Abstract: Based on the re-easured data between 2007-2009 from 14 permanent sample plots in larch plantations located in Mengjiagang Forest Farm, Jiamusi city of Heilongjiang province, the relationship between crown variables and increment of tree was analyzed and the distance-ependent individual tree growth model for larch plantation was developed by introducing two crown competition factors (CI_a and CI_b) as new competition index in this paper. The results showed that two crown competition factors (CI_a and CI_b) are better than the Hegyi competition index (CI). The correlation between various competition index with basal area increment of individual tree is CI_b>CI_a>CI for larch plantation. With enlargement of the competition influence zone of object tree, the competition index tends to be stable and the model fitting effect increases. Tee size is the main affecting factor for the individual tree growth for larch plantation. The basal area increment of individual tree increases as tree diameter at breast height increasing. The goodness of fit for individual tree growth model was improved 5.6% by introducing new distance-ependent crown competition index. The distance-ependent individual tree growth model developed in this paper can be suitable for predicting basal area increment of individual tree for larch plantation.

Key words: larch plantation, crown competition factor, individual tree growth model