GROWTH OF TREES AND FORESTS 



177 



The chief purpose of studying tree volume growth is to be 

 able to predict future growth for a coming period. This can 

 best be done by a study of periodic growth made under condi- 

 tions similar to those which are likely to obtain during the period 

 to be predicted. Unless there is a radical change of conditions, 

 the rate of growth during the ten coming years may fairly be 

 expected to approximate that of the past ten years. The growth 



Fig. 65. — A study of the growth of an indivitUial pitch pine tree is in progress. 



of a past period is easily obtained, (i) by determining the present 

 volume of the tree; (2) by counting the desired number of rings 

 from the bark inward at both ends of the logs, and obtaining the 

 volume of the tree at the beginning of the period; (3) by sub- 

 tracting the second volume from the first. If the percentage 

 of growth is desired, this remainder is divided by the volume 

 at the beginning of the period. For example, a red oak sixty 

 years old had a volume of 8.4 cubic feet. Its volume ten years 



ago was 6 cubic feet, and the tree grew at the rate of ^ or 40 per 



cent. But the annual growth was .24 cubic foot, and hence its 

 annual rate was 4 per cent. Usually the rate of growth of a 



