ASPEN IX THE CENTRAL ROCKY MOUNTAIN REGION 
27 
aspen grows very slowly toward maturity. Conifers, on the other 
hand, maintain a rapid diameter growth to old age and put on 
their widest rings at diameters of 12 to 15 inches, at which time 
aspen stagnates and decays. 
Diameter growth for conifers as presented in Table 15 is in 
virgin stands of moderate density and probably represents a lower 
figure than would be obtained under forest management. This is 
of course true for aspen, though in a lesser degree. 
Table 15. — Diameter growth of aspen and associated conifers 
Diameter breast high 
Age 
Aspen, 
Site 2 I 
Douglas 
fir 3 
White 
fir 2 
Alpine 
fir* 
Engel- 
mann 
spruce 3 
10 years 
Inches 
0.8 
1.4 
2.4 
3.3 
4.3 
5.3 
6.4 
7.4 
8.4 
9.3 
9.9 
10.3 
10.8 
11.3 
11.8 
Inches 
Inches 
Inches 
Inches 
30years .... 
0.2 
1.7 
3.5 
5.5 
7.0 
8.5 
9.7 
10.8 
11.7 
12.6 
13.4 
14.3 
15.0 
15.7 
16.4 
17.1 
17.7 
18.3 
1.7 
3.2 
4.5 
5.9 
7.3 
8.7 
9.7 
10.8 
11.8 
12.8 
13.7 
14.6 
15. 5 
16.3 
17.1 
17.9 
18.7 
19.4 
20.1 
20.8 
21.4 
22.0 
1.7 
3.1 
4.5 
6.0 
7.7 
9.3 
10.5 
11.8 
13.0 
14.0 
14.9 
15.7 
16.5 
17.1 
17.6 
18.1 
18.5 
0.8 
50 years 
1.6 
2.5 
70 years 
3.4 
80years. 
4.3 
90 years 
5.2 
lOOyears 
6.2 
llOvears .... .... 
7.0 
120 vears 
7.9 
130 vears. 
8.6 
140 vears . . ..... 
9.4 
loOyears. .. .. . .. ... . 
10.1 
160years . 
10.8 
170 years ... 
11.5 
180 years 
12.2 
190 vears 
12.9 
200 years 
13.7 
210 years .. 
220 years 
230 years 
240years _,_ 
250 years 
i Heights (Table 13) converted into terms of diameters by use of diameter-height relation table (Table 
7). Does not agree with column 4 Table 16 because that table shows average diameter of entire stands 
(over 4 inches diameter breast height), while this shows individual trees. 
3 From stump ring counts made on Manti National Forest. Basis: 51 Douglas firs, 62 white firs, 24 
alpine firs. 
3 From Forest Service Circular 170, "Engelmann Spruce in the Rocky Mountains." 
VOLUME GROWTH 
Volume growth for individual trees is, of course, a product of the 
height and diameter growth. As diameter measurements include 
the bark, they tend to give conifers a certain fictitious advantage 
over aspen in diameter growth, and the development of solid wood 
in conifers is correspondingly slower than would appear from the 
diameter-growth table. The form of aspen is somewhat fuller- 
boled than conifers, which gives it another small advantage. For 
the quick production of large volumes of small wood in a short time, 
conifers can not compete with aspen on first-class sites (Table 16). 
