基于空间结构优化的采伐木确定方法研究

摘要

以吉林省汪清林业局金沟岭林场天然云冷杉林标准地内147株树木为研究对象,选用最近邻木取4的传统方法和Voronoi图来确定每株树木的最近邻木株数和树号,对2种方法计算出的混交度、大小比数和角尺度进行比较,在调整角尺度的基础上调整混交度和大小比数并结合临界距离确定采伐木,并且对Voronoi图的适用性进行评价.结果表明,根据2种确定最近邻木的方法计算出的混交度和大小比数较为一致,同为有效数据,但是最近邻木取4计算出的混交度和大小比数偏小;基于Voronoi图确定最近邻木计算的角尺度与最近邻木取4计算出的角尺度相差较大.根据Voronoi图计算的角尺度、混交度和大小比数选择采伐木并结合临界距离确定采伐木,基于Voronoi图计算的采伐后的角尺度增大,林木聚集程度增大,其他指标均改善,按照最近邻木取4计算的空间结构参数均改善.因此,根据Voronoi图计算混交度和大小比数是比较合理的,但是计算角尺度时误差较大,必须结合应用较为普遍的指标进行验证.%Based on the 147 trees within the sample plots of natural mixed spruce-fir forest which was located in Jingou Forestry Farm administrated by Wangqing Forestry Bureau in Jilin Province, China, this paper compared the outcomes of calculating the spatial structure indices based on Voronoi diagram (VD) and the outcomes of traditional method in which the number of the nearest neighbor trees was 4 (FT). Uniform angle index was taken as the first optimization target, mingling and neighborhood comparison were adjusted at the same time. Cutting trees were determined according to the spatial structure indices and critical distance, and the applicability of VD was evaluated. The results showed that mingling and neighborhood comparison calculated based on VD and FT were consistent, both belonged to effective data. However, mingling and neighborhood comparison calculated based on FT were lower than the outcomes of the VD, uniform angle index calculated based on VD differed significantly with those calculated based FT. Cutting trees determined according to spatial structure indices calculated based on VD and critical distance, mingling and neighborhood comparison were improved after thinning but uniform angle index was not. Spatial structure indices calculated based on FT were improved after thinning. Overall, mingling and neighborhood comparison calculated based on VD were reasonable while the error of uniform angle index was comparatively large. Therefore, when calculating the uniform angle index based on VD, other indicesrnwhich were used for spatial structure distribution evaluation were needed to confirm the result.