基于空间结构的杉木枝下高可视化模拟研究

【目的】定量研究林分空间结构对杉木枝下高的影响,构建基于空间结构的枝下高模型,结合杉木生长模型,应用三维可视化技术,实现杉木枝下高可视化模拟。【方法】利用湖南省黄丰桥国有林场6块杉木人工林临时样地的调查数据,选择5个常用枝下高基础模型,分析水平空间结构参数(P_H)、垂直空间结构参数(P_V)和空间结构单元平均距离(d_DIS)及其组合对枝下高的影响,构建综合指标较好且变量少的枝下高模型。基于林分三维模型实时生成方法,建立一种枝干可控的杉木三维模型;结合单木胸径连年生长量模型、树高-曲线模型和冠幅面积估计模型,模拟林木的生长状态。【结果】Logistic模型综合指标较好且模型参数可解释,可选为基础模型;3个空间结构参数中垂直空间结构影响较为显著,将P_V加入到Logistic模型中,改善了枝下高模型的拟合效果,决定系数(R²)从0.717提升到0.741,估计值的标准差从1.407 m减小到1.321 m,并使各项模型检验误差指标有所减小;构建的杉木三维模型可以动态调节枝干,实现了杉木枝下高模拟。【结论】构建的枝下高模型可以应用于林木年龄和部分林分信息未知的杉木林中,体现了林木间的相互竞争影响;结合枝干可控的杉木三维模型,模拟杉木生长过程,形象直观地表现了杉木枝下高的变化,为进一步研究林分生长动态可视化模拟和森林经营可视化模拟提供支持。

Visual simulation of Chinese fir under branch height in consideration of spatial structure

【Objective】This study quantitatively investigated the effect of spatial structure on the under-branch height of Chinese fir(Cunninghamia lanceolata),to build a model of Chinese fir under-branch height.The spatial structure combined with the fir growth model,three-dimensional(3 D)visualization technology was applied to visually simulate the height of fir branches.【Method】Using survey data of six temporary sample plots of Chinese fir plantations in the Huangfengqiao State-owned Forest Farm in Hunan Province,China;five commonly used branch height foundation models were selected to analyze horizontal spatial structure parameters(P_H),vertical spatial structure parameters(P_H),and spatial structure unit average distance(d_DIS).The influence of this combination on the height of branches was constructed with better comprehensive indicators and fewer variables.【Result】The Logistic model showed better comprehensive indicators and explanatory model parameters;as such,it was selected as the basic model.Among the three spatial structure parameters,the vertical spatial structure(P_H)had a significant impact(R;=0.741).Adding vertical spatial structure parameters to the Logistic model improved the simulation of the sub-branch height model.As a result,the coefficient of determination(R²)increased from 0.717 to 0.741,the standard deviation of the estimate reduced from 1.407 to 1.321 m,and various model inspection error indicators were reduced.【Conclusion】The under-branch height model constructed in this study may be applied to Chinese fir forests of unknown tree age and partial stand information,reflecting the mutual competition among forest trees and visually and intuitively expresses changes in the height of fir branches,and supports further research on the visual simulation of forest stand growth dynamics and forest management.