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 rent, in basal area of western yellow 
pine. 
Site. 
Plot. 
Num- 
ber of 
trees. 1 
Diameter classes 
(inches). 
12-17 
18-23 
24-29 
Ill— 
Shasta, 6 
288 
261 
306 
160 
33 
76 
0.78 
1.35 
1.52 
2.69 
3.27 
4.72 
0.62 
.90 
.98 
1.61 
3.00 
4.21 
0.45 
III 
Tahoe 
.67 
II— 
.70 
11+ 
1.29 
I 
.78 
I 
2.75 
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 ha sal area by species. 
Annual. Basis. 
White fir 
Sugar pine . . . 
Yellow pine. . 
Incense cedar 
Per cent 
2.22 
2.07 
1.50 
1.21 
Trees. 
463 
81 
156 
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. 
