Effects of Forest Gap Disturbance on Plant Species Diversity and Stability in Regeneration Layers of Castanopsis kawakamii Natural Forests

The effect of forest gap disturbance on the diversity and stability of species in the regeneration layers of natural Castanopsis kawakamii forest were studied by applying biodiversity indices and improved M.Godron's stability methods in C.kawakamii natural reserve.The results showed that: forest gap disturbance improved its micro-environment,as reflected in the differences in importance values and biodiversity in the tree and shrub layers of forest gap and understory.The biodiversity indices of richness index R,domination index D,Shannon-Wiener diversity index H,and evenness-dominance-abundance index Z in the forest gap tree layer were higher than those of the forest understory,while evenness index Js and community dominance C were lower than those of the forest understory.The biodiversity indices of R,D,H,J s,and Z in the forest gap shrub layer were higher than those of the forest understory,while C were lower than those of forest understory.Biodiversity in the forest gap was richer with less evident ecological dominant species,which indicated that the population in the forest gap was developing in the direction of complexity and homogeneity.The similarity coefficients of C j,C s,and C N were relatively low,while C mH was relatively high in the tree layer of the forest gap and understory,which demonstrated that the forest gap promoted the regeneration of trees.The similarity coefficients of C j,C s,C N,and C mH were relatively high without exception and the species composition in the forest gap were basically identical with those of the understory.According to the theory of M.Godron and the simulated the optimum stability model,the logarithm model and quadratic objective function model were the best stability models in tree layer of the forest gap and understory,respectively,and the optimum stability model of the shrub layer in both the forest gap and understory was the logarithm model.The plants in the tree layer of the forest gap were stable,but were unstable in the understory.The plants in the shrub layer of both the forest gap and understory were stable.The importance value of Litsea subcoriacea was the highest in the tree layer of the forest gap and understory,which showed that it played an important role in forest regeneration and would likely have a greater impact on the regeneration of C.kawakamii population.The importance value of C.kawakamii was relatively low in the tree layer of the forest understory,which impacted its regeneration.However,forest gap disturbance improved the upward growth and importance value of C.kawakamii,which could achieve the regeneration and restoration of the C.kawakamii population effectively.