28 BULLETIN 418, U. S. DEPARTMENT OF AGRICULTURE. 
the reserved trees was found to be very large. On seven sample plots 
which were studied intensively it amounted to 310, 219, 242, 141, 103, 
63, and 48 per cent, respectively. On these areas the increase in the 
growth rate was in inverse relation to the volume of the reserved trees 
on the sample plot. Where there were many trees left standing there 
was less stimulation than where there were few. The acceleration 
in growth was also more noticeable where the reserved trees were 
evenly distributed than where they were crowded into groups. 
The measurement of a similar area in Klamath County lightly culled 
over some 24 years ago, on which u bull pines" and somewhat mis- 
shapen older trees were left, showed the increase in the growth of 
these reserved trees to have been surprisingly large since the thinning 
was made, amounting in one sample plot * to 105 per cent in the 
volume growth, and in another 2 to 63 per cent in the basal area growth. 
Yellow pine's rate of growth responds quickly to changes in the 
soil moisture, soil depth, aspect, climate, density of the stand, etc.; 
and the changes in these factors are very frequent in the mountainous 
country such as yellow pine inhabits. Within the Blue Mountain 
region alone, on neighboring tracts (Winlock's Mill and Mill Creek) 
both of which support typical commercial yellow-pine stands, the 
volume growth of a 190-year-old tree is in the one case 3.7 board 
feet per year, and in the other 9.0, a range of 240 per cent. 
STANDS. 
It is easy to determine the rate of growth of individual trees, but 
extremely difficult to find out, even approximately, that of stands, 
especially when only uneven aged and virgin forests which are irregular 
in density are available for measurement. Theoretically, and ac- 
tually on large areas, there is no net growth in the virgin forest; i. e., 
the growth of the living trees is just offset by the death of occasional 
old ones. Young trees take the place of the dying ones just rapidly 
enough to preserve indefinitely a uniform volume. Assuming that 
no trees died, the growth on an acre in such stands as those listed in 
Table 7 would probably be 100 board feet or more per year on average 
soils, and fully 200 feet on good soils. 3 
The forester, however, is particularly interested in the rate of 
growth that he can secure on lands that have been cut over under 
proper regulations. Until there is an opportunity to remeasure 
sample plots in areas which have been cut over, exact yield data of 
this character will be lacking. Estimates based upon the gross 
growth of virgin forests, which take into consideration the several 
1 Manuscript report, " Silvicultural Aspects of Cutting in Open Yellow-Pine Forests," by H. D. Foster, 
forest assistant. 
a Manuscript report, "Notes Regarding Increased Growth in Yellow-Pine Stands as the Result of a 
Selection Cutting," by Thornton T. Munger, forest assistant. 
■ Growth rate of individual trees as shown in Table 11. 
