1124 
Journal of Agricultural Research 
Vol. XXXI, No. 12 
a 5-inch top as a cutting limit entirely within the bounds of possibility. 
Incidentally, these were the standards accepted by Gallaner for the 
west slope of the Sierras. 
In the actual construction of the volume tables the data were 
worked up by three different methods, i. e., the conventional method, 
the frustum form factor, and the alignment method. The tables 
were then checked against the trees from which they were constructed 
and against each other, and it was found that the values derived by 
the different methods were generally exceedingly close, and that by 
each method the values from the tables checked well against the trees. 
In the same way cubic-foot tables were made and the board-foot 
tables checked against the cubic-foot tables, a conversion factor being 
used. Although it is recognized that the basis of data is rather small 
for construction of final volume tables for immature trees under east 
slope conditions, comparison of the values with those in the current 
tables indicates that the latter would be less suitable. 
The values for a given total height and diameter class are higher 
on the east slope than on the west slope, using Gallaher’s volume 
tables for the latter set of conditions. This is because the more 
rapid taper in the top of the east slope trees gives them a shorter 
top above the 5-inch merchantable limit than in the west slope trees. 
With trees of equal total height, those on the east slope thus have 
a greater merchantable length. If the tables were worked up on the 
basis of merchantable height instead of total height, the indications 
are that values would be higher for west slope than for east slope trees. 
SITE CLASSIFICATION 
A little consideration of the main problem, that is, the determina¬ 
tion of the yield capacities of large areas of virgin forests, makes it 
clear that yield tables to be reacnly usable must be tied into some 
index which can be measured without difficulty. The principle that 
height of dominant trees at a given age or at maturity is a reasonably 
correct expression of differences in yield, or site quality, is so thor¬ 
oughly established by both American and European experience that 
no objections could be seen to its adoption here, and consequently 
each plot was referred to the average height of dominant mature trees 
adjacent to the plot, usually four or five trees being measured to 
obtain a correct figure. One can readily see that this procedure 
makes possible at once an approximately correct site classification 
of the area where timber reconnaissance has been made. The 
original timber tally sheets show the occurrence of the mature timber 
by merchantable heights, and one readily picks out on the sheets the 
average maximum heights on a given forty. Then, after these heights 
have been entered on a base map, it is also easy to convert mer¬ 
chantable height to total height by adding the length of top above 
the merchantable limit used in the volume tables. 
The concensus of opinion among foresters in this country seems to 
be that five site classes are sufficient, some writers, indeed, favoring 
three. After considerable discussion and study of the question it 
was decided to adopt the five-site quality classification and to use a 
difference of 20 feet in mature height as the interval between classes. 
This interval appears to be fairly well agreed upon and also has the 
great virtue of fitting the conditions in the forest. That is, in pure 
