Study Of Populus Euphratica Community Pattern In The Upper, Middle And Lower Reaches Of Tarim River

The study focused on ecological survey of Populus euphratica community in the upper, middle and lower reaches of Tarim River. The objective of this study was to illuminate the population structure and quantitative dynamic, living status and development trend in the future. The results of this study were as follows:(1) Community composition structure and species diversity: The community structure was simple, the arbor, shrub and herbage were distinctly delaminated into three. Twenty species were identified in the whole study area, with thirteen in upper reaches, seventeen in middle reaches and six in lower reaches. The species quantity, indivedual density, species diversity of P. euphratica community in the upper and middle reaches were higher than lower reaches of Tarim River. The species quantity ,indivedual density, species diversity of P. euphratica community in the middle reaches of Tarim River are the highest.(2) The sturcture and dynamic of P. euphratica population: Height classes curve, static life table and survival curve of DBH and failure rate of height classes entirely indicated that a increasing from upper to middle reaches, while a decline community to lower reaches.The ratio of unstead of P. euphratica population in the upper reaches was 37.05%, while it was 52.91% in the middle reaches,and 23.95% in the lower reaches, indicating that P. euphratica population in the upper and middle reaches had higher growth rate, but it showed decline status in the lower reaches.(3) P. euphratica distribution pattern: In the upper reaches, low DBH (seedlings) of P. euphratica showed cluster distribution, especially in alongshore zone, while high DBH ( middle-aged and adult tree)of P. euphratica appeared random and uniform distribution. In the middle reaches, the P. euphratica showed cluster distribution mainly. And in the lower reaches, seedlings showed cluster distribution, while middle-aged and adult tree displayed random and uniform distribution.Summing up, what conclusions can be drawn was that: The environmental condition for P. euphratica community survive was the best, and the healthy development of P. euphratica community in the upper reaches of Tarim River. The environmental condition for P. euphratica community survive was better in the middle reaches of Tarim River, and showed strongly growth trendy, but the growth trendy was susceptible to interference from environmental factors, especially water. P. euphratica community are highly dependent on water, and Tarim River set-off in the lower reaches was one of the main reason of recession of P. euphratica community.