10 BULLETIN 1176, U. S. DEPARTMENT OF AGRICULTURE. 
Table 7. — Effects of grouping on basal area growth, per cent. 
Plot. 
Stanislaus: 
Released 
Left in groups 
Sequoia: 
Released.. 
Left in groups 
Before cutting. 
After cutting. 
Num- 
ber of 
trees. 
10 

5 
10 
!.-> 
years. 
years. 
years. 
years. 
years. 
16 
2.22 
2.26 
2.81 
2.63 
10 
1.71 
1.51 
1.44 
1.43 
13 
2.78 
3.20 
3.43 
3.32 
2. 55 
15 
3.30 
3.30 
3.59 
3.06 
2.59 
A ver- 
age in- 
or de- 
Per 
cent. 
+21.4 
-10.9 
+3.7 
-6.7 
The Sequoia area before cutting was already quite open, so that 
the cutting resulted in only slight changes 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 II, 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 III, 
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 lightness 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 growth 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, 
