A Study on the Weibull Paramenters Expressing the Diameter Distribution of Plantations

A problem in the expressioi~ of diameter distribution of plantations using only the Weibull parameters a, b and c was examined. First, it was shown that the scatter of diameters could not be evaluated exactly using only parameter b. Therefore, to solve this, a simple calculating method of a standard deviation and variation coefficient of diameters using the Weibull parameters b and c was devised. From examples taken from application, it became clear that differences in the scatter of diameter distributions, where parameter b was nearly the same and c was greatly different, could be evaluated precisely by comparison of standard deviation and variation coefficient calculated using the above method. Furthermore, when comparing of some diameter distributions in which parameter b was different, it was shown that difference in the scatter of diameters must be evaluated using standard deviation and variation coefficient. From the viewpoint of forest management technology, it is very important to ascertain the scatter of diameters with regard to plantations. Therefore, the simple method of calculating standard deviation and variation coefficient of diameters proposed in this study should be utilized effectively in study of forest management technology of plantations using the Weibull distribution.