中文摘要：

杜加依林建群种胡杨（Populus euphratica）的水分再分配现象已被广泛认知,但该现象对其伴生种多样性和生态位宽度的影响仍不清楚。基于120个样方的调查数据,通过分析比较2010年6、8、10月胡杨林冠下（林冠群落）与非胡杨林下（对照群落）在群落数量特征、物种多样性和生态位宽度上的差别,以探明水分再分配和物种多样性间的关系。结果表明：（1）林冠灌木和草本群落的郁闭度、株高和多度在6、8、10月均分别显著高于对照灌木和草本群落（P〈0.05）;（2）在6、8、10月,林冠灌木的Margalef丰富度指数和Brillouin物种多样性指数均显著高于对照群落（P〈0.05）,Pielou均匀度指数在两群落间未有显著性差别（P〉0.05）;相反,林冠草本群落的Margalef丰富度指数仅在6月和10月显著高于对照群落（P〈0.05）,其他时期,林冠草本群落的物种多样性指数均小于对照群落;（3）林冠灌木和草本群落的物种生态位宽度多高于对照灌木和草本群落。胡杨作为杜加依林的建群种,其拥有水分再分配现象能够改善森林的水分条件,对胡杨林冠下伴生种群落的数量特征、生态位宽度和物种多样性产生积极影响。

英文摘要：

Relationship between plant and water in arid environment is a hotspot in physiology and ecology research,but the connections between hydraulic redistribution（HR）and species diversity is still undiscovered.In this study,Based on the survey data of 120 quadrats in June,August and October 2010,the community under the P.euphratica canopy（Under community：UC）and the community outside the P.euphratica canopy（Control community：CC）were used to test the differences of community numerical characteristics,niche breadth and community diversity between UC and CC.The results showed that,（1）canopy density,abundance and community depth in herb and shrub UC（HUC and SUC）were significantly higher than these in herb and shrub CC（HCC and SCC）from June to October（P0.05）;（2）Margalef richness and Brillouin diversity index in SUC were significantly higher than these in SCC（P0.05）across growing season,but there was no significant difference between SCC and SUC for Pielou evenness index（P0.05）.On the contrary,Margalef richness index in HUC only was significantly higher than these in HCC in June and October（P0.05）,but at other all times,Margalef richness,Brillouin diversity and Pielou evenness index were higher in HCC;（3）niche breadth in SUC and HUC were larger than these in SCC and HCC across growing season.In conclusion,P.euphratica HR significantly ameliorates the water conditions of shallow soil,which then influences the community numerical characteristics,niche breadth and community diversity.