42 BULLETIN 308, U. S. DEPARTMENT OF AGRICULTURE. 
The yield in saw timber of a crowded stand 30 years old is very 
small, because very few trees have attained a merchantable diameter. 
The largest diameters occur in understocked stands, which yield con- 
siderably less, however, than fully stocked thinned stands. If the 
material derived from the thinnings is of sufficient value to pay for | 
the cutting or to yield a profit, the cost per thousand feet of growing 
saw timber in fully stocked thinned stands is less than in either 
crowded or understocked stands. If thinnings do not pay for them- 
selves the cost is greater. At the age of about 48 years, when thinned 
stands reach their maximum annual yield, the diameter of the average- 
sized tree is about 9.5 inches breast high, or 11.5 inches on the stump. 
The average annual yield of saw timber at that time from trees 9 © 
inches and over in diameter is 410 board feet. For similar unthinned 
stands the maximum annual yield occurs at the age of about 57 years, 
and the tree averages 8.2 inches at breast height, or 9.8 inches on the 
stump. The annual increment at different ages from unthinned and 
thinned stands is shown in Table 21. 
TABLE 21.—Average annual increment per acre of saw timber from thinned and 
unthinned shortleaf-pine stands in Virginia. 
[Trees 9 inches and over in diameter, measured at breast height.) 
Thinned stand (thin- 
nings neglected). Unthinned stand. 
Age. Periodic : Periodie 
Average annual Average annual 
annual increment annual increment 
increment.| foreach |increment.| for each 
decade. decade. 
Years Bd. ft Bd. ft. Bd. ft. Bd. ft 
3 DO pt aie arate no ect ces ere eS 
40 410 800 150 fae fa eee 
50 408 400 262 710 
260 250 190 
70 357 200 238 170 
In calculating the cost of growing shortleaf pine saw timber, com- 
pound interest on the value of the land, accumulated taxes, and other 
expenses must be considered. The effect of thinning upon the final 
yield and upon the cost of growing shortleaf pine are shown in 
Table 22. The calculation assumes a land value of $5 per acre, 
taxes and other expenses at the rate of 1 per cent on the land value, 
and net annual returns of 5 per cent on the investment in land and 
cost of stocking. The lowest cost for unthinned stands was $6.25 and 
for thinned stands $2.21 per thousand feet. The age at which the 
cost is lowest, or the financial maturity of the timber, was 45 years 
for natural stands and 35 years for the thinned stands. 
