Study On The Dynamic Modeling Of Larch Plantation

Larch plantation, which has the characteristics of fast-growing, high-yield and high- quality, is the major plantation tree species in north China. Dynamic modeling of Larch plantation can provide rational and practical stand dynamic information for its intensive management, of which include to develop Larch plantation to solve wood crisis partly. Based on the site classification and site evaluation, the matrix models (size class model) and individual tree growth model was developed in this paper. The main research content and result are given as follows: Site classification and site evaluation Larch plantation was classified six site types namely top-positive central-positive lower-positive top-negative central-negative and lower-negative by two dominant factors lope direction and slope location. Their corresponding site index are 8.95m lO.37m 12.02m. I3.24m l4.lOm andl5.75m, respectively. The result showed that negative slopes site index was higher than that of positive slope, and to same slope direction the lower part was higher than the central and than the top. Matrix model Tree mortality model was constructed by Logistic regression. Then transition probability parameter(a b) was cumulated on the basis of the mortality probability(m). Upgrowth parameter (d) can be obtained by bivariate linear function. According to the transition probability matrix combining with stand original distribution, the change of stand structure in fifteen years was modeled. The result showed that the amount of tree in small size-class decreased slowly, while the tree in big size-class increased steadily. Individual tree growth model Because diameter directly affects tree growth, this paper used planting-distance index (RS) and relative diameter (RD0) as distance- independent individual tree competition index. Based on Chapman-Richards equation, the distance-independent individual tree model was developed to predict individual tree basal area growth of Larch plantation. Using this model and combining with height- diameter curve. individual tree mortality probability model and individual tree volume equation, stand dynamics can be better simulated for unthinned Larch plantation.