The Study On Individual Tree Growth Models For Larix Olgensis Plantation

The data used to develop individual model for Larix olgensis plantation were collected from 5 periodic permanent sample plots of 5-year periodic from 1994 to 1999 and 2004-2009 in Mengjiagang Forest, Based on analyzing relationship between diameter basal area increment of individual trees with tree surveying factors and choosing tree relative diameter(RD) and the effective crown surface area(ECSA) as competitive index, the growth models for distance-independent individual trees of Larix olgensis plantation, that have simple form, good predicting precision, and easily applicable, were developed using stepwise regression method.In this paper, the individual tree height curve of Larix olgensis in different site conditions was fitted with the model which was chosen according to experienced models, with the data of 95 analysis trees in 19 permanent plots of 2007-2008. The relationship between parameter and surveying stand factors was obtained and then the individual tree height curve model was established finally with the method of re-parameterization. Besides, the individual tree mortality probability model for Larix olgensis plantation had been developed based on Logistic equation.The research results showed that the individual height of effective crown (HEC) of Larix olgensis plantation had the greatest positive correlation with height (H), and negative correlation with crown ratio (CR). The effective crown surface area(ECSA) had power function with individual diameter(D),HEC and effective crown length(ECL). ECSA had the greatest positive correlation with effective crown length (ECL), positive proportional relationship with D, negative with HEC. Then employing ECSA as a competitive index, distance-independent individual growth model of basal area of Larix olgensis plantation was set up by multiple stepwise regressions. Then, the comparison of non-ECSA and ECSA individual growth model was made. The results showed that the multiple correlation coefficients were improved 3.2% and the accuracy of model was improved 0.03% after introducing ECSA. Therefore, the effective crown surface area (ECSA), which has influence on individual growth, can enhance the fitting effect of individual models as individual competition index.In this study, the Richards theoretical model was chosen as the basic model for individual height curve model of Larix olgensis plantation, a linear relationship between the parameters and stand site class index (SCI) was found, however unobvious with age and density. Finally, the individual height curve model was built as follows: H= (12.38025+0.74079SCI)(1-e-0.05D)0.66529+1.3The advantage of this mode1 was that D could be equaled to zero when H was less than 1.3, conforming to the biological characteristic of tree growth. Besides, the diameter of trees was significantly related to mortality from the individual tree mortality probability model. As diameter decrease, the mortality probability of individual increased.The individual tree growth models developed in this study can actually reflect the tree increment of Larix olgensis plantation of Mengjiagang Forest, and it could imitate the growth process of individual tree well. Furthermore, it will provide detail information of tree increment to intensive the forest management and decision-making for Larix olgensis plantation. Therefore, this research had the theoretic foundation and practical values.