利用Voronoi图评价油松人工林空间结构

Spatial structure of a Pinus tabulaeformis plantation based on the Voronoi diagram

为量化分析北京市八达岭油松Pinus tabulaeformis人工林森林空间布局特征,优化其生态系统结构,利用Delaunay三角网、 Voronoi图的地埋信息系统(GIS)方法确立各中心木的邻近木株数,并以此为基础划分森林空间结构单元,计算各单元的聚集指数、混交度、大小比数和开敞度,实现森林空间结构信息化调查和研究。结果表明:由Voronoi图创建空间结构单元的方法,是一种区别于传统固定邻近木株数为4的合理的方法;研究区中邻近木株数范围为3~11株,在9种边长个数不同的空间结构单元中,最常见的邻近木株数为6;经统计分析可得,研究区的空间结构参数均不符合正态分布;聚集指数为1,表明整体为一般聚集状态;全林分平均开敞度为0.52,林木生存空间充足;树种的平均大小比数为0.53,整体呈中庸态势,竞争程度一般,但林分间处于优势的油松个体占比较大,竞争能力较强。由于研究区所在林分并非人工纯林,树种混交度水平参差不齐,油松的平均混交度最弱为0.25,其余树种混交程度较强。总体上树种间隔离度较差,全林稳定性较弱。

To quantitatively analyze the characteristics of a forest spatial layout so as to optimize its ecosystem structure,a Pinus tabulaeformis plantation in Badaling,Beijing was studied.The number of adjacent trees for each central tree was confirmed using Delaunay triangulation,the Voronoi diagram,and GIS methods.Next,the forest spatial structural unit was determined with four parameters for each unit being calculated based on the Voronoi diagram:the aggregation index,the degree of mixing,neighborhood comparison,and the degree of openness.Then data was collected in each forest spatial structure with informatization.Results showed that creating a spatial structural unit using the Voronoi diagram was reasonable.The way is different from the method which fixes the number of the unit sides with 4.The number of adjacent trees was 3-11 with the most common number being six.Nine kinds of spatial structural units were found with a different number of sides.According to the statistical results,the parameters of the spatial structure in the study area did not have a normal distribution.Also,the aggregation index of the spatial structure was 1,or a general state of aggregation.Living space in the forest was sufficient because the average data for the degree of openness was 0.52.Moreover,the average neighborhood comparison for the whole study area was 0.53 which meant a general state with common competition even though the competitive ability of P.tabulaeformis was strong.Tree species were unevenly distributed with an average mixed degree of 0.25 for Pinus tabulaeformis,the poorest,with other species being better.In general,isolation of tree species was poor,and stability of the whole forest was weak.