Study on the Species Diversity during the Natural Succession of Degraded Karst Vegetation in Northwest Guizhou

By using spacial method in stead of temporal method,the species diversity in grass(G) stage,liana and thorny shrub(LS) stage,shrub and young tree(ST) stage,secondary forest(SF) stage and latter forest(LF) stage during the natural succession of degraded karst vegetation in Northwest Guizhou were studied.The species composition of different successional stages was analyzed,including richness,Simpson index,Shannon index and Pielou evenness of grass,shrub and tree layers.Richness of trees went up during the successional process,but richness for shrub layer and grass layer peaked at LS stage and then went down.For grass layer,Simpson and Shannon-Wiener index were the highest at LS stage and the lowest at LF stage,and Pielou index was the highest at G stage and then changed slowly to get the lowest point at LF stage.For shrub layer,the three indices took almost the same changing pattern,however Simpson and Shannon-Wiener index peaked at ST stage and Pielou index peaked at LS stage.For tree layer,all the three indices of SF stage was little higher than indices of LF stage,which may related to the disturbances and fuel harvesting at SF stage.