PREDICTION OF GROWTH FROM YIELD TABLES 



415 



This method is illustrated below based on a standard yield table, § 314. 

 Second-growth Hardwoods in Central New England 

 Site Class I 



This assumes no increase in the density factor with age and is the most conserva- 

 tive method. 



Assuming that future yield will be influenced by the number of trees and their 

 distribution, the future yields as shown may be increased as follows : 



This basis gives the maximum possible yields to be expected by contrast to the 

 first method, since it does not contemplate the loss of any of the original six hundred 

 trees, and assumes that these trees are distributed at equally spaced intervals over 

 the area. 



Somewhere between these two predictions the actual future yield will be found. 



Use of Basal Areas. Basal area may be substituted for yields in 

 determining the percentage relations, and as a basis for predicting 

 yields in cubic feet. If in the above example the basal area at twenty- 

 five years is 57.2 square feet per acre, the reduction per cent is 63 and 

 the same prediction of future yield is obtained, which can be modified 

 by comparing the number of trees per acre in the same way. 



These illustrations bring out the function of a yield table as dis- 

 tinguished from that of merely stating the yields of stands. When the 

 total age of any given stand is determined in addition to its volume, 

 the rate of growth per year for that stand can then be found, or its past 

 yield. But the whole purpose of a yield table is to predict the future 

 yields of stands. A standard yield table gives a means of predicting 

 this future yield, by indicating first the yield relation as to density of 



