64 



Forest Mensuration 



number of trees of the various diameters, composing a stumpage of from 

 1,000 to 12,000 feet board measure. 



c. Predict the number of trees and their exact diameters to be found 

 10, 20 or 30 years after logging, according to severity of logging (diam- 

 eter limit). 



d. With the help of the volume tables, give the contents of these trees. 



In these tables as well, the death rate amongst trees is disregarded. For 

 normal death rate, compare Pinchot's "White Pine," p. 80, ff ; also remarks 

 at end of Paragraph LIV. 



PARAGRAPH XCVII. 



THE INCREMENT OF A WOODLOT. 



The current as well as the annual average increment of normal, even- 

 aged woods culminates at a much earlier date than the increment of the 

 trees composing such woods. The explanation lies in the death rate of 

 the trees. 



Under a close crown density in even-aged, normal woods, the stronger 

 half of the trees yield, from the pole stage on, practically all the incre- 

 ment, the weaker half of the trees being almost inactive. 



The better the quality of the soil, the earlier occurs the culmination of 

 the increment ; consequently, on good soil, shorter rotations are apt to be 

 advisable than on poor soil. 



Light demanding (intolerant) species show an earlier culmination than 

 shade bearers (tolerant) species. 



For white pine woods, after Pinchot, the years of increment culmina- 

 tion are as follows : 



I denotes best; II denotes medium, and III denotes poorest quality of 

 soil. 



The increment of a woodlot, whether normal or abnormal, can be 

 obtained : 



a. With the help of yield tables. 



b. By special investigations made into the rate of growth of sample 

 trees (Paragraph XCVIII.). 



