基于混合效应模型的兴安落叶松人工林单木冠幅模型构建OA

Based on dendrometric measurements from 12 permanent sample plots in Shuangfeng Forest Farm,Hegang City,Heilongjiang Province,a crown projection area model for individual trees in Larix gmelinii plantations was devel-oped.The relationships between crown projection area and factors including DBH,height-to-diameter ratio,and crown length ratio were analyzed through correlation analysis.The optimal model was selected from six common linear and non-linear candidate crown-DBH models.Single-tree variables were incorporated into this base model,and plot-level random effects were added to construct a mixed-effects model for individual-tree crown projection area in Larix gmelinii planta-tions.The developed crown models were evaluated and validated.The results indicated that crown projection area showed positive correlations with DBH and crown length ratio but a negative correlation with height-to-diameter ratio.The optimal base model was a linear function with R2a of 0.515 6.After incorporating height-to-diameter ratio and crown length ratio,the generalized linear model achieved R2a of 0.597 8.Based on this model,the mixed-effects model includ-ing plot-level random effects further improved the fit,yielding R2a of 0.629 7.Model validation and evaluation confirmed that the mixed-effects model demonstrated superior predictive performance.The developed Larix gmelinii plantations mixed-effects crown projection area model-incorporating DBH,height-to-diameter ratio,crown length ratio,and plot-level random effects exhibits excellent goodness-of-fit and precise predictive capability.With broad applicability and sig-nificant biological interpretation,this model provides a theoretical foundation for accurately predicting crown dimensions in Larix gmelinii plantations across Northeast China.