The stand structure and the growth of sugi (Cryptomeria japonica D. DON) natural forests on Yakushima

In 1973, five permanent plots were established in sugi (Cryptomeria japonica D. Don) natural stands on Yakushima, an island off the south coast of Kyushu, Japan's southern most main island. In 1983—1988, remeasurements were made on four of the permanent plots. This paper reports on the stand structure and the growth of these stands during the interim. The percentage of the basal area in the groups of sugi and other coniferous trees was about 70—80 % in each stand. No changes of DBH-height curves of sugi and broadleaved trees occurred, but among plots large differences were recognized. No regeneration and ingrowth of sugi were recognized in any stand. The two generations of sugi, which were divided at the point of about 90—100 cm of DBH, were noted by using an analyses of DBH-distributions, growth patterns of DBH classes, and crown-structures. The net growth-rate of sugi, including the ingrowth, was 0.5∼1.2 %.