油松人工林单木邻体竞争模型

Individual adjacent competition model of Pinus tabuliformis plantation

研究林木个体间竞争关系,建立以保留木为对象的单木邻体竞争模型对于人工林的抚育经营具有重要的作用。本研究以北京西山试验林场油松人工林为研究对象,采用改进的Hegyi竞争指数分析林木的竞争强度;以对象木胸径和空间相对位置为参数构造加权Voronoi图,选择S_i=n∑j = 1λ(α_(ij)-α_i)~a/L^b作为模型表达式,分析对象木与邻近的少数林木(3株或4株)之间的竞争关系并建立邻体竞争模型。结果表明,油松人工林林木间竞争较剧烈,密度越大、坡位越低的林分中林木间的竞争越强。以胸径和冠幅作为自变量构造的单木竞争模型具有较低的标准误,3-邻体竞争模型和4-邻体竞争模型的相关性分别为0.83和0.84。本研究基于Voronoi图和林冠面积建立单木邻体竞争模型,为优化林分空间结构、提高森林质量的单株木抚育择伐经营技术提供参考。

Understanding and modeling the competition relationships of individual trees play an important role in tending of forest plantation. A study was performed to calculate the competition of individual trees of Pinus tabuliformis plantation in Xishan Experiment Forest Farm, Beijing. The competitive intensity was analyzed by modified Hegyi index, and the weighted Voronoi diagram of objective trees was mapped by DBH and relative spatial position in order to determine its competition unit. Take formula Si=∑j=1^nλ（αij-αi）^a/L^-b as reference to model the competition relationship between an objective tree and other 3 or 4 nearest trees. The results showed that the competition of individual trees was high, especially in plantation with high density and lower slope position. Model combining with the DBH and crown diameter had a lower standard error, with the estimation effects （R^2） of 0.83 and 0.84 for 3- and 4- neighborhood competition model, respectively. Based on the analysis of overlapping area of Voronoi diagram and crown canopy, the adjacent competition model of individuals provided a reference for stand structure optimizing and thinning in forest management.