THE HEIGHT AND DIAMETER BASIS FOR VOLUME 



TABLES 



By Donald Bruce 



Division of Forestry, University of California 



THE BASIS FOR VOLUME TABLES 



In spite of the many years during which volume tables have been 

 in use in this country, there is still little uniformity of opinion as to the 

 basis on which they should be constructed. It has come to be quite 

 universally agreed that both height and diameter must be recognized 

 as factors of volume, but the method of measuring the former is as 

 yet not standardized and even the point of measurement of the latter 

 may still be questioned. While it is possible that differences in present 

 practice and opinion may be justified in different forest regions, it is 

 more probable that some at least of these divergences are due to the 

 personal preferences of the men responsible for volume table prepara- 

 tion and to the absence of rigorous investigative work. 



THE DIAMETER MEASUREMENT 



On the question of diameter there is less disagreement. Foresters 

 generally accept the measurement at breast height as standard, al- 

 though several other points of measurement are still occasionally ad- 

 vocated. Chief among these others is d.i.b. stump (the favorite 

 of the professional cruisers of the old school), the obvious advantage 

 of which is that it is a measurement free from the influence of bark 

 thickness. In choosing between this basis ^ and the standard d.b.h. 

 there are two points to be considered : ( 1 ) The ease and accuracy 

 with which the measurements can be taken. (2) Their relatives pre- 

 cision as an index of volume. 



The first of these requirements is far better met by d.b.h. in the 

 case of standing trees. Measuresments of d.i.b. stump can be obtained 

 with accuracy but not with ease, since the bark must be cut through. 

 D.b.h. is then obviously preferable unless it can be shown that d.i.b. 

 stump is the far better volume index. 



'Diameter eye high {^i.2^^ feet) has also been advocated by the writer for use 

 with the Biltiiiore stick, but as a supplement to and not a substitute or d.b.h 



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