Individual Tree Growth Models Of Natural Mixed Forest In Changbai Mountains

The data used to develop individual model for natural mixed forests were collected from 712 remeasured permanent sample plots of 10-year periodic from 1990 to 2000 in Baihe Forest Bureau of Changbai mountains, northeat Chian. Based on analyzing relationship between diameter increment of individual trees with tree size, competitive status, and site condition and finding out the major independent variables, the growth models for individual trees of 15 species in the natural mixed forests, that have simple form, good predicting precision, and easily applicable, were developed using stepwise regression method.The research results for individual trees growth model of each species showed that main variable to influence on diameter increment of individual trees for natural mixed forests were tree size (D) and then competition index. The site condition was not related with diameter increment. The natural logarithm of DBH (lnD) and square diameter (D~2) were included in the predicting models of diameter increment for all 15 species. The diameter increment was directly proportional to tree diameter for each species. For the competitive indexes in growth model, the relative diameter (RD), canopy closure (P), and the ratio of diameter of subject tree with maximum diameter (DDM) were related to diameter increment and the stand density measures, e.g. stand basal area (G), stand density index (SDI), and the basal area of larger trees than the subject tree (BAL). were not significantly influenced on diameter increment. As the relative diameter (RD and DDM) increase, tree's competitive capacity and diameter increment increase. As canopy closure (P) increase, tree increment decreases. The site conditions, such as site class index (SCI), slope, and aspect, were performance less of factors in increment predictions and were deleted from model. Using independent data set, validation measures were evaluated for predicting models of diameter increment developed in this study. The result indicated that the estimated precision values of diameter were all greater than 94% and the models were more applicable and suitable to describe diameter increment. In addition, mortality model for each species was developed based on logistic equation. Tree's diameter was significantly related to mortality. As diameter decrease, the mortality probability increases.The individual growth model developed in this study can actually reflect the tree increment of 15 species and be generally well suited for simulating tree and stand growth for natural mixed forests in the Baihe forest Bureau. Furthermore, it will provide detail information of tree increment to intensive forest management and decision-making for natural mixed forest. Therefore, this research has the theoretic foundation and practical value.