针对异质性地表条件下蒸散发过程的重要性和复杂性，选择干旱区典型灌丛生态系统为研究对象，综合应用涡度相关技术、树干液流技术和稳定同位素技术，通过长期野外定位监测和室内模拟试验，系统研究（1） 土壤从饱和到极干情况下，毛管流、薄膜流和水汽扩散运动发生的含水量阈值，揭示不同土壤水分运动形式对干旱区土壤蒸发的贡献；（2）干旱灌丛生态系统根系吸水特征，揭示其水分利用来源及对土壤水分分布的影响；（3）异质性地表总蒸散发及其组分的动态特征及其与环境因子的关系；在此基础上，建立基于SPAC理论的干旱灌丛生态系统的蒸散发模型，并以贝叶斯定理为框架实现融合多源数据的模型参数同步估计，提高模型预测结果的一致性。其预期成果将在理论上丰富和发展干旱区植物生理学、水文学及全球变化科学的理论和方法；在实践上，为干旱区制定气候变化应对策略和有效水资源管理提供基础数据和理论支撑。

By comprehensively applying the long-term in situ observing methods which include the eddy covariance technique, sap flow techniques and isotope technique and laboratory simulation, this project aimed to reveal the biological and physical controlling mechanisms of evapotranspiration over typical shrub ecosystem in arid northwest China. Here, we will systemically study: (1) the threshold values of soil water content under which the movement was determined by capillary flow, film flow and vapor diffuse, to reveal the contribution of different soil water movements to total ET; (2) the characteristics of root water uptake to reveal the water usage sources and its influence on soil water distribution; (3) the dynamic characteristics of the total ET and its components as well as their relationship with environmental factors. Based on these researches, we will develop an ET model based on the SPAC theory, and simultaneously estimate the model parameters by assimilating multi-datasets using the Bayes’ theory. It is excepted that this study will enrich and develop the contents of arid-region physiological plant ecology, hydrology and global change science in theory and practice, and will provide the theoretical supports for the drawing adaptive strategies to climate change and reasonable managements of water resources in arid regions.