50 BULLETIN 308, U. S. DEPARTMENT OF AGRICULTURE. 
this tract there should be at least 10 trees per acre, allowing for a 
20 per cent loss in the 30 years. Since shortleaf in forest stands, 
unless crowded, begins to seed at 30 to 40 years, trees 14 inches and 
over are at least 3 decades beyond the beginning of seed-bearing 
age, and probably fully one-third were actual seed producers at the 
time of the logging. A minimum diameter limit of 14 inches usuaily 
provides ample seed trees and a basis of about 10 trees, varying 
considerably, for a second cut in 30 years. The volume of the 12.4 
trees per acre, 10 inches and over in diameter, left on the above 
cut-over tract, in 80 years will scale 2,675 feet, not counting losses. 
On the basis, however, of a probable reduction to 10 trees per acre 
and allowing 20 per cent reduction in scale for defect and breakage, 
the yield at the end of 30 years will be approximately 2,100 feet or 
an increase of 40 per cent over the present yield. The factor of 
accelerated growth, which must be included in the calculation, may 
safely be counted on to increase the rate at least one-half of the 
normal, or to a total yield of 2,400 feet. The power of accelerated 
growth following suppression is definitely known to be retained by 
shortleaf west of the Mississippi to considerably beyond the age of — 
70 years. In 7 representative trees, averaging 67 years old (45 to 
101 years old), the growth in basal area in the 5 years after logging © 
was 171.4 per cent greater than in the previous 5-year period prior 
to cutting. (Plate X.) It is believed that the above calculation is 
conservative. | 
A 10-inch diameter limit, which represents an average age of 40 
years, is about the present minimum commercial diameter limit for 
the region. If this limit were adopted, it would clearly be neces- 
sary in every operation to make special provision for retaining sufli- 
cient seed trees. This sort of cutting would result in more uniform 
conditions on the ground following logging, largely increase the 
area for incoming reproduction, and thereby gain some ground 
toward bringing about the desired even-aged form of forest. Wher- 
ever the present stand is dominated strongly by pine, in contrast to 
-the mixed pine and hardwoods, and the region is rough or rather — 
inaccessible, it appears that cutting to include the smallest mer- 
chantable size will give good results. 
The silvicultural principles upon which the marking and logging © 
of shortleaf pine are based are: The high capacity of the species for 
recovery after suppression, and abundance of seed and demand of the 
seedlings for light; the possibility, under certain conditions, that 
shortleaf can profitably be managed on a relatively short rotation; 
the desirability of growing shortleaf in even-aged pine stands, and 
at the same time, where necessary, during the first rotation, retaining 
the younger portion of the stand for a second cut in 30 or more 
