中文摘要：

通过对塔里木河下游不同地下水埋深梯度下胡杨和柽柳叶片δ13Ｃ值的测定，分析了地下水埋深变化对胡杨和柽柳的长期水分利用效率的影响，为塔里木河下游退化生态系统植被保育和恢复提供科学依据。研究结果表明，随着地下水埋深从２．４ｍ增加到９．１ｍ，胡杨叶片δ13Ｃ值呈现出先升后降的趋势，且在９．１ｍ 处胡杨很可能是通过减少地上生物量的方式来适应加剧的干旱；而柽柳叶片δ13Ｃ值则随着地下水埋深的增加而逐渐增加，其水分利用效率不断增加，且对地下水埋深变化的适应宽度也较大。对比同一地下水埋深下胡杨和柽柳叶片的δ13Ｃ值发现，随着地下水埋深不断增加，胡杨的抗旱性比柽柳的弱；对比不同地下水埋深的植物叶片的δ13Ｃ 值发现，胡杨在不同的地下水埋深采取不同的策略适应干旱环境，而柽柳在不同的地下水埋深则通过增加水分利用效率来抵御加剧的干旱。

英文摘要：

The δ13C values of Populus euphratica and Tamari spp. in the lower reaches of the Tarim River were measured under different groundwater depth gradients and the effect of groundwater depth diversification on long-term water use efficiency was analyzed. This research provides a scientific basis for degraded ecosystem vegetation conservation and restoration in the lower reaches of the Tarim River. The δ13C value in P. euphrati ca leaves initially increased but then decreased as the groundwater depth varied from 2.4 to 9.1 m. P. euph ratica was likely to reduce aboveground biomass to adapt to the intensified drought at 9.1 m. The δ13C values in Tamariac spp. leaves gradually increased with increasing groundwater depth, indicating that water use effi ciency and the width of the adapted groundwater depth increased as the groundwater depth become deeper. The δ13C values of P. euphratica and Tamarix spp groundwater depth and It was found that drought leaves were compared under the conditions of the same resistance of P. euphratica was weaker than that of T chinensis with increasing groundwater depth. Under conditions of different groundwater depths, the δ13C val ues of P. euphratica and Tamaria spp. leaves were compared. P. euphratica used different strategies at dif ferent groundwater depths to adapt to arid environments, while Tamarix spp. resisted the intensified drought by increasing water use efficiency.