Plant response to soil and atmospheric water stresses is the dominant control of Dryland ecosystem functions, affecting water resources, ecosystem stability and biodiversity. The link between water stresses and plant water status is regulated by plant hydraulics, of which the corresponding impact on plant water use and the susceptibility of Dryland ecosystems remains under-explored. We used a plant hydraulic model to describe hydraulic states and water flux of two species (Populus euphratica and Tamarix ramosissima) in desert riparian ecosystems. We optimized hydraulic parameters and tested the model using observed physiological states and ecosystem water flux. The optimized model was used to evaluate plant hydraulic sensitivity, tree mortality risk, and evapotranspiration under a wide range of water stress scenarios. The model captures the observed leaf water potential, sap-flow and ecosystem evapotranspiration. Our scenario analysis demonstrates that hydraulic sensitivities generally reduce as the water stresses intensify. The results highlight a strong coupled impact of the co-occurrence of soil and atmospheric water stresses on restricting ecosystem water flux and intensifying mortality risk. The assessment of multiple aspects of eco-physiological functions and the stress scenario analysis of desert riparian ecosystems will contribute to a better prediction of ecosystem functions and facilitate resource management under future climate.

植物对土壤和大气水分胁迫的响应是旱地生态系统功能的主导控制，影响水资源、生态系统稳定性和生物多样性。水分胁迫与植物水分状况之间的联系受植物水力学调节，其中对植物水分利用和旱地生态系统敏感性的相应影响仍未得到充分探索。我们使用植物水力模型来描述两种植物（胡杨和柽柳）的水力状态和水通量) 在沙漠河岸生态系统中。我们优化了水力参数并使用观察到的生理状态和生态系统水通量来测试模型。优化后的模型用于评估各种水分胁迫情景下的植物水力敏感性、树木死亡风险和蒸散量。该模型捕获了观察到的叶水势、树液流和生态系统蒸散量。我们的情景分析表明，随着水压力的加剧，水力敏感性通常会降低。结果强调了土壤和大气水分胁迫同时发生对限制生态系统水通量和加剧死亡风险的强烈耦合影响。