基于加权Voronoi图的杉木生态公益林空间结构分析

Analysis on spatial structure of Cunninghamia lanceolata non-commercial forest based on weighted Voronoi diagram

以湖南省福寿国有林场杉木生态公益林为研究对象,通过将林木胸径、树高和冠幅作为综合权重,改进Voronoi图确定林木的邻近木,进而计算各空间结构指数,分析林分的空间结构特征。结果表明:林木空间结构以1株中心木与5株邻近木组成的空间结构单元最为常见,林木空间影响范围随综合权重的增加而增加;不同林龄杉木林树种空间隔离程度均较低,幼龄林全林分平均混交度为0.34,属于中度混交,中龄林和近熟林全林分平均混交度分别为0.17和0.23,为弱度混交;3种不同林龄的优势树种杉木的平均胸径大小比数均为0.50左右,表明林分处于中等竞争状态;各样地平均角尺度均小于0.475,表明不同林龄杉木林林木均处于均匀分布状态。

To analyze the spatial structure characteristics of Cunninghamia lanceolata non-commercial forest in Fushou State-owned Forest Farm in Hunan province, the DBH, tree height and crown-width of China fir in the forest farm were taken as the comprehensive weight values to built a weighted Voronoi diagram. Then adjacent tree of the object tree was determined according to the improved weighted Voronoi diagram, and the mingling degree, neighborhood comparison and aggregation index were further calculated based on the weighted Voronoi diagram. The results show that the most common spatial structure unit was one object tree with five close neighboring trees, and the spatial influenced region of individual tree increased with the increase of comprehensive weight value; the average mingling degree of the young stand was 0.34, belonging to moderate mixed, the average mingling degree of the middle-aged and nearly-mature stand were 0.17 and 0.23 respectively, both belonged to weak degree mixed, which indicated that the segregation of tree species in C.lanceolata stand with three different ages was low; the average neighborhood comparisons of C.lanceolata which is the dominant plant of three different ages stand were 0.50 or so, the stand belonged to the medium competition state; the average uniform angel indexes of all sample plots were less than 0.475, the trees presented a regular distribution.