中文摘要：

荒芜的河边的植物由于水文学变化在水可获得性经历高可变性。然而，河边的植物怎么能与低水可获得性幸存，几乎很好没被学习在植物社区组织上对高水位线可获得性的效果被知道。我们进行了一个 mesocosm 实验测试在模仿的高地下水可获得性下面的幼苗竞争是否能向 P 在早社区解释 Populus euphratica 和 Tamarix ramosissima 的合作优势的移动。在沿着西北的中国的 Tarim 河的成熟的 euphratica 优势。这二植物种的幼苗与高地下水可获得性在单一经营和混合水池被种。结果显示未葬生物资源和亲戚 T 让步。ramosissima 比 P 的那些高。euphratica。T 的竞争优势。ramosissima 在生长包括了它的快速的反应到地下水丰富和它的水 spender 策略，由到 leaf-to-air 蒸汽压力赤字的增加的叶生物资源比例和惰性的有气孔的反应证实了 VPD ) 。在比较， P。euphratica 在水使用显示出保守策略，与对 leaf-to-air VPD 的敏感回答。短期的比赛的结果与地里的长期的比赛不一致，建议比赛排除不是组织荒芜的河边的植物社区的机制。因此，我们的研究由环境变化强调调停的重要性(例如减少，竞争由骚乱导致了) 在沿着 Tarim 河边的地区组织植物社区。

英文摘要：

Desert riparian plants experience high variability in water availability due to hydrological fluctuations. How riparian plants can survive with low water availability has been well studied, however, little is known about the effects of high water availability on plant community structuring. We conducted a mesocosm experiment to test whether seedling competition under simulated high groundwater availability can explain the shift of co-dominance of Populus euphratica and Tamarix ramosissima in early communities to P. euphratica dominance in mature ones along the Tarim River in northwestern China. Seedlings of these two plant species were grown in monoculture and mixture pools with high groundwater availability. Results indicated that the above-ground biomass and relative yield of T. ramosissima were higher than those of P. euphratica. The competitive advantages of T. ramosissima included its rapid response in growth to groundwater enrichment and its water spender strategy, as evidenced by the increased leaf biomass proportion and the inert stomatal response to leaf-to-air vapor pressure deficit （VPD）. In comparison, P. euphratica showed a conservative strategy in water use, with a sensitive response to leaf-to-air VPD. Result of the short-term competition was inconsistent with the long-term competition in fields, suggesting that competition exclusion is not the mechanism structuring the desert riparian plant communities. Thus, our research highlights the importance of mediation by environmental fluctuations （such as lessening competition induced by disturbance） in structuring plant communities along the Tarim riparian zones.