Effects of Site Environmental Factors and Stand Conditions on Growth of the Lacquer Tree, Toxicodendron vernicifluum for Evaluation of Suitable Plantation Sites

Abstract

To insure a stable demand of Japanese lacquer, evaluation of suitable plantation sites for lacquer trees, Toxicodendron vernicifluum (Stokes) F.A. Barkley, is urgently needed. In this study, the relationship between lacquer tree growth and environmental factors and/or and stand conditions was examined at 111 plantation sites in Aomori, Iwate, Niigata, and Ibaraki Prefectures. Statistical analysis was carried out using a generalized linear mixed model (GLMM) in which the mean tree diameter at breast height (DBH) was the response variable, and six fixed effects (stand density, slope orientation, soil type, annual mean temperature, maximum snow depth, and ivy damage) and a random effect (prefecture) served as the explanatory variables. The most appropriate model was selected based on Akaike's Information Criterion. We found that the positive coefficient of annual mean temperature and the negative coefficient of maximum snow depth accounted for most of the variation in DBH in the selected model. This is the first study to evaluate environmental effects on lacquer tree growth based on such a detailed measurement of environmental parameters. This study provides sufficient information for evaluating suitable sites for lacquer tree plantations.