Dec. i 5,1925 Yield Capacities of Yellow Pine Type in California 1123 
a measurement of each individual tree on the plot. By this method 
a height-diameter curve for each plot or for each group of plots can 
be drawn, and in computing volumes the height indicated by the 
curve can be used with very little chance of serious error. Compu¬ 
tations on several of the plots laid out by Gallaher 4 in west side pure 
yellow pine showed an error of from 1 to 2 per cent in using this 
method, the values where every tree was measured tending to run 
slightly higher than where the height-diameter curve was used. 
This short-cut method was felt to be fully justified, however, by the 
rate of speed which it made possible and because, so far as can be 
determined, any error introduced is likely to be on the side of con¬ 
servatism. 
Wherever possible, dominant and codominant trees on the plots 
were climbed and taper measurements taken, these trees later being 
used for the construction of a volume table. On part of the plots, 
also, sample trees were felled and complete stem analyses made. 
Occasionally wind-thrown trees were also measured. 
Work was carried on from six camps well scattered over the area, 
a radius of several miles being covered from each. Thus it is be¬ 
lieved that a sufficient portion of the entire area was studied to be 
representative of the entire range of conditions in yellow pine stands. 
In all, 175 plots were measured: 132 pure yellow pine, 22 pure 
white fir, and 21 mixed stands. The site qualities as measured 
by mature heights ranged from about 170 feet to as low as 80 feet, 
thus practically embracing the entire range of site quality on the east 
side of the Sierras. The average plot was almost exactly one-fourth 
acre in area, individual plots varying from one-twentieth of an acre to 
nearly an acre in extent. For the construction of yellow pine volume 
tables approximately 150 trees were taken. About 25 white fir also 
were measured. 
It can be seen from the preceding discussion that the field methods 
adopted differed in some respects from the traditional textbook 
methods for studying yield, a situation made necessary by limitations 
of the forest itself and of men and money to carry out the work. 
OFFICE METHODS 
The office methods used were in the main those established by 
custom for the construction of yield tables. As a preliminary step, of 
course, the tree-volume data had to be worked up and tables con¬ 
structed. The first question encountered was the selection of a log 
rule on which to base the tables. The Scribner Decimal C rule, which 
is in current use in the Forest Service, is obviously unsuited for the 
study of future yields because of the large overrun of material sawed 
out as against the values from the rule. The information desired was 
the number of board feet of lumber per acre that could be obtained, not 
how many thousand feet the log scale would estimate. The Clark 
International rule was therefore selected because of its close approxi¬ 
mation to mill scale. In determining on a standard of utilization on 
which the yield tables should be based, many individuals were con¬ 
sulted. The general consensus of opinion designated 8 inches in 
diameter at breast height as the smallest tree to be considered, and 
4 Gallaher, W. H. second growth yellow pine. Forestry Quart. 11:531-536, illus. 1913. 
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