Possibilities of a Second Cut 15 



which during the next ten years should amount to 4>,4t66 feet b.m., 

 which is an increase of 70 per cent in volume on the trees left 

 standing. 



This is explained as follows. The calculated growth of the 

 trees now 12 inches and over in diameter will be 1,206 feet b.m. 

 per acre, and the trees now below 12 inches in diameter which will 

 grow to be over 12 inches in ten years will add 639 feet b.m. per 

 acre, giving a total of 1,836 board feet. The stand to be left 

 after cutting, viz., 2,630 feet b.m. per acre, is slightly better than 

 the average, which will be nearer 1,800 feet b.m. per acre. The 

 growth per cent, which includes the maturing of trees now too 

 small to cut, is conservative and might well exceed the above esti- 

 mate of 70 per cent in ten years on all such stands. The reason 

 for their rapid increase in volume is that the trees are in the best 

 condition and of the best sizes for growth, while the removal of all 

 slow-growing and large timber increases the relative average 

 growth on those remaining. 



GROWTH IN VIRGIN STANDS 



The growth in virgin stands of pine in the next decade is deter- 

 mined by the age and condition of the timber. Stands from which 

 the old, overmature trees have been removed present quite a dif- 

 ferent condition from that existing on the average "forty" of 

 virgin timber. After trees have reached a certain size and age, 

 they lose vitality, and succumb to heart-rot, insects or wind. The 

 loss of one old tree, unless it can be logged, will offset ten years' 

 growth on a great many others. Hence, if the stand contains a 

 large proportion of old and large trees, it is probably not increas- 

 ing in volume at all but the reverse, while the value of the standing 

 timber may be sinking because of the progress of decay. 



Owing to the tendency of these pines to grow in even-aged 

 groups, and to the operation of natural destructive agencies, an 

 even distribution of age classes from overmature to seedlings is 

 seldom found on an area as small as forty acres. The timber 

 will be largely overmature veterans, or young and thrifty, and 

 the volume of the stand be actually decreasing, stagnant or 

 increasing according to the age class which preponderates. On 

 large areas it may happen that the annual decay and loss in 

 virgin forests just equals the annual growth, while for any one 

 stand this same balance will be attained in the course of time. 



The tract of 70 acres selected for the study of growth after 

 thinning and removal of mature timber contained a larger propor- 

 tion of young thrifty trees than is found in typical overmature 



