APPLICATIONS 



Calculating Current Annual Increment 



Current annual volume increment is commonly calculated by measuring or estimating 

 the two major dimensions of volume increment: change in tree d.b.h. (inches) and change 

 in tree height (feet). Then, these changes are added to present d.b.h. and total 

 height, and the volume change is determined from the difference between the volumes 

 obtained from a volume table or volume equation that relates tree volume to d.b.h. and 

 total height. The prediction equations developed in this report can be used to calculate 

 the 10-year periodic height increment from the corresponding 10-year periodic diameter 

 increment, initial d.b.h., and initial height. When past periodic diameter increment 

 is used to determine future diameter increment, a problem arises because diameter growth 

 generally declines with age. Consequently, the current annual rate would differ from 

 the periodic rate divided by period length. To remedy this problem, we can invoke the 

 observation that whereas diameter increment declines with age, basal area increment 

 usually remains constant (Spurr 1952, p. 214; Smith 1962, p. 55). 



The sequence of calculations is: 



1. Determine past increase in diameter squared. If increment was measured out- 

 side bark, convert to increment inside bark. If measured for a period of y years, 

 convert to a 10-year basis . 



DDS = (d 2 - d 2 ) * 10/u 

 % i-y n 



2. Use past DDS to estimate future AD (10-year periodic increment): 



AZ? = Vd/ + DDS - d. (inches) 



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