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 reeommended: 
(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, agmmerorndline 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 
