The diversity characteristics on secondary vegetation of different restoration stages in Hanquangou valley of Tianzhu county

The two-way indicator species analysis and the detrended correspondence analysis are adopted to classify and rank the quadrats of the secondary plant in the Hanquangou valley in Gansu province.The flora can be divided into different community types,and demonstrate the distributed pattern of the vegetation community in this region.Based on this result,the species richness index,the Simpson dominance index,the Shannon-Wiener diversity index and the Pielou evenness index are used to study the species diversity of different vegetation community types.The results shows that there are 7 community types,which represents the different restoration stages.The primary limiting factors are water and heat in specific region,Chashugou valley.From restora-tion stage Ⅰt oⅦ,as for the Simpson dominance index,tree layer,shrub layer and herb layer are approximately equal,the Shan-non-Wiener diversity index manifests as tree layer shrub layer herb layer,the Pielou evenness index manifests as tree layer herb layer shrub layer,and the species richness increase gradually.The species composition and the spatial structure of the community become complication gradually,and tend to be stable.