LIFE HISTORY OF SHORTLEAF PINE. 
17 
proached at about the age of 50 or 60 years on the best sites and 
70 to 90 years on the poorer sites. In respect to the number of 
trees per acre at these ages, shortleaf somewhat exceeds longleaf 
and notably surpasses loblolly on similar qualities of site. At ages, 
ranging mostly from 175 to 225 years, natural thinning of stands, 
due to old age and overmaturity, goes on at a more rapid rate. This 
is closely associated with the incoming of the new generation and the 
sudden and rapid increase in numbers per acre. 
The number of trees per acre in well-stocked stands decreases as 
the quality of the site improves. At 20 years, well-stocked stands 
in the Arkansas region have usually from 1,000 to 1,300 trees per acre; 
in North Carolina, 1,400 to 1,800; and in central New Jersey, 1,800 
to 2,400. In general, this regional difference holds good for several 
decades; so that at 50 years well-stocked un thinned stands have 
approximately 300, 355, and 500 trees per acre, respectively, in the 
above three regions. The relation of the density to the quality of 
situation, both in one locality and in widely separated regions, 
appears to be constant and regular. The difference in densities in 
normal or well stocked stands in North Carolina and Arkansas is well 
shown by the contrast between Table 5 and Table 6. 
Table 5. — Number of shortleaf trees per acre in stands of different densities in Arkansas. 1 
Age (years). 
Under- 
stocked. 
Well 
stocked. 
Over- 
stocked. 
Age (years). 
Under- 
stocked. 
Well 
stocked. 
Over- 
stocked. 
20 
840 
475 
290 
210 
170 
140 
100 
80 
80 
75 
1,130 
600 
400 
300 
250 
215 
185 
145 
128 
118 
1,540 
1,000 
550 
400 
325 
280 
250 
185 
175 
160 
120 
75 
70 
65 
65 
60 
60 
60 
55 
55 
115 
110 
105 
102 
100 
100 
100 
98 
95 
155 
30 
130 
150 
40. . 
140 
145 
50 
150 
140 
60 
160 
140 
70 
170 
140 
80 
180 
140 
90 
190 
140 
100.. 
200 
135 
110 
i Based on measurements in 38 even-aged stands. The number of trees per acre vary quite widely in 
each case in accordance with the quality of the situation, and the numbers should be considered approxi- 
mate rather than exact. 
Table 6. — Number of trees per acre for well-stocked shortleaf stands in North Carolina. 1 
Age (years). 
Quality 
Quality 
II. 
Quality 
III. 
Age (years). 
Quality 
Quality 
II. 
Quality 
III. 
20 
1,000 
675 
510 
410 
340 
280 
235 
1,635 
1,095 
765 
600 
500 
420 
355 
2, 450 
1,880 
1,405 
1,045 
795 
655 
550 
55 
200 
165 
140 
120 
100 
90 
310 
270 
230 
205 
180 
155 
475 
25 
60 
420 
30 
65 
370 
35 
70. . 
330 
40 
75 
295 
45 
80... 
270 
50 
1 Based on measurements of 80 sample plots; area, 21.6 acres. 
92233°— Bull. 244—15 3 
