96 THE ADIRONDACK SPRUCE 
TABLE 33 
THE RATE OF GROWTH IN DIAMETER OF 
ASSOCIATED SPECIES 
Average diam-| No. of years 
No. of trees eter of trees required to 
Species measured measured. | grow one inch 
Inches. in diameter 
Birch 12.5 
Beech 12.7 
Hard Maple 15.0 
Hemlock 16.6 
Balsam 10.5 
Soft Maple 10.5 
Knowing the number of trees of the small diameters 
and their rate of growth, it is possible to make a fair 
forecast of the future crops. It seems, however, that, 
in view of the fact that a large number of the Birch 
measured were very old, twenty years is too slow a 
rate of growth for the small trees, which would enjoy 
after the cutting a considerably larger amount of space 
than at present. Fifteen years seems to be a conserva- 
tive estimate for the rate of growth of young hardwoods 
from ten to fifteen inches in diameter, and this estimate 
is confirmed by observations made on the same species 
in northern Michigan. 
If the Birch and Maple are cut down to fifteen inches 
they will yield 3468 board feet per acre. Atthe end of 
