Abstract:

Using knot analysis data of 95 sample trees in 19 sample plots of larch(Larix spp.) plantation in northeast Heilongjiang Province(5 sample trees were selected in each sample plot), the models for predicting knot variables, including knot diameter, angle and length, were developed based on the linear mixed effect model. The results showed that the knot diameter, angle and length increased as DBH increasing. When knot height increased, knot diameter increased firstly, and then decreased, and knot angle decreased gradually. The knot length increased with knot diameter increasing. Comparing with fixed effects model, the mixed effect based knot size models can obtain more accurate parameter estimates,the residual distribution of the model was more uniform, and the fitting precision of models were obviously improved(the R² value improved about 0.3).The results of independent validation showed that prediction precision of each model reached above 90%. Therefore, knot models developed in this paper can suitably describe the knots variation for larch plantation.

Key words: larch plantation, knot diameter, knot angle, knot length, mixed effect model