基于Voronoi图的林分空间模型及分布格局研究

以南洞庭湖龙虎山次生林为研究对象,建立林分Voronoi图模型,通过该模型表示林分空间结构特征,提取林木空间量化信息。在此基础上,引入变异系数量化Voronoi多边形面积的变化率,将林木空间格局分析转化为计算Voronoi图变异系数,并将计算结果与角尺度作相关性比较。结果表明:林分Voronoi图模型能准确表达林木邻接关系、相邻木距离及角度、空间密度等重要空间信息;大尺度取样时(76m以上),变异系数趋于稳定,林分整体空间格局呈接近随机分布的轻度聚集;Voronoi图变异系数和角尺度存在显著的正相关关系,进一步说明本研究格局分析方法的可行性和有效性;受多种因素影响,乔木层主要树种在不同发育阶段的空间格局表现出强烈的时间和空间动态特性,且小径木多为聚集分布,大径木呈轻度聚集或随机分布。基于Voronoi图的林分空间模型及格局分析方法,从空间上表征林木的生长繁育特性、种内种间关系、资源及环境分布特征,为计算几何方法应用于林分空间经营提供了新的思路。

The stand spatial model and pattern based on voronoi diagram

The secondary forest of Mt.Longhu in the south Dongting Lake is chosen as the research object in this paper which tries to establish a stand model based on Voronoi diagram. This diagarm is applied here to illustrates the stand spatial structure and extract forest spatial quantitative information. Based on this, coefficient of variation (CV) is used to quantify the change rate of Voronoi polygon area, transferring the analytic results of stand spatial pattern to the calculation of the CV based on Voronoi diagram, and comparing the calculation results with uniform angle index. The result shows that the stand model of Voronoi diagram can accurately display some important spatial information, such as the correlation, distance and angle between adjacent trees as well as spatial density, etc. When sampling large scale(above 76m), CV tends to remain stable, and the overall stand spatial pattern shows mild aggregation which is close to random distribution. The CV of Voronoi diagram and uniform angle index have notable positive correlation, which further proves the feasibility and effectiveness of the analytical methods applied in this paper.The spatial pattern of main tree species of abor layer in different development stages shows a distinct temporal and spatial dynamic characteristics due to many factors. The small-diameter wood belongs to aggregated distribution, while the large-diameter belongs to mild aggregation or random distribution. The stand spatial model and its pattern analytical method, both based on Voronoi diagram, charaterize the tree growth feature, intraspecific and interspecific relationship, characteristics of resources and enviornment distribution from the perspective of spatial structure, providing a new way of thinking for stand spatial management by applying computational geometry method.