| In order to understand the forest community status, structural feature, to provide technical guides for vegetation recovery and biodiversity conservation in the central hilly areas of Sichuan Province, the structural feature in each community layers was analyzed, and the community stability was studied through M. Godron index and fuzzy function in the paper.(1)In terms of layer, the forest communities can be divided into arbor, shrub and grass layers, the forest layers are simple. There are 7 families,7 genera,11 species in arbor layers; 29 families,39 genera,60 species in shrub layer; 35 families,57 genera, 72 species in grass layer. Each forest type has own main family, especially in shrub and grass layer. Rosaceae, Verbenaceae and Graminea are the main families.(2) Each forest type has its own dominant or sub-dominant species, but they are quite variable. In artificial forests, the pure community consisting of one species is quite common in both shrub and grass layer; however, this situation never occur in natural forests.(3) In terms of species distribution, the species in community, shrub and grass conform to the frequency distribution law, and belongs to L shape. That is, A class of low frequency are actually dominant; but species frequency varies to forest layers.(4) Shannon-Wiener index, richness index and ecological dominance index are higher in shrub and grass layers than that of arbor layers. Highly significant difference exists in arbor-shrub layer, and arbor-grass layer. Evenness index in each forest layer shows no distinct law.(5) Diversity index varies with community types.1)communityâ…§(natural secondary oak-cypress community) has the highest Shannon-Wiener index (0.6854), then communityâ…£(0.5984) and communityâ…¤(0.5557), communityâ…¢(pure cypress forest) is the lowest one (0.2121).2) Pielou evenness index ranks as:communityâ…§(0.9615)>communityâ…¦(0.8691)> communityâ…¤(0.7464)> communityâ…£(0.7197)> communityâ…¥(0.6943)>communityâ… (0.3326)> communityâ…¡(0.3168)> communityâ…¢(0.3115).3)The order of species richness index is:communityâ…§(7.2)> communityâ…£(6.8)> communityâ…¤(6.1)>communityâ…¦(5.4)> communityâ… (4.7)> communityâ…¡(3.5)> communityâ…¥(2.9)> communityâ…¢(1.9).4) In terms of ecological dominance index, communityâ…§is the highest one (0.7444), communityâ…£is the second (0.7020), communityâ…¤ranks the third (0.6622), communityâ… is the lowest one (0.2196).(6) Study on the community stability though M.Godron index has indicated that the intersection point's coordinates (ratio of species percentage and accumulative relative frequency to straight-line equation y=-x+100) is (37/63), (39/61), (39/61), (38/62),(36/64), (40/60), (37/63), (39/61)respectively from communityâ… to communityâ…§. Far from the stable intersection point (20/80), which means all the communities are still in the unstable stage.(7) By choosing vegetation feature, community diversity index, soil physical properties, soil nutrient feature and M. Godron index, the stability of the forest communities was evaluated through subordinate function, the results has shown that the function value ranks as:communityâ…§(0.7039)> communityâ…¡(0.5395)> communityâ…¢(0.5200)> communityâ…¦(0.5176)> communityâ…¥(0.5026)> communityâ…£(0.4683)> communityâ… (0.3884)> communityâ…¤(0.3445).
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