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Forest distribution in the northern Rock

Cornell University

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the United States on the use of the text.

http://www.archive.org/details/cu31924002876815

PRESS OF
MISSOULIAN
PUBLISHING
COMPANY

MISSOULA
MONTANA

FOREST DISTRIBUTION

IN THE

NorRTHERN Rocky MOUNTAINS

Vig. 31. Larch (Larix occidentalis) and pine (P. ponderosa)

forest along east shore of Flathead Lake. Undergrowth J//olodiscus
ariacfolius, Ceanothus sanguineus, Lepargyraca Canadensis, ete. June.

UNIVERSITY OF MONTANA. STUDIES

Forest Distribution

in the

Northern Rocky Mountains

By

J. E. KIRK WOOD

Professor of Botany in the State University of Montana

STATE UNIVERSITY
MISSOULA, MONTANA

JUNE, 1922

Bulletin No. 247—-State University Studies Series No. 2

Published bi-monthly at Missoula, Montana. Entered as second-class
matter at the postoffice at Missoula, Montana, under act of Congress,
August 24, 1912.

THE UNIVERSITY OF MONTANA

Epwarp C, ELLioTT. Chancellor of the University

The University of Montana is constituted under the provisions of Chapter
92 of the Laws of the Thirteenth Legislative Assembly, approved March 14,
1913 (effective July 1, 1913). i

The general control and supervision of the University are vested in the
State Board of Education. The Chancellor of the University is the chief
executive officer. For each of the component institutions there is a local
executive board.

Montana State Board of Education

J. M. Drxoyn, Governor Ex-officio, President
W. D. Rayxkry. Attorner General Ex-officio

May TRUMPER, Supt. of Public Instruction_............ Ex-officio. Secretary
As Je VIOLETTE ygs.. ences. (1922) WHITFIELD SPADN..WW.2... (1924)

... (1922) J. W. FREEMAN.
JOHN DIETRICH...
FRANK ELIEr

The University comprises the following institutions, schools and depart-
ments:

The State University, Missoula
Established February 17, 1893, and consisting of

The College of Arts and Sciences The School of Business
The School of Law Administration

The School of Pharmacy The Summer Quarter
The School of Forestry The -Biological Station

(Flathead Lake)
The Public Service Division
The Graduate Division

The School of Journalism
The School of Music

Charles H. Clapp President

The State College of Agriculture and Mechanic Arts, Bozeman
Established February 16, 18938, and consisting of

The College cf Agriculture The School of Music

The College of Engineering The Summer Quarter

The College of Applied Science The Secondary School of Agricultu-e

The College of Household and The Agricultural Experiment Station
{Industrial Arts

The Agricultural Extension Service
Courses for Vocational Teachers

Alfred Atkinson. President

The State School of Mines, Butte
Established February 17, 1893
Course in Mining Engineering Course in Metallurgical Engineering
Bureau of Mines and Metallurgy

George W. Craven. President

The State Normal College, Dillon
Established February 23, 18938, and consisting of

The Teachers’ Certificate Course The Two-years Course
The Three-years Course The Rural Teachers’ Course
The Course for Supervisors The Teachers’ Service Division

Sheldon E. Davis. President

For publications and detailed information ecncerning the different schools
and colleges address the president of the particular institution concerned.
Communications intended for the Chancellor of the University should be ad-
dresssed to the State Capitol, Helena, Montana.

PREFACE

It is the purpose of the following pages to present a general
account of the forests of a region comprising about 175,000 square
miles lying across the Rocky Mountains south of the 49th parallel
and marked by great diversity of topography, soil and climate.
The many factors involved in the development and maintenance
of the present physiognomy of the vegetation merit careful study,
both as to the sources whence its component parts have been
derived and as to the agencies and conditions at present effective
in their local movements and inter-relations. It is designed to
open the way to a critical study of this area and to emphasize
the point of view from which this and all other such studies
should be approached.

The usual approach to the study of problems in eealens
both in matters of association and succession and of local and
general distribution has up to the present time been mainly
from the side of the physical factors involved, and hardly, if
at all, from the standpoint of individualities of the species con-
cerned. It is the intention herein to lay particular emphasis
upon the latter and, while taking account of the climatic and
topographic influences, to stress those characteristics of the most
important species as far as known, as furnishing the clue to the
solution of problems of competition and dispersal. It is but a
truism to say that the fuller the knowledge of the specific pe-
culiarities of a plant the more may its place in the flora be
understood.

Acknowledgment of valuable suggestions and criticisms of
the manuscript by Prof. John W. Harshberger of the University
of Pennsylvania and Dr. Forrest Shreve of the Desert Laboratory
of the Carnegie Institution of Washington is due and is hereby
gladly rendered.

; J. E, Kirxwoop.
Missoula, Mont., May 1, 1922.

CONTENTS

Page

THEO GULCH Ons ss ah oy ale aa assole do uaa 15
Pont OP vie We 5 sos ep es oe Se ore 15
Harly collectors........2.222202.1.2cccsceeecececececeeeececeeeeeeeeteeeeeneeenes 16
Tiarter:: COlleetorgsgxsms saa is A ees ett pase eens eae 19
Routes of early travel... ceececceccecc eee eeeeteeeeeeeeeee 20

B05 gy) -9 210) 0s Sates et Sane eet ets reed meee 24
Mountain ranges and altitudes.....0..000.00.20.2.22cc2ceeeeeeeeeeeee 24
Geology and soils... ccceccecetceccceceeec cece cee ceceteeneeceeneneenees a4
Rivers and drainage 2... eee ce cee eeeee eects 35
arin aC, sc a a nO eee nn om ec etna racen SemcneeaeS 39
recr pil atl OM isc wee a eet ee ee a ee 39
Relative humidity... occ cece eee eeeeeeee 45
Mem pera turessacc 58 ise ie eect 49

IME Pa GON ae: init ooo Goce po eee een ee a ee 62
A oy <(5 IRs 0) 04k eae me NO Og RRL ee SR De SR MRE OSES OR oeene COTE 62
Alpine? Ploraiccs i236: eres st oe kia Rises Bech See at 64
Transcontinental species _.......22.2.2..2-c-ece cece eee 66
The eastern element....0...0....0.0 ce cee eee ccc e teens 66
The western element............20...-22.22:2.ceccecceececeeceeceeceeteeeeneeee 68
The southern element. ........2.20.2..2020cc eee eee cece eee 73
General forest aspects. ......22.22212-c2eeceeceeeeee ee ceeceeeeeeeeeeeeeeeeeeeeeneee 75
UIST G8" SPC CLC se sca a eaten 76
Sectional areas) 222222060 area eee 78
Forest zones and formations.._....22222222.2:.20c-ceseecceceeeeeeeeeeeeceeeeees 95
The foothill transition forests..........2..2..2..22.222202200200000200-- 101
The ‘‘slide-rock’’ stiecessiOn..........22.222.2.22:02:2:ceeceeceteeteeeeeee 114
The humid transition—western valleys...............2----------+ 118
The mountain forests.............22.2..22-2222:02:0202000eeeeeeeeeeeeeeeeee 137
Whe: SUM Mts. 255s ae sees eae ese ei caseeweeeee te 159
Sumima ny cece os oe esate tue eas Seca etla 169

TiitOPAatire: 62s he pans oee aes eee ee 175

Figure Page
1. Routes of early exploration in Montana... 22
2. Physiographie map of Montana... 022 26
3. Profile Idaho-Montana topography on the parallel

48 degrees 30 minutes... cee cence 30
4. Profile Idaho-Montana topography on the 46th parallel 32
5. Profiles of certain mountain ranges in Montana............ 36
6. Chart of Mcntana showing direction of prevailing winds 40
7. Diagrams showing monthly distribution of precipita-

{10m iy On bali aly) ecomomy 44
8. Mean temperature diagrams for the vear. Distrib-

TE 2 Est] 0 21610. 0 Yen ete eR ee 48
9. Mean temperature diagrams for the year at two stations

near the same meridian, but 200 miles apart................ 54
10. Chart showing temperature, relative humidity and.

precipitation at Missoula, 191122022... eee eee 56

11. Isotherms for mean temperatures in Montana, 1911... 60

12. Forest sectional areas............2.22.222..c2:cecceeceeeeeceeeeeeee eee 78

13. Badlands near Glendive, Montana.........00020022:00-ee 98

14. Vegetation of the rimrock near Roundup, Mont............. 104

15. Alluvial bench along the Musselshell, near Melstone,

NG i tent eh ce Ao rs a ss ee ee 108

16. Populus Sargent along the Musselshell...........0....2...---. 112

17. Yueca glauca near Forsyth, Montana.......2000.002.02--- 116

18. Buffalo berry along the Milk River... 120

19. Vegetation on south slope near Havre, Montana............ 122

20. Creeping Juniper on plains near Havre.............22--- 124

21. Junipers near Boulder, Montana..............0..0.0.2.2.22.22-2+---- 126

22. A western slope near Missoula, Montana...................---- 128

23. A high landscape on the East Fork of the Bitter Root.... 130

24. <A southern slope in the Lolo VWalley..........0.2.2:::-2---- 132

25. Opposing slopes on the East Fork of the Bitter Root...... 134

26. Cercocarpus ledifolius on south-facing blufgf.................. 136

ILLUSTRATIONS

ILLUSTRATIONS (Continued)

Figure Page
27. South exposure in upper Bitter Root Mountains............ 138
28. Yellow pine on Wildhorse Island in Flathead Lake........ 140
29. In the valley of the Swan River. 142
30. In the Priest River Valley in northern Idaho.................. 144
31. Larch and pine on the east shore of Flathead Lake
Frontispiece
32. A mountain valley in the upper Bitter Root.................. 146
33. Distribution of larch along snow drifts.......................... 148
24. A north mountain slope near Missoula.................-...-.---- 150
35. Encrusting lichen vegetation on the talus........................ 152
36. A ‘‘slide-rock’’ slope in the upper Bitter Root............ 154
37. Pure stand of Engelmann spruce in Avalanche Basin.... 156
38. Western slope of the Mission Range overlooking Flat-
head Lake........ 158
39. A burn being reoccupied by lodgepole pine..................-- 160
40. Lodgepole forest at top of Continental Divide............... 162
+1. Summit of the Bitter Root Mountains... 0. 164
42. A typical sub-alpine park in the Swan Range in July... 166
43. At an altitude of 6200 feet in the Swan Range.............. 16s
44. A cirque lake in the Swan Range... 170
45. Section of stem of small fir showing rate of growth...... 172

INTRODUCTION

HE following discussion of the distribution of forests is
[ concerned with that part of the Rocky Mountain region
and neighboring plains which is ineluded within the
State of Montana and adjacent parts of Idaho. These boun-
daries furnish a convenient definition of an area which presents
certain aspects of forest, vegetation and which by reason of its
extent and location exhibits features of special interest. Here
on both slopes of the main divide appears a wide overlapping
of the Atlantic and Pacific floras and, while the hemlocks,
larches and some other forest species of the north reach their
farthest southward extension in the Rocky Mountains, they too
overlap, though at different elevations, the most northward
reaching elements of the southern vegetation as represented by
eactus, yucca and other forms. Moreover, factors influencing
the local distribution of species more widely prevalent are mod-
ified at least in their intensity by latitude, altitude and other
causes.

The complex interaction of climatic, edaphic, biotic and
other influences which guide and control the distribution of
species is of keen interest to the student of phytogeography, and
no treatment of the subject is fair which does not seek to give
full weight to the many factors involved, and especially to the
nature and requirements of the individual species. Similarly
the ecology of local areas must be studied closely from the
standpoint of the adaptability and demands of the species of
those areas, if lasting results of importance are to be obtained.
All questions concerning the dominance of some species and the
suppression of others are questions of the interaction of the
constituent species and their environment.

Among such questions are the specific light, moisture and
temperature requirements at different stages of development and
under particular conditions, the rate of growth and the form
during youth and maturity, the form and extent of the root
system, its strength, functional activity and relation to the soils
of particular composition and structure, the reproductive ca-

15

16 FOREST DISTRIBUTION

pacity of the species, including not only the amount of seed and
the frequency of seed vears. but the comparative ages at which
seeds are produced, their viability. their mode of dissemination
and germination and the time involved, the requisite conditions
of successful pollination, etc. In addition to these factors must
be considered the matters of specific protoplasmic functions,
such as resistance, or susceptibility. to the attacks of destructive
insects, or fungi, the range of adaptability in relation to climate
and soil. Only by an appreciation of the value of these and
other factors can the relative importance of a2 species in any
given area be fully understood. Furthermore. it would seem
that no estimate of the influence of these causes is adequate
which does not take some account of the time during which the
various influential factors have been operative.

The immensity of the task involved in the thorough study
of the vegetation of an area becomes the more apparent when
we reflect that native vegetation is dynamic. not static. and
that the changing quality of the soil through long periods of
time is attended by conspicuous changes in the plant covering.
Our knowledge of the ecology of a region or locality must in the
end be a product of our knowledge of the separate units (species)
of that area. It seems, therefore, important that the study of
plant geography, or ecology, be approached primarily from the
standpoint of the species and merely incidentally from that of
the physical conditions.

It is the aim of this paper te present an introduction to the
subject of forest distribution in a portion of the northern Rocky
Mountains, with a few tentative conclusions. and to point the
way to a more thorough study, the results of which should be
of importance, both in their scientific and their economic as-
pects.

Up to the present time. the flora of Montana has been
studied chiefly from the standpoint of the systematist. More
than a century of botanical exploration, from the time of Lewis
and Clark to the present day, has made known to us the prin-
cipal components of its flora. The first collection within the
region was that of Meriwether Lewis in 1806, who traversed the
northern part of the State from Lolo Pass in the Bitter Root
Range through the Hellvate and Blackfoot country via Sun

INTRODUCTION 17

River to the Missouri near the Great Falls and thence down the
river.

Meehan (42), speaking of Lewis collection, says, ‘‘From the
few (plants) they did collect, Pursh (47) in his ‘Flora Americae
Septentrionalis,’ published in London in 1814, refers to 119,
many of which he described as wholly new.’’ He quotes from
Pursh as follows:

‘‘The collection was made during the rapid return from
the Pacific. A much more extensive one made on their slow
ascent toward the Rocky Mountains and the chains of the north-
ern Andes, had unfortunately been lost, by being deposited
among other things at the foot of these mountains. The loss of
this fine collection is the more to be regretted when I consider
ihat the small collection communicated to me, consisting of abont
150 specimens, contained about a dozen plants well known to
be natives of Northern America.’’

The plants were probably taken to England by Pursh and
finally deposited in the herbarium of A. B. Lambert. Afterward
they found their way into the possession of the Academy of
Natural Sciences of Philadelphia and the American Philosophical
Society. The plants collected on the outgoing trip between St.
Louis and Fort Mandan were sent back and received by the
Society November 15, 1905.

Among the weody plants of the region collected by Lewis
are the following:

Pachystima Myrsinites Raf.

Ceanothus velutinus Dougl.

Rhamnus Purshiana D. C.

Amelanchier alnifolia Nutt.

Crataegus Douglasti Lindl.

Sorbus sambucifolia (C & N) Roem.

Prunus demissa Nutt.

Spiraea discolor Pursh

Philadelphus Lewisit Pursh

Ribes aureum Pursh

Ribes viscossisimum Pursh

Lonicera involucrata Banks

Artemisia cana Pursh

Elaeagnus argentea Pursh

18 FOREST DISTRIBUTION

Shephcrdia argentea Nutt.

Populus trichocarpa Torr & Gray

Pinus ponderosa Dougl.

Juniperus communis L.

Juniperus horizontalis Moench.

From the time this collection was made it was nearly 30
years before another observation was made upon the flora of the
State of Montana, unless we except the visit of David Douglas
who at least approached the western boundary in 1826. In
1833, however, Alexander Phillip Maximilian (41), Prince of
Neuweid, made notes on the vegetation from Fort Union, near
the mouth of the Yellowstone. up the Aissouri River to the
mouth of the Marias. In the ravines at Fort Union. he observed
thickets of oak, elm, box elder. and bird cherry (probably Prunis
Virginianad L). On the banks of the Missouri were poplars,
willows, ash, elm, box elder, ete.. with a thick undergrewth of
hazel, roses and blackberry. The occurrence of oak, e'm, and
ash is to be expected along the Missouri bottoms but the pr2sent
bourdary of Montana is about the western limit of their range.
it is doubtful if they have since been reported in Montana.

Wveth’s journevs to Oregon begun, in 1832 and occupying
about three vears, (45). followed a route via (reen River and
the Snake south of the region here considered, but approaching
the western border in Eastern Idaho. On the second of these
trips (1834), he was accompanied by Thomas Nuttall. There
appears to be no record of his collections on this trip. Wyeth,
however. on his return from the first expedition. is said to have
ascended the Clark’s Fork of the Columbia, thence southward
via the Bitter Root and the Big Hole to the Salmon River in
Idaho, and from there across to the Big Horn and the Yellow-
stone. His collections were described by Nuttall and are de-
posited in the Academy of Sciences in Philadelphia and the
New York Botanical Garden.

Charles A. Gever (19) in 1844 traveled over part of the
same route from Clark’s Fork to the Yellowstone and the plants
which he collected were taken to Europe, determined by Hooker
and distributed. At an earlier date, we have a record of his
survey of the vegetation of the Missouri River region in the
Dakotas in which he lists a number of plants common to Montana.

INTRODUCTION 19

David Lyall (36), Surgeon and Naturalist of the North
American Boundary Commission, visited Northwestern Montana
in 1861. His collections were distributed to nineteen important
herbaria. In discussing the region visited, he treats of the
Rocky Mountains (presumably the main range) and the Galton
Range between the Tobacco Plains of the Kootenai and the
Flathead Valley. He enumerates those collected between 4,000
and 8,300 feet elevation and mentions the following as occurring
in this region :

Pinus monticola Doug.
‘* contorta Loud.
flexilis James.
ponderosa Laws.
Larix occidentalis Nutt.
Lyallit Parl.
Pseudotsuga taxifolia (Poir) Britt.
Abies amabilis (Loud) Forbes.
«grandis Lindl.
Thuja plicata Don.
Juniperus scopulorum Sarg.

John M. Coulter (14), with the Hayden Survey in 1872-3,
collected along the Upper Yellowstone and later contributed the
first manual of the plants of the Rocky Mountains. Again in
1880, the Big Hole Basin and the Bitter Root were visited, this
time by Sereno Watson (4), who also made collections in the
Valleys of the Hellgate and the Beaverhead. Rydberg (4) from
1895 to 1897 covered much of the same ground extending: the
exploration northward as far as Deer Lodge, Helena and the
Judith Basin. From 1884 to 1904, Leiberg in the service of
the Northern Pacific Railway and later with the United States
Geological Survey made some collections within the State and
reported on the forests of the Little Belt (32), the Absaroka
(31), and the Bitter Root Mountains. Blankinship (4), while
Professor of Botany at the State College of Agriculture at Boze-
man, made large collections in various parts of the State from
1898 to 1904. These plants have been widely distributed and
are largely represented in the herbaria of the State institutions
at Bozeman and Missoula.

ee

ee

20 FOREST DISTRIBUTION

The largest contributions from the northern part of the
State have been made by R. 8. Williams and Marcus W. Jones.
Williams from 1880 to 1899 made extensive collections. confined,
however, mostly to the country about Great Falls and Columbia
Falls and the Highwood and Little Belt Mountains. Jones in
the subsequent period to 1910 collected largely in various por-
tions of the Flathead Valley from the Lake of that name to the
Glacier National Park and the higher altitudes of the Mission,
Swan and other northern ranges.

The earliest botanical explorations followed naturally the
lines of overland travel. The main highway through the north-
ern region then lay via the Yellowstone River, the Big Hole
Basin and the upper forks of the Missouri. The Continental
Divide was crossed at Gibbon’s Pass leading into the Upper
Bitter Root Valley. From that point, the trail followed the
Bitter Root River northward to its junction with the Lolo, thence
into Idaho via Lolo Pass to the Snake River. or continuing to
the mouth of the Bitter Root, and down the Clark’s Fork, or the
Clark’s Fork was left at a point near the present site of St.
Regis and a crossing effected into the Coeur d‘Alenes. This
route was subsequently adopted by the Government for a mil-
itary road (The Mullan Trail) from Fort Benton, the head of
navigation on the Missouri. to Walla Walla.

The various routes were old Indian trails. Lewis and Clark.
on their outward journey, followed one of the main highways
through the Big Hole. the Bitter Root and Lolo Pass. and on
the return by the same route as far as the Big Hole, except that
Lewis with a body of men parted company with Clark at the
Lolo and followed another highway via the Blackfoot Valley,
as above noted. The more southern route was followed by later
travelers, and collectors, at least in part namely, Wveth, Geyer,
Watson, Coulter and cthers. Later with the coming of railroads
a more general observation of the flora was made possible.

Many travelers, other than those noted above, might be
mentioned, who have contributed notes and collections on the
flora of the State from one point or another. Altogether. how-
ever, but few parts have been well worked over, many have
been superficially studied and some not touched at all. There
seems to be no available record of any botanical observations

INTRODUCTION 21

having been made in the Blackfoot Valley from the days of Lewis
and Clark to the present time, and probably the upper valleys
of the South and Middle Forks of the Flathead have never been
visited by a botanist. The latter represents an area some 200
square miles in extent and part of it is isolated, wild and in-
accessible. The Yellowstone Valley and the upper branches of
the Missouri, especially the Gallatin Valley, the upper valley of
the Clark’s Fork reaching to Deer Lodge with its principal
tributaries the Bitter Root and the Flathead and the regions
surveyed by Williams and Jones above mentioned constitute the
areas which have received most attention, yet even these, em-
bracing as they do hundreds of square miles, are yet imperfectly
known. The higher mountain ranges, especially the heights of
the Bitter Root Mountains which form a natural barrier to the
eastward migration of Pacific species, still furnish important
fields for investigation.

Systematic collections and description represent the most of
the work on the Montana flora and almost nothing has been
done on the phytogeographical and ecological aspects of the
vegetation of the region. <A series of brief contributions by
Rydberg (53-55), Whitford’s (73) study of the Forests of the
Flathead Valley, and the work by Leiberg (29-32) above referred
to represent about all of the literature on this phase of the
plant life of the Northern Rockies. Nothing has yet appeared
which attempts to relate the vegetation of the area within the
present boundary of Montana to the topographic and climatic
influences which have had so large a part in determining its
quantity and quality.

The area considered within the scope of this paper comprises
a wide belt across the northern Rocky Mountains mostly in
Montana. That portion of Idaho, adjoining on the west will
also be considered as floristically belonging to this region and
as possessing certain points of special interest in this connection.
The whole area covered by this paper covers about 175,000
square miles. It is unequally divided between prairie and forest,
the latter covering about 75,000 square miles. The prairies dif-
fer in their composition and topography and while representing
the typical condition in the eastern part of the State, they are
broken here and there by forest islands of greater or less extent,

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INTRODUCTION 23

and westward the prairie and forest alternate with frequency
depending in the main upon topographie variation. This di-
versification of the vegetation in response to topographic in-
fluence in its relation to climate is one of the most interesting
aspects of the plant life of the region, and one of the most
characteristic. This influence may, indeed, be said to be the
dominant one determining the physiognomy of the plant cover-
ing over all the western part of the State.

The flora of the northern Rocky Mountains has heen cited
as mainly a composite one and such is evidently the case. As
the first element may be considered those which are apparently
indigenous descendants or derivatives of a former more extensive
and probably more uniform vegetation of the Later Tertiary, and
those which in subsequent times have evolved from the species
from various sources in the migrations subsequent to the close of
the glacial period. Most of this region was glaciated and with
the recession of the ice was reoceupied from various centers of
distribution. We must believe that the forces which then oper-
ated in the dispersal of plant life over this area are, at least
many of them, still operative and that the invasions from the
east, southeast and west, which account for so large a part of
the Montana flora, are still in force. However slow the move-
ments of a species may be, in competition with others, in regions
already well occupied, there is no reason to believe that its
present limits of distribution are fixed.

The vegetation of Montana shows a distinct overlapping
of the eastern and western floras. The flora of the Pacific
Northwest is well represented on the western slopes of the
Rockies in Montana. The number of species, of course, dimin-
ishes eastward, vet some of evident Pacific origin have extended
their range to the Black Hills and the Great Lakes. Similarly
species of the Great Plains appear in the prairies west of the
Continental Divide.

In considering, therefore, the distribution and composition
of these forests, special emphasis must be laid on the one hand
on the specific individuality of the component species and on
the other on the combined influence of topography and climate.
As a basis for further discussion, the latter factors will be con-
sidered first.

CHAPTER I.

TOPOGRAPHY.

HE region here under consideration lies mostly between

| the 45th and 49th parallels of north latitude. Its width

from north to south is 276 miles, and, measured west

from the 104th meridian it extends 624 miles across the main

and secondary ranges of the Rocky Mountains. The tctal area

is close to 175,000 square miles. This embraces nearly all of

the State of Montana and includes a portion of eastern and
northern Idaho.

The mountain ranges of Montana have mostly a southeast
to northwest direction. They are thus essentially parallel with
valleys of greater or less width between. Most of these inter-
mountain valleys have in width from two to twenty miles of
river bottom and bench land, mostly the latter. which ascends
gradually or abruptly into foothills, behind which rise rugged
mountains, dissected by numerous strong tributaries of the main
streams. The valleys proper are but narrow strips as a rule in
the broad drainage basins of which they form a part.

The mountains and vallevs have been formed by successive
faulting and tilting on a grand scale. The eastern slope of a
range usually represents its fault face (7), the western slope
inclines more gradually to the foot of the next abrupt ascent.
Only two great mountain chains, however, figure conspicuously
as barriers in the spread of the flora of the state, the others are
of subordinate or negligible importance. One of these is
the Bitter Root Mountains and those shorter ranges to the north-
west in the same general alignment, the other is the Continental
Divide.

The eastern border of Montana on the Missouri lies 1898 feet
above sea level. From this point the land eradually rises to
the summit 400 miles to the west and drops down again to about
1800 fect where the Kootenai River crosses the western boundary
of Montana, the lowest point in the State. The altitude of half
the State or more is above 3000 feet. The highest point is

24

TOPOGRAPHY 25

Granite Mountain near Cooke, -just northeast of Yellowstone
Park, 12,847 feet (88).

The Continental Divide enters Montana on the north at about
the 114th meridian nearly 100 miles east of the western boundary
of the State. Its direction from that point is southeastward for
over 200 miles to a point near the city of Butte, where it swings
westward about 75 miles thence 100 miles southeast to the Yel-
lowstone National Park. In the north it is identified with the
Livingston Range which, with a rugged crest 7000-9000 feet
elevation, traverses the Glacicr National Park. Here it is mag-
nificent, precipitous and glacier-ridden, where the ‘‘Garden
Wall’’ thrusts a serrated sky-line between the eastern and west-
ern drainage. The altitude of the Divide, however, has a wide
range of variation. At Summit, where the Great Northern Rail-
way crosses, it has an altitude of 5214 feet. South of this point
it rises again to 8000 and 9000 feet with passes below 6000 until
it curves westward near Butte. From here to its junction with
the Bitter Roots it is relatively low (5500-7000) and is either
forested or denuded by fires. From this point to the Yellowstone
Park, the Divide, though somewhat higher, is rounded, broad and
may be traveled with comparative ease. Along the southern
boundary of the State it separates the waters of the Snake River
from the ultimate sources of the Missouri. The total length of
the Divide, from the northern boundary of Montana to the Yel-
lowstone Park, is upward of 500 miles.

The Bitter Root Range is variously defined. On some maps
it is shown as extending from Clark’s Fork of the Columbia to
Yellowstone Park, Lindgren (34) limits it to 60 miles, north
and south trend, from Lolo Pass to the Little West Fork of the
Bitter Root River. At this point the geological formations
change and southward the structure of the range identifies it
with the Rocky Mountains. This portion, generally included
in the Bitter Roots, is a northward projecting spur of the Main
Divide. With the Bitter Roots proper it forms a natural boun-
dary wall between Montana and Idaho, and divides the tribu-
taries of the Clark’s Fork, the Snake, and the Missouri.

The Bitter Root Mountains rise abruptly from the western
side of the valley of the same name. The crest of the range
lies at an average of about fifteen miles from the Bitter Root

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TOPOGRAPHY 27

River, and, especially in their southern part, the mountains pre-
sent high and rugged ridges and sharp summits, culminating in
Trapper Peak, 10,175 feet. From the ridge the slopes descend
more gradually to the Clearwater Mountains, which cover an
area some 70 miles east and west and 100 north and south.
The average elevation of the Clearwaters is about 7000 though
occasional summits rise to 8000 feet. The western border falls
abruptly to the Columbia Lava Plateau 3000 to 3500 feet. The
whole Clearwater series are but the remains of a dissected
plateau, now characterized by sharp ridges, jagged granite peaks,
innumerable and intricate canyons and chasms, wild and in-
accessible. The Clearwater Mountains, however, are important
from the standpoint of the flora, and, as we shall later see,
contribute an influence to the vegetation beyond their imme-
diate environs.

The Lolo Fork of the Bitter Root River marks the route of
the earliest travelers. It also marks the dividing line between
the Bitter Root Range and the Coeur d’Alenes. For about 75
miles north and northwest of this pass the character of the
topography assumes a different aspect. No longer a single high
barrier, but a broad, relatively low series of summits and ridges
about 6000 feet in elevation, and, like the Clearwater, dissected
by numerous channels. To the east. lie the open valleys of the
upper affluents of the Clark’s Fork, to the north the lower por-
tion of the same river, and to the west the lake country of the
Coeur d’Alenes and the Pend d’Oreille. The Coeur d’Alene
Range is not marked by the rugged features of the Bitter Root
and the Clearwater, but present rounded elevations and a more
hospitable aspect. The less forbidding nature of this range as
well as its lower altitude are facts which should be noted in
passing as having a bearing on the floristic features to be dis-
cussed later.

North of the Clark’s Fork the slopes rise abruptly to the
summits of the Cabinet Range, which extends to the valley of
the Kootenai. The trend of this range is from southeast to
northwest, and from the junction of the Flathead and the Clark’s
Fork to Bonners Ferry is about 100 miles. The Cabinets are
higher than the Coeur d’Alenes, some peaks rising to 8000 feet
and with a topography diversified, rugged and picturesque (7).

28 FOREST DISTRIBUTION

The northeastern portion of the range is more like the Coeur
d’Alenes, having somewhat the nature of a dissected plateau,
but the northern portion assumes the character of a more clearly
defined chain.

The Kootenai River enters Montana from the north. curves
to the west, then again to the northwest, and after a course of
about 80 miles passes over into northern Idaho. In the great
bend of this river lies the Purcell Range. These mountains are
of moderate height. pushing up to summits of 7500 feet, spread
rather widely acress the area included in the bend of the river
and serve to continue the general barrier along the western
boundary of Montana. This is further augmented by the Galton
Range which extends from the international boundary at the
crossing of the Kootenai to the head of Flathead Lake.

It will thus be noted that an almost continuous mountain
barrier extends from Yellowstone Park along or near the western
boundary of Montana, through most of its length essentially
parallel with the Continental Divide and about 100 miles distant
from it. The character and position of this barrier is a matter
of importance, as affecting the part between it and the Divide,
what is known as Western Montana, an area of about 22,000
square miles. Within this area are included some lesser ranges
of which two might be mentioned as adding certain topographic
features to the country west of the Divide. These two ranges
lie parallel and well within 50 miles of the main ridge. The
first. or more western, of the two is the Mission Range (15)
which extends for about 70 miles north and south and forms
the eastern wall of the lower Flathead Valley. The western
face is a fault scarp, the eastern slope is less abrupt. The crest
of the range is elevated to 9500 feet at the southern end, and
inclines gradually to the north where it sinks beneath a plain of
glacial gravels and silts. The southern peaks are rugged and
precipitous, deeply cut by numerous cirques and troughs of local
glaciers, but northward the lower summits are rounded and
heavily forested, the forest extending down to the very shures
of Flathead Lake. About midway of the range a bold terminal
moraine swings westward from the mountain base. shutting off
the waters of the lake on the north from the rolling prairies of
earlier glaciation on the south. Through this moraine the Flat-

TOPOGR.\PHY 29

head River at the outlet of the lake has cut its way toward its
junction with the Clark’s Fork some sixty miles to the southwest.

The second of these chains lies between the Mission Moun-
tains and the Divide, and between the Swan River and the
South Fork of the Flathead. It is called the Swan Range, is
somewhat longer than the Mission, merging at its southern end
with the plexus of ridges that form the three-way divide between
the waters of the Jocko, the Swan and the Blackfoot Rivers. It
is scarcely as high as the Mission Range in the southern portion,
but to the north sustains its elevation almost to the main chan-
nels of the Flathead River. Its peaks rise to 7000 feet more or
less and its sides are less precipitous than those of the Mission on
the west and of the main range on the east. It is practically
forested to the summit, but with here and there high, barren and
exposed ridges.

Having considered the mountain chains which lie west of
the Divide, there remain to be considered two or three areas on
the eastern side which have a part in the problem. The first
of these lies mainly in the southwestern corner of the State, in
the forks of the Missouri and among the higher tributaries of
the Yellowstone. This group includes the Beartooth, the Absa-
roka and Gallatin mountains and some lesser ranges. The second
group includes the Big Belt the Little Belt, the Crazy and the
Snowy ranges and covers an area roughly 10,000 square miles
in extent in the central part of the State, in the great bend of
the Missouri, north of the Yellowstone and about the sources
of the Musselshell. The third comprises the Bear Paw Moun-
tains, the Sweet Grass Hills and lesser elevations in the northern
part about the sources of the Milk River. The special features
of these will be taken in order.

The first group, embodving several ranges presents features
which seem to link it with the main backbone of the Rockies of
which it was apparently at one time a part. It includes lofty
and rugged peaks and deep, narrow gorges. The highest point
in Montana, Granite Peak, stands north of Yellowstone Park
and rises to an altitude of 12,847 feet. A high, plateau-like area
extends eastward, the Beartooth Plateau, furrowed, pitted and
covered by low buttes and rounded elevations. The plateau
varies from 10,000 to 12,000 feet in altitude, and slopes grad-

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30

TOPOGRAPHY 31

ually toward the valley of the Clark’s Fork of the Yellowstone.
The canyons in this section are often mere narrow rifts between
nearly perpendicular rock walls, which sometimes rise to nearly
3000 feet above the floor of the canyon, which here and there

is strewn with boulders and glacial debris.

Toward the west the country decreases in elevation. The
lowest canyons are 4000 feet above sea level and from that all
elevations occur up to 10,000 the usual elevations of the East
and West Boulder Plateaus. Here again glacial action has left
its traces, but not of such a character as to indicate that they
have been reduced much in height since the ice age began.
Through all this region of high peaks there is nct a snow cap,
so completely is the not too ample snow dissipated by the sum-
mer’s wind and sun. Some perennial snow fields lie in the lee
of high ridges and peaks where the winds have piled the snow
too deep for it to disappear entirely during the short summer.

In this group the Bridger and some lesser ranges form
lower plateaus or rounded ridges, forested to the summits, and
in outlines far less severe than those of their more lofty neigh-
bors.

In the second area are several groups of mountains which
constitute forest islands in the central part of the State. The
most western of these, the Big Belt Range, is the only group
which is extended in the form of a chain. They lhe parallel
with the main divide at a distance of 40 to 60 miles for nearly
100 miles in a direction from southeast to northwest. Through
the intervening valley flows the Missouri River in places through
narrow gorges which Lewis and Clark called the Gate of the
Mountains. East of the Big Belts are the Little Belts with
spurs radiating from a central elevation and supplying the
sources of Smith and Judith Rivers and other minor affluents
of the Missouri. South of the Little Belts at a distance of 50
miles more or less are the Crazy Mountains and east at about
the same distance lies the Snowy Range. These several ranges
are separated by valleys of greater or less agricultural possibil-
ities, and with broad rolling grassy uplands, which gradually
merge into sparsely timbered foothills. The higher elevations,
in conformity with meteorological conditions, support ample

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TOPOGRAPHY 33

forests. ‘The ranges here enumerated thus constitute forest
islands in the plains country.

Some peaks of this region rise to 9000 feet or more above
sea level. In the Little Belts, the central group of the area,
the average elevation is above 7000 feet. They are mainly
limestone uplifts, seamed by numerous dikes of eruptive rock
with extensive areas of metamorphics. The ridge crests are in
some places narrow, in others flattened out into plateaus, as at
the head of the Lost Fork of the Judith and even marshy in
others, as where the divide descends into what was originally
part of the South Fork of the Judith Basin. Some of the
secondary ranges are largely of ignecus rock. Ridges radiate
on the eastern slopes of the main axis into long spurs of narrow
and winding form which separate the streams flowing to the
Judith River. They are seldom high but are usually of low
and rounded contour. On the west the spurs are short and
steep and on the north they form a labyrinth of tortuous can-
yons. Many of the canyons throughout the area are narrow and
flanked by steep slopes or by limestone cliffs buttressed by talus
accumulations. Above they widen out into amphitheater-like
basins. To the north of this range a short distance stands a
small detached group, the Little Rockies which have an altitude
of 6500 feet or less, and support a forest growth.

To the east of the Belts the neighboring elevations of the
Snowy Range are separated from the former by Judith Gap, a
rolling and fertile prairie country. These summits have eleva-
tions of 4000 to 8000 feet and are themselves divided into two
groups, the Big and the Little Snowys. The latter is the more
easterly and represents the most distant outpost of the Rocky
Mountains with forest vegetation between the Missouri and the
Yellowstone.

The most southern members of this second general group
are the Crazy Mountains. They cover an area of some 360
square miles and reach an altitude of 10,000 feet. Geologically
and topographically they resemble the Absarokas of the southern
group, from which they are separated by the broad valley and
rolling grassy benches of the Yellowstone. They rise abruptly
from the plains and their rugged sides and sharp ridges ascend
to clear cut peaks often cloud-crested and mantled with snow.

34 FOREST DISTRIBUTION

The third group remains to be considered. From the Snowy
Range across the Missouri to the north, about 100 miles from
summit to summit, lie the Bearpaw Mountains. These are of
comparatively low altitude vet of sufficient elevation to support
forest growth. They practically constitute a culmination of the
divide between the Milk River and the Missouri. They reach
an altitude of 6000 feet and with the Sweet Grass Hills and a
few other low elevations represent almost the only forested slopes
within 100 miles of the main front of the Rockies in a strip 100
miles wide below the Canadian Boundary.

Geologically, of course. the State presents a great variety
of formations. The eastern half is mainly Upper Cretaceous
(with an extensive coal bearing portion) and Early Tertiary.
Later Tertiary formations appear in several isolated tracts in
the western part, occupying portions of the Flathead, Bitter
Root, Blackfoot, Big Hole. and other valleys. alternating in the
southwest and center with larger areas of the Paleozoic. The
northwestern portion from the Continental Divide to the boun-
dary and from the British possessions to the head of the Bitter
Root Valley is mainly Proterozoic (Algonkian). The Bitter
Root Range and the high mountains of the main divide about
Butte and southeastward through the <Absarokas are chiefly
granitic, but the northern ranges are sedimentary. Voleanic
rocks and lavas form a very small portion of the State.

The soils derived from these sourees are necessarily varied,
both locally and regionally. Over much of the eastern part of
the State the soil is of that comminuted variety known as loess
(18), in many places overlying glacial drift and now supporting
a typical prairie vegetation, mostly grasses. It is a fertile soil
and when broken up and sown to grains vields heavy crops.
Extensive glaciation characterizes the greater portion of the
State and morainie deposits are common (9). Many of these
are thinly covered with soil and, while fertile enough when pro-
vided with water, are usually dry and very difficult situations
for plant life. Deltas at the mouths of canyons. river bottoms of
silt, sand or heavy clay, and in varying areas and depths, form,
west of the divide, a limited part of the vegetation-bearing land,
composed of transported materials. The slopes which, in the
western portion of the State support nearly all the coniferous

TOPOGRAPHY 35

forests, are usually formed of fragmented rock, mingled with
the products of its decomposition and small additions of humus.
The different phases of vegetation on soils of this character are
usually expressions of reactions to moisture content in relation
to exposure.

While the uplands of eastern Montana are largely of fine
soil or gravels the bottom lands are often of fine heavy soil
commonly known as ‘‘gumbo’’ formed ‘by sedimentation from
decomposed shales (40). These in the aggregate involve a con-
siderable area. They are usually more or less heavily impreg-
nated with soluble salts and are the so-called alkali lands (52).
The salts most commonly present are sodium-chloride (very
slight) sodium sulphate, magnesium chloride, and calcium sul-
phate. Sodium carbonate is practically absent. Much of this
sort of soil is found in the lower Yellowstone Valley, where
strong erosive action is still going on, especially in the ‘‘Bad
Lands,’’ where the bluffs are dissected into a rugged wilderness
of hills and gullies.

Wind action also is still evident. Fantastic forms of
sandstone stand isolated here and there, caverns are carved in
the faces of cliffs, boulders are gradually reduced and obliterated.
Along the crumbling cliffs and on the margins of broken terraces
is a fringe of forest growth, scant, scattering and depauperate.
The benches above and below support only herbaceous or shrubby
vegetation. The stream bottoms invariably support cottonwoods
and other hard-wood species.

The eastern slope of the Continental Divide in Montana is
drained by the Missouri River, the western slope by the Clark
Fork of the Columbia. Along the peaks of the main and outlying
ranges are the innumerable sources of these streams; some take
their rise in high sub-alpine bogs and meadows, others flow
from cirque basins where quiet lakes lie under forested slopes.
Of these there are many of varying size and depth. Again
there are countless small streams that flow from melting snows
all summer, flowing freely by day and ceasing by night. The
slopes of all the ranges are thus watered abundantly; every
canyon has its brook or torrent which soon unites with others
forming swift, clear streams uniting into the main tributaries
of their respective systems (17, 49).

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Fig. 5. Profiles of certain mountain ranges in Mentana. Seale:
horizontal and vertical, 15 inch: about 5000 feet. ©, mean sen level.
A and I}. along the international border (49th parallel) from Kintla
Lakes to Belly River, across Glacier National Park and the Conti-
nental Divide. (, section of the Bitter Reot Range on the 46th
parallel; from the summit to the Bitter Root River. D, Continental
Divide on the 46th parallel. E, the Absaroka Range and the Yellow-
stone River on the 46th parallel. F,. the Crazy Mountains on the

46th parallel.
36

TOPOGRAPHY 37

The Missouri and some of its lesser affluents drain the
whole of the eastern slope of the Divide in Montana, from the
Milk River in the north to the ultimate sources of the Madison,
over 500 miles. The Jefferson, the largest of these mountain
tributaries, is formed by the Big Hole River and the Beaverhead
and carries the waters from 250 miles of the Divide, which
describes a wide and deep embayment, partly known as ‘‘The
Big Hole’’ and occupying the southwestern corner of the State.
The Jefferson, the Madison and the Gallatin unite at Three
+orks to form the Missouri and from this point on to the mouth
of the Dearborn there are no streams of considerable size. From
the south the Missouri receives the Musselshell which drains the
Crazy and the Snowy ranges, the highlands of the central part
of the State. Near the eastern boundary the Yellowstone River
enters but its waters have their sources mainly outside of the
State, in the Yellowstone National Park and in northern Wyo-
ming, although some are supplied by the Absaroka and the Bear-
tooth Ranges in the southern part of Montana.

On the western slope, from the northern boundary to the
head of the Bitter Root, somewhat over 300 miles, the waters
are gathered by the North, the Middle and the South Forks of
the Flathead, by the Blackfoot, the Bitter Root and the upper
source of the Clark’s Fork, commonly known as the Hellgate, all
uniting to form the Clark’s Fork which drains the whole of
western Montana beyond the Divide. This stream finds its out-
let through the narrow valley between the Coeur d’Alene and
the Cabinet Ranges and finally empties into Lake Pend d’Oreille.

The main sources of these rivers lie ultimately in the winter’s
snows. During the long winters these accumulate, more on the
western than on the eastern slopes, and as the warmth of summer
dissolves them their waters run off in torrents or, percolating
through the soil, feed the numberless springs and sources of the
small streams. In February the waters are low, but in June the
streams are at flood and their volume is increased as much as
70 fold as measured in second feet. Similarly, on the Atlantic
drainage the streams are swollen bv the melting snows but the
minimum may come in March or in August depending on the
location of the stream sources, and the maximum may occur ac-
cordingly anywhere from March to June. Measurements of flow

38 FOREST DISTRIBUTION

indicate that some of the streams at flood may attain more than
1000 times their low water volume, but more often the increase
is about 20 to 30 fold.

The tributary valleys of western Montana mostly have a
north and south direction and occupy trench-like depressions
between high ranges. The valleys are often or even usually
narrow, but occasionally broaden out into numerous inter-
mountain basins, as some parts of the Flathead and the upper
Blackfoot Valley. Some are the basins of old lakes with the
evidence of their ancient shore lines still intact. The positions
of the ranges and their alternating valleys in most cases is
squarely across the lines of eastward or westward movement.

CHAPTER II.

CLIMATE,

precipitation and temperature. Precipitation as the

source of nioisture is a matter of interest to be considered
in connection with its seasonal distribution, with soil structure
and composition, and with temperature, relative humidity and
other atmospheric conditions. Data upon most of these points
are available from records of the Weather Bureau, from over
90 stations fairly evenly distributed throughout Montana and
covering periods varying from three to thirty or more years (70).

Vv NHE climatic influences affecting vegetation are chiefly

The prevailing winds of Montana are from the west. Fig. 6
indicates the direction in different sections of the State. Tables
published by the Weather Bureau giving the usual wind direc-
tion by months at the numerous stations show west, northwest
and southwest with few exceptions throughout the year. Easterly
winds at times are strong, but such are usually of short duration.

On the western slope of the Divide the prevailing winds are
the bearers of rain, which comes chiefly in the cooler months of
the year. In this respect the climate of the western slope of
the Rocky Mountains is not essentially different from that of
the Pacific Coast west of the Cascades, except in the quantity
- of the precipitation. The seasonal features are much the same
on the whole, however, with lower minimum temperatures. On
the eastern slope of the Rockies, however, the rainfall features
are diametrically opposite. Here the principal precipitation
comes in the warmer months of the year, a fact of distinct ad-
vantage to the agricultural operations as well as to the native
vegetation of the Plains region, and of importance as linking the
climate of the eastern slope with that of the central states of
which it is logically a part.

A diagramatic representation of the distribution of rainfall
is shown in Fig. 7. The distribution by localities and seasons
is shown and it will be noted that at most of the stations on the
western slope (Plains, Missoula, Hamilton, Kalispell and Butte)

39

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40

CLIMATE 41

May and June are the months of heaviest rainfall, comprising
possibly as much as one-fourth the total of the year, and that
the months of July, August and September are comparatively
dry.

At these stations the precipitation during the growing sea-
son, from April to September inclusive, represents about 54%
to 63% of the total of the year. At some places, however, as
at. Troy, in the extreme western part of the State, the climate
more nearly approaches that of the Pacific Northwest, and of
the total annual rainfall (about 23 inches) about 35% only
occurs during the same period. On the eastern side of the
Divide the rainfall from April to September varies from 62%
to 82% of the year’s total.

The reason for the heavier precipitation during the months
of May and June on the western slopes of the Rockies is doubt-
less due to the altitude of the land and the coolness owing to
accumulated snows. During these months the snows are rapidly
melting, the rivers are at flood, and the air is more heavily
loaded with moisture. By the first of July the snows have
mostly disappeared, except from the highest peaks, and the tem-
perature of the whole region becomes noticeably higher. Through-
out the whole summer showers occur among the higher moun-
tains, but the valleys and foothills are usually almost rainless
during July and August. Most of the observation stations are
at moderate altitudes (2,000 to 6,000 feet) so that almost no
data are available from the higher ranges, either in winter or
summer,

Precipitation during the winter is usually in the form of
snow. Table 1 presents precipitation data, both rain end snow,
and the stations selected from various parts of the State afford
representative figures. Strange as it may seem, the snow fall
on the main range ef the Rocky Mountains is comparatively
light, notwithstanding their greater altitudes. This no doubt is
largely due to the Bitter Root and Cabinet Ranges to the west
where the snows fall to great depth. The figures from Saltese
and Snowshoe are far above anvthing that occurs on the main
Divide, being in the neighborhood of 12 feet for Saltese and 23
feet for Snowshoe. Butte, at an altitude of 5,716 feet, and
within a few miles of the Divide, has an average snowfall of
less than 5 feet. Philipsburg, at 5,275 feet, has 31‘, feet, while

fi

42 FOREST DISTRIBUTION

Table 1. Distribution of precipitation in Montana. From data fur-
nished by the Weather Bureau.

Lotal
Precipi- | Length Length
tation, of Altitude,| Average of
Place Inches, Record, Feet Snowfall,| Record,
Annual Years Inches Years
Mean
Western Montana H |
(Pacifie Slope) | |
Missoula 15.84 | 338 3212 | 34 23
Ovando 18.36 | 10 4101 | 69.8) | 9
BeNOR - csc Aotntedeceeus, [ 24.93° | 15 | 18sS0 6.3 | 11
Hamilton 10.71 1 BATS | Bt 7
Philipsburg 15.55 7 | APTS 42.2 6
Snowshoe 69.70 | 4 | 4500 | 2709 | 8
Kalispell 15.73 | 13 | 2965 42.1 10
Saltese _ 37.63 | 5 3600 142.3 | 5
Plains .. | 13.00 1) 2475 | 25.6 11
Butte _.. w! = TROS 14 | 5716 | ASS 14
Southwestern Montana | |
(Atlantic Slope) i | |
18.60 | ao 4878 TiAl 6
10.00 | 17 | 4920 | 30.4 | 9
17.20 | 10 147 58.2 9
Fort Logan 13.01 | 30 | 6000 FL. ae
Harlowton 15.50 | if 4165 59.9 | 6
Helena .... .| 121 ! 29 | 4110 5470229
Red Lodge.. » S085 6 | 5548 Lins 6
Virginia City. I 15.03 23 | 5880 aa
Yellowstone Park........) 18.97 19 | 6200 2),
North Central Montana!
(Atlantic Slope) : | |
Adel | 20.14. | A | Se 10
Babb... pase ay ! 103.7 3
Fort Benton. Las 50 34.2 7
Great Falls. 1048 | 24 411) dt
Havre oo... .! 13.63 30 37.0 | 10
Lewistown _.......... 19.77 14 | | 662 10
Northeastern Montana |
Chinook me ; ; 14 2502 27.5 Ss
Glasgow ooo eee | | 15 2002 25.5! 7
Glendive 2.00. ky | 20 © 2ono 2 ame bas
Jordan | | Di! DM 4 atetter © glia ae
Poplar Y 147 | 2020 415 13
Valentine ......... 4) y : Del lth atten ~ dae
Southeastern Montana’ il: |
Billings oes 14.96 16 3115 = ; 16
Crow Agenc | 1456 | 30 3041 | 489 | 30
Bkalaka ....... 15.41 DE OT eas ! 28.7 9
Miles City ... he 3 PAT1 272. 31
Wibaux 14.19 14 2674 306 | 9

CLIMATE 43

Ovando, at 4,101, has nearly six. It is a matter of further
interest in this connection to point to the snowfall in Yellowstone
Park at 6,200 feet elevation as being normally 814 feet and at
Red Lodge, 5,548 feet elevation in the Absaroka, 914 feet. Both
of these stations, which represent the highest east of the Divide,
are within 80 miles of the summit and in the direct path of the
southwesterly winds which sweep across the range at points un-
protected by any high barriers to the windward. The Bitter
Roots, which shelter the main divide further north, have no
influence here, having merged with the main range some 200
miles to the northwest.

If we reckon 10 inches of snow on an average as equal to
one inch of water, the equivalent of the winter’s precipitation
in acre feet would amount to a considerable volume in stream
flow and is important in its relation to power and irrigation.
It is an important, factor as related to the vegetation of the
region. In this respect, however, it is not equally distributed,
and much of it doubtless is lost by evaporation, but it is swept
by winds into gulches and into sheltered pockets in the lee of
peaks where, piled to great depths, it furnishes a constant supply
for innumerable streams throughout the warmer season. In this
form it is less significant to the vegetation of the crests and
exposed slopes, except as these are forested and so enabled to
hold the snows that they receive. In such cases, which are
numerous, the snows become of the utmost importance, and
furnish conditions highly favorable for certain species. he
countless lakes and streams fed by the melting snows furnish a
natural irrigation system, and by furnishing suitable habitats
for trees along their banks facilitate the spread of forests over
intervening and adjoining areas.

Locally rainfall conditions vary within wide limits. The
western slopes of the Bitter Roots are amply watered. The
rain bearing winds from the west sweep up their high inclines
and deposit their burden in frequent showers and heavy snows.
There is probably no part of the Rocky Mountains more heavily
watered than the higher Bitter Roots and their western slopes,
or with snows so deep. In the lee of this range lies the Bitter
Root Valley, and Hamilton, near the center of the Valley and
at the foot of the mountains on the east has an annual rainfall

Felleblesebolel ele ples as : ale
Reueeeeeeuey GESRaEsesaee gees /tey
HELENA HAMILTON MISSOULA PLANS
Patty HAIR Ts ee ee
ected likey as nla
Tat Meta Tat hatior TOE EE
EKALAKA MILES CITY JORDAN FORSYTH
aT 7 “4
3H ! - ee —-—4Jf-—---3
AT, Mirage sal op a Saplly oat pee ‘
2 r i : +
ed tas pee ee I
: ET) oT wlllttus. bttib LU Iiats ,
FT BENTON ST. PAULS GLASGOW POPLAR RIDGELAWN
Rr ee ey ea:
SInitnL oy eS ‘ee ees eee
etdpue Pe a
an f rd mat ie Wap eee SI My
pele a gil 1 \ | fall ea
oul litin DUTT Toten ot to ul,
DECKER RED LODGE LIVINGSTON DILLON BUTTE
8m [ltiee =< a FETen] (ee ea 7776
- a i ‘ : i sy “ae
Teeth oh sa nr
2+ + 4 - (ane Serena rae j-—_—_--_: 9
ee ee la ! ta atill =
Sao TE tT TE tl filin ;
TROY KALISPELL | RAYMOND GOLOBUTTE HAVRE
67 ; 6
5 Ho L po as
a : Hs
a ELUTinad FEUGEL ON DO 7 ! oy
a Bai] MAGGE | REP eee eer 2
Ali ti lt ali alli
MALT J TET UT is Ti

Fig. 7. Diagrams showing monthly distribution of precipitation
at twenty-five stations in Montana. From Summary of the Climat-
ological Data of the United States. Reproduced by permission of the
Weather Bureau.

CLIMATE 45

of 10.71 inches, the average of 11 years of observation. Missoula,
near the mouth of the Bitter Root Valley and on a direct line
some 30 miles from the higher Bitter Root summits, has an
annual record of less than 16 inches, the average of over 30 years
of observation. Similar comparisons may be made in various
other places. The heavy precipitation at Snowshoe in the Cab-
inet Range may be due to the position of the lake country in
northern Idaho, lying as it does directly to the west, and to the
fact that the southwestern winds have few opposing altitudes
to diminish their moisture before striking this range. To the
east lies the broad basin of the Flathead Vallev with about one-
fifth the total annual rainfall which oceurs at Snowshoe.

The more amply, watered western slopes of the Bitter Root,
Coeur d’Alene and Cabinet Ranges are heavily forested, and
support a type of vegetation more mesophytic than is to be found
in other parts of the region, with some few and limited excep-
tions. In this feature some portions of northern Idaho may be
included and in all such areas in western Montana and northern
Idaho there is a conspicuous element in the flora suggestive
of Pacific Coast humid conditions and undoubtedly derived from
that source. The areas of this character in western Montana
are few and are mostly confined to the moister valleys of the
Flathead drainage.

East of the Divide the annual precipitation is on the average
less. It varies from 10 to 22 inches, but for most places from
10 to 15. The lower plains have less and the amount increases
with the altitude. Red Lodge, Babb and Lewistown, situated
among or near mountains, have about 21, 22 and 20 inches re-
spectively. The mountainous areas, due to the greater rainfall,
have forests of considerable extent, but the plains are dévoid of
trees except along the streams or under other exceptional con-
ditions.

Relative humidity and the rate of evaporation in Montana
have not been established by a sufficient number of observations,
but some facts are available from the records of the Weather
Bureau at Helena, Havre, Kalispell and Yellowstone Park and
from observations bv the writer at Missoula, and these are sub-
mitted herewith.

Table 4 summarizes the data from the Weather Bureau’s

46 FOREST DISTRIBUTION

publications, which show that the mean maximum at Helena,
Yellowstone Park and Kalispell were between 60 and 87 per cent
and that the lowest relative humidity of which there is a record
is 30 per cent at Helena in August.

Table 2 gives the mean daily relative humidity, maximum
and minimum for a period of three years and table 3 the mean
daily variations during the same period. The record was made
by a standard hygrograph under standard conditions and cor-
rections made from time to time by aid of a sling psychrometer.
The instrument shelter, on the University campus, was placed
in an area of natural prairie vegetation as dry as usually ean
be found in the region. .A mountain rising to the east shut off
the early morning sun, but the station was fully exposed through-
out the rest of the day.

From the table of mean daily variations it will be seen that
these may range from 50% to 64%. The curve traced by the
recording pen shows, especially during the summer months. a
rythmiec daily rise and fall, the maximum about 6:00 a. m., the
minimum about +:00 to 6:00 p.m. The pen in rising traces a
more or less zigzag and irregular line until the maximum is
reached. At this point there is usually a sharp peak. for the
maximum is of short duration, then a steady downward sweep
during the day to the minimum late in the afternoon. The max-
imum of each day’s record usually shows strong throughout

Table 2. Mean daily relative humidity at Missoula. Maximum and
minimum.

Jan. Feb. Mech. Apr. May June July Aug. Sept. Oct. Nov. Dee.

Max ss 92 94 95 SS ST 96 SD SS
1915 Min 34 41 440 34 21 38S 438 50 60

Max S60 94 SD) SHE SB 8B SB 82d C82 8B) CTD OTB

1916 Min 6 66 45 34 32 31 2% 20 18 34 45 58
Max SO SO SO TT TT 73 66 67 T1 7 73 72
1917 Min 55 S51 42 31 25 25 9 413 IS 22 82 52

Max 72
1918 Min 50

Table 38. Mean daily variations in the relative humidity at Missoula.

Jan. Feb. Mch. Apr. May June July Aug. Sept. Oct. Nov. Dec.

; 54 al 54 61 67 49 5349 28
2 28 44 50 ad song 59 62 64 49 34 18
ay 29 ae 46 42S ml 5 52 5d 2k 20
>

CLIMATE 47

Table 4. Data from the Weather Bureau on the mean relative
humidity by months at three places in Montana and one in the Yellow-
stone National Park.

An-
Stations Hours Jan. Feb. Mar. Apr.May Jun. Jly. Aug. Sep.Oct.Nov.Dec.nual

Helena SA.M. 72 73 71 65 66 67 60 59 G64 66 68 71 67

8P.M. 66 63 56 42 42 41 31 30 39 48 56 65 48
Yellow- SA.M. 77 74 77 74 77 74 77 73 71 74 70 76 74
stonePk. SP.M. 71 64 65 48 51 46 36 38 40 55 58 59 53
Havre 80 81 77 62 63 63 57 56 62 6S 75 79 69
Kalispell 64.M. 86 86 81 78 82 82 78 77 S2 86 86 87 88

6P.M. 80 73 58 42 49 47 387 36 50 62 76 83 58

the year, even in relatively dry seasons, since the nights are
always cool. In the winter the rythmic quality of the curve is
much less marked, the maximum is comparatively low and the
peak flat, while the sharper angle in the day’s tracing now falls
at the minimum.

The situation is one of exceptional severity for vegetation.
Two months or more of drouth during the summer, mostly cloud-
less days, dav temperatures of 80 to 90 degrees, low relative hu-
midity and a highly porous soil, all tend to xerophytic conditions
in the vegetation. This station may be considered the most severe,
all points considered, in western Montana. During the season
of 1917 10 weeks in June, July and August were without a trace
of rain, and but .62 of an inch fell in three months. At the
close of this time, in the vicinity of the instruments, soil at the
depth of a foot was within 1.1% of actual air dry condition and
when heated for three weeks at a temperature of 120 degrees C.
gave off less than 2% of its original weight. The lower alti-
tudes in this valley are treeless except where sheltered from sun
and wind, a fact which is evidently related to the dryness of the
situation.

There is little but inferential evidence as to the rate of
evaporation at any point in Montana. One record in the Judith
Basin in 1909 showed evaporation amounting to 32.6 inches,
presumably for the vear. At Missoula during the season of 1917
the evaporation was 14 inches in 10 weeks (July, August and
September) from an exposed water surface of 4 square feet
protected by wire netting of one-third inch mesh. Sometimes
the evaporation was as much as 2 inches per week.

The Signal Service and the Geological Survey have con-

ae wouty. ‘ oiana

{

BEI

spbafesent teazaeetes ited? pisraassg ta

2 Get eo

tiesto

Fig. 8. Menn temperature diagrams for the year. A. Mammoth
Hot Springs, Yellowstone Park. altitude 6200 feet. B. Anaconda.
altitude, 5300 feet. CC, Philipsburg, altitude. 5 feet. D. Ovando,
altitude, 4101 feet. I, Missoula, altitude, 3212 feet. F, Troy, altitude.
1880 feet. The figures at the right represent the ratios of the growing
to non-growing seasons. The mean temperatures for the months are
en the curves midway between the vertical lines.

CLIMATE 49

ducted experiments showing that evaporation from a water sur-
face on the western plains of the United States may amount to
from 50 to 80 inches, and in some localities to even 100 inches
a year, while the rainfall (diminishing in inverse ratio) over
this area is from 30 to 12 inches and less. (25) In a series
of experiments to determine the relation of wind to evaporation
they arrived at the following conclusions: evaporation with the
wind at 5 miles an hour was 2.2 times greater than in a calm;
‘at 10 miles, 3.8; at 15 miles, 4.9; at 20 miles, 5.7; at 25 miles,
6.1, and at 30 miles, the wind would evaporate 6.3 times as much
water as a calm atmosphere of the same temperature and hu-
midity.’’ During these experiments the temperature of the air
was 84 degrees and the relative humidity 50 per cent.

In four years in Montana from 1908 to 1911 the maximum
wind velocity was 60 miles per hour. This was in March. Sum-
mer winds of 46 miles per hour were reported during the same
period. These figures are for the plains country. West of the
Continental Divide the winds are much more moderate. Winds
which rise to considerable velocity are of short duration. In
this section of the State the only places where winds seem to be
effective are on high and exposed ridges and peaks, and on the
more arid southern and western exposures at low altitudes.

Temperature records from many places in Montana, rep-
resenting observations of from 10 to 30 years, afford a reason-
able basis for judgment of the climatic conditions of the region
in relation to the vegetation. The lowest temperature thus far
recorded in Montana is -65 degrees, at Miles City. ana tlfe high-
est 117 degrees at Glendive. Glendive and Miles City are about
75 miles apart, and, while the figures just cited as to tempera-
tures represent the greatest extremes for these places and do
not at all indicate the usual conditions, they do indicate that
that section of the state is subject to seasonal extremes and
that the annual range of temperature may be considerable. As
a matter of fact it may range from 125 to 175 degrees. Other
sections of the State on the plains may likewise be subject to
extremes and the annual temperatures range from 120 to 150
degrees. The lowest mean annual temperature in Montana is
recorded from Bowen in the Big Hole, averaging 34.1 degrees,
and the highest recorded mean annual temperature is at Billings,

50 FOREST DISTRIBUTION

47.2 degrees. For the climatological sections established by the
Weather Bureau, the mean annual temperatures range as fol-
lows: :

Northeastern AMontana.............. 39.6 to 43.3 degrees
Southeastern Montana.............. 42.9 to 47.2 degrees
North Central Montana............ 36.5 to 45.8 degrees
Southwestern Montana.............. 34.1 to 45.5 degrees
Western Montana..................--. 38.9 to 45.8 degrees

Northeastern Montana is characterized by lower tempera-
tures usually and by higher winds and more sudden changes of
temperature than other parts of the state. There is a sudden
transition from winter to summer in the middle of June. from
snows and freezing weather to the long hot days of summer;
autumn is dry, and mild weather often extends to December.
The normal temperature for April is about 40 degrees, which
marks the beginning of the spring growth of the prairie flora.
In the southeastern part of the State there is a wider range
of temperature, both daily and annual. During the summer
the diurnal variations may be as much as 40 degrees or more.
Snow falls from October to March. The north central portion
of the State is colder and drier than the northeastern part. The
winter minimum sometimes falls to 45 degrees below zero, and
the summer maximum of 100 degrees is experienced in many
localities. In scuthwestern Montana the several high ranges of
mountains collect abundant snows. High altitudes, low humid-
ity and the absence of high winds are features of this section.
The tefnperature records are more uniform than might be ex-
pected, owing probably to the more or less sheltered locations
of the various stations of observation. Western Montana is a
region of widely differing altitudes and topographic conditions.
and in some of the mountain valleys frosts and even snows may
occur in all months of the vear. Jn some parts the snowfall is
exceedingly heavy.

Two tables are provided viving the significant facts of at-
mospheric temperatures. Table 5 gives the average mean tem-
peratures during the months of the growing season and the
average annual means at 29 different stations in the State. The
last six are within the timbered section of Montana and in
proximity to important forests. The others are mostly in the

CLIMATE bl

prairie country. Table 6 shows the highest and lowest tem-
peratures on record for 35 stations in Montana during the six

Table 5. Average mean temperatures during the months of the
growing season and average annual means.

Yrs. An. | Alti-

Station Obs. = | Mav | June | Julv | Aue leant lees feet
Glendive ow ... | 20 | 46.0 | 56.3 | 65.1 | 72.1 | 71.0 | 59.4 | 43.3 | 2069
Poplar ........ .| 24 | 42.9 | 54.3 | 63.8 | 69.7 | 67.3 | 57.1 | 89.8 | 2020
Glasgow | 14 | 44.3 | 56.2 | 62.7 | 69.9 | 67.8 | 56.0 | 40.2 | 2092
St. Pauls 9 | 42.7 | 50.4 | 59.2 | 66.5 | 67.0 | 55.8 | 43.1 | 4150
Chinook 10 | 43.0 | 54.5 | 62.6 | 69.9 | 67.4 | 56.8 | 41.9 | 2502
Havre .... 29 | 42.7 | 54.1 | 62.4 | 68.1 | 66.9 | 57.6 | 41.9 | 2505
Cut Bank... 11 | 38.3 | 48.8 | 54.8 | 60.6 | 60.0 | 50.4 | 38.6 | 3700
Fort Benton... 30 | 44.6 | 55.1 | 62.7 | 69.6 | 67.8 | 57.2 | 44.1 | 2630
Great Falls... ---| 18 f 45.5 l 53.6 | 60.9 | 67.8 | 66.7 | 57.1 | 45.8 | 3350
Fort Shaw..... 2 EL | 40.1 | 54.1 | 62.6 | 68.3 | 64.7 | 55.6 | 44.0 | 3500
Lewistown 12 ' 42.1 150.4 | 57.5 | 64.2 | 63.0 | 53.7 | 42.6 | 4010
Wibaux ...... 9 | 46.3 | 56.2 | 61.7 | 69.7 | 66.8 | 56.8 | 42.9 | 2674
Miles City.. 31 | 47.0 | 56.5 | 66.3 | 72.6 | 71.5 | 59.8 | 44.6 | 2371
Ekalaka ..... 9 | 43.5 | 53.0 | 61.9 | 68.9 | 67.9 | 59.8 | 48.7 |...
Crow Agency............1 30 | 46.6 | 55.6 70.9 | 69.5 | 58.6 | 45.2 | 3041
Billings | 16 | 45.3 | 55.7 71.7 | 70.4 | 60.5 | 47.2 | 3115
Fort Logan... | 24; 39.1] 48.1 63.1 | 61.6 | 51.1 | 39.3 | 6000
Harlowton | 14 | 41.4 | 51.0 65.2 | 64.0 | 48.1 | 41.0 | 4165
Helena. ........ -| 28 440/518 66.9 | 66.2 | 56.2 | 43.6 | 4110
Bozeman 2h | 40.5 | 50.0 65.8 | 64.3 | 53.3 | 43.5 | 4700
Red Lodge.. 9 | 39.6 | 46.0 61.2 | 60.7 | 52.4 | 40.8 | 5548
Virginia City............| 20 | 40.0 | 47.6 64.5 | 64.0 | 53.5 | 41.2 | 5880
Yellowstone Park....| 22 | 374]461 64.7 | 61.0 | 52.4 | 39.5 | 6200
Columbia Falls........ 14 | 42.9 | 51.0 63.9 | 62.4 | 53.3 | 42.6 | 3100
Kalispell 11 | 42.5 |} 51.0 64.3 | 62.9 | 53.9 | 42.4 | 2965
Troy -....... 15 | 46.1 | 53.6 64.2 | 63.0 | 55.0 | 45.1 | 1880
Plains 11 | 44.6] 51.7 65.8 | 64.1 | 56.0 | 44.7 | 2475
Missoula 30 | 44.8 | 53.7 67.1 | 62.9 | 55.8 | 43.8 | 3212
Deer Lodge .............. 14 | 40.6 | 49,2 62.9 | 60.3 | 51.7 | 41.0 | 4768

months of the growing season. Again the figures for western
Montana are the most significant as representing a more heavily
forested region. But in other parts of the State represented
by these figures there are forests locally important, or at least
forest species more or less common. While it may be seen that
in all sections the maximum may rise to 100 degrees or more, the
minimum for each month falls more often below the freezing
point than above it.

The vital phenomena of plants are mostly confined to tem-
peratures above freezing. While it can be shown that certain
functions are performed at a diminished rate below 32 degrees
F., it is also evident that all functions inerease in vigor in geo-
metrical ratio from this point up to the optimum. The length

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CLIMATE

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(‘ponutjueg) 9 eTqRy

54 FOREST DISTRIBUTION

of time, therefore, between the ccol weather of spring and au-
tumn, which marks annually the time of awakening and of re-
tarding of plant life, is important as determining to a large
extent the limits of the distribution of species when other things
are equal, but hotter summers in certain areas may furnish the
required total of heat for the support of species which would
not be able to endure in another region having a growing period
of equal length but of lower temperature.

The length of the frostless period in the year must deter-
mine, of course, the northern limit of distribution of certain
species of native as well as of crop plants. The sum total of
heat required for the maturing of the plant and the production
of seeds must in most cases be the minimum even among those
hardy species which resist frost, and furnish the northern limit
of their distribution. Jn this region the frostless period of the
year varies from 40 days to 4 months or more, depending on
location and altitude. Table 7 presents frost data for a number

0 ND. i r ya] = ALL

TEETH fisssseedd ceil i fpejieend estat SREY

i

Vig. 9. Mean temperature diagrams for the year. A, at Billings,
altitude. 2371 feet. B, at Havre, 200 miles north of Billings. altitude,
2505 feet. The figures at the right represent the ratios of the growing
to the non-growing seasons. The mean temperatures for the months
are indicated ly “the cross-marks on the curves, midway between
the vertical lines. :

CLIMATE 55

Table 7. Average dates of last killing frost in spring and first in
autumn.

Station Years of Last fr First frost

a in nee in autumn

GIASSOW:. sent.ccveiiesicekcne attests 14 May 22 Sept. 12
Chinook 10 “18 “il
Glendive .... 16 “12 22
Poplar 16 “ 16 “44
St. Paul 10 “29 “16
PAVEN, osecericrecicanestnasisnenanscaninnbusdtesueankon 10 June 25 Aug. 24
Chouteau : 11 May 30 Sept. 6
Fort Benton ..00.0000000.0 eee 9 “16 «30
Lewistown ou... oo 12 June 5 a 3
Great Falls 18 May 7 “16
Cut Bank .... ve June 14 Aug. 29
Billings ........ 10 May 7 Sept. 16
Crow Agency . a 27 foe alley “26
Miles City ..... 3 18 i qT “24
Red Lodge .....222222.---csecccecseeeece 8 June 13 ui 2
Bozeman 8 May 28 - 7
Butte 14 June 5 bam
0 2X5) id a B07'1s | 0 nr 12 as 16 Aug. 30
Helena _ 0.2.22. 3 May 7 Sept. 28
Dillon 9 June 9 uf 1
Anaconda ....... (SEPT ONEEODA 7 8 He 1. ne 4
Columbia Falls 16 “ 9 Aug. 22
Kalispell 12 May 13 Sept. 30
Missoula oo... eeecee eee 10 e138 19
OVANGO: siscectesescszesetceeeessecss 10 July 4 Aug. 12
{Troy beeps ahd 15 June 1 Sept. 7

of stations within the State. In these as in most temperature
records, other elements are to be considered besides latitude and
altitude. Some stations much higher than others have a longer
frostless season and some with a difference of 100 miles or over
in latitude have a difference of 30-50 davs in the frostless period
in favor of the more northerly stations without compensating
difference in altitude. The proximity of mountain ranges, the
width and direction of valleys, the exposure cf the slope, and
the ‘direction and velocity of winds, all have their influence on
the temperature at any time of the year. Owing to the charac-
ter of the topography and the extent of the area involved, the
figures on temperature can have only the most general sig-
nificance. Figure 11 givesethe mean annual isotherms of 1911,
one of the colder years, and indicates the complexity of the
temperature problem as far as distribution of species is con-
cerned. When local areas are under consideration their tem-
peratures must be a subject of local investigation.

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CLIMATE 57

_ The ratio of the growing to the non-growing portion of
the year is graphically shown in Fig. 8, which applies to sev-
eral stations at altitudes varying from 1880 to 6200 feet. For
each station a base line is drawn representing 40 degrees F., the
approximate minimum of temperature as related to seasonal
vegetative activity. Above and below parallel lines are drawn
at intervals of ten degrees. Each diagram thus represents a
vertical range of temperature of from 40 to nearly 60 degrees.
The mean temperature for each month is fixed by points above
and below the base. A line drawn through these points forms
a seasonal curve for the temperature of the station. This curve
falls below the base during the winter months. Descending
sharply it reaches the minimum sometime in January, then it
ascends, crossing the line usually in April, and reaches the
maximum in July, whence it sinks again to the base line in
October or November. Between the curve thus described and
the base are included two areas, one above and the other below,
which together represent respectively the positive and the neg-
ative temperature conditions of the year. They represent also,
from the standpoint of vegetation the relative values of .the
months indicated.

The vertical lines separate the months. The mean tem-
perature for each month is fixed at the middle or half wav he-
tween the verticals. On some of the curves these points are
marked and indicated by figures expressing the mean tempera-
ture of the months. (Figs. 8, 9.) The relative lengths of the
growing and the non-growing seasons can readily be compared.
In some cases the two periods are seen to be about equal, six
months of each. Jn others, the ratio is 5 to 7 in favor of the
growing season. The vertical distances determine the areas which
are proportional to the values of the periods. In comparison the
growing seasons are seen to have relative values of 7, 8, 9, 11, 12,
14, ete., in different parts of Montana, as reckoned by the total
areas of the squares. While the curve is a generalized one and
the actual temperature variations would show sharp oscillations
above and below, the areas included may, in the long run, be
taken as fairly representative of the seasonal values.

Livingston (35) has suggested a method of reckoning tem-
peratures in relation to field vegetation according to exponential

58 FOREST DISTRIBUTION

law. By this method it is conceived that with every increase of
18 degrees F. from 40 degrees to the optimum there is a doubling
of the rate of growth and of activity of other physiological
processes. MacDougal (37) has applied this principle in de-
vising a method of integrating temperatures, whereby the area
below the line of a thermograph record and above the line of 40
degrees may be made to represent hour-degrees in relation to
plant growth. when applied to the rate of growth within fixed
limits of temperature. In the diagrams (Figures 8, 9) herein
presented for Montana the duration and intensity of the growing
temperatures is shown. The spaces between the heaviest vertical
lines represent months. The same distance between horizontal
lines represents 10 degrees of temperature. The tallest of these
vertical lines represents therefore 72 degrees as the mean for
the month of July at Billings. The lowest here given is 61 de-
grees which is the mean for the same menth at Ovando. In the
former case there are as a rule 32 degrees of temperature favor-
able for growth. in the latter 21. The others may be seen to vary
from 22 to 28 degrees. The duration, however, varies. as indi-
cated by the character of the curve which in some cases ascends
directly to the maximum and falls off again quickly, in others
the higher temperatures are sustained longer and the curve
accordingly has a flat or broadly rounded top. These features
figure largely in the sum total of the productive temperatures
of the locality, and stand in relation also to the variety of crop
plants usually grown under irrigation in the several places.
The curves of total heat required for all species must nat-
urally fall within the limits of the curve thus determined for
each locality. when established upon the same basis. It is also
evident that the curve for the species must more nearly approxi-
mate the curve for the locality the higher the latitude or altitude.
If the exponential interpretation of temperatures in relation to
plant life is applied, it means that in one month of higher tem-
perature as much substance of the plant body may be formed as
in a longer period at lower temperature. It must be borne in
mind, however, that the brevity of the far northern summer
seasons is accompanied by the shortening of the vegetative period
and the production of seed in much less time than is required
by the same species in warmer climates. Wheats which require

CLIMATE 59

129 days to mature in temperate latitudes, if taken farther north
gradually, after some years, reduce the period of life from sow-
ing to ripening to ninety days or less (1). The rapid develop-
ment of northern vegetation during the short summers is well
known. The same is true of alpine floras. Schimper’s refer-
ence (56) to the effects upon the rate of growth of trees and
the period required for their maturity may be cited in this
connection, and many other facts of similar import.

The sunshine data for this region are far from being ade-
quate for our purpose but some facts can be given indicative of
the conditions. They show an abundance of clear days for the

Table 8. The average sunshine record for four years (1908-1911)
in different parts of Montana.

Station Clear | Gisudy | elses
Miles City esas ' 159 125 81
TANG GS (goo eee nents atta ddne evden Sancti 159 128 104
Helena eee 120 122 123
Great Falls... eee 160 149 56
Dillon 156 110 96
Butte 2... sone 151 62 145
PU AUIS: ie Avsern poem ceacostuc sap emsevecessantoesssecssteussscds 205 7 152
Saltese x 227 11 127
Kalispell 110 117 138

limited period to which they apply, though unfortunately the
distribution of the clear days by seasons can not be indicated,
nor the intensity of the light. In the state the average number
of clear days in the year varies from 160 to 178, the number
of those partly cloudy from 95 to 108, and those recorded as
cloudy from 83 to 101. At Poplar in northeastern Montana, the
number of clear days from vear to year varies from 260 to 280,
those partly clear from 33 to 58, while the cloudy days at the
most cover less than two months, varying from 45 to 59 days.
These figures as well as those in the accompanying table are to
be taken only as a general indication, allowing for errors of
observation and the lack of related data. On the Western Slope
the clear days predominate in the summer and autumn, though
many are scattered through the other seasons. In eastern and
central Montana, the rains coming freely in the growing season
probably indicates a good many days during the summer at least
partially clouded.

NVIN Jay VA, OJ JO UOTSssttod Ly

TIGL ‘WULUOW UL somNzRavdtuo) uTont 1oJ suLoY JOS]

OV

TL SLT

60

CLIMATE 61

In connection with this reference to light it should be re-
membered that on the parallels of latitude extending through
this region the period of daily illumination during the summer
is relatively great. On the longest days of the year, actual
darkness hardly amounts to more than 6 hours of the 24. That
the amount of carbon assimilated stands in direct ratio to the
duration of daylight during the growing season is, of course,
obvious.

While the fundamental importance of light in the economy
of plant life is widely known, not so general is the knowledge
of the relation of light to other climatic factors in the growth
of plants, or of the peculiarities, with reference to light, of the
particular forest species. In discussing the forest conditions
of a region it is pertinent to point out that the amount of light
required by a tree is increased with the lowering of the tem-
perature. In warmer latitudes, therefore, a tree may endure a
ertain amount of shade, while in more northern regions it re-
quires full exposure to sunlight: A difference of this sort may
be seen in the western yellow pine, which in Montana and else-
where in the northern Rocky Mountains is very intolerant of
shade; in Arizona, however, this tree is much less sensitive, and,
like many other plants of that region, actually prospers better
for a time under a moderate shade. This is, however, not wholly
a matter of temperature difference, since the sunlight is more
intense in latitudes toward the equator, and, as all plants are
attuned to a certain range of light intensity, any excess of light
is avoided wherever possible. Whether the difference of be-
havior is due to a difference of light intensity or of temperature,
or both, it finds expression in the appearance of the forest,
which must be mcre open in the cooler latitudes, in order to
provide sufficient illumination. This opening of the stand may
give an opportunity for the entrance of other species less sensi-
tive to shade, giving rise to a forest of mixed species, and even
resulting in the end, perhaps, in the total elimination of the
intolerant ones.

CHAPTER III.

SOURCES OF THE VEGETATION: MIGRATIONS.

gion and plains have been glaciated and the subsequent

plant covering derived from outside areas in later times
(24). The sources from which these migrations have ensued were
several, including chiefly Atlantic and Pacific elements as indi-
cated by the existing species. A southern element likewise enters
to some extent, but is important only here and there locally, so
far as the woody species are concerned.

Pee a pi all of the northern Rocky Mountain re-

That any relation exists between the species at present
growing in this region and those antedating the glacial period
is neither impossible nor improbable. but is difficult of proof.
Of the many (50) genera of woody angiosperms listed below,
mostly from the strata of the Tertiary of this immediate regicn,
nearly all are represented by one or more species within the
temperate latitudes of North America, and the majority of the
existing genera of like sort in Montana are represented in the
fossils of that period. Of the Tertiary gvmnosperms three out
of four genera are likewise now native to temperate North Amer-
ica, while the earlier Cretaceous genera representative of this
group are mostly extinct, though some are allied to existing fam-
ilies. The rich flora of the Tertiary. abounding in broad-leaved,
deciduous forests, must have developed under conditions far dif-
ferent from any that have existed since, both as to temperature
and moisture, and doubtless far more favorable for the origin
of new forms.

The following lists from the works of Newberry (44). Les-
quereux (33), Knowlton (28) and Ward (69) are doubtless in-
complete but will serve to indicate something of the past history
of the flora of this region. The genera at present existing
here are marked by an asterisk (*).

GYMNOSPERMS

Araucaria Glossozamites
Sequoia Cycadaspermum

62

Taxodium
*Thuja
Glyptostrobus
* Pinus
Ginkgo
Abtetites
Cycadella
Cycadeoidea
Nilsonia
NVageiopsis
Zamites

Sabal
*Populus

* Salix
*Corylus

* Alnus
Alnites

* Betula
Quercus
Quercophyllum
*Ulmus
Ulmophyllum
Celtis
Planera
Carya
Juglans
Ficus
Ficophyllum
Protoficus
Liriodendron
Magnolia
Laurus
Sasafras
Tetranthera
TIamamelites
Liquidambar

SOURCES OF THE VEGETATION

Williamsonia
Araucarioxylon
Araucarites
Leptostrobus
Arthrotaxopsis
Geinttzia
Sphenolepidium
Baieropsis
Cyekanowskhia
Cephalotarus

ANGIOSPERMS

Platanus
*Amelanchier
* Prunus
*Rhus
Euonymus
Celastrophyllom
*Acer
*Negundo
Sapindus
Sapindopsis
*Rhamnus
Rhamnites
*Vitis

Cissites

Tilia

*Aralia
*Cornus
Nyssa

* Andromeda
Sapotacites
Diospyros
*Prarinus
Cinchonidium
Viburnites
*Viburnum

63

It has long been known that in times next preceding the

glacial period, in the latest Tertiary, from Spitzbergen and

64 FOREST DISTRIBUTION

Iceland to Greenland and Kamtchatka a mild temperate climate
prevailed and forests like these from New England to Virginia
and California clothed the land. In the words of Gray (20):
‘*We appear to be within the limits of scientific inference when
we announce that our existing temperate trees came from the
north.’’ All species were probably crowded southward by the
ice and doubtless found at least a narrow zone suited for their
occupation during the period of glaciation. Upon the retire-
ment of the ice some of these species or their descendants must
have reoceupied portions of the land. During all of this period
selective influences were undoubtedly sifting out the species
which were the distant forebears of our present flora. Climatic,
topographic, and edaphic conditions determined the final types
of vegetation (prairie, forest, ete.) over large areas of the land
reoccupied. Since none of the existing species of this region.
as far as we know, have appeared in the Tertiary deposits it
seems probable that they have entered or evolved since that
period.

The present alpine flora of the northern Rockies shows
little evidence of its connection with the Tertiary flora above
mentioned. Few species are common to the old and new world,
and no closely related forms are here known in the fossil state.
Rydberg (55) mentions one woody plant, a dwarf willow (Sa/ir
reticulata) as common to the arctic regions of both continents
and to the higher altitudes of the Alps and the Rockies.

Beyond a few other shrubby willows and heaths, with aftin-
ities more or less evident with European species. immediate con-
nection between the woody alpine flora of this region and that
of the old world can hardly be admitted. As to some of the sub-
alpine specics (admitting the difference of opinion as to the
identity of the old and new world forms of Juniperus Nabina
and communis a few may be cited as having general circum-
polar distribution in the pre-glacial period. Probably a consid-
erable number of plants may be regarded as indigenous to the
northern Rocky Mountain region since the glacial period. (Cer-
tain species considered by some to be transcontinental are by
others divided into two or more species with lesser ranges con-
tiguons or overlapping; without considering the merits of these

SOURCES OF THE VEGETATION 65

distinctions it suggests the possible origin of new species from
the invading stock.

as to whether a species is immigrant or indigencus is often
difficult or impossible to determine. In some cases it may be
apparent from geographical evidence that a species has entered
from a contiguous or distant area, but in others it may appear
to have originated within the area, and if so the question of
interest is the identity of the parent race or species, a fact which
may be suggested by a comparison with associated or neighboring
species, but which, if at all susceptible of proof, can be deter-
mined only by detailed structural comparisons or by experiment-
al means. In this paper such conclusions as may reasonably be
drawn from geographic evidence or other external facts will be
presented, but with appreciation of the uncertainties involved.

With reference to the geographic evidence it would seem
that at least three considerations may be recognized. (1) The
edge or limits of the range of any species may fall within the
region under examination and if so its’ source may logically be
referred to the center from which it seems originally to have
emerged. Southward extensions along the Rocky Mountains of
boreal transcontinental species, or western margins of the ranges
of conspicuous eastern or middle states species lying along the
eastern base of the Rocky Mountains or eastern margins of
ranges in the case of typically Pacific Coast forms would be
cases in point. (2) The degree of development of a species as
representing the supposed center of its distribution. The Doug-
las spruce falls under this category. This species occurs in
extraordinary vigor and abundance along the Pacific Coast west
of the Cascades, whence it seems to have emerged eastward until
it has found its effective barrier in the plains between the Rocky
Mountains and the Mississippi River. While this is not usually
a safe argument in view of the well known facts of the luxuri-
ance of many introduced forms in various parts of the world,
it seems more logical in the case of naturally developed species
in their proper ranges to view them as indigenous to the regions
of their greatest and most varied development. (3) The geo-
graphic center in which the genus or family are conspicuous or
characteristic may be regarded as the source from which the
outlying species have emerged. The cacti and yuccas of the

66 FOREST DISTRIBUTION

Southwest and the Mexican Plateau may be regarded as ex-
amples. The representatives of these groups in the Montana
flora can be regarded only as having a southern origin. With
such points in mind a grouping of species is attempted accord-
ing to the sources from which they seem to have migrated into
the northern Rocky Mountains.

The following species mostly have a northern transcontinent-
al range and appear to have moved southward along the Rocky
Mountains into Montana and in some cases far beyond:

*Juniperus communis Dasiphora fruticosa
= se Sadina ‘Elacagnus argentea
Populus tremuloides Lepargyraea canadensis
- balsamifera Rhus glabra
Salix cordata Rhamnus alnifolia
6 chlorophylla Cornus stolonifera
fe fluviatilis ws canadensis
“ Bebbiana Andromeda polifolia
“Barclay? *Arctostaphylos Ura-ursi
‘* pscudomyrsinites Chiogenes hispidula
Betula papyrifera *Vaccinium uliginosum
*Alnus incana a caespitosum
Ribes lacustre ae ovalifolium
“<< hudsonianum Sambucus raccmosa
Rubus strigosus Symphoricarpos pauciflorus
Rosa acicularis Lonicera involucrata

There is, of course, no barrier to the southward movement
of species along this highway through the region here under con-
sideration. Five of the above species (marked *) occur around
the world in the northern hemisphere. Most of the others are
middle or northern Atlantic Coast or eastern species which
apparently have extended their ranges far to the northwest,
passing north of the Great Plains to the Rocky Mountains and
thence southward; some are extensively distributed from the
coast of New England and Labrador to Alaska.

The following have entered Montana and the Rocky Moun-
tains from the east:

Populus angustifolia Prunus americana
ee Sargentii Acer Negundo
Salix pedicellaris Sambucus canadensis

SOURCES OF THE VEGETATION 67

Salix candida Symphoricarpos orbiculatus

“* amygdaloides fracinus lanceolata

Ribes americanum

Bessey (3) concluded from a study of the trees of Ne-
braska that most of the species had entered that state from the
southeast, influenced largely by the direction of the prevailing
winds in the spring and early summer. The cottonwoods, two
willows (S. amygdaloides and fluviatilis) and the boxelder were
included in his list. Populus Sargentti, which by some authors
is considered as at best only a variety of P. deltoides, is contin-
uously distributed along all the bottom-lands of the Missouri and
the Yellowstone and their tributaries, and evidently has followed
up these streams from the lower regions to the southeast. The
favorable conditions which woody species usually find on river
bottoms and the continuity of such conditions along the many
drainage channels across the plains should have provided a
larger representation of such species in the Montana flora. The
low relative humidity of the plains and the desicvating winds
that sweep across them serve apparently as effective preventives
of any departure of woody plants from the lower and more
favorable levels. The tops of the cottonwoods along the upper
tributaries (16) are distorted and repressed as they reach above
the protection of the bordering benches. The matter of at-
mospheric humidity is as important for certain trees as the mat-
ter of soil moisture, and specific requirements must be met in
one condition as well as another. Whether this is the determining
factor or not in this case is impossible to say without further
study, but for various reasons it seems probable. Prunus Ameri-
cana is reported only from the eastern part of the state, and on
uncertain authority as far west as the Bearpaws, south of Havre.
The ash (Fraxinus lanceolata) probably occurs sparingly in the
eastern end of Montana.

As the western or Pacific slope of the divide is the more
favorable for forest growth and is tenanted by a greater variety
of species, it naturally follows that the western element is the
most conspicuous in the forest flora of the Rocky Mountains.
On this point several considerations should be noted. Aside
from the more favorable climatic conditions enjoyed by this
region, its more ample precipitation, its higher relative humidity

68 FOREST DISTRIBUTION

aud more moderate winds. there is also an historical reason in
the events subsequent to the glacial period. The more varied top-
ography of the Pacific Slope from the mountains to the coast
furnished conditions of greater diversity and thus more favorable
for varied vegetation. Bodies of water formerly occupied areas
now sparsely timbered or prairies and these must, at least during
the time of their subsidence, have offered conditions more favor-
able for the existence and the movements of arborescent species.
The distance to be covered, no less than the character of the
intervening country, has doubtless been a factor, for the dis-
tance from the Cascades to the Rockies is less than half of that
across the plains eastward from the summit. and the time neces-
sary for movements would have been correspondingly less even if
topographic conditions had been equal. Furthermore the direc-
tion of the prevailing winds favor the eastward migrations. It
is significant also that of the 63 species enumerated below as
having entered from the west 27 have seeds winged or otherwise
more or less fitted for wind dispersal, 21 bear succulent
fruits with small seeds. such as may be carried readily by birds.
The others have small or minute seeds. There are no heavy seed-
ed species. unless the whitebark pine is excepted. and the seeds
of this tree are eagerly sought by squirrels. birds and other forest
animals. There are, of course, few heavy seeded species on the
coast in neighboring latitudes. According to all reports no oaks
have yet reached Montana either from the west or the east, al-
though they occur in Wyoming.

Following is a list of the species which have entered the
Rocky Mountains from the west or northwest:

*Pinus contorta =Betula occidentalis
=Pinus monticola * «6 fontinalis
“ albicaulis ‘< alaskana
Larix occidentalis “glandulosa
#Larixe Lyallii *Alnus tenuifolia
*Pseudotsuga tarifolia *Odostemon Aquifoalium
=Abies grandis *Ribes ccreum
#Tsuga heterophylla *Philadclphus Lewisti
‘ Mertensiana =Spiraea Douglasii
*Picea Engelmannii =Holodiscus ariaefolius

=Thuja plicata *Rubus parviflorus

SOURCES OF THE VEGETATION 69

#Taxus brevifolia Rosa nutkana
#Populus trichocarpa ‘pyrifera
*Salic fluviatilis + ‘* gymnocarpa

<< melanopsis *Amelanchier alnifolia

“ exigua *Crataegus Douglasit

“ argophylla Sorbus scopulina

‘ Mackenziana *Prunus demissa

‘ vestita Prunus emarginata

«« sitchensis *Pachystima Myrsinites

“* Geyeriana *Rhus Rydbergii

‘* Scouleriana Ceanothus velutinus

“bella ee sanguineus

«« glaucops Kalmia microphylla
#Rhamnus Purshiana Cassiope Mertensiana
#Echinopanar horridum #Gaultheria humifusa
#Cornus Nuttalli Vaccinium occidentale
Ledum glandulosum me membranaceum
# Rhododendron albiflorum ee oreophilum
Phyllodoce empetriformis ee scoparium

os glandulifera Symphoricarpos vaccinioides

*Menztesia ferruginca

The species listed above vary widely both as to their abun-
dance and as to the extent of their areal distribution. Some
(marked *) are found generally distributed throughout the re-
gion under discussion in their appropriate altitudes. Those
marked (*) are either rare or uncommon, confined to the lo-
ealities or altitudes suited to their peculiar demands, which in

* According to Bebb \Bot. Gaz, 102-108, Ap. 1891), the group
Longifoliae, to which belong Salix fluviatilis, S. melanopsis, S. exigua, and
S. argophylla, “is distinctly American, clearly defined on every side,
shading off into no other by variation, hybridizing with none. It is
not connected with the Old World forms by any synthetic type of the
present or of any preceding period, but apparently was derived from the
Mexican Plateau at the close of the Tertiary. In keeping. with this
view if finds its fullest development and greatest variation in form and
structure on the Pacific Slope. Eastward it declines in vigor and
variability until on the Atlantic Coast it is of rare occurrence from
New Brunswick to the Potomac.” Taking this view into account, there
is some doubt as to whether the species named should be regarded as
coming from the south or west. Considering, however, that'the group
is most fully represented today in numbers and forms in western
Oregon and Washington, it seems most probable that they have come
into our region from that source and are so listed.

70 FOREST DISTRIBUTION

all but a few cases means mesophvtic conditions, or they are
found only along the western boundary of the State. The other
species are more or less abundant locally but have no very wide
range, or they may be sparingly and uniformly scattered over
the area.

The number of Pacific Northwest species increases with the
distance westward from the Divide. As nearly the whole of
Montana west of the Range is drained by the Clark’s Fork of the
Columbia and its several main affluents. the Flathead, the Bitter
Root, the Blackfoot. and the Hellgate (the upper continuation
of the Clark’s Fork and now known by the same name). the re-
gion falls naturally into four divisions corresponding to these
main drainage basins. Of the two most westerly. the Flathead
lying to the north and the Bitter Root to the south, the Flathead
presents the most humid conditions and contains the largest
number of western species. The Bitter Root, on the other hand,
is the least humid and presents fewer mesophytic situations. It
lies in the rain shadow of the Bitter Root Mountains. Only in
the passes and the deeper gerges of this range are mesophytie
conditions found and in these some of the moisture loving species
appear, but most of them are excluded by the high barrier to
the west.

In discussing the topography it was pointed out that a high
mountain barrier extends along the western border of Montana,
except where the Coeur d'Alene Range interrupts the higher ele-
vations with a broad plateau-like formation, dissected into nu-
merous canyons and relatively low summits. Just north cf this
lies the channel of the Clark’s Fork bearing all the waters of
the Continental Divide over a distance of 300 miles of its western
slope. North of this the high ranges again arise, extending far
to the north. The Coeur d'Alene Range is occupied >y nearly
all of the species above ascribed to western origin (30) possibly
excepting Lyall’s larch and others ordinarily found only on the
highest elevations. It is evident that this range is the main
highway for the Pacific species into western Montana. The con-
figuration of the land, its low altitude. its proximity to the lake
region of northern Idaho. all serve to make this range at once a
convenient harbor and highway for the more tender mesophytie
species of the Humid Transition. These species as-cnd the west-

SOURCES OF THE VEGETATION 71

ern slopes of the Bitter Roots but usually fail to get over, and
again to the north the region is inhospitable on account of its
altitude in some places and in others on account of greater aridity.

Some of the species apparently have come into Montana
from the northwest along the Rocky Mountains. Some have a
distribution from Alaska to Oregon and in the Rockies to Mon-
tana or Wyoming. Others seem to have made their way across
from the coast by way of the Okanogan country and the Selkirks.
Shaw (57) found in the Selkirk Range most of the species listed
above. It is not improbable, as already stated, that formerly
conditions were much more favorable for a direct eastward mi-
gration across the inland basin which now would be impossible.

Certain species in this eastward migration have moved on-
ward across the main range of the Rockies. The Continental
Divide in its general course and altitude has been discussed
under topography. It constitutes the main barrier between the
eastern and western floras. Many species, however, have crossed
it both from the east and the west. In many places, up to
7000 feet or more the crest is wooded, sometimes with dense
forests, more often with scattered pines and junipers, and here
and there a bleak, wind-swept, rocky ridge, tenanted only by
low, caespitose perennials of xerophytic habit and structure.
While the ridge is not uniformly high, the greater part of its
length in Montana is 7000 feet or more in elevation, dropping
in some of the passes to less than 6000 feet. These gaps, how-
ever, are not wide and climatically are quite different from the
Coeur d’Alenes farther west. They share in large measure the
rigors of the winters which are long and severe in the neighboring
heights. At these elevations the summers are short and the
growing season two to three months, with great diurnal range of
temperature and with nights frequently marked by heavy frosts.
The snow usually disappears during the summer except in patches
on sheltered north slopes, or in the glaciers which occupy some
of the high depressions in the northern ranges.

Plants are abundant and over most of the high slopes vig-
orous, during the short season allotted to them, but on the whole
the region of the high divide is inimical to many species and in
general an effective barrier to eastward and westward move-
ments. It is interesting, however to note how many of those

72 FOREST DISTRIBUTION

plants among the herbaceous perennials which flourish in such
numbers in the high mountain parks are conspicuous elements
in the spring floras of lower altitudes, and in some species almost
to sea-level. Still other factors besides those of altitude and
length of the growing season figure in determining the range
of these plants and such are found in their moisture requirements
and the trying conditions which at all times beset the crest of the
main Divide and all exposed places in its immediate vicinity.

The continental crest in itself is hardly a barrier of suf-
ficient height to prevent transmigrations. Flanked, however, as
it is by massive ridges and high parallel ranges. its effect is re-
inforved by repetition. The topography offers a succession of
parallel ridges rising on both sides to the main Divide. These
eut by valleys would have even less effect individually as bar-
riers, but they serve to increase the mass elevation and econtrib-
ute to the general effect upon the climate over a region 250 to
300 miles from east to west. and north and south for some dis-
tance beyond the limits of the region here under discussion. The
proximity of surrounding peaks has of course a marked influ-
ence on temperature, humidity and precipitation and conse-
quently upon the flora of localities, themselves not of great ele-
vation.

The following species of eastern origin have reached the west-

ern slope:
Populus tremuloides Salix cordata
Nalir candida Ribes americanum
“ amygdaloidvs Symphoricarpos orbiculatus

It is probable that some of the species have traversed the
Rocky Mountain barrier in many places. In the case of trans-
continental species in the north their southward extension has
doubtless followed along both slopes of the Divide and wherever
else suitable conditions offered.

These of western or southwestern origin which have reached
the eastern slope or the plains are listed below. Some of these
have extended their ranges much further than others.

Pinus contorta Ceanothus velutinus
Fseudotsuga tarifolia Ledum glandulosum
Picea Engelmannii Phyllodoce empetriformis

SOURCES OF THE VEGETATION 73

Salix Mackenziana Phyllodoce glandulifera

“ erigua Menziesia ferruginea

** Scouleriana Kalmia polifolia

“* glaucops Cassiope Mertensiana
Betula fontinalis Gauitheria humifusa
Odostemon Aquifolium Vaccinium membranaceunr

be

Rubus parviflorus oreophilum

Amelanchier aliafolia scopartum
Crataegus Douglasis Artemisia camporum
Prunus demissa ay frigida
Pachystima Myrsinites es cana

Rhus Rydbergti
The following species seem to have entered from the south-
ern Rockies or the Great Basin:

Yucca glauca Opuntia polyacantha
Atriplex truncata Mammuillaria missouriensis
Sarcobatus vermiculatus a vivipara
Eurotia lanata Gilia pungens
Grayia spinosa Sambucus glauca
Ribes aureum Aplopappus suffruticosus
Rosa Fendleri -Tetradymia canescens
“« ultramontana ye spinosa
Cercocarpus ledifolius Chrysothamuus nauscosus
mn montanus 7 viscidiflorus
Purshia tridentata Artemisia tridentata
Amelanchier oreophila o spinescens
A utahensis

Yueca is a common plant in many localities on the plains
of eastern Montana. It is usually found on the slopes of the
foothills or benches. On the other hand Opuntia polyacantha,
also plentiful in the same region, is more abundant on the low
flat benches. The most interesting species in the above list is
the mountain mahogany, Cercocarpus ledifolius, which is found
as far north in the Rocky Mountains as Helena. It is plentiful
about the head of the Bitter Root Valley where it has apparently
arrived from the hills of southern Idaho across the Bitter Root
Range. Purshia probably came from the same source but is
somewhat more widely distributed through the Bitter Root Val-
ley and sparsely farther north in the Flathead Valleys and

T4 FOREST DISTRIBUTION

elsewhere. Both of these occupy the highlands. the former the
higher rock outcrops. the latter the more gentle southern and
western slopes of the foothills.

In addition to the species discussed above there remain a
number of woody forms as to the origin of which there seems to
be no evidence. Some of these doubtless are indigenous to the
region under discussion. others. as Harshberger suggests. may
be descendants of species which at some past time had a much
wider distribution in the same region.

CHAPTER IV.

GENERAL Forest ASPECTS,

the State, or nearly 50,000 square miles. Over much of

this area the landscape is diversified by alternate forest
and prairie, and the forests, thus divided, extend further east
and west and reach to farther limits than the statement in square
miles would imply. The forests are continuous for considerable
distances only, as a rule, above certain altitudes (4000-5000
feet) ; below this forests and prairies alternate. The western end
of the state, owing mainly to climatic conditions, is far more
heavily timbered than the part east of the Continental Divide.
From the western boundary eastward the forests in the southern
part of the state become gradually more open; in the northern
part their volume is better sustained. The rainfall is much
heavier in the northwestern part than in the southwestern and
the forest development proportionately greater. It presents on
the whole a more rugged topography and a greater variety of
exposure and shelter. The heavier precipitation is reflected in
the drairiage and the frequent lakes, springs and streams pro-
vide the mesophytic conditions requisite for heavier forests and
a greater variety of species. Prairies are smaller and less nu-
merous and continuous forests occur at lower levels, at 4000 feet
and above.

In the southwestern part of Montana the lower margin of
the continuous forest is at least 1000 feet higher than in the
north. About the head of the Bitter Root, the Jefferson and
the Big Hole the grasslands may extend in some places to 6000
feet or even more. The topography is less rugged, the country
much drier, and the forests accordingly more open. The forest
here is sufficiently open to admit grasses and other herbaceous
plants. The number of shrubs, however, is much less than in
the north, both as to species and individuals.

Vy | NHE forests of Montana cover about one-third the area of

Throughout the region coniferous vegetation is dominant.
Yellow pine and Douglas spruce are the prevailing species over
the greater part of the region, as seen from the highways. Broad

7

5

76 FOREST DISTRIBUTION

leaved, deciduous vegetation, is dominant. as 2 rule, only along
the bottom lands and stream banks. It is hardly too much to say
that in these places nine-tenths of the forest consists of the spe-
cies of Populus, Salirc, Alnus and Betula. On the western slope
Populus trichocarpa is the only large cottonwood of the river
bottoms. It is usually accompanied by Alnus tenuifolia and
Betula fontinalis. These three species are found along every
stream on the western slope. Along with these. usual or fre-
quent, are Populus tremuloides. Salix cordata, 8. fluviatilis,
Cornus stolonifera, ete.

On the eastern slope and the plains the bottomlands are
commonly covered with Popuius Sargentii, accompanied more or
less frequently by P. tremuloides, Salix fluviatilis, Betula fon-
tinalis, Amelanchier alnifotia, Acer Negundo, Lepargyraea ar-
gentea, ete.

As to the upper limit of tree growth there seems to be no
clearly defined timber line except such as may be due to the
desiccating influence of wind. Only the crests are usually bare
or occupied by stunted pines. spruces or firs and this way oc-
cur at relatively low altitudes of 6000-7000 feet, while on neigh-
boring mountains of greater elevation forests may be found ex-
tending much higher up the slopes. Other factors, like the steep-
ness and ruggedness of the land have much to do with the matter
of forest occupation both as to moisture and as to foothold.
Consequently high and pinnacled crests like the southern peaks
of the Mission Range. the Bitter Roots from St. Mary's Peak
to the Nez Perce Pass. the precipitous declivities of the main
range of the Rockies from Glacier Park to Lewis and Clark
Pass, the high summits south of Georgetown, all are barren, due
in part to their elevated exposure and to the inhospitable charac-
ter of their surface. Elsewhere the high elevations of rounded
contour are forested sometimes by pines, firs or spruces. some-
times by an open stand of Rocky Mountain juniper (J. scopu-
lorum) as shown near the Mullan Pass and the Continental Di-
vide southeast of Butte.

The principal trees in the forests west of the Divide are
Pinus pondcrosa, P. contorta and P. albicaulis, Larix occidentalis,
Pseudotsuga tarifolia, Picea Engelmannii, Abies lasiocarpa, and
Juniperus scopulorum, Locally Pinus monticola, Tsuga hitero-

GENERAL FOREST ASPECTS 17

phylla, Abies grandis and Thuja plicata are important, but these
are confined to relatively narrow areas. Among the rarer or
less important gymnosperms may be included Larix Lyallii,
Tsuga Mertensiana, Juniperus scopulorum, J. communis, and
Taxus brevifolia.

East of the main Divide the forest is more open and assumes
a more xerophytic aspect. In the more sheltered canyons good
forests are developed, but along ridges and slopes, more or less
exposed, the trees straggle out in open stands, with lessening
frequency as they descend to the foothills and plains. The num-
ber of species diminishes also and only the more hardy are rep-
resented. The following are the more common trees on the east-
ward slope of the Rockies and the outlying ranges. Pinus flexilis,
P. contorta, P. ponderosa, Pseudotsuga taxifolia, Juniperus scop-
ulorum, Picea Engelmannii and Abies lasiocarpa. J. communis
and J. Sabina also occur, the latter more or less common on
prairie slopes. The spruce and fir are confined to the higher
elevations; the most common trees at low elevations and about
the foothills are the vellow pine, the Douglas spruce and the
Rocky Mountain juniper. These are usually present on the
bluffs and along the rim-rock at the margins of the valleys of
the Yellowstone and the Missouri and their countless tributaries
over most of Montana down to the eastern boundary. The higher
elevations of land known as the Crazy Mountains, the Snowy
Range, the Bear Paws and the Pryor Mountains, and others all
support forests of some or all of the above species in greater
or less numbers and sizes. However, the forests as such are
found only on the mountains and become less and less frequent
eastward until the Black Hills are reached. The following sum-
mary presents the usual distribution of the species and their
approximate altitudes in different parts of the state.

In considering the problem of forest distribution it is essen-
tial to determine as far as possible the relative abundance of the
constituent species and the place which each occupies in the
composite formations of which it is a part: Jt is likewise impor-
tant to determine the areas occupied by the several species and
to relate the species wherever possible to their controlling factors.
In connection with the facts of horizontal extension the altitudinal
distribution also claims attention, especially in a region where

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GENERAL FOREST ASPECTS 79

differences in altitude are so prcnounced and where soil and
climatic conditions present wide variations.

The facts of horizontal and vertical distribution are pre-
sented from various sources,* with data on the relative impor-
tance of the various species. By this means it is hoped to present
a conception of the forest as it appears in different parts of
this region. It is admitted that the data here assembled can
be interpreted only in the most general way. The figures on
percentages are to be taken merely as indicators of the approxi-
mate proportions of the species in the forest covering of the
area in question, and not as an accurate final result. The extent
of the area and the extent of the work involved must entail a
large probability of error. The figures presented below, how-
ever, point to safe conclusions as to the facts of general distribu-
tion, which is the purpose of this paper, and from this stand-
point it is doubtful whether any further refinement of the per-
centage data would be either necessary or profitable.

A study of the forests of the northern Rockies brings into
view certain aspects of their composition and distribution related
to particular topographic and climatic conditions of the different
geographic units or sections which they occupy. For convenience,
therefore, as well as for conformity with the points of ecological
significance the area will be considered by sections determined
in accordance with certain physiographic features which either
individually or in groups seem to stand in some important rela-
tion to the flora. Fifteen such sections are recognized. The
first three lie in adjacent parts of Idaho, the forests of which,
in their composition, should be considered in connection with
those of Montana, as in fact being in large degree the immediate
source from which many of the species have found their way
eastward into the higher mountains and valleys. The sections
are numbered from the west and will be discussed in the same
order. They are named for some significant physiographic fea-
ture. See Figure 12.

The first or Priest Lake Section occupies the panhandle of
Idaho and includes the drainage of the Priest River and the
Kootenai in Idaho. It extends from the international boundary

*The writer wishes here to acknowledge with thanks the generous co-
operation of the officers of the Forest Service in District 1, who supplied
much of the information essential to this discussion.

80 FOREST DISTRIBUTION

southward to include the southern arm of Lake Pend d’Oreille.
It includes some of the most mesophytic conditions of the region.
A survey of the forest of this section gives the following data:

Table 9. Forests of the Priest Lake Section.

Species re ee | Range of Altitude
Pinus monticola -....-.....00-.----eeeeeenee 21-30 9000-5000
OF MOMAEFOSO:. <2.:22.2.20ss-dinsecheeentne 7-10 2000-4000
£6 CONE OPED, wecccc cscs cesiecesseeceeeccseeee 2000-6000
66 ALD COATS a. eeeeeeee ee ieeeee ene 6000-7000
Larix occidentalis ......22...2.-..:0------- 18-20 2000-5500
Picea Hngelmannti «20.2.0... 2-2 20-25 2000-7000
Tsuga heterophylla ......--.------.0----- De 2000-4500
Pseudotsuga taxtfolia -.......--.---------- 8-15 2000-6000
Abies QraNndig --...-.....00 n= cee 5- 2000-5500
6 MASUOCEP IG: 2.scsenece-osccctesscsnceasess 5000-7000
Thitge: pUcata .ec22- cee ceases 9-10 2500-5500
Juniperus scopulorum -......-.--------- 3000-5000
a COMMURIS ..c.ceceeeeeeeeee 4000-6000
Taxis dvr evifolid 2.2... ee 2500-5000

The forests of this section vary from open stands of yellow
pine and Douglas spruce in some localities. or in others of typ-
ical forests of lodgepole, to the heavy forests of white pine,
hemlock and grand fir, such as may be found along the bot-
toms of Priest River. In this stand is a copious undergrowth of
young hemlock and arborvitae, but in many places the forest
is too dense to support more than a light undergrowth of broad-
leaved shrubs.

The second section, here designated as the Coeur d’Alene,
lies southeast of the first. It extends for about 130 miles in
length and from 50 to 75 in breadth. It lies about equally in
Montana and Idaho, across the Coeur d’Alene Range. It includes
on the western side the drainage of the Coeur d’Alene and St.
Joe rivers in Idaho, and on the Montana side the lower valley
of the Clark’s Fork and reaching to the summits of the Cabinet
Mountains and Evaro Pass. Its southeastern corner lies near
Missoula at the junction of the Bitter Root and the Clark’s Fork
rivers, This area, as discussed above, is notable for the richness
of its flora. It includes the only stations thus far reported for
Tsuga Mertensiana in this region, and in shrubby and herbaceous

GENERAL FOREST ASPECTS 81

forms alike is of marked interest. In this section the species ap-
pear distributed as follows:
Table 10. Forests of the Coeur d’Alene Section,

Species | ee | Range in Altitude
Pins MONEMCOlE -22..20.2002ceevneeeee nee | 2-36 2100-5000
€8 PONMEL OSG ..ecccecceccecceceesseneeneen | =. 2-25 2100-5000
E COMBOTEG cities aetna | Qa 7 2100-7500
6 ADICAUNS occ eeee teeter | 4500-7000
Larix occidentalis 2.00... 6-24 2100-6000
BOS VGN lacie ese ee 7000-8000
Picea Engelmanntt -..---2-----:--------- 2-11 2500-5500
Tsuga heterophylla 00.0.0... 7 2100-5500
6 Mertensiana 0.2.0.2... 4000-7000
Pseudotsuga taxifolia -..-...2.. -..----- 13-25 2100-7000
Abtes grandis 22. 0-20.00 vee -12 2100-5000
£6 YASIOCOP PA oo. ceeeeereee ee eeeeeeeee 1- 4000-7000
Juniperus scopulorum -....2..2..------+ 5-15 2100-5500
Thaga PWicata 2.2 cies cence een 3000-5000
ee COMMUNIS one 4000-6000
Tarus brevifolia .....0...--1c eee 2100-5000

With referenec to the differences of percentage composi-
tion and altitude some of the facts are worthy of comment. No-
where is the influence of a mountain range more evident. The
Coeur d’Alene section as above described is traversed by a water-
shed of some 5000 to 7000 feet elevation, extending from north-
west to southeast. To the north east flow numerous lesser
affluents of the Clark’s Fork on the Montana side, to the south-
west on the Idaho side the St. Joe and the Coeur d’Alene rivers
flow to Lake Coeur d’Alene. This ridge lies squarely across
the path of the rain-bearing winds with the result that the pre-
cipitation is greater on its western slope. This, together with
the greater relative humidity of the lake region supplies the
requisite couditious for the growth of the white pine and the
species usually associated with it. On the western slope the
white pine may reach as much as 36% of the stand, while on
the east it is estimated at about 2%. Abzes grandis forms 12%
on the western slope and a neghgible amount on the eastern.
Thuja plicata forms 15 % on the western slope, 5% on the eastern.
Tsuga heterophylla forms 7% of the stand west of the ridge and
a negligible amount on the eastern side. Similarly Engelmann

82 FOREST DISTRIBUTION

spruce favors the western slope. On the other hand Pinus pon-
derosa, Laris occidentalis and Pseudotsuga tacifolia are far
more heavily represented on the eastern side than on the west-
ern, forming respectively 2, 6, and 13% per cent on the western
side, as against 25, 24 and 25% on the drier eastern slope.

Another feature of the difference is in the vertical distri-
bution of the species. On the western side the lower limit of
distribution is from 700 to 1000 feet below that of the eastern
and the upper limits from 500 to 2000 feet lower. It is noticeable
also that certain species like the grand fir and western hemlock
are confined to a much narrower vertical range on the eastern
than the western slopes, falling within a zone of 1000 to 1500
feet in the former and of about 3000 feet in the latter case.
These facts can only.be interpreted in terms of the moisture
conditions and the lower limits of temperature encountered at
the higher altitudes. Several species listed in the table were
not of sufficient importance to merit calculation as to their
quantitative relations in the forest.

The third or Clearwater section lies on the western slope of
the Bitter Root Range and embraces the drainage of the upper
branches of the Clearwater, its North, Middle and South Forks.
The area reaches the summit of the Bitter Root divide on the
east and covers about 100 miles from north to south and from
40 to 60 east and west. The course of its principal streams is
mainly westward to a junction with the Snake River.

In its northern part the forest vegetation is more nearly
related to that of the western slope of the Coeur d’Alenes. The
white pine, arbor vitae grand fir and Douglas spruce are the
dominant species. In its southern part these species appear
very sparingly, and the dominant species are yellow and lodge-
pole pines and Douglas spruce. In this part the climatic con-
ditions are merging into those of the arid plains of the Snake
Valley. The marked variations in the percentage of different
species will thus be interpreted accordingly.

GENERAL FOREST ASPECTS 83

Table 11. Forests of the Clearwater Section.

Species | Beate ciate | Range in Altitude
Pinus monticOla. 2.20.22. eee eee ene 30 1800- 6000
£6 PONAEV OSA «2. ..-2-2220ce2cceeceeeseeee 2-25 1700- 7500
£6 CONFOTED eae eeneeeeeteceeteteeeeeenee 7-40 2500- 9500
66 AUDIO UTES oie eee eenneneee 1 5000- 6500
Larix occidentalis 2.2... 7 3000- 5000
OETA OLY aos Re Aaa A 7000-10000
Tsuga heterophylla .......0.00---00--- 3 5000- 6500
Picea Engelmannia 2... 5- 6 2000-10000
Pseudotsuga taxifolia 2... 14-20 1800- 7000
Abies grandis 22... 2.5-18 2000- 5500
66 UMSVOCON DA 222s cteeteecteceee 2 4000-10000
Thuja PUcata, ......22.c 0 eee eee 14 1800- 5000
TUNIPCLUS SCOPULOTUWM .222.2020-2--220-+ 2000- 5000
ee COMMUNIS oo seen eens
Taxis brevt Poli -..-.2..-.ccccceceeeeees 2000- 4000

Here also in the southern and drier part of the section the
various species are found at correspondingly greater elevations.

In the first three sections which cover an area 60 miles or
more in width from the Canadian boundary to the Salmon River,
a distance of about 250 miles are represented the forests of
northern and northeastern Idaho lying adjacent to Montana.
This constitutes the White Pine Belt of the Rocky Mountains.
With the white pine are the species usually associated as men-
tioned above and the strip is favored with more ample precipi-
tation and higher relative humidity than the areas lyine farther
to the east. Although the species typical of this belt do oecur
in the sections subsequently to be treated they are not except
in localities, a dominant feature anywhere over large areas.
These conditions are almost entirely limited to the valleys of
the Flathead and the Kootenai.

The Kootenai Section, No. 4, covers the area drained by
the Kootenai River in Montana, about 3200 square miles. This
river crosses the international boundary and enters Montana
near the 115th Meridian, flows south about 50 miles and turning
sharply to the northwest, recrosses the boundary about 60 miles
west of its first crossing. The southern boundary of this sec-
tion is the summit of the Cabinet Range, the eastern the divide
between the Kootenai and the Flathead, sometimes known as the

84 FOREST DISTRIBUTION

Flathead Mountains. The Cabinet Range rises, especially at
its eastern end to heights of 8000 to 9000 feet, rugged and pic-
turesque. The Flathead Mountains are lower. In the bend of
the Kootenai lies the Purcell range, only its southern end reach-
ing into Montana. The range is fairly even in height except
a group of sharp summits which rise to 7500 feet near the south-
ern end of the chain.
Table 12. The Forests of the Kootenai Section.

Species | anne eadion | Range in Altitude
Pintts PONACV OSA -22.-222.s2eeeeeeeeeeenee ee 9 1900-5000
OB" POTTNCOLG: excxcctes tpt es 3 2200-4000
PE“ CORLOTE G2 saaes see vee 17 1900-6000
£5 QUDICQUIIS © eectececonl ere otnnn ooo 5000-7000
Larter occidentalis ....-.2-...---.------- 21 2000-4000
OS CGY OUR ee fee eS 7000-73500
Picea Engelmannti 22.02.00 | 21 2000-7000
Tsuga heterophylla ...........22..--------- 14 3000-4000
Abies GPANAIS -o222.c2eeeeeeee eevee ees 14 3000-4000
* lasiocarpa 2200-7000
Pseudotsuga taxifolia -........----------+- 18 1900-5000
LNG PUCOLO Biceps ceceeenog eee 2200-3000
Juniperus scopulortm 2.22.
ee COMMUNIS eee eeeeeeeee eens
Taxus brevifolia 0.022222 anne

Most of the Kootenai section is heavily forested. In the
narrower valleys, on low flats and about lakes are suitable con-
ditions for the white pine, arbor vitae, grand fir and hemlock,
on some of the upper benches are extensive pure stands of lodge-
pole pine, sometimes of young larch. The hills are often cov-
ered with open growths of vellow pine.

The fifth, or Flathead Section, covers the drainage of the
Flathead River, including the North, Middle and South Forks
and the Swan river. It extends its northern line 60 miles along
the Canadian boundary and reaches south 180 miles to the
extreme sources of the South Fork. Its western margin joins
the Kootenai Section. its eastern follows the crest of the Conti-
nental Divide. Tt includes a part of Glacier National Park.
The Flathead Section is one of the most significant of Montana,
both in its topography and its vegetation. It includes several
high and rugged mountain ranges. some of them bearing gla-

GENERAL FOREST ASPECTS 85

ciers. The marks of previous glaciation are extensive and con-
spicuous. Numerous lakes, large and small, are fed by cold
mountain streams, many of which flow from glaciers or perpetual
snows. There are many cirque basins occupied by deep, cold
and dark waters and fringed by forests of fir and spruce.

Table 13. Forests of the Flathead Section.

Species | compaaition| Range in Altitude
Pinus mMontecola 22.2 3.5-11 3000-5000
6 PONderOsa oe ee eee neces 2.0 3000-4000
ES SCONE OIE G = Riso ounces 1.0-14 3000-6500
6 ALDICAUHS octet eee eee 5-1 4000-7000
Larix occidentalis ....2....0.2..20000----+) 35.0-50 3000-5000
OY QUAG oie oe ern eed 5000
Picea Engelmanntt 22.20.2002... 90.0-23 3000-6000
Tsuga heterophylla 2... 1 3100-
Pseudotsuga taxifolia 2.2! 11.0-17 3000-6000
Abies grandis... seen 1 3000
a TCLs 1) 1.0 3000-7000
Thuja Plicata ........ecccccccereneeeeeeeene 17 3000-5500
Juniperus scopuUlorunr 22-2 3000
of COMMUMNAS ...e.eeceveeeeeeeeeee 3000-6500
Taxus brevifolad ...........cecceeeeenen ee 3000-6000

In this section it will be observed that the white pine, grand-
fir, hemlock and arbor vitae are still present but in greatly
reduced amounts. Larch and spruce are the main species with
lodgepole pine locally dominant. The white pine formation
appears usually in the narrower valleys and canyons, protected
from excessive influence of wind and sun. The essentially moist
condition of the soil is maintained, and atmospheric moisture is
relatively high. While the white pine is a less common tree
than in some other sections, vet some of the largest trees are
found, one on McDonald Creek in Glacier Park measuring seven
feet in diameter. Hemlocks also reach a large development in
Glacicr Park, as in the case of a grove near Avalanche Basin,
where some of the trees are three feet or more in diameter.

The ranges in altitude will be noted. In nearly all of the
species the lower limit is near the lowest possible altitude in
the section. The upper limit in some of these cases extends to
the uppermost altitude habitable by trees. This range differs
but little in different parts of the section.

86 FOREST DISTRIBUTION

The sixth section includes the Bitter Root Valley, an area
of about 3000 square miles. It is bounded on the west by the
summit of the Bitter Root Mountains and on the southeast it
reaches to the crest of the Continental Divide. On the east its
margin rests upon the top of the divide between the Bitter Root
River and Rock Creek.

Table 14. The Forests of the Bitter Root Section.

Species Ghinpasition | Range in Altitude
Pinus PONdCrOSG ...2.22.22022---2-222 222 | 32.0 | 3500-7000
COMLOTEO, mcncericrens onc. - 40.0 3500-8000
* albicaulis 2 7500-8500
monticola eat
Larix occidentalis .....2...22...0-------- 3 3500-5000
Ae PPT OLED: eta Tic ado 7300-9000
Picea Engelmannii 2-22-20 1.6 3500-7300
Pseudotsuga tarifolia 242 3300-7000
‘ Abies lasiocarpa .........-.- 5000-8000
grandis 2... 4000-5000
Thuja plicata -.....22222.22----- 4090-5000

Juniperus scopulorum

It will be observed that the prevailing species in this sec-
tion are those adapted to drier conditions. viz., the yellow and
lodgepole pines and the Douglas spruce. All others are in a
small minority. The species of the humid forests. the white
pine and its associates. are now mostly confined to the upper
canyons of the Bitter Root Range. This conforms exactly to the
climatic conditions of the section. The Bitter Root Valley has
an annual precipitation record of 10.71 inches. representing the
average of a good many years of observation. This is a lower
figure than is shown at most of the plains stations in eastern
Montana. They are, however, the observations at only one sta-
tion that of Hamilton near the center of the valley. It is easy
to understand this condition since the whole valley is sheltered
on the west by the lofty Bitter Roots, which effectually intercept
the rain bearing western winds. The temperature of the Bitter
Root Valley is, moreover, usually a little higher than that of the
neighboring localities, which must further influence its water
supply.

The lower limits of vertical distribution are considerably

GENERAL FOREST ASPECTS 87

higher here than in the preceding sections, a fact correlated with
the dryness of the region. The floor of the valley is almost de-
void of the species cited and the foothills are mostly bare, rising
to the scattering pines at about 3500 feet. The whole section
is distinctly in contrast to the northern portion of Number 3
on the opposite side of the Bitter Root Range.

The Hellgate Section is the seventh of the series. It em-
braces the drainage basins of the upper Clark’s Fork (formerly
called the Hellgate) and the Blackfoot. On the east and south
it reaches to the Continental Divide, which forms a huge are
about the heads of these streams and their principal tributaries.
The western limit of this section is the Bitter Root Valley. The
whole area is nearly 8000 square miles. It rises gradually to
the eastward for about 80 miles, from an altitude of 3200 feet
near Missoula to 6000 to 8000 on the crest of the Divide. It is
a region of comparatively light rainfall and moderate tempera-
tures. Prairie and forest alternate according to slope and ex-
posure and the forest is often open and the trees of medium size.
The upper valley of the Blackfoot widens out at 4000 feet into
a broad basin twenty miles or more across, treeless and rela-
tively arid. The upper Hellgate valley presents much the
same appearance. Much of both basins is covered with
glacial gravels, and drumlins are common especially in
the valley of the Blackfoot. The grass range is extensive, and
the rolling foothills gradually merge into the wooded slopes
which extend from 4000 or 5000 feet to many of the high sum-
mits.

Table 15. Forests of the Hellgate Section.

Species Gemolticion Range in Altitude
Pinus PONE OSG .-..2-.22.2-20-2002eeeen 3.5- 3500-7000
6 CONFOTEG einen eceeeeeeeeeeeeeeeenes -72 3500-9000
66 @bbicaUlis ec eee 1.0- 6000-9000
Larix occidentalis 22.20.2202 -1--2---- 5 3300-6000
OO TSU QING secs nrcst ested eas 7000-8500
Picea Engelmannti 22.2.2. 2.0- 3 3300-9000
Pseudotsuga taxtfolia .......2-2..-.0---- 15.0-24 3300-7000
Abies lastoCar pa -...22---2-2-1ceeeeeeeees 1.0- 3500-9000
Juniperus scopulorum + 3300-5500
7 COMMUNIS oo eeceeeereeeeeees 3400-5500

838 FOREST DISTRIBUTION

In the previous cases the percentage composition was in
terms of volume estimates; in this it is in terms of the forested
areas. In neither case does it give more than a general impres-
sion of the relative importance of each species. The figures on
this area are with reference to the ‘‘type’’ as it is called 5x the
Forest Service, which means practically the same as the terms
society and association in the ecological sense, as where species
in pure or mixed stands assume certain characteristic aspects
under the control of climatic and physiographic influences.

In this case it will be seen that the leading species are
lodgepole pine, Douglas spruce, larch and yellow pine. The
larch is confined chiefly to the western side of the section, and
to northern slopes and creek bottoms. The yellow pine. often
mingled with Douglas spruce, occupies the southern slopes but
with its lower limit at 4000 to 5000 feet elevation. The lodge-
pole is found in dense and extensive stand at high elevations
along the main range of the Rockies. Pinus monticola and Abies
grandis are rare in this section and are found only in isolated
localities; however, limited stands of white pine are to be found,
as in the upper end of the Blackfoot valley close to the Divide,
on the Clearwater and elsewhere. Where the moisture is suffi-
cient in the soil, that of the atmosphere seems deficient or the
temperatures too low. For the most part this section seems to
be beyond the easternmost limits of the white pine, grand fir,
western hemlock, arbor vitae and western yew.

The eighth division of the Rocky Mountain forest will here
be called the Sun River Section. Its western margin lies along
the continental crest from the Canadian boundary to the 47th
parallel in a strip 20 miles or less in width. It lics on the east-
ern slope of the Divide in the narrow timbered zone between the
mountain ridge and the prairie foothills. Its northern portion
includes a part of Glacier National Park. The Sun River Valley
is heavily timbered. but the Teton and Marias Rivers traverse
elevated plains and prairies.

GENERAL FOREST ASPECTS 89

Table 16. Forests of the Sun River Section.

Species Gemmtciaen | Range in Altitude
LUNs CORTOTEO occ cece erence cee 50 4000-8000
eS ORLBUBN LDS ie extras eect ts Lk 10 5000-8500
Picea Engelmanntt .2....ceccceee 20 6500
Pseudotsuga taxifolia —.........020022--. 15 7500
Abtes lasiocarpa ......... -...- jenesceseoees 4 8500

The above are the principal species found in this strip and
their approximate proportions. The larch and whitebark pine
are together reduced to about 1% of the entire stand. They are
present only near the top of the Divide where they have dropped
over from the western slope. It is probable that Pinus ponderosa
is also represented, though sparingly, as well as small quantities
of Juniperus scopulorum, J. communis and J. Sabina. The sit-
uation on the whole is one of low rainfall and of general difficulty
for forest species.

The Belt Section (No. 9) extends from the top of the Con-
tinental Divide near the head of Clark’s Fork eastward over
100 miles including the Big Belt and the Little Belt ranges.
From north to south the area extends roughly from Great Falls
to the Three Forks of the Missouri, about 120 miles. This sec-
tion is very largely prairie. Only the higher elevations are
wooded, so that the forest for the most part lies above 5000 feet.
Besides the Belt Ranges are several othcr more or less elevated
masses, the Highwood Mountains and the Little Rockies, which
also are forested.

Table 17. Forests of the Belt Section.

Species _- | Range in Altitude
Pints CORtOTtA -..2..2---2-22020 eee 56-84 5500-8200
66 PONEEL OSG ~-.n2-222--2-eeeveeeeeeeenn 7-15 7500-8300
BE FUGUES ct 3 nat vas Stee a 7500-8300
OE LDC CONUS cs ccoesscee tees 7000-8300
Picea Engelmannti .....2-22.2000------- 2- 6 7000-8000
Pseudotsuga tacifold «....-...--------- 5-44 6000-7500
Abtes lastOCarpa ...--2-.2-2.2000--eeeen 7000-8300

The percentages here are in the area covered by the several
species. The variations in the percentages indicate their relative

90 FOREST DISTRIBUTION

importance on the different mountain ranges in this section.
Leiberg (32) gives the volume per cent for the different species
in the Little Belts as follows:

Piss, FlOL MAS: co. 2 csserveces eee ee 8.2
CO" GUDICONETS, 22 oe) hci eter en sere 009
SO! SCOWEGRED. eacsces santas each cs oan eget ave 34.2
££ PONKETOSE) cee eoessncicinteete oe ee 07

Picea Engelmannit -.-.----.----------- 114

Pseudotsuga tarifolia. .........2:.2.21---20.-0 en 44.7

Abies LASIOCANPA «...---------2--2-0- een 14

In addition to the above species it is probable that Juniperus
scopulorum and J. communis are likewise present. Isolated as
most of the outstanding ranges are, the influence of the climatic
conditions are readily felt, so that the lower timber line is fixed
at elevations unusually high. In sheltered canyons and valleys,
however. many of the species may descend to where they open
out upon the plains.

The Three Forks Section (No. 10) is an area 140 miles from
east to west and 100 miles in round figures from north to south.
The westward direction of the Continental Divide from the vicin-
itv of Butte, and its wide curve to the south and thence to the
east to Yellowstone Park forms a huge embayment, drained by
the three main sources of the Missouri, the Gallatin, the Madi-
son and Jefferson rivers, which push their ultimate branches
to the high walls of this huge amphitheater. The western por-
tion of the basin is known as the Bighole. particularly that part
drained by the Bighole River which is the main western branch
of the Jefferson. The basin is traversed by several low moun-
tain ranges, and in altitude most of its floor lies above 5000 feet.
The country is largely prairie and only the highest elevations
are forested and these with few species and comparatively meager
growth. It is largely glaeiated and climatically dry and cold.

GENERAL FOREST ASPECTS 91

Table 18. The Forests of the Three Forks Section.

Species eae Geis | Range in Altitude
PUNUs PONAECL OSG ....---2.20-2seeeeeeeeeeeeeen 5600- 6500
OP SCONEOV ED icon CC Oo ne a cag 60-75 5600- 8500
66 albicaulis eee eee 14 7000-10000
BO POMS: oa hk AS oN ea te SS cel 7000-10500
Picea Engelmannit -......22-:01--0--- 4-5 5500- 8500
Pseudotsuga taxtfolia ....22-2.2.00--- 20 5000- 8000
Abies lastocarpa, «....2.-..--2:-21-0--- 7000-10000
Juniperus scopUulorum, .......2--2------ 6000
ee COMMUNIS......-.20c0c- anne

The forests are confined to higher elevations mostly above
6000 feet and consist mainly of lodgepole pine as the main zone,
merging below into yellow pine and Douglas’spruce and above
into limber and whitebark pine, Engelmann spruce and alpine
fir. In some places the lodgepole forest covers the Divide at
7000 feet. Only as the summits rise to greater heights does the
character oftheir forest covering assume the aspect imparted by
the spruces and firs, though in the sheltered canyons these genera
may descend much lower.

The Yellowstone Section (No. 11) occupies the upper Yel-
lowstone drainage in Montana. From the uorthwest corner of
the Yellowstone Park it extends 120 miles along the southern
boundary of Montana, and 100 miles to the north including the
Crazy Mountains. In this section, covering some 10,000 square
miles, are the highest peaks and some of the most rugged topug-
raphy in Montana. From the Absaroka and the Beartooth
ranges flow numerous streams northward to the Yellowstone
River, which from the north gains a few affluents from the
Crazy Mountains. To the west the Gallatin and Bridger ranges
form the watershed between the upper Yellowstone and the Mis-
souri, in altitude varying from 5000 feet in Bozeman Pass to
10,000 on some of the higher peaks. In the Absarokas the high-
est peak reaches nearly 13,000 feet.

The Yellowstone Valley ‘is broad and treeless, except along
the immediate stream bottoms. The coniferous vegetation occurs
above 5500 or 6000 feet where a fringe of limber and yellow
pine, Douglas spruce and juniper marks the lower edge of the
forest. Between 6000 and 8000 feet the lodgepole pine forms

92 FOREST DISTRIBUTION

almost the whole of the forest, but above 8000 feet gives place
to white bark pine, alpine fir and Engelmann spruce. The
upper timber line occurs at elevations of 9300 to 9800 depend-
ing on direction or exposure. though on the Beartooth Mountains
toward the east it ascends in places to 11,000 feet. At the timber
line Engelmann spruce is the dominant and most conspicuous
species.
Table 19. The Forests of the Yellowstone Section.

Species ee ee | Range in Altitude
Pinus PONM OOS 0s eee eee | avoo |
contorta ...| 90-60 : 6000- 8500
flerilis ...... a | = §000- 8000
‘ albicaulis ois 7500- 9000
Picea Engelmannii..... 0000. 1... : 15 6000- 9000
Pseudotsuga tasrifolia .....00000000-..... 21-30 . 5000- 8000
Abies lasiocarpa nee 7000-10000
Juniperus sCOpulorum 2.0.20... | TAN,

The above species are all represented in this section. though
some of them very sparingly, and the yellow pine probably the
least of all. The above figures were tabulated from Forest
Service data and have the advantage of being the most recent
obtainable. Leiberg, (31). however, gives a somewhat different
and more detailed account as follows:

TERTNG LER LUG cement oo ee rre seaman oe ss 23S
RES COMER ea wh eat in teed Reet 45.6
BES DONO CROSOE ioe ae acer eae wean 005
ES UD UC GINS: ies sets eat oan ct yressaetamn Ss 5.3

PHC6G PENG ELMNANIE coven w ices mesg eeeeeeleangsys 215

Pseudotsuga tartfolia 22.02. 122

ADI ES COSCO PO eestor te |

In this estimate trees are considered of three inches basal
diameter and upwards. Leiberg states that the lodgepole pine
forms fully 75“ of the forests below the subalpine zone, and
even as much as 0 in its own proper belt akove the lower
fringe occupied by Douglas spruce and limber pine. Leiberg
cites also the occurrence of Pinus monticola in one locality in
the Absarokas but this is very doubtful, as it there would appear
to be in a locality far removed from its known range and in the
only position reported for it cast of the Divide. As it is not

GENERAL FOREST ASPECTS 93

now known to the Forest Service in that locality and as the con-
ditions would seem to be so unlike those of its usual habitat, it
would seem that Leiberg’s report is in error on this point. Engel-
mann spruce and Douglas spruce are common trees throughout
the section in their particular zones. Though the latter is lim-
ited to a lower belt, the former is found as low as 6000 feet and
from there up to timber line.

The next is the Bearpaw Section (No. 12) including for the
most part the Bearpaw Mountains and the Sweetgrass Hills,
with altitudes of 6000, 7000 and 8000 feet respectively. These
have scant forests of lodgepole and yellow pines, and Douglas
spruce. Two junipers (J. Sabina and J. communis) oceur in
this region. This section covers about 20,000 square miles, ex-
tending along the northern boundary about 200 miles and south-
ward about 100. It embraces a good deal of the Missouri Valley
and the upper sources of the Milk River, besides portions of the
drainage of the Marias and the Teton. It is mostly prairie with
elevation ranging from 3000-4000 feet. The forests where pres-
ent are found mainly above 5000 feet.

The Snowy Section (No. 13) is occupied mainly by the
Snowy Mountains and the sources of the Musselshell River.
Some of the peaks of the Snowy Range rise to an altitude of 8000
feet. Thev are in fact the farthest outpost of the high mountains
in Montana east of the main Rockies. They, like the Crazy
Mountains and the Belts, are forested only above 5000-6000 feet.

Only four species are here conspicuously represented. These
are:

Pinus CONCOVEG -2..-2.2.2222.22eeeeeeeteeeee teens 76. %
66 PON CTOSA ~-------sse2eenseeeeseeseeeeceeeeeeneeee 13.5

Picea Engelman nts «...2..2..22:21c2cceereeree eee 6.5

Pseudotsuga tawvifolia 222.2... 4.

These figures, however, are for area covered and not for
volume. It is probable also that Abies lasiocarpa, Pinus albi-
caulis, Juniperus scopulorum, J. communis and J. Sabina are
sparingly represented.

The 14th, or Bighorn Section, covers a few forested areas
in southeastern Montana. Various southern affluents of the
Yellowstone, including the Bighorn and Powder rivers drain
these hills which reach altitudes from 3000-3800 feet. Here also

94 FOREST DISTRIBUTION

most of the country is prairie, but in the hills especially in the
ravines and canyons the few forest species are distributed at
all altitudes. On portions of this area the yellow pine (P. pon-
derosa) is reported as forming 95% of the stand and Juniperus
scopulorum about 2%. J. communis is also reported.

In the 15th, or Missouri Section, no forests of any conse-
quence occur. The margins of the benches a ove the river
valley are occupied by a sparse growth of Pinus ponderosa and
Juniperus scopulorum and the isolated elevations here and there
are similarly wooded.

Reviewing the facts on general distribution as above stated.
several conclusions are evident. In the first place the species
decrease in numbers from the west toward the east. until of the
fifteen or more gymnosperms of the Idaho forest only four or
five appear near the eastern border of Montana. With the
decrease in the number of species comes also a decrease in the
volume of the forest. The same cause which limits the forest
flora to the more resistant species likewise limits the volume
production, viz., the lack of sufficient moisture. Again it will
be noted that the altitudinal range of the species in most parts
of the region is very wide. The influence which tends to nar-
row the vertical range of distribution is again the influence of
scant rainfall and the other conditions which tend toward a
xerophytic environment. Such influences not only narrow the
vertical range, but push the lower limits of forest distribution
further up the mountain slopes.

CHAPTER V

Forest ZONES AND ForMATIONS,

in the Hudsonian, Canadian and Transition zones of

Merriam (43). Sometimes the Hudsonian and Canadian
are called the supalpine and montane zones respectively (55).
The Transition is confined mainly to the foothills, valleys and
plains. The Upper Sonoran, if it extends into Montana at all,
is confined to the lowlands and benches along the rivers in the
plains and bears little relation to the forests. The zones as
such, however, are more easily defined by given sets of condi-
tions than by the species which are supposed to represent them,
since few species are so clearly limited by temperature, either
in latitude or altitude, as to be plainly identified with either
zone. This is especially true with reference to the middle zones
in this region, viz., the Transition, the Canadian and the Hud-
sonian. The upper Sonoran and the Arctic-Alpine, as repre-
senting the extremes of conditions, are the more clearly recog-
nized by some of their species which, being at the extremes of
their ranges, are mainly excluded from the other zones. Such
are the Yucca and the cacti of the former and the dwarf willows
of the latter, although even some of these may transgress their
allotted limits.

Many plants which Cary (11) cites as marking the upper

Sonoran of Wyoming occur in neighboring parts of Montana.
Among these may be mentioned the following:

v | NHE forests of the northern Rocky Mountains are included

*Populus occidentalis (P. Sargenti) Yucca glauca

i acuminata Opuntia polyacantha
*Saliz amygdaloides *Plantago Purshit
‘fluviatilis *Artemisia tridentata

Five of these, however, (*) are so widely distributed in
Montana, and in such varied conditions, as far to exceed the pos-
sible limits of the Upper Sonoran Zone.

The Transition Zone is a belt of wide vertical range and

95

96 FOREST DISTRIBUTION

diversity. It extends from the benches and plains at 2000 to,
3000 feet to the level of continuous forest at 4000 to 6000. It
may thus from cne part cf the region to another cover a vertical
distance of 4000 feet. It is largely the foothill country. varying
with exposure and location from arid to humid conditions, inter-
rupted and divided here and there by descending extensions
of the montane forests. Im some places it is the bunchgrass
(Agropyron spp.) or the bunehgrass and sagebrush (Artemisia
tridentata, A. cana, A. frigida, etc.) or these merging into open
stands of Rocky Mountain juniper, or yellow pine or Douglas
spruce, or all of them intermingled. Again it appears in areas
in composition similar to the Pacific Coast Humid Transition
with hemlock, grand fir, arbor vitae, western yew and many
other forms commonly found in the forests of the low lands of
western Oregon and Washington. The humid forest is the
more rare and is developed where neighboring areas are elevated
to the degree necessary to induce condensations and abundant
rain, where the valleys are not too wide and where the proximity
of considerable bodies of water and the structure of the soil
combine to afford the requisite conditions. These are forests
of moderate or low elevations, 2000-4000-feet. The forests of
the Transition alternate frequently with prairies and the vege-
tation of this zone extends in the southern part of Montana
about 1000 feet higher on the mountain sides than it does in the
north, reaching even to 6000 feet.

The forest of the foothills (Transition) merge gradually
into those of the montane (Canadian) belt. Especially in the
humid forest is the line of demarcation uncertain. Reference
to the tables under the discussion of general aspects of distri-
bution will show that in most sections the vertical range of many
species may be 2000 to 4000 feet and in different parts of the
state some species may be found at altitudes varying from 2000
to 9000 feet. The following figures indicate the approximate
extent of vertical distribution of the species cf gymnosperms
within this region. as far as at present known.

FOREST ZONES AND FORMATIONS 97

Table 20. Ranges in Altitude.

Species | "aiwde | “aint

Pinus PONderOsa ooo eee eevee 1,300 7,000
COMHOTLE, eso eee 1,900 9,500
Lt |: ee 1,800 6,000
£6 albicaulis. 0c 4,000 11,000
OS PVORUAS sscetsect ites ote od 3,000 10,500
Lurie occidentalis occ. 2,800 7,000
se £10 (011 een eee 7,000 10,000
Picea Engelmanntt 2c cece 2,000 11,000
Tsuga heterophylla -..0.00.0.00200000002.- 2,900 5,500
6 Mertenstana occ cece 4,000 7,000
Pseudotsuga taxifolta 0. 02... . 1,900 8,000
Abies Grandis ........ccceceeccee cece 2,000 7,000
66 VASIOCOP PA oo. eeececeeeeeee eee 2,000 11,000
Thuja Plyeedtae cece cece enn 2,000 5,500
Juniperus scopulorwm 2.0.0.0... -. 1,900 6,000
i COMMUNIS _.. see ts 3,000 6,500

ee SQDind oo... 2,500 4,000
Taxus brevifolia 000000 1.900 5,000

The wide range in altitude of the species here indicated and
the fact that at all elevations between 4000 and 6000 feet, within
their range and habitat thev are likely to be intermingled makes
difficult the distinction between the Canadian and Hudsonian
zones, or the montane and sub-alpine, if indeed there is any in
this region. The term sub-alpine, when used herein, is intended
to designate the forests immediately below the higher crests.
The trees of this belt, however, have few species which do not
descend to the foothills. The alpine fir, Abies lasiocarpa, is the
most. conspicuous tree at high elevations, but is commonly found
in the canyons about Missoula at about 4000 feet and descends
at least to 2000 feet along the Kootenai in Montana. The same
may be said for the Engelmann spruce. The white bark pine,
(P albicaulis) also a common timber line tree, is abundant down
to 5000 feet in Glacier Park, and scattering individuals may be
found occasionally in the valley of the Clark’s Fork and its trib-
utaries at 3500 feet or less. The only tree of this region which
is confined to the highest elevations is Lyall’s larch (LZ. Lyalliz)
but this species is found only in a part of the Bitter Root Range
and along the highest summits of the main divide. The black

J INNA) ‘Snow snjouaygy Munadad saqry ‘Duns “Pr worppmomm nistmapepe “ds wap
yp ‘vsomds pinay ‘snpppnoiitoa snqpqoowwy copys pun AVQ “uO ‘PAtpuopTH avou spuvlpeg, “EL “Fhy

FOREST ZONES AND FORMATIONS 99

hemlock (7. Mertensiana) is of still narrower horizontal range,
being found in this region only in a small part of the Bitter
Root and some of the mountains of Northern Idaho. Ordinarily
a tree of the high mountains it was found by the writer in the
vicinity of Wallace at: 5000 feet in association with Pinus
monticola. Juniperus communis, which forms extensive low
thickets at 6500 feet in Glacier Park, is common about Flathead
Lake at 3000 and elsewhere at various altitudes.

Of the undergrowth much the same may be said. <A few
shrubs Cassiope Wertensiana, Phyllodoce empetriformis, Salix
Barclayi, etc., are found only in the high mountains. Many
other species occur freely at elevations from 4000 feet, through-
out most of the upper fcrest belt. Among such the following

may be mentioned: Pachystima Myrsinites
Sorbus scopulina Valeriana sylvatica
Ribes lacustre Erythronium grandiflorum
Vaccinium membranaceum Calochortus apiculatus

ne uliginosum Veratrum californicum
Menziesia glabella Xerophyllum Douglasii

Before proceeding to a discussion of the several zones it is
desired to call attention to a few facts determined for the six
species most important and widely distributed. These figures
on the viability of seeds and the rate of growth of seedlings are
to be interpreted in connection with the behavior of the species
in the field. The observations which extend over a period of
several years are the results of experimental work by the writer
at the University of Montana. The experiments were conducted
under the climatic conditions of the prairie, more difficult at
Missoula than those to which most of the species are accustomed
in their natural situations. Comparisons are made between
seeds from different sources. The prosperity of plants in the
field is largely measured by their possession of advantageous
characteristics among which their seeding behavior and rate of
early growth are important.

The special study of seeds and seedlings pertained to six
species, viz., Pinus ponderosa, P. monticola, P contorta, Larix
occidentalis, Picea Engelmannii and Pseudotsuga taxifolia, The
seeds were obtained from various sources in California, Oregon,
Washington, Idaho, Montana and Colorado, and their behavior

100 FOREST DISTRIBUTION

in the experimental operations compared under dissimilar con-
ditions. The seeds within ove vear of their production showed
from 3 to 54% defective in different lots and species as deter-
mined by physical examination, while in the beds none of them
showed more than 10.4% viable. although the most favorable
conditions were provided. This estimate of viable seeds. how-
ever, is doubtless much too low, owing to the fact that it was
based upon the number surviving at the end of the first season.
The percentage of response in germination showed no relation
to the percentage of apparently viable seeds by dissection. Thus
where Pinus penderosa showed 91% viable by dissection 10.4%
actually produced seedlings. while the same species in another
lot showed 94% apparently sound there resulted only 7.7% of
seedlings, and in the case of the spruce the figures were respec-
tively 91% and 2.8% for one lot and 74% and 3% for another.
The only constant relation revealed by the studies seemed to be
that the time required for germination is inversly proportioned
to the number of seeds responding, or. in vther words. percentage
of germination and rapidity of response were directly propor-
tional, a condition to be expected. The results obtained from
the few species examined and experiments conducted under the
favorable, conditions of cultivation suggest that the rate of
propagation in the field under natural conditions must be very
much less. It is seen also that radical differences obtain be-
tween seeds from different sources, as to size. soundness, and
response in germination. facts which must weigh in the final
determination of the place which each species must occupy in
the different parts of its range.

Observation of the seedlings of this planting through a peri-
od of several vears shows a marked acceleration of growth in
height after the second vear in nearly every case, being least in
the Engelmann spruce and most in the larch. The greatest
growth in height at the end of the first season was 41. inches
in the case of Douglas spruce, at the end of the second season
the larch with 13 inches and at the end of the fourth with 59
inches. The Douglas spruce reached a height of 22 inches at
the end of the fourth vear. the yellow pine 23 inches. the white
pine 13. the lodgepole 27 and the spruce 16. though the latter
was exceptional. the heights in other lots of the spruce being

FOREST ZONES AND FORMATIONS 101

10 or 11 inches. The average heights attained are more sig-
nificant. Those for the yellow pine at the end of 1, 2 and 4
“years were respectively 2, 4 and 18 inches; for the white pine
1, 3 and 9; for the lodgepole 1, + and 18; for the larch 1, 8 and
40; for the spruce 1, 2 and 6 and for the Douglas spruce 1, 4
and 12 inches. The disadvantages of delaved growth in compe-
tition with other species are of course obvious and these are most
pronounced in the earliest stages of growth in each species. As
between these species it will be seen that the greatest growth
in height occurs in those most intolerant.

In the study of these seedlings parallel experiments were
conducted under a lath screen of half shade, 8 feet above the
soil. Under such conditions growth was usually slower than in
the open, apparently indicating the retarding effect of shade in
the growth of young trees. This result, however, was reversed
in the case of the larch and Douglas spruce which exceeded in
height those grown in the open.

Thus in the case of the seeding habits of various species
peculiar conditions obtain which affect their prosperity under
the varying circumstances of their environment. Probably few
features in the life are so intimately concerned with their preva-
lence as are those of their seeding habits.

Tue FoorHity VEGETATION,

Over a large area of western Montana, from the Divide
westward to the Bitter Root Range and embracing the
drainage of the Clark’s Fork and its tributaries the Bitter
Root, the Blackfoot and the lower Flathead, the landscape
is strongly diversified by alternate forest and prairie. Forest
distribution is in strong relation tc topography, sheltered
slopes are forested, open and exposed slopes are grassy. The
latter are usually, but not always southern or western, often
sharply marked in contrast with a vigorous forest at the turn of
a ridge which leads to a northern or eastern slope. High slopes
rising 2000 feet as in the Helleate Canyon are thickly wooded
on the north with an abrupt transition at the crest to grassland
on the southern face. Such alternation of forest and prairie
are common and on a lesser scale may be seen in miles of land-

102 FOREST DISTRIBUTION

scape in the Bitter Root and the Jocko Valleys. Even low undu-
lations on the mountainside present the same aspect. Where
the direction of the slopes fails to present a sufficient contrast —
of conditions the transition is more gradual and scattered forest
trees are sprinkled through the grass land diminishing in size
and numbers with the inerease in distance from the main stand
until the farthest limits of the forest are represented by a few
low pines set at wide intervals. A tension between the prairie
and the forest is evident. It is also evident that the forest is
gradually replacing the grasses. Here the pine leads the way
followed closely by the Douglas spruce, these two and rarely
other species, Junipcrus scopulorum. The migration is usually
from above downward, but local conditions may vary this and
show a migration from wooded canyons onto the neighboring
prairie. An interesting reversal of the usual course is to be
seen on Wild Horse Island in Flathead Lake. where the forest,
governed apparently by the proximity of the lake waters. became
established first at the foot of the slopes and is gradually oc-
cupying the higher ground.

Owing to local features of the physiography the directions
of the wooded and barren slopes may ke altered. or even re-
versed. The western slopes of the Mission Range, rising from
Flathead Lake are densely wooded and steep. while the opposite
shore. a series of low foothills. is mainly grassland. The evi-
dent explanation here lies in the influence of the lake upon the
moisture content of the westerly winds. The foothills of the
west shore lie in the rain-shadow of the Cabinets. a high range
to the west. Narrow valleys or canyons extending north and
south and transverse to the direction of the west winds some-
times show the western slope more heavily wooded than the
eastern. This fact is due, apparently. to the protection from the
desiccating influence of the westerly winds afforded by the
mountain opposite and the normally higher temperature of a
western exposure. In the vicinity of Haugan, near the western
boundary of the State, the dry exposures are distinctly north-
eastern. This locality was once heavily forested but many years
ago was denuded by fire. A series of slopes here shows a sharp
contrast between the southwestern and western exposures which
were, at the time of the observatien, in 1910, producing a sturdy

THE FOOTHILL VEGETATION 103

young growth of Pseudotsuga tarifolia, Larix occidentalis and
Pinus mouticola, and the northeastern slopes on which no re-
forestation had taken place, but which were occupied by a low
and scattering stand of Ceanothus velutinus.

That the slopes at Hangan were originally forested by the
slow process of conyuest which seems to be the rule where the
pines invade the prairie is of course impossible to say, but that
transitions occur from the grassland to an open pine forest, and
then to the full occupation by Douglas spruce, larch and other
species, has heen pointed out in the case of the forests of the
Flathead Valley (73), and apparently is of common occurrence
elsewhere.

The severity of the conditions on an exposed western slope
is not at first evident. Such slopes are usually covered with
tall waving bunchgrass. Agropyron spicatum, and a host of
herbaceous, plants mostly perennials, among which the following
are conspicuous:

Balsamorrhiza sagittata Cogswellia macrocarpa
Senecio canus Cogswellia simpler
Monarda menthaefolia Pentstemon Wilcoxrii
Delphiniwum bicolor Arabis Nuttall
Zygadenus venenosus Comandra pallida
Mertensia oblongifolia Woodsia scopulina
Cogswellia montana Selaginella densa
Achillea lanulosa Lupinus ornatus

Clarkia pulchella

The active vegetative period of most of these plants comes
early in the season before the rains have ceased, and by the
middle or the end of July they have finished fruiting. The test
of the season comes during July and August, when scant pre-
cipitation, high temperatures, clear skies and dry winds draw
from the thin soil almost its last vestige of moisture. Such con-
ditions are impossible for forest trees, except where the seedling
is sheltered in the lee of some rock or in the bottom of a gully.
Now and then on such slopes a single yellow pine has rooted and
grown to large size where one chance in millions has placed a
seed in favorable conditions.

A series of experimental operations conducted to determine
the practicability of forest planting on sites of this character,

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SUBARU ot oO prods sunwopndoos snaadiun py
! J TCAT, / LUN [

104

THE FOOTHILL VEGETATION 105

indicate something of the severity of the conditions involved.
Three situations were chosen on the grassy slope of a mountain
facing the west and southwest. One of these by reason of a
slight depression and less direct exposure to the sun was con-
sidered more favorable than the others; the other two areas,
lying on a steep and rocky slope directly facing the southwest,
were regarded as exceptionally severe. Upon these areas plant-
ings were made in three successive seasons (1910-1912) with
considerable numbers of yellow pines, both seedlings and trans-
plants one or two years old. Unusual conditions in the form of
drouth and fire at first beset the efforts, but in the end, owing
to circumstances attending the planting and a season more than
usually favorable, ‘the plantations weathered the first summer
with about 25% of the trees surviving.

It was thought that the main difficulty besetting either
natural or artificial afforestation was the establishment of the
seedling, and that if the first season could be sutvived they
might maintain themselves indefinitely. Such, however, seems
not to be the case, for in these experiments the number surviv-
ing waned rapidly from year to year until none were left. The
stems and leaves eventually turned dry and crisp, and, inasmuch
as the planted seedlings could be clearly identified, any conclu-
sion that they had been destroyed by other agencies was obviated.

Growth, as usual under such circumstances, was slow. Even
the plants that survived two years or more grew a scant inch
or more of stem and a few dwarfed leaves while those of the
same stock remaining in the nursery increased by several vig-
orous inches and a full brush of healthy leaves.

Seeding operations were even less successful, as was expect-
ed. Several variations of method gave uniformly negative re-
sults. The difficulties that beset natural seeding are largely
present in artificial methods and that forest extension over grass-
lands by natural means is exceedingly slow is generally true and
a matter of common knowledge. Along the tension line of yellow
pine forest and bunch-grass prairie of western Montana the
direction and rate of transition is evident in the scattered pines
successively younger and more sparse from the forest outward.

It would hardly he safe to say that successful forestation
of such areas with Pinus ponderosa is impossible, but the fail-

106 FOREST DISTRIBUTION

ures attending the above experiments indicate something of the
hazards involved., Of all native species of forest trees the yellow
pine undoubtedly is the most capable of surviving in such situ-
ations, from the standpoint of its water requirements, but in
addition to this we may consider also the fact of considerable
amounts of seed produced, their high percentage of germina-
tion and the facility with which they are sown by the wind.
Millions of seeds must be produced for every tree that shows its
head above the herbaceous vegetation, and such are very few.
These soils absorb practically all the rain that falls, except what
is lost by evaporation from the surface of plants. There is
rarely any run-off. The soil is porous and stony and absorbs
quickly any rain that may fall wpon it. :

In the invasion of the grassland the constant companion
of the yellow pine is the Douglas spruce (Pseudotsuga taxifolia).
No more adaptable species is to be found among the forest trees
in the northwest. Partial as it is to abundant moisture, never-
theless it resists almost as much drouth as the pine, and grows
to large size, albeit more slowly than elsewhere. It is this spe-
cies which more than anv other marks the transition from the
open yellow pine to the mesophytic or near-mesophytic forest.
On account of its greater tolerance it is capable of supplanting
the pine. Jn these situation, however, it is slow to develope
density and grows with the pine in an orchard-like stand and
not crowded, as its habit is on more favorable ground.

The western yellow pine and Douglas spruce are, however,
characteristic of the semi-arid zones and belts of irregular form
and determined by elevation, exposure, precipitation and wind
in the tension zone between woodland and prairie. On the Mis-
souri drainage they often occur associated with Juniperus scopu-
lorum, either on the foothills or along the rim-rock bordering
the benches on the Yellowstone and other streams far out into
the plains. Of the two species the yellow pine has a little the
best of the struggle as the pioneer in the invasion of the grass-
land, but owing to its intolerance, is at a decided disadvantage
in competing with the Douglas spruce in the better watered soils.

One of the most striking features of the forests at middle
elevations, especially on the western face of the divide is the
strong influence of topography in the matter of forest distri-

THE FOOTHILL VEGETATION 107

bution. South and southwest slopes are usually grassy, or
covered with an open forest of yellow pine and Douglas spruce,
the former the more abundant. The northern and eastern slopes
usually bear heavy forests in which Douglas spruce prevails, or
in which larch is locally strong sometimes over considerable
areas.

The difference between opposite slopes is a common and
striking phenomenon over wide ranges of landscape and con-
cerns mainly the vellow pine and Douglas spruce. That this
is a reaction to soil moisture would seem to be evident. Experi-
mental operations, however, do not wholly support this view.
Soil samples taken from the depth of a foot at five different
stations on each of two slopes for comparison, the one facing
north, the other south, were placed in glass stoppered bottles
and removed to the laboratory. This was at the close of a rain-
less period of three months. By the removal of the stoppers
they were allowed to become air dry. After a lapse of several
weeks the samples from the slope facing the north had lost an
average of 3.0% of their original weights; those from the oppo-
site slope had lost 2.5% of their original weights. The samples
were then kept for three weeks in an oven at a temperature of
120 degrees C. At the conclusion of this period the samples of
the former lot had lost an additional .9% and of the latter .8%.
The total loss therefore. in terms of the original weight, was
3.9% from soil of the northern and 3.3% from soil of the south-
ern exposure. There was a difference therefore of only .6%
in moisture between the two series. The southern exposure
presented the usual open yellow pine forest with almost bare
soil; the other bore a dense cover of young Douglas spruce and
larch with ground cover of mosses and other small plants. Com-
parisons were also made on a series of soil samples from the
level gravelly plain and an open treeless slope, covered with
grasses and other plants, according to the same methods and
subject to the same conditions. The former showed a total
water content of 1.9%, the latter 4.3%.

While the evidence from soil examinations is not so con-
vineing as one might expect, the data are too meager to justify
conclusions. It may be expected that the longer the period of
drouth the more closely will the different sites approach uni-

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-pijod miyundg punoadotoy oy, UL “VUE qUOTY ‘oUOIS[OE AvoU TpoyspossnyY ayy Fuope yup oquing ep Fy

108

THE FOOTHILL VEGETATION 109

formity in the percentages of soil moisture. It is obvious also
that the water supply in soils is depleted by absorption and
transpiration, which may in large measure account for the dry-
ness of the soil on the more heavily wooded slope.

The yellow pine seldom favors the steeper north slopes,
even where space is available, except upon outjutting promon-
tories or elevations, which seems to indicate certain relations to
light or temperature. Experimental operations show that the
yellow pine grows more rapidly, on the whole, exposed to full
light at Missoula than it does under half shade, while the reverse
is true of the Douglas spruce.

It has been suggested above that the study of distributional
problems should be approached from the standpoint of the nature
of the species, rather than from the standpoint of the external
factors. Ecological literature has usually been concerned more
with the effect of climatic and other factors upon the vegeta-
tion as a whole on a given area and for the most part has neg-
lected the critical examination of the specific qualities which
identify the important species. From this point of view phy-
sical data is none the less necessary, but each species is a complex
entity which reacts to its environment in its own way. Each has
its individuality and the study of that individuality, the specific
reactions to light, temperature, moisture, ett., efficiency in seed
bearing, periods of fruiting, immunities and the like, in short
the sum total of its resistance and response, must throw light
upon the nature of the plant and the conditions of its distribu-
tion. Every species is a complex of positive and negative quali-
ties, the positive qualities those that are advantageous, the nega-
tive those that are disadvantageous. The balance of these
qualities may show an excess for or against the species, and
this balance will be found to be proportional as a rule
to its geographic range and abundance. The negative
qualities are limiting factors in its distribution, the positive
make for dispersal. The more stringent the limitations the
more cireumscribed the distribution locally and generally, al-
though in the latter aspect the limits of geographic range are
not due to the lack of similar and suitable conditions elsewhere,
so much as to the more effective action of intervening barriers.
These conelusions, it is thought, will be supported by reference

110 FOREST DISTRIBUTION

to the particular species which occur in this region.

The three species which oceur most commonly in the foot-
hill regions of Montana are the vellow pine, the Douglas spruce
and the Rocky Mountain juniper. Taking first the case of
the pine certain highly important positive qualities may be
pointed out. This species produces abundant seed amply winged
for distribution by the wind and with high percentage of via-
bility. The moisture requirement both as to soil and air is
relatively very low, within its range it is subject to a tempera-
ture range of at least 180 degrees. and it will grow on soils of
widely differing texture and composition. Add to these quali-
ties that of immunity to most diseases and, on account of its
thick bark, to ground fires of ordinary intensity, and also the
general vigor and robust habit of the tree. and it appears that
the yellow pine is equipped with an unusual number of impor-
tant positive qualities which make for extension and survival.
The only serious limiting factor which seems to militate against
its success is its intolerance of shade. Owing to this weakness
it is largely excluded from moister soils suited to the more vig-
orous and rapid development of its bulk, and eventually suc-
cumbs in the gradual march of succession to the more tolerant
species which compose the climax forest. From the point of
view here advanced ‘it is this combination of positive qualities
which accounts largely for the wide distribution of the species
over most of the western half of North America and its common
occurrence in most places within its range.

The Douglas spruce offers a similar case. Its seed bearing
capacity is large and the light seeds are readily carried by winds
to considerable distances and show a high degree of viability.
It is a tree of vigorous growth up to maturity and has the added
advantage of greater tolerance than the pine. in favorable sit-
uations forming dense stands to the exclusion of almost every
other green plant. This species also resists as wide a range of
temperature as the pine. and seems impartial as to most soils.
Toward maturity the tree is largely resistant to slight fires. In
its moisture demands, however, it is slightly less resistant than the
yellow pine. While a close second to the pine in the tension
line between prairie and forest, yet the Douglas spruce more
readily shows the effect of adverse condition in diminished

THE FOOTHILL VEGETATION 111

growth. The species has a wide range of adaptability. While
it grows with the greatest luxuriance in the region. of heavy
rainfall west of the Cascades it also occupies the outposts of
forest vegetation bordering the dry prairies in the Rocky Moun-
tains and adjacent plains. In the latter situations, however,
its inferior size and form indicate the hardships to which it is
subject. In another way also is it inferior to the pine in the
Rocky Mountain region where it succumbs frequently to the
attacks of Razoumofskya Douglasii. As these negative qualities
are only relatively of importance, the Douglas spruce is remark-
ably well fitted for successful competition and becomes locally
here and there in the Rockies, and far more extensively farther
west, the dominant species. Its geographic range is greater
than that of the western yellow pine.

The extensive distribution of Juniperus scopulorum, an-
other of the Transition, or foothill species, seems largely to be
the result of its rugged adaptability to adverse soil conditions,
both as to moisture and other qualities, and to the effective
means of the distribution of its seeds by birds. It is however,
never abundant to the extent of forming forests, but appears,
in the few places where it is pure, in widely open stands.
This fact is perhaps associated with the relative paucity of its
seeds and to its exceedingly slow growth. It is nevertheless a
species resistent to a wide range of temperature and apparently
suited to many different soils.

It is quite evident that the grassy slopes of this region have
not been forested since pre-glacial times. The condition about
Missoula furnishes an interesting study in this particular. The
city is built upon a gravel plain at one time the bed of a sup-
posedly Pleistocene lake; on all sides to the hight of 1,000 feet
above the city are clearly marked shore lines of the ancient
sea. For miles these may he traced horizontally and they mount
one above another in a close succession of slight undulations.

The lines of these shore terraces lie chiefly in loose materials,
gravels, soils or broken rock. In view of the effects of large
roots upon such materials and the minor displacements con-
sequent in the course of time, it seems impossible that forests
could ever have occupied these slopes without obliterating the

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quadssoroqae oy, Jo Juotd Ay, MOAN TPoyspossnypy oy] JO spuvpuroyjoq oy, uo Npuahuwg snyndog "OL Att

THE FOOTHILL VEGETATION 113

sharp definition of the shore lines or at least interrupting their
continuity.

Some of the foothills are morainal in character, and where
unsheltered, support only the herbaceous prairie flora. The
higher slopes show numerous outcroppings of the country rock,
such as may be found in all stages of disintegration, from jutting
bluffs to mere mounds, and usually with more of less exposed
talus below. It is significant that such outcroppings, if not too
bold, and much of the older talus, is occupied by deciduous
shrubs:

Amelanchier alnifolia Opulaster malvaceus
Philadelphus Lewisti Rosa Woodsti

Ribes cereum Acer glabrum
Prunus demissa

The species which occupy such situations, it appears, may
be for the most part those which are plentiful in the region, and
not especially xerophytie forms. Some places are occupied by
Populus tremuloides, which may occur here and there as small
islands, sometimes on high grassy and otherwise treeless slopes.
On the east and west forks of the Bitter Root the southern slopes,
erassy and treeless over considerable areas, support in patches
serubby growth of Cercocarpus ledifolius. Over a whole moun-
tain side the rock outcrops may be located at a distance by the
gray bunches of the mountain mahogany. It clings to the faces
of cliffs and seemingly in the most severe and inaccessible places.

This obvious feature of the distribution of deciduous shrubs
over a slope otherwise unfavorable can have but one meaning
and that is the locally greater supply of available moisture.
Competition of grasses and other plants over most of the area
may operate toward exclusion by withdrawing too much water
from the soil, but not by the density of the stand, for there is
always sufficient space for many more plants than are actually
to be found in the sparse and open stand of the bunch grass.
The shrubs above mentioned are often seen aligned up and down
-the slope in drainage channels so shallow as hardly to be notice-
able, but apparently supplying the roots from a source hidden
under the coarse fragments which compose the surface of the
talus.

114 FOREST DISTRIBUTION
THE ‘“‘SLwe Rock’’ SUCCESSION.

One feature which is noticeable in the topography alike
toward all points of the compass are the rock fields which com-
pose extensive slopes of talus and are known as ‘‘rock slides’’
or ‘‘slide-rock’’ Such areas consist of rock fragments mostly
under a foot in diameter. The succession of vegetation on these
areas is a matter of much interest and importance. As might
be expected the rate of development varies much with the ex-
posure.

One of these areas which faces the south in Hellgate Can-
yon a mile east of Missoula, offers considerable difficulty from
the standpoint of vegetation. This slope which rises at an angle
of about 40 degrees is one of the older slide rock areas since the
cliffs which formed it no longer are evident and the talus merges
smoothly into the grassy slope above. Viewed from a distance
the shallow channels of occasional drainage are evident and these
have been preempted by Rihes cereum, Philadelphus Lewisii and
Amelanchier alnifolia, which extend up and down the slope in
bushy, hedge-like rows. In about half a mile of this slope one
may count a score of Douglas spruce trees. old and misshapen.
-\ slightly greater number of yellow pines, and an equal num-
ber of smaller trees of each species, ten feet in height or less.
None of these occur above the line of the slide-rock. Upon
closer inspection one finds old stumps of former large trees of
200 to 250 years of age. The larger living trees probably vary
from 75 to 200 vears of age. There is immediate evidence that
on this area of approximately 30 acres there have been seed-
bearing trees for fully 200 years. yet the total stand of pine and
Douglas spruce combined numbers less than 100 trees. while the
number of young seedlings number a scant two score, the progeny
of about fifty seed-bearing trees.

The fragments of the talus, at first gray. soon become spotted
with minute lichen growth which finally covers the surface with
a coating almost black. Most of these lichens are close encrust-
ing forms without even so much as a foliaveous margin of the
thallus. This change proceeds slowly, and much more slowly
on the southern than on the northern exposures. In the case
now under discussion considerable parts of the rock slope are

\

THE ‘‘SLIDE ROCK’’ SUCCESSION 11d

still as bare as when first formed. Elsewhere, however, espe-
cially on more favored exposures the slide-rock has become cov-
ered with dark lichens and has at a distance the appearance of
coal.

Where a trace of soil comes into the talus, wind blown or
washed, it supports the following plants:

Agropyron spicatum Balsamorrhiza sagittata
Clarkia pulchella Delphinium bicolor
Leptotaenia multifida Achillea lanulosa
Pentstemon Wilcoxii Woodsia scopulina

Artemisia frigida

The forests of the northern and eastern slopes are subject
to an entirely different set of conditions. Long after the snow
is gone from the southern and western exposures it lies in deep
drifts on the opposite slopes. Instead of .an almost vertical sun
as on the former the latter exposure may receive very little
direct illumination. It is sheltered from the prevailing winds.
As a result of these conditions, the ground water is fairly plen-
tiful and lasts later into the season. These conditions are usually
favorable in many places for a near-mesophytiec vegetation in
contrast to the xerophytic on the opposing slope.

As typical of conditions over a large part of western Mon-
tana, the principal discussion will deal with the south wall of
Hellgate Canyon just opposite and distant about a quarter of a
mile from the slope described above. This slope, of about
the same angle, has several outstanding crags, and rugged ridges
extending up and down the north slope. Between these ridges
are depressions occupied to a large extent by steep and extensive
areas of unstable talus.

The forest of the north slope is mainly Douglas spruce and
western larch. Yellow pine does not amount to so much as one
hundredth part of the stand, and is found chiefly on the tops
of the ridges and at higher elevations where it approaches the
crest of the ridge toward the southern exposure. This undoubt-
edly is due to its demand for light. In a few places on the
higher slope are thickets of lodgepole (Pinus contorta) and here
and there a Rocky Mountain juniper (J. scopulorum).

The tops of the ridges extending up and down the slope are
occupied by the oldest and largest trees, chiefly Douglas spruce

uO “YAsaoyp avou vonnjh voong "Ly “AtyT

116

THE ‘‘SLIDE ROCK’’ SUCCESSION 117

and yellow pine. In some places their sides are occupied by
mature larch. The rest of these ridges are open and grassy
and show evidence of seasonal drouth. Among the grasses
(mostly Agropyron) may be found Sieversia ciliata, Zygadenus
venenosus, Selaginella densa and Arctostaphylos Uva-ursi. Such
conditions are impossible for the larch which seeks the moister
situations.

The depressions between the vertical ridges are occupied
by lesser vegetation in various stages of development. The slide-
rock is thoroughly covered with encrusting lichens. When suf-
ficient hold is provided for mosses these appear, along with the
more foliaceous type of lichens.

The first of the mosses to take hold on the exposed rock
surface is Grimmia pulvinata. Its dark cushion-like growths
accumulate sand, dust and vegetable matter, and ultimately fur-
nish a foothold for other small plants.

Places are found in which Dicranwm congestum fills in
between the rock fragments or wholly overgrows them. Woodsia
scopulina is evident and an occasional Sedum stenopctalum and
Heuchera glabeila. At certain points shrubs become established
and among these may be observed Philadelphus Lewisii, Amelan-
chier alnifolia, Opulaster maluaceus, Ribes cereum, R. saximon-
tanum, Rubus parviflorus, R. strigosus and others. It is inter-
esting to note the extent to which some of the more favored slopes
have become forested. Considerable areas have become covered
with a stand of vigorous Douglas spruce about 30 years of age.
The trees number as high as 3000 to the acre and so dense is the
canopy of their foliage that but few plants and these the most
tolerant find sufficient light to support life. Digging away the
thin cover of leaf mould one soon uncovers just such rock frag-
ments as form the usual talus.

Elsewhere on the slope the stand may be practically pure
young larch, or with some mingling of Douglas spruce. The
extent to which the larch is dependent upon the ground water
is beautifully exemplified in places on this slope. Long drifts
of snow may be seen at the end of March ar early in April lying
in the shallow drainage channels and rising out of the drifts
are thickets of larch of various ages from small saplings to large

118 FOREST DISTRIBUTION

trees. One of these belts is not more than 15 feet wide and
extends down the slope for some hundreds of yards.

The same history of the slid« rock has been observed in
many places and the character o* its vegetation man be corre-
lated with that prevailing iv the locality and with the direction
of exposure. The identity of its vegetation varies with the alti-
tude and geographic position but the course of events is usually
the same, the lichen crust, the mosses of the Grimmia type, the
herbs, the shrubby vegetation and eventually the forest or the
prairie, according to exposure and climatic conditions.

Tue WESTERN VALLEYS.

Whitford has described the mesophytic type of forest
of the Flathead Valley as characterized mainly by the pres-
ence of Douglas spruce and western larch but including also
Pinus contorta, P. menticola, Abies grandis, Thuja plicata
and Picca Engelmannii. It would seem, however. as indic-
ative of the purely mesophytic type, that the species which
should be taken as characteristic are Pinus monticola, Abies
grandis, Tsuga heterophylla, and Thuja plicata. These species
are almost invariably, associated with one another in this region
and forests containing them are not only of restricted distri-
bution in Montana, but also are marked by other more or less
distinctive species among the lesser forest plants. This group
will be considered later.

While the Douglas spruce and vellow pine are frequent
companions on the southward mountain slopes. the former on
the northern slopes in western Montana is frequently associated
with the western larch. The mixture of the two species obtains
only under the better watered conditions and diminishing the
quantity of larch and increasing that of Douglas spruce even
to a pure stand. in the direction of the drier situations. On the
other hand the larch sometimes attains pure stands on the cooler
and better watered slopes.

The western larch (L. occidentalis) has several distinctive
characteristics. Certain positive qualities stand out conspicu-
ously and certain negative ones are no less prominent. The posi-
tive factors in the organization of this species may bé summed

THE WESTERN VALLEYS 119

up briefly as follows: The trees begin early to bear seeds and
produce them in abundance throughout a long life. The seeds
are small and light, and provided with ample wings by which
they are carried far by the wind. In addition to these quali-
ties they retain- their viability well and usually show a good
germination percentage. When once started the seedlings grow
rapidly in height, a feature in which they excel most other
species. With age the tree acquires a thick bark which serves
it well as a protection from ground fires.

The negative or limiting qualities are seen in the intolerance
of the larch to shade, in its rigid demands upon soil moisture, its
partiality to cooler climates and its marked susceptibility to
<dlisease.

The strong points of the larch are in its seeding habits, and
its rapid early growth. The significance of the positive factors
is especially evident in local distribution. The seeding ability
of the tree often enables it to occupy limited areas exclusively,
but such areas are bounded by the special properties of the soil
from the moisture standpoint. The temperature relations of
the species are such that its most southerly extension in the
Rocky Mountains occurs in Montana, and it doubtless is found
farther south than it otherwise might be were it not for the
topographical conditions which provide suitable situations on
northern slopes. While the western larch endures a considerable
diurnal range of temperature, it is distinctly a tree of the cooler
regions. It is one of the principal trees of the Kootenai Valley,
where the annual range of temperature may be from -40 to 108;
the days of summer may be hot, but the nights usually are cool
and frosts occur in all months of the vear.

The rapidity of its early growth in height is probably the
most important of all its qualities in competiticn with other
species. Under good conditions trecs make a growth of 4 feet
in + years while under the same conditions Douglas spruce gains
a height of about 20 inches, vellow pine about the same and
Engelmann spruce less than a foot. Thus if given an equal
chance, or even somewhat less. thé larch will soon be so far above
its neighbors as to be out of all danger from shading. Engel-
mann spruce sometimes forms forests so dense that nothing can
grow beneath their crowns, yet in just such forests one may

BI

YION MOATYT

“AUIN §

120

THE WESTERN VALLEYS 121

sometimes find two stories, the upper consisting of the crowns
of the vigorous larch, the lower a uniform stand of spruce. If
it were not for the relative growth in height of the two species
such a mixed stand. would be impossible.

The larch is severely subject to the attacks of Trametes pini,
but even so may continue to live for years with ever diminishing
increment of growth, before the stem finally gives way. Other
fungi are likewise parasitic on the larch but they apparently are
less serious in their effects, and.the mistletoe, Razoumofskya
laricis, is in some localities very troublesome.

One of the most significant of the forest societies of
western Montana is that furnished by the white pine (Pinus mon-
ticola) and its associates. Some of the species often associated
are Abics grandis, Tsuga heterophylla, Thuja plicata, Taxus
brevifolia, Betula papyrifera, Populus trichocarpa, Lonicera in-
volucrata, Lonicera cilosa, Lysichiton Kamtschatcensis, Acer gla-
brum, Holodiscus ariaefolius, Ceanothus sanguineus, and Linnaca
borealis. Two forms of parasitic fungi are usually prevalent.
Trametes pint and Echinodontium tinctorium, the former at-
tacking the white pine, Douglas spruce, larch and some other
species, the latter found almost exclusively on the hemlock and
fir.

The aspect of the forest is strongly mesophytic. Tender
leafy plants of more or less delicate structure, suited to a humid
forest and moist soil,.evidence in all species of rapid and vig-
orous growth, and the attainment of extraordinary size, all point
to conditions exceptionally favorable. Acer glabrum elsewhere
a shrub of ten or fifteen feet, here becomes a tree, 30 feet or
more in height and in diameter 8 or 10 inches. The white
pine itself may attain 7 feet in diameter, the black cottonwood
(P. trichocarpa) 3 to 4 feet, the hemlocks 2 to 3 feet, and
other trees more or less. The forest floor is usually covered
with a litter of branches and leaves among fallen logs, support-
ing a growth of mosses and liverworts, while fleshy fungi of
many genera and species abound. Among the small plants may
also be found Pyrola aphylla, Pterospora Andromeda, Monotropa
uniflora, and Corallorrhiza multiflora and other orchids and
plants more or less mycotrophic in habit.

Forests of this sort are limited to relatively small areas in

‘ds pistmay.cpy pur vypqo/ap snyy “yuoy, Sotavpy avou odors yyNoG "GEL “Lyf

THE WESTERN VALLEYS 123

this region. They are largely localized and may be separated
or surrounded by tracts in which far different conditions obtain.
They are found in the valleys and canyons and on the lower
slopes of the Flathead drainage, in parts of the Kootenai Valley,
and in the northern part of the Bitter Root Range between Mon-
tana and Idaho. .They are found at their best, as far as the
writer’s observations have extended, in the valley of the Swan
River, and some other tributaries of the Flathead, where they
diminish and merge into the drier land formations southward
along the east side of Flathead Lake, and in the valley of the
Priest River in northern Idaho. In Glacier Park they are to
be found in Avalanche Basin, and the valley of McDonald Creek
and in other places west of the Continental Divide. The best
forests of the Flathead are along the upper courses of its main
branches and their many tributaries among mountains and in
narrow gorges; the river in its lower course enters the open coun-
try where the mesophytic forests gradually yield to more and
more xerophytic types. Very little is seen of Pinus monticola
and its associates below the upper end of Flathead Lake until
the slopes of the Bitter Root are reached. The western slopes
of this range and the neighboring country of the St. Joe and the
Clearwater of Idaho are covered by some of the best of the white
pine forests of the northern Rocky Mountain region and this
species and some of its associates have crossed to the eastern
slope and descended into the valley of the St. Regis and other
tributaries of the Clark’s Fork. All of this section of Montana
from the Kootenai to the St. Regis occupies but a corner in the
northwestern part of the state.

Some discussion of the leading species in the white pine
forest may now be appropriate. The white pine as the most
characteristic element will be taken first. Its salient features
may be summed up as follows:

The seeds are well adapted to wind dispersal. The trees
show considerable tolerance while young and grow rapidly in
height. The species seems impartial as to structure and com-
position of the soil. The above are the positive qualities. Op-
posed to these are the facts that seeds are produced sparingly
and rarely if at all until the trees are 40 to 60 years of age. The
seeds germinate slowly, have low percentage of germination and

UOT SAtAuPE aAvou sureyd oyy uo (wurqnogy

“c) sywjuonsoy sniodiunpe “06 “FtyT

THE WESTERN VALLEYS 125

transient viability. The demands of the species are exacting as
to soil and atmospheric moisture, and the temperature range
seems normally to lie between -40 and 100 degrees. The trees
are very susceptible to disease and are easily killed by fire.

Thus it will be seen that the negative or limiting factors
predominate. Among the positive silvicultural characteristics
two only are of much significance as far as competition is con-
cerned, viz., the rate of growth and tolerance in early years.
These two qualities alone enable the white pine to compete ad-
vantageously with all other native forest species and to outstrip
many of them in growth. They enable them to enter stands
of older trees which are beginning to open as they approach
maturity. The importance of these qualities becomes the more
apparent when we consider the nature of the species with which
the white pine is called upon to compete. The hemlock and
grand fir are both very tolerant of shade and may grow in dense
stands though such are not frequent in this region. The Doug-
las spruce, arbor vitae, larch and even lodgepole pine may appear
along with the white pine in the same situation and in competition
with it. All of the usual competitors except the fir are vigorous
producers of seed and hence of special importance in the com.
petitive struggle.

On the whole the white pine can scarcely be said to be for-
tunate in its seeding habits. The percentage-of germinable
seed has been shown to vary, according to the size of the cones,
from 15 to 90, but mostly 50 or less. The seeds are sought as
food by various animals. Moreover the germination response
is slow and the seeds may lie even in well tended nursery beds
for a year before germination. It is difficult to see, in the com-
plex of influences to which all plants are subject, how any ad-
vantage accrues to the tree by such a habit, in view of the fact
that such delay may increase the chances for destruction by ani-
mals and by decay, and enhance the advantage to other species
by increasing their lead in the race. It has also been learned
that little seed is produced unless the crowns are well lighted,
which indicates that competition is directly responsible for a
large reduction in the seed crop. (75.)

An element of weakness in the white pine is its susceptibility to
disease, especially to the attacks of Trametes pini. Whole stands

“AU “DSOL0p
-uod snug punoadyonq oy, up ‘punoa®oaoy oy. ut mnsopndoos snuodiunp “yuo Saoppnog, AVON "16 “FLT

126

THE WESTERN VALLEYS 127

of fine timber are in places so seriously affected as to make it
difficult to find a sound tree.

The importance of this disease appears not only in the de-
preciation of the wood for commercial purposes but also in the
shortening of the life of the tree and the lessening of its repro-
ductive vigor. The tree is also subject to serious attacks by
the bark beetle, Dendroctonus monticolae, and owing to the thin-
ness of its bark is readily injured by ground fires.

All of these factors are then very potent influences in keep-
ing the tree within narrow geographic bounds and ordinarily
below a medium point numerically over areas which are capable
of supporting it. In Montana it is confined to the west side of
the Continental Divide. It doubtless reaches its most
southern limit in the Rocky Mountains in the Bitter Root range
between Montana and Idaho, possibly as far south as Nez Perce
Pass, at the head of the West Fork of the Bitter Root, and mostly
on the western or Clearwater slopes.

The grand fir (Abies grandis) is nowhere in Montana a com-
mon tree. Even in the mesophytie forest to which it properly
belongs it is seldom conspicuous and it grows in poor form and
only to medium size, as compared with the sometimes pure stands
of fine, large trees to- be found here and there west of the Cas.
eades. The salient qualities of this tree may be set forth as fol-
lows: As to its positive characteristics, the grand fir grows
rapidly while young and has a considerable capacity to resist
shade. It appears not to be particular as to soil composition or
structure. The seeds are light and amply winged. On the
other hand it is not given to early fruitage in the Rocky Moun-
tains, and its seeds have transient vitality and low germi-
native capacity. It is not at any time prolific in the bearing of
seeds. The species is exacting in its moisture requirements and
its temperature range is rather narrow. In addition to these
traits the tree is susceptible to disease and is easily injured by
fire.

Like the white pine the grand fir wins in competition mainly
by reason of its tolerance and rate of increase in height. The
early production of seed is a mark of some advantage in the
most favored parts of its range, but in the less favorable region
of the Rocky Mountains even this feature disappears. The seeds

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AOMO'T ‘punoadspouq Juuysip oy) ul vsotspuod snurg “WoW “eyNossty Avou adojs udaysom Yo ee “ALT

THE WESTERN VALLEYS 129

being low in vitality and germination are a means of slow and
uncertain reproduction.

The grand fir is impartial to soils as to structure and compo-
sition, provided they are sufficiently moist. It is usually found
on bottom lands or in places where the soil is likely never to be
dry. Even under the favorable conditions which usually pre-
vail over most of the country west of the Cascades, this fir is
usually found on river banks or in the bottoms of canyons, where
it reaches large dimensions. In western Montana the relation
to soil moisture is even more strongly emphasized.

The grand fir seems to demand on the whole a higher tem-
perature than the white pine. Its lower limit is about -30 de-
grees while its upper range is some degrees above the maximum
commonly understood for white pine, or somewhat over 100 de-
grees. In Oregon this species thrives at sea level while the white
pine seldom appears there below 3000 feet.

Fire injury in this species is seldom an important matter
as the local conditions on river bottoms and similar places are
not often such as to invite it. The matter of disease, except
for Hchinodontium tinctorium, is not apparently a serious one.

The control of distribution in this species, therefore, must
be largely topographic, with reference to the amount of soil mois-
ture, and on areas which are favorable its size and numbers are
determined by competition.

The hemlock (Tsuga heterophylla) affords another example
of a conifer of mesophytic requirements. In fact it is much more
restricted in its local distribution than the grand fir. Its range
in western Montana is confined to localities in the northwestern
part of the State, in the valleys of the Swan River, the Flathead
and the Kootenai. It is found in the valley of McDonald Creek
in Glacier Park, and a stand of trees unusually large for this
region occurs in Avalanche Basin, tributary to the same stream.

In its positive qualities the hemlock is particularly fortunate,
These pertain to two features, its seeding habits and light rela-
tions. Abundant.seeds are produced, which have a high germ-
inative capacity and the ability to thrive on the humus cover
and litter of the forest floor. The seeds, being ight and with
ample wings, may be carried well by an ordinary breeze. The
hemlock is very tolerant of shade and is of fairly rapid growth.

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SHUT

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1:

THE WESTERN VALLEYS 131

Negatively the species demands abundance of moisture in
soil and air, its temperature limits are relatively narrow, lying be-
tween about -35 degrees and 95 degrees in this region. It is easily
damaged by fire and is moderately susceptible to disease.

The positive qualities of this species are practically confined
to two things of particular importance, viz: the seeding habits
and tolerance. The hemlock is especially fortunate in both; in
the former as providing a great number of individuals in the
competition for space, in the latter as successfully opposing the
suppressing influence of other species. These are important ele-
ments within the suitable areas, but so important in the economy
-of this tree is the constant presence of a considerable amount of
soil moisture, that this factor alone is of sufficient weight to
over-balance all other considerations in local distribution. No
more definite mark of the nature of the tree in this regard can
be found than the habits of the root system, which spreads in
all its complex ramifications at the verv surface of the soil.
Often the roots extend for fifteen feet or more on all sides of
the tree just under the layers of forest moss and mould and are
more than half exposed when a chance ground fire consumes the
combustible material. In such cases, of course, the tree is killed
and this constitutes another of the limiting influences which
affect the prosperity of the species. Thousands of seedlings of
the hcmlIcck establish themselves upon fallen logs, boulders,
stumps, etc., wherever mosses and fallen leaves furnish some
check to evaporation, and under such conditions they may flour-
ish to maturity. It is not unusual in hemlock woods to find old
trees with roots astride a low and reaching down to the ground
on either side. Sometimes under such conditions the young
seedlings form a veritable carpet. The behavior of the hemlock
in these respects, however, is possible only under the most favor-
able conditions of atmospheric and soil moisture.

The western hemlock is not especially susceptible to dis-
ease except in the case of Echinodontium tinctorium, by which
it is often seriously affected or destroyed.

One other tree of importance remains to be discussed as a
member of the mesophytic forest. The arbor vitae (Thuja
plicata) is frequently conspicuous, and is somewhat more widely
distributed than the two preceding species, though sharing to a

Fig. 24. Southern slope in the Lolo Valley. Pseudotsuga and

Pinus ponde rosa. Chrysothamnus nauseosus and

Agropyron spica um
in the foreground. August.

THE WESTERN VALLEYS 133

large degree their preference for distinctly mesophytic situa-
tions. With respect to its particular qualities, the statement may
be made as follows:

The positive elements in the nature of the arbor vitae are
found largely in its seeding habits. The tree produces an
abundance of seed throughout a long life. The seeds show a
high germination response, and find a suitable substratum on
the mossy litter of the moist forest floor. The seeds are the
lightest of any produced by our coniferous species and are easily
distributed. The arbor vitae is very tolerant and is not very
partial as to soils. It is little subject to serious disease.

The principal negative elements in the composition of this
species are its strict moisture requirements, its limited tempera-
ture range, its slow growth in its earliest vears and its suscep-
tibility to injury by fire.

It is evident that the positive qualities of the species out-
number those of a negative character, but the moisture limita-
tions are locally important to a degree sufficient to outweigh
all other considerations. It frequents river bottoms and moist
flats, stream banks, the bottoms of canyons and the borders of
high lakes in the Rocky Mountains, but in the Coast Mountains
of Oregon, where precipitation is ample it occurs plentifully
on mountain tops and stony ridges. In Montana it is found
mostly in the northwestern part of the State and neighboring
regions, and is most aboundant, in the cooler, moisture sections
of the north, as on the flats below Lake McDonald and elsewhere
in the Glacier Park, and the tributaries of the Kootenai. Fine
stands of this tree are pictured by Whitford and Lindgren about
the lakes and in the creek bottoms of the Mission and Clearwater
Mountains. It forms a conspicuous understory in some parts of
the white pine forests of the Priest River Valley where the
writer observed it in 1910. It reaches its best development
within the limits of moderate temperatures where the soil is
perennially moist. The seasonal temperature range must be
usually from about -35 to 100 degrees or more but with the
usual upper limits of summer heat at 85 or 90 degrees.

In the case of the arbor vitae one seldom finds many small
seedlings, such as usually are to be found under hemlocks. The
growth of seedlings at first is very slow, rising to a height of

25. On the East Fork of the Bitter Root. On the left,
slope facing the southeast, Cercocarpus ledifolius; on the right, north-
west exposure, Pinus ponderosa and Pseudotsuga tavifolia. August.

134

THE WESTERN VALLEYS 135

six to ten inches in four years, but accelerating for a time during
later vears. In this respect the tree is at some disadvantage as
compared with other species like the fir and hemlock and is
saved only by its great tolerance of shade. Thus it may con-
tinue for some time under deep shade without suffering sup-
pression. The trees grow to great age and are very tenacious of
life; often with much of the trunk and crown dead a few living
branches may survive indefinitely. There are few parasites
which attack the arbor vitae though owing to its thin bark it
easily suecumbs to fire and the ground which it occupied may
become covered with Douglas spruce or lodgepole pine, or as
appeared in one case, with a dense growth of the more rapidly
growing white pine and grand fir.

Among the mesophytie companions of the white pine men-
tion should be made of the western yew (Taxus brevifolia) while
almost a rare tree in western Montana, it reaches a diameter of
a foot and a height of twenty to thirtv feet, where it occurs
in some of the deep. moist canyons east of Flathead Lake, always
thriving best in the vicinity of permanent water, but forming
a shrubby undergrowth in the shade of old forests. It seldom
is abundant, even locally, which may partly be accounted for
by the paucity of its seeds and the slowness of its growth. Like
some of the other species, however, it may be taken as a good
indicator of the humid qualities of the soil and climate.

The broad-leaved, deciduous element in the forests of this
zone is seldom conspicuous, but along open river bottoms, Pop-
ulus trichocarpa is everywhere the dominant tree, sixty feet or
more in height, three feet or over in diameter, and sometimes
with a clear, cylindrical trunk of 40 feet in length. The sec-
ondary species on the river bottoms are Populus tremuloides,
Alnus tenutfolia, Betula fontinalis, B. papyrifera, Prunus demis-
sa, Crataeyus Douglas, Salix fluviatilis, 8. Bebbiana, 8S. cordata,
and 8. Scouleriana. Betula papyrifera is much more restrict-
ed in its range in Montana than any of the other species and is
confined to the northwestern slopes and valleys, where also the
aspen shows larger and more abundant development, with Cra-
taegus rivularis, Ceanothus sanguineus, Ribes lacustre, Rhamnus
Purshiana, R. alnifolia, Holodiscus ariaefolius, Spirea lucida
and numerous other shrubs. The trees which appear most con-

Bitter Root near Medicine
xposure at an altitude of about

of the

ast Fork
South e

E

A bluff on the
Cercocarpus ledifolius.

6.

2

Fig.

Springs.

st.

Augu

4000 feet.

136

THE MONTANE ZONE 137

spicuous in the mesophytie pine forest, where openings of the
forest permit, are Populis tvichocarpa and Betula papyrifera,
often well shaped trees of unusual size.

The mesophytic forest as discussed above is essentially the
same as the Pacific Coast Humid Transition. It merges by
degrees into the Montane or Canadian forest in northern
Montana at an altitude of near 4,000 feet. The white pine shows
a tendency to ascend the slopes ahead of its usual companions
on the lower levels and so in places becomes identified with the
mountain forests.

THe Montane ZONE.

The forests of the Montane or Canadian zone are not
clearly differentiated from those of the sub-alpine or Hud-
sonian. By reason of the occurrence of some trees more
abundantly at higher altitudes and the restriction of a few
species of herbs and shrubs to the same elevations the areas im-
mediately below the highest peaks and ridges have a physiognomy
more or less their own, but the trees that constitute the bulk
of this so called sub-alpine zone also enter largely into the com-
position of the lower belt, if indeed they do not in some places
constitute it fully. The same species which on high and exposed
sites are depressed and misshapen may form the main stand of
good form and quality a thousand or two thousand feet lower
on the mountain side. The species which form the bulk of the
Canadian forest zone are Pinus contorta, P albicaulis, Picea
Engelmannti and Abies lastocarpa. An examination of Table
20 will show the wide range of vertical distribution of these
species and reference to the tables presented under the discus-
sion of the sections will show that this feature is not confined
to one locality. On the eastern slope of the main Rockies the
limber pine (P. flexilis) has also a large part in the forests of
this zone.

At about 4,000 feet one begins to meet occasional representa-
tives of the higher mountain flora and with mounting altitude
their numbers increase until the level of maximum development
is reached. This level is not the same on different ranges nor
on different peaks of the same range, since the conditions vary.

Fig. 27. South exposure, altitude 4090 feet, upper Bitter Root
Mountains. Open forest of Pinus ponderosa. In the bottom of the
canyon a thick stand of Pseudotsuga taxifolia. August.

138

THE MONTANE ZONE 139

So far as observed, none of the plants seen first on the slope at
4,000 feet or above fail to extend to the sub-alpine zone, some in
sheltered canyons and ravines and others on open and exposed
slopes. Among such may be mentioned:

Yerophyllum Douglasn Menziesia glabella
Veratrum californicum Pachystima Myrsinites
Vaccinium membranaceum

Referring again to the trees of the Montane or middle
mountain belt, the first of the species from the standpoint of
its numbers, its characteristics and the breadth of its distribution
is the lodgepole pine /P. contorta).

The lodgepole forests have been studied by Clements (12)
in Colorado and by Mason (3%) in Montana and elsewhere. From
various standpoints they are of great interest and importance.
They represent a form which is able with remarkable rapidity
to reoceupy denuded land, made possible by prolonged viability
of the seed, by the large numbers of seeds produced and the
facility of their dispersal. The lodgepole represents a species
which by reason of its own power to reproduce is usually pre-
vented from attaining great age and maximum dimensions. The
density of the stands, the resincus character of its tissues, and
the habitats which it often seeks on high and exposed ridges
make lodgepole peculiarly susceptible to fires which often re-
peatedly sweep the same area. During at least the earlier period
of its development the lodgepole stand is often as effective a
barrier to the movements of neighboring species as a lake or a
snowfield, for stands of trees six to eight feet in height may be
so dense as wholly to exclude even the most tolerant of the
lesser green plants. In older stands which have begun to open
there is, however, opportunity for the entrance of competitors
and in some places the white pine may be seen making headway
under the much older growth of the lodgepole. Under conditions
favoring the entrance of other species the lodgepole must ulti-
mately become supplanted. Whitford has found in the forests
of the Flathead Valley the invasion of the lodgepole stand by
white pine, lowland fir, Engelmann spruce and occasionally ar-
bor vitae and western hemlock. If the seeds of western larch,
Douglas spruce, or other species of rapid growth in height are

140

THE MONTANE ZONE 141

sown with the lodgepole these may become the dominant com-
petitors.

The character of a lodgepole stand clearly indicates a wind-
sown forest. Extensive areas are seeded go evenly as to permit
of no alternative explanation although authors above men-
tioned are inclined to question this view. The lightness of the
seed and the amplitude of the wing make possible their trans-
portation by even a moderate gale. The behavior of the lodge-
pole recalls no other species so much as the Douglas spruce,
which with great facility in its most favored regions reoccupies
clear cut slashings and burns many acres in extent with a uni-
form thicket growth propagated from the borders. And the
seeds of the Douglas spruce are heavier than those of the lodge-
pole pine.

The reseeding of a burned area by lodgepole presents no
difficulties if the area has previously been occupied by that
species, even as a partial stand, unless the fire has been so intense
as to consume the tops. The writer recalls that the severe fires,
of 1910 swept a part of the valley of the North Fork of the
Flathead River. The ground cover was entirely consumed and
the crown fire had stripped the leaves from the branches over-
head. Some trees had fallen and among them lodgepoles. Upon
examination, within 36 hours after the passage of the fire, the
cones of the lodgepole were found open and the seeds were seen
lying upon the ground. The opening of the cones had followed
after the passage of the fire at an interval sufficient to allow
the seeds to fall uninjured, for not even the edges of the delicate
wings were singed, a fact which seems difficult to reconcile with
the findings of Clements that the flame of the Bunsen burner
opened the cones in ten seconds.. If such were the case in a
forest fire the seeds must surely perish. In the case above
cited, however, the cones evidently were opening slowly, for at
the time they were observed they were not entirely expanded.
On the top of the standing trees the cones undoubtedly were
opening likewise in response to the drying action of the fire and
from this vantage were being broadcasted effectively onto the
cleared and receptive soil.

Of course the action of fire is not the only means of opening
the cones. They may he observed in some cases fully expanded

Fig. 29. In the valley of the Swan River, tributary to the Flat-
head. Betula papyrifera, associated with Pinus monticola, Tsuga
heterophylla, Abies grandis and other trees, representing the most humid
forest conditions of the region. July.

142

THE MONTANE ZONE 143

on green trees, but this is relatively rare. There is at hand a
branch about a foot in length bearing 27 cones, about evenly dis-
tributed over a period of 12 years, and not one of them has be-
gun to open. Of 167 cones collected in August five years ago
and kept continuously in the dry air of the laboratory, 70 still
show no signs of opening, 14 are beginning to open, and 83 have
opened enough to liberate a few over 200 seeds in all. These
seeds when tested showed a high percentage viable.

Lodgepole pine is not abundant in the immediate vicinity
of Missoula. It is restricted mostly to north slopes at elevations
of about 5,000 feet. This feature of its distribution seems to
be mainly a response to temperature. Lower clevations though
well watered rarely support vigorous stands in this locality, but
farther north in the Glacier Park at 4,200 feet, and in the
Kootenai Valley at less than 2,000, are vigorous forests of pure
lodgepole. In these regions heavy frosts may occur in any
month of the year. Northward the lodgepole forests become
more continuous and homogeneous; southward the continuous
and extensive forests of this species are found at seccessively
higher altitudes. Westward, of course, the lodgepole extends to
the coast; its eastward distribution in Montana reaches a merid-
ian traversing the State midway. In the north it is found in
the Bearpaw Mountains, a low range between the Milk River
and the Missouri south of IJavre. It occurs also in the Crazy
Mountains almost in the exact center of the State and in the
Beartooth Mountains northeast of the Yellowstone Park. In
this region Leiberg, reckoning trees of all ages with a basal
diameter of three inches and upward, concluded that the lodge-
pole constituted 45% of the forest species, and in the Little Belt
43%. Elsewhere it may be more or less according to circum-
stances, more where fires have occurred at intervals sufficient to
repress competing species, less where time has sufficed for the
maturing of the forest and invasion, or where conditions of re-
production have established a mixed stand from the start.

A summary of the biotic elements which enter into the
composition of the lodgepole species leaves no doubt as to its
fitness and capacity for distribution and survival. Among these
several qualities may be mentioned as positive factors. First
may be mentioned the abundance of the seed produced, which

Fig. 30. Priest River Valley in northern Idaho. Pinus monticola,
T'suga heterophylla, Abies grandis, Thuja plicata. In the foreground
Lysichiton Kamtschatcensis and Asplenium Filix-foemina,

lit

THE MONTANE ZONE 145

probably excels that of any other native species. Not only is the
annual crop abundant but the lodgepole begins early to bear
seeds, as early as the sixth year in some places. The lightness
of the seeds and their marked adaptability for wind dispersal,
their usual high rate of germination and long continued viability
are all points of marked importance. The ability of the lodge-
pole to grow in dense stands operates to exclude other species,
and its ability to recover from prolonged suppression further
makes for dominance. The lodgepole is also largely resistant to
disease. Against these points may be set off certain limiting
traits most of which are, however, not very definite or pro-
nounced. There appear to be certain limitations in soil require-
ments, and light and a marked susceptibility to fire injury.

It has been estimated that the average production of seed
per tree in Colorado varied from 20,000 to 50,000. Considering
the fact that the tree may begin as early as its 5th year to pro-
duce cones and that the cones remain closed for many years and
that when seeds are most needed, i. e., just after a fire there
is available for sowing not merely one season’s crop but the
combined fruitage of several years, considering also the extended
viability of the seeds and their high germinative capacity it is
evident that the lodgepole pine is beyond all competitors in the
advantage derived from a reproductive capacity. The facility
with which it preempts and holds newly seeded, especially fire-
swept lands, is a fact related partly to its preference for hare
soil as a seed bed, but more decidediy to the large amount of
seed available for distribution at the opportune time. It is
found under recorded temperatures of -55 to 112 degrees F. in
the United States and doubtless has much wider range. In the
same locality (Anaconda) it may be subject to an annual varia-
tion of temperature through 165 degrees F.

In the ability to recover after years of suppression is one of
the important factors in the persistence of the lodgepole. Un-
like many other species which would suffer permanent injury
from early shading, the lodgepole, after years of repression is
able to push forward rapidly to full vigor and reproductive
capacity as soon as the dominating individuals are removed. Es-
pecially mav this be the case where the cutting or destruction of

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4

146

THE MONTANE ZONE 147

the larger trees of the stand may throw open the land to a con-
test for supremacy among the local species.

There are few parasites to which the lodgepole is seriously
subject, and most of these do not destroy the tree, nor apparent-
ly retard its production of seed. The most serious enemies are
the bark beetles of the genus Dendroctonus which kill the
stands. Among the vegetable parasites Peridermium cerebrum
and P. Harknessii and the small mistletoe Razoumofskya ameri-
cana are the most common, but they are seldom conspicuous.

Against these more or less favorable traits may be set off
three which have a limiting effect upon its distribution. The
soil limitations are not a serious handicap to migration. Locally
such limitations are effective as in over-watered soils, the lodge-
pole requiring well aerated land with a medium amount of
available moisture. Some authors hold that the lodgepole shuns
calcareous soils, but that is a matter affecting local rather than
general distribution. Otherwise the lodgepole seems indifferent
as to the qualities of the soil. The effect of the intolerance of
this species, as was mentioned above, is seen mainly in the re-
tarding of its growth until such time as the shade may be re-
moved. The specific light requirements of this species, however,
like the edaphic relations, are more important locally than as
effecting the whole range of the species. In the third negative
element, that of susceptibility to fire, is a factor which must in
a far-reaching way affect the prosperity of the species through-
out its range and operate to reduce the area over which it may
hold sway.

Thus it will be seen that the positive factors in the make-up
of this species far outweigh those which are negative and which
would tend to weaken it in its struggle for survival. Such
adaptability is reflected in its wide distribution which extends
from the peninsula of lower California almost to the Arctic
circle and from the Black Hills to the very shores of the Pacific.

The Engelmann spruce (Picea Engclmannii) is one of the
most widely distributed trees of the Rocky Mountain forests.
Within the boundaries of Montana it has a wider altitudinal
range than any other species. From the crests of the highest
ranges it descends to the lowest point, within the State (Troy,
1,880 feet) and in Idaho to 1,500 feet. Jt is a prominent tree

U

THE MONTANE ZONE 149

of both the Hudsonian and Canadian zones. It is found plenti-
fully both east and west of the divide, forming 11% to 21%
in the Belts and Absaroka, 13% in forests of the Kootenai Val-
ley and more or less in other parts. At lower elevations the
species finds its best conditions on bottom lands and in cool
canyons and frequently reaches 3 or 4 feet in diameter. Pure
forests of Engelmann spruce occur and such are found in Gla-
cier Park, over limited areas, in the upper Avalanche Basin and
a good, uniform stand on the slopes of Brown Pass over the
Continental Divide between Waterton and Bowman lakes.

Certain factors are conspicuous in the nature and habits
of this species. It produces abundant seed; the seeds are small,
light and amply winged, and easily carried by the wind; the
seeds germinate well; the tree endures much shade and the
seedlings do well under heavy cover. The trees have great long-
evity and bear seeds for an extended period of time. On the
other hand the Engelmann spruce grows slowly even under the
best of conditions; it demands much moisture in the soil; its
temperature limits while they may be wide for brief periods
(-60 to 108) are more especially favorable toward the cooler end
of the scale.

The chief determining factors in the distribution of Engel-
mann spruce are water and temperature. It has been held (27)
that moisture alone is the dominant influence and that low tem-
peratures operate mainly in increasing relative humidity. This
seems to be true and the fact that in regions where the species
abounds it grows to large size in narrow canyons but may rarely
appear in the broader open stretches of river bottoms in the same
locality and at the same altitude where conditions are unfavor-
able for an equal degree of relative humidity. The effect of
high relative humidity, however, must not be regarded merely
as insuring a greater amount of soil moisture, but, as in the
ease of the vew and other species, seems to operate directly on
some phase of the transpiratory function. Places where soil
waters are near the surface and never lacking are seldom if
ever occupied by Engelmann spruce under conditions where
the weather is continuously warm during several weeks of sum-
mer and the relative humidity low. While day temperatures
may be occasionally high, in the favored habitat of this species,

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150

THE MONTANE ZONE 151

the nights usually are cool, almost to frost, and the usual daily
temperatures of July and August about 75 to 85 degrees. Engel-
mann spruce is sometimes planted in Missoula, but does not
thrive even under careful summer irrigation, although the Col-
orado blue spruce (Picea Parryana) and the Norway spruce do
very. well. Within the limits of its range the abundance and
dominance of Engelmann spruce is conditioned upon its seeding
habits and tolerance. As a competitor with other species it has
the distinct advantage of being strongly shade resistant, and
this quality is its sole compensation for its slow growth in height.
Field seedlings gain in height less than 4 inches in + years under
conditions apparently favorable. Other data on growth are to
be found in Tables 22 and 23.

The growth of this species may easily be checked by fires,
as the bark is very thin and the trees easily destroved. Fires
are less frequent, however, in this kind of forest than in some
others, owing to the moister conditions under which the tree
usually grows. The species is subject to few serious parasites
among the fungi, though some among the insects operate to re-
duee its vitality or shorten its life.

The most frequent companion of the Engelmann spruce at
all elevations, but especially in the higher ones, is the alpine or
sub-alpine fir (Abics lasiocarpa). It has almost as wide a range
of vertical distribution as the spruce, but in altitudes above 6,000
feet it becomes much more conspicuous and abundant, probably
owing to the lessened frequency of other species.

The salient characteristics of this species are, in the posi-
tive direction, a liberal production of seed from early vouth,
facility of dispersal and free germination. The species is tol-
erant and resistant to cold. Negatively its seeds have transient
vitality, the tree requires much moisture both in soil and air, its
upper temperature limit is low, its early growth is slow and it
is not resistant to fires (61).

The alpine fir is the most typical tree of the high mountains
in Montana, and from the highest slopes it descends to 2,000
feet in canvons in the northwestern part of the State. The most
favorable situations for this species are to be found in the
sheltered basins at altitudes from 5,000 to 7,000 feet. It is
found usually upon slightly elevated knolls of sloping ground

[ “MHoy] Uoomjoq surmoad wnudfipp yo pur ‘somo:
‘OGLYS SSOU-UOYOtL otf] ul oO

THE MONTANE ZONE 153

providing good drainage but where there is sufficient moisture
during the growing season. Unlike the spruce it seems to shun
the wetter soils. Groves of the alpine fir often shelter snow
drifts until August or even through the entire year.

This fir endures the most rigorous climate. Its temperature
range must extend from -60 to over 100 degrees for short periods,
with the prevailing summer temperatures between 30 and 85
at 6,000 feet elevation. It is the temperature which appears to
be the special controlling factor in the distribution of the alpine
fir, both local and general. Moisture likewise is influential but
is likely never to be absent during the growing season in the
zone where this species reaches its best development.

The alpine fir seldom grows in dense stands, but appears
more or less scattered and in groups. Its tolerance, however,
makes possible a dense forest which here and there is realized
over small areas. The foliage of the crowns is dense, especially
in older trees where it is sometimes almost impenetrable, and fre-
quently descending to the ground. Young trees may endure
shade for years and recover with rapid growth when the dom-
inating influence is removed.

Abies lasiocarna finds conditions favorable for its growth
throughout the Rocky Mountain region from Alaska to Arizona
and to some extent in the Cascades and coast ranges. In the
southernmost parts of its range its lower limit in altitude is
about 9,000 feet.

Another species forming a large part of the mountain for-
ests is the whitebark pine (Pinus albicaulis). It forms some-
times pure forests at 7,000 to 8,000 feet in clear orchard-like
stands of trees of medium size a foot, more or less, in diameter
and about 40 to 50 feet in height. Sometimes the trees of this
species in more favored situations between 6,000 and 7,000 feet
may reach a diameter of 5 feet or more, but such are rare. Trunk
diameters of two to three feet, however, are not uncommon. On
exposed, wind-swept situation at all altitudes within its range
it assumes a stunted and spreading habit, usually of 5 or 6 feet
in height. The white bark pine is the usual companion of the
alpine fir and Engelmann spruce, and its characteristically
branching tops can be recognized far and near. It enjoys a
natural range from British Columbia to southern California and

Fig. 36. A slide-rock slope, southern exposure, bearing Pinus pon-
derosa and Douglas spruce. Heavier forest to right Abies lasiocarpa,
spruce and lodgepole pine. Near head of Bitter Root Valley, about
6000 feet, August.

THE MONTANE ZONE 155

in the northern Rockies, where it seems to reach its best develop-
ment at 6,000 feet or above.

The positive qualities of the whitebark pine are few; it
produces seed liberally, endures a wide range of temperature
and seems adapted to rocky situations and meager soil. On the
other hand it is limited by the lack of facility in seed dispersal,
the seeds being heavy and large, which also renders them at-
tractive to squirrels and other animals. The tree is intolerant,
it thrives only in moist soil and having thin bark is readily in-
jured by fires.

The seeding habits of this species are somewhat peculiar.
Wind can have little influence on seed dispersal in a case where
the seeds are devoid of wings or structures which serve a sim-
ilar purpose. The cones do not open to discharge their seeds
but disintegrate at the core. Cones falling to the ground if
spared by animals, often give rise to trees in groups. Such trees
may differ much in size, but an examination of the stem section
will usually reveal the fact that they are of the same age. As
one tree of the group gains the ascendancy it comes ultimately
to stand alone. As the seeds of this species are wingless, their
distribution is not dependent upon the wind, and other agencies
must therefore account for their dispersal, in which squirrels
and other seed-eating animals doubtless have a large share. The
rare appearance of seedlings at relatively low altitudes, and
where it is practically certain there is not a seed tree within
miles, suggests the influence of birds. Among birds it is prob-
able that the chief agency is the Clark Nut-cracker or Clark
Crow (Nucifraga columbiana). Skinner (58) states that it pre-
fers pine seeds, sometimes tearing cones to pieces while yet at-
tached to the branch. More often the cone is detached and car-
ried away to a strong limb where it is held with one foot while
the bird strikes strong downward blows at it with its pickaxe bill.

In its temperature relations the whitebark pine shows a ca-
pacity to endure a wide seasonal range said to be from 60 to 100
degrees, but for the most part it is restricted to cooler levels
of elevation, seldom below 6,000 feet in’ Montana, though the
writer has sometimes found isolated individuals at 3,500 feet
in western Montana. It is found at about 6,000 feet in Glacier
Park and about the same in the Swan Range, from 6,000 to

ee a

ae

Fig. 37. Pure stand of Picea Engelinannii about the head of
Avalanche Lake in Glacier National Park. August.

156

THE MONTANE ZONE 157

8,000 in the Bitter Roots, and in the Absaroka Range above 7,000.
In the Little Belt Mountains it is found only on the highest points
above 8,000 feet. Its endurance of high temperatures is only for
brief periods at the altitudes which it usually inhabits.

In its local distribution it shuns the wet soils and is found
usually on rocky ridges which have better drainage and aeration.
Here it grows to its best size and so partial is it to the rock,
either fixed or in the form of fragments or boulders, that no
case can be recalled where trees of more than seedling size were
found in the wet soil. It is a common accompaniment of the
topography which is exhibited in crumbling outcrops of rock,
alternating with depressed areas composed of finer materials,
but seldom occupied by trees except at times the spruce. Sloping
mountain sides are also favorite situations for this species. Uni-
form stands have been found by the writer where the ground
cover consisted mainly of a thick carpet, ankle-deep, of small
heaths mainly Casstope Mertensiana. Its relation to tempera-
ture and to soil conditions are thus the important factors which
control its local distribution. Owing to its very thin bark it is
easily destroved bv slight fires and areas are known where
whole stands are reduced to dry and bleaching trunks with
little evidence of reoccupaticn by the same species, in marked
contrast to the progress of the lodgepole pine. At its best the
whitebark pine is not vigorous in propagation, and stands once
destroyed are very slowly restored. Nevertheless this tree is
readily found, as a rule in all the higher altitudes of the State
and ranks third among the native species as to the extent, and
uniformity of its distribution in this region.

Closely related to this species is Pinus flexilis, limber pine,
which in this region is found east of the main divide. Cases re-
ported of the finding of Pinus flerilis on the west slope in Mon-
tana seem not to be clearly substantiated. The two species are
similar in requirements and in altitudinal range. The twigs and
leaves are practically indistinguishable but the cones differ in
form, color, thickness of the scales and manner of opening. The
tree occupies high and exposed situations, and responds in the
manner of its growth and its form much as other trees in similar
situations, severely distorted and repressed.

The positive qualities of this species are found mainly in

‘psosapuod snug

‘oun (*
IYOQOLLOAO

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THE SUMMITS 159

its liberal seed production, its capacity for resisting a vigorous
climate, where the temperature falls to -60 degrees, high winds,
adaptability to various soils but not strict in its demands upon
soil mcisture. It is thin barked and could easily be injured by
fire, but in the open stands where it usually occurs there is less
danger from this menace than is usual with other species. It
seems not to be especially susceptible to disease. On the other
hand its disadvantages in the matter of seeding, the limitations
in the facilities for dispersal, the size of the seeds and the eager-
ness with which they are sought by animals, and its intolerance
of shade militate against its dominance in the range which it
occupies.

The limber pine has an extensive total range from Alberta,
southward threugh the Rocky Mountains to New Mexico and
westward to California. In the Belt Mountains it comprises
about 8% of the forest species and’ about 2% in the Absaroka
Range. It mingles more or less with lodgepole pine at the upper
limits of distribution of that species and in the higher sub-alpine
zcne is found with spruce, fir, and whitebark pine.

Tre SuMMItTs.

The sub-alpine zone of the Montana Rockies, as above
defined, represents the THudsonian zone of Merriam and is
with reference to all parts of its vegetation, a zone of sur-
passing interest. Its tree forms are few, it has a limited num-
ber of shrubby species and a considerable number of herbaceous
perennials. The trees are Pinus albicaulis, P. flexilis, Larix
Lyalli, Picea Engelmannii, Tsuga Mertcnsiana, Abies lasiocarpa,
and Juniperus scopulorum. In shrubby form Juniperus com-
munis also occurs in abundance. All of these except Lyall’s
larch and the black hemlock have a distribution extending across
the State from north to south, and all except these two and the
limber pine are found on both sides of the Continental Divide.
Two of them, Picea Engelmaunit and Juniperus scopulorum,
have a wide range of altitude, from the crest of the divide at
6,000 feet or more down to the lowest point in Montana, Larix
Lyallit belongs consistently to the high altitucles.

The aspect of the sub-alpine zone is not that of a continuous

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160

THE SUMMITS 161

forest, but of limited tracts of even though usually not dense
stands, or more often of bunched trees in small groups, separated
by meadows, bogs, lakes, rock fields, snow fields, chasms, ete.
Snow is perennial only in small patches, and even the glaciers
of the northern part are of very limited extent. The growing
season is short, however, and at an altitude of 6,000 feet may be
limited to about two months or less during July and August.
Heavy frosts usually oceur and snow may fall during this time.
Small brooks fed by melting snow run low or cease to flow at
night and the days are usually long and bright and warm. Veg-
etation awakens quickly and advances rapidly to flowering,
fruition and rest, so that usually before the end of August fresh
snows have begun to mantle the peaks and higher ridges.

The Rocky Mountains of Montana have no summer snow
line, and in rare cases only a distinct timber line. Most of the
high mountains are clothed with trees of fair size almost to their
very summits, especially on their more sheltered slopes, and
where forests are lacking, the influence is not snow nor cold but
chiefly wind and desiccation. Mt. Lolo of the Bitter Root Range,
rising to about 9,000 feet, is forested practically to its summit,
and Trapper Peak, the highest point of the same range, reaching
10,175 feet, is likewise timbered nearly to the summit. At Gib-
bon’s Pass across the Continental Divide from the Bitter Root
to the Big Hole the road passes through a dense forest of lodge-
pole pine, and where the railway lines cross the divide are scat-
tering stands of pine and juniper. The peaks and high ridges
of Glacier Park, from 6,000 to 10,000 feet have no perceptible
timber line.

Under the conditions cf the very short growing season and
other adverse aspects of such situations it is inevitable that the
increment of woody plants from season to season should be very
small, especially in the cases of trees in situations at all exposed
to wind. Trees sheltered in the center of a group make fairly
rapid growth. Near the top of the Swan Range a small tree
(Abies lasiocarpa) about 6 feet in height and about 3 inches
in diameter at the ground stood at the edge of a group, but in a
sheltered basin with trees back of it rising 40 feet or more. This
tree had no limbs on its windward side but to the leeward ex-
tended its branches about two feet. A section across the stem

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THE SUMMITS 163

showed 84 rings of annual growth, which could not be counted
without the aid of a lens. The accompanying table prepared
from observations on the trees of the sub-alpine forest, shows
similar conditions, although in neither of these cases were the
conditions less than of average advantage, and might have been
even better than the usual sites occupied by trees. It will be
observed that it required 60 years for the Engelmann spruce
to reach a diameter of 31% inches, 80 years for the pine to reach
43 inches, and 108 years for the fir to attain 414 inches in diam-
eter. These may be taken as typical figures for most situations
in the sub-alpine zone. The altitude in all these cases was about
6,200 feet. The first case cited was in the Swan Range east of
Bigfork, the figures in the table are from observations made near
Swift-Current Pass in Glacier National Park.
The shrubs most common in the sub-alpine forest are:

Salix Barclayi Menziesia ferruginea

“« westita Ledum glandulosum

‘« glaucops Kalmia polifolia
Aliuus incana Phyllodoce empetriformis
Rebes lacustre Cassiope Mertensiana
Sorbus scopulina Vaccinium erythrococcum
Crataegus rivularis u scoparium
Pachystima Myrsinites Hes oreophilum

Of these Salix Barclayi forms dense thickets three or four
feet in height here and there in basins at the heads of streams
in Glacier Park and elsewhere. In the openings in such forma-
tion Kalmia microphylla occurs along with Sphagnum and grasses
and sedges.

The other species of willow are plentiful but are not massed
and are only locally conspicuous. Alnus incana, however, forms
pure, dense and matted covering on some of the slopes of the
Arctic drainage, and in places elsewhere is prominent in the
forest undergrowth. The most characteristic of the high moun-
tain shrubs are some of the heaths and huckleberries, Ledum,
Cassiope and Phyllodoce are especially conspicuous in many
places, and Vaccinium erythrococcwm and V. oreophilum, low
and slender, are frequent in forests or open parks. Most of the
others named have an altitudinal range more or less extensive
and are found in the forests of the white pine and hemlock

‘SUINJUNOP, YOOY Lyles

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164

165

THE SUMMITS

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THE SUMMITS 167

as well as in those of the spruce and gsub-alpine fir. In fact
most of them may be found at altitudes varying from 3,000 to
8,000 feet under moist and sheltered conditions at the same lat-
itude.

Herbaceous plants of the sub-alpine zone, especially in the
open parks, are many and some of those collected by the writer
in different places in Montana are as follows:

Lonicera Utahensis Claytonia megarrhiza
Deschampsia atropurpurea Anemone parviflora
Phlewm alpinum Pulsatilla occidentalis
Carex atrata Draba crassifolia

«« Montanensis Mitella pentandra.

«« Mertensi Parnassia fimbriata
Scirpus trichophorum Dodecatheon pauciflorum
Eriophorum gracile Epilobium Hornemamnii
Eleocharis acicularis Phacelia sericea
Juncoides glabratum Mimulus Lewisii
Xerophyllum Douglasit e moschata
Veratrum Califormcum Castilleja miniata
Erythronium grandiflorum Erigeron macranthus
Calochortus apiciulatus Arnica ventorum

Spiranthes stricta

Usually the whole of the above list may be collected in any
of the mountain parks of the Montana Rockies, in flower or
fruit between the middle of July and the middle of August.
Juncoides ylabratum is conspicuous and abundant, forming a
veritable sod over large areas with grasses and sedges in the
wetter portions along the water courses and elsewhere, mingled
with Mimulus, Epilobtum, and Spiranthes. Yn the dryer places
Erigeron is conspicuous along with Anemone, Castilleja, Ery-
thronium, Claytonia and many others in a riot of luxuriance and
color. On the slopes with better drainage Verophyllum is dom-
inant plant, even on stony ridges and the older talus. Ery-
thronium grandiflorum, Calochortus apiculatus, Castilleja minc-
ata andErigeron macranthus of the above list, and others that
might be mentioned, are equally as abundant in many places at
altitudes of 3,000 to 4,000 feet as in the mountain parks at
6,000 feet or more elevation, though their flowering season is
from one to three months earlier. FErythronium in the vicinity

Fig. 43. At an altitude of about 6200 feet in the Swan Mountains,
Abies lasiocarpa with ground cover of Juncoides glabratum and snow
bank in the foreground, July.

168

THE SUMMITS 169

of Missoula at 3,300 feet opens from the 20th to 30th of April
and gradually unfolds at successively higher altitudes on north
slopes until in about five weeks, the same phase of development
may be found at 5,300. Under such conditions spring, summer
and autumn are telescoped into one brief period and the flowers
of these seasons at lower altitudes are mingled in one brilliant
assemblage, during the few weeks of vegetative activity. So short
is the growing season that the plants can scarcely await the
removal of the snow and ice. In one year on the 22nd of July
in a mountain park at an altitude of about 6,500 feet the writer
observed this luxuriance of vegetation where the blades of
Erythronium grandiflorum, Juncoides glabratum and other
plants were forcing their way through sheets of ice an inch or
more in thickness. The edges of old snowdrifts condensing into
a solid fringe of ice of varying thickness were closely surrounded
by the vigorous shoots of numerous plants several inches in
height. Some had perforated the ice and others under the thicker
parts had pushed upward into it and when the cakes of ice were
overturned their bottoms were marked by deep pits plainly evi-
dent.

Local differences are thus evident in the length of season
and the conditions of development in small areas side by side.
This must have its influence upon forest development as well as
upon herbaceous vegetation. The earlier an area is cleared of
its snow the longer its growing season. The occupation by forest
trees of slight elevations above the general surface in protected
coves where the.snow usually accumulates may be susceptible of
this explanation for from such the snow must sooner dis-
appear, while in the alternate depressions it may not entirely
melt during the whole summer. The advantages of a relatively
long growing season may thus account for the establishment of
forest species where otherwise it would be impossible.

SUMMARY.

1. The area here under discussion covers the State of Mon-
tana and neighboring parts of Idaho. Approximately one-half
of the total area may he said to be forested, but some of the

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1

SUMMARY 171

forest species extend into the plains eastward over the higher
elevations of land and along the margins of the valleys.

2. The altitude of most of this region lies above 3,000
feet. From the eastern boundary of Montana at about 2,000
feet the land rises gradually to the summit of the divide at
from 6,000 to 10,000 feet and drops more abruptly toward the
west to altitudes of 1,800 feet or less. The region is one of
greatly diversified topography with many high and some very
rugged mountain chains and intermountain valleys varying in
all widths up to 20 miles or over. The general course of the
ranges is from northwest to southeast. Geologically the surface
formations are largely of the Cretaceous and the Tertiary, with
some of more ancient origin. Most of the area has been glaci-
ated and extensive fields are covered with gravels. Mountain
glaciers still remain in some of the northern ranges.

3. The climate is relatively dry, the mean annual precipi-
tation varying from 10 to 24 inches in most places with occasional
exceptions in the direction of the greater numbers. The rain-
bearing winds of the northern Rocky Mountains are from the
west and southwest. The mountain chains which lie across their
path receive heavier precipitation on their western slopes, re-
sulting in heavier forests upon the western side at elevations
mostly above +,000 feet and correspondingly drier eastern slopes
and intermountain valleys with sparser woods or prairies. From
the standpoint of temperature the region is one of long winters
and short summers, a condition accentuated with the increase in
altitude. In different places and at different altitudes tempera-
ture of -20.to -50 degrees are frequent but not continuous and
the winters are not especially severe. The effect of the lower
temperature is seen mainly in the shortening of the growing
season and the relative frequency of summer frosts. Low rela-
tive humidity and a high rate of evaporation in summer and the
seasonal distribution of rainfall add their influence in deter-
mining the character of the vegetation.

4, The sources of the vegetation of the region are mainly
two. The Atlantic flora and the Pacific flora meet in the
northern Rocky Mountains and overlap. Many trees, shrubs,
and herbs have entered from the west, ‘either across the wide
basin of eastern Oregon and Washington at some earlier time

sees

Fig. 45. Section of a small fir (Abies lasiocarpa) six feet in
height, two inches in its greatest diameter, 84 years old. Illustrating the
severity of conditions for growth in exposed situations at about 6500

feet altitude.

SUMMARY 173

when, conditions were more favorable, or more recently by way
of the Okanogan country and the Selkirk Mountains, and enter-
ing Montana mostly by way of the Coeur d’Alene gateway, form
a large part of the plant covering on the western slope of the
divide. Most of the woody species represented bear either wind-
blown seeds or succulent fruits. Few heavy seeded species have
entered the region from any source. The eastern contingent is
less numerous among the woody forms. Some of these apparent-
ly have followed the streams across the plains, but the larger
number have made their way across the continent from the
Great Lakes to Alaska and have followed the Rocky Mountains
southward.

5. The mountain ranges act as barriers to eastward and
westward migrations. The continental crest in itself is not the
efficient barrier, but the elevation of a large land mass, con-
sisting of the main chain and its parallel ranges east and west,
so affect the climatic conditions over a wide space as to in-
fluence the movements of plants. The Bitter Root and Cab-
inet Ranges form a secondary barrier west of the main divide.

6. About 17 species of Gymosperoms make up the bulk of
the Rocky Mountain forest in Montana and Idaho. The number
of these is greatest along the western border of the area. Two
reasons are assigned for this. First the western part is nearer
the source whence most of the spécies probably-came and, sec-
ond, the climatic conditions are there most favorable. From
the western side eastward this number of coniferous species
diminishes to three or four on the eastern side.

7. Over much of the western part of the State forest dis-
tribution at lower elevations conforms to topographic influences
in response to moisture, temperature or light. Above 5,000 feet
the forests become continuous over most of the mountain region,
clothing the mountains to their summits, except in some cases
where desiccating influences render the peaks untenable for
woody species. There is no summer snow line on the mountains
of this region and no upper timber line that is constant or clearly
defined or subject to a particular elevation.

8. The life zones, according to Merriam, are represented in-
distinctly. The foothill region of vellow pine and Douglas spruce
represents largely the Arid Transition intergrading through the

174 FOREST DISTRIBUTION

larch and Douglas spruce on northern slopes to the marked
Pacific Coast Humid Transition of the northwestern vallevs
where the strongest mesophytic conditions of the region prevail.
The main body of the forests on the mountain sides belongs to the
Canadian zone and consists largely of lodgepole pine, spruce,
larch, whitebark pine and alpine fir. The Hudsonian Zone is
nowhere clearly delimited from the Canadian and most of its
species make up a large part of the forests between 5.000 and
10,000 feet. However, at the higher elevations the alpine fir,
Engelmann spruce, and whitebark pine are the principal trees,
though of inferior size and form owing to the severe conditions
there found.

LITERATURE 175

LITERATURE.

1, ABBE, CLEVELAND. First report on the relations between
climates and crops. Bull. Weather Bureau U. S. Dept. Agric.
342: 1-386. Au 1905.

2. Bessey, C. E. Plant migration studies. Univ. Neb.
Studies 5: 1-26. Ja 1905.

3. —-. The forests and forest trees of Nebraska
Ann. Rep. Neb. State Board Agric. 1899.

4, Buanxinsuip, J. W. A century of botanical explora-
tion in Montana. Montana Agric. Coll. Sci. Studies 1: 3-31, 1905.

5. —— Report of the botanist. Bull. Mont, Agric.
Exp. Sta. 32: 38-44, 1902.

6. Borrxer, R. H. Ecological investigations upon the germ-
ination and early growth of forest trees. pp 1-89. pl. 1-5. Lin-
coln, Neb. Ja, 1916.

7. Bowman, IsataH. Forest physiography. New York.
1911.

8. Briecs, Lyman J. and Beuz, J. O. Dry farming in re-
lation to rainfall and evaporation. Bull. Bureau Plant Ind. U. 8.
Dept. Agric. 188: 1-71. pl. 1. f. 1-23. N 1910.

9. CaLHoun, Frep H. H. The Montana lobe of the Kee-
watin Ice Sheet. Prof. Paper U. 8. Geol. Surv. 5: 1-62. pl.
1-7 f. 1-30. 1906.

10. Cauxins, F. C. A geological reconnaissance of northern
Idaho and northwestern Montana. Bull. U.S. Geol. Surv. 384:
1-112. pl. 1. 1909.

11. Cary, Merrirr. Life zone investigations in Wyoming.
U.S. Dept. Agric. Biol. Surv. N. A. Fauna 42: 1-95. f, 1-17.
1917.

12. Ciements, F. E. The life history of lodgepole burn
forests. Bull. U. S. Dept. Agric. 79: 1-56. pl. 1-6. Ja. 1910.

13. Cooper, WitttAM 8S. Alpine vegetation in the vicinity
of Long’s Peak, Colorado. Bot. Gaz, 45: 319-337. f. 1-8. My
1908.

14. Counter, Jonn M. A catalogue of plants collected in
1872 in portions of Montana, Idaho, Wyoming and Utah. Ann.
Rep. U. S. Geol, Surv. Terr. 6: 747-792. 1873.

176 FOREST DISTRIBUTION

15. Davis, W. M. The Mission Range. Montana. Proc.
Nat. Acad. Sci. 1: 626-628. D 1915.

16. Dwicat. T. W. Forest conditions in the Rocky Moun-
tain Forest Reserve. Pull. Forestry Branch Dept. Int. Canada.
33: 1-62. pl. 1-19. 1913.

17. Foiuanseer, RoBeRT, MEFKER, R. L. and STEWarRT, J.
E. Surface water supply of the Missouri River drainage, 1906.
Water Supply and Irrigation Paper U. 8. Geol. Surv. 203: 1-90.
pl. 1-5. 1907.

1s. Free. E. E. The movement of soil material by the
wind. Bull. Bur. Soils U. S. Dept. Agric. 63: 1-272 pl. 1-5.
1911.

19. Geyer. CHARLES A. Notes on the vegetation and gen-
eral character of the Missouri and Orevon Territories. made
during a botanical journey from the State of Missouri. across
the South Pass of the Rocky Mountains to the Pacific during the
years 1545 and 1544. Lond. Journ. Bot. +: 479-492. 653-662,
1845. 5: 22-41, 195-208, 285-310, 509-524. 1546.

20. Gray, Asi. Forest geography and archeology. Am.
Journ. Sei. and Arts. 16:—. 87s. (Bull. U. 8. Geol. Surv.
Terr. 6:62-77. 1530.)

21. Gray, As, and Hooker, JosepH D. The vegetation of
the Rocky Mountain region and a comparison with that of other
parts of the world. Bull. U. 8. Geol. and Geog. Surv. Terr. 6:
1-77. 1880,

22, Griccs, Roperr FF Observations on the behavior of
some species at the edges of their ranees. Bull. Terr. Bot. Club.
41: 25-49. -f. 1-6. Ja 1914.

23. Haun, H. M. A »otanical survey of San Jacinto Moun-
tain. Univ. Cal. Pub. 1: 1-140. pl. 7-14. Je 1902.

24. Harstpercer. J. W. Phytogeographic survey of North
America, Die Vegetatien der Erde. NIT. Leipzig. 1911.

25. Harrinerox, M. W. Review of forest metecrological
observations. A study preliminary to the dis: ussion of the rela-
tion of forests to climate. Bull. For. Div. U. S. Dept. Agric.
7225-122. 7, 1-60. 1893,

26. Haypex, F. VY. Plants collected during the exploration
of the upper Missouri by F V. Hayden. Rep. Sec, War. 2:
726-747, 1858.

LITERATURE 177

27. Hopson, E. R. and Fosrrr, J. H. Engelmann spruce
in the Rocky Mountains.. Cire. For. Serv. U: S. Dept. Agric.
170: 1-28. S$ 1910,

28. Knowuton, F. H. A catalogue of the Cretaceous and
Tertiary plants of North America. Bull. U. 8S. Geol. Surv.
152: 1-247. 1898.

29. Lxewerc, Joun B. Notes on the flora of western Da-
kota and eastern Montana adjacent to the Northern Pacific
Railroad. Bot. Gaz. 9: 103-107, 126-129. 1884,

30. — —. General report cn a botanical survey of
the Coeur d’Alene Mountains in Idaho during the summer of
1895. Cont. U.S. Nat. Herb. 5: 1-85. pl. 1. Ja 1897.

31. —._ Forest conditions in the Absaroka divi-
sion of the Yellowstone Forest Reserve, Montana, and the Liv-
ingston and Big Timber Quadrangles. Prof. Paper U. 8S. Geol.
Surv. 29: 1-148. pl. 7-2 1904.

32, ———___.. Forest conditions ‘in the Little Belt Moun-
tains Forest Reserve, Montana, and the Little Belt Mountains
Quadrangle. Prof. Paper U. S. Geol. Surv. 30: 1-75. pl. 1-2.
1904.

33. Lesquereux, Leo. Contributions to the fossil floras
of the western territories. JIT. Cretaceous and Tertiary Floras.
Rep. U.S. Geol. Surv. Terr. 8: 1-283. pl. 1-59. 1883.

34. Linperen, Wautpemar. <A geological reconnaissance
across the Bitter Root Range and Clearwater Mountains in Mon-
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1-15. 1904.

35. Livineston, B. E. Temperature coefficient in plant
geography and climatology. Bot. Gaz. 56: 349-3875. 1913.

386. Lyauu, Davin. Account of the botanical collections
made by David Lyall, M.D., R.N., F.L.8., Surgeon and Naturalist
to the North American Boundary Commission. Journ. Linn.
Soc. 7: 124-144. 1864.

37. MacDovuaan, D. T. The auxo-thermal integration of
climatic complexes. Am. Journ. Bot. 1: 186-193. pl. 17-18.
Ap. 1914.

38. MarsHatn, R. B. Results of spirit leveling in Mon-
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39. Mason, D. T. The life history of the lodgepole pine in

178 FOREST DISTRIBUTION

the Rocky Mountains. Bull. U. S. Dept. Agric. 154: 1-35. Ja
1915.

40. Marnews, O.R. Water penetration in the gumbo soils
of the Belle Fourche Reclamation Project. Bull. U. S. Dept.
Agric, 447: 1-12. N 1916.

41. Maximmiix, ALEXANDER Puiuiep. Reise in das innere
Nord Amerika in dem Jahren 1932-34. Coblenz, 1541.

42. Merwin, THomis. The plants of Lewis and Clark’s
expedition across the continent, 1804-1806. Proc. Acad. Nat.
Sci. Phila. Ja 1898. ,

43. Merriim, C. Harr. Life zones and crop zones of the
United States. Bull. Div. Biol. Surv, U. 8. Dept. Agric. 10:
1-79. pl. 1. 1898.

44, Newserry. J. S. The later extinct floras cf North
America. Monog. U.S. Geol. Surv. 33: 1-295. pl. 1-68. 1893.

45. Orecon Historica. Society. The correspondence and
journals of Captain Nathaniel J. Wyeth, 1831-36. Sources of the
History of Oregon. 1: —. Eugene. 1899.

46. Piper, CHArtes V. Flora of the State of Washington.
Cont. U.S. Nat. Herb. 11: 1-637. pl. 1-18. O 1906.

47. Pursu, FreperircK. Flora Americae Septentrionalis.
London. 1814.

48. Ramauey. Francis. Remarks on the distribution of
the plants in Colorado east of the Divide. Pestelsia. 1902: —.

49. Report National Conservation Commission. Papers on
the conservation of water resources. Water Sup. Paper U. S.
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90. Rospins, M. W. Climatology and vegetation in Col-
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51. Ross, D. W.. WHistuer, J.T. and Nope, T. A. Report
on progress of stream measurements for the calendar year 1905.
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32. Rowe, J. P. and Witson, R. A. Geology and economie
deposits of a portion of eastern Montana. Univ. Mont. Studies,
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53. RypperGc, P. A. Vegetative life zones of the Roeky
Mountains. Mem. N, Y. Bot. Gard. 6: 447-499, Au 1916.

LITERATURE 179

54, ———__—. Phytogeography of Montana. Bull. Tor.
Bot. Club. 27: 292-294. 1900.
55. ——————. _ Phytogeographical notes on the Rocky

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56. Scurmper, A. F. W. Plant geography on a physiolog-
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58. Sxinner, M. P. The Nutcrackers of the Yellowstone
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59. Smitty, F. J. The alpine and sub-alpine vegetation of
the Lake Tahoe region. Bot. Gaz. 59: 256-286. f. 1-4. Ap 1915.

60. SupwortH, GEeorce B. The pine trees of the Rocky
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mp. 1-10. My 1917.

61. ——————. The spruce and balsam fir trees of the
Rocky Mountain region. U.S. Dept. Agric. Bull. 327: 1-43.
pl. 1-25. mp. 1-10. F 1916.

62. ———_-———. Forest trees of the Pacific Slope. U.S.
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63. Tuwarrrs, R. C. Maximilian’s travels in N. America.
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64. Torrry, JoHN. Catalogue of the plants collected by
Mr. Charles Geyer, under the direction of Mr. I. N. Nicollet,
during his exploration of the region between the Mississippi
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65. Transeau, EH. N. On the geographic distribution and
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66. —_————. The relation of plant societies to evap-
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67. TurReEsson, Gore. Slope exposure as a factor in the dis-
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68. VisuER, S. 8. Report on the biology of Harding coun-

180 FOREST DISTRIBUTION

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69. Warp, Lester F. Status of the mesozoic floras of the
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70. Weather Bureau. Summary of the climatclogical data
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71. Weaver, J. E. A study of the vegetation of southeast-
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72. Weaver, J. E. and Turet, A. B. Ecological studies in
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73. Wauitroro, H. N. The forests of the Flathead Valley.
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74, Zon, RapHAEL, and Graves, H. §. Light: in relation
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75. ZON, RapHarEL, Seed production of western white pine.
Bull. U. 8. Dept. Agric. 210: 1-15. Ap 1915.

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