36 



BULLETIN 308, U. S. DEPARTMENT OF AGRICULTURE. 



Table 18. — Relation between tree density and yield of slwrtleaf pine in board 



feet per acre} 



Total trees per 

 acre. 



Number 



150 



200 



250 



300 



3-50 



400 



450 



Trees 8 

 inches 

 and 

 over 

 in dia- 

 meter. 



Num- 

 ber. 

 130 

 175 

 215 

 260 

 290 

 290 

 260 



Saw timber. 2 



Scrib- 

 ner 



rule. 



Board 

 feet. 

 11,250 

 13,500 

 16,000 

 18,100 

 19, 400 

 19,100 

 17, 500 



Doyle 



rule. 



Board 

 feet. 

 6,600 

 8,450 

 9,700 

 10, 600 

 10,800 

 10, 200 

 9,000 



Aver- 

 age 

 dia- 

 meter 

 (breast- 

 high). 



Inches. 



11.5 



10.9 



10.4 



9.8 



9.4 



Total trees per 

 acre. 



Number. 



500 



550 



600 



650 



700 



750 



Trees 8 



Saw timber. 2 



Aver- 



inches 

 and 





age 

 dia- 







over 



Scrib- 



Doyle 

 rule. 



meter 



in dia- 



ner 



(breast- 



meter. 



rule. 



high). 



Num- 



Board 



Board 





ber. 



feet. 



feet. 



Inches. 



255 



15,350 



7,900 



8.1 



235 



13,200 



6,800 



7.7 



215 



11, 250 



5,800 



7.3 



195 



9,250 



4, 450 



7.0 



180 



7, 500 



3,200 



6.6 



160 



5,900 



2,000 



6.3 



140 



4,250 



800 



6.0 



1 A 30-year old stand of varying densities on good quality site and protected against fire, Montgomery 

 County, Ark. 



2 Yield of trees 8 inches and over in diameter at breast-height. 



In a selected old-field stand in Arkansas, 20 years old (PI. VII, 

 fig. 1) a density of 1,440 trees per acre gave a yield of 1,600 board 

 feet, counting all trees 8 inches and over in diameter, while a normal 

 stocking of 520 trees per acre in the same stand yielded 10,200 feet 

 of saw timber. The overstocked stand contained only 40 trees per 

 acre 8 inches and over in diameter and merchantable for saw timber, 

 the well-stocked stands 200. The relation between number of trees 

 per acre and diameter growth is so regular that it is almost sus- 

 ceptible of expression with mathematical exactness. The sections in 

 Plate VIII represent the average growth in a 33-year-old stand of 

 shortleaf pine coming up under full-light exposure in an opening of 

 about 10 square miles caused by a cyclone. A density of 370 trees 

 per acre gave a yield of 18,000 feet of saw timber, a density of 550 

 trees per acre 21,800 feet. The trees widely spaced averaged 1 inch 

 larger in breast-high diameter, thus yielding a higher grade of 

 lumber. 



The number of trees to be left per acre in thinning shortleaf stands 

 of specified ages varies chiefly with the quality of the situation. 

 Table 19 indicates approximately the number of trees in natural un- 

 thinned stands and also the trees left after thinning. The better class 

 is representative of the more southern and western portions of the 

 shortleaf range; the poorer class, of unfavorable local situations in 

 this portion of the range, and the more northern and eastern areas 

 of distribution. 



