360 



GROWTH OF TREE8 Ix\ DIAMETER 



these measurements require no correction. Care must be taken if 

 but a single measurement is made on standing trees, to select the point 

 for testing on neither the lower nor the upper side of a leaning tree, 

 the growth of which is veiy eccentric, coinciding with its position. 



278. Method Based on Comparison of Growth for Diameter Classes. 

 In Chapter XXII it was shown that growth is measured in order that 

 future growth may be predicted. This may be done either by pro- 

 jecting the growth of a past period into the future on the specific trees 

 or stands measured, or by the method of comparing the growth on 

 trees or stands which have reached a certain size or age, with younger 

 or smaller trees which are assumed to grow at a like rate. These 

 principles must be applied in utilizing the growth of trees for determin- 

 ing that of stands. 



Since diameter, not age, is now the basis of the growth study, trees 

 are classified for growth on the basis of their present diameters at 

 B.H. and an average rate is determined for each class. The result of 

 such a study is applied to trees of given diameter classes in the stand 

 or forest. By the method of comparison, a tree now 15 inches in 

 diameter which has grown 1 inch in the last 8 years, was 14 inches 

 D.B.H. 8 years ago, and trees now 14 inches D.B.H. if compared with 

 this growth, will presumably grow at like rate for 8 years. 



This requires current growth to be measured by inches of diameter, 

 or half-inches of radius, and not by decades or periods, in order that 

 the basis of comparison, D.B.H. classes in the past, may be obtained. 

 The rings in successive half-inches of radius are counted and avera 

 by diameter classes, in the following form : 



TABLE LIV 



Current Growth of Spruce, Adirondacks Region, New York 



