STANDARD VERSUS LOCAL VOLUME TABLES 153 



if the volumes taken from the table are those for heights correspond- 

 ing to the trees in the stand. 



130. Standard Versus Local Volume Tables. Volume Tables based 

 on both diameter and height classes, in whose construction from 500 

 to several thousand trees have been used, selected from as wide a range 

 of sites and locations as possible, are termed Standard Volume Tables, 

 while those based on diameter, either alone or with the average height 

 of trees of each diameter class stated, and applicable only to a given 

 stand or site, are known as Local Volume Tables. 



It follows that local volume tables applicable to any stand, age 

 or site can be derived from the values given in a standard volume table 

 and can be expressed on the basis of diameter alone by first determin- 

 ing, for the stand, the average height to use for each diameter class. 



Classification by both diameter and by height is not sufficient to 

 secure complete accuracy in volume tables because of differences in 

 average form (§ 166). But such tables, well constructed, are vastly 

 more accurate than any universal table based on uniform tapers, or 

 frustums of cones, and are known to apply with almost the same degree 

 of accuracy throughout the entire range of a species. Greater vari- 

 ation in form and volume of stand is caused by differences in soil, expo- 

 sure and density in a restricted locality than by a thousand miles dif- 

 ference in location. 



