426 



THE USE OF YIELD TABLES 



indicates the proportional yields at different ages, correlated with the 

 proportional falling off in numbers of trees per acre at these ages, both 

 factors correlated with diameter of the average trees, for it is evident 

 that in such a forest no stands will be found which are pure, even-aged 

 or fully stocked over any large area; hence the use to which the table 

 is put must be solely as a standard to be discounted by a reduction per 

 cent. 



TABLE LXV 



Yields op Cordwood, for Yellow Poplar in Tennessee — Based on Crown 

 Space and Volumes of Trees of Given Ages 



*rrom volume table 5, p. 22, Bulletin 106, Yellow Poplar in Tennessee, W. W. Ashe, State 

 Geological Survey of Tennessee, 1913. 



The age of stands, by this method, is assumed as the age of trees 

 of given diameters. To determine this age, for each diameter class, 

 a curve of growth is required in which ages are averaged on the basis 

 of diameter (§ 276). Otherwise the ages of trees of the larger classes 

 will be over-estimated. 



To apply this yield table for the prediction of yield in the forest, 

 a large area must be considered; otherwise the assumed correlation 

 between age and diameter will not hold good. The stand table (§ 188) 

 for this area must show the number of trees of each diameter class in 

 the forest. 



One of the principal services rendered by such a table is its indication 

 of the probable rate of loss of numbers, which is a most difficult problem 

 to solve by any other method. 



