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2 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE,

ditions were frequently severe, limiting growth and reproduction.
Sentiment toward the practice of silviculture was generally apathetic
or actively antagonistic.

With these conditions prevailing, the forester faced the problem
of improving the health of the stand, increasing the rate of growth,
and securing more pine reproduction to the limited extent that one
cutting permits. In 10 years’ time a large amount of valuable data
has been accumulated which has served to indicate good silvicultural
practice. There is an increasing demand for reliable growth sta-
tistics in the preparation of working plans, not only for public
forests but for private timber also, as evidenced by recent requests
from several private timber owners contemplating management of
their tracts on a permanent yield basis. In addition, all possible in-
formation should be available for those directly or indirectly con-
cerned with the forests and their products in considering the reme-
dies for forest devastation and the establishment of forest policy
for the State and region.

As indicated in the text, some of the conclusions drawn from this
study as to the best silvicultural practice are not immediately ap-
plicable on the national forests because of management conditions.

DESCRIPTION OF DATA.

The study is based on 25 permanent sample plots, varying in size
from 6 to 25 acres, totaling about 300 acres, on which over 13,000
numbered trees have been measured at 5-year intervals from 1911 to
1921. The attempt has been made to bring out the important points
rather than to set down in detail the multitude of possible variations
represented. For the sake of simplicity the reaction of individual
trees 1s used as a basis for analysis wherever possible. The plots are
located in the Sierra timber belt from near Mount Shasta to a point
southwest of Mount Whitney. Sites vary from first to third quality
(on a scale of five classes based on total height at maturity). The
four more important types—pure yellow pine, yellow pine-sugar
pine, mixed yellow pine-sugar pine-Douglas fir-white fir-incense
cedar, and sugar pine-fir—are represented. Purely experimental cut-
tings were not feasible. The plots, therefore, do not represent ideal
site, type, or other factors. They were established just before or just
after logging to represent the results of actual average marking
practice of that period on the national forests. The marking was
often based on a compromise between economic lumbering and silvi-
culture.

The areas were carefully mapped to show distribution of num-
bered trees, stumps, cover, brush piles, etc. All trees 4 inches in
diameter and larger were numbered with metal tags, diameters were
taken in inches and tenths with a steel tape, and total heights and
heights to base of crown to the nearest foot with a Klaussner hyp-
someter. A detailed description was made of each tree, giving its
dominance class, width of crown, color and density of foliage, form
of top, presence of mechanical injuries or pathogenic agencies, and
a rough estimate of age and apparent vigor. Reproduction data
were secured from subplots, in the form of permanently marked
continuous strips 0.1 chain wide, or a series of mechanically located
quadrats varying in size from 5 feet to 1 chain square. In some cases

RESULTS OF CUTTING IN THE SIERRA FORESTS. 3

each seedling is mapped or marked with a numbered tag and wire
pin. Annual examinations have been possible for only a few of the
reproduction plots.

The early methods of cutting represented by the sample plots in
this study differ considerably from present methods. All of the
earlier cuttings, including those on the plots, were light, leaving a
volume of 10,000 to 20,000 board feet per acre, representing 30 to 60
per cent of the original stand, and contemplated a second cut in 30 to
60 years. This method was termed “ selection ” cutting for lack of a
better name. Yellow pine and sugar pine were strongly favored,
with the hope that the percentage of these species would be increased
in the next stand. In reality, many of these cuttings resembled
somewhat the second stage of a shelterwood system. The virgin
stands were characterized by even-aged groups of uniformly over-
mature trees with advance reproduction in openings due to the action
of firés and insects. They might be compared to the first stage of a
shelterwood method after the cutting to secure reproduction had
been completed. The original cutting done at the time of the sale
was designed to release advance growth, secure further restocking,
and enhance the rate of increment on reserved trees. The method
differed from the true shelterwood system in that only two cuttings
were contemplated and the final removal of the overwood was de-
ferred for a long period.

Since these early sales, when very light cutting was the practice,
the tendency has swung to the opposite extreme, very heavy cutting,
especially on poorer sites, leaving only thrifty seed trees for insur-
ance against destruction of advance growth by fire. At present there
seems to be a logical reversion to an intermediate course, in which a
considerable nucieus of thrifty standards and sound, thrifty, mature
trees are reserved, especially on the better sites, for increased volume
and value increment in a second cut and to insure adequate seed. It
seems likely, therefore, that future cuttings may not differ greatly
from some of those on which this study is based.

GROWTH OF REMAINING STAND.

Considering first the rate of growth of reserved trees without
regard to quality increment, there are several factors which have
proved to be of prime importance. Of these, site will be consid-

ered first.

SITE.

The importance of site as affecting method of cutting can not be
overestimated. Criteria for site differentiations had not been devel-
oped at the time of the earlier sales, and. in consequence as heavy
stands were sometimes reserved on poor as on good sites. The results
of this study indicate that no method of cutting on Site III or poorer
will result in a rate of growth which, in itself, will be sufficient to
justify reserving a considerable volume of trees approaching ma-
turity for increased wood production.

This is to be demonstrated if some of the plots are arranged in
order of site from the poorest to the best, using only trees between
12 and 30 inches in diameter, which furnish most of the reserves.
Yellow pine, because of its presence on all of the plots, is used as an

4 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE.

indicator to express the relation in annual basal area growth per
cent maintained between sites during the 10 years since cutting.
The same individual trees have been followed throughout the period.
The effects of accidental death and the entrance of new trees into
the lower diameter classes have been eliminated in order to bring out
merely site potentialities.

There are, of course, age differences within 6-inch diameter groups
between such extremes of site, and some variations in stand density
which tend to enhance the apparent differences, but, in the main,
site variation is the controlling factor in the figures given in Table 1.

TABLE 1.—Periodic annual growth, per cent, in basal area of western yellow

pine. -
Diameter classes
Num- (inches).
Site. | Plot. ber of
trees.1
12-17 18-23 24-29
ii

WINS hastasG: fae se f Nose toe PA ee ee eee ee 288 0.78 0. 62 0. 45
Ill DAN OG Leer oe ta ete on rw pee ae CES an 2 Sn 261 1.35 90 . 67
J S723 hoe oe al Me AB ts Ss Ek De aS ee eae ons nae Ta 306 ay 98 .70
A WS Camislaus, Se) < picid sa eS yes eet ea sae. eae eee een eee 160 2.69 1.61 1. 29
I SS CET is pe a ae ey Se Nee eee er eae ae ee he es ae ae 33 3574 3.00 . 78
I SequoinnG ori 1s. 5 2a tee Se sea tee eee eee cee 76 4,72 4, 21 2.15

1 The numbers of trees in this and the following tables include all those of the given site, plot, species, and
size class.

Examination of many cut-over areas leads to the belief that these
figures represent a fair average of what can be expected from reserved
trees. The best silviculture, therefore, on Site III or poorer, would
be designed to secure reproduction and release advance growth, and
only on Sites I and II would a reserve volume be left for increased
growth. Management considerations, however, may justify the reser-
vation of a considerable volume for a second cut.

SPECIES.

On Site II or poorer the species under consideration may be
arranged in order of rapidity of growth as follows, the most rapid
first: White fir, sugar pine, Douglas fir, yellow pine, incense cedar.
Averaging the rates for 18 to 24 inch trees for 15 plots on-which all
species except Douglas fir occur, there is given in Table 2 the relation
between annual basal area growth percentages, which reliably reflect
volume growth also.

TABLE 2.—Rate of growth, per cent, in basal area by species,

Annual.| Basis.

Per cent.| Trees.

Wife fir 2252 Se 5at = Rest Soles ASE oh a ao ee ee cette Soe tae a IIe ee 2. 22 463
SUPAL DING «2082 so. Sone oes ons seantet eee cpiaate ee weiace ee eee eee ok heen 2.07 81
Wellow. pines 02 bis V See Sere a ee on oe eee ee eet lacie nen erat Seraes Sao 1.50 156
Incense'Cedar : ='s 22,2 SeS.ce0 = cde ego a eee ee oe ee ee ees Nga k es ee. LES rceeeeees ‘pl 321

Douglas fir is omitted because it is present in only a few cases.
Comparison under similar conditions indicates that it grows rather
more rapidly than yellow pine in this region. .

RESULTS OF CUTTING IN THE SIERRA FORESTS. 5

On poorer sites incense cedar is usually conspicuously behind the
others in rate of growth, but it is remarkably adaptive to site dif-
ferences and under the most favorable conditions, up to about 24
inches in diameter, may exceed all species except white fir.

It is evident that, from the standpoint of growth, sugar pine is a
better tree to leave than yellow pine. It also furnishes the most
valuable wood of all the species in this region. White fir, because
of its rapid growth and, as will be seen later, high reproductive
capacity, will doubtless receive more consideration under manage-
ment as the market for pulpwood and box and low-grade lumber
improves. Sugar pine and white fir likewise exceed the other species
in rate of height growth for a given age class, as well as in total
height at maturity, and consequently maintain their superiority in
volume growth to an even more striking degree than in basal area.

Plainly, therefore, the sugar pine-fir type, which is closely lhmited
to first-quality sites and is composed principally of the two most
rapid growing species, promises the highest yields under manage-
algae SIZE AND AGE LIMITS.

After site, age is probably the most important factor affecting the
rate of growth. But the timber marker can seldom determine age
accurately and must depend on size as expressed by diameter and
other external features in estimating degree of maturity.

Of the four species considered here, sugar pine maintains a good
rate of growth to a higher diameter than any of the others and on
Site II or better will maintain a rate of 2.5 per cent annually up to
30 inches. On the best sites well-formed, well-located sugar pines
make good growth up to 36 inches in diameter, but as a rule about 30
inches should be the upper limit in marking trees of this species to
be reserved.

On the best sites selected yellow pines maintain good growth up to
30 inches in diameter, but under average conditions trees over 24
inches seldom exceed a rate of 1 per cent annually, and only under
exceptional circumstances should trees above 26 inches be left.

The rate of growth in white fir decreases rapidly above 24 inches
in diameter, and larger trees of this species should rarely be reserved
in marking, even on Site I.

Incense cedar shows a marked decrease in rate of growth above 18
inches. About 24 inches should be the limit in cutting, since smaller
trees are doubtfully merchantable. 7

Table 3, made of averages of five plots classed as Site I, brings out
the relations discussed above. :

TABLE 3.—Site I—Average periodic annual growth, per cent, in basal area,
1910-1920.

Diameter classes (inches). Basis

. 4. 4 cee _}| num-

Species. Sonat

4to1l |12tol7 | 18 to 23| 24t029 |30t035 | 36to41} 42 up. | trees.
a a eee ree 6.45] 3.30] 2.20] 1.50 | 1.15] 0.90] 0.70 798
ee 7.10} 4.05} 3.10] 2.70; 2.10] 1.40 .70 716
Sa a ee oe 9.70 5. 30 3. 30 2.00} 1.50 1. 20 1.00 1,131
SL se 7.10 4. 00 2. 40 1.70 1.10 - 80 0 135

6 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE.

An expression of growth on an age basis is shown in Table 4,
which gives average results from eight plots on the Plumas National
Forest. These plots represent Site II, but a heavy stand and lght
cutting resulted in rather slow growth.

TaBLe 4.—Site I]—Relation of age to annual growth, per cent, in basal area.
(Hight plots, Massack, Plumas National Forest, curved.)

Num-
Neopia ie to eRe 50 100 | 150 | 200 | 250 | 300 | 350 | 400 | Per
trees
SPECIES
Wihtitefir. cleus oo eee ae: 4. 50 2. 20 125 Ua) 0.99 0. 80 0, 70 0. 60 789
SU Sal DITO s .6 toe eo ee 3.30 1.90 1. 50 1, 20 . 80 50 40 . 40 437
Mellowsapine sot ee 2.40 1.40 95 .70 . 60 55 50 45 724
iticenseicedars.. =) 22. 8s.-.6 2. 40 1. 50 . 90 .65 . 99 50 45 . 40 1, 249

After 200 years, which roughly corresponds to the 24 to 29 inch
size class, the rate of growth for all species under these conditions
falls below 1 per cent annually. Probably 150 years, which corre-
sponds to the 18 to 23 inch size class, should be the limit in cutting
for all but sugar pine, in which value increment as well as better
sustained growth has an influence, taking into consideration, of
course, site and other factors. |

On some of the earlier sales many large, obviously mature pines
were left, primarily to increase the proportion of pine reproduction,
and their presence results in a material decrease in the average rate
of growth maintained. Such trees represent a high risk of loss by
fire or insects and, as will be seen later, have resulted in very little
reproduction. How far leaving such trees is justified on the ground
of improved quality of second cut will be discussed below.

In selecting trees to be reserved it is of the greatest importance
that the marker be able to estimate accurately degree of maturity,
vigor, and probable effect of cutting, as well as soundness and seed-
producing capacity, in order to utilize completely the potentialities
of species and sites. Results may be neutralized by accidental losses
or unproductive trees. Certain external features have been found
most reliable as reflecting vigor, such as color and texture of bark,
form of top, color and density of foliage, size of crown, and freedom
from disease.

CROWN SIZE AND FORM.

The crown furnishes the most reliable index of what may be ex-
pected from reserved trees. A dense, rich green, pointed crown
gives certain evidence of a thrifty tree. The most significant single
factors are crown length and form of top. If yellow pine is again
used for demonstration, considering only trees between 12 and 30
inches, on the basis of ratio of crown length to total height, the
following relation, shown in Table 5, expressed in annual basal area
growth, per cent, is found:

RESULTS OF CUTTING IN THE SIERRA FORESTS, 7

TABLE 5.—Relation of crown length to rate of growth in basal area.

[Basis, 434 trees. Curved.]

Annual per cent. Annual per cent.
Crown ratio. Crown ratio. ——$——————————————
Site I. Site II. | Site III. SiteI. | Site II. | Site ITI.
2). ee 2 1.40 0. 40 OF4G 58602 22 52s. be Ps 2. 40 1.01 0. 55
LU ae 2 1.50 ~00 ORS OSes a hea 3. 60 a 170) 80
SCS ae ee iD 65 ESN (o'( iaes aE ee aes | 4,90 2. 50 1. 20

Trees with narrow, long crowns are usually growing more rapidly
than the average trees of the same size. For yellow pine, probably
60 per cent of the total height is the most desirable proportion of
crown for standards of the size usually reserved. Trees with larger
crowns are too limby, and those with shorter ones are apt to be
growing slowly. On all the sample plots considered here, the length
of crown for all size classes averages 65 to 70 per cent of the total
height. On poor sites, density of stocking being the same, trees of
a given size carry relatively smaller crowns than on good sites, as is
shown by Figure 1.

A significant fact brought out clearly during this study is that the
ordinary crown classification based on position of trees in the crown
canopy, when applied to irregular mixed stands of this character, is
practically valueless as an indication of relative vigor of individual
trees. Taking trees of the same size and species representing the
ordinary dominant, codominant, intermediate, and suppressed
groups as carefully classified in the field, one would expect to find
a definite relation between crown class and the crown-height ratio,
and between crown class and rate of growth, increasing from the
suppressed to dominant trees. This is not found to be true of the
present data, although it doubtless is true for even-aged stands.

_ Taking 318 yellow pines on the Plumas plot classed as dominants
and segregating them into two groups, the first composed of trees
with crowns of average size or larger and pointed tops, the second
with smaller than average crowns and round, flat, or dead tops, it
was found that the trees of the first group were growing at a rate of
1.22 per cent annually in basal area, while those of the second group
were growing at a rate of only 0.42 per cent annually. On the same
area trees of the same size, called intermediate and suppressed, were
divided into similar groups. The first of these were growing at the
rate of 1.37 per cent and the second 0.96 per cent annually, or con-
siderably faster than dominants of the same character.

The several important observable factors which contributed to an
accurate estimate of vigor might be combined into four thrift or tree
classes, which would guide in the mental appraisal of each tree
according to the following standards:

Class 1—Dominant, codominant, or isolated trees, with pointed
tops, well-shaped crowns forming 60 per cent or more of the total
height; sound, symmetrical trunks; bark characteristic of young
trees; foliage dense and rich in color.

Class 2.—Similar to the above in all respects except with crowns
of smaller than average size,

BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE.

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Fic. 1.—Ratio of crown length to total height in relation to size of tree and site. Western yellow pine, all crown classes.

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RESULTS OF CUTTING IN THE SIERRA FORESTS, 9

Class 3. s of any crown class having average-size crowns or
larger, aE or flat tops, thin foliage, bark characteristic of ma-
turity, with sound, well-formed trunks.

Class 4.—Trees of any crown class with smaller than average
crowns, pale, thin foliage, flat or dead tops, poorly formed trunks,
bark characteristic of poor vigor.

Seriously diseased trees are, of course, considered apart.

The reliability of such groups as indicating relative vigor is shown
in Table 6, in which 349 yellow pines over 12 inches in diameter on
the Plumas National Forest are arranged according to this plan.
Only dominant and codominant trees are included. The inclusion
of intermediate and suppressed trees would accentuate the differences
shown in Table 6.

TABLE 6.—Relative vigor of different classes of dominant trees.

= Annual | Devia-
Tree N fanbet basal tion
class. aaa area from
I : growth. | average.
See
Per cent. | Per cent.
“ Bry 209 ze, +56. 3
eee 39 .95 +21.8
ee ee he Al 55 f+ —29.5— 4
ue] Becher «dd te AG. 1-4

o

The relative response of such classes to cutting will be discussed

jater.
DISTRIBUTION—DEGREE OF CUTTING.

A study of the growth of individual trees on the various sale areas
brings out clearly the disadvantages of the so-called group selection
cuttings and indicates that trees reserved for increased growth and
seed production, particularly yellow pine, should not be left in
groups, if this can be avoided. It has been argued that such groups
offer greater protection against wind. The data under consideration
throw no light on this subject, as windfall has been of shght conse-
quence on the study areas. Smith and Weitknecht, in southern
Oregon, found windfall to be heavier in groups of 4 or 5 than for
single trees and 13.4 per cent higher for groups of 16 trees or more
than for groups of 4 or 5. Frequently in this region the only avail-
able reserves occur in groups, and cutting is av cided because dam: age
results to remaining trees from logging.

Many increment ‘hori ings indicate that trees left in groups seldom
respond to cutting. This is illustrated in Table 7 by the growth
figures for typical yellow pines on the Stanislaus and Sequoia Na-
tional Forest timber-sale areas, which give the annual rate by 5-year
periods, before and after cutting, for trees between 12 and 24 inches
in diameter. The number of trees included has been limited by
selecting from several hundred bored only those as nearly similar as
possible as regards distance of cutting, age, vigor, and crown charac-
ter. Trees have been considered released when lar ge trees were cut
within 60 feet of them.

49263 °—23

2

10 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE.

~

TABLE 7.—Iffects of grouping on basal area growth, per cent.

Before cutting. | After cutting. | A ver-

Num- ‘) oh =| age in-

Plot. ber of | | crease
trees. 10 5 5 10 15, Sor .de=

years. | years. | years. | years. | years. | crease.

Pey
Stanislaus: cent.
Releaseds-tre boss) Soph ee ed =e Sane m oe 16 2. 22 2. 26 2. 81 2 Oty ein eee +21.4
EGHAM STOUDS seen: cocecee os Bote 10 aga 1.51 NN AE Ee ee —10.9
Sequoia:
HGleASCd 2s «Ja ssesis oe st oe alte oes Hoses | 13 2.78 3. 20 3-43 |° 3:32.) - 2.55!) +E 307
WelvaTareTOUPS: 2.2. =~ 2 Se sagt eran ce Snaeiee 15 3. 30 3.30 3. 59 3.06 | 2.59 es i

The Sequoia area before cutting was already quite open, so that
the cutting resulted in only slight changes i in rate of growth.

In general the trees left in groups “declined in rate of growth,
while the growth of released trees was accelerated by the cutting.
This relation is more clearly illustrated by the accompanying dia-
grams of typical increment cores. (Fig. 2.)

It has been well established that leaving trees in groups has an
adverse influence also on seed production, as the trees, unless they are
fully released, build up their crowns only slowly after cutting.

Because of the presence of many variable factors, comparison of
these sample plots does not indicate clearly the effects of degree of
cutting on rate of growth. At Massack, on the Plumas National
Forest, eight plots, originally representing fairly similar stand and
site conditions, were subjected to cuttings of various degrees with
this object in view, but, unfortunately, the differences in degree of
cutting were so slight and all cuttings were so light that the results
are obscure.

The slow rate of growth maintained by all of these plots was prob-
ably due primarily to the dense stand left, which averaged 73.5 trees
over 4 inches in diameter and 20,000 feet board measure per acre.
Average heights of the tallest trees indicate that these plots repre-
sent a “good Site IT, in spite of which the annual rate of growth in
basal area averaged only 1.02 per cent, whereas the Tahoe plot, a
much poorer site, classed as third quality, but with only 23.1 trees
and 15,520 feet board measure, maintained practically the same rate,
1.01 per cent. Similarly, another Plumas plot classed as Site ITT,
with 51. 5 trees and 10,065 feet board measure per acre, maintained a
rate of 1.22 per cent. Bearing in mind the probable effects of differ-
ences In composition and size of remaining trees on these plots, which
would tend to favor those at Massack, the hghtness of cutting seems
to be the only explanation of the slow growth.

Weidman, probably under more uniform conditions in yellow pine
stands in southern Oregon, found a very close correlation between
the acceleration of erowth and degree of cutting as expressed by per
cent of volume removed, but arrangement of the present sample plots
in order of degree of cutting shows little correlation as to rate of
growth, probably because of site and type differences.

Light cutting results in leaving many large mature or overmature
trees which greatly reduce the average subsequent rate of growth.
Moreover, the loss of one such tree, containing high-quality material,

LS

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11

THE SIERRA FORESTS.

RESULTS OF CUTTING IN

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12 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE.

may neutralize the volume produced by thriftier trees, so that no net
growth appears. For illustration, take the Plumas plot, considering,
for the sake of brevity, only yellow pine, which formed 86 per cent
of the original and 74 per cent of the present volume. On the basis
of the previously discussed tree classes, the remaining merchantable
trees were divided by field observation into two groups, the first in-
cluding trees which would be cut under present marking methods,
the second including trees which would be reserved. The compafa-
tive annual rates of erowth of the two groups during the 10 years
since cutting are shown in Table 8, expressed in basal area per-
centages.
TABLE 8.—Comparative annual rates of growth.

Diameter classes.

l Total.
Group. | 12 to 17 18 to 23 24 to 29 | 30 to 35 | 36 plus.
‘Num- Per |Num-| Per |Num-|} Per |Num-|} Per |Num-| Per |Num-] Per
ber. | cent.| ber. | cent.| ber. | cent.| ber. | cent.| ber. | cent.| ber. | cent.
OCH = see Sod were ee 32 | 0. 84 33 | 0.85 36 | 0.72 27 | 0.48 12} 0.35]; 140] 0.60
MOVCAVC. seen eee 104 Pe 77 73 | 1.34 28 | .90 1 . 59 3 | er00s 2265 aedeals
A VOTAT ee Ree ek Sek ae 2 bate esOae eee jLO9D NES. = Ais) bel eae se ARIS LON jee3 ee AY Ae eee 89
Percentage deviation of ;
trees to cut from the |
RyeTALCS = eee ee —35.6 | —22.4 —ll.1 | —10.3 — 26,3 | —32.6
} :

Expressed in volume, the trees which would have been cut totaled
118,200 board feet, which produced 40 board feet per acre annually,
while the total volume of those which would have been left was
96,840 board feet, which produced 63 board feet per acre annually;
that is, 45 per cent of the total volume produced 61 per cent of the
total growth. Such a cutting would have reduced the stand left from
57 to 18 per cent of the original volume, would have added 4,930
board feet per acre to the cut, and probably would have resulted .in
more rapid growth per cent of the trees left than actually occurred
on the larger number reserved.

On one 20-acre plot on the Stanislaus a stand per acre was left of
24,100 board feet, containing 16.9 trees over 12. inches in diameter,
which formed 46 per cent of the original volume. ‘There were left
14 yellow pines and 12 sugar pines over 42 inches in diameter, the
largest tree being an 82-inc ch sugar pine 215 feet high. Considering
the quality of this site, which approached Site I, a rate ot erowth
24 to 3 per cent annually might be expected. The aVerage rate main-

tained by the surviving trees, however, was only 1. 44 per cent in
basal area, and the net total j increment in ead feet was only 0.93 per
cent annually. The reason for this is clearly the presence of over-
mature, slow- growing trees, as will be seen from Table 9.

For any given size class, sugar pine maintained, in general,
normal position as to rate of growth, but its agoregate rate was
lower than for any of the other species. The high open of
sugar-pine trees in ‘the larger-size classes gives the explanation. The

same condition was true to a lesser extent of the other species.

RESULTS OF CUTTING IN THE SIERRA FORESTS. 13

Taste 9.—Periodic annual basal area growth in per cent, Stanislaus National
Forest, 1910-1920.

Diameter classes.

Species. | | Total
4to 11 |12tol7| 18 to 23 | 24 to 29| 30 to 35 | 36 to 41 oe
inches. | inches. | inches. | inches. | inches. | inches. | *~ UP:
White fir:
_ UPD DE ee ee ee x ae 9 4 3 1 4 1 7
LET) Gi | aes peepee gs een eee 9.11 3. 63 3. 90 87 98 . 63 33 Dees
Sugar pine:
TSF Fir 0 2) ee ee ta 34 4 8 4 5 8 1A 75
An ia ae ee t.? 6.35 | Slee a Suh) 2586-7 2 195 [1.03 O58 452-1. 06
Yellow pine:
“AT SEST Pt PS ee A a ee 273 71 55 44 27 19 14 503
LEE INT Tint Se Se ek ee 4. 92 2. 74 1.61 1.39 37 . 69 38 1. 46
Incense cedar
TA) Titt. 2S tl Se ee ee ee eee 53 21 14 6 4 1 6 105
LD ET See ee eee ee 5. 53 24h 1. 66 27 123 42 18 BY

ACCELERATION OF GROWTH.

It is to be expected that the degree to which growth is accelerated
by cutting will depend upon the proportion of the stand removed,
provided age, site, composition, and other factors remain compar-
able. As stated previously, variations in these factors on the plots
here considered have been so great as to mask this relation. There
are, however, several other factors more clearly emphasized by the
present data than degree of cutting, which must be given considera-
tion if enhancement of the growth of reserved trees is to be secured.
- Study of several hundred increment cores has shown that indi-
vidual trees of all species and all ages seldom fail to respond if the
trees removed are near enough so that lght and soil-moisture re-
lations are materially improved for those that remain. If, prior to
cutting, a given tree was already receiving all the hght it could
utilize, its response will depend upon the increase in available soil
moisture. As a rule, no acceleration is observable unless trees are
removed within 50 or 60 feet. If the stand is already quite open
before cutting, and the current rate of growth be high, no response
may be apparent. An example of this is shown in the Sequoia plot
in Table 7. Expressions of acceleration of growth, based on per-
centage ratios between the average rates before and after cutting,
do not, of course, give the total effect of the thinning, which is in
reality the difference between the actual rate and that which would
have been maintained with advancing age had no cutting been made.
This is shown in Table 10 by comparing the growth rates of trees
left after a cutting with those in adjacent virgin timber, using only
yellow pines as nearly as possible the same in size, crown form, domi-
nant class, and other respects, during the same periods as indicated
for trees from the Sierra National Forest. The figures represent
the percentage ratios between the rates maintained during one 5-year
period and the preceding one. The remarkable decrease in rate
during the last period on the cut-over area may be due to the com-
bined effects of rapidly invading bear clover and reproduction, and
a series of four exceptionally dry seasons from 1917 to 1920.

-49263°—23-—-3

14 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE.

TABLE 10.—Comparison of basal area growth per cent on virgin and cut-over
areas during successive 5-year periods, Sierra National Forest.

Per cent of increase or decrease over
preceding period for periods ending—

Fi Number
Condition of area. of trees:
1905 1910 | 1915 192%
WAL ia We ng a pe DET ee ns Mig Spey eens Pg SENT y= 13 —3.1 —12.7 —8.5 —13.5
CAITOVER LO0G n= 2 oa oe ee ae Se es ee eee 28 —3.7 +57.8 +42.0 — 58. 6

The ability to respond to the stimulus of cutting varies with the
species. It has been stated that the amount of acceleration is in-
versely proportional to the hght requirements of the species. If this
be true, we might expect white fir, one of our most tolerant species,
to show a greater relative response than yellow pine, the least tolerant
in this region. The results obtained from increment borings are not
in accordance with this expectation. It is difficult to get strictly com-
parable conditions, and present data are not considered final. To
obtain as nearly as pessible comparable data for the two species, how-
ever, there have been selected from many trees bored on each plot a
few as nearly as possible similar in size at time of cutting, character of
crown, and position. All the trees were dominants or codominants
with large pointed crowns about which some cutting was done within
a radius of 60 feet. Trees which stood in stream beds or were other-
wise exceptional have been omitted. This limiting of the data gives
the appearance of a scanty basis, but it is considered preferable to aver-
aging together a larger number of trees which would introduce varia-
tions, the effects of which could not be determined. The results are
given in Table 11. |

TABLE 11.—Felative response of yellow pine and white fir.

|
Yellow pine. | White fir.
; 3,
Annual basal Annual basal
Plot. Aver- | area growth. Aver- | area growth.
Num | age di- Accel- | Num- | age di- Accel-
ber of | ameter eration. | Det of ameter anes
trees. | breast ‘| trees. | breast ,
high. | Before.| After ; high. | Before.| After.
PACE NAPs et Spee Cee Pech: | each | eer
Snastaesee aes se ss: 20 20.6 0. 53 0.83 | +56.6 9 12.7 1.39 1. 48 +6.5
anOO--3- 255 se =. ee 25 18.9 a ee 9 1. 46 27.0 11 17.4 3. 67 4, 20 14.4
iblamasse t= ss ee 5 32 18.1 1.15 1. 34 16.5 6 11.4 2. 09 2. 48 18.7
Stanislaus-2......... 31 20. 0 1.73 1. 87 8.1 11 18.1 3.65 3. 87 6.0
Sierra. ie less. 222% 13 15.8 1.93 3.19 65. 3 8 15.8 2. 25 4. 26 89.3
Stanislaus-1......... 7 18.5 1.70 3.48 | 104.7 8 12.3 5. 53 Hei! 32.2

In every case white fir has grown at a much higher rate than yel-
low pine, but the relative increase after cutting was greater in only
two of the six cases.

With increasing age the percentage of acceleration, as well as the
absolute rate attained after cutting, decreases.

Suppressed trees growing at a slow rate show relatively greater
response to cutting than those which were always dominant, al-
though the rate attained may be much less.

RESULTS OF CUTTING IN THE SIERRA FORESTS. 15

Trees with large, well-formed crowns and dense foliage respond
more promptly (usually during the first season after cutting) and

attain a higher rate under the stimulus than trees with small, poorly

formed crowns in which response is usually delayed from one to
three years. Response is greater and more prompt on good than
on poor sites. The maximum rate is attained in 7 to 10 years
after cutting, but the stimulation is discernible for many years, de-
pending on the rate of closing of the crown canopy, invasion of
brush, etc. A heavy cutting, good distribution, and careful selection
of remaining trees are necessary to secure the greatest response.

NET GROWTH.

Statements in the preceding discussion have been largely in terms
of potential rather than net growth rates, in order to demonstrate
more clearly the effects on growth of the factors mentioned. It
may be of interest to consider what the actual net returns have been
from the areas under consideration. This may be seen from Table
12. The Feather River, Sequoia—4, and Tahoe plots represent ex-
amples of the reduction of net increment by- the loss of a few large
trees. On the better sites net growth has been excellent, amounting
in some cases to over 400 board feet per acre annually, or more than
o per cent.

TABLE 12.—Stand, losses, and net increment per acre, 1911 to 1921.

Net annual in-
Stand. Annual loss. crammont.
Site. Plot. Type.
Trees, 4 | Volume, Board
inches board Trees. | Volume. feat. Per cent.
up. feet. og ea
Per cent. | Per cent.

III Sy AE ee Mixed... 83.9 6. 500 0. 33 0.06 60 0.92
We. Phasit-07.2- 2... 5.--|-s< G022.5- 54. 4 9, 880 .53 36 53 54
iit Jiclit es ee aa JP-WF1 23.1 15, 520 . 80 . 68 53 . 34
JUSS GS oct Mixed... 51.5 10, 065 28 ook 130 1.29
II Feather River, 1-8...-.-.}..- dor... (Be 20, 000 - 83 . 00 76+ oo
II+ | Stanislaus-2............. SP-YP 1 38.4 18, 570 . 46 Splat 265+ 1.43
ie Stanislaus—3.... 5. -52----|- == dost: 37.7 24,100 . 87 . 26 225 93
II SEQUOIN=3 =< = S552 55. - MPa 53.3 10, 870 . 83 85 200 1. 84
I DIMNESee obo. sone’ Jen caecele es dois: 34.5 11, 350 .10 22 294 2.59
I SOS 1 at ee ee SP-WF. 51.8 12, 930 81 63 325 2.51
I Pequorw—to.= 2-< 1 2 ss: SP-YP. 45.5 21,710 cb7 . 60 80 37
I pequoia-6.< 32... ..-~-..-- 2 ee 32.7 12,700 Ase eee ee 440 3.46
I Dtanislaus=le 2. 2232.25. SP-WF 62.2 20,780 1. 46 Sule 470 2.26
BPR OSLO sae ees a BA ee 49.4 14,998 61 .39 205 1.3%

1JP=Jefirey pine; W F= white fir; SP=sugar pine; Y P= yellow pine.
INJURIOUS AGENCIES.

Loss in number of trees, averaging 0.61 per cent annually since
cutting, seems rather high, but it is due to the fact that most of the
trees were small, occasioning but. slight volume loss, and died during
the first few years after cutting from injuries received during brush
burning and logging. Other causes of loss, principally among small
trees, were snow, suppression, and, in white fir, engraver beetles
(Oecoptogaster). The greatest volume losses were due to wind and
bark beetles (Dendroctonus) in yellow pine, and to mistletoe in
Douglas fir on the Shasta plots, the latter being the only case of seri-

16 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE.

ous volume loss. From Table 12 it will be seen that volume losses
have never exceeded 1 per cent and have averaged 0.37 per cent an-
nually. Since windfall and deaths from other causes are usually
heaviest during the first five years after logging (true, thus far, of
practically all the areas included), this rate should decrease th the
ieure, 2{(Pl. I.)

Economic conditions at present do not permit the removal of all
defective material, and in consequence there are on these plots a
number of trees showing the effects of mechanical injuries, or attacks
by pathogenic organisms, some of which reduce growth. Probably
the most serious of these is mistletoe. This subject early received
rather careful consideration in marking, so that most of the trees
seriously attacked were removed. Excepting the above-mentioned
case of Douglas fir on the Shasta, mistletoe damage is largely con-
fined to attacks of the lower limbs of white fir and yellow pine by
tazoumofskya and of the tops of large decadent white firs by a
Phorandendron. Pearson, in the Southwest, has shown that a con-
siderable infestation of mistletoe reduces growth to a marked degree.

On timber sales made before the advent of the sanitation clause in
the contracts there remain considerable numbers of old unmerchant-
able white firs and incense cedars affected with fungi. These trees
are growing slowly, probably due as much to advanced age as to the
fungi, most of which attack the heartwood only.

Even large mechanical injuries, such as basal logging and fire
scars, have not been found to reduce growth except in smaller trees,
which are practically girdled.

Increment borings show that injuries, such as scorching away part
of the foliage by brush-burning fires, raking off of green limbs by
falling trees, or broken tops, are always evidenced by reduction in
the width of the annual rings made during the years immediately
following logging, in proportion to the amount of foliage destroyed.

The dense cover of shrubs which, owing to the open character of
the stands, frequently grows to the bases of the larger trees, un-
doubtedly reduces the amount of soil moisture available and conse-
quently their rate of growth. While this fact is usually conceded,
the extent to which it is true has not been determined.

VALUE OF INCREMENT.

So far we have been considering the disadvantages of a heavy
stand after cutting as regards volume increment without regard to
quality. There is considerable justification for leaving a certain
amount of large, high-cuality material for value increment, where
the stand will be accessible for a second cut in a reasonable time, but
great care should be exercised in selecting trees to be reserved for
this purpose. The following figures, although they do not represent
the method of determining national forest timber-sale policies,
indicate that a profit will result from such stand unless unexpected
wind or insect damage occurs.

The valuation of the stand left on the Stanislaus plot 3 at the time
of cutting, assuming a second cut in 30 years, would be:

Sale value of timber at time of cutting, $45.20 per acre.

Value of timber at end of 30 years, with compound interest at 3 per cent.
$109.71.

“4YSO1O,T TOUOTIVN SBVUINTA *4S8010
oy} oAOGK Surpoofoad suMOID MOY) YM 9sptt 1doMs-puUrA v JO OPIS 99] OY} UO SAvdS OIG AC POUOZLOAM Soot] PUv Soot) T[e1 AIOA SULAVOT WHOA, Surppusoa TpeypurAy

PLATE

Iture.

Icu

of Agr

Dept.

S

U

1176,

Bul.

Bul. 1176, U. S. Dept. of Agriculture. PLETE le
if
{
|

Fic. 1.—Heavy cutting on private land on Site J, effective in releasing the abundant advance
growth of sugar pine and white fir. Sierra National Forest. q

Fic. 2.—A good stand of yellow pine reproduction present as small seedlings prior to cutting,
which grew rapidly and became conspicuous after release. Note condition of slash 11 years
after cutting with no disposal, no fires, and moderate sheep grazing. Plumas National Forest.

Bul. 1176, U. S. Dept. of Agriculture. PLATE III.

Fic. 1.—An accidental stand of yellow pine reproduction on a north slepe due to abundant
seed ripened the year of cutting, following a hot slash fre cf the same season. The fire was
followed by favcrable conditions for germination and growth. Private lands within the
Sierra National Forest.

Fic. 2.—South slope of same ridge where, with similar treatment, less favorable conditions
resulted in a stand of bear clover and manzanita instead of tree seedlings. Private lands
within the Sierra National Forest.

Bul. 1176, U. S. Dept. of Agriculture. PLATE IV.

Fic. 1—A group of trees left after cutting. Groups as dense as this do not permit reproduc-
tion, growth of the trees is seriously retarded, and they show little or no response to cutting
in the form of increased growth. Plumas National Forest.

Fic. 2.—Abundant advance reproduction of western yellow pine on an unfavorable site where
the condition of the natural stand resembles that which would be secured by a first cutting
under the shelterwood system. The primary object of cutting should be to release and
preserve such reproduction. Lassen National Forest.

ys tj

~-

fia deal

da

No aaes ama

Aa we
ik

4

ee

high quality stands.

.

RESULTS OF CUTTING IN THE SIERRA FORESTS. LT
6
Cost of brush-disposal at 30 cents per thousand for 28,560 board feet per acre
removed, or $8.57 at.3 per cent compounded for 30 years, $20.80: per acre.
Fire pervention and suppression, 30 years at 13 cents per acre annually,
with compound interest at 3 per cent, 71 cents.
Total investment in timber at the end of 30 years, omitting taxes and admin-

istrative charges, $131.22.
Since most losses on sale areas occur during the first five years
after cutting, we may expect a higher net annual growth rate for
the longer period of 30 years than the 0.93 per cent given above, so
it seems conservative to use a rate of 1 per cent annually. At this
rate the stand per acre at the end of 30 years would be 32,482 board
feet. With an investment. of $131.22, as determined above, the stand
would have to bring an average stumpage price of $4.04 per thousand
to earn 3 per cent on the investment.
As present (1922) stumpage rates for similar timber are $5 tor
sugar pine, $4.50 for yellow pine, and $1.50 for white fir and incense
cedar, more than twice what they were at the time of the above sale
10 years ago, it is readily seen that the Government may reasonably
expect a profit of over 3 per cent on the 30-year investment from such

REPRODUCTION.

In the forests of California, where expense generally prohibits
artificial regeneration, the question of securing natural reproduction
is of the first importance. Unfortunately, when this study was be-
gun, the securing of growth data was given first consideration and,
except in a few cases, only rather generalized reproduction data were
provided for. Since that time more intensive studies have been un-
dertaken, but have not yet yielded conclusive results. Only the more
obvious facts developed will be mentioned and no attempt will be
made to explain them.

One of the most important results of these studies has been to
emphasize the great importance of advance reproduction. It be-
comes more and more evident that the establishment of reproduction
after cutting is a long, tedious process, requiring as high as 20 years
or more on poorer sites to secure even a fair stand. In none of the
sample plots even on the best sites has more than one-third of the
seedlings now present been established since cutting, and in only two
cases are the number and distribution of seedlings sufficient to con-
stitute complete stocking 10 years after logging. That this condi-
tion is not exceptional is evident from examination of many of the
more important cut-over areas in the State. With very rare excep-
tions the large number of seedlings now found on cut-over areas was
present under the original stand, or developed from seed borne by
trees during the season of felling.

Investigation of the excellent stands of seedlings often pointed out
on clear-cut or heavily-cut areas in support of the argument that this
is the proper method of securing good reproduction, practically al-
ways discloses the fact that the majority of seedlings were present
as very small inconspicuous trees at the time of cutting, and that the
removal of the older stand was exactly what was needed to release
them. Their sudden advent was apparent, not real. (PI. IL.)

Some remarkably fine stands of yellow-pine reproduction have be-
come established by a rare combination of circumstances, such as an

18 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE.

abundant seed crop ripened during the season of felling, stirring up
the soil by logging, a series of favorable seasons fgllowing germina-
tion, and the miraculous escape from slash fires. (PL IT) Ob-
viously such stands can not be counted on regularly in practice.

The reasons for the failure to secure at will abundant reproduction
of desirable species are not so evident. In most cases at the time of
cutting advance growth is present in openings made by fire or insects,
and even directly under the more open, older stands. Investigation
shows that as a rule there is a great range in age of these seedlings, or
that they germinated abundantly during certain widely separated
years—that is, advance growth originated either by a long, gradual
process or by rare combinations of favorable circumstances.

The slow progress of restocking is brought out in tabulation (Table

13) of selected typical data, which shows the differences between
the number of seedlings present at two examinations of the same
area made at intervals of from 4 to 10 years. Advance growth or
reproduction which had become established before logging is in-
cluded. Examinations at intermediate periods have shown that some
seedlings start practically every year, but deaths due to drought,
rodents, and unknown causes almost or more than offset the number
of new trees. The conspicuous decrease in number on the Feather
River plots is due to the fact that the 1913 examination was made
prior to logging and brush burning and included seedlings of ae
current year’s germination, in which mor tality is always high, ¢
condition not true of the other plots. Certain changes in Gena
make comparison with the earlier examinations in most cases rather
difficult, and they have been omitted, but the general trend or results
would be the same.

TABLE 13.—Progress of reproduction, all species.

| }
Seed- Per cent |. Seed- | Per cent
Plot and date. lings per | of origi- Plot and date. | lings per | of origi-
acre. | al. acre. nal.
Shasta: Feather River 1 to8:
MQUOES Beso he AIS Sse 4,534 100. 0 ONS Brae ce eee tee cs 25, 366 100. 0
1920 see Be eee apa 4,165 91.9 LESS eee ie ae oh ee ee 5, 464 | 2
Tahoe: Sierra: |
191624 see a Ee ee eee 540 100. 0 19162 Se ee eer eee 9, 680 100. 0
DODD shee ase Sire pac Ca 493 | 91.3 192055 Saeco one 8, 544 | 88.3
Plumas: . Sequoia-l
TOVQ Hes fst) Seon nop eS 1,270 100. 0 LONG 2h en cease Sates 1,690 | 100. 0
LOD Sian s Ne ioe fee 1,352 106. 5 1G 20) FES eee eee eee | 1,690 | 100. 0

It was stated above that the stand of seedlings on most of the
plots was deficient. It might be assumed from Table 13, which shows
totals of 4,000 to 10,000 seedlings per acre on some of the plots, that
this was not true. It should be explained, however, that from 35 to
67 per cent of the reproduction is incense cedar, over half of which
consists of dense patches of small seedlings less than 6 inches high.
Only a very small portion of this will ever reach large size.

The reasons for this slow progress in restocking will not be dealt
with at length, because lack of sufficient meteorological, seed crop,
hght intensity, and other data at present restricts the discussion to
generalities of slight interest. Briefly, there are several outstanding

RESULTS OF CUTTING IN THE SIERRA FORESTS. 19
e

reasons to which failure is attributed. On the poorer sites it is

probably due primarily to drought and infrequent seed crops and on

the better sites to infrequent seed crops, abundant brush and ground

cover present before cutting, and light cuttings where the original

stand was heavy.

In what way could changes in marking affect these factors? On
most of the older sales enough, and in some cases too many, seed
trees were left on the poorer sites, but what effect a heavier cutting
would have on amount of seed borne is unknown. Apparently trees
on the sale areas bear more seed than similar trees in adjoining
virgin timber, and as on these poorer sites, particularly on the east
slope of the Sierras, brush invasion is slow in the absence of fire, a
heavier cutting leaving only well-distributed, well-formed, frequent
seed trees, as at present, seems justified. Grouping of reserved trees
should be avoided. (PI. IV.) As to modifying the effects of
drought, there is doubtless a compromise between some method,
such as the shelterwood, designed to prevent soil deterioration and
loss of soil moisture by evaporation, and clear cutting, which makes
more soil moisture available to seedlings by reducing root com-
petition of the older trees but encourages heavier herbaceous and
shrubby undergrowth. ‘This matter is still an open question. On
poor sites some cover doubtless favors the establishment of repro-
duction. On the Plumas plot over 90 per cent of the seedlings are
situated in patches of squaw carpet which covers only about 20 per
cent of the area. This plant (Ceanothus prostratus) forms dense
flattened mats which protect seed from rodents, act as fire barriers,
probably reduce frost damage, and prevent excessive evaporation
during the early season when seed is germinating, thus favoring
establishment. Apparently root competition later results in slow.
growth of the seedlings until sufficient shade is provided to kill the
shrub.

On the better sites, in addition to the question of seed supply, the
control of brush and ground cover assumes greater importance and
offers a particularly difficult problem. Until recent years uncon-
trolled fires, started by hghtning, Indians, miners, stockmen, etc.,
have favored the spread of many species of Ceanothus, manzanita,
bear clover (Chamebatia foliolosa), and other shrubs whose vigor-
ous sprouting and seeding capacities enable them to seize openings
to the detriment of reproduction. The lhght requirement of some of
these shrubs, notably Ceanothus cordulatus, Prunus emarginata,
Castanopsis chrysophylla, and Chamebatia foliolosa is nearly the
same, but lower than that necessary for yellow-pine reproduction.
In many cases the crown canopy is already sufficiently open to permit
the shrubs to gain a foothold before logging, so that no choice is left
but to risk their extension by cutting the timber. That the brush
does spread appreciably following cutting is evidenced by .photo-
graphs taken at intervals from the same point. Under intensive
management this underbrush might be grubbed out and the space
replanted with trees, a course not open at present because of exces-
sive cost. Seedlings gradually become established in even the densest
brush (especially is this true of white fir), and, after severe competi-
tion for soil moisture for a time, overtop the brush and shade it out.
(Pls. V and VI.) Several instances are known where this has hap-

20 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE.

pened in less than 30 years. Apparently, for the present, we must
depend on this process with fire protection fr control of brush al-
ready present.

Heavy litter is definitely known to favor fir and cedar at the ex-
pense of yellow pine. Heavier cutting in the yellow pine, the sugar
pine-yellow pine, and the ee pine-fir types with better distribution
of reserved trees undoubtedly favors pine reproduction and is espe-
cially necessary to release advance growth.

In most cases the period required for natural regeneration will
range from 10 years on the best to 20 years or more on the poorer
sites. Bearing in mind the character of the virgin forests in which
the best advance growth is found, an extensive application of the
shelterwood system seems to offer the best chance of improving on
conditions existing at the time of cutting. It is particularly adapted
to the fir and sugar pine-fir types if an increasing proportion of fir
is accepted as unavoidable. It was stated previously that most of
the early cuttings inadvertently resembled shelterwood cuttings.
How, then, are the unsatisfactory results explained? In the first
place, sufficient time has not elapsed. Few good stands of reproduc-
tion can be found in which all seedlings have been established in less
than 10 years, except on the best sites or where a good seed crop has
been followed by favorable seasons.

In the eee ed place, the system was not definitely in mind at the
time of marking, and improper application of it resulted. Seed. cut-
tings were made where the presence of advance reproduction justified

heavier removal cuttings. Even markings intended for seed cuttings

were probably too light. On the other hand, some later very heavy
cuttings, where advance growth is scanty, and which have left only
three or four thrifty standards per acre for seed trees, will probably
result in slow regeneration, as such trees bear little seed for a number
of years after cutting. (Pl. VII.) In many cases in which the stands
are essentially even-aged to start with, a heavy shelterwood cutting
would be practically the same, as the present system of leaving a
greater number of seed trees and at the same time a volume of 4, 600
to 10 000 feet board measure per acre for increased growth and im-
pr oved quality of the second cut. (Pl. IV.) The principal objection
to this system is that even two cuttings within a reasonable period
are not possible on most areas for economic reasons. Even to-day,
however, it would be possible to cut over a second time several sale
areas on the Plumas and other national forests.

Fortunately, in nearly all cases considerable advance reproduction
is already present and every effort should be made to preserve it and
favor its growth. In the early markings not enough attention was
given to such advance growth, especially if of small size or composed
largely of fir and cedar. The aim was to secure a new crop. The ad-
vance growth was given little protection in felling, yarding, and
brush burning, with the result that in some cases much of it was de-
stroyed. In others it remained suppressed by trees left for seed. An
extreme case of this is represented by the Massack plots above, where
the number of seedlings present now represents only 21.5 per cent of
the 25,000 or more per acre before logging, and much of what remains
is still suppressed. The present policy of heavier cutting and better
distribution of reserves is again indicated. (Pl. VIIL.)

Sra ae

Bul. 1176, U. S. Dept. of Agriculture. PLATE V.

Fie. 1.—Dense bear clover which hinders the establishment and retards the early growth of
reproduction. Nevertheless numerous white fir seedlings may be seenin it. Sierra National
Forest.

-

Fic. 2.—Same location five years later. White fir gradually overtopping the bear clover.

Bul. 1176, U. S. Dept. of Agriculture. PLATE VI:

Fia. 1.—Good marking has resulted in excellent reproduction of yellow pine on Site I after
cutting. While the seed tree is approaching maturity it is still thrifty and is justified by
prompt abundant seed crops which a smaller tree would not produce. Sierra National
Forest.

Fic. 2.—Same location five years later, showing rapid growth of seedlings which will soon
occupy the soil to the exclusion of bear clover and manzanita.

Bul. 1176, U. S. Dept. of Agriculture. PLATE VII.

Fic. 1.—A shelterwood cutting in Jeffrey pine on Site III, where 20 years or more may be
required before reproduction becomes established. Tahoe National Forest. |

Fic. 2.—A heavy cutting where advance reproduction is absent. It is doubtful if so few
reserved seed trees of this size and age can furnish enough seed for regeneration under
prevailing unfavorable conditions.

Bul. 1176, U. S. Dept. of Agriculture. PLATE VIII.

Fie. 1.—Mature stand of western yellow pine. Reproduction and intermediate sized trees |
practically absent. Some large trees should be reserved from cutting to insure a seed
supply. Lassen National Forest. |

Fic. 2.—A heavy stand of mature trees left on a timber-sale area in the sugar pine-fir type in
accordance with the practice of several years ago. A heavier cutting would have been
more favorable for reproduction. Sequoia National Forest.

—:

2
RESULTS OF CUTTING IN THE SIERRA FORESTS. Of

The method of brush disposal practiced has a very important in-
fluence on advance growth. Where piling and burning is done the
area covered by the piles, even with careful burning under ideal
conditions, is considerable. On the 24-acre Plumas plot in the mixed
coniferous type, yellow pine predominating, from which a cut of
13,480 board feet per acre was removed, the number of piles per
acre was 24 and the percentage of the area covered by closely con-
fined brush-burning fires was 6.7. On a more recent sale area of
the Lassen National Forest, pure yellow pine type, from which an
average of 17,500 board feet per acre was cut, the number of piles
indicated by a strip cruise was 20 per acre, which covered 6.2 per
cent of the area before burning and 9.2 per cent after burning. A
more extensive airplane photographic survey of the same sale area
gave an average of approximately 15 piles per acre, or 6.7 per
cent covered by fire. This was with careful burning under
favorable conditions. The period during which satisfactory brush
burning can be done is usually short, and frequently fires spread
much more than indicated above. On the eight Feather River plots,
where the average cut was 34,770 board feet per acre, brush-burning
fires covered 8 to 17 per cent of the area. With careful supervision
piles can be placed away from reproduction, so that the area burned
does not necessarily mean proportionate destruction of advance
growth. The areas covered by the fires are rendered unfavorable to
establishment of seedlings for several years. Formerly practically
all piles were burned, regardless of proximity to advance growth,

but it is customary now to leave 10 to 20 per cent of the piles where

their location close to clumps of seedlings is unavoidable. Careless
piling and burning may result in great damage, particularly with
donkey logging, where the seedlings which escape yarding are left
in narrow sectors between the skidding trails radiating out from the
lead block. Slash and other débris is likewise pushed aside into
these same sectors by incoming logs. If the brush pilers merely heap
the trash up where it is found, burning may easily destroy what
reproduction escapes logging.

The piling and burning method of brush disposal was adopted
because of the extreme difficulty of controlling slash fires, the un-
certainty as to the effect of slash on increasing insect depredations,
and the belief that in most cases new reproduction could be secured
easily. We have long realized that the most abundant and thriftiest
young growth in this region is found in areas where abundant ad-
vance growth was fully released by a heavy cutting, no slash disposal
was practiced, and the area accidentally escaped fire, rather than on
areas where new reproduction was established after cutting. Ex-
perience has shown that there is slight danger of the spread of bark
beetles due to slash. (This is true’ at least. of Dendroctonus, al-
though the less destructive 7ps may spread under certain condi-
tions.) ‘The expense is a serious factor. There remains, then, only
the reduced fire hazard to justify the method. The Forest Service
has hesitated to change its method until it is certain of the results
or can find a more effective substitute. Modified methods whereby
slash is cleared from control lines separating the areas into natural
protection units are now being tried out on a large scale, with the
hope that, combined with more intensive fire protection, they will
give better results at less cost.

22 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE.

The effects of different methods of logging on advance reproduc-
tion will not be discussed in detail. Briefly; big-wheel and other
types of horse logging are the least destructive. Power logging
with a ground lead over extensive chutes, as generally practiced
several years ago, caused only moderate damage. With present
ground-skidding methods damage can be kept within reasonable
bounds. The method of high lead logging, generally used during
the last three of four years on private land, where the lead block is
placed on a spar tree from 75 to over 100 feet from the ground, as a
rule precludes dependence on advance growth for restocking. This
method is only justifiable on extremely difficult topography or where
subsequent planting can be done.

The effects of grazing upon reproduction on the areas under con-
sideration have been shght. Sheep are excluded from all of the plots
and grazing by cattle has been light.

As stated elsewhere, one object in practically all the older mark-
ings was to increase the proportion of the more valuable species,
yellow and sugar pines, in the next stand. It was hoped that this
would be accomplished by leaving abundant pine seed trees and
marking white fir and incense cedar as closely as economic condi-
tions would permit. It may be definitely stated, however, that in 10
years’ time such markings have failed to show any progress toward
the desired result. Repeated counts rarely indicate any great change
in the ratio of the species present, and what changes have occurred

are generally in favor of the fir and cedar. This relation is best:

expressed in Table 14.

TABLE 14.—Changes in composition of reproduction by species.

[Number of seedlings per acre and per cent of total.]

Yellow

pine.

. Thi Incense
Sugar pine. | Douglas fir. | White fir. aaa Total,

Plot and date.

Num-| Per |Num-| Per | Num-} Per | Num-}| Per | Num-} Per | Num-| Per
ber. |cent.| ber. |cent.| ber. |cent.| ber. |cent.| ber. | cent.| ber. | cent.

Shasta:

tO) eae ee 1,587 | 35.0 9} 0.2 674 | 14.9 247 | 5.4 | 2,017 | 44.5 | 4,534 100

1 COA. 0 Spey i 1,273 } 30.5 12 .3 745 | 17.9 237 | 5.7 | 1,898 | 45.6 | 4,165 100
Tahoe:

1OUG Sere aes 195) OGe 1. hese seek ee le coe peeeee BED NOOBS ON Mate oel eee 540 100

POQOEY SPY Bip ek 170} edd: Sales she eee | eee eee BURN) Oseesalle sage eae © 493 100
Plumas

NOLOS ee ee eee 2c 330 | 26.0 Ale | 352 96 | 7.6 123 4) 3937 680 | 53.5 | 1,270 100

O20 ses fates oe 366 | 27.1 38 | 2.8 85) 26538 120 | 8.9 743 | 54.9 | 1,352 100
Feather River 1 to8:

Sete Lees 2,500 | 9.9 | 1,256 | 5.0 | 6,392 | 25.2 | 5,288 | 20.8 | 9,930 | 39.1 |25, 366 100
ee OL eae ee 578 | 10.6 333 | 6.1 | 1,161 | 21.2 | 1,315 | 24.1 | 2,077 | 38.0 | 5,464 100
ierra ;

1916. F255 ote 1,985 | 20.5 Ee lee OT aaa eS MODs iis) | 6, 5352\\ Ofzon| oy O80 100

MOZ0E 2 Soe. Sao ass 2,098 | 24.5 ANT) (4. oe sealers 766 | 9.0 | 5,263 | 61.6 | 8,544 100
Sequoia

LONG 5 ees oe selectors bees & 490 {):29\0s\e ae eae eee oe 600 | 35.5 600 | 35.5 | 1,690 100

TODOS Eee ale cae eee oS 520 SOK Se seca ene 580 | 34.3 590 | 34.9 | 1,690 100

From what has been said before in regard to securing reproduc-
tion after cutting, this result might be anticipated. The composi-
tion of the new stand is predetermined in the advance growth, which
in general resembles the original stand. The single cutting possible
resulted in only shght modifications in composition. Doubtless

2

RESULTS OF CUTTING IN THE SIERRA FORESTS. a3

heavier cutting than took place on most of these sale areas would
have favored the pines in the small amount of reproduction which
actually did come in, because both shade and litter may be so heavy
as to exclude sugar and yellow pines where incense cedar and white
fir come in abundantly.

Another reason for this failure to secure the expected change in
composition was that early markers did not give sufficient considera-
tion to the natural succession of tree species. Where natural con-
ditions of site favor white fir, which is generally true of Sites I and
II on north and east slopes, this species is destined to succeed yellow
pine unless the normal succession is disturbed by fire or other acci-
dents. Fir seeds more abundantly than pine germinate under
stands of yellow pine, whose litter and shade exclude their own
seedlings, and the young trees endure suppression longer. More-
over, height growth of fir is more rapid, and the total height
attained is greater than for yellow pine. Im the past occasional
fires have been primarily responsible for sustaining yellow pine on
fir sites. Fir seedlings and young trees are far more susceptible to
fire damage than the pine because of their thinner bark with balsam
eysts, more inflammable foliage, and small resinous terminal buds
which are far less resistant than those of yellow pine. The fir is
more often eliminated by fungi entering through fire scars than is
pine. Exposure of mineral soil and openings created by fire favor
yellow pine. .Striking examples of the succession of white fir with
fire exclusion may be seen in many places, notably on the Lassen
National Forest, where the mature stand is composed of practically
pure yellow pine, while the reproduction beneath it is over 90 per
cent white fir.

Although incense cedar reproduces abundantly under the same
conditions as white fir and is equally or more tolerant, its slow height
growth prevents it from becoming anything but a secondary species
in the final stands.

Leaving out of consideration, for the present, the possibility of
using fire to maintain pine in the stands as inefficient and wasteful
if practicable at all, there remain open only two courses—fir must
be accepted on fir sites or planting of other species must be resorted
to. The first course is the only one regarded as feasible at present,
and from what has been said about growth and the trend of market
conditions for possible fir products, it is not at all discouraging.

Under certain conditions, not uncommon, planting may be not only
the logical but the most economical method, in the long run, for the
Government. On Sites I and II, where rotations would be less than
75 years, planting would result in a yield of 50,000 board feet or
more per acre of desirable species. Where advance reproduction is
deficient and young trees for reserves are few, clear cutting could
be practiced, permitting logging to proceed as cheaply as possible,
destroying inferior trees and brush, and concentrating slash in piles
and rows, thus obviating expensive brush disposal. Areas treated
in this way could be planted successfully for $15 per acre.

Present methods of securing natural reproduction on the national
forests involve leaving at least 5 seed trees, averaging 20 inches in
diameter, per acre, an investment of about $8. The interest on this
amount is chargeable to the final crop, provided the trees themselves

94 BULLETIN 1176, U. §. DEPARTMENT OF AGRICULTURE.

survive. Additional cost of logging to protect geed trees and advance
growth is roughly 75 cents per thousand for slash piling and burning,
snag disposal, and additional blocks, bushing, etc., to protect trees
from lines, or, for a cut of 20,000 board feet, about $15 per acre.
These costs are really borne by the Government in reduced stumpage
rates. Natural reproduction, as compared with planting, will in-
crease the rotation by 10 or more years. Comparing the two methods
on a financial basis, disregarding taxes and administrative charges,
and using the same rate of interest in each case for the respective
rotations, the ultimate costs are much in favor of planting. At
present the planting of such areas is inconsistent with the nation-
wide policy of the Forest Service which gives first consideration to
completely denuded areas where lack of seed trees makes even slow
natural regeneration impossible and to areas where rapid growth
and good markets will insure quickest returns.

SUMMARY.

Site is the most important factor in the growth of stands left after
cutting. On Sites I and II a reserve volume of 6,000 to 10,000 feet
board measure is justified for increased growth and improved quality
of second cut. By proper selection of reserves a net growth of 24 to
3 per cent annually can be maintained for at least 10 years after cut-
ting. On Site III, or poorer, silvicultural considerations indicate
marking aimed to secure reproduction. Other considerations, how-
ever, do not permit the uniform application of these principles.

White fir ranks first in rate of growth, followed by sugar pine,
Douglas fir, yellow pine, and incense cedar. ‘Sugar pine maintains a
high rate of growth to a greater age or diameter limit than the other
species. On Site I, or better, indicated diameter limits are roughly
30 inches for sugar pine, 26 inches for yellow pine, and 24 inches for
white fir and incense cedar. Corresponding ages range from 150 to
200 years in present stands.

In selecting trees to reserve for increased growth the best results
will be obtained from trees free from defects, with the color and tex-
ture of bark characteristic of immaturity, pointed tops, dense dark
green foliage, and crown length equal to 60 per cent or more of the
total height.

Leaving trees in groups neutralizes the effects of cutting and dis-
criminates against pine reproduction.

The greatest response to cutting can only be secured by heavy
marking, proper distribution, and careful selection of reserves ac-
cording to the foregoing statements. Response is greater and more
prompt on good sites and where cutting frees both root and crown.

The net rate of volume increment for stands averaging about
15,000 board feet per acre for Sites I to III has been from 53 to 470
board feet per acre annually, or 0.34 to 3.46 per cent. Loss by death
has averaged 0.37 per cent annually.

Except on Sites I and II, in 10 years’ time there has been no appre- —

ciable increase in the amount of reproduction on early sale areas cut
over lightly by the group selection and shelterwood methods. A
regeneration period of from 5 to 10 years on Site I and of 20 or more
years on Site III may be expected.

RESULTS OF CUTTING IN THE SIERRA FORESTS. yrs

The favoring of yellow pine and sugar pine by leaving abundant
seed trees of these species and marking white fir and incense cedar
closely has resulted in no change in composition, because few new
seedlings of any kind have come in; there always remain enough
unmerchantable firs and cedars to supply abundant seed; hght cut-
ting, heavy litter, brush, and ground cover favor fir and cedar; and
on certain sites, if fire or heavy cutting are excluded, fir naturally
succeeds pine. |

Attempts to control brush and ground cover by marking methods
without eradication or planting are not successful, because the nat-
ural stands are already sufficiently open to permit survival of many
shrubs where yellow-pine reproduction is excluded. Cutting of any
kind favors extension of the brush. With fire protection, suppres-
sion of such shrubs depends, for the present, on the slow process of
competition by which the brush is overtopped by the tree seedlings,
especially those of white fir.

Marking designed to promote natural regeneration should give
primary consideration to existing advance reproduction. Cutting
should be as heavy as management restrictions allow in order to
release it. Every precaution should be taken in felling, yarding,
and brush burning to preserve it. Its presence will shorten the
rotation 5 to 20 years or more.

Brush disposal by piling and burning results in covering by fire
at least 6 to 10 per cent of the area, on which a considerable number
of seedlings and saplings are destroyed, and costs from $8 to $10
per acre. Leaving slash rarely induces insect infestation. Cleared
control lines with intensive protection may ultimately supersede
piling and burning of slash.

The best advance reproduction in nature has occurred under con-
ditions resembling a shelterwood system. When reproduction is
absent and the stand essentially even-aged, a heavy shelterwood, or
a seed-tree cutting, leaving numerous well-distributed seed trees
preferably larger than 18 inches, will combine the most favorable
conditions for improved growth and reproduction. In irregular
stands a heavy selection cutting, removing 75 to 80 per cent of the
volume, and avoiding grouping of the reserved trees as much as
possible, promises to give the best silvicultural results. Each acre
is a problem in itself and much depends on the marker’s ability to
recognize the character of the site, the mature stand and reproduc-
tion requirements, and to apply the right silvicultural principles as
a part of the broad marking policy by which he is guided.

REFERENCES.

CArTER, E. E. Silvicultural results of marking timber in the national forests.
Proc. Soe. Amer. For., Vol. III, p. 18, 1908.

CHAPMAN, H. H. Development of a brush disposal policy for yellow pine
forests of the Southwest. Jour. For., Vol. XVII, p. 693, 1919.

CLAPP, E. H. Silvicultural systems for western yellow pine. Proc. Soc. Amer.
For., Vol. Vil, p: 168, 2912.

DuNNING, D. Relation of crown size and character to rate of growth and re-

sponse to cutting in western yellow pine. Jour. For., Vol. XX, No.
4, p:. 37921922.

I’ROTHINGHAM, E. H. Classifying forest sites by height growth. Jour. For.,
Vol. XIX, No. 4,-p. 374, 1921.

——=. Height growth as a key to site. Jour. For., Vol. XVI, No. 7, p.. 154,
1918. '

— —.. Site determination and yield forecasts in the southern Appalachians.
Jour... or., Vol. XEX,- Noe: bp a eee

GALLAHER, W. H. . The Himalayan forests. Proc. Soc. Amer. For., Vol. VIII,
Wo: 3, .Ds oo0;.2015.

HawteEy, RAtpH C. The practice of silviculture. John Wiley & Sons, New
York, 1921.

HoppinG, RALPH. The entomolegical aspects of slash disposal. Proe. Soe.
Amer. For., Vol. X, p. 183, 1915.

JARDINE, J. T.. Efficient regulation of grazing in relation to timber production.
Jour. For., Vol. XVIII, p. 367, 1920.

KocuH, Evers. The economic aspect of slash disposal. Proc. Soc. Amer. For.,
Vol. TX, p. 356, 1914.

Lone, W. H. A new aspect of brush disposal in Arizona and New Mexico.
Proce. Soc. Amer. For., Vol. X, p. 383, 1915.

——. Investigation of the rotting of slash in Arkansas. U. S. Dept. Agr.,
Bul. 496, 1917. ;

MircHeELL, J. A. Methods and costs of brush piling and burning in California.
Proc. Soe. Amer. For., Vol VIII, p. 340, 1913. 5

Muncer, T. T. Western yellow pine in Oregon. U. 8S. Dept. of Agr., Bul. 418,
1917.

Nisset, John. Concerning the enhancement of increment which takes place in
the forest after heavy thinnings or partial clearance. London, 1893.

Pearson, G. A. Influence of age and condition of tree upon seed production
in western yellow pine. U. S. Forest Service, Cir. 196, 1912.

Rotru, Filibert. Concerning site. For. Quart., Vol. 14, No. 1, p. 3, 1916.

SmitH, Kan, and WEITKNECHT, R. H. Windfall damage in selection cuttings
in Oregon. Proc. Soe. Amer. For., Vol. X, p. 263.

SmitrH, P. T. A silvicultural system for western yellow pine in the Black Hills.
Proc. Soe. Amer. For., Vol X, p. 294.

SparHawk, W. N. Effect of grazing on western yellow-pine reproduction in
central Idaho. U.S. Dept. Agr., Bul. 738, 1918.

Watson, Russell. Site determination, classification, and application. Jour.
Hor. -Vok XN, Ne: 5,-p.- 502, AGU

WEIDMAN, R. H. A study of windfall loss of western yellow pine in selection
cuttings 15 to 30 years old. Jour. For., XVIII, p. 616, 1920.

WootseEy, T. S., jr. Marking western yellow pine. For. Quart., Vol. VII, p.
271, 1909.

Many manuscripts in Forest Service files on methods of cutting, growth, and
brush disposal by S. B. Show, R. H. Weidman, J. W. Lowdermilk,
G. A. Pearson, W. H. Gallaher, R. S. Maddox, S. W. Wynne, N. T.
Childs, E. G. Dudley, L. T. Larson, and D, Dunning.

26

ORGANIZATION OF THE UNITED STATES DEPARTMENT OF

AGRICULTURE.
Secretary of Agriculture____~ oe ee PEENEY Oo. -WAELACE:
MIRE SENT CLOT pt C.-W. PUGSLEY.
Director of Scientific: Work _______-_---_ 2 SH. 1D BATA.
Director of Regulatory Work____________
EE EE 2) ee CHARLES F. MArvIN, Chief.
Bureau of Agricultural Economics___—~—_—- Henry C. Taytor, Chief.
Bureau of Animal Industry___-------~~~. JOHN R. MoHLER, Chief.
Burcau of fiant Iindusiry___-____---_____. WILLIAM A. Tayutor, Chief.
rae sae? 280) a SS W. B. GREELEY, Forester.
Peeve ORCMASITY = + WALTER G. CAMPBELL, Acting Chief.
EE AOS Se a ee MILTON WHITNEY, Chief.
Eurcau of Entomology. + L. O. Howarp, Chief.
Bureau of Biological Survey____--__-____- KH. W. NELSON, Chief.
Pawetn of wollte toads. THOMAS H. MAcDonatp, Chief.
Fired Nitrogen Research Laboratory____- F. G, CoTTretyi, Director.
Division of Accounts and Disbursements_. A. ZAPPONE, Chief.
Division of Publications________________- EDWIN C. POWEL., Acting Chief.
J ee CLARIBEL R. Barnett, Librarian.
DMieceesChLIONS WET PiCce..-- =~ A. C. Tsaur, Director.
Wedenm Horteultural Board_.________—-— C. L. Mariatr, Chairman.
Insecticide and Fungicide Board_________ J. K. HAywoop, Chairman.

Packers and Stockyards Administration_|CHESTER Morrityt, Assistant to the
Grain Future Trading Act Administration_ Secretary.
Office of the Sovertor________ sage a a R. W. WILLIAMS, Solicitor.

This bulletin is a contribution from

DSB 2 8 5 ee ar W. B. GREELEY, Forester.
BYTOM eIeeCSCUrCh.. = 2. - fs ____. HARLE H. Cuapp, Assistant Forester.
Forest Investigations___________. J. KITTREDGE, Jr., Chief.

27

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