Trees grow more rapidly at low altitudes than at higher and cooler
elevations. Under similar conditions some species increase in size
faster than others, but the rate of growth depends principally upon
environment. The average increase at the stump in valley land is about 1
inch in 6 years. A Douglas fir growing along the stage road between the
park boundary and Longmire's, at the age of 90 to 120 years may have a
breast diameter of 20 inches and yield 700 feet of saw timber. But many
of the trees of this size may be much older on account of having grown
in the shade or under other adverse conditions. The trees between 200
and 300 years of age are often 40 to 50 inches in diameter and may yield
an average of from 2,700 to 5,500 board feet. The largest Douglas firs
are sometimes over 400 years old and 60 to 70 inches in diameter. Such
trees when sound will produce over 8,000 feet of lumber.
The western red cedar has a shorter and more tapering trunk and its
volume in board feet is proportionally smaller. A tree 50 inches in
diameter and 175 feet high contains about 3,400 board feet.
The size of the trees decreases rapidly at higher elevations. In the
subalpine forest the annual growth is very small. At elevations of 6,000
feet the white-bark pine requires 200 years to attain a diameter of 10
or 12 inches. The annual rings are so close together that they can not
be distinguished without a magnifying glass.