广东黑石顶森林演替过程群落稳定性分析

Analysis of Community Stability at Various Successional Stages in Heishiding Nature Reserve, Guangdong Province

应用May的控制论模型,对广东黑石顶自然保护区森林演替系列5个不同演替阶段群落的稳定性进行了分析。每一群落设置一60m×60m的样地,并将其划分为36个10m×10m样方。理论模型中的3个参数按下列方法进行测定,①元素个数n:用群落中频度≥5 36的物种数表示;②元素间平均作用强度α:分别用种对间达到显著关联的联结系数AC和点相关系数PCC(P<0 05,AC=0,PCC=0)的绝对值之和除以种对总数表示;③关联度C:显著关联的种对数除以总的种对数。结果表明,群落演替各个阶段的不稳定指数α(nC)1 2,分别介于0.006～0 041(α用AC表示)或0.005～0.035(α用PCC表示)之间,都远小于1,说明黑石顶森林群落在各个演替阶段都是稳定的群落。

There are three parameters in May's Cybernetic system:①n, the number of elements in the interaction matrix;②α, the average interaction strength representing the average effect of each element on other elements. Its value is bounded from -1 to +1; ③C, the connectance representing the proportion of non_zero's in the matrix. Stability is defined by a matrix in which all real parts of the latent roots are negative. May showed that most of the systems are almost certainly stable if α(nC)^(1/2)<1, and unstable if α(nC)^(1/2)>1. An application of May's theory to a forest successional serires in Heishiding Nature Reserve, Guangdong Province, was presented. A 60 m×60 m sampling plot divided by 36 of 10 m×10 m quadrats were surveyed from each of 5 typical forest communities. Following May's analogy, the number of interaction elements was represented by the number of species S which frequency ≥5/36. The interaction strength among species with the association coefficient (AC) and point correlation coefficient (PCC) was measured. The sign of AC and PCC was changed to positive, and the mean value of significant AC's and PCC's (P<0.05 for AC=0 and PCC=0) was assigned as the average interaction strength. The proportions of all AC's or PCC's that were significantly different from zero were defined as C. The results showed that the ratio representing the instability index of the community at various successional stages was much less than 1. This implied that every forest community within the successional series is stable.