中文摘要：

结合塔里木河中下游74个植被样地和74眼地下水位监测井（2005-2007年）数据,将地下水位按不同埋深划分为0-2m,2-4m,4-6m,6-8m,8-10m和〉10m6个梯度,对不同地下水埋深下的群落盖度、物种多样性进行了分析,并探讨了主要植物种分布频率与地下水埋深的关系。结果表明：在地下水位2-4m时,物种多样性最高,其次为4-6m,再次为0-2m;当地下水位在6m以下时,物种多样性锐减。塔里木河中下游主要植物最适宜水位在2-4m之间;这些植物能够正常生长的地下水埋深区间为3-6m。这表明,塔里木河下游植被恢复的地下水位应确保达到6m以上。

英文摘要：

Based on the data collected from 74 vegetation plots and groundwater depth monitoring wells （2006 to 2007） in the middle and lower reaches of the Tarim River, the groundwater table was divided into six gradients （0-2, 2-4, 4-6, 6-8, 8-10 and 〉10 m） to compare the influence of groundwater level on coverage, plant diversity and plants appearance frequency. The results showed that plant diversity was the highest at the 2-4 m level, followed by 4-6 m and then 0-2 m. When the groundwater depth dropped to below 6 m species diversity decreased tremendously, and the slope of the Hill＇s index （diversity ordering） tended to level off. Thus, the optimum groundwater level for major plants growth is 2-4 m and the threshold groundwater depth is about 6 m. To restore vegetation and ecosystem of the lower reaches of the Tarim River, the groundwater depth must be kept at a minimum of 6 m.