The treatment of sugi natural forests on Yakushima

The control method is ideal to treat sugi (Cryptomeria japonica d. don) natural forests on Yakushima (an island south of Kyushu, the southernmost main island of Japan) because it takes into account the power of nature and is based on the actual growth of forests. From an investigation of the growth for fifteen years in an excellent natural forest, 10 years was decided as the management period. A standard volume table was constructed by using the richards growth function. In the stand experimenting with this method, the distribution of the types of trees were determined. That of the broadleaved trees was random, whereas, those of sugi and tsuga (Tsuga sieboldii carr.) were contagious. Tall trees also were distributed contagiously. The coniferous trees and the broad-leaved trees, which grow tall, were found on different topography in slope, aspect and so forth.