The Study On The Individual Tree Growth Models Of The Natural Secondary Forest In Maoershan Forest Region

The data used to develop individual model for natural secondary forests were collected from remeasured permanent sample plots in Maoershan experimental forest farm of NEFU, northeast China. the major independent variables have been pick up from many variations by correlation analysis between diameter increment of individual trees with tree size, competitive status, and site condition .The growth models for individual trees of 10 species in the natural secondary forests have been developed using stepwise regression method.The research results of individual trees growth model of each species showed that the main variable which influence on the section area increment at breast height of individual trees for natural secondary forests was tree size and then competition indexes. The site condition was slightly related with diameter increment. The natural logarithm of DBH (lnD) and square diameter (D~2) were included in the predicting models of breast height section area increment for all the 10 species. The diameter increment was directly proportional to tree diameter for each species. For the competitive indexes in the growth models mean of the relative canopy width (MRCW), the relative diameter (RDI), and the competitive pressure index (CSI) were related to the breast height section area increment and the other stand density measures, such as stand canopy closure (P), stand density index (SDI), and the basal area of larger trees than the aimed tree (GL), were not significantly influenced on breast height section area increment. As the relative diameter (RD and DDM) increase, tree's competitive capacity and diameter increment increase. The site conditions, such as site class index (SCI), slope, and aspect, were performance less important in increment predictions and were seldom introduced in the final models. 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 85% and the models were more applicable and suitable to describe breast height section area increment,In addition, the individual tree mortality model for some species was developed based on the logistic equation. Tree's diameter was significantly related to mortality. As diameter decrease, the mortality probability of every species increases.The individual tree growth model developed in this study can actually reflect the tree increment of the 10 species and be generally suited for simulating tree and stand growth for natural secondary forests in the Maoershan experimental forest farm. Furthermore, it will provide detail information of tree increment to intensive the forest management and decision-making for natural mixed forest. Therefore, this research has the theoretic foundation and practical value.