Abstract:

By means of both asymptotic stable and actual change process of coefficient variation of the diameter(CVD), the compatible CVD model is proposed so as to link three type models (whole stand, size class and individual tree) and better reflect the effect of thinning on forest tree differentiation in the stand. Taking Larix olgensis Henry as an example, the fittings and analyses are carried out for the compatible model, CVD dynamic model without thinning factors and diameter variance model. The result has shown that the compatible model has the best fitting precision among the three models. The compatible CVD model has many desired properties such as compatibility, invariance for projection length, and mechanism, and has clearer biological and mathematical meanings in parameters of the model. There are two conclusions in the description of CVD dynamic changes of thinned and unthinned even-aged stands in different thinning systems: 1) when stand is not thinned, the initial value of CVD determines the direction of CVD curve, if the initial value is higher than the tendency value of CVD, the CVD curve will decrease monotonously, conversely, the CVD curve will be monotone increasing. 2) Thinning intensity affects the speed towards to tendency value of CVD. The more the thinning intensity, the slower speed of tending to the tendency value of CVD and the longer the time needed.

Key words: Diameter, Coefficient of variation, Compatibility, Dynamic model, Larix olgensis Henry