Stusy On Forest Dynamic Model For Larix In Plantation

Based on the data of stem analysis,branch analysis,and knot characteristics from 95 sample trees in 19 sample plots for Larix olgensis Hengy plantations with different age, different stand density,and different site,the total number,spatial distribution and development process of branches in crown under different forest conditions were discussed in this paper. Dead branches or knots in different sizes of tree was studied and different branch development phases of growth,suppression,death and self-pruning was analyzed to evaluate the effect that knot size and distribution impact on timber quality.Branch and knot dynamic models were developed using stand and tree variables.Based on multipleunit stepwise regression method, the individual tree growth model was established using forest and crown factors as the variable. The best taper equation model of Larix olgensis was bucking data of 130 sample trees selected in the studied area.The effect of forest condition on step form was analyzed and proper pruning heightand relevant management measures were determined to control dead branch and knot size along the stem and improve timber quality.The results are followed:1.The branch numbers in every whorl does not relate with forest conditions and they are affected by genetic factors.It obeys normal distribution with average value is 5.There is a adjacent peak and valley of branch number in the vertical distribution of primary branches and uniform distribution was appropriate to reflect branching pattern around the bole.Branch angle is related with the depth into crown(DINC).It increased with the increseament of DINC. There are large branch angles in the middle of crown with smaller value and few in the lower crown with larger value.2.The total number of branch is the function of DBH.And the variables of DBH and HT can reflect the diversity of crown structure.Branch size is mainly related with its depth of crown(DINC),DBH and HT.The linear model with variables of DINC,DBH and HT can predict the branch diameter and length.Based on the Mistcherlic and Richards theory growth equation,the variables of AGE,DBH and HT were introduced to established branch dynamic models to predict the growth of branch diameter and length.3.The average value of knot diameter(KDmean) increased with the increasing of knot height and the biggest knots were located in the middle of stem,which is about 12m.The Shumacher equation can predict KDmean with the variables of HK,DBH and crown.The tree diameter at breast height(DBH) and crown length(CL) can be used to predict the size and location of mean knot diameter in a whorl.A linear mixed model expressed as function of tree and knot variables such as HK,RKD,KD and DBH was used to predict sound knot length(KLsound),and a log-linear mixed model using RKD and DBH as variables was used to describe loose knot length(KLloose).4.A knot has four development phases:from the birth of a branch to its growth cessation (BC),from growth cessation to death(CD),form death to occlusion(DO) and form birth to occlusion(BO).The numbers of annual rings in four periods,as well as the stem width of respective zones were used as dependent variables predicted by models expressed as function of tree variables and knot attributes.5.Using the data of diameter out side bark of 15 relative heights along the step,the best taper equation for Larix olgensis was established.It can improve the precision of using taper equation to simulate the step form diversity.It also can predict the diameter inside bark of the trees or the timber length of the trees of different size.6.The individual tree growth model using the tree size(D),relative diameter(RD), crown width(CW),crown length ratio(CR) and site quality(SCI) as variables was established. The model showed that the trees with larger crown width in a forest with good site quality and the trees has large relative diameter,usually has large diameter increase for higher photosynthesis efficiency.7.The forest density has some effect on tree step form.The step form is good in the forest with larger density and the proper forest density can improve the step form.According to the method of branch relative growth curve,the first pruning of Larix olgensis is about 15 years and the intension is about 40%to 50%.6.The individual tree growth model using the tree size(D),relative diameter(RD), crown width(CW) and site quality(SCI) as variables was established.The model showed that the trees with larger crown width in a forest with good site quality and the trees has large relative diameter,usually has large diameter increase for higher photosynthesis efficiency.7.The forest density has some effect on tree step form.The step form is good in the forest with larger density and the proper forest density can improve the step form.According to the method of branch relative growth curve,the first pruning of Larix olgensis is about 15 years and the intension is about 40%to 50%.These results can provide theory base and management method for improving forest increment and timber quality which is of great significance.