40 



BULLETIX 244, 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 between 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. 



Scribner 

 rule. 



Dovle 

 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 

 18,100 

 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 little 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 





