REGIONAL VOLUME TABLE 



^27 



To make more than one table, would, however, be wasted effort, 

 leading merely to confusion, unless some simple method could be de- 

 vised to enable an estimator to tell which table should be used for any 

 given stand. This must depend, of course, on the basic cause of form 

 difference. Although there are probably many such, the most im- 

 portant (setting aside for the moment regional location) can be as- 

 sumed to be either age or site. The former is hopelessly unuseable, 

 since the basic tree measurements had not been accompanied by age 

 determinations and since the average age of a stand can not be 

 simply and accurately determined in the field, particularly if it be 

 very uneven-aged. The latter seemed almost equally unpromising, but 

 there was one possible line of attack. If maximum height be taken 

 as a site index, not only could the groups of tree data be classified, 

 but any stand under consideration could be similarly identified by an 

 estimator. 



This plan was therefore attempted. After several trials it was de- 

 cided to use the average height of the tallest 10 per cent of the trees 

 as the index. The result follows : 



Table 3. — Relation of Form Quotient to Maximum Height. 



It will be observed that the correlation between form quotient and 

 maximum height is fairly satisfactory. It was, therefore, considered 

 safe to combine into fwo additional groups, on the basis of maximum 

 height, a relatively small additional number of tree measurements 

 from scattered localities, and this was done. 



Form Factor. — An attempt was made to work out a converting 

 factor from form quotient to frustum form factor, but this was un- 

 successful. A fairly close correlation was found to exist, but not 

 close enough to permit the calculation of the one from the other wnth 

 any accuracy. It, therefore, seemed necessary to prepare tables of 

 frustum form factors for each tree group before making the final 



