In the evaluation of a forest, it may be more helpful and more convenient to estimate the log volume by the direct measurements of standing indivldual trees than the conventional method which deduces the log volume from the evaluated total tree volume of a forest.
As a practice of his method, the author tried to get a table for evaluation of log volume by direct measurement of standing trees. The measurement was carried on 313 samples of "Hinoki" trees of several stands in Shimane Prefecture.
His procedure which he followed in making the table, was as follows :
1. measurement of D.B.H. and height of sample trees.
2. evaluation of log volume by sectional measurement on all of samples.
3. estimation of the value of coefficient in the equation.
V=<10>^a・D^b・H^c
Thus he get following three equations, dividing the samples in three classes by the diameter.
For the first class(D.B.H.16 cm and over)
V=0.000002844・D^<2.683462>・H^<1.187045>
For the second class(D.B.H.18～26 cm)
V=0.000009224・D^<1.883012>・H^<1.572019>
For the third class(D.B.H. 28 cm and over)
V=0.00004628・D<^1.443939>・H^<1.507586>
where the error rate for a tree may be 24.3%, 21.4%, 14.3% respectively.
Then he modified it in a form of one variable equation as follows.
For the first class
V=0.000003198・D^<3.793595> (error rate 33.2%)
For the second class
V=0.00003688・D^<2.863836> ( 〃 26.8%)
For the third class
V=0.0006674 ・D^<1.961423> ( 〃 15.7%)
For the convenience of practice he prepared a table to evaluate log volume, as shown in Table 7 to be used in Shimane Prefecture.