RESULTS OF CUTTING IX THE SIERRA FORESTS. 
9 
Class 3. — Trees of any crown class having average-size crowns or 
larger, round 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 (5. 
Table 6. — Relative vigor of different classes of dominant trees. 
Tree 
class. 
Number 
of 
i rees. 
Annual 
basal 
area 
growth. 
Devia- 
tion 
from 
average. 
1 
2 
:; 
4 
209 
39 
77 
24 
Ihr cent. 
1.22 
.95 
.55 
42 
Per cent. 
+56.3 
+21.8 
-29. 5 
-46.1 
The relative response of such classes to cutting will be discussed 
later. 
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 slight 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 lo.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 avoided because damage 
results to remaining trees from logging. 
Many increment borings 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 1:2 and -24 inches 
in diameter. The number of trees included has been limited De- 
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 large trees were cut 
within 60 feet of them. 
49263°— 23- 
