40 
BULLETIN '2U, U. S. DEPARTMENT OF AGRICULTURE. 
attacks of natural enemies of various sorts. In good situations in 
Arkansas, for instance, well-stocked 160-year-old stands of shortleaf 
have average yields of about 45,000 board feet, or approximately 
the same as 58-year-old stands on similar situations. The point of 
highest average annual production of natural unthinned stands is 
probably between 90 and 100 years in Arkansas and some 10 years 
earlier in the central Piedmont region bordering the Atlantic coastal 
plain. 
Table 15. — Relation betiveen tree density and yield per acre for 30-year-old shortleaf pine. 
[Yield from trees 8 inches and over in diameter. Based on 7 sample areas in Arkansas in stands of similar 
soil, protected against fires, and ranging from 210 to 780 trees per acre in quality I site.] 
Trees per acre. 
Yield (saw timber). 
Average 
diameter. 
Total. 
8 inches 
and over in 
diameter. 
Seribner ! Doyle 
rule. rule. 
150 
200 
250 
300 
350 
400 
450 
500 
550 
600 
650 
700 
750 
800 
130 
175 
215 
260 
290 
290 
260 
255 
235 
215 
195 
180 
160 
140 
Feet b. m. 
11, 250 
13,500 
16.000 
IS'. 100 
19; 400 
19,100 
17, 500 
15, 350 
13,200 
11,250 
9,250 
7,500 
5,900 
4,250 
Feet b.m. 
6,600 
8,450 
9,700 
10,600 
10,800 
10,200 
9,000 
7,900 
6.800 
5,800 
4,450 
3,200 
2,000 
800 
Inches. 
11.5 
10.9 
10.4 
9.8 
9.4 
8.9 
8.5 
8.1 
7. 7 
7.3 
7.0 
6.6 
6.3 
6.0 
YIELD IN PURE STANDS. 
Old growth or virgin stands in regions of good development show 
yields averaging 10 to 30 thousand board feet per acre over con- 
siderable areas. Most of such tracts are at the present time found 
only in the more inaccessible regions in the upper portions of the 
middle Atlantic coastal States and in the Louisiana-Arkansas district. 
Much larger amounts occur in mixed stands with hardwoods. 
Fully stocked tracts of shortleaf pine in natural stands are scat- 
tered and rarely occur in areas of considerable size. Irregular 
stocking at the outset, fire, and other causes produce many open 
spaces where trees are needed to complete the stand. In other places 
the stand has from the start maintained too many trees per acre to 
give the best results in quality or quantity of product. The average 
yields of natural stands, therefore, vary widely and have lit tie sig- 
nificance in considering the habits and possibilities of the tree when 
growing in full stands. The best basis for considering the yield of 
forest trees like shortleaf which occur in pure stands is the yield of 
fully stocked stands or portions of stands growing under known con- 
ditions of situation. Such information, when classified by age and 
site quality for normally stocked stands, is known as a normal yield 
