70 VOLUME OF WHOLE WOODS. 



1. Estimating the Volume of the Wood as a whole. 



This method, being the oldest and roughest of all, consists 

 in going through the wood and estimating the volume either of 

 the whole wood, or per unit of area, if the total area is known. 

 The estimator must consider differences in the density of 

 stocking, the average volume per tree, the differences in the 

 quality of the locality, and, if for the whole wood at once, its 

 area. It stands to reason that the method requires great ex- 

 perience and practice on the part of the estimator, and even 

 then considerable mistakes may be made. 



2. Estimating by Trees. 



Under this method each tree is estimated separately, the 

 volume of the wood being obtained by adding together the 

 volumes of the several trees. With great care an experienced 

 estimator can obtain fairly accurate results, but if done care- 

 fully the operation takes almost as much time as if the 

 diameters of all trees and the height of some of them are 

 measured; in the latter case the volume can be calculated by 

 means of form factors or volume tables, a procedure which 

 yields far more reliable results. 



The method is only justified in open woods, consisting chiefly 

 of old trees, such as standards in high forest or in coppice with 

 standards, or where a low degree of accuracy meets the require- 

 ments of the case. In such cases the estimate may extend over 

 the whole area, or over a sample plot only. 



3. Estimating according to the results of Past Fellings. 



Where fellings have been made and the fall accurately 

 measured, the results can be used to estimate the standing crop 

 in similar woods. In such cases it is necessary to take into 

 consideration any differences in the age, density of stocking, 

 height, etc. 



Frequently fellings made in clearing strips for roads or rides 



