26 BULLETIN 418, U. S. DEPARTMENT OF AGRICULTURE. 
An analysis of these tables brings out some interesting points. 
Rapid diameter and rapid height growth are by no means associated 
always; a stand may make a very good diameter growth and yet poor 
height development, particularly in some of the open stands in the 
dry situations bordering the desert. Sustained growth rate seems 
also to depend upon the character of the situation. Apparently 
the rate is sustained longest on the poor sites where it is the lowest, 
as though the tree were striving to reach certain dimensions bef ore- 
its increment slackened. 
The period of most rapid growth is reached early in the life of the 
tree. In all the 18 localities for which data are given above, the 
culmination of the annual growth in diameter takes place between 
the fortieth and the one hundred and fiftieth year, usually about 
the seventy-fifth year; in height growth, it takes place between the 
forty-third and ninety-seventh years, averaging about the sixty-fifth 
year. The culmination of the mean annual growth is of course later, 
and in these localities was found to be between the seventy-eighth 
and the one hundred and forty-fifth year (average 109 years) in the 
case of height growth, and between 80 and 190 years (average 120 
years) in the case of diameter growth. While the data are not wholly 
consistent, both the mean and the annual diameter and height 
growth culminate latest on the poorest sites. 
VOLUME GROWTH. 
No specific volume growth measurements were taken in the field, 
but the volume growth tables have been derived from volume tables 
and the diameter and height growth data. 
Table 11 indicates the average number of board feet in trees of 
various ages in several typical localities. It shows that in an unfavor- 
able site, such as that near Winlocks Mill, the trees do not come to be 
of merchantable size (12 inches in diameter) until 140 years old, 
and that it takes 200 years for a tree to have a volume of 280 board 
feet, and 300 years for it to have 900 feet; while on a favorable site, 
such as at Fort Klamath, the average tree becomes merchantable in 
80 years, and at 200 years contains 1,190 board feet. The culmina- 
tion of the annual and mean annual volume growth takes place, as 
would be expected, later than that of the diameter and height growth. 
The period of most rapid current volume growth (which may be 
derived from Table 11) falls variously from the one hundred and 
fiftieth year to the limit of the table, while the maximum mean 
annual volume growth usually occurs outside the limits of the table, 
500 years. 
