Abstract
Log production has been expanding so rapidly in recent years in Miyazaki Prefecture where Sugi (Cryptomeria japonica) grows fast, that the sustainability of production is questioned. This study proposed a method to simulate the sustainability of log production, and applied it to the non-national Sugi plantation forests in the prefecture. With this method, how long a target log volume can be sustained in each watershed is calculated under the presumptions on the replantation rate and the unable-to-harvest forest rate. The effects on the length of sustainable production period of some policy options such as replantation rate improvement, recovery from unable-to-harvest forests to harvestable ones, and production volume share between watersheds are also examined. The results showed that the sustainability is in a critical level in some watersheds so that some policy options need to be realized, from which it is considered that such a method to simulate and examine policy options will be an effective tool for local forestry administration at a time when log harvest is increasing nationwide.
