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林分密度和立地条件及其交互作用对长白落叶松人工林树高-胸径模型的影响

Interaction Effects of Stand Density and Site Conditions on the Height–Diameter Model of Larix olgensis Plantations

    摘要
  • 摘要:
    目的 深入理解林分密度和立地条件对张广才岭林区长白落叶松人工林单木树高-胸径曲线的影响，为该地区长白落叶松人工林的可持续经营提供理论和技术支撑。
    方法 本研究以东北林业大学帽儿山实验林场和哈尔滨市胜利实验林场共71块固定样地数据为基础，采用赤池信息准则（AIC）和贝叶斯信息准则（BIC）选取最佳树高-胸径基础模型，并在此基础上进一步引入林分密度指数（SDI）和立地指数（SI）构建单一效应模型和交互效应模型。最终，采用调整决定系数（Adjusted R2）、均方根误差百分比（RMSE%）和平均绝对误差百分比（MAE%）检验不同变量对长白落叶松人工林单木树高-胸径曲线的影响。
    结果 长白落叶松人工林树高-胸径曲线的最佳基础模型为幂函数方程（ H=1.3 + b_1D^b_2 ）；在参数b1、b2中引入SDI和SI，可得到2个最佳的单一效应模型，而同时在参数b1和b2引入SDI和SI可构建出最佳交互效应模型。与基础模型相比，SDI和SI单一效应模型的Adjusted R2值分别提升4.98%和3.87%，而交互效应模型的Adjusted R2值则可提升7.38%。模型拟合结果表明，当培育胸径为30 cm时，较高SI等级下SDI对树高的提升作用约为11.57%，而较低SI等级下SDI对树高的提升作用则仅为2.01%，相同等级提升幅度下（由2级升至3级），SI对树高的提升幅度最大达到11.57%，高于SDI的8.07%，差值为3.50%。
    结论 林分密度与立地条件间存在显著的交互作用，其交互作用比单一因素随机效应更能解释林分高度的变化，树高随SDI等级和SI等级的增加整体呈上升趋势，立地条件在树高对林分密度变化的响应中起主导作用。因此，本研究结果有助于提高长白落叶松人工林树高预估精度，并可为其他树种相关的科学研究提供参考。

     

    Abstract:
    Objective To understand the effects of stand density and site conditions on tree height-diameter (H-D) relationship of Larix olgensis plantations in the Zhangguangcai Mountain region, and to provide theoretical and technical support for the sustainable management of Larix olgensis plantations in this area.
    Methods Based on data from 71 permanent plots in the Maoershan Experimental Forest and Shengli Experimental Forest of Northeast Forestry University, the optimal H-D base model was selected using Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). Then, stand density (SDI) and site index (SI) were introduced to construct single-effect models and an interaction-effect model. Model performance was evaluated using adjusted coefficient of determination (Adjusted R2), root mean square error percentage (RMSE%), and mean absolute error percentage (MAE%).
    Results The optimal base model was the power function ( H=1.3 + b_1D^b_2 ). Introducing SDI and SI into parameters b1 and b2, two optimal single-effect models can be obtained. A further interaction-effect model was developed by including both SDI and SI simultaneously b1 and b2. Compared to the base model, the single-effect models incorporating SDI and SI improved the Adjusted R2 by 4.98% and 3.87%, respectively, while the interaction-effect model improved the Adjusted R2 by 7.38%. When cultivated DBH was fixed at 30 cm, the contribution of SDI to tree height increased by approximately 11.57% under high SI conditions, but only by 2.01% under low SI conditions. For the same increment in level (from level 2 to level 3), SI led to an 11.57% increase in tree height, outperforming the 8.07% increase attributed to SDI by a margin of 3.50%.
    Conclusion There exists a significant interaction between stand density and site conditions, and this interaction explains the variation in stand height more effectively than random effects of either factor. Tree height increases with higher SDI and SI levels, and site quality plays a dominant role in mediating the response of tree height to changes in stand density. Therefore, the findings of this study can help improve the prediction accuracy of Larix olgensis tree height, and also provide a reference for related research on other tree species.

     

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