アテ択伐林に関する研究(4) : マアテ択伐林の蓄積価と限界粗収益

1. The relation between log price per m^3 and the minimum diameter of the smaller end of log by Japan log rule was to be expressed by following equations :
(log length) (experimental equation)
1.8m : P_1 = -13,396 + 1185.8・D
3.0m(lowest log of a tree) : P_1 = -231,030 + 30,551.7・D - 851.7・D^2
3.0m(other logs without lowest log) : P_1 = -10,896 + 2111.7・D
3.8m(below 14cm) : P_1 = -3,309 + 2164.6・D
3.8m(14-21cm) : P_1 = 25,635
3.8m(above 21cm) : P_1 = 1,139.5 + 1,280.2・D
6.0m : P_1 = -163,718 + 23,016.5・D + 635.4･D^2
The maximum of log price appeared in two parts ; one was at 14-16cm diameter of 3.0m and 6.0m log length, and the other was at the largest diameter class of 3.8m and 1.8m.
2. The marginal gross revenue of a tree was obtained with the sum of the product of annual current timber volume increment (of a log) and marginal price per m^3 (of a log) of each log.
The marginal gross revenue of the stand was obtained with those two data of tree instead of log.
3 . The ratio :
(marginal gross revenue)/(stampage value) x 100
was a sort of earning rate. This rate of Hosoya was 4.6%, and that of Konosu was 20.6%. The former was very small and not desirable. On the other hand, the latter seemed to be desirable, but the absolute dimension of marginal gross revenue was not largest one among 6 selection forest stands.