干旱区地下水湿生植物能够根据水分条件的变化来优化调整自身的根系分布，从而保证其充分利用稳定的地下水及深层土壤水。揭示地下水湿生植物根系的自优化机制及植物用水策略对水文条件变化的响应，是干旱区生态水文学研究的核心。本项目在综合考虑区域气候条件相似性及水文土壤条件差异性的基础上，选取黑河下游和塔河下游典型地下水湿生植物（胡杨、柽柳）林地为对象，对比分析不同土壤质地、地下水位埋深及水位变化速率下的植被蒸散过程及相应的植被根系、地下水与土壤水动态，分析植被根系对不同土壤质地和地下水位变化的响应，发展基于“自优化调节机制”的植物根系随土壤水与地下水变化的动态模型，从年、季和日尺度上揭示干旱区地下水湿生植物的用水策略及其对水文条件变化的自调节行为。研究成果有助于深化干旱区地下水依赖型生态系统对地下水位变化响应与反馈机制的认识，为我国西北干旱区生态水资源的科学配置提供科学理论依据。

Phreatophytes in arid regions are able to adjust their root distributions to ensure direct root water uptake from the groundwater and deep soil water. Understanding the plant root optimality of phreatophytes and the response of water use strategy on the varying hydrological conditions is the key issue of the eco-hydrology in arid regions. Considering the similarity in climate conditions and differences in soil and hydrological conditions, the current project aims to select the typical Populus euphratica and Tamarix ramosissima sites at the lower Heihe and Tarim rives. It is planning to analyze the plant transpiration and associated dynamics in plant root systems, the groundwater level and soil moisture under the different soil, depth to water table and changes in water table. The response of root dynamics to soil properties and changes in water table will be further quantified. The dynamic root model that considers the changes in root distribution with soil moisture and water table dynamics will be developed with the principle of self-optimality. It will reveal the diurnal, seasonal and annual water use strategy of phreatophytes and also its self-regulation with the changeable hydrological conditions. The results will help us to deep understand the response and feedback between groundwater-dependent ecosystem with changes in groundwater table, and also will provide an important insight of water regulations that aim to protect the ecological environment in arid regions.