34 BULLETIN 308, U. S. DEPARTMENT OF AGRICULTURE. 
On the National Forests of Arkansas the Federal Government in 
its management of shortleaf pine aims to produce the sort of material | 
most needed by the people, which is mostly medium-sized saw timber. — 
A rotation of about 100 years in fully stocked pure stands affords 
the largest annual yield. The average tree at this age, grown under 
forest conditions, is 74 feet in height by 16.6 inches in diameter, and © 
contains not less than 270 board feet! of merchantable lumber. While — 
the interval between successive cuts 1s many years, it is well to bear in 
mind that present cuttings on private holdings in the region are tak- 
ing very little timber younger than 60 years. Where the stand, 
whether of pure shortleaf or a mixture of shortleaf and various 
hardwoods, is moderately open, as is the case over considerable of its 
range, the culmination in annual yield is earlier. A rotation of 90 — 
vears under these conditions will probably give the highest average 
vearly yield of saw timber on the Arkansas National Forest. Under 
natural conditions, and without fire protection until very recently, 
shortleaf pine on the Arkansas National Forest at 90 years measures 
mostly from 14 to 18 inches in diameter, averaging 15.9 inches, and ~ 
from 60 to 110 feet in height, averaging 73 feet. The average tree of — 
this size contains 240 feet of saw timber. Judging from the character — 
of similar stands up to 80 years old, pure stands at 90 years on aver- 
_age sites in Arkansas yield from 30 to 40 thousand feet, while com- 
pletely stocked stands on the same situations contain about 170 trees © 
per acre and yield about 50 thousand feet of saw timber. 
THINNINGS. 
The extensive areas of shortleaf pine in the younger stages of | 
growth and the quick response of the species to changes in light © 
supply? make thinnings very important in its management; their 
purpose is to admit the right amount of light so far as is possible to 
each individual tree. The available soil moisture and growing space 
for the roots must also be considered. Thinnings are made neces- 
sary by the dense seeding which usually takes place under protection 
from fire, in openings, such as abandoned fields or forest clearings. 
While natural thinning gradually reduces the density of the stand, 
progress is slow and much time is lost in the production of a mature 
crop. Fires thin stands, but in a haphazard manner, accompanied 
always by severe loss and injury. Thinnings made by selecting the 
proper trees at the right intervals result in an increased yield, a 
notable improvement in quality, and frequently a higher net money 
return on the investment. 
1Table 29 in Appendix. 
2U. S. Department of Agriculture Bulletin No. 244, “‘ Life History of Shortleaf Pine.” 
