以山西省庞泉沟自然保护区华北落叶松天然次生林为研究对象,基于1 531株单木冠幅实测数据,对华北落叶松天然次生林单木冠幅预测模型展开研究。首先从9个常见的冠幅-直径候选模型中选出一个拟合精度较高的模型作为构建冠幅模型的基础模型;接着从林分测树因子、立地因子和林分竞争指标中选出与冠幅相关性较强的因子作为模型自变量进行建模;最后利用偏差、剩余均方根误差R和决定系数并结合似然比检验对模型进行检验与评价。结果为:三参数的逻辑斯蒂形式的冠幅-直径模型拟合精度较高,并且模型参数可解释,因此把该模型作为构建华北落叶松单木冠幅模型的基础模型;对象木冠长、林分密度和林木竞争压力指数与冠幅相关性较强,当基础模型中考虑这些因子时能进一步提高预测精度。所构建的冠幅模型可为华北落叶松天然次生林的科学经营提供理论基础和技术依据。
Larix principis-rupprechtii natural forest was taken as research object.Based on 1531 strains of individual tree crown width measured data,the study was conducted on the natural forest of larch wood single crown width model.Firstly from the nine common crown width diameter candidate models,a model with higher accuracy of fitting was selected as the basic model of crown width model,then from the tree size and vigor factor,site factors and stand competition factor were screened with the crown width of a strong correlation factors as independent variables in the model for modelling,finally,the model is tested and evaluated by using the deviation,the residual root mean square error R and the determination coefficient and combined with the likelihood ratio test.As a result,the 3 parameter logistic forms crown width diameter model fitting with highest accuracy,and the model parameters can be explained.Therefore,the model can be used as the basis of the model of Larix principis-rupprechtii single crown width model;the object of trees crown length,stand density and competition index has strong correlation with crown width.When these factors are considered in the basic model.the model can further improve the prediction accuracy.The crown width model constructed in this research fills the blank of Larix principis-rupprechtii natural individual tree crown width model.
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