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 limited 
to first-quality sites and is composed principally of the two most 
rapid growing species, promises the highest yields under manage- 
ment. 
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. 
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 groicth, per cent, hi basal area, 
1910-1920. 
Speeies. 
Diameter classes (inches). 
Basis 
num- 
4 to 11 
12tol7 
18 to 23 
24to29 
30 to 35 
36 to 41 
42 up. 
ber of 
trees. 
6.45 
7.10 
9.70 
7. in 
3.30 
4.05 
5.30 
LOO 
2.20 
3.10 
3.30 
2.40 
1.50 
2.70 
2.00 
1 70 
1.15 
2.10 
1.50 
1.10 
0.90 
1.40 
1.20 
.80 
0.70 
.70 
1.00 
798 
Sugar pine 
716 
White fir 
1,131 
Incense cedar 
" 
