Institute of Forest Resource Information Techniques, Chinese Academy of Forestry, Beijing, 100091, China.
Sci Rep. 2024 Aug 12;14(1):18695. doi: 10.1038/s41598-024-69675-y.
Individual modelling is a foundational approach to study the natural forest growth and in this paper, we develop a serial distance-depended individual tree model for some species in natural forest which would provide prediction and characteristics for natural species. The data used to develop individual model for natural mixed forests were collected from 712 remeasured 10-year periodic permanent sample plots of in Baihe Forest Bureau of Changbai Mountains, northeast China. Based on analyzing relationship between diameter increment of individual trees with tree size, competitive status, and site condition and finding out the major independent variables, the growth models for individual trees of 15 species in the natural mixed forests, that have good predicting precision, and easily applicable, were developed using stepwise regression method. The individual growth model developed in this study can reflect the tree increment of 15 species and be generally well suited for simulating tree and stand growth for natural mixed forests in Changbai Mountains. The research results for individual trees growth model of each species showed that main variable to influence on diameter increment of individual trees for natural mixed forests were tree size (D) and then competition index. The site condition was not related with diameter increment. The natural logarithm of DBH (lnD) and square diameter (D) were included in the predicting models of diameter increment for all 15 species. The diameter increment was directly proportional to tree diameter for each species. For the competitive indexes in growth model, the relative diameter (RD), canopy closure (P), and the ratio of diameter of subject tree with maximum diameter (DDM) were related to diameter increment and the stand density measures were not significantly influenced on diameter increment. As canopy closure increase, tree increment decreases. The site conditions were performance less of factors in increment predictions in the model.
个体建模是研究天然林生长的基础方法，本文为天然林中的一些物种开发了一个连续距离依赖的个体树模型，该模型将为天然物种提供预测和特征。用于为天然混交林开发个体模型的数据是从中国东北长白山白河林业局的 712 个重新测量的 10 年定期永久性样地中收集的。通过分析个体树的直径增量与树木大小、竞争状态和立地条件之间的关系，并找出主要的独立变量，使用逐步回归法为天然混交林中的 15 个树种开发了具有良好预测精度和易于应用的个体树生长模型。本研究中开发的个体生长模型可以反映 15 个树种的树木增量，并且通常非常适合模拟长白山天然混交林的树木和林分生长。每个树种的个体树生长模型的研究结果表明，影响天然混交林个体树木直径增量的主要变量是树木大小（D），然后是竞争指数。立地条件与直径增量无关。自然对数的 DBH（lnD）和平方直径（D）被包含在所有 15 个物种的直径增量预测模型中。直径增量与每个物种的树木直径成正比。对于生长模型中的竞争指数，相对直径（RD）、冠层闭合度（P）和最大直径的主体树的直径比（DDM）与直径增量有关，而林分密度测度对直径增量的影响不大。随着冠层闭合度的增加，树木增量减少。在模型中，立地条件对增量预测的影响较小。
