14 



Diameter Breast High. The average, breast-high diameter 

 of all trees over two inches was obtained by dividing the 

 basal area per acre by the number of trees per acre. Two 

 factors cause variation in the average diameters of trees in 

 fully stocked stands of the same age. First, the normal basal 

 area and crown cover may exist when the dominant stand 

 contains few trees of large diameter and crown spread or 

 many trees with small diameters and crowns: second, there 

 may or may not be a large number of suppressed and inter- 

 mediate trees in the stand. If there is the diameter of the 

 average tree is greatly reduced. 



Cubic Foot and Cord Volume per Acre. Several methods of 

 obtaining volumes in the construction of yield tables are 

 recognized. Perhaps the most common is that of the mean 

 sample tree. This method involves the computation of the 

 mean at the time of measuring the sample plots and the 

 cutting and partial stem analysis of several sample trees for 

 each plot. In the present case, a red maple volume table, 

 made on the Harvard Forest, 1 and giving volumes in cubic 

 feet and cords, was used. Its applicability was established 

 by the following test. A quarter acre sample plot was care- 

 fully laid out in a twenty-eight year old better second growth 

 hardwood stand on quality one site. Its approximate com- 

 position was red oak thirty per cent, red maple twenty-five 

 per cent, chestnut fifteen per cent, yellow birch eight per 

 cent and miscellaneous species twenty- two per cent. All 

 trees over two inches were calipered and tallied in inch diam- 

 eter classes and a number of heights taken. Three inch 

 diameter classes were then formed and the height and diam- 

 eter of the mean sample tree for each of these was deter- 

 mined. At least three mean sample trees for each class were 

 then felled and cut into bolts four feet two inches long, the 



1 Original: A Volume Table For Red Maple on the Harvard Forest, E. E. 

 Carter, Bulletin of the Harvard Forestry Club, vol. 2, 1913. 



Revised: Volume Table for Red Maple on the Harvard Forest (Revised 

 and Enlarged by E. E. Carter in 1915). U. S. D. A. Bull. 285, The Northern 

 Hardwood Forest: Its Composition, Growth and Management, pp. 61-63. 



