Species Diversity and Dominance Population Distribution Pattern in Oasis-Desert Ecotone

Synthesis dominance rate(SDR),Richness index(R),Shannon-Wiener index(H),Simpson index(D),Pielou index(JSW),Whittaker index(βwc),Cody index(βc),Dispersion index(C),Negative binomial parameter(K),Mean crowding intensity(m*),Clumping index(I),Patchiness index(PI),Cassie index(GI) and Green index(CA) are used to analyze the species diversity and dominance population distribution pattern based on field surveying data from 30 plots along 10 sections at oasis-desert ecotone in the lower reaches of the Tarim River.The results showed that the structure and composition of these communities were simple,the dominance populations were Populus euphratica,Tamarix chinensis Lour.,Lycium ruthenicum,Halostachys caspic,Karelinia caspica,Phragmites communis,Alhagi sparsifolia,Glycyrrhiza inflate,Poacynum hendersonii,and they distributed in aggregative state in responding to groundwater depth.The α-diversity indices of these communities were low,and species diversity showed gradient change.The richness index followed the order: oasisecotonedesert due to water resource difference in microenvironment.From ecotone to desert,the community structure changed from tree-shrub-herbage to shrub-herbage to single shrub to shrub-herbage,and to tree-shrub-herbage due to change of groundwater depth.Suggested by Whittaker index and Cody index,the β-diversity indices of these communities changed with groundwater depth gradient,showing the ecotone was the boundary between oasis species and desert species distribution.Therefore,the groundwater depth was the decision factor for species diversity and distribution pattern of dominance population at oasis-desert ecotone in the lower reaches of the Tarim River.