Abstract: To investigate the effect of the water disturbance on community diversity of Populus euphratica in the middle and lower reaches of the Tarim River, Xinjiang, China, by using the diversity index and community similarity index, this paper studied the community diversity of Populus euphratica before and after the ecological water conveyance in the middle and lower reaches of the Tarim River. The results show as follows:(1) the Populus euphratica communities within the study area include a total of 14 families, 27 genera and 27 species, giving priority to those with resistant to cold, drought and salt;(2) the diversity of community shows that, Patrick richness index, Simpson diversity index and Pielou evenness index have different changing trends, and Pielou evenness index is contrast with McIntosh diversity index and Patrick rich index; the same kind of diversity indices are significantly different before and after the ecological water conveyance from midstream to downstream of Tarim River, so the main factor affecting the community diversity of Populus euphratica is water disturbance;(3) the community similarity comparison shows that, the similarity of Populus euphratica community before ecological water conveyance, from high to low, ranks as:the critical point of the middle and lower reaches, the downstream community, and the upstream community; while the similarity of Populus euphratica community after ecological water conveyance ranks inversely. So water is the main factor affecting the similarity of community. The results of community similarity comparison and community diversity analysis are basically consistent, the water factor is the dominant factor of the Tarim River Populus euphratica communities. The water disturbance is the dominant factor affecting the species, diversity, and similarity of Populus euphratica communities in the middle and lower reaches of Tarim River.

Key words: Populus euphratica, ecological water conveyance, diversity, similarity