Simulation On Stem Taper Of Dahurian Larch Based On Crown Characteristics

In this study, the sample data was based on114sample trees from dahurian larch(Larix gmelinii Rupr.) plantations located in Qitaihe Forest Bureau in Heilongjiang Province, northeastern China. On the basis of date survey on crown factors and stem taper data, make a quantitative analysis and simulation on crown characteristic factors and influence on stem taper using forest management, mathematical statistics and mathematic model. Based on the scatter plots between the crown factors and individual tree factors, we make analysis to the scatter plots and to test the correlation relationship between crown and individual tree factors.10kinds of classic linear and nonlinear model were used to construct the crown factors model and the fitting results showed that the correlation coefficient of crown width was relative high based on the model of binomial. Meanwhile, the correlation coefficient for the Logistic model of crown length fitting was high. The crown ratio model based on the Gompertz model had well fitting results. The Max-Burkhart segmented taper equation was fitted using nonlinear mixed-effects modeling techniques by SAS software PROC NLMIXED module. We can found that random parameter b1showed negative correlation with crown ratio and crown length, and positive correlation with crown height. Random parameter b2showed positive correlation with crown ratio and crown length, and negative correlation with crown height. Random parameter b3did not show any correlation with crown ratio, crown length and crown height. Three taper equations including crown ratio, crown length and crown height variables were developed based on these correlations. Significant test of parameter estimates indicated that crown ratio, crown length and crown height had significant effects on stem taper. A series of taper curves were generated based on the stem taper equation with crown ratio. It shows that trees of the same relative size but with a larger crown ratio generally have a bigger stem taper, lower stem profile quality.