Response of Species Diversity in Natural Abies faxoniana Forest Along an Elevation Gradient in Wolong Nature Reserve, Sichuan Province

Using the typical transect survey method, five sample zones along an elevation gradient were set up in the Abies faxoniana natural forest on the dengsheng shady slope of Wolong nature reserve to analyze the response law of the species biodiversity of Abies faxoniana natural forest with altitude gradients. The results showed that the species richness, Shannon-Wiener diversity index, Pielou evenness index and integrated diversity index of natural Abies faxoniana forest in the tree layer and herb layer showed a decreasing trend with elevation gradient, while the ecological dominance index showed an increasing trend. The species richness of shrub species decreased with the elevation gradient, while the Shannon-Wiener diversity index, Pielou evenness index and integrated diversity index decreased first and then increased, and the variation of ecological dominance index was opposite. Variations of α-diversity of all plants in the community with elevation were consistent with that of the tree layer. In terms of β-diversity, the dissimilarity coefficient CD and Cody index of trees, herbs and all plants in all communities in Abies faxoniana forest showed a downward trend with the rising elevation. However, due to the change of species number and dominant species, the shrub layer formed a bimodal change of β-diversity, which was consistent with the actual distribution of shrub species. The species difference and turnover rate of the Abies faxoniana community were greatly influenced by the vegetation types with more species, and gradually decreased with the elevation.