blunder to attempt to allow for the 1-log difference in height by 

 simply using the volume in the unrevised regional table for a 

 3-log tree; the table itself should always be corrected for differ- 

 ences in utilization. 



APPLICATION OF YIELD TABLES 



DETERMINATION OR IDENTIFICATION OF SITE. 



Sites in this study have been designated by the height attained 

 on each by the average dominant tree at the arbitrarily chosen 

 age of 50 years. It has been found that such heights are the 

 most reliable and convenient means of identifying the productive 

 capacity of forest land. In order, therefore, to apply the tables 

 to any particular site, it is necessary to identify the site from the 

 height of dominant trees now growing upon it. The following 

 method of identification is recommended: 



(1) Lay out a sample plot, of any convenient shape but con- 

 taining from 100 to 300 trees, in a well-stocked portion of an 

 even-aged stand growing on the site in question. Very young 

 stands (under 25 years) are somewhat more erratic. They are 

 therefore less desirable than older stands and can well be avoided. 

 Turpentined stands should also be avoided. Old-field stands are 

 not so reliable as those on cut-over land, because the high quality 

 of the site apparent in the first decade or two deteriorates in time. 



(2) Tally the breast-height diameters of all trees on the plot 

 above 1.5 inches by two classes — dominant trees (including 

 codominants) and others. 



(3) Obtain from this tally the average diameter for the 

 dominant stand, using the basal-area method. 



(4) Measure a sufficient number of heights, corresponding to 

 the full range of diameters of both dominant trees and others, to 

 construct a satisfactory curve of height over diameter. (Actual 

 plotting in the field and construction of the curve at that time 

 will be the best guide to what is a sufficient number.) 



(5) From the height-diameter curve obtain the height of the 

 average dominant tree, using the average diameter determined 

 by step 3. 



(6) Determine the age of about six trees (more if there is con- 

 siderable variation) among the average dominants, and strike an 

 average. The additions that must be made to the age as 

 determined at breastheight or on the stump are given under the 

 definition of "Age," page 15. 



(7) On the height-growth classification graph for the proper 

 species (figs. 1 to 4) plot the height of the average dominant 

 tree of the sample stand over its age. These graphs are a series 

 of curves, one for each 10-foot site index, showing the height of 

 the average dominant tree at various ages. The curve nearest 



5 



