36 
BULLETIN 1437, U. S. DEPARTMENT OF AGRICULTURE 
Although individual trees growing in the open attain a maximum 
size of about 120 feet in height and nearly 4 feet in diameter, mature 
forest trees in the region of best development are usually from 80 to 
100 feet high and from 14 to 18 inches in diameter. The bole is 
straight, giving off rather slim branches which droop in a narrow, 
long, domelike crown. The thin-barked, smooth-looking, light ashy 
gray and whitish trunks are clear of branches for at least 20 to 40 
feet. The root system, as would be expected from the preference for 
moist soils, is shallow. 
Eed alder is a relatively short-lived species. Eighty years is an 
old age for this tree, and it may be said to be mature at about 50 
years. The maximum age recorded thus far is 101 years. In early 
life it grows very rapidly, more rapidly even than Douglas fir and 
the associated broad-leaf species. Owing to its early maturity, 
however, the species which are first surpassed by red alder later out- 
strip it; in fact, alder stands if left under natural conditions are 
likely to be replaced altogether by other species. 
Table 14 shows the diameter, height, and volume of alder trees 
at various ages, based on measurements of 115 trees in the Puget 
Sound region. 
Table 14. — Average diameter at breast height, average total height, and average 
volume of red alder trees of various ages x 
Age (years) 
Average 
diameter 
at breast 
height 
Average 
total 
height 
Volume 
25 
Inches 
10.2 
11.0 
11.9 
13.0 
14.5 
16.0 
17.3 
18.5 
Feet 
78.0 
81.9 
85.8 
89.7 
93.6 
97.5 
101.4 
105.3 
Board feet 
75 
92 
120 
167 
240 
335 
390 
430 
Cubic feet 
18 
23 
28 
34 
42 
52 
63 
75 
Cords 2 
" o 20 
30 
26 
35 
31 
40-.. 
38 
45 . 
47 
50 
58 
55 
70 
60 . . 
83 
1 Read from curves. Based on 115 tree measurements, Puget Sound region. Field work conducted by 
Forest Examiner A. A. Griffin. 
3 Cord assumed to have equivalent of 90 cubic feet. 
YIELDS 
Table 15 gives in board feet by the Scribner rule and in cubic feet 
the yield per acre in a number of even-aged red alder stands. The 
indication is that land cut over to-day and properly managed can 
be expected to yield 50 years from now not less than 15,000 board 
feet of saw logs to the acre with possibilities as high as 40,000 feet. 
The figures are based on measurements of 16 sample plots (13% 
acres) in typical forests in the Puget Sound region of Washington 
and the Coast Range of Oregon. Most of the plots were located at 
relatively low altitudes, ranging from sea level to 500 feet. The 80- 
year-old plots were at an elevation of about 1,800 feet. 
Tables 14 and 15 indicate the probability of an average annual 
growth per acre, on good sites, and after allowing for the loss of a 
certain number of trees through death, of 300 to 800 board feet up 
to 50 years. 
