the size of the focal image brings into view all the range
of periods of which the instrument is capable.
Lens. — The lens is a Tessar II B of 6 inches focus and about
i-inch aperture, with a negative cylindrical simple lens of —6 inches
focus with horizontal axis, so that in the vertical direction it neutral-
izes the action of the main lens. Without the cylinder there is an
ordinary image at 6 inches. With the cylinder all the horizontal spacing
comes in as before, but there is no vertical focussing; consequently,
each maximum in the curve appears in the image as a vertical band
whose intensity is proportional to the height of the maximum.
Automatic focus — The lens is mounted as in previous instruments
inside and on the base of a suspended parallelogram with hinges at
each angle. The length of the parallelogram extends along the axis
of the instrument, in line with the track. This permits a focussing
motion of the lens in its axial line. From the front of the parallelogram
a lever-arm extends downward and is attached by an adjusting-screw
to a horizontal rod passing forward toward the axis of the drum which
moves the mirror-carriage. A cross-piece on the rod bears against a
brass spiral mounted near the axis of the drum and turning with it.
This spiral is so arranged that as the drum turns, the position of the
lens changes and the focus is maintained in a fixed plane.
Analyzing-plate — The analyzing-plate is fixed at the focus of the
lens in a brass mounting attached to the back of this front compart-
ment of the analyzing-box. The mounting has been elaborate enough
to test many details and is rather more complete than ordinarily
needed. On the fixed plate is a circular brass plate which can be
rotated through 45° against a graduation in degrees. A rectangle 1
inch high and 2 inches long is cut through the circular plate, and on
this rectangle is mounted the analyzing-plate, covering a little more
than the rectangle. The ruled lines of the plate are vertical, that is,
parallel to the short side of the rectangle. In normal position the
circle is clamped so that the fines are inclined 12° from the vertical,
and therefore 12° from the vertical bands in the image.
The plate itself is made of two screens accurately ruled 50 lines
to the inch, face to face, one fixed and the other with a slight motion
controlled by a screw. The purpose of this is to change the relative
size of the transparent part of the ruling without changing the distance
from center to center of the fines. In each screen the opaque ruling
is equal in width to the transparent space between. So by moving
50 CLIMATIC CYCLES AND TREE-GROWTH
one screen slightly across the other, the transparent part can be
changed from zero up to 0.01 inch. The width found advantageous
is 0.004 inch or two-tenths of the spacing of the lines.
Visual compartment — From the analyzing-plate the light passes
into the middle or visual compartment through the condensing-lenses.
These are two 6-inch positive cylindrical lenses with vertical axis, so
that the eye placed 6 inches away may receive all the light from the
plate and see its whole area. It is more convenient to have the observer
at the side than at the end, where he may interfere with the light
coming from the curve beyond, so back of the condensers is a vertical
mirror on a hinged support. When the support is pulled forward, it
takes a position at 45° and throws the beam out at the side through a
small lens and to the eye. The lens puts the image slightly out of
focus to the eye, as in such condition the eye recognizes alignments of
blotches better.
Photographic compartment — When the mirror-support is thrown
back out of the way, the beam goes straight on to a triple lens of 3
inches focus, which reproduces the analyzing pattern on a ground
glass in the third and last compartment. This last compartment is
held separate on a clamp by which the ground glass may be brought
to the most advantageous focus. A plate-holder fits in place of the
glass and may occupy three slightly different positions, so that three
exposures can be made on the same plate.
Recent changes — The above description gives the form of the
instrument used in the cycle analyses in this volume. But since
writing this chapter added floor-space has made it possible to lengthen
the track to 40 feet. With this the two extra mirrors have been
removed, together with the automatic focussing device and scale
illumination, and a small convenient scale is now located directly in
front of the observer.
CYCLOSCOPE
A small portable analyzer has been constructed for exhibit pur-
poses, but fully equal to real analyzing work. It consists of a small
illuminator with a long electric light inclosed and cord to be attached
to a wall-socket. Curves 10 inches long may be placed in this. The
analyzing part is a box 12 inches long and 4 inches square, with top
which opens on a hinge. It carries a convex spherical and a cylindrical
lens at the front, with a little chance to focus by hand; then a simple
analyzing-plate fixed at the proper inclination; then condensing-
lenses and an eye-lens. One looks through it toward the illuminated
curve and walks nearer or farther and watches the changing pattern.
When a cycle is indicated by proper horizontal alignment of spots in
the analyzing pattern, its value may be found by a simple formula
after measuring the distance from the lens to the illuminated curve.
VI. TREE RECORDS: LENGTH
The first definite purpose in making the collections here described
was the extension and improvement of the 3,000-year sequoia records
presented in the previous volume. This was followed by a similar
plan in regard to the yellow pine as soon as certain probabilities
of extension were realized. The present chapter deals with these
attempts. As the number of specimens grew and material came from
many sources, the study of local and continental topographic effects
took shape and has become a central theme of this volume, as indi-
cated in the succeeding chapters (VII and VIII). Finally, large
quantities of early historic, prehistoric, and geologic material came
to the laboratory and the problem was presented of reconstructing,
in part at least, the climates of past ages by such indications as could
be found in tree-rings. Hence arose the thought of collecting and
formulating climatic indicators in trees (VIII). All this is of funda-
mental importance in the continued investigation of climatic cycles
and tree-growth (IX).
OLD SEQUOIA RECORDS
THIRD SEQUOIA TRIP, 1919
The trip to the groves near General Grant Park in July 1919 was
made for the purpose of determining the status of a certain ring called
1580 A, which was in doubt because it had appeared in less than half
of the 23 specimens at that time in hand. It was also planned to make
a topographic study of the influence of the immediate environment,
especially ground-water, on ring-growth. After a trip to Wigger's,
just south of the Park, to see an immense stump, and after an examina-
tion of the General Grant tree to estimate its age, I went to Hume and
on the 12th accompanied a guide to the farthest parts of Camp 6,
where Nos. 1 to 5 had been collected, and selected new specimens for
cutting. The next day, with burros and a helper, camp was made at
the mouth of Redwood Basin, near the spring. With no one to help, the
radial pieces cut here the next morning were not on the scale previously
obtained. Instead of being 6 or 8 inches wide and deep, they were
about an inch in those dimensions. This meant their breaking into
many small pieces, which were immediately put into small marked bags.
The new specimens supplemented the 13 already obtained in that
district and gave opportunity of testing more thoroughly the relation
of sequoia growth to ground-water, which will be discussed in a later
chapter.
The next day we cut a new radial from D-12 in Indian Basin,
which had previously failed to give a satisfactory dating on account
51
52 CLIMATIC CYCLES AND TREE-GROWTH
of badly compressed rings near the outside. A good radius was
selected and a conspicuous ring was traced across from the new radius
to the old and its position on the old accurately determined. It
proved very easy to extend the dating on the new radius back to this
ring, and with this good start the entire dating of this tree proved
very satisfactory, in spite of the complacency of its growth.
We returned to the Park and the next day I cut radials 32 to 35 at
Converse Hoist. These supplemented the two obtained the year before
in that vicinity by going higher up on the ridges for Nos. 32 and 35
and nearer the creek for 33 and 34.
This locality is a very interesting one, because it contains the
stump D-21, which had 3,200 rings in it, whose central rings were
shown in Plate 1. Very old trees are rare. I have examined many
hundreds of stumps, made estimates of their age, and in many cases
have counted the rings. There were in these forests many trees over
2,000 years of age, but probably very few over 3,000. Only 3 stumps
of this age are known so far. Two estimates of the General Grant
tree gave 2,000 and 3,000 years of age, and its true age is thus taken
as 2,500 until some better opportunity comes for getting its number of
rings. The Centennial stump nearby was estimated to have some
1,800 rings and the large stump with raised center at Wigger's probably
is 1,500 years of age.
FOURTH SEQUOIA TRIP. 1924
The fourth sequoia trip in July 1924 had two objectives; first, the
improvement of the general sequoia record, and second, the securing
of certain indicators needed in the problem of correctly dating large
numbers of prehistoric tree-sections from the ancient ruins of the
Southwest. Such dating would not only help the archaeologist, but at
one stroke would also extend the superb yellow-pine climatic record
by more than 300 years at least. The general problem of dating
unknown tree-records will be taken up at another time. It is sufficient
to say here that one way to accomplish such dating is by cross-identifi-
cation between the pines of the Arizona region and the sequoias of
California. This apparently would be easy by comparison of the
occasional common deficient years, perhaps eight per century, except
that in about one-fourth of such cases the Arizona deficient year
occurs one year late. For example, the small sequoia rings for 1846,
1812, 1541, and other years in California come in 1847, 1813, 1542,
and so forth, in Arizona. The attempt is, therefore, now being made
to discover in the pines or sequoias, or both, some internal signs by
which to know just when this difference of one year is to be expected.
Hence, in approaching this problem from the sequoia point of view, it
seemed best to go to other sequoia groves and see if some indication
of this occasional discrepancy could be discovered.
TREE RECORDS: LENGTH 53
Accordingly, a trip to the northerly Calaveras Grove was made in
early July 1924, by stage from Stockton. This grove was the first
one discovered and the marble slabs with tree names are reminiscent
of the pioneer days. The hotel is picturesquely situated at the edge
of the grove and nearby is the Dance Hall mentioned by Mark
Twain. This hall is on the stump of the first big tree cut (1853) and
the early difficulty in penetrating such immense trunks is apparent,
for in this case it was done by large auger-holes made on opposite
sides toward a selected diameter. These holes show in the great butt-
log still lying close to the hall. This tree was quick-growing and
estimated to have some 1,200 or 1,400 rings only. It was probably
the one from which a tracing of the whole set of rings was made
about 1865.
The road, as it approaches the hotel, formerly passed between the
"Sentinels," two fine sequoias, but one had fallen the previous year
and a boring in it at some 50 feet from the original ground-level,
checked by a similar boring from another fallen tree, gave a perfect
start in dating the trees in this grove. This actual dating, however,
proved unnecessary, for it was perfectly easy to date all the records
obtained by comparison with the known records in the more southerly
groves. The trees in this grove are standing and, therefore, it was
difficult to get any satisfactory radials. However, a very few old
trees had fallen and small pieces were cut from three in inconspicuous
places by which the record was carried back some seven centuries.
Incidentally, this dating of fallen trees gave excellent data on the dura-
bility of sequoia bark and sap wood already referred to.
This grove is small, perhaps one-third of a mile across, and lies in a
flattish, slightly depressed area with drainage to the southwest and
protected on the other sides by hills and ridges a few hundred feet
high. Its elevation is 5,000 feet and the precipitation in this neigh-
borhood is probably near 40 inches, mostly in winter. The ring-
growth is very complacent, with deficient rings showing but rarely.
The average size is smaller than expected. The easy cross-identification
with the tree records in the other groves shows that the entire area of
Sequoia gigantea in California is essentially a unit in its climatic reaction.
A full day was given to collecting yellow-pine borings in connection
with the study of modern tree-records over the whole western area.
Trees were selected in an east-and-west line across the grove from the
hilltop back of the hotel to the ridge on the east, where the main
highway passes and the trail to the South Grove branches off. These
pines cross-identify well and are included in the western groups under
the abbreviation CVP. Eleven trees comprise this close group, but
three more were added at elevations nearly 2,000 feet above sea-level
in the vicinity of Murpheys. These three, however, give essentially
the same record as those near the grove and are included in the CVP
54 CLIMATIC CYCLES AND TREE-GROWTH
group. The Calaveras Grove of sequoias is privately owned and
these specimens were obtained by courtesy of Mrs. Whitesides, in
charge at the hotel.
FIFTH SEQUOIA TRIP. 1925
The dating of the specimens from the Calaveras Grove led to the
conclusion that the tree-records there resemble the Arizona pine-tree
records less than the sequoias farther south, instead of more. So it
only remained to visit the most southerly grove near Springville and
secure better material than already collected there. In 1918, two
3,000-year old radials had been secured from the Old Enterprise mill-
site. These both cross-identified with trees 50 miles north near the
General Grant Park, but while the cross-dating was absolutely reliable,
the resemblances were not so close as hoped for and were not equally
good in the two trees. No. 23, age 3,100 years and growing near the
drainage brook, showed less agreement than No. 22, age 3,000 years,
growing near the center of the grove. Accordingly, the trip was made
by auto from Pasadena to Springville on August 4, 1925. Mr. Charles
A. Elster, of that city, met us and next day took us to his Camp
Lookout and sawmill in the pines at an elevation of about 5,000 feet
above sea-level. After lunch he drove us up the steep grades, past
the old Frazier mill-site of 1885 and the Elster mill-site of 1901, to the
Enterprise site of 1898. The Conley mill of 1892 at Brownie Meadow,
off the road to the north, was close to D-49, which had been cut by
Mr. Elster himself in 1892. Mr. Elster had worked here in the lumber
business almost since its beginning and his recollections were of the
greatest help. The afternoon was devoted entirely to the selection
of suitable stumps for cutting. It seemed advisable to get the very
oldest and, if possible, to exceed the previous maximum of 3,200
years (but that hope was disappointed). At the same time it was
desired to get a range of younger trees in order to develop an improved
system of age corrections.
The next day the cutting of radials began. This was done by
two helpers in charge of Mr. P. W. Weirick, of Pasadena, who very
kindly assisted me on this trip, thus enabling me to spend the entire
time in the selection of specimens. So two days were spent in this
way and in securing specimens of pine growth (see p. 88), and on
Saturday, the 8th, Mr. Elster took us to Balch 's Park to see the marvel-
ous old tree appropriately named Methuselah. That afternoon we
returned to Springville and the next day to Pasadena.
On returning to Tucson, several of these long sequoia records were
dated, including one of 2,600 years, but it finally seemed best to
postpone the complete study of this material to a time when proper
attention could be given to old and prehistoric records in connection
with climates of the past. Hence, its further discussion will be reserved
for another time.
TREE RECORDS! LENGTH 55
COAST REDWOOD RECORDS
The value of very long and old ring records is so obvious that
every effort has been made to discover them. The coast redwood is a
very available tree, growing to a great age, but its preference for the
coast's even climate and its avoidance of winter snows led many years
ago to doubts of its usefulness in these ring and climate studies.
Moreover, about 1912 the late Julius Kapteyn did some counting on
the rings of the coast redwood in the hope of finding climatic or solar
correlations, but was disappointed. At any rate, the possibility of its
usefulness deserved a real test and two groups of this species have been
collected.
SANTA CRUZ GROUP, 1921
A trip made on February 20, 1921, was arranged through the
kind assistance of Mr. R. E. Burton, of the high school in Santa Cruz,
who took me out some 15 miles in a northerly direction from that city
to a point near Major's Creek, where redwood trees had recently
been cut. This location was in the upper part of the low range of
coast hills, but on the eastern slopes, so that the drainage was toward
the northeast and inland at that point. The first trees selected were
at the upper end of a gully, often dry; others were cut in the valley
bottom and others on the very steep slopes of a side-wash. The 7
specimens collected there were studied for months and no satisfactory
cross-identification was found. Trees 10 feet apart cross-identified
and gave apparently good records, but other trees 50 yards away
gave a different record which could not be identified with the first.
In the outer parts of some good specimens the rings would interlace
in a way never noted in the big sequoia; for example, some red rings
merged in one direction with the ring next outside and in the opposite
direction with the red ring next inside. Dating was therefore hopeless
and has not been accomplished to this day. The general age of these
trees was not great, probably from 300 to 700 years.
SCOTIA TRIP, 1925
The above negative result was not conclusive, for it might be a
characteristic of the locality chosen or of the southern redwoods only.
So the long auto trip of June 1925, described later, was directed to the
redwood region of northern California. We motored from Grant's
Pass, Oregon, to Crescent City, on the extreme northern coast of
California, and thence through those wonderful redwood groves to
Eureka and Scotia. At Eureka, the center of the redwood-lumber
industry, I consulted representatives of the Forest Service and was
referred to Mr. Percy J. Brown, whose mill and forests were on or near
the main highway to the south. The general area included a square
mile or so of bottom land some 30 feet above the level of the Eel River.
This land rises very gently toward the hills on the south, but the slope
5
56 CLIMATIC CYCLES AND TREE-GROWTH
grows steeper in the outwash-fan from a small canyon entering the
hills. Twelve stumps were selected of different sizes and at various
scattered points. Of these, three were high up on the ridge forming the
east side of the canyon. Here the cutting had been done some years
and the young sprouts of redwood from the stumps formed dense and
tangled masses which had to be cut away in order to get at the stumps.
In the bottom lands below the cutting had been recent, some of the
trees having been felled only a few weeks, so there was no difficulty
about getting the final dates. The v-cuts were 4 to 6 inches wide and
deep and thus were excellent specimens, well selected and in perfect
condition. They were prepared and mounted by Mr. Swan Erickson
at Tucson under my direction and cross-compared by him and later
by me, but no cross-identification was found. Some of the bottom-
land specimens seemed to have perfectly clear records, yet with close
study the different trees did not agree. It may be that further study
will produce some way of using these good specimens, but so far they
are not usable in this study of climate and solar activity. This is
unfortunate, since many of them carry records over a thousand years
in length.
DEFICIENCY OF THE COAST REDWOOD
Though it is true that years ago the theory was entertained that
winter snow is important in producing trees that give good climatic
records, this failure of the coast redwoods was a surprise. Probably
the subsoil water-supply and certain habits of the tree itself increase
these nonclimatic variations. The trees get much moisture from the
coast fogs, and Mr. W. P. Hoge, of Mount Wilson, tells me that in a
fog the trees show some very curious anomalies in their capacity to
take moisture from the air. Again, if moisture is in too large a quan-
tity, sunshine would be the controlling factor in growth, though this
is not at all likely in the southern groves. But a greater difficulty lies
in the way these trees reproduce after fire, which is by sprouts from
the base of the mother tree. Hence, these trees when near together
are apt to be connected underground. This method of reproduction
leads to very erratic growth, as observed by Dr. Emanuel Fritz, of
Berkeley. In a letter dated May 15, 1923, he says:
"This section of second-growth redwood is interesting because it
shows a large number of rings merging into one and thus on some radii
giving an incorrect indication of the age of the tree. In March we cut
three-quarters of an acre of second-growth redwood 65 years old and
under, and found to our amazement that trees were older at the top
than on the stump. Very careful study soon brought to light the fact
that we were not counting the rings on corresponding radii. After
this discovery we had no further trouble. As you know, redwood
sprouts very freely from the stump. As these suckers mature, they
crowd out one another and leave but two or three in a clump. Often
TREE RECORDS: LENGTH 57
the cambium layer is common around the group. We noted that on
that side of the tree which faces closely another sprout, there is a
dearth of growth-rings. On that side also there is practically no foliage
clear up to the tip. The most peculiar thing about this lack of ring
formation on one side is the sudden change from the normal to the
abnormal."
In another letter soon after, he says:
"The trees cut in this experiment .... were many of them
sprouts. Two to six sprouts, 15 to 35 inches in diameter at breast
height, were found around many mother stumps. This sprout-clump
habit makes the trees touch one another at the base (sometimes after
50 years to develop a common, or rather a continuous cambian ring
for two or three trees at stump height) and to be separated at the top by
3 to 6 or more feet. Tree No. 90, from which the specimen was cut,
was of this class. The crown was all on one side. The most difficult
thing to explain in the specimen seems to me to be the reason for the
sudden change from normal growth to asymmetry and then a return
to the normal."
The coast redwood may some time be used in the study of climate
and solar activity, but its interpretation is so complicated that for the
present it can not be included in this study of modern and historic trees.
OLD PINE RECORDS
For climatic records involving rainfall as the most important
factor, no tree has yet been found superior to the yellow pine of the
arid Southwest. It combines a wide range of growth with excellent
sensitiveness and a reluctance to drop rings completely in deficient
years (as the junipers do). Next to it, perhaps, comes the Douglas
fir, which has larger growth with usually greater sensitiveness, so that
for the same size of trunk it has fewer rings with over-exaggerated
representation of climatic changes. Therefore, extension of climatic
records in the pine trees is most desirable.
SEARCH FOR OLD TREES
In the summer of 1919, Flagstaff was visited primarily for the
purpose of investigating certain buried pine trees in the recently
filled land immediately north of town, which will be described in
another place. September 10 was spent in a "University" section, 5
miles south of town, a section which had long been pointed out as
having most beautiful pines with clear trunks, suitable for fine lumber.
These trees were on nearly level limestone, breaking to lower levels at
their south edge and protected to the west by the volcanic bulk of
Woody Mountain. There seems to be no special protection from the
occasional powerful northeast wind. This region had been cut over
recently and it was easy to select the large stumps with fine grain.
58 CLIMATIC CYCLES AND TEEE-GKOWTH
Of the 8 radials cut (Fl-33 to 40), 5 had an age of 500 years. Only 2
such trees had been found before. Thus by one day 's work a reliable
500-year record was obtained (see Plate 6).
Burnt centers — All this seemed so encouraging that on August 28,
1922, another visit was made to this locality for the purpose of collect-
ing " burnt centers." It had long been hoped that the tree record
could be carried back before 1,400 a. d. by finding stumps or logs of
earlier origin which in some way had been preserved. For example,
a tree blown down by the wind might be buried and thus preserved,
or it might have fire injury which would cause the central parts of the
stump to fill with pitch and thus withstand weathering. So on this
visit the larger burnt stumps were sought and partial radials cut from
their centers. Out of 5 so collected, numbers Fl-95 to 99, one was
too complacent for dating, 2 began about 1500 and 2 began before
1400 a. d. Of these two, one undoubtedly started by 1350, but the
very center had rotted away and no real gain was made. Yet these
two were thoroughly filled with pitch and presented records which
match in a remarkable manner certain dated beams from the pueblo
buildings of the Hopi Indians.
In the summer of 1920 two other 500-year trees were reported to
me at about the same time. On June 17 a radial from Fl-41, a 66-
inch stump in the northwest corner of Fort Valley, was cut. This
very old tree stood at the edge of the flat valley floor, in good soil,
near large outcroppings of volcanic rock, on which the Southwestern
Forest Experiment Station stands. Mountains protected it to the
west, north, and east, but not especially on the southwest and south-
east, and southwest winds are sometimes very strong.
On the following day another stump of even larger size was visited
near the top of Woody Mountain, 10 miles to the south. This was
numbered Fl-42. By courtesy of Mr. T. A. Riordan, president of the
Arizona Lumber and Timber Company, a full section of this splendid
tree was cut and shipped to Tucson. Each of these 500-year trees
was somewhat complacent; in fact, they and the still older tree men-
tioned below have decidedly less sensitive records than the previous
7 trees of that age. Five of these 7 had come from the university
section, some 3 miles east of Woody Mountain, and 2 collected in 1906
had come from about 2 miles west of the same mountain.
A 640-year pine — In early July 1923, Forest Assistant Merker
and Forest Examiner M. Westveld discovered a pine stump in the
canyon a mile up-stream (south) from Fisher's Tank and about 5
miles southeast of Flagstaff. By their first count this tree was 640
years of age when cut and subsequent examination confirmed that
figure. By courtesy of Mr. G. A. Pearson, director of the Southwestern
Forest Experiment Station, a large half section was cut for me and
Carnegie Inst, of Wash. Pub. 289, Vol. II (Douglass)
PLATE 6
r*
Q
A. Site of 500-year pines, Flagstaff, Fl. 35, in foreground; looking south
B. Stump of 640-year pine, Fisher's Tank, Flagstaff
TREE RECORDS! LENGTH 59
sent to Tucson, and later (July 13, 1926) he showed me the stump,
of which I include here a photograph (Plate 6, B). The canyon is
about 200 feet deep in the horizontal limestone strata and extends
north and south. Water flows occasionally. The stump is on the
east side of the canyon, 25 feet above the bottom and 50 yards from
the usually dry wash. The slope of ground about it is about 30°.
The date of starting was undoubtedly close to 1275 a. d. The earliest
measured ring is 1284, but a serious injury occurred, probably in
1294, greatly reducing the growth for some 8 years. Much decay has
occurred at this point, and though the dating is probably correct, the
normal values of the ring-width are profoundly reduced. Since the
first hundred years in this record were new, three radii were measured
and the average taken. The growth is somewhat complacent, but
much information is given by it for that century. It is probable that
important checks on it will be obtained from early historic beams in
the Hopi pueblos. This discovery renewed interest in the search for
very old trees, and it is possible that some living trees of similar age
have already been found.
Other 500-year pines — A 500-year pine was found in the group
of 8 from the Charleston Mountains, near Las Vegas, Nevada. It
showed with the other trees there a record rather intermediate between
the Arizona and California values. Also a fine v-cut from a pine stump
in the Crater National Forest of southern Oregon near Kirkford has
been sent me by the kindness of Lumberman John D. Hoist, of that
locality, acting for Mr. Fred Ames, assistant district forester at the
Portland, Oregon, office. In this connection, also, one might mention
the extraordinarily old juniper near Logan, Utah, of which a descrip-
tion has come from Supervisor C. B. Arentson, located there.
PREHISTORIC MATERIAL
The search for old pine records has taken a new turn in the use of
early historic and prehistoric pine logs in the Hopi villages and the
ancient ruins of the Southwest. This really began in 1916, when Mr.
Earl H. Morris, for the American Museum in New York, sent me
several early historic logs from Gobernador Canyon, near Aztec, New
Mexico. This led to a series of specimens from the ancient ruin at Aztec.
Aztec sections — A trip to Aztec was made in August 1919. An
examination of the logs in this ruin led to the construction of the
tubular borer, which produces cores 1 inch in diameter, giving the
series of rings from the outside to the center of the log without impair-
ing its strength and without disturbing the original house construction.
Following this visit, Mr. Morris spared no effort in getting me speci-
mens from some 50 logs used in the construction of that wonderful
ruin. Nearly all of these cross-identify perfectly in the Aztec-Pueblo
60 CLIMATIC CYCLES AND TREE-GROWTH
Bonito chronology. It seemed necessary to get some modern trees
from that vicinity, so Mr. Morris took me 40 miles north to Basin
Mountain, in southwest Colorado, where some 10 different trees were
sampled. To these were later added 9 tree sections from a point
about 20 miles east of Aztec. These together make a very satisfactory
group known in my lists as the "Modern H's," H being the group
letter applied to the old Aztec material.
Chaco Canyon beams — The Aztec sections gave a fine ring record
more than 200 years in length, but of unknown date. As soon as its
real date becomes known, that much length can be added to the cli-
matic record in the southwestern pines. An early shipment of Aztec
sections included several from Pueblo Bonito in Chaco Canyon, some
50 miles to the south. These specimens came from the American
Museum in New York City, where they had been deposited by the
Hyde Expedition 25 years before. Very soon these were found to
cross-identify with the Aztec sections, and they began to improve and
extend that prehistoric record. Then Mr. Neil M. Judd, director of
the National Geographic Society Expedition at Pueblo Bonito, became
interested in the possibility of developing the chronology of Pueblo
Bonito by the ring records and he has collected and sent me nearly
160 excellent specimens, mostly from that one ruin. Nearly a hundred
of these I have been able to place exactly in the Aztec and Pueblo
Bonito chronology. This chronology is referred to as R. D. or relative
date, since its true location in our numbering of years, "Anno Domini,"
is unknown. This Pueblo Bonito material has increased the prehis-
toric ring record so that it extends accurately from R. D. 230 to R. D.
543, a range of 313 years. A single beam extends it with uncertainties
about 40 years later. So if this material could be dated, some 350
years of record would be added at one stroke.
In connection with this collection two trips have been made to
Chaco Canyon, one in early September 1922, to get a better knowledge
of the beams there and of the problems connected with their dating,
and the other in September 1926, to study the living pines in that
region. On each occasion many specimens were collected, and on the
second trip much was seen of special interest in connection with
climatic indicators in trees, which will be mentioned in a later chapter.
National Geographic Society beam expedition — It is evident that
two different interests join in the attempt to date the beams in the
ancient ruins of the Southwest, namely, the extension of climatic and
solar records in trees, and the archaeological and human interest in
the age of those wonderful ruins. For the second reason, the National
Geographic Society has encouraged and supported the further collec-
tion of early historic and prehistoric material and otherwise assisted
in the dating ol these prehistoric beams. In general, two distinct
TREE RECORDS! LENGTH 61
dating methods are in view. The first is the " bridge" method, by
which we start with old living trees and cross-date the early parts of
these with late parts of earlier trees, and so on till a real ring record
is built back to the age when the ruins were under construction. The
other method is the "sequoia comparison" method by cross-dating
with the sequoias, whose great age without doubt covers the period of
building of these ruins. The best result would be one derived from a
complete agreement of these two methods. Perhaps the stronger of
the two methods is the first or bridge method, but it promises to
require large collections from many different ruins, beginning with the
early historic and going back to the period desired. Consequently,
in June 1923 an expedition set out for the purpose of making such
collections under the charge of Dr. J. A. Jeancon of Denver, assisted
by Mr. O. M. Ricketson, of the Carnegie Institution. I went with
them for the first 10 days in their visits to the Hopi Indian villages,
where some 22 specimens were collected. They then continued the
trip, covering generally the southwestern area, including such places
as Canyon de Chelly, Chaco Canyon, Mesa Verde, and the Rio
Grande Valley. To the present time their collections have not been
finally and thoroughly examined (such work will be done in connection
with the study of past climates), but it is practically certain that
extensive gaps remain in the long interval from the Aztec and Pueblo
Bonito chronology to a. d. 1300 or 1400, when the living trees began
their record. Nevertheless, this bridge method is probably only
delayed, for the collection from Pueblo Bonito reveals the possibility
that in some Hopi Pueblo or late prehistoric ruin will be found beams
cut in ages different enough to cover the long interval desired.*
CALIFORNIA AND ARIZONA CROSS-DATING
In the presence of the gaps above referred to, the sequoia com-
parison method becomes of increased importance and has played an
important part in directing our effort in the last few years. The visit
to the Calaveras Grove in 1924 and to the Springville Grove in 1925
were primarily to aid in this problem. The problem itself was stated
above in describing the purpose of the fourth sequoia trip, page 52.
CHARLESTON MOUNTAIN TRIP
In connection with the dating problem between Arizona and Cali-
fornia, the Charleston Mountains, at the southern extremity of Nevada
and about midway between the Flagstaff area and the best sequoia
region, were visited and collections made. Senator E. W. Griffith, of
Las Vegas, Nevada, kindly took me out on July 9, 1924, by automobile
*At the time of reviewing this chapter a group of 25 beams from " Wupatki" near Flagstaff
has shown that this ruin was built some 30 years later than Aztec. It seems very probable that
in time the "bridge" method will be successful.
62 CLIMATIC CYCLES AND TREE-GROWTH
some 30 miles west to the summer resort at about 7,500 feet elevation
in these mountains. The resort is located in a large, deep canyon on
the east side of the mountain and well up in the pines. A delightful
brook runs much of the time. The ring record from the trees collected
here is actually intermediate between Arizona and California, agreeing
in some parts conspicuously with the Arizona trees and in other parts
with California. The full discussion of these characteristics, in order
to see whether they help to solve the cross-dating problem, is planned
in connection with the study of past climates.
VIL TREE RECORDS: GEOGRAPHICAL DISTRIBUTION
The understanding of any special distribution of ring characters
over great areas is increased by personal acquaintance with the region.
So, in addition to much travel in the Southwest, both within and with-
out the State of Arizona, the writer has made two special trips in the
study of geographical distribution of tree-growth.
WESTERN CIRCUIT, 1925
This trip was made easterly from Tucson to the Rio Grande Valley,
thence up-stream to Albuquerque and east again to Santa Fe, where
the SF group had been collected in 1922; thence through the pine-
covered mountains to Las Vegas. Halfway between these cities we
passed Pecos, where the "L" group of four trees had been obtained, by
aid of the Forest Ranger. However, only one of these proved suitable
for dating, and so this is not retained as a group. The next day car-
ried us over the wide elevated plains of northeastern New Mexico to
Raton, whose mountain pass through the Rockies is high enough to be
pine-covered. Three of the trees near the road were bored, but only one
could be dated reliably, and as we already had a group from Cloudcroft,
New Mexico (CC group), this single tree is omitted. Later we went
along the eastern base of the mountains to Fort Collins, Colorado,
and Laramie, Wyoming. In the low hills between these two places,
the group LW (Laramie, Wyoming) was collected near the road.
The eastern face of the Rocky Mountains, extending north and
south for many hundreds of miles, is a striking feature of western
contours, and the groups in New Mexico, Colorado, and Wyoming
along this line and partly also the small Yellowstone group from
Specimen Ridge in the northeast corner of the park (collected in 1920)
give certain interesting characters which will be referred to later.
The next stop for collecting was 60 miles northwest of Baker,
Oregon. At a point where pine trees border the road as it passes over
the Blue Mountains, the BO (Baker, Oregon) group of 8 was collected.
On the eastern slopes of the hills near the road at The Dalles are more
yellow pines, of which a small collection was made, known here as the
DL (Dalles) group. In the low coast hills 25 miles northwest of Port-
land, a large group of Douglas firs was collected in 1912, as described
in Volume I. It now appears that this group, called OC (Oregon
Coast), does not cross-identify with the other western groups, probably
because its location close to the coast gives a very different climatic
environment.
The primeval forests of the State of Washington were extensively
cut along the settlement-line marked by the highway between Port-
land and Seattle. Much of the land was burnt over and the huge
63
64 CLIMATIC CYCLES AND TREE-GROWTH
burnt stump is a common sight. Stumps were examined in different
places and ring samples were collected at Victoria, British Columbia,
at Blyn, Washington, and at Toledo, on the Oregon coast, but the
growth was so exceedingly complacent that no special effort was made
to form a group. However, there is no real doubt that group char-
acters will show, if the right tree and location are found.
WESTERN CONTOURS AND RAINFALL
The important mountain ranges of the western States extend in
north-and-south rows, whose western slopes precipitate moisture from
the westerly winds. The long valley running north from the Gulf of
California, with the smaller parallel San Joaquin Valley in central
California, is the driest area, because the westerly winds are drying
winds as they descend into them.
Mechanism of Arizona summer rains — The maximum rainfall on
the coast is in winter, but the maximum in the northern parts of the
dry valleys just mentioned is in late spring, when their warming
causes the air to rise and move to the east and "pull" in the wester-
lies. In midsummer it is so hot that the moisture is reabsorbed even
before it falls and the amount that reaches the ground is small. The
same summer "pull" draws moisture-laden air from above the Gulf
of California far to the south (whose water temperature at Port
Libertad in September 1923 was 87° F.), and perhaps from other
warm bodies of water. This air, as it is drawn up over the mountains
and plateaus in its northward-moving path, gives up its moisture in the
common torrential summer rains of that region, strongest near the
Gulf and fading out in Utah.
Prediction possibility — If this statement of the possible mechanism
of our summer rains is correct, it would seem possible to predict their
amount, some months at least beforehand, by some formula involving
chiefly the mean temperature of the water in the Gulf of California
and of the desert areas of the western valleys.
The Rocky Mountains — The Rockies are high enough to catch the
westerlies and intercept a remnant of their moisture, and thus they
partake year by year to some degree in the winter variations which
come to the Pacific Coast. But in the warmer months the mechanism
just referred to as acting north from the Gulf of California produces
a similar effect north from the Gulf of Mexico, and the eastern Rockies
show a great summer maximum.
THE THREE ZONES
Thus, in reference to climatic types, there are three zones lying in
north-and-south strips delineated by the mountain ranges. On the west
is the Pacific or Coast zone, where the precipitation is only in winter,
from the westerly winds coming in off the ocean. The arid interior
region forms the Arizona zone, whose higher points where the pines
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 65
grow intercept the westerlies and partake strongly in the variations of
the coast. This zone has a secondary rainy season in midsummer,
torrential in character and producing for the most part only slight
effect on the tree-growth. To the east is the Rocky Mountain zone,
which catches a remnant of the coastal variations and gets its chief
moisture supply in summer.
Latitude effect — In each of these zones there is a strong latitude
effect. On the coast the westerlies are very powerful in the higher
latitudes, weakening south of San Francisco and becoming gentle at
San Diego. They disappear entirely in the tropics. In the valleys of
the central zone the spring rainfall maximum of the north changes to
the well-defined winter and summer rainy seasons of Arizona. The
eastern or Rocky Mountain zone has less latitude change than the
others. The total rainfall increases as we go south by the increasing
amount of summer rains. In Texas, and still more in Mexico, it
begins to show a temporary diminished rainfall in July and August
at the very peak of the maximum. Perhaps this is actually the tropical
winter minimum of the southern hemisphere reaching over thus far
into northern latitudes.
THE PUEBLO AREA
The Pueblo area trip was made in behalf of the National Geo-
graphic Society in connection with studies of the Pueblo Bonito
chronology. It seemed advisable to visit and test the pine and spruce
regions from which the prehistoric Indians drew their timbers and
find out whether such regions agree with the Flagstaff areas in their
tree-growth.
The Hopi villages — These villages, still occupied, he along the
southern edge of a raised and sloping plateau called the ''Black
Mesa," whose surface is dissected by canyons and whose highest
point, some 75 miles north of the villages, is near Kayenta.
Kayenta — The 24-hour trip from Flagstaff to Kayenta was made
on September 4 and 5, 1926. The settlement is in a valley just east
of Mount Lolomai, the highest point of Black Mesa. Mr. John
Wetherill, for many years well known in this region, took us to the
mountain top, 4 miles in a car, 4 or 5 more on horseback, and then a
climb of 700 feet on foot. Samples collected in several different places
all show the Flagstaff ring record, as do the rings in the beams of the
Wetherill house.
On September 7 we started to Chin-lee, 72 miles southeast, pass-
ing Chilchinbeto at 16 miles and confirming the agreement between
Black Mesa and Flagstaff by some specimens there.* At Chin-lee
we cut radials from logs in the store of Mr. L. H. McSparron, who very
♦Later, on the return trip, we stopped at Oraibi, the westernmost of the Hopi villages, and
cut radials from logs of spruce from Pinon, 30 miles northeast, with the same result.
66 CLIMATIC CYCLES AND TREE-GROWTH
kindly gave the necessary permission. These logs came from the
Lukaichukai Mountains east of the Chin-lee Valley, south of the
Chuskas and north of Fort Defiance and Gallup. A day on horseback
was spent in the wonderful canyons there, De Chelly and Del Muerto.
Then we drove southeasterly up onto the Lukaichukai Mountains and
obtained borings in several places, ending at the sawmill 13 miles
north of Fort Defiance. These borings and the radials from Chin-lee
agree with the Flagstaff series.
We motored southeast to Gallup and then 100 miles northeast
to Chaco Canyon, and there a most interesting search was made for
living pines, a number being found at distances of 2 to 20 miles east
of Pueblo Bonito. These pines, which appear to be a remnant of a
great forest on those mesas in past ages, also show the Flagstaff series
of rings. From Chaco our return trip carried us to Gallup, Holbrook,
and the Petrified Forest, Ream's Canyon, Walpi, Oraibi, Leupp, and
Flagstaff, 16 days from leaving it.
Rio Grande Valley — During a trip to the Rio Grande Valley in
April 1927, specimens of tree-growth from the Zuni Forest, south of
Grant's, New Mexico, and from the Jemez Mountains, west of Santa
Fe, were obtained. Each locality shows a perfectly clear Flagstaff
record.
Navajo Mountain — By courtesy of Mr. H. Richardson, a trip was
made in May 1927 to Navajo Mountain, Rainbow Bridge, and Rain-
bow Lodge. Specimens of Douglas fir from the south slopes of the
mountain show a perfect Flagstaff record. These recent collections
therefore leave no further doubt that the whole Pueblo area west of the
Rio Grande is homogeneous in its tree-growth and forms part of the
large Flagstaff area.
SOUTHWESTERN CONTOURS
The large southwestern arid area is bounded on the west by
the range of Southern California mountains, including San Antonio,
10,080 feet, San Bernardino, 11,600 feet, and San Jacinto, 11,000
feet, which, therefore, form a great rampart impeding the westerly
winds. East of this range is the Imperial Valley, with the Salton
Sea some 200 feet below sea-level. The Charleston Mountains form
an isolated island at the southern point of Nevada. East of the
Colorado River the land rises to the plateau of northern Arizona,
while in the southern part of Arizona the land rises to the east
very gradually, with many "island" mountains high enough to have
pine trees upon them. The Mogollon Mesa, often called the Rim,
is the bold and lofty southern edge of the Colorado plateau. It
cuts across the central part of the State, pointing generally a little
south of east. South of it are the island mountains; north of
it the land descends gently to the Little Colorado River and then
TREE RECORDS! GEOGRAPHICAL DISTRIBUTION 67
rises gently to the States on the north. On this slope the great
Black Mesa has large cedar forests, with pines in the canyons and along
the northern edges. Then to the east is the Chin-lee Valley, and east
of that, on the border between Arizona and New Mexico, is the range
called Chuskas on many maps, with a southern part called the Lukai-
chukais. These carry extensive pine forests. The next pine-covered
range is a hundred miles east and forms the western boundary of the
Rio Grande Valley. This range has Mount Taylor at its southern
end and the Jemez Mountains west of Santa Fe. Chaco Canyon is
in the large area between the Chuskas and the Jemez Mountains.
It is surrounded by mesas which probably once held pine forests, but
the mountains just named are higher and its rainfall is small. East of
the Rio Grande Valley the big masses of the Rocky Mountains begin.
WESTERN PINE GROUPS
Statistics — The whole number of tree records minutely examined
up to date is about 1,100, and the total number of rings is close to
210,000. Of these, about 175,000 have been dated and measured.
The extensive failures to date the coast redwoods are largely responsible
for this difference between rings examined and rings measured, and
many of the groups have had a small proportion of the trees which
could not be dated. The number of trees included in the 42 groups
whose cycles are studied below is 305 and the number of rings dated
and measured is 52,400. These trees are practically all western yellow
pines, with a few Douglas firs here and there.
Zone statistics — The 42 groups are divided into three zones:
(1) the interior or Arizona zone, where this study began and has had
the greatest extension; there are 14 groups in this zone, with 104
trees and 21,210 measures; (2) the eastern or Rocky Mountain zone
has 15 groups of 82 trees and 14,135 measures; and (3) the western or
coast zone has 119 trees in 13 groups, with 17,055 measures.
Miscellaneous groups — A number of other groups not included
in the subsequent discussion of cycles follow the western pine groups.
They consist of groups of different kinds of trees, groups of good trees
which did not have enough material, such as the Raton and Pecos
groups of yellow pines with only one record each, of trees which could
not be dated, such as the coast redwood, and of groups from distant
localities.
Group treatment — In the 42 western cycle groups only the individ-
uals are used which can be dated and also only those parts of each
individual which can be dated with certainty. In nearly every group
the curve of each individual tree has been standardized as described
in a previous chapter. Thus the different trees in a group have equal
weight and the age effect in the trees is largely removed.
68 CLIMATIC CYCLES AND TREE-GROWTH
Analysis — Three analyses were made, namely: (1) the full length
of the group curve, using maxima; (2) the part of the group curve
subsequent to 1750 a. d., using maxima; (3) the part of the group
curve subsequent to 1750 a. d., using minima, that is, plotting an
inverted curve and then cutting out and analyzing the higher (nega-
tive) ordinates as usual.
Precautions — Knowing the possibility of prejudice and systematic
error in analyzing this large number of curves, several precautions
were observed: (1) Settings of the White cyclograph were made with-
out knowing what the reading was going to be; (2) full analysis of
each curve was made without knowing which curve it was; (3) each
of the three analyses was carried through the complete list of curves
in one continuous sitting of four or five hours, so that possible errors
of adjustment or of judgment would apply equally to all groups; (4)
the instrument was calibrated from time to time with standard curves,
and its errors were of the order of one-tenth of a unit of period, which
is less than the error of an average setting, which is one to three
tenths of a unit, depending on conditions. Four critical parts of the
reduction process were invariably done by the writer, namely, dating
the rings, drawing the standardizing line, marking the cutting line
for the cycle plot, and making the cycle analysis. Other parts were
done mostly by assistants, such as mounting, measuring (checked
afterwards by the writer in most cases), tabulation, plotting, smooth-
ing, and tracing and cutting the cycle plot.
Analysis report — A cycle is reported below only when it occurs in
two of the three analyses, and its relative excellence is shown by a
number in parentheses following the cycle-length. This number may
be considered a "weight" and so an approximate amplitude. Unit
weight, meaning medium or average conspicuousness of the cycle, is
omitted. Weight 2 means a fine cycle and weight 3 a remarkable
cycle as viewed in the cyclograph. Cycles occasionally show a lesser
secondary maximum and very rarely two secondary maxima. In
such cases the fraction \ or \ respectively, in the parentheses with
the weight, gives indication of this doubling or tripling.
Abbreviations — For convenience, the names of the groups are
sometimes reduced to an abbreviated form which consists of some
initial letters as suggestive as possible. These letters are given after
the group title.
ARIZONA REGION
FIRST FLAGSTAFF GROUP (FL)
This group was collected in 1906, 1 or 2 miles west of Woody
Mountain and some 10 miles southwest of Flagstaff. Nineteen trees
numbered 7 to 25, were used; Nos. 1 to 6 were not preserved and there-
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 69
fore were not corrected by cross-identification, which was applied
to the others in 1912. The 19 original sections have been retained and
two sets of radials have been cut from them; one is the set measured
in 1906 and cut in 1912 and the other was cut about 1925, so that
accidental loss of the fragmentary pieces of the original sections would
do no harm. The curve values as extended to 1910 are given in the
appendix of Volume I, to which volume reference is also made for the
curve itself (p. 25) and further details. Measures were by ruler.
There were so many in this group that for the present purpose it did
not seem necessary to standardize each tree-curve, as has been done
in nearly all of the western-pine groups. The smoothed curve shown
in figure 4 was made by a graphic Hann. The cycles are 6.9 (3), 13.6
(3), 20.6 (2), and 28.3 (-J-).* It still remains uncertain whether the
cycle 20.6 years is a real value or whether it is a combination of two,
of which one is under 20 years and the other about 21 years.
FLAGSTAFF 500-YEAR GROUP (FLU)
This group was collected September 10, 1919. Mr. J. F. Freeman
measured the specimens by the cathetometer method. Long records
were sought at that time and the two 500-year trees, Nos. 12 and 13
in the previous Flagstaff series, were completely remeasured and added
to the five similar trees in this group, Nos. 33, f 34, 35, 37, and 40, and
a table of seven (unstandardized) trees produced. It is a plot of their
averages, 1750 to 1917, of which a graphic Hann is shown herewith in
figure 4. The use of the same two trees in each of these Flagstaff
groups probably has no real effect on the similarity between the two
groups, which is very marked, for all these trees give very nearly the
same record. The cycles found in this group are 14.0 (2), 20.6 (3),
26.7 (|), 29.1 (|), and 40 (£). The 20.6 varies from 20.2 to 21.0.
The two near 28 are perhaps variants of one cycle.
FORT VALLEY GROUP (FV)
This group is made up of complete sections cut in Fort Valley, 12
miles northwest of Flagstaff, by Mr. G. A. Pearson, for the purpose of
studying group effects, or the effect on tree-rings of near neighbors.
But practically no effect was found unless the neighbor was within
5 or 10 feet. The trees grew one-quarter mile northeast of the experi-
ment station, elevation 7,300 feet. Mr. L. R. Patterson measured
these rings by the auto-plot method. Each tree was standardized.
The final table and plot were made by Mr. W. G. Austin and the cycle
plots by Mr. F. M. Douglass. The curve 1686 to 1920, shown from
1750 in figure 4, resembles FL and FLU and is equally typical of the
*It will be noted that thia fraction means doubling and not weight.
fNos. 26 to 32 were cut east of Lake Mary in 1911 and are often called the LM group. They
are given in the curve on page 27 of Volume I, and as they were only small pieces cut from the
edge of the stumps, they are not used in this study of western cycles.
70
CLIMATIC CYCLES AND TREE-GROWTH
1800 1850 1900
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group curves
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 71
central Arizona area. It shows cycles as follows: 13.1, 14.5, 18.5,
20.5 (3), and 35 (3, J). The 13.1 and 14.5 are very possibly variants
of one about 14 years. The 20.5 again varies from 20.0 to 21.0.
HIGH LEVEL GROUP (FLH)
The idea of testing the effect of altitude on the ring-growth was
held from an early date. The first actual collection for it was done on
June 19, 1920, when Dr. E. J. Brown and the writer went on foot up
the canyon above Shultz Pass, where the Weatherford Boulevard has
recently been constructed. But the specimens were crudely cut and it
was felt that it would be preferable to test tree-growth on the west or
southwest slope of the mountain. Accordingly, on July 11, 1920, a
trip was made up the southwestern ridge of the mountain from the
southern end of Hart Prairie to the cabin used by the experiment
station at an elevation of 10,500 feet. Director Pearson and Mr. Haasis
of the staff were of the greatest assistance. A very interesting group,
numbered Fl 69 to 80, was obtained, including Douglas fir, cork-bark
fir, Umber pine, fox-tail pine, and Engelmann spruce. But this seemed
to combine too many different species over too great a range of alti-
tude; accordingly, the group of yellow pine increment-cores here used
was collected with the aid of Mr. Pearson on July 12, 1924, at eleva-
tions averaging a little under 9,000 feet, that is, really in two sub-
groups, one at the south end of Hart Prairie and the other at a little
over 9,000 feet altitude.
These 10 cores were measured by Mr. D. A. Hawkins, using the
long-plot (longitudinal plot) method, and were then tabulated and
averaged and the curve, 1770 to 1923, plotted without standardizing.
A graphic Hann, shown in figure 4, was made by Mr. F. M. Douglass.
In general appearance this smoothed curve has all its variations greatly
diminished and is otherwise somewhat discordant compared to the
usual Flagstaff tree-records. It introduces a 17-year cycle, which is
not common in this region; but its cycles belong to the Arizona class
and are as follows: 6.9 (2), 9.1 (oc. £), 13.7 (2, -J), 17.3 (3), 20.5
(2, oc. i), 27 (oc. i), and 35 (2, oc. £).
FLAGSTAFF SHADOW GROUP (SH)
The old-time winter road to all points north of Flagstaff passed
east of the San Francisco Mountains because it was drier, warmer,
and had less snow than the west side. The forest regions east and
northeast of the peaks are shaded by the mountains from the wet
westerly winds, and the special effect observed in this group and
others is called the shadow effect. This group of five Swedish incre-
ment-cores was collected on July 13, 1924, in a specially selected area
nearly on a fine between Sunset Crater and the peaks, and about half a
mile west of the main highway. At this place the elevation is very
6
72 CLIMATIC CYCLES AND TREE-GROWTH
little above that of Flagstaff and is about the same as that of the Fort
Valley group, with which the curve, therefore, can be compared for the
shadow effect. Mr. Hawkins measured these specimens by the long-
plot method and, without standardizing, plotted a curve from the
averages. This curve, 1717 to 1923, was Hanned mathematically and
the cycle plot was made by him also. This smoothed curve from 1750
on is shown in figure 4. The great variation between maxima and
minima is at once apparent and is characteristic of lower and drier
altitudes. The shadow effect does not appear to differ much from
simple reduction in rainfall, equaling in this case the effect of about
1,500 feet change of altitude. The spacing of the maxima is strongly
of the Flagstaff or Arizona type. The observed cycles are 14.1 (3),
19.4 (2), 27.3 (2, -J) and 40 (2, oc. £).
FLAGSTAFF NORTHEAST GROUP (NE)
This group was collected on June 14, 1923, in connection with
prehistoric dating problems, to determine with certainty whether the
part of the Flagstaff forest area nearest the prehistoric ruins carries
the same ring records as the very old trees just south of town. Dr.
E. S. Miller, of Flagstaff, was kind enough to take me out 19 miles on
the Tuba road and there, at the edge of the forest, I took four incre-
ment-borings. Mr. Hawkins measured these in 1923 by the auto-plot
method. These were thoroughly rechecked by the writer (as in all
cases). These individuals were so nearly alike in average growth that
they needed no further standardizing. The curve, 1678 to 1922,
identifies exactly with the Flagstaff record. It was smoothed by
graphic Hann by Mr. Austin and the part from 1750 on is shown in
figure 4. The cycle plot analyzes as follows: 8.5, 11.6 (2), 14.3 (2,
oc. £), 19.4 (2), 27.7 and 36 (2); these classify as Arizona type, though
the 11.6 is not so common as on the coast.
GRAND CANYON GROUP (GC)
The edge of the Grand Canyon is 65 miles north and a little west
of Flagstaff. Leaving the San Francisco Peaks and traveling north,
one descends gradually for a time away from the pines, down through
the cedars, across a barren area, then up gradually through the cedars
and into the pines which border the canyon. Much of the forest area
near the canyon is perfectly flat. The Grand Canyon group was taken
in early July 1920, at points scattered several miles along the south
rim from a little west of Grand View to the Buggeln property, which
used to be Tolfree's Hotel, at the top of the old historic Hance Trail,
a distance of 5 or 6 miles. The soil here is a thin layer of earth over
limestone. There appears to be very little surface drainage and it is
probable that the water soaks down through the limestone formation
and emerges in springs in the canyon. In the early days, Tolfree 's got
its drinking-water from artificial "tanks" or pools of standing water
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 73
formed from the melting winter snow. Mr. Patterson measured 7 of
this group of eight v-cuts by the auto-plot method in 1922. Each
tree record was later standardized, tabulated, and plotted by Mr.
Austin in a curve from 1716 to 1919. This curve is of perfect Flagstaff
type. The graphic Hann shown in figure 4 was made by Mr. F. M.
Douglass in 1926. The cycles belong to the Arizona classification, as
follows: 11.7, 14.5, 18.4, 20.8 (2), 23, and 36 (oc. ■§•).
DIXIE FOREST (UTAH) GROUP (DF)
This is a group of Swedish increment-cores collected and sent me
by Mr. William M. Mace, supervisor of the Dixie National Forest,
from the Pine Valley Mountains, in the southwestern corner of Utah.
As in the case of the Charleston Peak of southern Nevada, it seemed
desirable to find some groups intermediate in position between the
Flagstaff area and the region of the big trees of California. Mr. Mace
writes that these specimens came from the westerly side of the moun-
tains at an elevation of 8,500 feet. This would seem to correspond
in topography to group FLH, but their record, though very complacent
like FLH, resembles FL more than FLH does. The cores were received
October 1, 1923. Mr. Austin measured them by the long-plot method
in 1926. Each tree was standardized and the table and averages and
plot were also made by Mr. Austin. The curve extends from 1616 to
1922 and shows good resemblance to the Flagstaff curve. It was
smoothed by graphic Hann and is thus shown from 1750 in figure 4.
Its cycles are of the Arizona type, as follows: 19.6 (3), 27.1, and 40
(2, oc. i).
UPPER RIM GROUP (RH)
Next to the Grand Canyon, Arizona's most remarkable scenic
feature, on a large scale, is the Rim. This is the abrupt southern edge
of the great Colorado Plateau. It is an ancient fault-line; the rocks
to the north average 7,000 feet above sea-level and 1,000 to 2,000 feet
higher than those to the south, with other steep slopes below, so that
from the Rim one looks over enormous stretches of Southern Arizona
with its island mountains showing faintly in the blue haze of distance.
The edge of the Rim stretches across half of the State in a generally
uniform direction, but is wavy or zigzag in detail. So, when seen from
below, for example, from near Pine or the Natural Bridge, its sinuous
length extending easterly as far as the eye can see, could be classed
as one of the wonders of the world.
An extraordinarily large and pure pine forest covers this Rim and the
adjoining slopes, connecting on the north with the Flagstaff area and
extending on the east past the White Mountains and into New Mexico.*
♦Years ago, by kindness of Mr. F. S. Breen, then supervisor of the recently created national
forest, it was my privilege to traverse this Rim from Camp Verde to Nutrioso, close to the New
Mexican border, in a buckboard. I have no doubt that 600-mile trip from Flagstaff, lasting 26
days, helped to originate this investigation of the history recorded in tree-rings.
74 CLIMATIC CYCLES AND TREE-GROWTH
Thus the bold, pine-covered headlands of rock overlooking southern
Arizona differ in topography from the Flagstaff region, and it seemed
worth while to get a group of borings in such a locality. This was
easily done in a motor trip from Tucson to Flagstaff, on which I was
assisted by Mr. T. J. Randolph. The borings were made on August
26, 1922, two of them at 6,000 feet elevation, near the fork in the
highway between Pine and Strawberry, where the road to Flagstaff
starts up the big grade. These were numbered 91 and 92 in the Flag-
staff series and form the group RL. Two other borings were made
at the top of the Rim, where the elevation is 7,000 feet. These were
numbered 93 and 94 and constitute the present group RH. It was
intended to include all of these four in one group, but the two locations
proved so different in their effect on ring-type that it was thought
best to separate the pairs. The individuals of each pair agree finely.
Mr. Hawkins measured these four cores by auto-plot method. They
were then completely rechecked by the writer and individually stand-
ardized. The tables and curves were done by Mr. Austin. The curve
of the Upper Rim group, 1697 to 1921, smoothed by graphic Hann,
and shown in part in figure 4, is very complacent, and has only moder-
ate similarity to the typical Flagstaff curve. Its cycles, however,
keep it in the Arizona zone, for they are as follows: 14.7, 19.9 (3),
and 37 (2).
LOWER RIM GROUP (RL)
This group, as described in connection with the preceding, con-
sists of two increment-cores collected August 26, 1922, near the fork
in the road at the foot of the long Strawberry grade. The eleva-
tion is 6,000 feet. Its location is a south exposure with the great
thousand-foot wall of the Rim immediately to the north and a low,
flaMopped mesa "island" close to the south, standing up a few
hundred feet. The curve, 1770 to 1921, smoothed by a graphic Hann,
is shown in figure 4. Its striking variations resemble a shadow effect
like that in the SH group, which it minutely resembles. In fact, the
remarkable likeness between this curve and those of FLU, FV, SH, NE,
GC, and J groups puts this collection of groups in a distinctive homo-
geneous class whose locus extends at least from the Grand Canyon to the
Rim, a distance of about 150 miles. The RL cycles are 10.1, 12, 20.1
(3), 23.7, 27.6, and 38 (2, oc. -J). The absence of 14 years makes it
resemble the cycle of the Rocky Mountain zone, but as 14.4 did appear
in good form in one of the three analyses, its place in the Arizona zone
is justified.
CIBECUE GROUP (J)
The Cibecue group of five increment-borings was collected on
July 23 and 24, 1920. The area included in this group extends from
the store on Grasshopper Creek (15 miles west of Cibecue Creek store)
to the small creek about a mile east. This is some 20 miles south of
TREE RECORDS! GEOGRAPHICAL DISTRIBUTION 75
the Rim and about halfway between Pine and Fort Apache. The
elevation is under 6,000 feet. The region is reached by motor from the
White River Indian School near Fort Apache. The cores were meas-
ured by Mr. Patterson, using the auto-plot method, and fully re-
checked. The curve, 1652 to 1919, was plotted directly from the
averages and cross-identifies closely with the Flagstaff record. The
graphic Hann from 1750 on is shown in figure 4. It resembles RL
strongly. The cycles are 8.2, 9.6, 12.1, 18.5, 23.8 (3), and 30.5. There
was no sign of a 14-year cycle, and therein it resembles the Rocky
Mountain curves.
PINAL MOUNTAIN GROUP (PNL)
Surrounded by the lower levels of southern Arizona, the Pinal
Mountains form an island 90 miles from the Rim groups described
above. To reach them from that part of the Rim, one motors down
Tonto Creek and after leaving Four Peaks on the right, passes Roose-
velt Lake and Dam. Twenty-five miles beyond are the cities of
Globe and Miami, south and west of which are the Pinal Mountains.
A road goes to Tucson over each flank. To the east is the Winkelman
road ascending almost to the pine level; to the west is the Globe-
Superior Highway, a splendid bit of road engineering over a rocky and
picturesque table-land. Four borings were made September 5, 1924,
above the camp-grounds, southwest of the main peak. These cores
were measured by Mr. Swan Erickson, using the long-plot method.
Each tree of the three usable ones was standardized and the resulting
curve (see fig. 4) shows distinct resemblance to the Flagstaff curve —
more in fact than do the curves of the other island mountains. The
cycles are 7.6 (2), 10.1, 14 (oc. •£•), 23, and 27. This grouping of cycles
is classed as general, since it is rather deficient in the special charac-
teristics of each zone.
CATALINA MOUNTAIN GROUP (SC)
The Catalinas are about 60 miles a little west of south from the
Pinals. They are a large, rambling mountain mass without distinctive
top and form an emphatic northern boundary to the Tucson Valley.
The main summit, Mount Lemmon, elevation 9,150 feet, has an
inconspicuous rounded top with a fire lookout. Close on its southeast
edge is the resort, Summerhaven, with an easterly ridge extending
4 or 5 miles to Bigelow Peak and beyond. Central on this ridge is the
beautiful little valley known as Bear Wallow, with the ranger station
and Soldiers' Camp. The SC group consists of eight increment-cores
and one 350-year v-cut, all usable except one core. Their location
extends from Summerhaven to Mount Bigelow. Some are on the very
crest of the ridge and some are a hundred feet or so lower down on the
south side. The average elevation is about 7,500 feet. The contours
76 CLIMATIC CYCLES AND TREE-GROWTH
are given in some detail, because this group, while internally very-
satisfactory, is as a whole the most discordant in the entire Arizona
area, both in cross-identification of rings and in comparison between
smoothed curves. The SC specimens were measured part by auto-
plot and part by long-plot method. Individual trees were standard-
ized. The final curve, 1567 to 1919, shows a very limited resemblance
to curves in the Flagstaff area. After being smoothed by graphic
Hann, it shows many reversals of Flagstaff growth, for example, the
years near 1630, 1670, 1730, 1847, and 1880 have big growth instead of
small. The part since 1750 is given in figure 4. The cycles are 7.5,
9.2 (oc. £), 11.3, 17.4 (2), 22.9, and 34.7 (3, oc. £). The presence
of 11.3 and 17.4 gives it a resemblance to the Rocky Mountain zone
which incidentally has a number of reversals compared to Arizona.
SANTA RITA GROUP (SR)
The Santa Ritas, 9,400 feet in elevation, are 50 miles due south of
the Catalinas and form a massive mountain boundary on the east
side of the Santa Cruz Valley south of Tucson. The mountain slopes
are steep and the summit itself forms an upstanding monument of
rock 500 feet high, very striking in appearance. The pines cover the
upper parts of the mountain, but favor the north-facing canyons
where the snow lingers. Some Mexican species of pine are found here,
but they closely resemble the western yellow pine. A group of 10
borings was collected in the upper parts of White House Canyon, the
summer-resort region, on May 2, 1921, but these could not be dated,
as the doubling of rings by the pronounced summer rains made the
annual character very uncertain, a summer condition much more
pronounced here than in northern Arizona. So a second group of 6
borings was made December 22, 1921, at higher levels, that is, from
7,500 to 8,700 feet, of which all but one were usable. In this collection
I was assisted by Mr. M. S. Lankford. In a recent review it was
noted that the Santa Rita tree-records have the intensely small
Flagstaff years, 1847, 1902, 1904, and so forth, but are erratic within
the group, omissions and change of size making cross-identification
very laborious.
Each of the five trees was standardized and the resulting average
curve, 1670 to 1921, smoothed by a graphic Hann, as shown from 1750
in figure 4. It resembles both the Flagstaff and the Catalina records.
Its minute details confirm the dating of the Catalina specimens, which
were at first held in considerable doubt. The cycles are 7.5, 11.2,
14.4 (3, oc. $), 23.0 (3), and 27.4 (oc. £). This is distinctly of the
Coast type. On the whole, it will not be surprising if these southern
island mountains are influenced by some climatic situation distinctly
different from the northern Arizona plateau area.
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 77
THE ROCKY MOUNTAIN ZONE
YELLOWSTONE GROUP (Y)
This group of five increment-cores of white-barked pine (Pinus
albicaulis) was collected on August 20, 1920, at the eastern edge of the
flat top of Specimen Ridge, west of and opposite the buffalo farm, in
northeast Yellowstone Park. The trip was made from Camp Roose-
velt with the assistance of Mr. A. G. Whitney. The specimens were
cross-identified and dated in 1926. They were measured by Mr.
Austin, using the long-plot method. They were standardized and
give a record from 1693 to 1919. The curve from 1750, smoothed as
usual, and shown herewith in figure 5, does not closely resemble the
other Rocky Mountains curves, though its cycles are distinctly of that
type. They are 8.5 (3), 10.4, 12.5, 17.1 (3, oc. J), 25.6, 30.3 (oc. £).
Here we see the 17-year period which is characteristic of this eastern
zone.
LARAMIE. WYOMING, GROUP (LW)
This group of four cores, of which three only could be dated, was
collected on June 11, 1925, while motoring from Fort Collins, Colorado,
to Laramie, Wyoming. At some point not far from the State border
the road passes through a slight ravine with pine trees on the steep
slopes. The three cores afterwards used were obtained here. A few
miles farther on, a very large pine growing in a bleak flat area was
bored, but the outer rings were too small for certain dating. These
specimens were measured by Mr. Austin, using the long-plot method.
The records were each standardized and the curve, 1754 to 1924, was
smoothed by graphic Hann, which is shown in figure 5. Though its
variations are immense, it closely resembles the typical Pike's Peak
curve. Its cycles present the characteristic 17-year period with what
are probably some of its variants. The cycles are: 6.3 (2), 8.2 (3),
11.5 (oc. i), 15.9 (oc. £), 17.4, 18.2, 19.1 (oc. $), 25.0 (oc. J), and
35 (2).
CLEMENTS'S PIKE'S PEAK GROUP (C)
In 1919, Dr. F. E. Clements initiated this study of the Rocky
Mountain zone by sending me nine sections of trees from the vicinity
of the Alpine Laboratory, which is just south of the Cog Railroad
above Manitou, at an elevation of 8,700 feet. He described the
location of these trees as follows: Three yellow pines from north of
track with a south exposure, three Douglas firs from above cabins
with a northerly exposure, and three Engelmann spruce from near the
brook, with a northeasterly exposure. These were actually cut and
packed by Mr. C. W. Cherry, who later helped me at Tucson for a few
months. One of the pines was defective and could not be used, and
the remaining eight trees were averaged and plotted in a curve from
1783 to 1919. This was recently Hanned graphically, as shown in
78
CLIMATIC CYCLES AND TREE-GROWTH
1800 1850
1750 1800 1850 1900 1930
Fio. 6 — Rocky Mountain zone, smoothed group curves
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 79
figure 5, and gave as cycles: 9.3 (2), 18.8 (2, ■£■), and 34.8. So much
material was obtained subsequently from that area that this group,
with its informal treatment, has been retained as a check on the
others. Without doubt the Douglas firs could be included with the
yellow pines, but the Engelmann spruces should be kept separate.
This will appear in the Brook group of Engelmann spruce (BES) .
PIKE'S PEAK TIMBERLINE GROUP (PPT)
The first Pike's Peak group was obtained close to the Cog Road
near timberline, at an approximate elevation of 11,500 feet. Naturally,
the trees were not yellow pine. No. 1, a chip from a dead tree, had
to be discarded, but five increment-cores, two in Engelmann spruce
and three in fox- tail pine (Pinus aristata), proved good specimens.
They were readily dated and were measured by Mr. Austin by the
long-plot method. Each tree record was standardized and the curve,
1734 to 1919, was smoothed in the usual way. The portion since
1750 is given in figure 5. Its complacent character shows at once,
yet it compares exceedingly well with the smoothed curves of groups
3,000 feet lower down the mountain. The cycles are 11.7, 14.0, 20.0,
22.6 (oc. J- or -J), and 37. This group, therefore, does not classify
well as of Rocky Mountain type, but its cycles are of the general
western sort. One notes here the tendency of the double sunspot cycle
to fall a little below 23.0 years; in the Arizona area it was usually a
little above.
PIKE'S PEAK BASIN GROUP (PPB)
In making its way east after passing timberline, the Cog Road
descends sharply into and then more gradually through a basin area
to an outlet in Ruxton Creek, where the water-supply for the cities
below is taken. The more level part of the basin has an altitude of
about 9,500 feet, and here four borings were taken, of which three
(PP 7 to 9) form the basin group. Mr. Austin measured these by the
long-plot method. After standardizing, a curve, 1693 to 1919, was
drawn and smoothed by graphic Hann; figure 5 gives the part since
1750. This has much larger variations than the timberline group and
compares closely with the later groups near the Alpine Laboratory.
The unusual feature in this group is the doubling of average growth
after 1865. The cycles are 10.2 (2), 13.0 (oc. |), 20.0 (3, £), 25.6,
and 30.7 (2, oc. ^ or £). The absence of a 17-year cycle is not
usual in this zone, but the presence of 25- and 30-year cycles is very
characteristic.
UPPER NORTH TRANSECT GROUP (HNT)
The Alpine Laboratory has an elevation of about 8,700 feet, and
near it are varying contours well worth testing. The various Pike's
Peak groups, including those already described, were originally
selected as a study in topography. After leaving the basin the Cog
80 CLIMATIC CYCLES AND TREE-GROWTH
Road descends sharply, following the bed of Ruxton Creek. The
laboratory is situated on a small southern tributary, Jack Creek,
just above their confluence. Dr. Clements has made extended ecologi-
cal studies on a certain area, the Transect, which extends a half mile
up the high, wooded slopes to the north and perhaps a third of a mile
up the shorter and more barren slopes to the south. The north branch
of this transect has very steep slopes in the lower part near this creek
and the Cog Road, and gentler slopes above. So the collections there
were divided into upper and lower groups. The upper group, PP
11 to 20, has an average altitude of over 9,000 feet and includes 5 yellow
pines, 3 Douglas firs, and 2 limber pines. These 10 cores were meas-
ured by Mr. Austin, using the long-plot method. They were stand-
ardized, and the curve, 1655 to 1919, was smoothed as usual, and the
part since 1750 is shown in figure 5. It resembles the neighboring
groups very closely indeed. Its cycles are 6.8 (2), 8.6 (2), 9.3, 13,
17.2, 22.6 (2), and 34.5 (2, oc. £).
LOWER NORTH TRANSECT GROUP (LNT)
The lower group, PP 21 to 27, in the North Transect, was 250 feet
below the upper, estimated in vertical height, which makes it about
8,800 feet above sea-level. Mr. Austin measured these cores also by
the long-plot method, and the curve, 1644 to 1919, smoothed after
standardizing, is shown (after 1750) in figure 5. The result shows a
rather even curve, more complacent than the trees farther from the
brook. It compares closely with the other group curves. Its cycles
are 11.1 (2), 16.0, 20.4 (2), 21.3 (oc. -£), and 40, which approximate
but are not exact in their conformity to the Rocky Mountain cycles.
SOUTH TRANSECT GROUP (ST)
South of the Alpine Laboratory the slopes rise abruptly up to
some very barren sand areas on Baseball Ridge. A collection of 10
increment-borings was made here with the help of Dr. Gorm Loftfield
at an average level perhaps of 8,900 feet. Two of these are yellow
pine, 6 are Douglas fir, and 2 are limber pine {Pinus flexilis) . They
cross-identified well and were measured by Mr. Austin and stand-
ardized. The curve 1570 to 1919 was smoothed as usual and the result
(since 1750) is given in figure 5. It shows vigorous variations which
make it probably the best representative curve of this Pike's Peak
area. Its cycles also are entirely typical of the Rocky Mountain
zone; 9.8 (2), 17.2 (2), 19.7 (3, oc. \), 25.2 (2), 31.1, and 34 (oc. $).
BROOK GROUP OF DOUGLAS FIR (BDF)
Ten trees were tested along Ruxton Creek near the Alpine Lab-
oratory, with the purpose of forming a brook group and of learning
whether the Engelmann spruce reacts to abundant ground-water in the
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 81
same way as the yellow pine and Douglas fir. While dating the records,
it was evident that the Engelmann spruce was giving a different
story and could not be joined with the firs and pines. So the brook
trees are separated into two groups, of which this one is made up of
4 firs and 2 yellow pines. One of these firs, PP-35, carries a dendro-
graph designed by Dr. D. T. MacDougal. The two yellow pines are
only a few feet away, and these three trees are sometimes referred to
as the dendrograph group; but they are themselves close to the brook
and their records agree well with the other Douglas firs near by, so
they make up part of this group. These six cores were measured by
Mr. Austin, using the long-plot method, and after standardizing gave
a curve from 1782 to 1919, which was smoothed in the usual way and
is shown in figure 5. This closely agrees with the other adjacent
groups already described, and with them (PPB, HNT, LNT, ST, and
C) forms a collection of homogeneous groups which must represent
this region exceedingly well. The cycles of the Douglas fir brook
group are 7.5, 9.5 (2), 11.4 (oc. £), 14.3 (oc. £), 20-4 (2)> 22-5 (2,
oc. ■£), and 39, a good Rocky Mountain set.
BROOK GROUP OF ENGELMANN SPRUCE (BES)
Engelmann spruce growth on the San Francisco Peaks in Arizona
had been too complacent for use in climatic study, but on Pike's Peak
four trees, PP 28 to 31, along Ruxton Brook, showed attractive
variations and even exhibited weak signs of cross-identification
among themselves. But when the curves were drawn, it was seen
that their growth does not match the growth of the other brook
species. The cores were measured by Mr. Austin by the long-plot
method and standardizing lines marked on each individual tree-curve
by the writer, as always. The resulting smoothed curve, from 1775
to 1919, shown in figure 5, presents marked variations, departing
greatly from the typical Pike's Peak curve. Its cycles are 8.9 (2),
12.2 (2), 14.1 (2), 17.6 (£), 24.7 (oc. £), and 34 (oc. •£). The 17-
year cycle is characteristic of the Rocky Mountains, but the presence
of a 14-year cycle and a probable sunspot cycle make this set resemble
the cycles of the Coast zone.
CLOUDCROFT. NEW MEXICO. GROUP (CC)
Any real representation of the Southwest would be incomplete
without specimens from New Mexico's summer resort, Cloudcroft, in
the Lincoln National Forest. Accordingly, six good v-cuts from pine
stumps were sent me by Mr. Dan Felts, forest ranger there. Three
only could be used, and these, as Mr. Felts writes, come from the
northwest quarter of the southeast quarter of section 23, township
16 South, range 11 east, New Mexico prime meridian. This is the
extreme upper end of Nelson Canyon watershed, half a mile west and
82 CLIMATIC CYCLES AND TREE-GROWTH
southwest of Russia, New Mexico. Mr. C. W. Cherry measured
these specimens by auto-plot method. They were approximately
standardized by assigning added weight to the slower-growing trees
in forming the averages. The resulting curve from 1736 to 1920,
smoothed by a careful geometric Harm and mostly shown in figure 5,
presents strong variations which have much in common with the
Pike's Peak curves. The cycles are 11.2 (oc. £), 13-4, 15.3 (2), 17.8,
22.1 (i or i), 27.5 (i), and 36 (i).
SANTA FE GROUP (SF)
This group was collected on September 5, 1922, with the aid of Mr.
B. Z. McCullough, who took me some 4 or 5 miles up the canyon
east of Santa Fe, New Mexico. The trees selected had usually a
north exposure and were in the general vicinity of the ranger station.
They were chosen at considerable height above the brook, so as not
to be influenced by it. All of the six cores were readily dated by
resemblance to the Flagstaff series. Mr. C. W. Cherry measured
these rings by the auto-plot method. After standardizing, he plotted
their average in a curve from 1749 to 1921 and smoothed it by a careful
geometric Hann. The result given in figure 5 shows excellent varia-
tions with distinct apparent similarity to curves of the Flagstaff area,
but the cycles conform more to the Rocky Mountain zone, being
10.2, 11.9, 18.4 (2), 22.4, 27.5, and 35 (2, oc. $). The absence of a
14-year period places it with the Rocky Mountain groups, although
the absence of the 17-year period is unusual in that zone.
BASIN MOUNTAIN UPPER GROUP (BMH)
The collection of this and the two following groups is due to the
cooperation of the archaeologists. In August 1919 I visited the Aztec
ruins, New Mexico; thence Mr. Morris took me to Sullivan's saw-
mill on Basin Mountain, in Colorado, nearly 40 miles north of Aztec
and perhaps 15 southwest of Durango. The mountain has a per-
fectly flat top about a mile across, covered with pines. The saw-mill
is 2 or 3 miles away, in the basin to the east. The pine trees extend
down to the mill and a few scattered ones are found even lower
down. Two v-cuts were taken from logs at the mill; five more were
cut from stumps on the mountain-top before it got dark, and on the
way down we cut the three which made the lower group, of which
the last was cut by the light of matches long after nightfall. This
division into upper and lower groups was made on account of varying
water-supply in the soil. The date was August 13, 1919. Mr. J. F.
Freeman measured all these specimens by the standard cathetometer
method and the seven from the mountain- top have been combined
without standardizing to form a curve beginning 1588 and ending
1919, which cross-identifies minutely with the Flagstaff tree-growth.
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 83
This curve, smoothed and shown in part in figure 5, distinctly re-
sembles the Flagstaff curves in position of the more prominent maxima,
but its cycles, 8.5, 16.8, and 35 (2), are characteristic of the Rocky
Mountain zone.
BASIN MOUNTAIN LOWER GROUP (BML)
The three v-cuts in this group were collected August 13, 1919, as
has been described in the preceding paragraph. Their actual loca-
tion was on the upper easterly slopes of Basin Mountain, some 500
feet vertically below the top. Thus climatically they are in the same
situation as the others, but with regard to soil moisture they are very
different, for they catch a local drainage. In fact, the lowest of the
three, No. H-29, had large complacent rings and could not be used.
The two remaining ones average 50 per cent larger growth than the
upper group. Mr. Freeman measured these with the cathetometer.
The curve, not standardized, begins at 1700 and ends 1918. The
smoothed curve from 1750 is shown in figure 5. The cycles are 10.5,
11.6, 13.4, 20.4 (oc. i), 22.7 (3), and 37, which resemble the Coast
cycles.
AZTEC EAST GROUP (AE)
On inquiry, Mr. E. H. Morris found that there were Douglas
fir trees nearer Aztec than the pines of Basin Mountain, namely, at a
point some 20 miles east. Accordingly, early in 1920 he secured four
specimens from there, H 39 to 42, which form this group. They showed
severe drought effects in several places, which made the dating of the
central parts uncertain, and accordingly later in the same year he
sent me five more, H 65 to 69, which gave entire certainty to the
dating. The earlier four were then measured by Mr. Freeman with a
micrometer slide, and the curve, 1662 to 1919, drawn without standard-
izing (as was the case with several of the early curves) and smoothed,
is «hown in part in figure 5. As with the others from this region, it
resembles the Flagstaff curves. Its cycles are 8.1, 12.4, 19.5, 24.0 (3),
and 34.2 (oc. ^-), which resemble both the Flagstaff and the Rocky
Mountain cycles. A later curve, using all these "Modern H" trees,
gives cycles as follows: 8.2, 13.7, 18.8, 20±, 23.8, and 36.
THE COAST ZONE
BOISE, IDAHO, GROUP (BI)
This group is a set of 10 increment-cores sent by the forest super-
visor of the Boise National Forest, in July 1923. They came from
the southwestern parts of the forested mountains, some 50 miles
northwest of the city. The growth is complacent, but the cross-
identification of all 10 is good. Two of the trees cross-identify with
some of the trees from Klamath Falls, in southern Oregon. These
84
CLIMATIC CYCLES AND TREE-GROWTH
rings were measured by Mr. Austin, using the long-plot method,
and represented dates from 1652 to 1922. The smoothed curve,
1800 1850
Fig. 6 — Coast zone, smoothed group curves
shown in part in figure 6 herewith, when taken in its entire length, and
especially when reduced to 3 specimens showing more variation, though
complacent for short cycles, evidently has a long period of the order
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 85
of 40 years. The cycles are 6.4, 11.6 (3, oc. £), 17.2 (oc. £ or J), 23.0
(oc. \ or -J-), and 36. This strong emphasis on the single sunspot
cycle, especially in the higher latitudes, is very characteristic of the
Coast cycles.
BAKER, OREGON. GROUP (BO)
The higher parts of the pass between Baker, Oregon, and the
Columbia River are pine-covered, and at distances from Baker vary-
ing between 60 and 90 miles 8 increment-cores were obtained.
These are complacent, and the dating, though probably right, has
not the certainty of the Arizona and Rocky Mountain pines. One
core had to be omitted because it was erratic, probably from injury.
There was some cross-identification with the Boise and the Klamath
Falls groups. The rings were measured by Mr. Austin, using the long-
plot method. The records were standardized and a curve produced
extending from 1660 to 1924. This was smoothed by the usual graphic
Hann and is shown in part in figure 6. It is a trifle less complacent
than the Boise group and, like it, tends to show a long period of the
order of 40 years. The cycles are 6.8, 9.1, 11.3 (2, oc. £), 15.0, 21.8
(2, oc. %), and 28.4 (oc. -J). These have some of the Rocky Mountain
characteristics.
DALLES GROUP (DL)
The most beautiful part of the Columbia River Highway passes
through the mountain range between Portland and The Dalles. On
the west side of this range the rainfall is heavy and the vegetation
profuse; the east side of the mountains is dry, looking out onto the
arid areas of central Oregon. A narrow belt of yellow pine runs north
and south along this eastern slope. This small group of three incre-
ment-cores came, therefore, from a point 8 miles west of the rapids in
the river which gave the name, several hundred feet above the river
on its very steep south side. The dating between these three trees
was very satisfactory. The rings were measured by Mr. Austin, and
the standardized curve from 1765 to 1924 was smoothed in the usual
way and is shown in figure 6. This curve has a trace of similarity
to those at Baker and Boise, especially in respect to the apparent long
period and its phases, but its real conformity is with the California
curves to the south. This group shows a profound depression from
1890 to 1894, which suggests fire or injury of some sort. The cycles
are 7.2 (2), 12.6, 14.2 (3, oc. -*-), 16.4 (2), 18.3, 22.5, and 35.
OREGON COAST GROUP (OC)
This is the group of Douglas fir described in Volume I, which
came from the low coast hills 25 miles northwest of Portland, where
the rainfall is large and the snows of winter very rare. No real like-
ness in rings or in smoothed curve (graphic Hann) has been found here
to the groups farther inland. The smoothed curve is shown in figure 6.
86 CLIMATIC CYCLES AND TREE-GROWTH
The cycles are 6.8, 10.2 (2), 14.0 (3), 20.3 (oc. £ or £), 22.6 (2, oc. $),
and 28.3 (oc. •£). This is of mixed type and does not readily match
any one of the three zones. Its 14- and 20-year cycles remind one of
Arizona, but the 10-year cycle is strongly Rocky Mountain and the
one close to 23 years is most common on the Coast. There is prob-
ably some relation between this set of cycles and its position close
to the coast.
KLAMATH FALLS GROUP (KF)
This group of 12 increment-cores was received May 12, 1924,
through the kindness of Mr. H. B. Rankin, supervisor of the Crater
National Forest, near Klamath Falls, Oregon. They had been secured
in that forest at an elevation of 5,100 feet above the sea. They cross-
identified perfectly, and a few of them show likeness to some of the
trees in the Boise and Baker groups. Mr. Austin measured all the
specimens, using the long-plot method, and after standardizing, the
curve was smoothed by graphic Hann and is given in figure 6. It
presents no marked similarity to any other, though the Boise and
Baker groups have real touches of likeness. Yet all the while its inter-
nal cross-identification was perfect and its smoothed-curve variations
look entirely normal. Its cycles are 8.5, 9.6, 14.0, 15.5 (oc. -1), 19.5
(oc. •£-), 24.2 (2, oc. •£), and 31.2 (2). This is a mixed set, but perhaps
has a little more resemblance to the Arizona area than to the others.
A very fine 500-year pine record was sent me on July 23, 1925. The
tree had been cut by the Pelican Bay Lumber Company in the same
forest on the southwest quarter of section 35, township 29 south,
range 61 east, W. M., at 5,100 feet elevation and about 5 per cent
east slope. This tree does not readily cross-identify with the 12 cores,
and as it comes from a different place and is very old, it is reserved for
future discussion.
PLUMAS COUNTY GROUP (CP»)
This group of 10 increment-cores from Meadow Valley was sent
me by Professor Emanuel Fritz, of the agricultural experiment station,
Berkeley, California. He says:
" Meadow Valley is eight miles west of Quincy, and the borings
were collected in Township 24 North, Range 8 East. The region is
very mountainous, but Meadow Valley is an ancient lake bed. The
borings came from the southern border of the valley on a slope, less
than 100 feet above the valley floor, elevation 4,000 feet. The water-
supply is excellent and the soil is very rich in humus and carries con-
siderable moisture. The forest growth is comparatively luxuriant.
All the borings were taken in August, 1922."
They cross-identified well and were measured by Mr. Cherry,
using the auto-plot method. They were standardized and smoothed
♦"California pines," the first group of that species secured from California.
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 87
by graphic Hann. The curve extends from 1551 to 1921 and the part
since 1750 is shown in figure 6. It has a distinct similarity to the
typical Sierra Nevada curve farther south. Its cycles are 6.7, 11.8,
13.7 (oc. -J), and 28.6 (3), which conforms to the usual ones of the
Coast zone.
Professor Fritz also sent a partial section of pine tree from a point
at about 5,400 feet altitude in Lassen County, near Susanville. This
single tree-record begins at 1588 and ends in 1922. An analysis
obtained in the usual way gives as cycles, 16.4 (2, oc. -£), 20.2 (oc. -J-),
24.2 (oc. i), and 29.5.
CALAVERAS GROUP OF PINES (CVP)
The collection of this group of increment-cores at the edges of the
Calaveras Grove of big trees on July 4, 1924, has been described in a
previous chapter, page 53. The additional cores, taken near Murpheys,
showed a larger growth average of 1.71 mm. as compared to 1.25 of the
trees near the grove, but otherwise appeared to give much the same
record, and all were included in one group of 14.
Mr. Hawkins measured these, using the long-plot method. An
attempt was made in this group to standardize the individual records
by using different gear ratios on the plotting instrument, but it was
not felt to be entirely satisfactory, on account of the different average
size of different parts of a single record; for instance, the larger central
growth in early years of the tree can not be properly allowed for, and
yet it is usually too good to discard. The average was undoubtedly
improved by this change of gears, and there were so many trees in the
group that it did not seem necessary to do any further standardizing.
The mean of the 14 trees, 1621 to 1923, smoothed by a graphic Hann,
is shown in large part (1750 to 1923) in figure 6. It is at once evident
that this belongs to the inner collection of homogeneous Sierra Nevada
curves. The cycles in this curve are 6.8 (2), 7.6 (2), 10.4, 14.6 (oc. £),
21.2 (2), and 30.2, which are of the Arizona type.
BIG CREEK GROUP (BC)
After the sequoia trip of 1919, it was realized that no pine records
had been secured in California to aid in the cross-dating between
Arizona and California. Accordingly, in 1920, at the request of Mr.
Paul Redington, district forester at San Francisco, the ranger on Big
Creek very kindly sent me five excellent v-cuts from pine stumps at
an elevation of about 5,500 feet on Big Creek, a northern tributary of
King's River. This river is just north of the General Grant National
Park and the large areas from which the greater part of the sequoia
records had come.
These pine specimens cross-identified among themselves exceed-
ingly well, and there was no trouble in recognizing a number of Flag-
7
88 CLIMATIC CYCLES AND TREE-GROWTH
staff dates in their rings. The average growth was nearly 50 per cent
larger than the Flagstaff growth and many rings were immense.
The specimens were measured by Mr. Cherry, using the auto-plot
method. They were individually standardized by him and the result-
ing curve from 1719 to 1919, smoothed by geometric Hann, is shown in
part in figure 6. It agrees exceedingly well with the Sierra Nevada
collection, which extends from Calaveras Grove to Mount Wilson.
The cycles are 8.4, 11.2 (oc. %), 13.5, 17.4, 21.7 (3), and 35 (oc. J),
which classify as of Coast type.
SPRINGVILLE GROUP OF PINES (EP»)
The visit to Springville in early August 1925, and the collection
of sequoia records, has already been described on page 54. The 10
pine borings came from elevations between 5,000 and 6,000 feet, that
is, from Camp Lookout to the lower edge of the sequoias, about 4
miles away. Most of the pines had a local south exposure toward a
canyon sloping toward the west. Some of these trees were on isolated
points, where they could get no possible water except the rain or snow
which fell immediately about them. Two could not be used; one was a
magnificent 5-foot tree whose growth was too small to allow dating
in the core and whose age therefore is probably very great; the other
had an extensive fire injury and the rings were too erratic. Mr. Austin
measured this group, using the long-plot method. The trees were
standardized individually and the curve, 1720 to 1924, smoothed by
graphic Hann, is shown (since 1750) in figure 6. It shows excellent
variations agreeing most satisfactorily with the other Sierra Nevada
curves between Calaveras and Mount Wilson. It is interesting to
recall that the sequoias from Calaveras to Springville which show uni-
form cross-identification, to a considerable extent cross-identify with
the pines nearby. The cycles classify in the Coast type as follows:
8.7, 11.4, 13.4 (2), 17.4 (oc. £), 23.1, 27.6 (2, oc. £), and 34 (oc. £).
MOUNT WILSON GROUP (W)
This group of 22 increment-borings, of which 8 are used, was made
July 25, 1925, by courtesy of the Toll Roads Company and the Mount
Wilson Solar Observatory, who gave permission to bore the trees.
The top of the mountain, about 6,000 feet elevation, is a rough semi-
circle of ridge, convex toward the west and south, with the inner area
in the form of an amphitheater of gentle slope toward the central
drainage wash, which flows down past Strain's Camp. Sixteen trees
were tested in this area, of which 8 are used, all yellow pines except
one sugar pine and one Douglas fir, each of which gives apparently
the same record as the yellow pines. The 6 Douglas firs tested on the
road down the mountain were defective, perhaps in part injured by
the road building.
♦Elster's pines.
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 89
The trees which could be used were in the triangle between the
hotel, the Observatory museum, and Strain's Camp. One of the very
best, No. 14, is a large tree in the fork of the gulch just above Strain's
Camp, close to the upper hall. The ring record of this tree shows
strong Flagstaff characteristics. This group was measured by Mr.
Erickson, using the long-plot method. The records were standardized
and a curve, 1725 to 1924, smoothed by graphic Hann, is mostly
shown in figure 6. This curve has strong variations agreeing excel-
lently with the Sierra Nevada curves. The cycles are 7.7, 10.4 (2),
11.2 (oc. i), 15.2 (oc. $), 17.1, 22.5 (2, oc. £ or £), 29.4, and 34 (2, oc.
•J- or J-). These conform to the Coast type.
SAN BERNARDINO GROUP (SB)
The Forest Service in Los Angeles was kind enough to send me in
1922 some 13 increment-cores from the San Bernardino Mountains.
Mr. Patterson measured the rings, using the auto-plot method. Five
were omitted because they were too short; 2 were reserved because
they did not agree well with the others, which formed a real group, and
because there was a slight doubt of the dating before 1850; of these
one shows an unusually regular 17-year cycle. The remaining 6 were
combined into the present group. They were standardized and the
curve, 1819 to 1921, smoothed by graphic Hann, is shown in figure 6.
The very remarkable 23-year period is the most obvious thing in it.
In fact, a search for older trees in that region might give some very
interesting and valuable material. This periodic feature stands out
because certain maxima which show well in the Sierra Nevadas to
the north are here largely suppressed. The maxima which make this
curve interesting are all present in the Sierra Nevada curves. The
cycles here are 7.7, 9.8 (2), and 22.9 (4), the only case of assigning a
weight of 4 to any cycle. These belong to the Coast zone.
CHARLESTON MOUNTAIN GROUP (CH)
The collection of this group of seven cores and one 500-year v-cut
on July 18, 1924, has already been described on page 61. Saw Mill
Canyon starts just north of the main peak and cuts to the east. The
site of these trees is about 7,500 feet elevation and has something like
24 inches of rain. The canyon is narrow and composed largely of
gravel terraces. Three trees high up on the very steep terrace bank
to the south showed such slow growth that much of their records could
not be dated, but the other specimens from the flat canyon bottom
gave a fine agreement. The wash was dry. The 500-year stump was
close to its north edge. The rings readily cross-identify both with
Flagstaff trees and also with Sierra Nevada trees, thus corresponding
to the intermediate geographical location. Mr. Hawkins measured
them by the long-plot method, effecting partial standardizing by dif-
90 CLIMATIC CYCLES AND TREE-GROWTH
ferent gears in the measuring instrument. However, each tree-record
was subsequently standardized in the usual way and the resulting
curve, 1402 to 1923, was smoothed by graphic Hann. The part since
1750 is shown in figure 6. This curve is strongly of the Flagstaff type
in the last century or so, except that 1818 to 1821 have large growth
instead of small. The cycles are 7.3, 11.4, 14.4 (oc. £), 17.8 (3), 21.3,
25.9, 29.0, and 34. This is a Coast type.
PINE VALLEY GROUP (PV)
The Pine Valley here referred to is in the mountains some 50 miles
east of San Diego, California, at an elevation of over 5,000 feet.
The trees are more numerous at the southern end of the 2-mile valley,
and of five increment-cores, three come from the vicinity of the
summer resort there; one which could not be dated comes from the
northern end and one comes from a very large tree about midway.
Four were secured in the summer of 1923 and the undated one in
August 1925. The rings cross-identify readily with those at Flagstaff.
Mr. Hawkins measured the rings, using the auto-plot method. Stand-
ardizing was effected by reducing mathematically each tree-record to a
set of departures from its own mean. The resulting curve, 1736 to
1923, smoothed as usual, is given in part in figure 6. This curve
matches the Charleston group with great exactness and therefore is
closely like the Flagstaff-type curve. The cycles are 6.6, 10.1, 14.4,
18.4, 25.2 (oc. ^ or -J-), 32 (2, oc. £), and 35, which rather resemble
the Arizona cycles.
MISCELLANEOUS GROUPS
The groups mentioned below have been collected for various pur-
poses, but for one reason or another do not lend themselves to the
study of cycle distribution. They are added here because reference
has been or will be made to them.
SEQUOIAS
Calaveras group (CVS) — This group consists of two increments-
cores, three v-cuts on fallen trees collected in 1924, and a tracing
(recently measured and plotted by Mr. Austin) made by Mr. Manson
in the 1880 's. This was copied from an original tracing, which, with
a separate copy, was filed in the library of the University of Cali-
fornia. A copy was loaned to me by the Department of Agriculture
of the University of California, and another was sent me by Professor
C. F. Marvin, chief of the United States Weather Bureau. This
"longitudinal" record is probably from the Dance Hall tree; it goes
back to 621 a. d. The specimen which I collected from the "Old
Maid" goes back to 525 a. d. My record from the "Father of the
Forest" begins at 922 a. d.
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 91
Grant Park sequoias (GPS) --This group includes the 21 v-cuts
made in 1915 and 1918 in the vicinity of the General Grant National
Park. They are described in Volume I.
Topography sequoias (TS) — These are 12 small and usually
incomplete radials collected in 1919 from the Grant Park region,
giving the last 500 years of sequoia growth and selected with respect
to topographic contours, ground-water, and so forth, to get the effect
of these features on the size of rings.
Springville sequoias (SS) — These include two numbers, 22 and 23,
collected in 1918, and 14 radials secured in 1925 from medium and
very old trees at the old Enterprise mill-site some 20 miles east of
Springville, California. These will be used especially in the formation
of early tree-records and the attempt to date the prehistoric ruins of
the Southwest.
COAST REDWOODS
Santa Cruz group (Z) — These are eight radial pieces of coast red-
wood collected February 20, 1921, some 15 miles north of Santa Cruz,
California. These could not be cross-identified and so are not dated.
Scotia group (B) — These are 12 fine radials collected in early July
1925, at Percy J. Brown's lumber-mill, a few miles south of Scotia,
California. These, too, did not cross-identify and have never been
dated.
ARIZONA GROUPS
Flagstaff century group (FLC) — This includes 10 pines 500 years
old, of which one extends back 640 years, all in the vicinity of Flag-
staff. These will form the approach to the study of early pine records
in the Southwest, which will include many semihistoric beam sections
from the Hopi villages, and it is hoped from the prehistoric ruins also.
Flagstaff lava-beds (FLB) — These lava-beds are 16 miles northeast
of town. Only two trees belong in this group, FL 48, inside the ring
of lava, from which a 1-inch core was taken in 1920, and FL 51, just
outside the lava ring, a v-cut from the stump. The former goes back
to 1556 and the latter to 1598.
Prescott group (PR) — Nos. 1 to 70 were small incomplete v-cuts
sent me by the Forest Service in 1911, described in Volume I. Nos.
71 to 75 are increment-borings made in 1924 to bring the Prescott
rain comparison up to date. The records were not intended to go back
before 1850, but some of them do.
OTHER WESTERN GROUPS
Pecos, New Mexico (L) — These are four radials from the forest
near Pecos, New Mexico, sent by the Forest Service in 1920. They
were needed for comparison with the prehistoric beams sent by Dr. A.
92
CLIMATIC CYCLES AND TREE-GROWTH
V. Kidder, who has been conducting excavations in the ancient ruins
there. The rings in these specimens are rather erratic and only one
gave a reliable record back to about 1720.
Raton, New Mexico (R) — This is a collection of three increment-
borings secured near the highway over Raton Pass. Only one proved
datable.
Nebraska (NEB) — This is a group of 12 sections from young
trees sent by Mr. Jay Higgins, forest supervisor, at the request of Dr.
F. E. Clements, from the plantations on the Nebraska Forest and from
the native yellow-pine stands near the Niobrara Division of the forest.
The three yellow-pine specimens all cross-identify nicely and give a
record extending back to the middle 1880 's. The jack pines, except
one, are also reliable in dating and extend back to about 1907. The
three Scotch pines extend back to about 1913, but do not cross-identify
in a way to give confidence.
In the study of western cycles a group from Nebraska would be
very valuable, but it should go back 100 years at the least for proper
comparison with the other western groups. The above specimens,
however, will be most useful in climatic comparisons.
Wind River, Washington (WR) — This group was collected June
20, 1925, at the Wind River Forest Experiment Station, Washington,
a most favorable location on a tributary of the Columbia River, per-
haps 75 miles from Portland. Five increment-borings were obtained,
one yellow pine and the rest Douglas fir. Most of these were erratic in
growth, perhaps from injuries, and one, at least, was too much crushed
in boring. So the group was not used in the special study of western
cvcles.
NORTH AMERICAN GROUPS
American Arctic (AA) — These 21 sections, chiefly white pine and
fir, came from high latitudes in the MacKenzie River area of northern
Canada, by courtesy of Hon. Chas. Camsell and Mr. G. S. Hume,
Department of Mines, Ottawa, at the request of Mr. V. Stefansson,
the explorer. They were mostly cut in 1923. The interesting and
gratifying fact is that they can be cross-identified for the most part
and dated. The growth is usually very small and sometimes erratic.
The 21 specimens are divided into three subgroups, as follows:
Subgroup
Average
age
Average
ring-size
Average
diameter
A. Nos. 1 to 6, lat. 60° N., South River group
years
57
85
100
inch
0.034
.015
.020
inches
4.08
2.29
3.94
B. Nos. 7 to 15, lat. 65.5° N., Lake group (Great Bear Lake)
C. Nos. 16 to 21, lat. 66.5° N., North River group
Total, Nos. 1 to 21
80
.022
3.3
TREE RECORDS: GEOGRAPHICAL DISTRIBUTION 93
These have been dated, but not yet measured. Considerable
parts of all except one can be used, but there is a tendency to show
very small compressed growth in the early years. No. 8, the excep-
tion, goes back to the neighborhood of 1700, but is too uncertain to
use. No. 19 extends to about 1743, but can only be used after 1890.
No. 10, beginning about 1792, can probably be measured. A fair
record from 1800 will come from the Great Bear Lake region. The
South River group extends to about 1835 and the North River group
to 1860, with a single one to 1808. This valuable collection will be
of the greatest help when the cycles over larger areas are studied.
East Wareham, Massachusetts (EW) — This group consists of
some 21 v-cuts and increment-cores secured largely in 1921, from the
region between Wareham and Sagamore Beach. The cross-identifica-
tion is good in most of them, but injuries have affected a number and
many are too short and only 8 are held as worth measuring. These
will carry a good record to 1840 and a single one to about 1795. This
last is from the "lone pine" which used to stand in the lane about
half a mile southeast of the Onset Junction railroad station.
Mount Washington group — Two sections of very old black spruce
trees from near timberline on Mount Washington have been kindly
sent by Professor W. C. O'Kane, of the University of New Hampshire.
These grew at about 4,000 feet elevation, were badly deformed, and
were some 3 or 4 inches in diameter and about 275 years old. This is
the nucleus of a valuable group.
Mount Desert, Maine — Three increment-cores were sent me in 1921.
NW. Pennsylvania group (PA) — This group of 10 v-cuts and 1
increment-core, 10 white pines and 1 beech, was collected May 20,
1922, from the logging camps of the Wheeler Lumber Company, by
kindness of the manager, Mr. N. P. Wheeler, jr., in the higher parts
of the mountains halfway between Pittsburgh, Pennsylvania, and
Buffalo, New York. These cross-identify well and give a record
extending back to about 1650. The beech shows favorable ring
variation and gives promise of being a useful tree in such studies as
t nPSP
FOREIGN GROUPS
Brazil (BZ) — Two 6-foot sections of the South American pine
from southern Brazil were measured by the auto-plot method in the
Commercial Museum in Philadelphia. They had been cut about 1902
and were each close to 500 years old. They did not cross-identify,
though the rings seemed clear and practically without error.
Tasmania (TS) — A section of King William's pine (Athrataxis
selaginoides Don) from 3,000 feet elevation in the highlands of Tas-
mania, has been sent me by Mr. G. Weindorfer. It gives great promise
of valuable cycle studies in the southern hemisphere.
VIII. ENVIRONMENT
This chapter deals with the effects of climate, topography, and
other external agencies on ring-growth in trees; after which the point
of view is reversed and the observed effects are listed as indicators of
past climates.
EFFECTS IN TREES
CLIMATE
The common factor over large areas is climate. A heavy winter
snowfall in Northern Arizona, which supplies abundant moisture for
the trees there, extends over hundreds of miles and supplies abundant
moisture in northwestern New Mexico, 225 miles away, or over on the
coast mountains, a matter of 400 miles in the opposite direction. A
dry winter in Flagstaff is usually dry in the other places also. Even
at much greater distances the resemblances are enough to enable us
to carry dates across in the trees.
Rings a climatic phenomenon — This is not surprising, for the ring
is a climatic phenomenon. It begins with large, white rapid growth
in the late spring when the sap flows. The usual time of this at Flag-
staff (elevation 7,000 feet) is in late May or June and is well observed
by the dendrograph, which magnifies the diameter of the trunk and
shows its daily and hourly variations. In this arid climate, spring
growth depends on the precipitation of the preceding winter, for the
months of April, May, and June are exceedingly dry. In July and
August come the heavy summer rains with a large run-off and little
benefit to the trees. When the season closes, there is a gradual cessa-
tion of the activity of the tree, owing to lowered temperature and
diminished water-supply. This causes the deposition of harder
material in the cell-walls, producing in the pine the dark, hard autumn
part of the ring and the protecting bark. The growth stops altogether
in winter.
Small single rings — If the winter and spring have been unusually
dry, the Arizona tree may stop growing by summer. The resulting
ring will consist of a small white spring growth and a threadlike red
outside growth. In old trees the ring may become microscopic or
appear as a thickening of the red ring of the preceding autumn, and
even disappear altogether in parts of the circuit of the trunk. In
some extreme cases, sections could be found in which a ring or two
is absent from the entire circuit. Very likely it was active for a time
but not long enough to leave white cells.
Double rings — On the other hand, if the winter precipitation has
been normal, the tree passes through the spring drought and reacts
94
ENVIRONMENT 95
to the summer rains and displays additional growth. As a rule, near
Flagstaff this late growth is very much less in width than the spring
growth, usually between 10 and 20 per cent, rarely going to 30 per
cent. When it is more than 15 per cent, it begins often to show a
double effect, with its central part lighter than the red on each side.
In extreme cases this autumn growth actually gets back to the color of
spring wood and the growth becomes nearly white, thus separating
off an extra red ring that is rarely hard to distinguish from the annual
autumn red ring. The distinctive feature is that the false ring fades
gradually on both sides, while the true autumn ring fades gradually
on the inside but ends abruptly on the outside.
Doubling and locality — The trees near Prescott show an extra-
ordinary number of extra rings, usually easily distinguished by the
criterion just mentioned. Some trees there have extra rings unusually
small and sharp and separated by very white tissue. Such rings are
more difficult to recognize. Sometimes there was more than one
false ring. In such cases it is evident that the storm is very important
to the tree. At that elevation, 5,200 feet, the rainfall is much less
than at Flagstaff, and each rainy season is more nearly a series of
isolated storms.
The soil on which these Prescott rings grew is a disintegrated
granite which forms a very efficient reservoir, holding abundant
water with little leakage. The top of Mount Wilson is very similar
in type of soil, though not in climate, for it has a single rainy season in
winter. Double rings are practically unknown there. At the lower
levels of the Santa Rita Mountains near Tucson the soil and also the
climatic conditions are again similar to those at Prescott. The trees
there depend on summer rains even more than at the northern moun-
tains and the doubling character is more conspicuous and bothersome.
Thus it is seen that doubling is a local climatic effect.
Doubling and age — Doubling is far more conspicuous in the earlier
or "youth" rings of a tree when the trunk is rapidly increasing in
size. These youth-rings are larger and less sensitive than the later
rings. Of course, it is more apparent in large rings, and any tree which
grows rapidly is more likely to show it. However, without specially
investigating the point, one is inclined to think that young trees,
being less sensitive than mature ones, are a little more certain to
continue their growth into autumn and so do have more doubling
than mature trees. This could be tested by the dendrograph on
properly selected trees.
Doubling and summer rains — Since in double rings the space
between the false ring and the outside of the real autumn growth is due
to summer rains, it seemed possible that this segregated autumn
growth might give a measure of the summer rains. This was called
96 CLIMATIC CYCLES AND TREE-GROWTH
at the time " partial ring study." As far as the matter was carried,
the autumn growth was found to be much more closely proportional
to the spring growth and to the winter rains than to the summer
rains. The matter is one of some complexity, because records of the
rains themselves are extremely incomplete, owing to their local and
torrential character and heavy run-off. As a result, the tree-records
of such rains are local and seem of much less value at the present
stage of their interpretation.
Doubles and cycles — In the early Flagstaff work there were two
500-year trees which showed a remarkable half sunspot cycle for
nearly 200 years, beginning soon after 1400. One of these was espe-
cially perfect in this cycle, showing it with most remarkable regularity
(see fig. 17 and Volume I, fig. 32). This tree also was full of double
rings. It has suggested the general question as to the character of the
record of trees which show many double rings. Is such a record
different from those in other trees? So far the answer is thought to be
negative, but there is further work to be done on this point.
Doubles and high altitude — As one studies the upper levels of the
yellow pine, above 7,000 feet elevation near Flagstaff, the double or
extra ring becomes less and less common. So far as tests go, it does
not appear at all in the highest trees. In these higher trees the rings
are more complacent, there is apt to be less pitch, and so less red color,
in the autumn part; yet this autumn part shows a large proportionate
size. Here probably the summer rains play less part in the tree's life,
for they are too local and the run-off is too big. But the winter snows
especially are too heavy, the ground stays moister, and falling tem-
perature is more often the agent which stops the yearly growth.
Other trees — As stated above, the yellow pine in California shows
very rare doubling. Douglas firs and sequoias practically never have
it, but piny on and juniper at the lower levels in Arizona are badly
subject to it.
Large single rings — If rains in Arizona are abundant and well
distributed, growth extends beyond the summer period. A good
distribution here does not mean that they assume at all an even dis-
tribution, for in many years evident division into wet and dry
seasons has never failed. In a long drought the summer and winter
rains decrease and the spring and autumn rains disappear, sometimes
entirely. In wet periods, summer and winter rains are heavy, and
spring and autumn rains come every few weeks. In this latter event
the trees carry their growing-season into autumn. Thus, without
putting on any preliminary red ring, they show a wide growth of
white tissue, ended in autumn by a dense, narrow red ring.
Rings in buried trees — In the vicinity of Flagstaff a considerable
number of buried trees have been washed out at depths from 18
ENVIRONMENT 97
inches to 16 or 20 feet. The upper trees have rings of modern type,
while the lower ones show enormous rings up to a centimeter in size.
They exhibit two characteristics which go with larger water-supply
than noted to-day in Arizona. The centers of the white parts of the
youth-rings show sometimes a softening that gives an effect almost of
an abnormal ring. And when the tree is old the red part of the rings
is very massive and wide in proportion to the rest, and the ring
sequence is subject to characteristic " surges" which are common in
European and other wet-climate trees. In this surging there is con-
siderable difference between largest and smallest rings, but the change
from large to small or the reverse is gradual, so that the mean sensi-
tivity is low, though the rings show strong variations. This sort of
thing is very different from the habit of the living Arizona trees.
Certain small white needle-shaped crystals discovered in these
ancient stumps were identified by Dr. F. N. Guild (1920, 1921) as the
first observed occurrence of terpin hydrate as a natural mineral.
On account of the location, it was named " Flagstaffite."
RAINFALL CORRELATIONS
If successive years were exactly alike, the rings would all be of the
same size, with some alteration with age or injury. But successive
years are not alike, and in their differences there are climatic factors
which appeal strongly to the tree. In northern Arizona, with its
limited moisture and great freedom from pests and with no dense
vegetable population, and with the seasonal correlations above de-
scribed, this controlling factor is unquestionably rainfall. This is
entirely in accord with the rainfall comparisons given below.
Prescott growth and rainfall — This was worked out to 1908 in
Volume I. Its insertion here is to call attention to figure 7, which
gives tree-growth and rainfall at Prescott extended to 1923, with a
new calculation of rainfall from growth, using the method described
in the previous volume. The discrepancies in the last few years
probably arises from the error of boring trees too near the roads, as
was the case with the recent collection. The calculations and plotting
for these curves were done by Mr. D. A. Hawkins.
Flagstaff tree-records and rainfall — The official Weather Bureau
records at Flagstaff began in September 1898. Hence, there are very
few years for comparison with tree-growth. A gain has been made by
using fragmentary records beginning in 1888 and filling in the deficient
months by estimation, using for comparison various records in other
localities of northern Arizona, such as Holbrook, Fort Defiance,
Prescott, and so forth. Practically all the precipitation after November
1 falls as snow, and hence that date is used as the beginning of the
year in reckoning rainfall. But even so the total rain does not show a
98
CLIMATIC CYCLES AND TREE-GROWTH
correlation with tree-growth. So, remembering that the torrential
summer rains do not greatly benefit the trees, the year was divided,
as it is naturally, into winter and summer precipitation, the former
from November 1 to June 30 and the latter from July 1 to October 31.
It was immediately evident that this removed the unexpected dis-
agreement, for the winter values closely resemble the tree-growth, while
the summer rains (averaging 10 out of an annual total of 23 inches)
show no relation to the growth. This is shown in figure 8. Though
the length of record is not great enough to test satisfactorily any for-
mula for reducing rainfall to tree-growth, or the reverse, the evidence
indicates that the same principle of accumulated moisture used in the
2J0O\
S '-co
S
o
30
■
o
a
i-t
10
F rescott tree gr owth
2and3
0 —
30-
20-
Prescott r linfall calculate J from tree gro vth
r
Presc stt rainfall Nov
to Nov. I
0'
I860
1670 1880 1890 1900 1910
Fig. 7 — Prescott rainfall and tree-growth
Prescott correlation (Volume I, p. 66) applies here. The accumulated
moisture curve for the winter precipitation at Flagstaff is shown in
curve 4 of the figure.
Flagstaff and Prescott difference — In the correlation between
rainfall and tree-growth at Prescott, it was not necessary to segregate
the winter rains for the purpose, because the correlation was apparent
when using the annual total. But in the Flagstaff area the winter
precipitation only can be used. Without doubt this difference arises
from the topography of the country. Prescott is situated in the lap of
the Bradshaw Mountains opening to the north and protected from the
southerly summer winds, while the Flagstaff area is mostly on the
south side of the lofty San Francisco Mountains, about which summer
ENVIEONMENT
99
clouds gather more easily perhaps than at any other point in Arizona.
The summer rains, especially near these mountains, are intense and
local and are likely to destroy any correlation.
Arizona-California rain record — There is a further important
advantage in using only the winter rainfall, namely, that such pre-
cipitation is essentially alike in Arizona and California. Since the
coastal region has practically no summer rain to complicate the situ-
ation, the trees of Arizona become admirable recorders of California
rainfall. In fact, it seems probable that these Arizona trees give a
better record of California rainfall than do the California trees, so far
Flagstaff
Nov.!'
n*Ufl:Summer [^Va/X W^V^ AW
Flagstaf)
preci
1850 1860 1870 1880 1890 1900 1910 1920
Fig. 8 — Flagstaff rainfall and tree-growth, with comparison curves; the tree-growth shows
close relation to winter precipitation
discovered, though it is possible that very carefully selected sequoias
will be found to give good records. This similarity in rainfall appears
in figure 8, where the Flagstaff, Prescott, San Diego, San Francisco,
and Mount Wilson rainfall curves are reproduced. From a meteoro-
logical point of view the similarity is not surprising, for the winter
storms of northern Arizona cover very large areas and come from the
coast with very trifling modification, giving precipitation in Arizona
about one day later than in California.
Cibecue drought record — Figure 9 shows the record of a single
tree, J-3, as measured by the auto-plot method. It shows the droughts
between 1870 and 1905 in a striking manner.
100
CLIMATIC CYCLES AND TREE-GROWTH
Sequoia growth and rainfall — The attempts in the previous volume
to find a real correlation between sequoia growth and precipitation
(p. 70) were not satisfactory. Figure 10 shows a decided improvement
brought about by the high-level trees, D 1-5, corrected for gross rings
and compared with rainfall at San Francisco. There seems to be a real
1850 I860 1870 1880 1890 1900 1910
Fio. 9 — Cibecue drought record traced directly from autoplot
1920
relationship here, even though it does not yet equal the Prescott
correlation.
Comparison records — There is yet much to be done in this com-
parison between tree-growth and rainfall, but the obstacle everywhere
is the lack of rainfall records near the trees and over adequate periods
of time. The five Prescott groups showed that in a mountainous
country nearness is very important. Until very recently the nearest
records to the sequoias were 65 miles away and at an elevation 500
San Francisco rainfall
Mlj
3.0 jf
zx>.S
i-o,
1850 I860 1870 I860 1890 1900
Fio. 10 — Sequoia growth and rainfall
feet lower. Colonel John R. White, superintendent of the Sequoia
National Park, is greatly to be commended for starting adequate
records there.
CONSERVATION
In the Prescott correlation, as discussed in Volume I, a conser-
vation formula was applied, based on the idea that the accumula-
tion of excesses or deficiencies in moisture affect the general activity
of the tree. One might say that the trees respond each year to
the amount of rainfall, but that their vitality is affected by the
ENVIRONMENT 101
conditions for some years back. Thus, during the dry period from
1870 to 1905 or so, the trees responded each year to the fluctuations
in rainfall, but with less and less spirit. This suggested that the con-
servation was in the tree itself.
Reversed conservation — In considering the details of smoothing
curves of tree-growth (page 44), it seemed as if the derived value should
substitute for the last of the several used in getting it, but as a matter
of fact there appeared to be better agreement with rainfall when the
derived value was placed in the middle, as in the graphic Hann, used
so much in the western groups. This could only be true if favorable
years affect the preceding year as well as the one after. And in the
growth of trees that is not impossible, so far as we know at present,
as will appear in the next topic.
Possible change in ring-size — The sapwood commonly holds much
reserve moisture which can without doubt be drawn on for the needs
of the tree and whose depletion can be changed to abundance when
conditions are favorable. It may be that the conservation or vitality
of the tree lies in this storage capacity. If so, it is entirely conceivable
that the moisture condition of the growing layer affects the actual
size of the rings near it, and that the ring-size is not absolutely fixed
for several years after its growth. A first attempt to test this matter
by borings in the same tree (FL-90) at 4-year intervals was not satis-
factory, because the cores happened to show some slight irregularities
in growth and were allowed to dry before measurement. Such varia-
tions as are referred to here might show in the dendrograph.*
Water-soaked rings — As an illustration of probable change in
ring-size in dead trees from excessive water-content, reference is here
made to the tests on a fallen sequoia described on page 24.
Repeated use of rain — Somewhat connected with the subject of
conservation is the matter of the repeated use of rain. In separating
the rainfall at Prescott into winter and summer records, the cycles of
the winter rains at Prescott seem to be repeated in the summer rains,
but the important ones in the summer rains do not carry over to the
winter. This seems to mean that winter moisture lasts over locally to
summer, but summer moisture mostly runs off or evaporates. This
difference comes from the different types of storms in winter and
summer. In the former, the storms come from the coast and clouds
are continuous over an immense area. There is no chance for evapora-
tion of any amount. On the other hand, in summer the sun is very
powerful and each morning promotes evaporation over large areas
between the scattered clouds. Storms come from the south and con-
*Since the above was written, Dr. MacDougal has told me that he has detected with the
dendrograph certain changes in the thickness of the two or three outer annual rings, depending
on the temporary condition of the moisture-supply.
102 CLIMATIC CYCLES AND TREE-GROWTH
sist of immense masses of warm air laden with moisture. When these
pass over a large mountain, they are thrust up in the air and start the
storm. When there is not enough motion in the air to draw in distant
moisture, clouds form directly over the valley, evidently composed
of moisture from the valley. As the day goes on and the air gets a
general motion, these clouds are carried forward and contribute to the
rainfall in adjoining localities.*
OTHER CLIMATIC CORRELATIONS
Several factors may enter into the tree-rings at the same time; for
example, rainfall, temperature, length of growing-season, and direct
solar stimulation. These may be isolated in two ways. We may
select and study a special region, as northern Arizona, where nature
has chosen out some one factor and made it preeminent, as rainfall. Or
we may isolate certain relationships as in any other investigations, by
using large numbers of observations, that is, many trees, and averag-
ing them with respect to one or another characteristic.
Temperature — Undoubtedly temperature and the resulting length
of growing-season enter tree-growth. At high elevations this becomes
the controlling factor. Probably that is the reason the Upper Flag-
staff group, FLH, shows departures from the usual curve of that area.
But there is no evidence that temperatures affect the lower pine
growth to any important degree, nor the sequoia growth, especially
in the southern groves, for sequoias at the highest and coldest levels
promptly respond to increased water-supply by enlarged growth, as in the
case of D-31, referred to below in connection with sequoia topography.
Wind — Reinforced rings (see page 32) are interpreted as due to
wind or other pressure exerted in a constant direction. In the pre-
historic material from the ruins northeast of Flagstaff, such rings
rather plainly indicate exceedingly strong spring gales from the west
or southwest, if we can judge by conditions at the present day.
TOPOGRAPHY
The broad effects of topography were encountered and recognized
in large measure while searching for the oldest sequoias. Almost at the
start it was realized that size is far from a final indication of age, for
nearness of water alters the rate of growth profoundly; for example,
it is possible to assign 2,500 years as the approximate time it took
the General Grant tree, which has no running water near it, to reach
its present immense diameter of close to 30 feet. But about 3 miles
west, near a running brook, is a stump which is over 25 feet in diam-
*In Tucson we have perfectly clear views of the Santa Rita Mountains 40 miles south and
7,000 feet higher than the city, the Rincons 20 miles east, the Catalinas 20 miles north, also
close to 7,000 feet higher, the Casa Grande and other mountains 50 miles northwest, and the
Tucsons, 15 miles west, and so on. Cloud formations are easily seen.
ENVIRONMENT 103
eter, but is only about 1,500 years old. That rapid growth is the
effect of contact with an unfailing source of water.
SEQUOIA TOPOGRAPHY
In selecting specimens to settle a dating problem, in 1919, prefer-
ence was given to trees at such distance from the obvious water-
supply that the specific dependence of trees on the nearby brook
could be tested. Thus from Redwood Basin, 15 miles east of the
General Grant Park, a total group of 21 sequoias was obtained. The
trees were scattered for a mile along this valley, whose slope faced
the north. The upper or southern end is near the top of the moun-
tain, but a spring supplies a small stream of water. The upper
trees mostly had a very dry soil, while those below, some 600 or
700 feet in vertical measurement, had more level ground and greatly
increased moisture. The average growth per century in the last 500
years was about 7.6 cm. The least was less than 4 cm. and the greatest
was over 15 cm. The fast-growing trees were mostly close to the
water-course in the lower basin. The average growers were mostly
around the edges of the basin, while the slow-growing trees were
chiefly at the tops of the slopes. Three larger growing trees close to the
upper limit formed interesting exceptions. One was a youthful
sequoia, only 700 years old when cut, and therefore naturally a fast-
growing tree. Another at the very highest point was about 50 yards
above the spring and undoubtedly tapped an underground flow of
water leading to it. Its type of rings was very similar to those in the
basin. The third exception had very large rings, but they were full
of sensitive variations like the slow-growing trees nearby. This
tree is probably over a pocket of water whose help increased its growth,
but which failed in extremely dry conditions. It is evident, then,
that with the sequoias moisture may control the growth up to a
maximum fully four times as large as the minimum.
Ring-type and moisture — The type of ring and its adaptation to
identification and study varies greatly with the moisture-supply.
The large rings of the quick-growing trees are either very complacent,
that is, of the same size for many years in succession, or gross in
character, which means extraordinarily large rings here and there;
and their whole grouping is apparently subject to slow surges in size
as one glances across the sequence from center to bark. Gross rings
in one tree have about an equal chance of appearing or not appearing
in any other tree near by. Since gross and complacent rings have little
individuality, it is not always easy to identify their dates, especially
if the outer layers of wood have been cut away, as was usually done
in felling the sequoias. On the other hand, the slow-growing, low-
moisture trees are full of irregularities which may be recognized in
tree after tree, thus rendering accurate dating a remarkably easy
8
104
CLIMATIC CYCLES AND TREE-GROWTH
process. It is also immediately evident that these latter sensitive
trees give short-period variations far more accurately and effectively
than the complacent trees. These types, as well as the following one,
are illustrated in Plate 3 and figure 3. Yellow pines in the dry climate
of Arizona at so low an altitude that they have the utmost difficulty
in getting water to prolong life become extraordinarily sensitive. In
the same tree one finds some rings several millimeters across and others
microscopic in size or even absent.
Mean sensitivity — Mean sensitivity, which expresses this different
quality in the trees (page 29) depends in large part on the relative
q Growth above average
u Average growth
x Growth below average
Fig. 11 — Land contours and annual growth of sequoias in Redwood Basin
response of trees to climatic influence and so long as there are no large
changes of ring-size due to injury, it gives a good criterion of climatic
effects in trees. Such appears to be the meaning of figure 12, in which
the 10 Prescott trees used in the original rain comparison are plotted
with respect to ring-size and other features, including calculated mean
sensitivity. The first curve shows them arranged in order of ring-
size. The second curve, apparent mean sensitivity, estimated by
inspection only, shows that such estimates may be too much affected by
ring-size to be of value. Curve 3 shows that sensitivity is independent
of ring-size. Curve 5 shows that correlation with rainfall had a slight
Carnegie Inst, of Wash. Pub. 289, Vol. II (Douglass)
/0<f
A. Sequoia topography, ridges; area of D-l, 2, 3, 4, 5, IS, 19, 28, 29 and 30
B. Sequoia topography, basins; area of D-6, 7, 8, 9, 10, 11 and 27
ENVIRONMENT
105
tendency to improve in smaller rings, and assuming some error in
tree No. 69, mean sensitivity is an excellent indicator of a tree's
accuracy in recording rainfall. Curve 4 hints that visual comparison
between curves of rainfall and tree-growth was not very different from
a mathematical correlation test.
2.5
2.00
1 1.5
1.0
05
10
8
2 6
4
3
2
0
3 4-o
ao
4! 'o
.80
.70
.60
/
/
, No; standardized^
M
/>..
/
yj-T^-J-Stdndajrdiz ed \
trees
Mean ring size
>4'7
/
Apparent mean
sensitivity
Mean
sensitivity
Visual comparison
with rain
Correlation
with rain
61 70 64 62 65 68 69 63 66 67
Tree number
Fig. 12 — Ring-size, sensitivity, and rainfall correlations, Prescott
Sequoia contours and cycle lag — Variations in the smoothed
curves are much greater on the ridges than in the basins, where the
water-supply is far more abundant. The complacent basin curves
smooth out the shorter variations. A lag in the basin trees might be
expected, since the water takes time in getting there from the higher
106 CLIMATIC CYCLES AND TREE-GROWTH
surroundings. This has been sought by comparative analyses of basin
and ridge trees. A lag of 3 years or more could have been detected,
but none was found. There may, of course, be a shorter one.
PIKE'S PEAK TOPOGRAPHY
Pike's Peak contours — In collecting 47 specimens from the vicinity
of the Cog Road on Pike's Peak in 1920, locations of test trees were
selected with reference to contour and water-supply. The region
lends itself exceedingly well to such tests. The valley bottoms are
v-shaped rather than rounded, as in the sequoia basins. The sides of
the valleys extend for great distances at a somewhat even slope.
Water is far less abundant and the trees are left more to their own
resources, as it were. The trees are scattered generally and one can
get north and south exposures, stream contact, and other features.
The soil material is relatively homogeneous compared to the Flag-
staff region, where transition is abrupt from limestone to lava or the
reverse, and hence tests are impeded on this account. However, on
Pike's Peak the same tree does not cover all the conditions tested, and
so each must be taken separately.
Yellow pines — Four groups had yellow pines in them, as follows,
in order from north to south : Upper North Transect, 5 ; Lower North
Transect, 2; Brook, 2; South Transect, 2. The mean ring-sizes in
order were, 1.26, 1.60 (variable), 1.74, and 0.81 mm. The first and
second of these showed considerable internal variation. The trees
on gentler slopes or in small side-gullies had the larger mean growth,
while trees on the very steep slopes toward Ruxton Creek had very
slow growth. The largest growth was near Jack Brook, the two yellow
pines there being some 20 feet above the water (and near the dendro-
graph tree). The smallest growth was on the South Transect, with
its ridge topography, very steep slope, and sand areas indicating
dryness.
The south-exposed North Transect, near the foot of a long moun-
tain slope, has growth 75 per cent greater, and the brook has growth
100 per cent greater than the South Transect, which extends nearly
to the top of a low, dry ridge. The extra brook growth is obviously
a question of water-supply. So we infer that the added growth on the
North Transect is due to moisture-supply also, and from the simi-
larity to the Flagstaff area in some prominent features of the tree
record, this better moisture-supply comes in the snows of winter. This
has been considered in some detail, because the Douglas firs next con-
sidered give similar results.
Douglas firs — Douglas firs occur also in the same four groups:
Upper North Transect, 3; Lower North Transect, 3; Brook, 4; and
South Transect, 6. The respective mean growths are 1.09, 0.99, 1.20,
ENVIRONMENT 107
and 0.43 mm. The apparent strong effect of slope in different parts
of the North Transect appears again here and emphasizes the value
of further work directly on that point. The growth on the North
Transect is 142 per cent greater and at the brook 179 per cent greater
than on the South Transect, and the same inference prevails as with
the yellow pines.
Limber pine — Limber pine (Pinus flexilis) occurs in the three
transect groups and the basin group at 9,500 feet. Three trees in the
basin have a mean ring-size of 0.69 mm. The others of two trees each
have 0.93, 1.02 (variable), and 1.00 mm. (variable). Thus, we can
not make conclusions from the data on this tree, except that the
reduced growth in the basin, 9,500 feet elevation, is very likely a
result of temperature.
Engelmann spruce — Two specimens of this tree in the timberline
group, 11,500 feet, give a growth of 0.95 mm., and four specimens at
the brook give 1.16 mm. This difference is quite as likely to be tem-
perature as moisture.
Fox-tail pine — Three trees of this species, Pinus aristata, were
included in the timberline group, with an average growth of 0.63 mm.
Age correction — No age correction has been used in these figures,
but as the selection of trees uniformly favored the larger and older ones,
it is not likely that such correction would materially alter the results.
Summary — The area tested on Pike's Peak lies on the east slopes,
chiefly below the basin. The pines and Douglas firs here show evidence
that water is the prominent controlling factor, the pines having some-
what larger growth than the firs. The limber pines tested had an
average growth between the other two, but were variable and, except
that they give the same tree records as the others, there was no decisive
material regarding their sensitiveness to moisture-supply. A single
group of fox-tail pine gives a similar curve. Engelmann spruce had a
larger growth at the brook, 8,700 feet, than at timberline, 11,500 feet,
and its ring record is far different from the other species tested. Near-
ness to running water greatly increases growth in all the species, and
apparently in the yellow pines and firs does not interfere with their
success as climatic recorders.
SAN FRANCISCO PEAKS AREA
These beautiful peaks, 12,760 feet high, 10 miles north of Flagstaff,
have the rounded mass of an ancient volcanic cone, with the huge
outlying spread of Elden Mountain (9,000 feet) stretching off to the
southeast. They are surrounded by pine forest for miles in every
direction and give favorable opportunity for certain tests.
Altitude effect — Two groups, all yellow pines, may be compared
to get an idea of this effect, namely, Fort Valley, at an elevation
108 CLIMATIC CYCLES AND TREE-GROWTH
of 7,300 feet, at the southwest base of the mountain, and Flagstaff
High group, at 9,000 feet, directly up that same southwestern slope.
The first effect of altitude is an increase of mean ring-size from 1.10
mm. to 1.95 mm. resulting without doubt from the increase of pre-
cipitation at the higher point. The rings themselves of the higher
group appear far more complacent, but can be dated in terms of the
Flagstaff series. In comparing the smoothed curves of the two groups,
the variations (those which become conspicuous in the cycle plots)
decrease from 34 per cent at Fort Valley to 25 per cent in the upper
location, and at the higher point lose much of their resemblance to the
other smoothed curves of that region. On comparing the cycles one
finds at the upper station the 17.3-year length, which is very rare in
the Arizona area. It is more common in the Rockies and on the
northern coast.
Shadow — As previously explained, mountain shadow is an expres-
sion which here refers to the side of the mountain away from the
direction from which storms usually approach. It is, of course, on
the east side of the San Francisco Peaks, since the winter storms come
from the west and southwest. Two groups were taken to the east
and northeast of the peaks; the shadow group (SH) close in at the
foot of the steep eastern slopes at about the same level as Fort Valley,
and Flagstaff Northeast group (NE), about 7 miles farther out from
the mountain center and at the edge of the pines at an elevation some
500 feet lower. The ring-sizes in the SH group is 1.52 mm. and in the
NE group 1.17 mm. The cycle variations of the former are about the
same as FV (34 per cent), but the corresponding variations of NE are
near 70 per cent. On examining the smoothed curves each seems to
be free from short interfering cycles, and perhaps this is its special
quality. The difference between them appears to be a question of
water-supply, which is abundant very close to the mountain, but
rapidly decreases to the east. This same characteristic of relative free-
dom from short-period cycles appears in the Lower Rim and the
Cibecue groups and in the Charleston Mountain group.
Soil and bed-rock — Many of the Flagstaff groups grew on soil that
was not distinctive. The first, for instance, was on deep soil formed
by an outwash fan from Woody Mountain, which is igneous rock.
The 500-year trees of FLU grew on a considerable soil over lime-
stone. Probably the old group at Lake Mary, whose curve is given
in Volume I, page 26, illustrates best the effect of this limestone
soil. Its mean ring-size is about 0.75 mm. It shows rather stronger
variations than the FL curve. For comparison, a group of two trees
at the Lava Beds, 15 miles northeast of town, may be quoted. These
trees were about 350 years old and show large growth when the trees
were small and then a very long continuance of uniform small growth
(0.50 mm. in one and 0.75 in the other), with slight variation. Lava
ENVIRONMENT 109
soil of this sort is full of clay which is formed by decomposition of the
rock. It is therefore water-tight compared to limestone soils. Hence,
moisture caught in the former stays in place and produces a uniform
tree-growth, while moisture entering the limestone soils readily passes
away from the roots. The growth over limestone has larger percent-
age variations with better climatic relationship. This confirms the
reference to this topic in Volume I, page 22.
Soil-moisture gradient — It is possible that a criterion of this
difference could be found by the vertical soil-moisture gradient.
Certain species of pine can grow in very wet land. In such cases the
soil is wet at the surface, then soaked, and then full of water as one
goes down a few feet. Tree sections occasionally appear which show
an enormous increase in growth on draining such land. At an eastern
point (Cape Cod, Massachusetts) the surface soil near the pine trees
is sandy and below that are moist glacier gravels, down to water at
20 feet. In contrast with this, the trees around Flagstaff grow mostly
on a thin layer of soil, perhaps 2 to 10 feet, upon impervious, igneous
rocks, or upon porous and cracked limestone. Over the igneous rock
is often a layer of clay. During a large part of the year one may dig
about the tree, or near the tree, and find the ground apparently dry.
Clays and volcanic rocks hold layers of moisture for a considerable
time, but the soil over the limestone, as observed in some cases, gets
drier and drier as one goes down. The average soil-moisture gradient,
therefore, seems promising as a help in determining certain controlling
factors in tree-growth.
Root conditions — Mr. G. A. Pearson, director of the Southwestern
Experiment Station, has very kindly supplied data regarding depth
of the root systems under certain trees near Flagstaff and per cent of
available soil-moisture, as follows: The greatest depth attained by
tree roots is usually around 4 feet, but only a few of them reach this
depth; the great masses of roots are found in the upper 2 feet. In the
case of spruce, very few roots are found below 1 foot in depth. These
measures cover the woodland (cedar), yellow pine, Douglas fir, and
Engelmann spruce. In his bulletin entitled "Natural Reproduction
of Western Yellow Pine," a series of graphs shows the available soil-
moisture in per cent of dry weight of soil, for the summer months,
including May to September. At 6 inches in depth the amount for
cedar and yellow pine varies from 1 to 9 per cent, and for the other
trees about twice as much. At 12 and 24 inches of depth the amount
for pines and cedars is between 5 and 0 per cent, and for the other
trees about twice as much. The precipitation curves during the same
seasons, 1918 and 1919, show that rainfall in the preceding months is
felt by these trees at 6 inches, and by the high-level trees, fir and spruce,
at 12 inches of depth, for at such levels the rainfall is greater, but at 2
feet only the Douglas fir shows it.
110 CLIMATIC CYCLES AND TREE-GROWTH
CHANGING CONDITIONS
The preceding topographic conditions are constant and their
effects are sought by comparing trees in one location with those in
another. The results are practically constant in any one tree. But
changing conditions produce internal alterations in each tree and
may often be recognized in the ring record after allowing for the normal
change of ring appearance with age.
Shade — The Vermont hemlocks from the edge of Mount Ascutney,
near Windsor, showed a doubling of yearly growth about 1808, due prob-
ably to cutting of adjacent trees at that time (Volume I, pages 41, 42).
Drainage — A small section of Scotch pine in the Berlin Museum
shows minute rings for some 40 years and then suddenly the growth is
quadrupled. As the history of the tree showed, this was caused by
draining the very wet land on which it grew.
Soil deficiency — A very interesting relationship was recognized
by studies in Chaco Canyon in 1926. For 10 years it had been noticed
that certain prehistoric or early historic trees showed normal growth
to a very good size and then rather quickly the growth dwindled down
to a great number of microscopic compressed rings from which there
was no recovery. In human language, the tree starved to death.
Some of these specimens came from Chaco Canyon and a number came
in 1926 from Wupatki, a ruin 35 miles northeast of Flagstaff, in the
region of the Lava Beds and volcanic cinders, which suggested showers
of volcanic ashes as a means of killing forests. But on the bare rock
mesas about Chaco a few pines were found in favorable spots where a
little soil covered the bed-rock. Some were dying, some dead, and a
very few in good condition, but most of them showed the compressed
rings for the last 50 or 100 years. Evidently there was enough soil for
small trees, but not enough to support full-grown trees, and the
shallow beds of soil were drying out and in many cases blowing away.
One small pine in bad condition had 2 feet of horizontal roots bare
before any of them were covered by soil. This lack of soil and change
in its condition, then, is the common cause of that sort of outer com-
pressed rings in this arid area.
Close grouping — A test for the effect of close grouping of trees was
made on the Fort Valley group. These effects have already been
described in connection with tree selection, page 12, and eccentricity
of ring-growth, page 22.
Injuries — The injuries chiefly recognized in the western groups are
fire and lightning-scars, already referred to in the selection of trees,
page 14.
Pests — This topic is a recognition that such effects are of great
importance in the general consideration of tree-rings. Where moisture
ENVIRONMENT 111
and sunlight are abundant and vegetation is densely crowded and
competition is intense, as in wet-climate forests, many individuals
must perish, and pests are largely the agent. Climatic conditions
influence these pests and we find therefore climatic variations in the
trees injured by them, but such effects are apt to be more hidden and
less clear and direct than in the dry Southwest, where the trees are
isolated and rainfall is the controlling factor. Pests, of course, attack
the trees in different ways, but when the growth is seriously interfered
with the rings show diminished size and may disappear, and abnormal
growths may enter.
ENVIRONMENT INDICATORS
The preceding pages of this chapter have dealt with the effects in
tree-rings of various exterior forces; the present paragraphs are
intended as a brief introduction to the general reversal of this process,
namely, estimation of exterior conditions by internal evidence in the
trees. So far as rainfall is concerned this is not new, for most of the
work done by the writer has had that purpose as its central theme.
But in approaching the study of prehistoric and geologic material,
the general consideration of all information contained in the rings
becomes more and more important. So long as one can apply the
principles of cross-identification, it is easy to isolate the climatic
effects, for climatic effects prevail over large areas for a short time,
while topographic influences modify the growth-rates in small areas
more or less permanently. Thus, as the use of groups of trees becomes
less and less possible in studying climates more and more remote, the
separation of climatic from topographic features requires notice to be
taken of all indicators of environment found in the trees. Without
any pretension to completeness, the following classification paves the
way to a future study of this interesting subject.
EVIDENCE IN INDIVIDUAL RINGS
This varies in different species, but in the yellow pine a widely
double ring means a double rainy season, especially if habitually
recurring. Narrow and indistinct doubles and multiples probably
mean the same, but in the extreme, multiple rings may refer merely
to individual storms.
Average ring-size — This reflects water-supply, which consists (1)
of rainfall modified by continent, mountain ranges, latitude, and
altitude; (2) of ground- water, or secondary rainfall, modified by
drainage contours and kind of soil.
EVIDENCE IN SINGLE TREES
Ring-type — Ring-types are: (1) complacent, meaning reasonably
sure water each year; (2) complacent surges, meaning some slow
112 CLIMATIC CYCLES AND TREE-GROWTH
variation in the complacent type; (3) sensitive, meaning limited water-
supply from lessened rainfall and greatly diminished ground-water;
(4) shadow or sensitive surges, meaning very great variations in slow-
growing trees, such as come near the lower (dry) margin of the forest;
and (5) erratic, meaning immense variations in water-supply, causing
some rings to be omitted, while others are very large.
Missing rings — This occurs more often in old age of the trees and
on very dry ridges, where the moisture is not likely to stay in the
ground nearby.
Merging rings — These occur in the pines in dry periods. It does
not usually mean close grouping. It occurs normally in the junipers
and pinyons without close grouping. It probably does not usually
mean close grouping in the big sequoias, but in coast redwood it does
indicate it.
Gross rings — Gross rings in the sequoias are understood to mean
root success with a slight climatic relationship, and to point toward
certain variable conditions of grouping.
Lightning scars — Lightning scars are easily recognized in the tree
section, but not in the core. They are climatic and occur in torrential
summer-type storms.
Fire injury — This also is easily recognized in the section. Such
fires are usually started by lightning and so become climatic in inter-
pretation.
CHANGING RING-SIZE
The change with age is always conspicuous in the diminishing size
from center to back. Rings growing smaller and then larger to a
marked degree, in Arizona, mean drought. Badly compressed outside
rings mean shallow and perhaps denuded soil. Probably soil denuda-
tion is better indicated when the compression lasts 50 or 100 years.
Drainage of soil and relief from too much shade are of rare occurrence,
but when they do come, are recognized by a very considerable change
that is fairly quick and practically permanent. Reinforced rings mean
wind whose season of occurrence may sometimes be estimated.
Climatic variations — Outside the various effects mentioned above,
the further variations from year to year are mostly climatic. If
several trees over some area can be cross-identified, it helps in the
climatic interpretation. But the normal average tree in all ages,
judged from large numbers of prehistoric beams and many fossils
examined and measured, is practically free from other disturbances,
and most of its variations, apart from age changes, can be taken as
climatic. So also the smoothed curve and its cycle analysis tell a story
of climatic variations.
IX. CYCLES
CYCLE ORIGINS
It is now generally recognized that certain small climatic variations
are caused by changes in the sun. The study of tree-growth in this
volume, and especially its correlation with solar cycles described in
this chapter, provide the motive for seeking in the sun the real origin
of larger climatic cycles and in the trees a detailed history of the
effects of such cycles on organic life.
SOLAR THEORY*
Nature of sunspots — The work at the Mount Wilson Solar Obser-
vatory and elsewhere shows that two-thirds of the sunspot groups are
dual, with a leader and follower in the direction of daily rotation.
These are connected below the apparent surface of the sun and form
the two exposed ends of a partial vortex-ring. The brilliant work of
Hale has shown that during the recent sunspot cycles the leaders in
the north and south hemispheres have exhibited opposite magnetic
polarity and that during the two minima under observation, 1913 and
1923, the polarity reversed between the two hemispheres. This
suggests a double sunspot cycle as the fundamental period. Hale
(1926 to 1927) finds evidence that this polarity results from direction
of rotation in the lower parts of the spot. Lighter gases in the upper
and thinner layers of the solar atmosphere are sucked downward into
the spot. Their direction of rotation resembles usually the rotation of
storms on the earth and so is independent of sunspot minimum.
Periodicity theories — No recent advance has been made in explain-
ing the periodicity of sunspots. The weight of evidence favors internal
causes; for example, the polarity phenomenon and the " butterfly"
diagram (by Maunder; it refers to the continued decrease in mean
latitude of sunspots, as each cycle begins, reaches maximum, and ends)
both point to internal causes. The possible extension of solar cycles
back into geologic ages is more agreeable with an internal cause than
with a meteoric hypothesis, using a swarm subject to perturbations
and possible dissipation. On the other hand, there is a possibility that
several cycles will need explanation, and it is hard to think of several
mechanical pulsations in the sun going on at the same time. Mechani-
cal disturbance between a dense core and a lighter shell have been the
foundation of some thought on this subject. Snyder and others have
been at work on a theory involving atomic energy. This might be
called chemical pulsation.
♦Continuing a related topic in Vol. I, p. 84.
113
114 CLIMATIC CYCLES AND TREE-GROWTH
Turner's meteor-swarm theory has the merit of simplicity, since
it merely becomes an extension of the accretion hypothesis (Chamber-
lin and Moulton) and offers many choices in periods. Perhaps size
and shape of a meteor swarm could be invoked to explain crudely the
butterfly diagram, but it is exceedingly difficult to reach with this
theory the polarity and rotation of spots.
Short-period cycles in sunspots — An analysis of monthly sunspot
numbers since 1750 gave a number of possible cycles, of which 7.9
months and especially 10.5 months were the best. The former of
these is the period required by a meteor swarm to pass in a very
elliptical orbit out to the orbit of Mars and back to the sun. The
latter is the period a swarm would have with aphelion near the inner
asteroids. The various periods noted in monthly sunspot numbers
were found to be multiples of 35 days, which is very nearly the sidereal
time of polar rotation of the sun (Abbot, 1925, p. 100). But to the
present time no one has found any satisfactory evidence of planetary
influence in the formation of sunspots, and this coincidence may be
accidental. If there were a tidal effect from any planet, it would
presumably take place twice in the solar rotation.
Solar rotation — Adams and others have applied the spectroscope
to solar rotation at different latitudes and find sidereal periods for
average surface rotation as follows: latitude 0°, 24.6 days; 30°, 26.3
days; 60°, 31.2 days; 80°, 35.3 days. High levels in the solar atmos-
phere rotate faster at all latitudes.
Radiation — Abbot (1925) has done important work upon radiation,
and now has an accurate record of the solar constant from 1918 on.
The values passed below normal in 1922 and stayed so during the
sunspot minimum of 1923. With the beginning of the new sunspot
cycle this constant has come back to normal. All this change seems
to be a correlation with the sunspot cycle, with radiation 3 per cent
above normal at the maximum activity. However, this is subject to
sudden brief decreases, reaching even 10 per cent, when unusually
large spot-groups are about one day past the sun's central meridian.
Ultra-violet radiation — Pettit and Nicholson (1926) have con-
structed a recorder of ultra-violet radiation (which has a powerful
effect on plant life), using a thin silver film as screen and producing
galvanometer deflections by a thermo-couple. The variations follow
the sunspot activity with accuracy and at the same time exhibit a far
greater sensitiveness to its changes than found in the solar-constant
records, reaching perhaps 80 per cent difference between readings at
times of maximum and minimum sunspot activity. The instrument
promises to be of unusual value. Perhaps in this way will come the
solution of a problem formulated years ago on finding the remarkable
solar records in trees around the Baltic Sea.
CYCLES 115
TERRESTRIAL REACTION
Radiation and terrestrial temperatures — H. H. Clayton (1917 to
1926), while in the Argentine Republic, began using daily reports of
the solar constant wired from Calama, Chile, in prediction of weather
conditions for the succeeding 10 days over northern Argentina. This
work he is continuing over parts of the United States in collaboration
with C. G. Abbot, of the Smithsonian Astrophysical Observatory,
under whose direction the solar-constant measures are made. Such
prediction is based on direct effects in temperature observed in the two
weeks or so following changes in the solar constant. Though still not
accepted as conclusive by some (Marvin, 1925, etc.), the abundant
tests already made seem to the writer to indicate a positive link in the
chain of solar influence and terrestrial reaction. The full set of reactions
as they spread over the earth is doubtless incredibly complex, and
this appears to indicate something of the way the larger effects begin.
Radiation and drought — Dr. F. E. Clements (1921), who is work-
ing on the relation of drought to sunspot numbers, found from the
rainfall records that when the relative numbers exceeded 80, a drought
period of two or more years followed in the western United States.
Electrostatic reactions — The electrostatic charge in the atmosphere,
earth-currents, and other electric conditions show response to solar
activity. Dr. L. A. Bauer, of the Department of Terrestrial Mag-
netism of the Carnegie Institution, has done extensive correlation work
(1923) and considers that terrestrial magnetic conditions vary with
" agitated" solar conditions perhaps, rather than merely with extreme
solar departures from the normal. Dr. Fernando Sanford, at Palo Alto,
California, is making extensive records of atmospheric electricity and
earth-currents and finds solar influence in a marked degree.
Glacial varves — Baron Gerard de Geer, of Sweden (1910, etc.,
1926, 1927), has invented a method of measuring time by the annual
clay layers, or varves, deposited under water during the retreat of the
glaciers on the Scandinavian Peninsula and elsewhere. The process is
given a firm scientific basis by a system of cross-identification of
layers in different localities, similar to the cross-identification of tree-
rings used in the present work. By this means he is able to enumerate
several series of years, totaling some 18,000 since the glacial period.
Measurements are made of the thickness of the layers, and thus evi-
dence is found of temperature variations over long periods. The
absolute date of these clay layers is known only within several hundred
years. Dr. E. Antevs has applied the process in the valleys of the
Connecticut and Hudson Rivers and at other points, finding some 4,000
years in the retreat of the glacial ice up the Connecticut Valley.
These long sequences of annual layers displaying a temperature effect
will be of greatest value in studying past climates.
116 CLIMATIC CYCLES AND TREE-GROWTH
Antevs's big-tree tests — Dr. Antevs (19253) has made certain trials
of the sequoias with reference to their use in studying past climates
and reached an indecisive conclusion. But this result was anticipated
from his selection of material and method of procedure. He divided
Huntington's trees into basin and ridge trees, standardized them, and
averaged these two classes separately without correcting the dating,
and then compared the two curves obtained. These curves agreed
for something like the last thousand years and before that disagreed.
The difficulty lies in Huntington's incorrect dates (and possibly
climatic change affecting the two groups differently). Basin trees
grow rapidly and can be counted easily and so contain few errors,
while the ridge trees are slow-growing and contain most of the errors.
Hence, in them the average error would be of the order of twice the
average error found in his dating, which was ±35 years in the last 1900.
In view of these details, given in previous publications (Douglass,
1919, 1922), it should hardly have been expected that undated basin
and ridge curves would show satisfactory agreement. On the other
hand, it should be remembered that carefully dated basin and ridge
sequoias show perfect cross-identification and only differ in the larger
and more complacent growth of the former due to moist soil, as
described in publications referred to.
Ocean rotation effects — One indirect effect of solar causes has been
studied by Dr. C. F. Brooks (1926), namely, the rotation of the
Atlantic Ocean under the pushing effect of the normal winds in different
latitudes. The ocean is a vast storehouse of heat, whose variations
are thus borne to different shores. The circuit takes some 2 years,
and thus could originate short cycles of that order of length. Similar
motion exists in the Pacific Ocean with probably an increased time of
circuit.
Closely associated with the study of this ocean movement is the
work of McEwen (1918, etc.) and Helland-Hanson and Nanson (1920)
and others.
Solar cycle and terrestrial seasons — If a solar cycle of 10.5 months
should exert a precipitation effect on the earth, it would alter the dis-
tribution of rainfall in different seasons, say in the temperate zone, and
produce a 7-year cycle. We shall see that a cycle of this length plays a
part in Arizona tree-growth, but it seems more likely produced by
corresponding changes in solar activity and not as suggested above.
If this short solar cycle were double the length given, or 21 months,
and if its effect did not interfere with the seasons but increased tree-
growth in each year of its occurrence, then we would find rings alter-
nately large and small, as has been extensively observed. This is
referred to in Volume I, page 106. Extended search has been made
for a 2-year period by taking successive annual differences in growth
CYCLES 117
and reversing alternate signs, and plotting. Such curves have shown
extensive 14-year cycles and half-sunspot cycles. However, on testing
rainfall records for such period, the weight of evidence favors a broken
or variable cycle of some 28 months (Douglass, 1915; Clough, 1924).
CYCLES IN TREE-GROWTH
CYCLE RELIABILITY
Definitions — The value of a record of the past is its service for the
future, and prediction becomes possible as repetition is recognized.
Repetition may come at irregular intervals, in which case it may be
wholly accidental; or it may come at nearly equal intervals, in which
case it constitutes a cycle; or it may come at exactly equal intervals,
in which case it can be called a true period.
Short variations — In studying variations of weather and trees,
the first characteristic observed is the great number of short varia-
tions. These are usually interpreted as accidental and without sig-
nificance, for if any large number of annual values be drawn by lot
and plotted, we shall find in the curve a maximum number of 2-year
periods, a lesser number of 3-year periods, and so on in decreasing
rate, all of which, of course, are accidental. So the weather at any
one locality is full of small variations which it is useless to work
on at the start. Such variations remind one of waves on water. We
can picture a combination of land outline and winds which would
produce an exceedingly complex wave system, but we could probably
determine the origin of each. We do not get the same bird's-eye view
in the distribution of weather and we have to class small variations
as accidental in the sense that they are far too complex to disclose
their origins at present. But while these variations are now of no
value in weather prediction, their existence does not prevent the
existence of certain short-period variations buried in them which are
not accidental and whose origins are worth tracing.
Long variations — Accidental and illusive periods decrease in
probability as the length of the period under test increases. Many
accidental 2-year and 3-year periods have been found, and even one
11-year period in numbers drawn by lot, but 20-year periods or over
have proved extremely rare in accidental sequences. Therefore, in
the analyses which follow, periods under 10 years have been given
little weight unless extraordinarily prominent, and as the length of
period advanced from 10 to 20 years and beyond, more and more
reliability has been credited to any evidence of periodic variation.
Criterion of reliability — A criterion for judging the reliability of
cycles has been suggested which for simple reasons has not yet received
extensive use. It is applied by taking all the values in a curve con-
118 CLIMATIC CYCLES AND TREE-GROWTH
taining the cycle, and twice drawing them out by lot; thus producing
three curves, of which one is genuine and two spurious. If the genuine
one can be distinguished from the others by the cycles alone, without
other marks of identity, then the cycles are there. We can hardly
yet make application of this to rainfall or tree-growth curves, because
we do not know (or are just learning) what cycles ought to be there.
On this account a half dozen criterion tests have resolved themselves
largely into solving the question of the existence of cycles over 20
years, for that was the only known mark of identity. That in turn
depended vitally on the length of the curve under test, for a cycle
does not carry conviction unless it is repeated five or ten times in the
record. So the trials on short curves of 50 or 75 years were not suc-
cessful, while those on curves of 200 years were. It is probable that
there will be extended use for this criterion, but in the absence of
better knowledge of the cycles to be expected it has not been thoroughly
tried and another method of judging reliability has been applied,
namely, identifying similar cycles in many trees and over wide areas.
Cycle identification in small areas — In the early use of the cyclo-
graph it became a matter of interest to know whether cross-identifica-
tion could be done by cycles. To test this, an early general curve of
the Flagstaff region was prepared as a standard. An assistant selected
125-year portions of other Flagstaff trees without letting me know
to what tree or to what part of the 500 years they belonged. By
cycles alone each unknown was compared with the standard 500-year
curve. In the first trial of 10 unknowns, 7 were dated correctly, and
in the next trial of 10, 8 were dated correctly. In other words, the
cycles in any given tree in the region specified bear 75 per cent resem-
blance to a good average cyclogram of that region. Dating by size of
individual rings is considered to have a reliability of 95 per cent or
more. This decreased reliance in cycles is due in part to over-
importance given in those tests to short-period cycles, before their
unreliability was recognized.
Cycle identification at 200 miles — Two groups of 8 or 10 trees each,
one from 40 miles north of Aztec, New Mexico (BMH), and the other
from 18 miles east (AE), were compared with the Flagstaff records.
The resemblance in the cycles is extremely close. Periods of 14, 17,
and 21 years appear in all three groups in practically identical form.
In this comparison cross-identification by cycles was carried over 225
miles of country (see Fig. 19 and Plate 9, page 132).
Cycle identification between Arizona and California — A still more
difficult test was made between the Flagstaff area and the big-tree
area. A selection of California trees was made in the following manner :
The last 500 years of each of 34 trees were plotted and the resemblance
of the cycles to Arizona and New Mexico cycles was reviewed and
CYCLES 119
each tree marked in some way to represent its resemblance. The best
four (D^4, 16, 20, and 21) were then taken by themselves, having a
regard both to this resemblance and to their wide distribution in
California, and the average record of the 4 trees plotted for 2,000 years.
These plots were slightly smoothed and duplicated so that each one
overlapped its neighbor half-way, and nearly every part of each tree's
record appeared twice. In exactly the same manner two other com-
plete sequoia records were prepared; one was an average of D-3, 12,
20, and 23, preferred for showing the sunspot cycle, and the second was
the "best selected" sequoias, with good consistent records. All these
were prepared by an assistant and marked by him with a reference
letter, so that I had no idea of the date or identity of any curve. The
assistant then selected 250 years of Flagstaff tree-records whose exact
dating was also unknown to me. Comparison was made by cycles
between the Flagstaff record and the unknown sequoia records. After
they were completed, all dates of resemblance were looked up, and it
proved that instead of the six possible correct coincidences, there were
a dozen apparent agreements, of which six, or 50 per cent, were correct
and the other six scattering. Thus it appeared that in group averages
there is a 50 per cent resemblance between the cycles in tree-growth
in Arizona and those in tree-growth in California, and that a fair
assurance in cross-dating between these two regions can be reached,
if one uses, as in this method, enough data from which to obtain a
convergence of results.
Advantages of the cyclograph — This instrument, which converts
mathematical integration into a photometric process, has been used
almost exclusively in the analyses about to be described. Its extra-
ordinary advantage is its rapidity of analysis and its flexibility in
showing the analysis of every part of the curve at the same time in the
cyclogram or differential pattern, and also in its independence of
fixed periods, for it shows many periods at once, whether fixed, variable,
or broken.
Disadvantages of the cyclograph — The chief disadvantage is that
in its present form one can not assign quantitative amplitudes. This
could be done by passing the photographic negative of the cyclogram
under a recording photometer, of which there are several types suffi-
ciently accurate. The amplitudes could be derived easily from the
galvanometer curve.
PERIODOCRITE
Professor C. F. Marvin, chief of the United States Weather Bureau,
has suggested (1921) the use of a process which he names the period-
ocrite. It simply solves the question : does the application of a given
cycle reduce the probable error? If so, the use of the cycle is justified.
9
120 CLIMATIC CYCLES AND TREE-GROWTH
ZONE CENTERS AND THEIR MEAN CURVES
The material collected over western areas has opened such a field
for immediate development that the contents of this chapter can only
be regarded as a transition rather than a conclusion. Such progress
and results as have appeared to date will be given, but they must be
taken as subject to revision at a later time.
Cross-identification — Introductory to the comparison of smoothed
curves, it should be recalled that cross-identification by individual
rings is the exact and reliable method of comparing curves over large
or small areas. In the western States it is found to grow easier and
more reliable as the climatic stress of the arid regions is approached,
that is to say, such dating is highly satisfactory within the Arizona
region, which extends to the Rio Grande on the east and the coast-
line on the west. It is fairly satisfactory between Arizona and Central
California, as also from Arizona to the central Rockies, but the northern
States, with a very different tree-record, do not cross-date with Arizona.
An electrical instrument is now under construction which it is hoped
will reduce this cross-dating by individual rings to mechanical quanti-
tative measurement. When that is accomplished it will perhaps be
possible to express similarity between groups by a single coefficient.
Comparison of smoothed curves — The crests of these curves give
the phase or epoch of maximum of the various cycles which may not
be the same in different regions. Two results appear in this curve
comparison, namely, first, a real separation into the three zones, and
second, a latitude effect in which there is much more similarity east
and west between the zones in their southerly or drier parts, than in
the northerly moist latitudes.
Flagstaff area mean curve — In consequence of the southern sim-
ilarity just mentioned, the Arizona area could be regarded as exceed-
ing the others in size, for Pine Valley and Charleston Mountains show
similarity on the west, and Basin Mountain, Aztec East, and Santa
Fe repeat Arizona features on the east. However, the Catalina and
Santa Rita Mountain groups near Tucson show marked differences.
The Flagstaff area presents an excellent central homogeneous collec-
tion of curves from the Grand Canyon to the Rim and Cibecue, a
distance of 175 miles (GC, FV, SH, NE, FL, FLU, RL, and J). These
curves have been combined together graphically and the mean result,
1702 to 1920, is shown in figure 18, upper curve, page 128. This curve
is important, because it is probably a better rainfall curve than those
of the other zones. We note that shorter periods are largely smoothed
out, except parts of a 7-year cycle. A period of 21 years (with lesser
14-year effects) strongly dominates, thus agreeing with a result reached
in 1908 and referred to in the previous volume (p. 104). The sunspot
cycle with its half and double appear in the early parts of the curve,
CYCLES
121
as also 8.5 and 17 year cycles. Further discussion will be found below
under Solar Records in Tree-Growth, page 125.
Pike's Peak area mean curve — The groups in the Rocky Mountain
zone cover a smaller area than those in the other zones. Thus the
area represented by the mean curve is limited to the east slopes of
Pike's Peak in the vicinity of the Cog Railroad. The homogeneous
l.b
1.0
0.5
1700
80
a 0.5
j~, s
\ /\
r\
/\
/*"■" \s \/ \y v \
~ 1300 10 20 30 40 1850 60 70 80 90 1900 10 1920
YEARS
Fig. 13 — Pike's Peak area mean curve, PPM ; average of six groups, standardized
and smoothed
collection of groups includes six, PPB, HNT, LNT, C, ST, and BDF.
The Laramie group and those from Santa Fe and the Aztec region are
similar, but not quite enough like the central collection to be included.
The mean curve of the six named is shown in figure 13. It appears to
show strongly a 5, 10, 20 year cycle and a triple sunspot cycle divided
into halves and quarters (that is, an 8, 17, 34 year cycle).
Sierra Nevada mean curve — The distribution of groups in this
zone is better than in the other zones. From The Dalles in northern
4.0
2.0
1700 10 20 30 40 1750 60 70 80 90 1800
4.0
2.0
a
a
<
I8C0 10 20 30 40 1950 60 70 80 90 1900 10 20 1930
Fig. 14 — Sierra Nevada area mean curve, SNM ; average of four groups, standardized
and smoothed
Oregon to Pine Valley near San Diego the nine locations are fairly
well spaced. There is pronounced similarity in the smoothed curves
in all of these except Klamath Falls and Pine Valley, but the best
agreement occurs between those in the Sierra Nevada Mountains from
Calaveras to Mount Wilson and the mean curve is the average of
these, namely, CVP, BC, EP, and W groups. It is given in figure 14.
122 CLIMATIC CYCLES AND TREE-GROWTH
It will be noted that this inner group does not include the trees from
San Bernardino Mountain, which show a remarkable double sunspot
cycle. These were not included because they seemed to represent an
extreme condition of some sort which should be studied by itself.
A preliminary analysis of the Sierra Nevada mean curve shows a 5,
10, 20 year cycle, very strong in early half (1700-1800), a 5.8, 11.8,
22.8 year cycle, strong in the late half (after 1800), and a 7±, 14-year
cycle growing strong in the late half.
METEOROLOGICAL AREAS: THE PROBLEM OF COMBINATION
Use of trees in outlining meteorological areas — Very few weather
records reach 100 years in length, and they are apt to be at widely
scattered places, subject to different conditions, such that the records
can not be combined advantageously, but a forest gives a vast number
of long records in some definite region. With proper care we do not
need to mix records of different types. No doubt we have exaggera-
tions, and in young trees we have a smoothing-down of variations.
In terms of thermometer and measuring-rule, our values are not of the
highest precision, but as seen from the viewpoint of actual growing
vegetation the tree record is hard to surpass.
Disadvantages — While we have as yet no substitute for the length
of record given by the trees, the chief difficulty is that the reaction
of trees to certain weather elements that physical conditions make it
easy for us to measure (temperature, precipitation, etc.) is not every-
where proportionate to these causes and under certain conditions may
be fundamentally changed, as, for example, in the reaction to moisture
in wet climates. The differences between the zones as shown below
is perhaps in part an illustration of this. That investigation is as yet
unfinished.
Problem of combination — Meteorological reports are collected in
various districts which are political subdivisions, and are not outlined
by weather conditions. When the student begins to combine areas in
order to get general averages, he is confronted at once by the problem
of combination, for before combining he has to find out what areas
it is safe to combine without losing valuable material. The error of
too large combination kept meteorologists from admitting solar effects
in weather for a score of years.
Tree-record combinations — In work with the western groups the
general experience has been that trees in the same forest are very
much alike and may be combined without loss, if care is taken to use
trees exposed to similar conditions of soil-moisture. Thus the groups
were formed. In combining groups the guides have been: (1) geo-
graphical outlines of zones, (2) obvious similarity in smoothed curves
which probably is equivalent to phase similarity in cycles, and (3)
CYCLES
123
obvious similarity in cycle-length. The relations between phase
and zone have been described above in connection with smoothed
curves. The relations between cycle-length and zone are now under
consideration.
Effect of combination on cycles — In a previous chapter the cycle
analysis of each group was given, some 42 groups. Here we have a
large number of widely scattered small units. The dominance of
certain cycles in these zones seems very significant. When we com-
bine the curves and use the mean curve for a homogeneous area, the
cycles in this general curve are reduced in number, giving a few
powerful ones and only traces of others.
Present importance of small units — It is felt that the group is still
the important unit for analysis, and though more general combinations
are illuminating and helpful, the fundamental information is in the
group.
CYCLES IN WESTERN ZONES
Arcigram — In a periodogram the ordinates give the amplitudes of
the various periods in a given curve. In the summaries below the
ordinates give the number of occurrences of each cycle-length over a
given area, and for the present the word " arcigram" is used to refer
to this kind of a diagram. The distribution of cycle-lengths in the
three western zones is shown in figure 15.
Derivation of ordinates — The number of groups in the three zones
is nearly the same: Arizona, 14; Rockies, 15; Coast, 13. In the first
plotting of figure 15, the ordinates consisted of the number of occur-
rences of cycles in each half unit of period; for example, those between
12.0 and 12.4 inclusive, and those within 12.5 and 12.9. But in the
original analyses three weights had been assigned, and in the curves in
figure 15 each occurrence is counted one, two, or three times as it was
assigned weight. This inclusion of weights made no essential change
in the curves.
Western area cycles — The cycle occurrences in the three zones
were counted and plotted separately, and the important characteristic
appeared that the cycles are much the same in each, with somewhat
different emphasis. This similarity, as shown in the figure, is evidence
in favor of the approximate values here given, which appear to be very
nearly simple fractions of 34 or 35 years, as can be seen in the following
list:
6.8 |
7.6 (rare) T\ or
8.6 i
10.2 f
11.2 to 11.7 i
14.2 |
17.2 £
20.5±1 for
22.5 to 24.0 f
25 + (rare) |
28±1 ft
31± (rare) f
35± 1
124
CLIMATIC CYCLES AND TREE-GROWTH
This relationship of western cycles only appeared in recent work
and is still provisional. It may be real, but, on the other hand, there
may be some preferential selection by the analyzing instrument or the
observer, in spite of great effort to get rid of such errors. It should be
added that the cj'cle given as 20.5±1, really covers the interval from
19 to 21, and could have interpretations at 19, 20, or 21 years. The
brief study, given later, of solar records in the long Flagstaff tree-
records, throws a little more light on this.*
5 6 7 0 3 10 II 12 13 K 15 16 17 18 19 20 2; 22 23 24 25 U 27 28 29 30 31 32 33 34 3b ?G 37 38 39 40
5 6 7 8 3 10 II 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 3940
Cycle length in years
Fio. 15 — Cycles in western zones
Arizona zone — The Arizona zone is distinguished by the absence
of 8, 10, 11, and 17 year cycles and the great dominance of 14 and 20
years. Its double sunspot cycle averages a little over 23 years.
Rocky Mountain zone — Cycles of 10, 11, and 14 years are largely
lacking. The 8+ and 17 year cycles have more prominence here than
in the other zones, but the 20 and 23 year cycles are the strongest in
the zone.
♦Recent independent tests sustain these results.
CYCLES
125
Coast zone: — Cycles 17 and 20 years are largely lacking. The 10
and 11 year cycles are stronger here than in the other zones, but the
23-year cycle is the strongest in this zone.
Zone summary — The characteristics of the three zones are brought
out in the following list :
Zone
Prominent
Deficient
Arizona
14 20 years
8 17
20 23
10 11
14 23
10 11 17 years
10 11 14
17 20
Rockies
Coast
Sequoia cycles — The above summary deals almost entirely with
the yellow pine; for comparison the cycle analyses of some 32 sequoias,
from 1400 on, have been combined into one arcigram which agrees
7 B 9 10 II 12 13 14 IS 16 17 16 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 39.
Cycle length in years
Fig. 16 — Sequoia cycles
with the pines in the coast zone in giving prominence to cycles of 10,
11, and 14 years, but differs from them in having a very prominent
20-year cycle with lowered emphasis on the 23-year cycle. This
includes the entire list of sequoias in the General Grant Park region
without selection of any kind, and indicates more resemblance to the
Arizona reaction than appears in the pines of the same area.
SOLAR RECORDS IN TREE-GROWTH
Historical confirmation — From the start the sunspot cycle was
sought in the Arizona pines, and during large portions of their growth
it seemed perfectly evident, but for scores of years near 1700 it failed
entirely; in 1914 the writer very nearly gave up the idea that the trees
show it. In 1919 (Volume I, p. 102) the cycle record was given with
the statement that from 1660 to 1720 the sunspot curve " flattens out
in a striking manner," and again, "the sequoias show strikingly the
flattening of the curve from 1670 or 1680 to 1727," and again, "it
seems likely that the sunspot cycle has been operating since 1400 a. d.,
126 CLIMATIC CYCLES AND TREE-GROWTH
with some possible interference for a considerable interval about the
end of the seventeenth century." Early in 1922 a letter was received
from Professor E. W. Maunder, of England, calling attention to the
prolonged dearth of sunspots between 1645 and 1715, and saying that
if there were a connection between solar activity and the weather and
tree-growth, this extended minimum should show in the weather and
in the trees. On receipt of the letter, this period was immediately
recognized as the interval referred to in which there was entire failure
in attempting to trace effects of the well-known solar cycle. The
sequoia record for the last 500 years, as summarized in figure 33, page
103, of the previous volume, confirms minutely the result. So also do
the Vermont hemlocks and other tree-records.
Dearth cycles — In 1922 or before it was noticed that when the
11-year cycle disappeared from the trees near 1700, two other cycles,
one of 10 or 20 years and the other of 7 or its smaller multiples, became
prominent in its place in the Arizona pines (see Plate 9 and Fig. 19).
Soon after, it was noticed that the Vermont hemlocks and the sequoias
of California show similar change at that time. And then it was
observed that these three cycles appear generally in the western trees;
they are, first, the known sunspot cycle of about 11£ and its double
of 23 years; second, 10 or 20 years; and, third, 7, 14, 21, or 28 years.
These three cycles, with others mentioned below, have been confirmed
in the present study of the 42 western groups. There is some reason
to think that all of these cycles come from the sun, for at different
times the sunspot cycle itself has changed to one or the other of them.
For example, from 1748 to 1788 there were four complete cycles of
close to 10 years each; and from 1788 to 1837, 49 years, there were
three complete cycles of about 14 years each and one of 7. It seems
at least likely that these other two cycles, found in western trees with
extraordinary persistence, are also of solar origin.
Wet and dry climatic effects — In this study of cycles in the western
yellow pine it was found that in this dry region, where trees are
specially sensitive to rainfall, they show, besides other cycles, a double-
crested 11-year variation, just as the rainfall itself does, but in the
moist coastal regions this solar cycle has more often a single crest
like that of the sunspot numbers. This agrees with the result of 10
years ago, in which the wet-climate Scotch pines of North Europe,
especially near the Baltic Sea, showed a direct single-crested cycle
having a remarkable resemblance to the curve of sunspot numbers
(Volume I, p. 77). Their growth gave the solar changes with an
accuracy exceeding that of any trees of the southwestern area. (See
S-14 in Plate 9.) This remarkable solar record is a wet-climate
phenomenon, but it is not yet clear just what causes its accuracy.
It seems probable that these trees follow the sunspot cycle more
%(*
Carnegie Inst, of Wash. Pub. 289, Vol. II (Douglass)
Spruce, S-14, from South Sweden, showing sunspot cycle; wet climate reac-
tion. Dots give dates of sunspot maxima beginning with 1830
CYCLES
127
closely than do the weather elements in which they live, and it is
perhaps safe to repeat the suggestion made by the writer in 1922 that
there may be some more direct line of cause and effect from the sun
to these trees than we have taken into account, such, for example, as
radiation (possibly of short wave-length), that is especially favorable
to trees growing generally under cloudy skies. In tree-groups along
the Atlantic coast of this continent, the 11-year cycle is also prominent,
but it has a phase displacement of 2 or 3 years.
SOLAR CYCLES
Eleven-year cycle in long Flagstaff record — Combining the long
Flagstaff century curve beginning in 1285 with the Flagstaff mean
usr
1500 10 20 30 40 1550 60 70 80 \ ,' ' 90 1600
I.S
A
j\
i
\
Ul
/'
\J
"W>
^L A
A/
\ /
\
r
\r
^N/\
/
y\j
\j
Y
\
/
V
n*
\
/
*600 10 20 30 40 1650 60 70 80 90 1700
YEARS
Fig. 17 — Flagstaff century curve, FLC, a.d. 1285-1700; standardized
and smoothed
area curve from 1700 on, one has full 625 years of sensitive tree-growth
(see Figs. 17 and 18). To this a superficial graphic analysis has been
applied with a number of interesting provisional results. The first
test deals with the extended half-sunspot cycle in the early Flagstaff
curve, found in 1908 and shown on page 102 of the previous volume.
The first hundred years of our present curve is made up of several
radials of one tree which had suffered a considerable injury in 1295.
It begins to show the cycle with certainty about 1320. The cycle
continues without interruption till 9 other trees join it between 1385
and 1419, during which time it is discordant, probably in part from
poor merging process in adding the new trees. Then it continues
without discord till 1541, 1550, and 1566-67. After that it is in
128
CLIMATIC CYCLES AND TREE-GROWTH
accord again till 1617, and from there on it decreases its accuracy, and
the variations typical up to that point disappear from the curve.
The curve from 1700 on shows much less of the sunspot variations,
but in the Grand Canyon group, one of its components, and others
also, the half cycle shows well from 1850 to the time of collecting and
with almost the early regularity. Brief calculations show that the
L5
/
v
A
1 '°
1.5
j
y
Va
,A
/N
A
-V
\
A/
r %
\J
S
/V\>
1 \
V
\j
\s
VJ
/
2 i.o
. 1.25
3 l0
/>
A
K^^-
A/
\J
v
A
r
k y\
A
'V
V-
V
j
\J
°\
S\
L -^
K/^
\
1800
1.0
/
w
/
'^v
1.0
0.75
1.0
J/
y
k
/
\y^
V
1900
1950
60
80
Fia. 18 — (1) Flagstaff area mean curve, FAM; average of eight groups,
standardized and smoothed; (2) synthetic curve; (3) residuals
long variation in the earlier curve agrees exactly in phase with the
recent years, and so we find through practically 600 years a mean
value of the sunspot cycle of 11.30 ± 0.02 years. From the correlation
diagram already referred to on page 104 of Volume I, we see that the
most direct relation between the double-crested growth-curve of the
above stated length and the single-crested sunspot curve is that a
growth maximum occurs at the time of a sunspot minimum. On
CYCLES 129
plotting in the early times of sunspot maxima and minima, according
to Wolfer, we find that the telescope was invented and spots observed
just in time to show that it has always been the same maximum of the
double-crested tree-cycle that came at sunspot minimum. This in
itself is an interesting fact, for it intimates that the 11 -year cycle can
be called a well-defined period which the sunspots do not always follow
exactly. Apparently, the 11.30-year period and the sunspot cycle are
two different things.
Seven years and multiples — There is further information in the
tree-records which perhaps adds light but does not fully solve the
solar puzzle. The Flagstaff area mean curve in figure 18 has some
large variations which are roughly solved without difficulty. A 21-
year cycle is very prominent and a 14-year and a 7-year cycle easily
evident. These values seem to be very close to 7.0 and its multiples.
The time of maximum of the shorter periods is about 1910 and for the
21-year period possibly 4 years later. This, however, is not a rigorous
solution. The amplitudes (from the mean value) increase from 5 or
10 per cent in the 7-year to double that in the 14-year and triple in the
21-year periods. This group of multiples of 7.0 becomes evident about
1663 with a large maximum of the 21-year type. It rather fails in the
1680 's, but after 1700 comes in regularly. Its beginning is thus con-
nected with the great dearth of sunspots described by Maunder (1922).
A single maximum of this apparent type occurred in 1479.
Nine-year-plus cycle — A very crude graphic synthesis of these
periods has been made (and extended to 1980) whose resemblance to
the original curve is fair. This is shown in the central curve in figure
18. So a set of residuals between it and the original was plotted
and two interesting features appeared, as shown in the third curve of
Figure 18. A set of crests came in 1747, 1758, 1766, 1777, 1786, and
1794, all of which except the last came close to the sunspot minima
during that unique interval when the sunspot cycle averaged about
9.3 years in length. (The minima were 1755, 1766, 1776, 1784, 1797.)
The length derived from these crests is 9.4 years, which thus gives us
a terrestrial cycle related immediately to a definite solar cycle. It is
possible that the fairly common climatic cycle of 19 years is the double
of this solar cycle. From 1800 to 1880 the agreement between the
natural and synthetic curves is good, except for the extreme minimum
growth in 1847 and 1880, 33 years apart, and from 1880 to 1905 the
7-year cycle is practically absent, reappearing again subsequently.
Historical changes — In a general way it is safe to say that the
sunspot cycle and its double and triple values are very common. The
double value has persisted in Arizona for 600 years with interruption
from 1630 to 1850 or thereabout, and in some North European locali-
ties it shows for the last century and a half covered by our tree groups.
130 CLIMATIC CYCLES AND TREE-GROWTH
The triple period, essentially Bruckner 's cycle, has operated in Arizona
for the last 200 years and in Norway for 400 at least. Western zone
cycles are largely its simple fractions. A hundred-year cycle is promi-
nent throughout the 3,000 years of sequoia record, and a cycle of
about 150 years shows in the 600 years of yellow pine. It seems fairly
probable that the 11-year cycle can be judged by the variations in its
double value, which in some cases is more easily traced through long
periods. A very incomplete review of the sequoia record suggests that
from 1300 b. c to well after 1100 b. c, the 11-year cycle was strongly
developed. Near 300 b. c. it was again apparent, though not very
conspicuous. During the first two centuries of our era it was again
highly dominant. It reappeared from 375 to 475 and from 600 to 650
and was operating during much of the ninth century, though mixed
with other cycles. Then it appears only occasionally until after 1300,
when it again becomes fairly continuous, except for the changes in
the seventeenth century (1633 to 1712) above noted. This is a pro-
visional report and will, without doubt, receive changes when the
sequoia records are minutely examined for the purpose.
Climatic patterns — From this study of the geographical and his-
torical distribution of climatic cycles it is inferred that they are
climatic patterns made up of interferences between a number of simple
fractions of a few fundamentals, traceable to solar influence. This
form of interference seems to produce pseudo-cycles which vary with
the phase relationship of the fundamentals and whose resulting tem-
porary character has always been a stumbling-block in the way of
investigation.
CYCLOGRAMS
An analytical review of some of the cycles mentioned in this chapter
is given in Plate 9. To one who understands the extent of information
in the cyclogram, and, if I may add, the spirit of this information, that
is, its frankness in showing its own accuracy or error, these figures
visualize the facts in a most compact and convenient way.
Cycle identity across 200 miles — The first three cyclograms, taken
in immediate succession on the same plate, show an analysis at a
period of 18.1 years (represented by the thread) of the Flagstaff curve
and the two points near Aztec in northwest New Mexico, from 1700
to about 1910. The most conspicuous alignment is the 21-year cycle,
but 17- and 14-year cycles also usually show. The similarity in general
pattern is apparent at once. This is evidence of the reality of the
cycles and of their climatic significance (page 118).
Dearth cycles at A. D. 1700 — The Vermont hemlocks give an analy-
sis shown in cyclogram 4. Here the Bruckner cycle dominates from
CYCLES 131
1650 for more than 100 years, accompanied by a 28-year cycle, of
which traces are found to continue even in the late half (1775 to
1900), in which the sunspot cycle and its double prevail. The latter
condition extends from about 1750 to the present time. In the early
half also a 20-year cycle is faintly shown by a distinct alignment, as
marked in the explanation diagram. So in this record also we find the
11 -year cycle replaced by 20- and 28-year cycles during the dearth
of sunspots near 1700 and for a brief time after, that is, to about 1750.
Cyclogram No. 5 gives an analysis of the sequoia record in four
trees, D-3, 12, 20, 23, which were selected for their excellence in show-
ing the solar cycle. The interval covered is the 400 years from 1450
to 1850 at a set period of 23 years, represented by the thread. The
change from the double sunspot cycle to the 10, 20-year cycle took
place near 1630. At about 1700 all three cycles (10, 20, 23, and 28)
begin to show. In the last half century or so, the 20-year cycle domin-
ates, which agrees with the "arcigram" of the sequoias mentioned a
few pages above. The dearth cycles (20 and 28) were forming by 1550
more or less, and they are the ones which prevail during the absence of
sunspots near 1700.
The Flagstaff evidence of dearth cycles is shown in cyclogram 6.
Here it is easy to trace the double sunspot cycle from 1400 to its
end near the center at 1650. The 14, 28-year cycle enters at about
1550, but after 1700 it is practically lost, due to smoothing and the
great dominance of the 21-year variation, which continues to the end.
The 35-year variant begins not far from 1700. This cyclogram was
taken in 1921 from the original Flagstaff group, smoothed by 5-year
overlapping means; all the others shown are from original unsmoothed
plots or from Hanned curves.
Flagstaff long record — Cyclograms 6, 7, and 8 show the analysis
of the long Flagstaff record (500 years used here) at three different
settings for cycle-length, 22.1, 14.0, and 7.0 years. The first, as just
described, shows the main features of the sunspot cycle to 1650 and
the 21-year cycle since 1700. The second gives more detail. The 14-
year cycle enters near 1500 and continues to the end. The 11-year
period, often double, may be traced from 1400 to well after 1600.
A 9- to 10-year cycle is evident from about 1650 to 1775 or so. Thus
the "extra" cycles (10 and 14) are clearly found connected with the
dearth of sunspots about 1700.
The Flagstaff analysis at 7.0 years is given in cyclogram 8, but the
numerous short cycles shown are not so important and sure as the
longer ones already described.
Arizona drought cycles — There is no doubt that a demonstration
of the periodic action of droughts would be of great value to the South-
west. Accordingly, in 1925 a "skeleton" plot of Arizona droughts,
132
CLIMATIC CYCLES AND TREE-GROWTH
shown in the trees, was made and analyzed. The major dry periods
came at 1440, 1580, 1735, and 1880 to 1900, or an average of about
150 years apart. Also, the single tree which gives a record beginning
at 1285 shows a great depression at 1295 to 1300, which conforms to
this 150-year spacing. Thus the major droughts give a cycle which
was long since (1914) noted as occurring in the Arizona record. Cyclo-
grams 9 and 10 show analyses at 14.6 and 20.2 years as the best to
1700 1900
1
Flagstaff
17
<
17
00 , l»
JO
2
Aztec
/7
East
<
"f
1
700 19
00
3
Basin Mtn
• %^*
*#^«
*
»/
^A.
18.)
IS. I
Cycle identity across 200 miles
1650
4
Vermont
hemlocks
Dearth cycles at 1700 A.D.
400
me
- 5- <-
Flagstaff cycles near 7,l4and 22
1442 1580 1735 1900
M \* »«4# ,,(* ******
/*x
10
»>",
I #£«««*
^ « \»\ » <0
»V • iN *
s w »W « « V
,«*<» <(M*«»
/* V* WW ft(,#>
tfV #>#*
^ « \«« «»v\Ki
Arizona drouth cycles
Fig. 19 — Details of cyclogram patterns in Plate 9
cover this 575-year lapse of time. These cycles are near the 14.0
and 21.0 values and may be identical. It will be seen that there is a
tendency to group the droughts at intervals of something under 50
years. This could be 42 years, the interval at which 14- and 21-year
cycles have their major effect on each other. Probably the 150-year
effect emphasizes whichever 21-year multiple is nearest, with some
modification from the 14-year cycle.
0^
Carnegie Inst, of Wash. Pub. 289, Vol. II (Douglass)
1, 2, 3 — Identity across
200 miles
6, 7, 8 — Analyses of
Flagstaff pines
4, 5 — Dearth cycles
near 1700 a.d.
9, 10 — Cycles in Arizona
droughts
Cyclograms
Explanatory diagram on opposite page
10
CYCLES 133
CYCLES AND CLIMATE
Three major lines of interest have emerged in this study of cycles
as it has developed in this chapter. The first was the distribution of
cycles over western areas in approximate simple fractions of 35 years
(or perhaps the triple sunspot value of 33.94 years) ; the second is the
history of cycles in the long Flagstaff record and their agreement with
solar changes, thus throwing light on solar history; the third now to be
considered is the problem of prediction, which depends directly on the
climatic significance of the cycles previously discussed. Their climatic
character seems open to no reasonable doubt. Dating and prediction,
the backward look and the forward look, both depend on a knowledge
of the historic and geographical distribution of these cycles. In each
it is better to test out a small locality first, such as the Flagstaff region,
in order to avoid the complexities which arise over too large areas.
First caution: Interpretation differs with locality — The Arizona
trees respond closely to a definite weather element, rainfall, the most
important element in the prosperity of the country, but in the moist
areas this direct response decreases and even disappears. Hence, the
first caution in this process is that we must not assume relationships
similar to those in Arizona in any given place until that place has been
thoroughly investigated.
Second caution: Cycle changes not understood — The second
caution is very important. Until we know the physical cause of cycles
we can not say how long a mechanical repetition will last, for it may
break down at any time. This is well illustrated in the solar changes
shown in the long Flagstaff record. For hundreds of years the 11 -year
cycle was dominant, and then in the middle of the seventeenth century
it faded out and gave place to others, and we do not yet know the
reason. Until we know the reason we can not be sure it will not happen
again in the near future. Fortunately, we have the long-lived sequoia
for testing out secular changes. The best results from it at the present
time were given in a historical summary above.
Variable star analogy — There are several variable stars which are
dominated by different periods for irregular intervals of time. One of
the best is SS Cygni, which has been observed carefully for more than
30 years. It is not visible to the naked eye, but by telescopic observa-
tion has been found to rise suddenly from the twelfth to the eighth
magnitude at intervals of 50 or 60 days, more or less. Alternate
maxima are often of different length, reminding us of alternate sun-
spot maxima. Then without warning the period changes. Dr. Leon
Campbell, of Harvard College Observatory, has given me data and
for years I have tried to find the rule which governs these changes.
Third caution: Cycle subdivisions — The splitting of cycles that
may differ in different localities causes an uncertainty in place of
134 CLIMATIC CYCLES AND TREE-GROWTH
maximum or minimum. Consider, for example, a yearly curve of
temperature, low in winter and high in summer. Impress upon this,
as we have in Arizona, a summer rainy season which lowers the daily
averages and produces a slight summer minimum. The maximum is
split and driven each way, but owing to the lag in effects the higher
maximum comes in June. If a cycle is split we need to know whether
it is the maximum or minimum that changes. If only one changes we
get a double-crested curve and if both maximum and minimum split
we get a three-crested curve. In the 120 or 130 analyses of western
groups, certain cycles, obviously the same in each case, were sometimes
found single, sometimes double, and very rarely triple. Hence, it is
evident that the comparison of dates of maxima and minima is a
complicated process.
Fourth caution: Interference cycles — If some tree cycles arise,
as is possible, from an interference between some external short cycle,
say 10.5 months, and the annual seasons, then it is evident that the
time of maxima would not necessarily be the same in different geo-
graphical locations, for the time of favorable season is different. Com-
parison between the northern and southern hemispheres would be
needed to settle such cases, for similar conditions in the two hemi-
spheres would reverse the cycle. A single curve from Tasmania
suggests a split 35-year cycle, with major maximum about 1891 and
minor maximum in 1908. In the early Arizona curve the maximum
of the 35-year cycle was put about 1900, but in the recent study of
western groups this 35-year cycle is usually split into two 17-year
cycles whose maxima come in 1892 and 1909, thus agreeing with
Tasmania.
Fifth caution: Cycle centers — In the western zones it was found
that each zone had a homogeneous central area with scattering varia-
tions about it and that intermediate points, such as the Charleston
Mountains, partook of the variations of each zone near it. It is not
impossible that we shall find several more central homogeneous areas
from which certain typical effects spread out. It is evident that in
such conditions many intermediate places will have badly mixed
conditions, so that prediction of any kind will become additionally
difficult.
Flagstaff area synthetic curve — The mean curve covering the area
from the Grand Canyon to the Rim shows very excellent similarity
to the individual curves composing it, but many of the short periods
have disappeared and multiples of 7.0 years are left prominent, 21
years being by far the strongest. Residuals between the synthetic
curve and the real growth-curve show a 9.4-year cycle in the latter
part of the eighteenth century. Crests are too high (in the natural
curve) at 1793 and 1891 and the minima at 1847 and perhaps 1880
CYCLES 135
are too low to be accounted for by the synthetic curve. The 7-year
cycle was almost absent from 1880 to 1905. Yet on the whole there
is a good deal of similarity. The prolongation of the synthetic curve
shows a small depression near 1927 and deeper ones at 1942 and 1947.
The interval during the 1930 's has high ordinates with an unimportant
depression at 1933. It is possible that the 1947 depression may
resemble the one of 1847 and be rather extreme. During the 1950 's
the curve is again high. High crests occur at 1937 and 1953. It is not
expected that this is entirely right, but the details are given here in
order to assist ultimately in finding the true variations.
10
SUMMARY
The foregoing book includes the following descriptive matter :
1. The technique of collection and preparation of material brought
up to the latest development, with special studies of trees and rings.
2. New instruments constructed and used, namely, the tubular
borer, the automatic plotter, the longitudinal plotter, and the White
cyclograph (periodograph without the attachment for producing the
periodogram) ; the cyclogram is here definitely used in place of the
periodogram.
3. The collection of long tree-records including (a) sequoia groups
from Calaveras and Springville, (b) coast redwood groups from Santa
Cruz and Scotia, (c) a 640-year yellow pine, and (d) much archaeo-
logical material for constructing a very long yellow-pine growth record.
4. The collection and measurement of 305 yellow-pine ring records
in 42 groups, from 10 western mountain states, representing the area
from the eastern slope of the Rockies to the Pacific coast and extending
from the Mexican border to the latitude of the Columbia River.
Practically all these trees were standardized individually before obtain-
ing group averages.
The results obtained and described are as follows :
1. All the sequoia groves from Calaveras to Springville give the
same climatic record and can be cross-identified throughout their
records; the northern groves are more complacent in ring- type.
2. The coast redwoods, carefully selected and most carefully com-
pared, could not be cross-identified and therefore are not used.
3. Ten-inch boring tests every 20 feet on a sequoia 265 feet long
and 15 feet in diameter, which fell in 1901, gave almost perfect simi-
larity throughout in the heartwood, but very considerable differences
in the water-soaked sapwood. The problem of change in ring-size
is opened. In living trees the change is probably very small and con-
nected with conservation of moisture, sometimes possibly retroactive
on the rings.
4. Topographic studies show that soil moisture is a strongly con-
trolling factor in ring-type, both in sequoia and yellow pine. Soil-
moisture gradient below the trees could be used as an indicator of ring
characters.
5. Trees at higher altitudes and at higher latitudes (than about
32° N.) show more complacent rings.
6. Close grouping in the pines and sequoias produces objectionable
alterations in rings only under extreme conditions and can be avoided
with trifling care in selection of trees.
7. Deficient soil-depths and denudation of soil about trees pro-
duce intensely compressed outer rings in the pines of dry areas, and
this character can be recognized in much prehistoric material.
136
SUMMARY 137
8. Mean sensitivity is a good indicator of climatic correlation, but
it is strongly affected by injuries to the tree.
9. Average ring-size, doubling, changing, and other characters of
rings can be used as indicators in judging the surroundings, and
especially the climates, of prehistoric and geologic times.
10. The Prescott correlation between rainfall and tree-growth is
continued and a similar correlation is found between the Flagstaff
trees and the winter rainfall recorded there, which, in turn, closely
resembles California precipitation. A close correlation is also found
between carefully selected (dry ground) sequoias and San Francisco
rainfall.
11. By comparison of smoothed curves, three western centers
appear; Pike's Peak, Flagstaff, and Sierra Nevada. The Pike's Peak
area as worked out covers the eastern slope of the mountain; the Flag-
staff area extends from the Grand Canyon to the Rim and Cibecue,
175 miles; the Sierra Nevada area extends from the Calaveras Grove
and even farther north to Mount Wilson and farther south, 500 miles.
In each of these the curves of growth are homogeneous, and at points
between these major centers, such as Charleston Mountain or Aztec,
mixed effects are found.
12. Dating comparisons of cycles in 200-year curves show 75 per
cent resemblance in local curves of individual trees, and 50 per cent
resemblance between Arizona pines and California sequoias, by large
groups of trees. Practical identity of cycles in yellow-pine groups is
found across 200 miles between Flagstaff and northwest New Mexico.
13. The cycles found in the yellow pines of the western zones
emphasize the approximate simple fractions of 34 or 35 years, with 11
and 14 years dominating on the coast, 14 and 21 years in Arizona, and
10 and 11 (or 23) in the Rockies; the coast is deficient in the 20-year
variations (the separation of 19, 20, and 21 is not yet fully determined
in these zones); Arizona has less of the 11, 23 year cycles and the
Rockies are short in the 14, 28 year cycles; they, however, show the
8.6- and 17.5-year cycles better than the other zones.
14. A sequoia arcigram (cycle summary over an area) shows a
little more of the Arizona character in the sequoias than in the yellow
pines of that region.
15. The long Flagstaff record, from 1300 to 1925, perhaps the
best in the three zones for rainfall history, gives cycles which check
with the known solar record. From them we get a solar period of
11.30 years lasting for 600 years, but with an interruption from 1630
to 1850; we get also a group of 7, 14, and 21 year cycles beginning
near 1660 and well established after 1700. The 21-year cycle has
dominated Arizona tree-growth for 200 years. A 9.4-year cycle
shows in the late 1700 's, when the sunspot cycle was of that length.
The 7-year cycle was less active from 1880 to 1905 (in the Flagstaff
area mean curve). Growth maxima occur at observed sunspot minima.
16. Wet and dry climate effects in trees in relation to the solar
cycle are confirmed.
138 CLIMATIC CYCLES AND TREE-GROWTH
17. Provisional results indicate that the 11-year cycle appears in
the long sequoia records at 1300 to 1100 b. c, 300 b. c, a. d. 35 to
240; 375 to 475; 600 to 650; 800 to 900 and 1250 onward, with the
interruption following 1700.
18. The dry years in the Flagstaff area tree-growth analyze best
on 14- and 21-year cycles with major droughts at about 150-year
intervals and minor droughts at 40- or 50-year intervals.
19. The extension of the cycles observed in the last 200 years in
the Flagstaff area indicates possible large growth of trees in the 1930 's
and 1950*8, with depressions in the early and late 1940 's.
It is recognized that much of this work is new and that time is
needed to test and improve it, but it is hoped that these preliminary
results are not greatly in error.
APPENDIX
TABLES OF GROUP AVERAGES, STANDARDIZED
ARIZONA ZONE
Flagstaff (FL), Appendix, Volume I, Page 113
Flagstaff University Section (FLU), 500-year trees
A.D.
0
1
2
3
4
5
6
7
8
9
1700
0.98
1.07
1.00
0.86
1.03
1.22
1.40
0.77
0.69
0.85
1710
1.01
0.79
0.85
0.85
1.05
1.08
1.17
1.08
1.20
1.03
1720
1.27
1.04
0.93
1.34
1.00
1.22
1.57
0.80
0.94
0.64
1730
1.04
0.84
0.95
0.85
0.90
0.51
0.84
0.76
1.14
0.76
1740
0.93
1.11
1.11
1.08
1.13
1.11
1.39
1.09
0.64
1.21
1750
0.91
0.75
0.45
0.69
0.61
0.72
0.65
0.83
1.15
0.98
1760
1.05
1.10
1.37
1.24
1.54
1.23
0.79
0.96
0.82
0.76
1770
0.95
1.12
0.88
0.67
0.85
0.97
0.88
0.97
0.60
0.60
1780
0.62
0.72
0.51
1.01
1.32
0.62
0.70
1.11
0.95
0.67
1790
0.90
0.86
0.99
1.21
1.20
0.92
0.90
0.98
0.79
0.95
1800
0.76
0.56
0.97
0.85
0.61
0.77
0.99
0.69
0.86
0.96
1810
0.98
1.18
1.09
0.49
0.94
0.86
0.80
0.67
0.60
0.85
1820
0.69
0.61
0.53
0.62
0.64
0.92
1.12
0.87
0.96
0.85
1830
0.96
0.82
0.98
1.02
0.70
0.80
0.80
0.80
0.76
0.92
1840
1.00
0.70
0.72
0.82
0.74
0.67
0.58
0.40
0.80
0.91
1850
1.00
0.77
1.13
1.29
1.09
1.02
1.06
0.84
1.11
0.88
1860
0.98
0.92
1.07
0.78
0.70
0.86
1.04
1.02
1.33
1.04
1870
1.14
0.84
0.94
0.82
1.05
1.06
0.72
0.70
0.85
0.75
1880
0.69
1.01
0.88
0.86
0.81
1.10
0.80
0.86
0.95
0.96
1890
1.12
1.12
0.98
1.36
1.21
1.05
1.34
1.18
1.26
0.95
1900
0.71
0.83
0.80
0.79
0.63
1.14
1.24
1.28
1.64
1.80
1910
1.68
1.66
1.42
1.19
1.42
1.36
1.36
1.00
0.95
Fort Valley (FV), 6 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1680
0.50
0.83
0.85
0.90
1690
6.86
6.82
6.90
1.06
0.85
6.76
0.89
1.43
1.30
1.61
1700
1.24
1.35
0.97
1.05
0.88
0.70
1.20
1.36
1.28
1.61
1710
1.91
1.56
1.54
1.71
1.66
1.54
1.04
1.48
1.59 +
1.73
1720
1.90
1.33
1.12
1.29
0.95
1.69 +
1.65
0.92
0.83
0.43
1730
1.04
0.82
1.48
1.44
1.18
0.38
1.11
0.90
1.04
0.81
1740
1.33
1.15
0.88
1.54
1.64
1.84
1.98
1.20
0.52
1.26
1750
0.77
0.85
0.45
0.79
0.95
0.83
0.84
0.87 +
1.28
1.03
1760
1.30
1.36
1.33
0.76
1.46
1.07
1.29
1.10
1.01
10.5
1770
1.05
1.50
1.48
0.69 +
0.83
1.03
1.04
0.81
0.48
0.85
1780
0.47
0.60
0.38
0.87
1.28
1.06
1.55
1.93
1.29
1.32
1790
1.16
1.12
1.17
1.62
1.43
1.17
0.64
0.95
0.77
1.34
1800
0.78
0.81
1.27
1.05
0.98
0.82
1.04
0.93
0.84
1.01
1810
0.88
1.01
0.94
0.44
0.51
0.76
0.79
0.65
0.58
0.97
1820
0.72
0.71
0.56
0.66
0.81
1.09
1.47 +
1.17
1.39
0.75
1830
0.92
1.15
1.32
1.37
1.30
1.46
0.83 +
0.97 +
1.21
1.10
1840
1.03
0.54
0.57
0.49
0.81
0.65
0.57
0.36
0.83
1.07
1850
1.14
0.58
1.18
1.17
1.24
1.19
0.78
0.74
1.08-
0.79
1860
0.92 +
0.96
1.09
0.76
0.66
0.87-
1.55
1.38
1.90
1.26
1870
1.30
1.10
1.26
1.24
1.53
1.17
0.87
0.81
0.91
0.37
1880
0.73
0.65
0.76
0.75
0.57
0.80
0.76
0.75
1.06
1.25
1890
1.14
1.01
1.07
1.09
0.94
0.67
0.89
0.93
1.14
0.80
1900
1.02 +
1.43
1.03
1.49 +
1.05
1.58
1.62
1.94
2.30
2.19
1910
1.49 +
1.25
1.39
1.05 +
1.30
1.20
1.57
1.54
0.95
1.80
1920
0.90
....
139
140
CLIMATIC CYCLES AND TREE-GROWTH
Flagstaff High (FLH), 10 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1630
. . • •
....
....
....
4.60
3.80
2.90
1640
3.60
4.40
1.70
2.50
3.00
2.70
8.50
3.80
3.00
3.50
1650
4.30
4.00
3.80
4.20
3.50
4.20
3.90
2.50
2.00
2.30
1660
1.20
0.30
1.00
0.90
0.80
0.80
0.80
0.50
0.70
0.50
1670
0.50
0.60
1.00
1.00
1.10
0.60
0.90
1.10
2.10
1.50
1680
1.80
1.70
1.80
2.50
3.30
2.40
1.90?
2.90
2.00
2.50
1690
2.20
1.50
2.30
1.70
1.60
1.80
1.50
1.30
1.40
2.20
1700
1.70
1.60
1.40
0.90
1.60
2.10
1.60
1.40
1.20
2.00
1710
2.20
1.20
1.20
1.30
1.40
1.40
1.40
0.90
1.10
1.40
1720
1.40
1.30
1.20
1.30
1.20
1.00
1.40
1.60
1.30
1.40
1730
1.30
1.30
1.40
1.40
1.10
0.70
1.20
1.00
1.30
0.90
1740
0.40
1.00
2.00
1.00
1.00
1.10
1.10
1.00
0.50
0.90
1750
0.70
1.10
0.90
1.00
0.80
0.70
1.00
0.90
0.60
0.80
1760
0.80
0.80
0.90
0.80
0.70
0.70
0.80
0.80
0.70
0.70
1770
1.15
2.10
2.55
1.70
2.15
2.15
1.65
1.90
2.05
1.50
1780
1.97
1.93
1.83
2.53
2.37
2.07
2.26
2.63
1.97
2.23
1790
2.40
3.08
2.43
1.83
2.08
1.55
2.12
2.33
2.10
2.37
1800
2.32
2.21
2.14
2.40
2.31
2.09
2.51
1.99
2.21
2.29
1810
2.27
2.04
2.11
1.40
1.87
1.41
1.36
1.44
1.43
1.63
1820
1.51
1.36
1.11
1.36
1.57
1.74
1.86
1.27
1.24
1.53
1830
1.57
1.40
1.67
1.23
1.84
1.47
1.24
1.68
1.73
1.84
1840
1.95
1.40
1.16
1.61
2.08
1.84
1.67
1.61
1.43
1.79
1850
1.58
2.03
2.17
2.45
1.80
2.00
1.94
2.49
2.41
1.69
1860
2.18
1.79
1.87
1.85
1.71
1.87
1.45
1.72
1.92
2.18
1870
2.25
2.01
1.63
2.05
1.58
2.10
1.62
1.81
1.85
2.27
1880
1.20
1.60
1.53
1.81
1.49
1.76
1.61
1.80
1.74
1.92
1890
2.04
1.72
1.94
1.58
1.80
1.85
1.03
1.31
1.45
1.09
1900
1.23
1.18
1.20
1.49
1.55
1.25
1.42
1.74
1.95
1.99
1910
1.87
1.62
1.60
1.70
1.75
1.50
1.22
1.33
1.29
1.18
1920
1.18
1.06
1.23
1.12
0.52
.... |
Flagstaff Shadow (SH), 6 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1710
4.80
6.10
5.40
1720
5.90
3.60
4.00
6.90
2.60
3.80
4.10
3.30
3.50
2.00
1730
3.90
2.20
2.60
2.70
4.50
1.20
2.50
1.30
0.40
1.10
1740
2.30
2.10
2.10
3.90
4.30
4.10
4.60
3.70
1.00
3.90
1750
2.20
2.30
0.50
1.30
2.90
2.50
3.50
3.00
3.90
2.95
1760
2.60
1.85
2.40
1.20
3.05
2.45
2.85
1.95
2.20
1.95
1770
1.95
1.65
1.76
0.45
0.80
1.20
1.65
1.00
0.70
0.50
1780
0.45
1.05
1.73
1.33
2.00
0.77
0.53
1.80
0.70
1.43
1790
0.83
1.53
2.23
3.33
2.23
2.45
1.80
2.08
1.33
2.30
1800
0.80
0.83
1.45
0.43
1.03
0.70
1.33
1.23
1.78
1.30
1810
1.53
1.70
1.85
0.50
0.55
0.90
1.62
1.15
0.75
10.8
1820
0.30
1.40
0.62
0.70
1.60
1.80
2.15
2.38
2.76
1.66
1830
2.52
2.45
2.45
2.20
2.18
2.23
1.78
1.55
2.15
2.55
1840
2.15
1.30
1.63
1.38
1.98
1.53
0.65
0.75
1.48
1.60
1850
1.98
1.45
2.25
2.00
1.80
1.80
1.32
0.58
0.80
0.75
1860
1.13
1.35
1.55
1.13
1.08
1.35
2.50
2.75
3.02
2.70
1870
2.23
1.50
1.13
0.63
0.87
0.97
0.65
0.60
0.72
0.60
1880
0.42
0.60
0.75
1.30
1.52
1.98
1.16
1.12
1.52
1.54
1890
1.78
1.76
1.74
1.68
1.60
1.58
0.74
1.10
1.12
0.68
1900
0.70
0.68
0.32
1.38
0.94
1.40
2.48
3.02
2.90
3.28
1910
2.84
2.40
2.02
1.32
2.08
2.06
2.15
1.38
2.06
2.76
1920
2.40
2.02
2.04
1.76
*1.28
....
....
* Incomplete.
APPENDIX
141
Flagstaff Northeast (NE), 4 trees
(Dates prior to 1685 marked "doubtful")
A.D.
0
1
2
3
4
5
6
7
8
9
1670
1.10
1.08
2.70
1680
2.55
1.33
1.83
0.42
1.05
i.io
2.05
1.90
1.90
1690
1.15
1.92
2.24
2.22
1.60
1.60
0.82
0.65
1.68
1.40
1700
0.45
2.20
0.87
0.38
0.68
1.05
0.55
0.83
0.42
0.55
1710
1.20
1.15
1.50
1.65
1.75
1.95
2.30
2.50
3.48
4.70
1720
4.45
2.40
0.95
1.78
1.46
2.37
4.23
2.76
2.29
1.14
1730
1.13
1.38
1.49
0.56
1.37
0.39
1.26
0.74
1.36
1.02
1740
1.70
1.89
1.08
2.31
2.09
2.72
3.83
3.35
1.10
2.11
1750
1.47
1.53
0.83
1.49
1.82
0.68
1.80
2.03
3.02
3.53
1760
3.42
1.77
2.31
1.18
1.40
1.85
1.98
1.66
1.79
1.39
1770
1.21
1.51
0.90
0.64
0.79
0.93
1.41
1.34
0.75
0.91
1780
0.79
0.73
0.89
1.75
1.33
0.54
0.62
1.27
0.85
0.77
1790
1.00
1.24
1.56
2.12
1.84
1.67
1.83
1.41
0.80
1.08
1800
0.63
0.41
0.47
0.45
1.08
0.46
1.02
0.89
1.12
1.14
1810
1.22
1.55
1.37
0.60
1.44
1.81
1.67
1.67
1.43
1.36
1820
0.87
1.15
0.91
1.31
1.54
1.53
1.98
1.63
2.01
1.21
1830
1.64
1.61
1.59
1.64
0.89
1.38
1.18
1.02
1.59
1.71
1840
1.88
1.46
0.68
1.14
1.55
0.31
0.61
0.12
0.85
0.87
1850
1.06
0.77
1.09
1.07
0.71
0.90
0.74
0.09
0.77
0.40
1860
0.63
0.60
0.58
0.49
0.26
0.57
0.65
0.83
1.20
1.19
1870
0.77
0.40
0.43
0.57
0.62
0.80
0.61
0.26
0.35
0.25
1880
0.33
0.10
0.35
0.29
0.43
0.77
0.63
0.68
0.71
0.72
1890
0.97
0.85
1.12
0.85
1.07
0.95
0.59
0.84
0.70
0.35
1900
0.50
0.41
0.13
0.48
0.13
0.66
0.83
1.32
1.38
1.62
1910
1.51
1.74
1.35
0.94
1.24
1.11
1.12
1.20
1.22
1.29
1920
1.38
1.25
1.27
Grand Canyon (GC), 7 trees
A.D.
0
1
2
3
4
5
6
7
8
,
1710
1.25
1.55
2.95
1.20
1720
2.66
2.15
6.60
1.90
6.60
6.90
1.50
1.25
0.95
0.50
1730
0.80
1.15
2.00
1.10
0.60
0.30
0.60
0.45
1.10
0.40
1740
1.25
1.30
0.90
1.30
1.05
1.20
2.05
2.12
0.67
1.90
1750
1.25
0.92
0.35
0.47
0.48
0.47
0.67
0.82
1.27
0.95
1760
1.15
0.92
1.28
0.93
1.83
1.03
1.13
1.35
1.60
0.93
1770
0.77
1.50
1.27
0.58
0.80
0.90
1.30
0.95
0.38
0.92
1780
1.23
0.93
0.50
0.98
1.50
0.53
0.95
1.42
0.78
0.93
1790
0.80
1.13
0.95
2.00
0.76
1.22
0.84
0.70
0.53
1.09
1800
0.45
0.45
0.81
0.44
0.71
0.62
0.44
0.78
0.81
0.64
1810
0.30
0.74
0.96
0.24
0.52
0.50
0.73
0.65
0.31
0.52
1820
0.28
0.61
0.25
0.39
0.52
0.86
0.89
0.87
1.03
0.36
1830
0.49
0.74
0.68
0.85
0.60
0.87
0.54
0.86
0.81
1.11
1840
1.16
0.69
0.42
0.44
0.75
0.13
0.23
0.07
0.55
0.83
1850
0.89
0.61
0.74
0.74
0.87
0.96
0.79 +
0.66
0.84
0.49
1860
0.51
0.44
0.83
0.52
0.31
0.63
1.18
0.85
1.66
1.33
1870
0.80
0.66-
0.61
0.45
0.90
0.88
0.55
0.48
0.79
0.27
1880
0.28
0.25
0.30
0.35
0.69 +
1.08
0.97
0.50
1.16 +
1.18
1890
1.68
1.66 +
1.66
1.41
0.84
1.17
0.32 +
0.86
0.79 +
0.16 +
1900
0.28 +
0.35
0.37
0.67
0.06
0.61
1.01
1.32
1.23
2.17
1910
1.08
1.39 +
1.07
0.67
1.19
1.07
1.14
0.82
0.39 +
0.89
142
CLIMATIC CYCLES AND TREE-GROWTH
Dixie Forest (DF), 10 trees
A.D.
0
1
2
3
4
S
6
7
8
9
1.26
1610
• • • •
• • • •
• . • •
• •
1.56
1.62
2.20
1620
1.26
2.26
1.06
1.76
i.oo
i.Yo
1.95
1.85
2.20
2.40
1630
1.85
1.50
1.40
2.50
2.30
2.35
2.60
1.65
2.15
1.40
1640
2.20
1.75
2.25
2.30
2.50
2.20
1.65
2.35
1.85
2.10
1650
2.30
3.10
3.75
1.35
2.60
1.50
2.05
2.20
2.45
2.25
1660
2.28
2.70
2.70
2.05
2.45
1.80
1.85
2.40
1.80
1.95
1670
1.30
2.40
2.45
2.10
2.35
1.65
1.50
2.10
1.75
1.75
1680
2.10
2.15
1.50
2.90
1.60
2.50
1.40
2.10
1.65
1.75
1690
1.15
1.65
1.80
1.65
2.10
2.15
1.75
1.55
1.65
1.95
1700
2.10
1.95
1.85
1.30
1.65
2.10
2.15
0.70
0.55
0.95
1710
1.30
1.55
0.95
0.85
1.10
1.05
1.42
1.35
1.52
1.70
1720
2.10
1.85
1.87
1.80
2.37
1.77
2.31
1.74
1.79
1.02
1730
1.56
1.71
1.21
1.50
1.44
0.35
1.32
1.09
1.35
1.24
1740
1.52
1.56
1.14
1.40
1.45
1.51
1.76
1.76
1.35
1.94
1750
1.26
1.46
0.89
1.21
1.19
1.24
1.02
1.41
1.15
1.11
1760
1.24
1.15
1.09
0.77
0.89
1.13
1.34
1.27
1.11
1.27
1770
1.36
1.30
1.16
1.40
1.46
1.46
1.40
1.17
1.39
1.33
1780
1.38
1.21
1.01
1.22
1.78
1.12
1.14
1.50
1.13
1.68
1790
1.46
1.45
1.62
1.36
1.56
1.17
1.26
1.36
1.18
1.42
1800
1.24
1.44
1.60
1.06
1.24
1.43
1.27
1.24
1.28
1.47
1810
1.32
1.52
1.27
1.16
1.34
1.24
1.30
1.28
1.27
1.30
1820
0.96
1.30
0.94
0.92
0.97
1.26
1.20
1.22
1.53
1.40
1830
1.23
1.48
1.70
1.60
1.16
1.22
1.01
1.20
0.98
1.18
1840
1.33
0.98
0.90
1.04
1.18
1.03
1.17
0.94
1.03
1.53
1850
1.34
1.04
1.12
1.30
1.26
1.35
1.14
1.26
1.22
1.18
1860
1.15
1.02
1.34
1.37
0.91
1.02
1.43
1.41
1.45
1.40
1870
1.61
1.22
1.20
1.10
1.38
1.34
1.00
1.30
1.14
0.68
1880
0.85
0.97
1.17
1.18
1.19
1.58
1.14
1.44
1.42
1.16
1890
1.30
1.45
1.43
1.37
1.52
1.40
1.34
1.43
1.50
1.34
1900
1.30
1.57
1.34
1.38
1.59
1.46
1.59
1.79
1.78
1.66
1910
1.79
1.64
1.60
1.55
1.63
1.61
1.67
1.39
1.34
1.44
1920
1.17
1.21
1.35
1.00
Rim High (RH)
2 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1690
0.98
1.22
1.58
1700
1.20
1.26
1.05
1.22
0.75
0.98
i!o4
0.55
0.79
1.31
1710
1.42
0.66
0.92
1.19
1.12
1.17
0.97
0.96
1.22
0.98
1720
1.26
0.92
0.60
1.13
0.90
0.82
1.09
0.53
0.70
0.55
1730
0.69
0.60
0.78
0.47
1.00
0.37
0.84
0.74
0.66
0.53
1740
1.03
0.63
0.72
0.80
0.56
0.86
1.12
0.93
0.25
0.79
1750
0.91
0.66
0.40
0.65
0.92
1.04
0.86
0.75
0.86
1.15
1760
1.22
0.70
0.90
0.90
1.55
1.30
1.50
1.80
1.20
1.00
1770
1.45
1.40
0.80
0.90
0.85
0.60
1.00
0.85
1.06
0.83
1780
1.00
1.10
0.63
0.82
1.69
0.80
1.20
1.40
1.08
0.79
1790
0.71
0.79
0.88
1.20
1.01
0.88
0.70
0.65
0.53
0.70
1800
0.65
0.60
0.98
0.93
1.00
1.18
0.75
0.96
1.00
0.92
1810
0.81
1.12
0.87
0.68
0.65
0.90
0.83
0.55
0.69
0.51
1820
0.56
0.55
0.51
0.41
0.45
0.57
0.63
0.48
0.48
0.35
1830
0.52
0.46
0.48
0.45
0.65
0.58
0.70
0.70
0.80
0.73
1840
0.72
0.44
0.57
0.68
0.71
0.29
0.70
0.42
0.68
0.80
1850
0.70
0.70
0.91
0.63
0.70
0.55
0.78
0.61
0.76
0.72
1860
0.72
0.80
0.65
0.66
0.68
0.82
1.20
0.76
1.10
0.48
1870
0.78
0.76
0.73
0.43
0.83
0.83
0.72
0.81
0.98
0.65
1880
0.78
0.80
0.66
0.80
0.82
0.72
0.52
0.80
0.82
0.70
1890
0.85
0.63
0.59
1.02
0.50
0.62
0.88
0.79
0.78
0.78
1900
0.50
0.75
0.48
0.76
0.25
0.75
0.76
0.84
1.06
0.90
1910
0.70
0.80
0.75
0.58
0.80
0.68
0.62
0.82
0.52
0.66
1920
0.59
0.76
0.55
....
APPENDIX
143
Rim Low (RL) ,
2 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1770
1.00
1.43
1.43
0.98
1.02
1.10
1.35
1.27
0.84
0.71
1780
0.68
0.75
0.51
0.77
1.49
0.92
0.95
1.35
0.97
0.99
1790
0.93
1.27
1.14
1.69
1.00
0.84
0.70
0.95
0.65
0.87
1800
0.72
0.71
0.84
0.50
0.79
0.68
0.83
1.00
1.05
0.95
1810
0.49
1.18
1.16
0.56
0.94
1.13
0.65
0.85
0.77
0.41
1820
0.12
0.70
0.36
0.28
0.85
0.75
1.13
1.43
1.50
1.53
1830
1.29
0.61
1.50
1.22
0.86
1.06
1.08
0.82
0.71
1.52
1840
1.46
0.78
0.78
0.84
0.89
0.62
0.63
0.27
0.83
0.75
1850
0.60
0.78
1.32
0.85
0.73
0.96
0.55
0.28
0.77
0.38
1860
0.58
0.44
0.62
0.39
0.24
0.70
0.60
0.90
1.41
1.44
1870
0.95
0.74
0.66
0.48
0.39
0.86
0.70
0.68
0.93
0.32
1880
0.58
0.41
0.35
0.45
0.92
1.38
0.92
0.78
1.36
1.08
1890
1.25
1.42
0.90
1.26
0.39
1.19
0.44
0.84
0.84
0.60
1900
0.36
0.79
0.06
0.42
0.08
0.95
0.98
1.31
1.85
1.49
1910
1.31
1.41
1.32
0.63
1.45
1.01
1.12
1.28
1.05
1.22
1920
1.33
1.02
....
Cibecue (J), 5 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1650
1.02
1.43
1.10
0.75
1.13
0.86
0.43
0.66
1660
0.80
1.09
1.12
1.40
1.33
1.37
1.11
1.00
0.75
0.63
1670
0.21
1.02
0.77
1.00
0.88
0.80
0.90
0.87
0.67
0.95
1680
1.30
1.43
0.92
1.43
0.27
0.13
1.20
1.40
1.60
1.55
1690
1.66
1.20
1.60
1.05
1.80
1.70
1.00
1.70
0.93
2.83
1700
1.03
0.98
1.24
0.87
1.13
1.35
1.34
0.35
0.55
0.72
1710
1.24
0.68
0.71
0.69
1.35
0.62
0.40
0.90
1.17
0.96
1720
1.10
1.02
0.66
1.03
0.44
0.95
1.15
0.90
0.75
0.33
1730
0.73
0.41
0.90
0.48
0.85
0.18
0.72
0.83
1.10
0.53
1740
1.28
1.16
0.73
1.00
0.82
1.11
1.35
1.62
0.80
1.96
1750
1.33
0.58
0.18
0.40
0.65
0.45
0.48
0.38
0.68
0.72
1760
0.66
0.60
1.18
0.40
1.59
0.81
1.38
0.92
1.16
0.93
1770
0.99
1.22
0.96
0.29
0.86
0.82
0.81
0.62
0.39
0.58
1780
0.27
0.36
0.12
0.59
1.08
0.43
0.69
1.10
0.67
0.59
1790
0.52
0.82
1.08
1.77
0.86
1.06
0.89
0.43
0.52
0.61
1800
0.38
0.27
0.43
0.12
0.47
0.29
0.36
0.44
0.51
0.47
1810
0.29
0.50
0.47
0.39
0.41
0.53
0.68
0.58
0.40
0.12
1820
0.04
0.34
0.03
0.28
0.28
0.48
0.33
0.13
0.72
0.44
1830
0.38
0.42
0.43
0.68
0.62
0.50
0.52
0.44
0.62
0.91
1840
0.68
0.42
0.40
0.33
0.70
0.20
0.20
0.12
0.15
0.46
1850
0.55
0.45
0.82
0.73
0.43
0.47
0.88
0.57
0.88
0.55
1860
0.90
0.49
1.03
0.77
0.26
0.92
0.91
1.01
1.28
1.23
1870
0.84
0.38
0.83
0.38
0.47
0.78
0.57
0.49
0.44
0.60
1880
0.43
0.41
0.42
0.49
0.57
0.66 +
0.64
0.46
0.57
0.59
1890
0.90
0.82
0.78
0.41
0.20
0.34
0.44
0.40
0.40
0.37
1900
0.12
0.35
0.10
0.21
0.12
0.47
0.71
0.76
0.91
1.01
1910
0.76
1.04
0.65
0.42
1.03
0.84
0.96
1.17
0.90
0.88
1920
0.67
....
144
CLIMATIC CYCLES AND TREE-GROWTH
Pined (PNL),
S trees
A.D.
0
1
2
3
4
5
6
7
8
9
1760
0.73
1.10
1.35
0.72
1.30
0.92
0.65
0.60
0.90
0.80
1770
0.80
1.15
0.80
0.45
0.55
0.70
0.42
0.50
0.65
0.60
1780
0.63
0.55
0.35
0.58
0.68
0.63
0.78
1.05
0.55
0.92
1790
0.75
0.58
0.73
0.60
0.68
0.55
0.68
0.65
0.75
0.98
1800
0.95
0.75
0.95
0.85
0.78
0.96
0.69
0.64
0.86
0.93
1810
0.67
0.46
0.50
0.42
0.59
0.56
0.47
0.62
0.44
0.38
1820
0.27
0.69
0.36
0.33
1.08
1.11
0.98
1.00
1.23
0.88
1830
1.36
0.92
1.37
1.37
0.83
0.90
0.87
0.69
0.90
1.14
1840
0.89
0.47
0.84
1.09
1.36
0.84
0.90
0.44
1.15
1.00
1850
1.35
1.52
2.17
1.11
0.94
0.84
0.86
0.79
1.07
0.73
1860
0.91
0.75
0.94
0.42
0.33
0.80
1.15
0.55
0.95
0.99
1870
0.57
0.43
0.56
0.44
0.49
0.88
1.03
0.78
0.95
0.90
1880
0.48
0.95
0.80
0.60
0.85
0.87
0.50
0.64
0.48
0.41
1890
0.87
0.79
0.36
0.51
0.47
0.46
0.57
1.07
0.83
1.01
1900
0.015
0.36
0.73
0.56
0.42
1.09
1.28
1.22
2.14
2.13
1910
0.66
0.68
0.64
0.40
0.54
0.68
0.53
0.41
0.27
0.32
1920
0.36
0.47
0.43
0.23
Santa Catalina (SO, 8 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1560
1.02
1.46
1.85
1570
1.47
1.67
6.87
1.20
6.98
1.42
1.42
1.27
1.03
0.88
1580
1.08
1.63
1.46
1.10
1.11
1.60
1.50
1.20
1.20
1.30
1590
0.68
0.95
1.17
1.16
1.04
1.10
1.11
1.40
1.22
1.14
1600
1.75
1.44
1.51
1.20
0.93
1.38
0.91
1.45
1.29
1.24
1610
1.60
1.10
0.80
1.23
1.21
0.87
1.39
1.19
0.98
1.43
1620
1.31
0.85
0.91
0.81
0.68
0.47
0.19
0.26
0.30
0.39
1630
0.65
0.78
1.30
2.02
1.73
1.10
1.56
1.16
1.03
1.35
1640
1.21
0.90
0.96
0.72
0.68
0.83
1.07
1.65
1.53
1.00
1650
1.81
0.67
0.72
0.89
1.00
1.40
1.00
0.59
0.65
0.61
1660
0.34
0.65
0.41
0.51
0.55
0.80
1.34
1.04
2.02
1.86
1670
1.80
1.74
1.48
1.49
1.19
1.52
1.54
1.25
1.71
0.94
1680
0.71
1.51
1.05
1.10
1.15
0.87
1.17
1.22
1.44
0.96
1690
1.48
1.13
1.15
1.06
0.74
0.48
0.78
1.06
0.43
1.08
1700
0.89
0.80
1.07
1.12
1.09
0.81
0.79
0.85
0.99
0.96
1710
0.82
0.58
0.70
0.85
0.65
0.59
0.48
0.59
0.68
0.85
1720
0.66
0.84
0.78
0.79
0.84
0.81
0.83
0.91
0.83
1.46
1730
1.36
1.51
1.51 +
1.39
1.11
1.00
1.06
1.20
1.17
0.88
1740
0.81
1.21
0.95
1.08
0.77
0.77
0.80
0.76
0.41
0.73
1750
0.74-
0.68 +
0.51
0.56
0.80
0.91
0.82
0.98
0.96
1.01
1760
0.86
1.06
0.98
1.03
1.18
1.16
1.12
1.10
1.01
0.96
1770
1.09
1.02
1.04
0.98
1.07
1.14
1.14
1.19
1.38
1.09
1780
1.17
1.32
1.01
1.19
1.18
1.13
0.79 +
0.78-
0.75
0.65
1790
0.72
0.97
1.29
1.29
1.39
1.13
0.87
0.95
0.83
0.99
1800
1.20
1.11
0.95
0.99 +
1.09
1.21
1.41
1.21
1.04
1.37
1810
1.29
1.21
1.04
1.10
1.32
1.33
1.32
1.03
0.80
0.73
1820
0.85
0.74
0.65
0.83
0.84
0.91
1.08
1.01
0.90
1.12
1830
1.28
0.82
1.24
0.82
0.56
0.94
0.67
0.82
0.93
1.08
1840
1.14
0.94
0.94
1.34
1.59
1.80
1.20
1.42
1.38
1.08
1850
1.19
0.72
0.96
1.16
0.82
0.51
0.78
0.97
0.95-
0.69-
1860
1.13
1.07
0.74
0.89
0.70
0.50
0.83
0.51
0.54
0.53
1870
0.64
0.74
0.89
0.79
0.77 +
0.97
0.89
0.80
1.13
1.35
1880
0.94 +
0.88
1.02
0.91
1.10
1.18
0.88
0.82
1.01
0.98
1890
0.95
0.68
0.74
0.96
0.81
0.80
0.88
0.70
1.09
0.89
1900
0.78
0.89
0.76
0.76
0.74
0.96
0.53
0.74 +
0.95
0.68
1910
0.46
0.57
0.58
0.62
0.83
0.45
0.65
0.79
0.52
0.75
1920
0.79 +
APPENDIX
145
Santa Rita (SR), 5 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1670
0.82
0.52
0.47
0.64
0.74
1.00
2.18
1.20
1.87
1.00
1680
1.07
1.20
1.09
0.95
1.14
1.11
1.13
1.41
1.43
0.85
1690
0.59
0.77
0.98
1.12
1.38
0.80
0.72
1.05
1.18
1.27
1700
1.00
1.20
1.00
1.58
1.30
1.04
0.91
0.85
1.12
1.14
1710
1.30
0.72
0.72
0.44
1.04
0.84
0.85
1.12
1.25
1.22
1720
1.31
1.06
1.06
1.10
1.40
1.18
1.51
0.61
1.20
1.02
1730
0.97
1.61
1.68
0.86
0.87
0.56
1.18
0.88
0.87
0.58
1740
0.86
0.78
1.03
1.93
1.74
1.21
1.42
1.70
0.62
0.46
1750
0.78
0.12
0.69
0.40
0.42
0.66
0.78
1.00
1.10
0.76
1760
1.08
1.22
0.66
1.11
1.01
0.79
1.04
1.04
1.13
0.98
1770
0.98
0.67
0.90
0.53
0.50
0.55
0.60
0.75
0.59
0.70
1780
0.80
0.67
1.02
0.90
1.10
0.70
0.62
0.81
1.01
0.99
1790
0.69
0.66
0.85
0.83
0.57
0.66
0.78
0.39
0.39
1.08
1800
0.56
0.23
0.77
1.03
1.18
1.28
1.11
1.22
0.87
1.30
1810
1.58
1.31
1.54
1.06
1.51
1.49
1.47
0.97
1.22
0.41
1820
0.61
0.62
0.68
0.82
0.95
0.89
1.50
1.42
1.45
1.32
1830
1.35
1.14
1.30
1.05
0.78
0.97
0.83
0.95
0.96
1.41
1840
1.53
0.84
0.62
1.12
1.55
1.32
1.05
0.39
0.58
0.78
1850
0.95 +
0.87
1.03
1.32
1.26
1.33
1.29
0.97
1.00
1.12
1860
1.23
1.17
0.86
0.81
0.72
0.85
0.79
0.68
0.94
0.98
1870
0.80
0.77
0.65
0.78
0.64
0.77
0.44
0.88 +
0.80
0.75
1880
0.53
1.02
1.22
1.19
1.04
1.05
0.46
0.54
0.92
0.76
1890
0.75
0.66
0.39 +
0.37
0.53
0.43
0.97
0.90
1.22
1.21
1900
0.77
0.91
0.63
1.13
0.71
1.24
1.09
1.25
1.39
1.13
1910
0.84
1.30
0.71
0.96
1.30
0.92
1.06
1.15
0.91
1.19
1920
0.84
0.62
ROCKY MOUNTAIN ZONE
Yellowstone (F), 5 trees
A.D.
0
1
2
3
4
5
6
!7
8
9
1690
1.00
1.16
1.16
0.88
0.66
1.02
0.77
1700
0.74
1.09
i.oo
1.12
0.98
1.06
0.95
0.79
1.00
1.29
1710
1.00
0.95
1.22
1.16
1.16
1.09
1.12
0.81
0.83
0.87
1720
0.89
0.87
0.80
1.06
0.97
1.00
0.95
1.06
1.26
1.23
1730
1.02
0.85
1.03
1.21
1.24
0.95
0.93
1.46
1.08
1.11
1740
1.00
1.15
1.03
0.85
0.75
1.05
1.13
1.17
1.20
1.18
1750
1.04
1.05
1.13
1.13
0.91
0.95
1.06
1.05
1.11
1.50
1760
1.36
0.98
0.98
1.11
1.01
1.11
1.01
1.25
1.37
1.35
1770
1.10
1.04
1.16
1.21
1.36
1.00
1.43
1.29
1.28
1.17
1780
1.43
1.00
0.87
0.86
0.97
0.78
0.94
1.16
1.03
1.29
1790
1.03
1.33
1.27
1.35
1.17
1.38
1.16
0.90
0.98
0.84
1800
1.00
0.94
1.00
0.91
1.10
0.93
0.89
0.75
1.03
0.79
1810
0.92
0.88
0.93
1.12
0.91
1.26
1.24
1.48
1.36
1.27
1820
1.40
1.12
1.04
0.96
1.02
0.96
1.15
1.33
1.11
1.13
1830
1.06
1.13
0.97
0.97
1.22
1.14
1.14
1.18
1.08
1.19
1840
1.04
1.35
1.47
1.78
1.55
1.10
1.32
1.02
0.94
1.04
1850
1.00
1.09
0.83
1.09
1.08
0.82
0.92
1.12
0.94
1.01
1860
1.13
1.37
1.01
1.10
0.87
0.83
1.04
1.00
1.15
0.98
1870
0.88
0.84
0.89
0.86
0.97
0.94
0.95
1.11
1.17
1.38
1880
1.12
1.17
1.20
0.75
1.05
1.09
1.09
1.12
1.26
1.15
1890
1.18
1.19
1.14
1.11
1.15
1.12
0.92
1.17
0.95
0.74
1900
1.03
0.96
0.74
0.83
0.83
0.98
0.77
0.90
1.02
0.98
1910
1.16
1.06
0.99
1.09
1.08
0.89
0.84
0.79
0.88
0.87
1920
0.87
146
CLIMATIC CYCLES AND TREE-GROWTH
Laramie, Wyoming (LW) , 3 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1750
1.95
1.20
0.55
0.35
0.65
0.80
1760
6.80
1.75
0.95
1.15
0.95
1.10
1.20
1.35
1.70
1.80
1770
0.90
1.35
1.00
0.80
1.05
1.20
1.20
0.50
1.50
1.50
1780
1.60
1.90
1.00
1.30
2.15
1.95
1.10
2.05
0.85
0.50
1790
1.40
1.30
1.15
1.70
2.00
1.25
1.20
0.30
0.45
1.60
1800
1.60
1.30
2.40
2.55
0.70
0.45
0.95
0.50
1.05
0.85
1810
1.30
1.25
1.05
1.05
1.10
1.00
1.05
1.20
1.00
1.25
1820
0.55
1.20
1.65
1.25
0.60
1.40
1.10
1.05
1.85
1.32
1830
0.96
0.90
0.94
1.12
1.16
1.37
1.58
1.78
1.69
1.84
1840
1.52
1.46
0.53
1.89
1.48
0.86
1.04
0.61
0.57
0.98
1850
1.05
0.72
1.14
1.56
1.09
0.59
0.59
0.59
1.16
1.31
1860
1.51
0.43
1.63
0.56
1.05
0.92
1.54
1.53
1.68
1.86
1870
1.63
0.91
1.75
1.31
0.66
1.56
1.36
0.65
1.63
0.92
1880
0.26
0.18
0.99
0.78
0.81
0.98
0.82
0.78
1.19
1.32
1890
1.03
1.83
1.24
0.93
0.93
1.21
1.08
1.46
1.42
1.21
1900
0.92
1.39
1.18
1.66
1.65
1.46
2.14
1.99
1.84
1.72
1910
1.43
1.18
1.31
1.74
1.46
1.93
1.00
1.55
1.48
0.58
1920
1.47
1.60
1.15
1.62
1.41
....
Clements' Pike's Peak (O, 8 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1770
....
....
1.41
1.86
1780
1.78
2.38
2.16
1.26
1.62
1.41
1.79
1.75
2.00
1.41
1790
2.27
2.20
2.56
2.52
2.42
2.36
2.46
1.91
1.83
1.23
1800
1.73
1.14
1.65
2.13
1.60
1.12
1.77
1.77
1.32
1.53
1810
1.60
1.55
1.92
1.65
1.31
1.71
1.95
1.68
1.53
1.71
1820
1.54
1.31
1.19
1.33
0.913
1.19
1.45
1.48
1.80
1.45
1830
1.34
1.68
1.08
1.41
1.49
1.72
1.83
1.95
2.31
2.08
1840
2.15
1.51
1.32
1.58
1.65
1.44
1.39
1.27
1.41
1.48
1850
1.25
0.567
1.49
1.47
1.76
1.17
0.92
1.35
1.81
1.07
1860
1.32
0.523
1.00
0.603
1.10
0.81
1.23
1.36
1.13
1.68
1870
1.08
0.863
1.09
1.08
1.06
1.22
1.18
1.08
1.37
0.937
1880
0.357
0.891
0.801
0.885
0.672
0.782
0.702
0.693
0.654
0.794
1890
0.57
0.705
0.734
0.439
0.581
0.720
0.594
0.796
0.970
0.351
1900
0.808
0.729
0.823
0.952
1.31
1.12
1.01
0.979
0.623
0.953
1910
0.917
0.668
0.842
0.95
1.08
1.18
0.994
0.734
0.67
0.81
Pike
s Peak, 11,600 Feet (PPT),
5 trees
A.D.
0
1
2
3
4
S
6
7
8
9
1730
0.81
0.78
0.70
0.79
0.82
0.91
1740
6.98
1.12
1.16
i.66
1.18
1.00
1.09
1.20
0.82
1.15
1750
1.18
1.06
1.09
1.10
1.05
0.92
1.08
0.98
1.08
1.36
1760
1.10
0.99
1.22
1.14
1.03
1.27
1.09
1.12
0.81
0.86
1770
0.75
0.86
0.97
0.74
0.93
0.84
0.97
0.95
0.93
1.02
1780
1.18
1.01
0.82
1.07
1.21
1.06
1.13
1.09
0.90
0.96
1790
1.02
0.90
1.18
0.95
1.05
0.96
1.03
1.05
1.15
1.16
1800
0.92
0.94
1.05
0.94
0.80
0.68
0.78
0.94
0.80
0.87
1810
1.01
0.95
0.92
0.85
0.99 +
0.79 +
0.89 +
1.07
0.83
0.97
1820
0.90
0.98
0.90
0.84
0.94
0.98
0.94
1.07
0.86
0.83
1830
0.96
0.91
1.04
1.11
1.07
0.94
0.73
1.06
0.90
0.80
1840
0.90
1.00
0.73
0.95
1.03
0.92
0.85
0.85
1.05
1.02
1850
0.88
0.45
0.81
0.88
0.90
0.92
0.97
0.89 +
0.84
0.85
1860
0.90
0.85
1.01
1.03
1.04
0.82
1.07
1.29
1.09
0.51
1870
1.47
1.21
1.17
1.29
1.36
1.40
1.57
1.27
1.32
1.17
1880
1.00
1.23
1.00
1.12
1.15
1.17
1.35
1.22
1.34
1.27
1890
1.02
1.01
1.01
0.79
0.84
0.77
1.01
1.02
1.07
0.76
1900
0.94
0.91
0.87
0.95
0.83
0.80
0.73
1.01
0.69
0.87
1910
1.01
0.77
0.85
0.86
0.79 +
0.78
0.95
0.91
1.02
0.95
1920
0.77
....
APPENDIX
147
Pike's Peak, 9,500 Feet (PPB), S trees
A.D.
0
1
2
3
4
5
6
7
8
9
1690
1.35
1.07
1.38
1.14
0.96
1.18
1.24
1700
1.26
1.39
1.04
1.17
1.06
1.18
1.22
1.21
1.26
1.08
1710
1.30
1.13
1.25
0.84
1.13
0.89 +
1.00
1.18
1.26
1.10
1720
1.13
1.18
1.22
1.17
1.15
0.86
0.87
0.66
0.84
0.92
1730
0.88
1.02
1.02
0.93
1.07
0.57
0.72
0.86
0.92
1.21
1740
1.32
1.27
0.68
1.14
0.99
0.65
1.19
1.22
0.74
0.85
1750
0.76
0.80
0.72
0.75
0.23
0.75
0.62
0.89 +
0.79
0.89
1760
0.67
0.77
0.99-
0.24
0.87
0.71
0.97
0.98
1.12
1.23
1770
1.49 +
1.37
1.57
1.84
1.67
1.17
1.16
1.31
1.12
1.23
1780
1.11
0.85
0.94
1.03
0.99
1.30
0.85
0.88
1.05
0.32
1790
1.04
0.81
0.98
1.06
1.18
1.09
1.04
1.07
1.17
0.96
1800
1.20
0.80
1.27
0.82
0.96
0.75
0.71
0.86
0.69
0.74
1810
0.87
0.75
0.88
0.86
0.89
0.88
0.99 +
0.99 +
0.62
0.77
1820
0.70
0.53
0.70
0.66
0.66
1.07
0.84
0.83
0.90
0.75
1830
0.64
0.91
0.54
0.95
0.80
0.88
0.81
0.87
0.79
0.67
1840
0.54
0.49
0.49
0.60
0.49
0.43
0.81
0.68
0.65
0.45
1850
0.62
0.15
0.09
0.24
0.32
0.54
0.70
0.69
0.72
0.64
1860
0.82
0.62
1.08
0.85
1.23
0.96
1.69 +
1.08
0.93
1.60
1870
1.70
1.27
1.89 +
2.19
1.86
1.68
2.08
1.50
1.68
1.17
1880
0.72
1.14
1.17
1.53
1.49
1.59
1.52
1.59 +
1.97
2.13
1890
1.67
1.74
1.78
0.79
1.66
1.67
1.27
1.33
1.39 +
0.55
1900
1.48
1.58
1.36
1.56
1.07
1.37
1.18
1.12
0.67
1.21
1910
1.24
1.24
1.19
1.18
1.43
1.31
1.44
1.04
0.84
0.90
1920
0.72
....
....
Pike's Peak, High North Transect (HNT), 10 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1650
1.78
1.72
1.76
1.56
1.14
1660
1.85
1.32
1.42
1.32
6.99
1.13
0.76
0.99
0.55
1.02
1670
0.78
1.01
1.10
1.39
1.19
0.46
0.78
0.88
1.25
1.25
1680
1.82
1.35
0.41
0.49
0.62
0.54
0.88
0.93
1.07
1.30
1690
0.68
0.98
1.50
1.20
0.72
0.89
0.92
1.07
0.83
0.88
1700
0.87
1.37
1.37
1.24
1.13
0.98
1.33
0.87
1.02
0.73
1710
1.34
0.99
1.43
1.15
1.52
0.55
0.74
0.85
1.04
1.04
1720
1.36
1.07
1.09
1.00
1.11
1.34
1.58
0.79
1.14
0.98
1730
0.54
0.48
0.76
0.88
0.87
0.73
0.65
0.75
0.83
1.29
1740
1.09
0.78
0.36
0.81
0.81
0.48
1.11
1.17
0.48
0.62
1750
0.69
0.93
0.69
0.65
0.56
0.64
0.42
0.69-
0.49
0.71
1760
0.67
1.16
0.90
0.62
0.89-
0.85
1.24
0.91
1.60
1.33
1770
1.37
1.86
1.59 +
1.32
1.19 +
1.14
1.27
1.00
0.86
1.26+
1780
0.74 +
1.05
0.81
1.21
1.09 +
1.27
1.12
1.23
1.39+
0.57
1790
1.37
1.24
1.17
1.27
1.11
0.91
1.19 +
1.06
0.79+
0.99+
1800
1.31
0.79 +
1.37 +
1.39-
1.24
0.63
1.21
1.20
0.64-
0.88-
1810
1.25-
1.20
1.29
1.22
1.48
1.24
1.23
1.11
0.71
1.14+
1820
0.70
0.61
0.57
0.69
0.40
0.66
0.90 +
1.12
1.28
0.96
1830
0.80
1.13
0.65
1.07
1.05
1.63
1.29 +
1.27 +
1.58
1.52
1840
1.73
1.04
0.98 +
1.32
1.22
1.06
1.16-
0.91
0.93
0.91
1850
0.81-
0.29-
0.87
0.81
0.93 +
1.02
1.04
1.31
1.49
1.12
1860
1.56
0.85 +
1.10
0.64
1.16
0.69
1.02
1.04
0.98
1.41
1870
1.09
0.88 +
1.55 +
1.19
1.21
1.04-
1.41
1.02-
1.45
0.96-
1880
0.41
0.76-
0.97
1.07-
0.71
0.79 +
0.77
0.80
0.80
1.12
1890
0.93
0.79
0.76-
0.59 +
0.83
1.03
1.04
0.84 +
1.01
0.32 +
1900
0.82
0.78
0.84
0.97
1.05
0.83
0.92
1.05
0.65-
1.03
1910
0.93-
0.84
0.74
0.88-
0.92
0.99
0.89
0.71
0.86 +
0.79 +
1920
0.61
148
CLIMATIC CYCLES AND TREE-GROWTH
Pike's Peak, Low North Transect (LNT), 7 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1640
■ •
....
....
0.72
0.60
0.98
1.13
1.10
1.20
1650
0.68
i.i8
1.15
1.13
0.33
1.33
1.38
1.33
1.17
0.56
1660
1.45
1.48
1.16
1.00
0.80
1.32
0.72
0.89
0.68
0.87
1670
0.77
1.18
1.17
1.22
1.02
0.57
0.41
0.48
0.79
0.70
1680
0.98
0.55
0.60
0.72
0.56
0.33
0.70
0.73
0.96
1.06
1690
0.54
0.81
1.15
0.98
0.61
0.87
0.80
1.05
0.81
0.81
1700
0.79 +
0.89 +
0.82
0.89
0.86
1.00
1.07
0.92
0.79
0.95
1710
1.27
0.89
0.98
0.96
1.12
0.67
0.83
0.68
0.65
1.17
1720
1.26
1.25
1.16
0.86
0.91
0.75
0.93
0.76
0.88
0.79
1730
0.56
0.39
0.56
0.59
0.51
0.56
0.49
0.51
0.55
0.83
1740
0.84
0.82
0.69
0.89
1.07
0.72
1.06
1.02
0.48
0.69 +
1750
0.71
0.82
0.89
1.10
0.89
1.03
0.85
1.29
0.56
0.69 +
1760
0.71
0.89
1.07
0.87
0.79
0.73
0.91
0.80
0.96
0.72
1770
0.82
1.00
1.25
1.20
1.07
0.84
1.01
0.90
0.85
0.90
1780
0.63
0.93
0.78
0.93
0.86
0.86
0.96
1.04
1.06
0.52
1790
1.02
0.98
1.09
0.98
0.86
0.88
0.91
0.81
0.57
0.86
1800
0.91
0.70
1.20
1.09
0.85
0.71
0.93
0.99
0.71
0.69
1810
0.87
0.75
0.80
0.85
1.05
0.88
1.02
1.14
0.78
0.78
1820
0.62
0.58
0.57
0.51
0.50
0.70
0.77
0.98
0.96
0.80
1830
0.64
0.91
0.50
0.73
0.71
0.68
0.81
0.90
1.02
0.86
1840
0.96
0.66
0.63
0.77
0.81
0.68
0.98
0.79 +
0.91
0.75
1850
0.86
0.24
0.87
0.96
1.05
1.16
0.90
1.08
1.24
1.09 +
1860
1.07
0.69
1.03
0.58
1.17
0.83
1.01
1.09
0.85
1.32
1870
1.05
0.85
1.18
1.19
0.96
0.93
1.09
0,92
1.13
0.71
1880
0.42
0.88
0.95
0.86
0.57
0.68
0.71
0.76
0.75
0.73
1890
0.61
0.78
0.85
0.64
0.78 +
0.82
0.72
0.92
1.07
0.39-
1900
0.90
0.77 +
0.88 +
1.00
0.98-
0.87
0.88
0.87 +
0.69
1.11
1910
0.97
0.79
0.91
1.04
1.25
1.21
1.09 +
0.91
0.75
0.95 +
1920
0.70
....
Pike's Peak, South Transect (ST), 8 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1570
1.40
2.15
2.03
1.12
1.37
0.84
0.73
0.78
0.70
0.68
1580
0.61
1.17
0.93
1.00
1.09
107
1.20
0.65
0.63
0.76
1590
0.92
1.00
0.90
0.85
0.95
0.99
0.81
1.02
0.92
1.00
1600
1.18
0.96
0.91
0.92
1.35
0.76
0.73
0.93
0.73
0.95
1610
1.19
1.04
0.66
0.98
0.72
0.98
0.98
0.96
1.19
1.25
1620
0.91
0.80
0.85
1.12
1.19
1.09
1.10
0.82
0.95
1.09
1630
1.10
0.75
1.36
1.32
1.36
0.98
1.13
1.20
0.25
0.16
1640
0.36
0.29
0.42
0.20
0.36
0.41
0.55
0.45
0.66
0.77
1650
0.80
0.87
0.64
0.95
0.82
1.28
1.27
1.47
1.41
1.16
1660
1.44
1.53
1.44
1.35
1.08
1.15
0.97
0.42
0.32
0.60
1670
0.53
0.65
0.68
0.61
0.78
0.68
0.27 +
0.22
0.52
0.52
1680
0.46
0.51
0.70
0.62
0.74
0.83
0.96
1.01
1.14
1.17
1690
1.43
1.01
1.25
1.02
0.95
1.05
1.15
1.17
1.27
1.16
1700
1.48
1.12
1.19
1.23
1.42
1.58
1.28
1.33
1.18
1.33
1710
1.49
1.46
1.38
1.37
1.84
1.01
0.95
0.99 +
1.27
1.49 +
1720
1.45
1.12
0.78
0.62
0.89
1.00
1.01
0.81
0.95
1.27
1730
1.35
0.56
0.22
0.49
0.49
0.80
0.63
0.82
0.86
1.13
1740
1.05
1.06
0.91
1.12
0.98
0.77
0.82
0.95
0.88
0.73
1750
0.62
0.79
0.72
1.05
0.68
0.88
1.25
1.12
0.09
0.18
1760
0.55
0.68
0.74
0.70
0.73
0.66
0.77
1.14
0.84
0.97
1770
0.73
0.93
1.14
1.09
1.07
1.13
1.49
1.52
1.44
1.48
1780
1.01
1.26
0.99-
1.20
1.37
1.29
1.28-
1.21
1.54-
1.30
1790
1.46
1.30
1.39 +
1.65
1.57
1.60
1.71
1.25
0.99 +
1.17
1800
1.25
0.91
1.18
1.17
1.34
1.19
1.29 +
1.31
1.23
1.36-
APPENDIX
149
Pike'a Peak,
South Transect (ST), 8 trees
— Continued
A.D.
0
1
2
3
4
5
6
7
8
9
1810
1.29
1.35
1.59
1.34
1.65
1.42
1.71
1.70
1.38
1.14
1820
1.24
1.11
1.16
1.31
0.94-
1.19-
1.32
1.42
1.37
1.11
1830
0.94
1.17
0.74
0.88 +
0.88+
1.07+
0.97
1.04
1.16-
1.04
1840
1.09-
1.04
0.99 +
1.06
1.03
0.89+
1.08-
0.92
0.90
0.88
1850
0.98+
0.43-
0.95
0.96
1.15
1.07
0.81
0.95 +
1.12
0.78
1860
0.81
0.77
0.80
0.66
0.93
0.76
0.83
0.81
0.86 +
0.89+
1870
0.87-
0.74
0.89
0.98
0.81
0.92
0.99 +
0.88 +
1.11
0.76-
1880
0.73
0.76
0.80
0.59 +
0.56
0.50
0.68 +
0.76
0.71
0.73
1890
0.71
0.82
0.79
0.80
0.97
0.95
0.91
0.99 +
0.98
0.49+
1900
0.87
0.71
0.87
1.05
0.86
0.81
0.64
0.67
0.56
0.79+
1910
0.70
0.63
0.84 +
0.91
0.82
0.87
0.79 +
0.73
0.66 +
0.76+
1920
0.69 +
Pike's Peak, Brook, Douglas Fir and Pine (BDF),
6 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1780
0.64
0.61
0.58
0.88
0.87
1.18
1.36
0.73
1790
1.13
1.37
1.65
1.20
1.08
1.10
1.33
1.28
0.38
0.32
1800
0.60
0.59
0.90
1.01
1.28
0.87
1.26
1.33
1.21
1.03
1810
1.22
1.07
1.30
1.11
1.17
1.15
1.07
0.89
0.62
0.80
1820
0.82
0.73
0.71
0.67
0.60
0.83
1.20
1.32
1.45
1.33
1830
1.24 +
1.22
0.92
0.97
0.94
1.00
0.87
1.05
0.96
1.05
1840
1.13
0.67-
0.64
0.81
0.84
0.77
0.84
0.87 +
0.96
0.92 +
1850
0.90
0.58+
1.05
1.20
1.41
1.06
0.73
1.12 +
1.39 +
1.20
1860
1.15
0.75
1.02
0.62
0.90
0.59
0.97
1.00
0.78
1.13
1870
0.94
0.79
0.90
0.76
0.93
0.94
0.99
0.84
0.93
0.71
1880
0.35
0.79-
0.88
0.76
0.80
0.77
0.77
0.70
0.78
0.83
1890
0.75
0.76
0.71
0.58
0.76
0.94
0.80
0.94
0.95
0.46
1900
0.53-
0.65+
0.67
0.92
1.10
1.11
0.94
1.08
0.53
1.01
1910
1.03-
0.68-
0.81
1.03-
1.03-
1.37
1.25
0.73
0.64
1.00
1920
0.63-
Pike's Peak
, Brook, Engelmann Spruce
(BES), 4 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1770
1.11
0.78
1.07
1.09
1.15
1780
1.35
1.00
1.39
1.34
1.12
1.04
1.04
1.02
0.92
0.92
1790
1.04
1.08
1.43
1.07
1.11
1.13
1.12
1.00
0.98
0.74
1800
1.11
0.69 +
0.99
1.17
1.05
0.82
0.88 +
1.02
0.78
0.97
1810
0.87
0.97
1.00
0.86
1.00
1.09
1.07
1.19 +
1.00
1.10
1820
0.73
0.61
0.56
0.64
0.46
0.80
1.07
1.17
1.31
1.10
1830
0.95
1.11
0.74
0.72
0.81
1.00
1.19
1.09
1.15
1.11
1840
1.17 +
1.26
0.92
1.35
1.14
1.07
1.02
0.93
0.84
0.94
1850
0.87
0.64
0.74
0.82
0.97
0.99
0.66
0.61
0.81
0.38 +
1860
0.72
0.43
0.63
0.66
0.70
0.50
0.60
0.70
0.80
0.90
1870
1.09 +
1.10
1.10
1.00
1.03 +
1.07 +
1.09
1.09
1.42
1.40
1880
1.16
1.25
0.94
1.08
1.05
1.33
1.09
1.40
1.32 +
1.42
1890
1.06
0.84 +
0.79
0.53
0.71
0.87
0.83 +
1.01
1.12
0.82
1900
1.28
1.14
1.15
1.24
0.85
0.83
0.62
0.63
0.74 +
0.86
1910
0.76 +
0.93
0.64
1.15
1.16-
1.26
1.14
0.71
0.60
0.73
1920
0.57
....
150
CLIMATIC CYCLES AND TREE-GROWTH
Cloudcroft, New Mexico (CC), S trees
A.D.
0
1
2
3
4
5
6
7
8
9
1730
1.21
1.27
1.27
0.90
1740
1.13
1.73
1.12
1.60
2.11
2.23
2.88
3.49
1.69
2.11
1750
1.88
2.62
0.87
2.10
2.08
2.42
2.45
3.02
3.39
2.81
1760
2.83
3.46
2.96
1.67
2.72
2.87
3.78
2.06
1.42
2.70
1770
2.10
2.48
1.92
2.13
2.21
1.96
2.74
2.34
1.70
2.47
1780
1.82
1.92
1.05
1.48
2.26
1.48
1.80
2.37
2.03
1.33
1790
2.51
2.29
2.87
3.11
2.28
1.58
2.71
1.97
1.34
2.40
1800
2.49
1.91
2.18
2.42
2.15
2.62
2.70
1.83
2.09
1.78
1810
1.98
2.00
1.33
2.01
2.24
2.86
2.26
1.42
1.88
0.95
1820
0.84
0.66
1.00
1.39
1.49
1.30
1.44
1.96
1.13
1.96
1830
1.17
0.91
1.30
1.35
1.74
1.22
0.95
0.54
0.61
0.90
1840
1.01
0.70
0.54
0.58
1.05
0.91
1.14
0.45
0.85
0.71
1850
0.40
0.38
1.05
1.08
1.13
0.68
1.37
0.92
1.07
0.32
1860
0.66
1.38
0.45
1.09
0.85
0.96
1.28
1.12
1.89
2.14
1870
1.12
1.52
1.60
1.24
1.18
1.38
2.03
1.31
1.29
1.13
1880
1.15
1.28
1.88
1.66
2.05
2.13
1.58
2.04
1.39
1.51
1890
1.66
1.32
0.75
0.56
0.81
1.06
0.92
1.20
1.96
1.08
1900
1.38
1.19
0.87
1.41
0.51
1.11
0.87
1.48
0.99
0.73
1910
0.72
1.25
1.01
1.20
1.27
0.70
1.17
1.38
1.36
1.32
1920
1.28
Santa Fe, New Mexico (SF), 6 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1740
• •
4.94
1750
3.12
3.48
3.72
3.20
5.18
5.56
2.72
3.52
2.80
3.66
1760
2.80
5.52
4.70
2.88
5.00
3.40
4.94
4.32
2.64
2.96
1770
1.98
3.28
2.38
1.48
2.08
2.08
2.12
2.16
2.40
1.76
1780
2.24
2.20
2.10
2.20
1.70
2.06
2.00
1.94
1.60
1.28
1790
1.24
2.62
2.36
3.12
2.42
2.50
2.64
1.96
2.30
2.30
1800
2.56
1.90
2.30
2.02
2.50
1.64
1.38
1.80
2.32
1.50
1810
1.98
1.42
1.32
2.00
1.70
2.60
2.74
1.92
1.46
1.94
1820
2.32
2.02
1.16
1.64
1.64
2.28
2.24
2.30
2.42
2.24
1830
2.20
2.06
2.36
2.10
2.82
2.58
2.20
2.22
2.78
2.76
1840
2.54
2.08
0.90
1.32
2.12
1.58
1.92
1.20
1.14
1.74
1950
1.58
1.90
2.56
1.92
2.64
2.12
2.12
2.02
2.34
1.64
1860
1.56
1.78
1.76
1.80
1.42
1.94
2.68
2.50
3.02
2.96
1870
2.22
2.12
2.38
1.34
1.90
2.62
2.06
2.34
2.18
1.86
1880
1.02
1.22
1.96
1.82
2.50
2.14
2.40
2.62
1.98
1.68
1890
1.28
1.60
1.80
1.38
1.84
2.00
1.24
2.48
1.96
1.24
1900
1.92
2.08
1.42
2.12
0.72
2.10
2.02
2.84
2.64
1.64
1910
1.62
1.74
1.84
1.88
2.10
1.54
2.06
1.10
1.24
1.76
1920
1.64
2.28
Modern H, 17, 22, 28, 24, 25, 26 (BMH), 6 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1580
0.71
1.02
1590
0.94
1.36
1.06
1.12
1.48
2.10
1.97
2.04
2.08
2.99
1600
1.78
2.14
2.64
2.87
3.41
3.36
3.14
2.77
3.13
2.77
1610
3.48
3.56
2.70
2.59
2.67
2.67
2.48
2.30
2.39
2.68
1620
2.26
2.81
1.86
1.39
1.66
2.30
1.94
2.72
2.28
2.73
1630
1.84
1.13
1.04
1.82
2.01
2.13
2.26
2.07
1.35
1.87
1640
2.52
1.90
1.58
1.60
2.87
2.13
2.54
2.05
1.64
1.86
APPENDIX
151
Modern H, 17, 22, 23, 24, 25, 26 (BMH), 6 trees— Continued
A.D.
0
1
2
3
4
5
6
7
8
9
1650
2.32
2.14
2.25
2.38
1.70
2.57
2.30
1.80
1.47
1.63
1660
1.81
2.22
1.97
1.72
1.34
1.61
1.18
1.18
1.03
1.34
1670
1.18
1.62
2.77
1.84
1.60
1.72
0.95
1.38
1.50
1.74
1680
2.06
2.05
1.38
2.08
1.41
0.18
1.31
1.92
2.36
2.18
1690
1.65
1.42
1.95
1.44
1.35
1.41
1.02
1.38
1.34
1.91
1700
1.50
2.18
1.50
1.12
1.16
1.92
1.72
0.99
1.32
1.72
1710
1.48
1.73
1.22
1.47
1.30
1.47
1.32
1.33
1.48
1.42
1720
1.79
1.59
1.54
1.78
1.60
2.10
1.87
1.31
1.45
0.75
1730
0.74
0.81
0.86
0.79
1.06
0.28
0.54
0.59
0.82
0.78
1740
0.72
0.79
0.97
1.21
1.06
1.50
1.67
1.78
0.42
1.36
1750
1.44
1.04
0.91
1.15
1.23
0.59
0.62
0.67
0.76
1.12
1760
1.01
1.27
1.48
1.48
1.68
1.24
1.63
1.64
1.40
0.97
1770
1.30
1.57
1.58
0.61
1.12
0.80
0.79
0.79
0.71
0.72
1780
0.64
0.67
0.74
0.81
1.08
0.56
0.84
0.97
0.60
0.80
1790
0.81
1.13
1.05
1.25
1.24
1.10
0.91
0.91
1.02
1.12
1800
1.35
1.06
1.28
1.05
0.88
0.91
0.77
0.77
0.66
0.75
1810
0.87
0.90
0.81
0.43
0.65
1.03
1.07
0.72
0.16
0.45
1820
0.36
0.48
0.26
0.25
0.50
0.51
0.61
0.48
0.85
0.67
1830
1.02
0.87
0.81
0.90
0.70
0.84
0.82
0.82
0.87
0.92
1840
0.88
1.00
0.71
0.85
0.76
0.76
0.69
0.07
0.66
0.87
1850
0.71
0.30
0.87
0.95
0.65
0.66
0.65
0.89
0.89
0.54
1860
0.80
0.16
0.85
0.72
0.33
0.72
0.89
0.91
1.23
1.19
1870
0.73
0.32
0.62
0.72
0.62
0.92
0.72
0.85
0.92
0.45
1880
0.68
0.76
0.57
0.65
0.76
0.93
0.68
0.87
0.84
0.72
1890
0.84
0.94
0.78
0.59
0.60
0.59
0.37
0.74
0.70
0.39
1900
0.28
0.42
0.12
0.75
0.37
0.78
0.70
1.04
1.12
1.02
1910
1.16
1.14
0.82
0.82
1.06
0.94
1.05
0.82
0.81
0.72
Modern H, 27
, 28 (BML), 2 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1700
1.28
1.25
1.76
1.28
0.96
1.23
1.59
0.97
1.15
1.21
1710
1.70
1.99
1.72
1.65
1.34
1.50
1.57
1.47
1.84
2.55
1720
2.96
3.07
3.26
2.78
2.74
4.00
4.06
2.88
3.04
1.75
1730
3.75
3.26
3.20
3.55
3.39
1.26
1.99
1.94
2.67
2.02
1740
1.94
1.82
2.49
2.61
2.94
3.43
4.32
3.48
1.56
3.11
1750
2.44
1.98
1.99
1.74
2.37
1.19
1.35
1.37
1.61
2.27
1760
2.13
2.00
2.83
2.17
2.47
1.72
2.57
2.66
2.75
1.77
1770
1.84
2.79
2.85
1.28
1.82
1.50
1.37
1.11
1.37
1.13
1780
1.13
1.36
1.38
1.75
2.02
1.05
1.58
2.21
1.12
1.11
1790
1.48
1.69
1.59
2.28
1.88
1.65
1.08
1.31
1.46
1.67
1800
1.84
1.24
2.03
1.43
1.65
1.43
1.31
1.35
1.57
1.03
1810
1.33
1.66
1.41
1.07
1.49
1.85
1.72
1.52
0.64
0.94
1820
0.82
0.71
0.27
0.31
0.62
0.68
1.02
0.98
1.46
1.05
1830
1.70
1.08
1.57
1.31
1.31
1.41
1.37
1.58
1.56
1.53
1840
1.33
1.67
1.25
1.32
1.09
1.17
0.83
0.35
0.70
1.04
1850
0.75
0.39
1.07
1.12
0.91
0.94
1.05
1.22
0.92
0.66
1860
1.20
0.44
1.14
0.80
0.50
0.96
1.28
1.09
1.22
1.39
1870
1.10
0.40
0.67
0.74
0.66
1.24
0.57
1.08
1.17
0.68
1880
0.80
1.17
0.88
0.66
1.28
1.39
0.88
1.36
1.40
1.13
1890
1.43
1.29
1.15
0.90
0.81
0.71
0.51
0.98
0.84
0.41
1900
0.33
0.48
0.02
0.81
0.26
0.75
0.84
1.51
1.45
1.37
1910
1.37
1.64
1.33
1.28
1.61
1.47
1.70
0.88
11
152
CLIMATIC CYCLES AND TREE-GROWTH
Modern H, 89
40,41,42 (AE), 4 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1660
2.30
1.50
1.20
2.25
0.72
0.82
0.72
0.45
1670
6.79
1.13
1.21
1.40
1.70
1.43
0.83
1.24
1.72
1.06
1680
1.81
1.72
1.31
1.67
0.85
0.17
1.80
1.68
1.23
1.87
1690
2.55
1.60
2.55
2.63
1.61
1.40
0.90
1.30
1.97
2.42
1700
1.79
2.37
1.20
1.38
0.98
1.64
2.07
1.07
1.54
1.41
1710
2.49
2.01
1.46
1.04
0.76
1.22
1.00
1.24
1.75
1.70
1720
2.30
1.78
1.30
1.67
0.97
1.30
1.90
2.04
1.66
0.29
1730
0.95
1.16
1.51
1.21
1.45
0.36
1.04
0.77
0.96
1.00
1740
0.86
0.90
0.77
1.16
0.80
1.08
1.45
1.98
0.61
1.82
1750
1.26
1.06
0.93
0.72
1.21
0.82
0.70
0.69
0.71
0.81
1760
0.73
0.73
0.96
0.93
0.99
0.66
1.50
0.85
1.26
1.10
1770
1.44
1.56
1.18
0.34
0.84
0.95
0.55
0.53
0.66
0.57
1780
0.52
0.68
0.58
0.77
0.75
0.68
0.70
0.97
0.52
0.40
1790
0.47
0.63
0.76
0.91
0.48
0.66
0.64
0.44
0.52
0.59
1800
0.62
0.31
0.86
0.60
0.62
0.43
0.24
0.66
0.59
0.62
1810
0.42
0.75
0.80
0.54
0.63
1.09
1.44
1.29
0.37
0.40
1820
0.31
1.00
0.43
0.41
0.35
0.58
0.56
0.39
0.87
0.68
1830
0.90
0.86
1.25
1.19
0.86
0.93
0.64
0.70
0.83
1.11
1840
1.12
1.01
0.84
0.76
0.54
0.59
0.69
0.04
0.76
0.66
1850
0.76
0.25
0.77
0.92
0.68
0.66
0.67
0.48
0.65
0.45
1860
0.60
0.02
0.69
0.39
0.10
0.38
0.37
0.55
0.65
0.85
1870
0.40
0.00
0.42
0.25
0.43
0.44
0.43
0.10
0.46
0.26
1880
0.26
0.29
0.27
0.25
0.38
0.21
0.39
0.52
0.59
0.44
1890
0.69
0.69
0.73
0.74
0.54
0.27
0.24
0.35
0.16
0.46
1900
0.37
1.12
0.25
0.26
0.32
0.38
0.32
0.44
0.38
0.38
1910
0.37
0.53
0.66
0.35
0.80
0.85
0.99
0.92
0.52
0.84
COAST ZONE
Boise, Idaho (BI), 10 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1650
1.70
0.65
1.50
1.65
2.05
1.05
1.70
2.05
1660
1.70
1.75
1.30
1.50
1.30
1.00
1.60
1.40
0.90
1.50
1670
1.80
1.75
1.15
1.60
0.90
1.15
0.90
0.80
0.80
1.25
1680
0.75
1.25
1.10
1.20
1.20
1.05
1.00
1.40
1.40
1.25
1690
2.00
1.75
2.15
2.45
3.55
2.35
1.95
2.45
2.15
2.15
1700
2.20
2.05
3.15
3.20
1.85
2.30
2.90
2.40
1.75
1.60
1710
2.05
1.85
1.95
1.75
1.10
0.90
1.35
0.95
1.10
1.00
1720
1.50
0.50
0.60
0.95
0.80
0.75
0.80
1.00
0.75
0.50
1730
0.50
0.85
1.20
1.05
1.00
1.20
1.00
1.45
1.60
1.00
1740
1.00
1.35
0.90
1.35
1.05
1.35
1.75
1.50
1.45
1.45
1750
1.95
2.20
2.35
1.60
1.64
2.28
1.80
1.58
2.21
2.09
1760
1.98
2.91
2.79
2.33
2.06
2.45
2.51
2.88
2.51
2.05
1770
1.98
1.98
2.28
1.12
0.81
1.28
1.65
1.81
1.32
1.42
1780
1.80
1.48
1.74
1.38
1.14
1.62
1.63
1.29
1.57
1.55
1790
1.67
1.99
2.19
1.98
1.56
1.27
1.37
1.15
0.93
1.36
1800
1.53
1.57
1.49
1.44
1.45
1.61
1.59
0.97
1.11
1.15
1810
0.60
0.70
1.02
0.98
1.18
1.10
1.12
1.00
1.15
1.15
1820
1.15
1.23
1.11
1.20
1.09
1.07
0.97
1.08
1.25
1.18
1830
1.06
0.83
1.36
1.01
0.87
1.00
1.02
1.01
1.00
0.91
1840
0.77
0.88
0.92
0.79
0.74
0.89
0.85
0.79
0.72
0.70
1850
0.82
0.79
0.71
0.68
0.99
0.83
0.67
0.93
0.88
0.64
1860
0.94
1.06
0.90
0.76
0.72
0.68
0.90
0.78
0.92
0.91
1870
0.70
0.71
0.88
0.91
0.84
0.91
0.93
0.94
0.94
0.96
1880
0.73
0.82
0.70
0.60
0.80
1.07
0.71
0.85
0.76
0.48
1890
0.45
0.69
0.78
0.53
0.63
0.72
0.64
0.36
0.59
0.62
1900
0.83
0.87
0.85
0.85
0.76
0.75
0.59
0.68
0.86
0.87
1910
0.86
0.87
0.78
0.79
0.63
0.58
0.52
0.42
0.74
0.93
1920
0.64
0.79
0.75
APPENDIX
Boise, Idaho, 8 trees selected
153
A.D.
0
1
2
3
4
5
6
7
8
9
1650
1.70
0.65
1.50
1.65
2.05
1.05
1.70
2.05
1660
i.Vo
1.75
1.30
1.50
1.30
1.00
1.60
1.40
0.90
1.50
1670
1.80
1.75
1.15
1.60
0.90
1.15
0.90
0.80
0.80
1.25
1680
0.75
1.25
1.10
1.20
1.20
1.05
1.00
1.40
1.40
1.25
1690
2.00
1.75
2.15
2.45
3.55
2.35
1.95
2.45
2.15
2.15
1700
2.20
2.05
3.15
3.20
1.85
2.30
2.90
2.40
1.75
1.60
1710
2.05
1.85
1.95
1.75
1.10
0.90
1.35
0.95
1.10
1.00
1720
1.50
0.50
0.60
0.95
0.80
0.75
0.80
1.00
0.75
0.50
1730
0.50
0.85
1.20
1.05
1.00
1.20
1.00
1.45
1.60
1.00
1740
1.00
1.35
0.90
1.35
1.05
1.35
1.75
1.50
1.45
1.45
1750
1.95
2.20
2.35
1.60
1.64
2.28
1.80
1.58
2.22
2.09
1760
1.98
2.91
2.79
2.33
2.06
2.45
2.51
2.82
2.51
2.05
1770
1.98
1.98
2.28
2.15
0.84
1.32
1.71
1.88
1.37
1.49
1780
1.89
1.50
1.80
1.63
1.12
1.88
1.80
1.39
1.53
1.65
1790
1.23
2.45
2.45
2.36
1.89
1.49
1.72
1.45
1.15
1.63
1800
1.74
1.55
1.63
1.72
2.01
1.96
2.05
1.20
0.93
0.83
1810
0.25
0.33
0.59
0.68
1.10
1.18
1.26
1.23
1.41
1.41
1820
1.28
1.45
1.78
1.33
1.36
1.42
1.56
1.45
1.70
1.80
1830
1.42
0.90
1.82
1.78
1.12
1.10
1.20
1.25
1.48
1.18
1840
0.92
1.25
1.25
0.95
0.75
0.78
0.78
0.35
0.48
0.58
1850
0.65
0.68
0.42
0.82
1.08
0.81
0.75
0.93
0.82
0.63
1860
0.88
0.95
0.94
0.92
0.81
0.77
1.03
1.03
1.11
1.09
1870
0.81
0.78
0.82
0.91
1.15
1.14
1.03
1.16
1.17
1.12
1880
1.05
0.93
0.73
0.60
0.73
1.07
0.87
0.92
0.91
0.42
1890
0.41
0.65
0.72
0.40
0.53
0.55
0.39
0.16
0.45
0.40
1900
0.36
0.49
0.62
0.41
0.63
0.61
0.49
0.55
0.85
0.80
1910
0.68
0.85
0.46
0.62
0.58
0.59
0.50
0.31
0.66
0.90
1920
0.65
0.41
0.55
Baker, Oregon (BO) , 7 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1660
1.60
1.65
0.55
1.10
1.25
1.10
2.00
2.40
2.00
2.10
1670
2.85
3.35
2.70
2.20
2.20
1.90
1.45
1.25
1.80
1.65
1680
0.90
1.00
1.00
0.90
1.25
1.35
1.60
1.25
1.35
1.60
1690
1.35
1.45
1.45
1.00
1.50
1.20
1.20
1.45
1.05
0.80
1700
0.75
0.60
0.80
1.00
0.95
1.30
1.80
1.65
1.50
1.70
1710
2.80
3.20
2.95
2.40
1.75
2.70
2.40
1.50
1.65
1.00
1720
1.25
0.90
1.10
1.10
1.10
1.65
2.10
2.20
1.45
1.55
1730
1.90
1.60
1.75
1.75
1.25
1.70
1.50
2.10
1.60
1.20
1740
1.25
1.35
1.05
1.05
1.25
1.45
1.25
1.10
1.10
1.30
1750
1.35
1.20
1.30
0.85
0.85
0.80
0.50
0.65
0.65
0.45
1760
1.15
1.20
0.80
0.75
0.74
0.64
0.90
0.82
0.78
0.78
1770
0.88
0.97
1.02
0.98
1.06
0.90
0.75
0.64
0.85
0.95
1780
1.10
0.84
0.86
0.78
0.66
0.47
0.79
0.72
0.86
1.04
1790
1.13
1.74
1.92
1.55
1.70
1.50
1.79
1.02
1.32
1.29
1800
1.18
1.16
1.14
1.14
0.91
1.03
0.90
0.82
0.89
1.11
1810
1.04
1.04
1.64
1.42
1.66
1.23
1.24
1.09
1.22
1.64
1820
1.17
1.23
1.65
0.87
1.58
1.84
1.53
0.89
1.08
0.93
1830
0.87
1.18
1.15
1.05
0.89
0.89
1.21
1.38
1.67
1.69
1840
1.14
1.11
0.83
0.70
0.77
1.12
0.94
0.59
0.84
0.78
1850
0.57
0.81
0.77
0.87
0.88
1.23
0.97
1.16
1.23
1.00
1860
1.00
1.19
1.06
1.12
1.18
1.29
1.87
1.39
1.66
1.32
1870
1.28
1.20
1.26
1.52
1.29
1.35
1.79
2.03
1.89
1.71
1880
1.39
1.72
1.29
0.98
1.08
1.44
1.05
1.05
1.18
0.87
1890
0.75
1.02
0.85
0.72
1.16
0.95
1.01
1.16
1.21
0.80
1900
1.23
1.09
0.99 +
1.06
1.17
1.02
0.91
1.10
0.93
0.94
1910
0.76
0.69
0.81
1.05
0.78
0.82
0.95
0.60
0.65
0.71
1920
0.61
0.76
0.32
0.60
0.52
154
CLIMATIC CYCLES AND TREE-GROWTH
The Dalles, Oregon (DL), S trees
A.D.
0
1
2
3
4
5
6
7
8
9
1760
3.00
3.30
3.50
1.94
2.72
1770
1.55
1.93
2.23
1.72
1.68
1.57
0.87
0.92
0.93
1.10
1780
0.75
0.98
1.30
1.18
0.99
0.90
1.64
1.01
0.82
0.88
1790
0.97
0.81
1.20
1.18
0.84
0.60
0.49
0.58
1.10
1.18
1800
1.11
1.12
1.25
0.93
0.79
1.10
1.25
1.26
1.68
1.43
1810
1.39
1.39
1.56
1.81
1.45
1.35
1.18
1.15
0.80
1.28
1820
1.21
1.05
0.93
0.81
0.82
0.84
0.99
1.25
0.88
1.15
1830
1.25
1.08
1.00
1.35
1.12
1.21
1.00
0.88
0.99
0.67
1840
0.68
0.44
0.66
0.92
0.74
1.02
0.98
0.54
0.48
0.34
1850
0.63
0.42
0.65
0.69
0.94
0.88
0.96
1.02
1.05
1.05
1860
1.21
1.08
1.09
1.17
1.63
1.06
1.23
1.12
1.07
1.07
1870
1.30
1.23
1.39
1.09
1.18
0.74
1.24
1.11
1.03
1.01
1880
1.16
1.00
1.34
1.12
1.23
1.16
1.19
1.01
0.77
0.68
1890
0.55
0.37
0.38
0.39
0.54
0.73
0.95
1.38
1.21
1.03
1900
1.14
1.13
0.85
1.09
1.13
0.79
0.85
0.82
1.14
0.79
1910
0.66
0.70
0.83
0.97
0.85
0.91
0.89
0.92
0.74
0.70
1920
0.68
1.12
0.89
0.68
1.05
Oregon Coast (OCT)
(See Volume I, Appendix, page 117)
Klamath Falls
, Oregon
[KF), It trees
A.D.
0
1
2
3
4
5
6
7
8
9
1790
1.01
1.17
0.83
0.69
0.75
1.16
1.25
1.74
1800
1.02
1.05
1.32
1.23
1.12
1.23
1.44
1.18
1.15
1.35
1810
1.14
1.18
0.94
1.93
0.94
0.86
0.91
0.96
1.16
1.15
1820
0.93
0.95
0.81
0.83
0.56
0.92
0.91
0.86
0.94
0.61
1830
1.05
1.08
1.47
0.87
0.91
1.47
1.64
1.51
1.43
0.48
1840
1.08
0.57
0.73
0.63
0.35
0.76
0.50
0.69
0.81
0.72
1850
0.91
0.97
0.84
1.21
0.94
1.00
0.85
0.94
0.79
0.69
1860
1.10
1.35
0.99
0.99
0.98
0.84
1.01
1.03
1.09
0.42
1870
0.72
0.54
0.66
0.85
0.91
0.80
1.08
1.05
1.15
0.98
1880
0.85
1.12
0.81
0.93
1.13
1.04
0.96
1.04
0.99
0.32
1890
0.69
0.79
0.85
1.14
1.56
1.12
1.12
1.21
0.35
0.79
1900
0.92
1.04
0.99
1.20
1.19
0.92
0.95
1.12
1.00
1.19
1910
1.19
0.94
1.08
1.33
1.23
0.77
1.18
0.86
0.50
0.76
1920
0.31
0.61
0.51
0.75
Meadow Valley Pines, Plumas County, California (CP), 9 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1550
2.13
1.95
1.80
1.98
2.91
2.37
1.80
1.50
1.17
1560
1.26
1.47
1.62
1.77
1.68
1.92
1.11
0.93
1.26
1.20
1570
0.90
1.59
1.32
1.26
1.53
1.68
2.19
1.29
1.38
0.93
1580
1.02
1.05
1.23
1.35
1.17
1.23
1.26
1.23
0.75
0.36
1590
0.90
1.05
0.90
0.42
0.24
0.51
0.75
0.90
0.90
0.87
1600
1.17
1.11
1.50
0.99
0.75
1.20
1.23
1.20
1.05
1.08
1610
1.80
1.44
0.96
1.50
1.53
1.20
1.50
1.83
1.44
1.80
1620
1.95
1.35
1.53
2.40
1.80
1.74
1.50
2.76
1.80
2.31
1630
2.19
1.80
2.01
2.46
3.66
3.51
3.54
4.50
3.03
2.64
1640
2.88
3.60
3.09
3.84
4.02
2.91
3.84
3.39
2.55
3.21
1650
3.24
3.69
2.70
2.67
2.76
3.66
3.42
2.94
3.12
3.63
1660
2.43
3.30
3.30
2.40
3.30
2.79
3.15
3.51
2.94
3.27
APPENDIX
155
Meadow Valley Pines (CP),
9 trees —
Continued
A.D.
0
1
2
3
4
5
6
7
8
9
1670
2.88
2.67
3.00
3.72
3.42
3.48
2.88
2.97
3.09
3.24
1680
3.12
3.75
3.39
2.82
3.27
3.57
3.39
2.94
3.18
2.16
1690
2.52
3.48
3.18
2.58
3.78
2.97
2.79
2.79
2.73
3.12
1700
3.12
2.16
2.64
2.88
2.97
2.97
2.73
2.97
3.03
2.67
1710
3.21
2.22
2.67
2.49
2.85
3.30
3.75
3.54
3.21
2.82
1720
3.24
2.85
3.18
3.03
2.46
2.61
3.21
2.85
2.61
2.82
1730
3.12
3.03
2.88
2.49
2.67
2.82
3.12
2.61
3.21
2.97
1740
2.58
2.61
2.61
3.06
2.70
2.64
2.43
2.76
2.37
2.85
1750
2.82
2.85
2.52
2.64
3.03
3.15
2.49
2.58
2.76
3.12
1760
2.37
2.97
2.55
2.10
2.25
2.64
2.49
2.37
2.46
2.13
1770
2.52
2.28
2.46
2.70
2.85
2.97
2.49
2.07
2.67
2.64
1780
3.30
2.73
2.70
2.97
2.73
2.97
3.18
2.37
2.70
2.43
1790
2.52
2.91
3.42
3.33
3.06
2.91
2.31
2.70
3.63
3.39
1800
3.66
3.33
2.91
3.30
3.78
3.63
3.57
3.72
4.11
4.56
1810
4.74
4.44
4.92
3.99
4.17
3.30
3.51
3.21
3.57
3.57
1820
3.33
2.49
2.58
1.68
1.89
2.37
2.76
2.70
2.43
2.91
1830
1.95
2.13
2.91
2.46
2.25
2.46
2.40
2.82
2.37
2.31
1840
2.85
3.09
2.70
3.06
2.82
3.63
3.51
2.94
2.25
1.83
1850
2.19
2.58
2.67
2.43
2.43
3.00
2.58
2.61
2.19
2.16
1860
2.70
2.61
2.10
2.34
2.19
2.25
2.49
3.18
2.82
3.18
1870
3.39
3.36
3.48
3.27
2.70
2.79
2.34
2.73
2.43
2.58
1880
2.01
2.70
1.71
1.68
1.95
2.31
1.59
1.79
1.83
1.65
1890
1.59
1.89
1.89
2.10
2.31
1.83
2.04
1.98
1.77
1.92
1900
2.67
2.10
2.13
2.16
2.01
2.07
2.07
2.19
2.16
1.98
1910
1.59
1.77
2.28
2.22
2.07
1.77
1.74
1.62
1.65
1.68
1920
1.59
1.92
....
Calaveras Pines (CVP), 14 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1620
1.60
1.70
1.40
1.30
1.15
1.95
1.35
1.40
1.65
1630
1.55
0.90
1.15
1.40
1.45
1.55
1.90
2.45
2.10
1.45
1640
1.20
1.40
1.45
1.75
1.80
1.80
1.80
2.20
1.90
1.45
1650
1.95
1.50
1.50
0.60
1.65
0.70
1.60
1.05
0.90
1.15
1660
1.85
1.50
1.70
2.05
1.15
1.10
1.75
1.80
0.95
1.88
1670
1.93
1.83
1.65
2.15
1.70
1.83
1.58
1.88
1.88
1.65
1680
1.60
2.90
2.08
1.35
2.00
2.75
1.95
1.65
2.03
1.40
1690
1.48
1.95
1.35
1.53
2.25
2.20
1.88
1.55
1.50
2.52
1700
1.95
1.20
1.32
2.41
2.00
2.90
2.48
2.00
2.12
2.58
1710
2.81
1.89
2.78
2.31
2.57
2.14
2.05
2.04
1.70
1.59
1720
1.85
1.85
1.67
2.32
2.11
1.68
2.30
2.10
1.56
1.12
1730
1.62
1.65
1.56
1.36
1.42
1.20
1.78
1.28
1.56
1.69
1740
1.59
2.21
1.71
1.26
1.46
1.34
1.55
1.63
1.31
1.86
1750
1.97
1.91
1.75
1.74
1.26
1.74
1.35
1.15
1.83
1.88
1760
1.60
2.14
1.73
1.14
1.32
1.42
1.84
1.31
1.77
1.54
1770
2.24
1.69
2.14
2.06
1.81
1.77
1.46
1.05
1.14
1.18
1780
1.16
0.95
1.24
1.12
1.30
1.69
1.39
1.03
1.53
1.26
1790
1.24
1.59
2.15
1.74
1.41
1.33
1.33
1.35
1.28
1.30
1800
1.32
0.92
1.17
1.18
1.29
1.40
1.28
1.26
1.43
1.44
1810
1.48
1.54
1.60
1.89
2.02
1.74
1.87
1.41
1.66
1.48
1820
1.52
1.47
1.44
1.29
1.22
1.61
1.62
1.61
1.72
1.76
1830
1.84
1.96
2.46
1.99
1.23
1.49
1.53
1.34
1.64
1.54
1840
1.95
1.59
1.82
1.48
1.32
2.16
1.65
1.73
1.57
1.20
1850
1.36
1.49
1.45
1.82
1.67
2.18
1.67
1.48
1.45
1.17
1860
2.39
1.87
1.45
1.40
1.79
1.26
1.42
1.28
1.79
1.98
1870
2.86
2.24
2.36
2.60
1.59
2.33
1.90
2.01
2.26
2.22
1880
1.78
2.08
1.66
1.75
2.24
2.32
1.67
1.50
1.47
1.62
1890
1.48
1.70
1.82
1.97
2.18
1.91
1.81
1.71
1.69
1.74
1900
2.28
1.65
1.60
1.77
1.48
1.70
1.61
1.62
1.37
1.02
1910
1.22
1.03
1.22
1.42
1.50
1.26
1.06
0.84
0.80
1.03
1920
1.07
1.12
0.95
1.18
0.57
156
CLIMATIC CYCLES AND TKEE-GROWTH
Big Creek, California (BC), 5 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1700
• •
0.80
0.60
1.08
0.58
0.70
0.73
0.60
1710
1.12
1.05
1.12
1.00
1.18
0.93
1.18
1.38
2.40
2.10
1720
2.22
1.53
1.66
1.89
1.56
1.85
1.97
1.82
1.45
0.96
1730
1.84
2.11
2.15
1.59
1.94
1.71
1.95
1.89
3.18
2.60
1740
3.56
3.05
3.22
2.94
3.19
3.42
4.08
3.62
3.24
2.84
1750
2.86
2.81
2.43
2.18
2.48
2.11
1.81
1.90
1.86
2.41
1760
2.62
2.72
2.06
2.27
1.89
2.10
2.68
1.82
2.26
2.87
1770
2.62
3.28
2.36
3.13
2.70
1.88
1.63
1.13
1.71
1.70
1780
1.96
2.06
1.70
1.32
2.57
2.55
1.84
1.93
1.52
2.39
1790
2.71
2.12
2.29
2.22
1.59
1.13
1.68
2.05
1.76
2.17
1800
1.98
2.38
2.36
2.20
2.24
1.97
2.18
2.62
2.16
2.04
1810
2.95
2.44
1.77
2.47
2.32
2.53
2.45
2.06
1.92
1.92
1820
1.79
1.66
1.63
1.77
1.58
2.16
1.89
1.78
2.02
1.23
1830
2.28
2.00
1.75
1.91
1.65
1.78
2.25
1.42
1.64
1.68
1840
1.84
1.26
1.45
1.22
0.87
1.67
1.22
1.14
1.17
1.06
1850
1.39
1.41
1.44
2.00
1.61
1.59
1.78
1.52
1.32
1.54
1860
2.03
1.56
1.28
1.13
0.78
1.35
1.29
1.24
1.70
1.55
1870
1.54
1.64
2.52
1.62
1.46
1.83
1.46
1.26
1.87
1.19
1880
1.08
1.17
0.83
0.80
1.53
1.14
0.98
1.00
1.06
0.99
1S90
1.38
1.27
1.04
1.34
1.36
1.55
1.43
1.70
1.15
1.23
1900
1.28
1.52
0.93
1.11
0.99
1.37
1.21
1.42
1.14
1.28
1910
1.46
0.93
0.72
0.93
1.38
1.03
1.04
0.98
1.03
1.09
Springville Pines (EP), 8 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1720
0.70
0.62
0.90
1.18
0.65
0.72
0.78
0.90
0.65
0.51
1730
0.68
0.50
0.70
0.85
0.62
0.65
0.70
0.55
1.00
0.68
1740
0.62
0.92
0.82
0.62
0.78
1.05
0.70
0.92
0.92
0.85
1750
1.12
0.85
0.85
1.00
0.65
0.51
0.65
0.72
1.08
0.85
1760
0.78
1.25
0.92
1.15
1.05
0.92
1.33
1.22
1.40
0.73
1770
0.92
1.12
1.21
1.52
1.52
1.50
1.29
0.60
0.78
0.92
1780
1.01
0.73
0.96
0.51
0.62
0.92
0.94
0.91
0.74
0.89
1790
0.97
1.31
1.35
1.12
1.25
0.73
0.64
0.93
0.94
0.84
1800
1.08
1.07
1.15
1.51
1.36
1.37
1.16
1.17
0.89
0.94
1810
0.92
1.15
0.70
0.97
0.93
1.02
1.18
0.87
1.28
1.20
1820
0.90
1.09
0.65
0.64
0.63
1.02
1.24
0.98
1.28
0.94
1830
0.98
1.21
1.27
0.87
0.64
0.79
0.84
0.80
1.01
1.11
1840
1.22
0.62
0.88
0.67
0.61
0.90
0.54
0.49
0.54
0.67
1850
1.04
1.07
1.23
1.37
1.06
1.59
1.14
1.06
0.57
0.64
1860
1.03
0.95
0.79
1.02
0.52
0.81
1.05
0.97
1.25
1.43
1870
1.07
1.18
1.35
1.04
0.93
1.13
0.86
0.91
1.11
0.98
1880
0.66
0.97
0.91
1.02
1.07
1.79
1.42
1.04
1.07
0.80
1890
0.74
0.92
0.87
1.08
1.18
1.28
1.02
1.19
0.89
0.85
1900
1.04
0.89
0.90
1.16
0.94
0.88
1.01
1.16
1.09
1.32
1910
1.14
0.84
0.74
0.78
0.85
0.77
0.91
0.85
0.66
0.71
1920
0.73
0.72
0.69
0.88
0.56
Mount Wilson, California (W), 8 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1720
10.40
11.00
9.10
9.10
5.90
1730
6.00
8.90
6.30
8.10
7.10
5.90
6.35
7.00
5.80
6.10
1740
6.70
7.90
7.75
6.60
5.85
8.95
7.05
8.45
7.60
8.90
1750
4.75
5.15
6.80
4.20
3.30
6.10
4.55
5.85
6.25
5.15
1760
6.30
7.60
5.85
7.30
9.35
5.85
8.70
7.25
8.55
6.61
1770
7.10
7.23
5.52
6.20
6.25
5.62
5.12
4.57
5.40
5.50
APPENDIX
157
Mount Wilson, California (W), 8 trees — Continued
A.D.
0
1
2
3
4
S
6
7
8
9
1780
6.13
7.00
5.37
5.30
7.00
6.70
4.30
5.12
4.65
5.22
1790
5.32
4.90
6.45
5.97
4.45
2.88
2.77
4.60
3.77
5.47
1800
5.60
5.77
7.15
6.12
8.50
7.65
5.85
4.67
7.05
6.05
1810
5.75
6.15
4.56
4.72
4.42
5.49
5.34
4.81
6.86
5.40
1820
6.25
5.08
5.00
4.11
3.93
4.83
5.83
5.10
5.43
5.16
1830
4.86
4.63
5.98
4.26
3.85
4.41
4.00
4.96
4.91
5.26
1840
5.71
3.70
4.51
3.16
3.61
3.97
4.13
4.13
3.37
3.80
1850
4.55
4.45
4.70
5.06
4.99
6.50
2.79
2.81
3.46
4.82
1860
5.26
4.71
5.66
5.26
3.42
4.15
4.67
4.32
5.92
5.75
1870
6.21
5.01
5.46
5.49
5.12
5.70
4.86
4.01
4.93
4.42
1880
3.05
4.52
3.87
4.31
4.17
4.67
4.042
4.25
3.57
3.48
1890
4.89
5.11
4.62
4.63
4.18
4.27
3.85
3.60
3.96
2.77
1900
5.22
4.91
3.75
3.89
3.72
4.47
5.18
4.68
5.63
3.51
1910
3.38
3.17
3.93
3.85
3.91
4.25
4.45
4.81
3.76
4.47
1920
4.45
5.16
4.75
4.90
3.27
3.03
San Bernardino (SB) , 6 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1810
1.88
1820
1.39
0.90
1.24
1.72
1.38
2.03
2.16
1.81
1.54
1.98
1830
1.74
1.54
1.51
1.50
1.02
1.41
1.36
1.19
1.17
1.25
1840
1.06
0.77
0.85
0.92
0.98
1.20
1.67
1.56
1.31
0.92
1850
1.10
1.27
1.30
1.88
1.22
1.67
1.08
0.94
1.15
1.14
1860
0.88
1.02
0.87
1.00
0.82
0.79
1.18
1.16
1.15
1.06
1870
1.06
1.23
1.66
1.60
1.77
1.66
1.22
1.09
1.17-
0.93
1880
0.65
0.93
0.73
0.89
0.77
1.03
0.75
0.65
0.73
0.86
1890
0.85 +
0.97
0.92
0.95
0.98
1.13
1.09
1.11
1.22
1.03
1900
1.42
1.41
1.07
0.91
1.03
0.76 +
0.88
0.89-
0.89
0.79
1910
0.74
0.71
0.88
0.92
1.03
0.76
1.07
0.86
0.80
0.83
1920
0.94
1.11
Charleston
Nevada (CH), 8 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1700
2.70
1.78
2.43
1.03
2.18
1.78
1.73
1.03
1.47
1.40
1710
0.95
1.13
1.22
0.82
1.12
1.07
0.61
0.83
1.00
1.08
1720
1.72
1.33
0.92
1.84
1.36
1.52
1.94
1.65
1.83
0.61
1730
1.54
1.26
1.44
1.41
1.38
1.12
0.63
1.00
1.51
1.05
1740
1.19
1.21
1.41
1.69
1.86
1.55
2.23
2.09
1.37
1.53
1750
2.00
1.54
1.23
0.77
0.72
0.73
0.99
1.09
1.37
1.73
1760
1.78
2.27
1.63
1.34
1.39
0.59
1.63
1.64
1.80
1.26
1770
1.39
1.55
1.77
1.35
2.28
1.82
1.90
1.27
1.09
1.19
1780
1.60
1.59
0.77
1.10
1.80
0.84
1.25
1.06
0.65
1.04
1790
1.02
1.14
1.59
2.10
1.66
0.36
0.64
1.15
0.97
1.52
1800
1.10
1.08
1.27
1.12
1.25
1.02
1.46
0.72
1.05
0.56
1810
0.69
1.09
1.20
0.51
0.82
0.79
1.06
1.06
2.13
2.43
1820
2.59
2.42
1.27
0.93
1.49
1.52
1.92
1.34
1.87
1.32
1830
1.57
1.58
1.88
1.55
1.42
1.43
0.65
1.66
1.57
1.90
1840
1.59
0.75
1.08
1.21
1.04
0.99
1.32
0.86
1.34
1.17
1850
1.29
1.04
1.42
1.76
1.84
1.70
0.78
0.26
0.79
0.88
1860
1.03
1.33
1.60
1.35
0.89
1.37
1.90
1.94
2.15
1.66
1870
2.18
1.76
1.38
1.66
2.08
2.11
1.88
1.59
1.67
0.95
1880
1.02
1.06
1.03
0.92
0.97
1.27
0.87
1.44
1.28
1.46
1890
1.49
1.78
1.86
1.86
2.11
1.72
1.13
1.54
1.24
0.53
1900
0.77
1.11
0.98
1.07
1.40
1.33
1.69
1.63
1.97
1.83
1910
1.62
1.53
1.55
1.59
1.67
1.37
1.63
1.61
2.20
1.74
1920
2.05
2.40
2.47
2.60
158
CLIMATIC CYCLES AND TREE-GROWTH
Pine Valley,
California (PV), 4 trees
A.D.
0
1
2
3
4
5
6
7
8
9
1730
. >
....
1.65
1.33
1.25
1.02
1740
1.33
i.ii
6.67
1.34
1.29
6.87
0.71
0.43
0.53
0.25
1750
0.47
0.52
0.61
0.55
0.88
0.93
1.10
1.69
3.36
3.36
1760
4.20
3.67
2.86
2.30
2.32
1.40
3.44
3.60
3.50
2.56
1770
1.90
2.93
2.45
1.90
3.14
2.39
2.20
1.56
1.39
1.19
1780
1.06
1.49
0.58
1.40
2.19
1.52
2.75
2.82
1.84
1.65
1790
1.26
1.07
0.60
1.89
1.86
1.68
1.52
1.33
1.00
1.22
1800
1.25
1.46
2.16
1.90
1.50
1.97
1.29
1.21
1.67
1.16
1810
1.31
1.65
1.42
1.36
2.28
2.40
2.58
2.57
2.24
2.77
1820
0.95
1.30
0.85
0.55
0.62
1.10
1.46
1.16
2.10
0.64
1830
0.83
1.32
1.25
1.91
1.23
1.28
1.25
1.28
1.31
1.40
1840
1.25
0.81
1.39
0.55
0.65
0.51
0.99
0.85
1.18
1.15
1850
1.18
0.90
1.56
1.99
1.09
1.47
0.73
0.63
0.75
0.82
1860
0.95
1.09
1.39
1.22
0.88
1.27
1.23
0.92
1.41
1.48
1870
0.72
0.91
1.06
0.37
0.64
0.65
0.68
0.49
1.27
0.46
1880
1.19
1.16
0.61
0.59
0.90
1.20
1.27
1.29
2.04
1.63
1890
1.12
1.52
1.39
1.25
1.07
0.95
1.06
1.27
1.00
0.57
1900
0.67
0.84
0.53
0.41
0.21
0.64
0.64
0.59
0.72
0.89
1910
0.98
0.92
0.66
0.81
0.69
0.84
1.11
1.18
1.05
1.21
1920
1.38
0.93
1.28
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QK
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