基于空间结构指数的不同森林群落稳定性研究

以长白山杨桦次生林、云冷杉针阔混交林、云冷杉近原始林为研究对象,基于微观经济学中的柯布—道格拉斯生产函数相关理论,以3个常用的空间结构指标(混交度、大小比数、角尺度)为"投入",林分整体空间结构为"产出",构建林分空间结构生产函数,定义了林分空间结构指数(FSSI)并计算了林分空间结构距离(FSSD)。利用这5个指标分析比较不同演替阶段森林群落的空间结构特点,从而评价各演替阶段的稳定性。结果表明:不同演替阶段森林群落的混交度值均不相同,云冷杉近原始林平均混交度最大,云冷杉针阔混交林次之,杨桦次生林最小;大小比数对不同森林群落空间结构影响较小,其值基本为0.49~0.52;3种森林群落水平分布状态为云冷杉针阔混交林和云冷杉近原始林随机分布,杨桦次生林聚集分布;其空间结构指数大小及与理想结构接近程度排序为:云冷杉近原始林云冷杉针阔混交林杨桦次生林。因此,云冷杉近原始林空间结构较好,稳定性最佳。

Study on the Stability of Forest Communities Based on the Spatial Structure Index

This study was carried out in three forest communities (polar-birch secondary forest, spruce-fir mixed forest and spruce-fir near pristine forest). Based on the Cobb-Douglas production function theory in microeconomics, the production function of the spatial structure of the forests was constructed with three commonly used stand spatial structure indices (mingling degree, neighborhood comparison, and uniform angle index) as inputs and the forest spatial structure as output. The forest spatial structure index (FSSI) was defined and the forest spatial structure distance (FSSD) was calculated. To evaluate the stability of each successional stage, the 5 indices were analyzed and the spatial structure characteristics of the forest communities in different successional stages were compared. Results indicated that the mingling degree of forest communities in different successional stages was diverse. The average mingling degree was highest for the spruce-fir near pristine forest (0.81), followed by that of the spruce-fir mixed forest, and lastly that of the polar-birch secondary forest. Neighborhood comparison had little effect on the spatial structure of the forest communities in different successional stages, and values ranged from 0.49-0.52. Horizontal distribution of the three forest communities indicated random distribution for spruce-fir mixed forest and spruce-fir near pristine forest and aggregated distribution for polar-birch secondary forest. The spatial structure index size and degree of closeness to the ideal structure was in the order spruce-fir near pristine forest >spruce-fir mixed forest >polar-birch secondary forest. Thus, both the spatial structure and stability of the spruce-fir near pristine forest were the best.