A Study Of Prediction Model Variation Of Larch Branches

In this study, based on the data of293sample trees of11plots from Dahurian larch (Larix gmelini Rupr.) plantations located in Wuying Forest Bureau in Heilongjiang Province, analysis and describes the larch plantation growth and development of different stand conditions. According to the scatter trend, selected fitting degree optimal tree height curve model from the empirical equation THT=32.0371·(1-e-0.05·DBH)1.044218+1.3.the stepwise regression techniques were used to develop a crown length model:CL=1.6622+0.2922·DBH. Used stepwise regression analysis and obtained the data of2190branch diameter samples of30trees from Dahurian larch (Larix gmelini Rupr.), Use of branches and trees of different variables built branches growth models. The model included total number of branches per tree, branch chord length and branch arch height. The optimal total number of branches per tree model is NBR=1.188955×DBH+2.562554×THT. Branch chord length is BCL=-0.0728+0.9292BL. Branch arch height is BAH=0.243114×BL0.864351. For branch diameter,branch length and branch angle, we used linear mixed model to study, the stepwise regression techniques were used to develop a branch diameter model:BD=b1+b2DINC+b3DINC2+b4DBH·DINC2. Branch length model is BL=b1+b2DINC+b3DINC2+b4DBH·DINC2. Branch angle is BA=b1+b2DINC+b3DINC2+b4DBH·DINC. The developed model was fitted using linear mixed-effects modeling approach based on LME procedure of S-PLUS software. Evaluation statistics, such as AIC, BIC, Log Likelihood and likelihood ratio test were used for model comparisons. The results indicated that the branch diameter model with parameters b1, b2, b3as mixed effects showed the best performance. Exponential and power functions were incorporated into the mixed branch diameter model. The addition of the power function significantly improved the mixed-effects model. The plots of residuals indicated that the mixed-effects model with power function showed more homogeneous residual variance than the mixed-effects model. Branch diameters increased with the depth into crown (DINC) increasing for trees with similar DBH. Branch diameters increased with the DBH increasing for different trees. DBH is adequate variable of tree for describing branch diameter variations with different trees. Branch diameters can be predicted from the measurement of some tree-level variables without detailed knowledge of the stand history for Dahurian larch plantations. The results showed that the branch length and branch angle models with parameters b1, b2, b3as mixed effects showed the best performance. Exponential and power functions were incorporated into mixed branch length and branch angle model. The addition of the exponential and power functions significantly improved the mixed-effects model. The plots of standardized residuals indicated that the mixed-effects model with exponential and power functions showed more homogeneous residual variance than the mixed-effects model. Validation confirmed that the mixed model with calibration of random parameters could provide more accurate and precise prediction. Therefore, the application of mixed model not only showed the mean trends of branch length and branch angle, but also showed the individual difference based on variance-covariance structure.