Abstract: The sample data was from dahurian larch (Larix gmelinii（Rupr.）Rupr.) plantations located in Daqingchuan and Yongcui Forest Farms, Dailing Forest Bureau in Heilongjiang Province. Height-diameter model with stand variables was developed based on sample data from 41 plots and Richards’s model. A mixed-effect modeling approach was applied in fitting Richards’s model y_ij=(β₁+b_i1)(1-e^{-(β₂+b_i2)x_ij})^(β₃+b_i3)+ε_ij and the same model with stand variables y_ij=(β₁+b_i1)(D_q)^(β₂+b_i2)(1-e^{-(β₃+b_i3)(N(β₄+b_i4))x_ij})+ε_ij. Results showed that Richards model with inclusion of random parameters b₁, b₂ was the best when fitting mixed-effects model of Richards; Inclusion of random parameters b₂, b₄ was the best when fitting Richards model with stand variables. Model validation indicated that mixed model showed lower error than fixed-effects model when randomly selected independent samples. However, using calibration with randomly selected four trees, mixed model reduced the bias and RMSE of the prediction by almost 71.8% and 42.1%, respectively.

Key words: height-diameter model, mixed effects, plot effect, Larix gmelinii