Water use efficiency and evapotranspiration partitioning for three typical ecosystems in the Heihe River Basin, northwestern China
Water use efficiency and evapotranspiration partitioning for three typical ecosystems in the Heihe River Basin, northwestern China
复制标题
DOI：
10.1016/j.agrformet.2018.02.002
复制
发表时间：
2018-05
影响因子：
6.2
通讯作者：
Sha Zhou;Bofu Yu;Yao Zhang;Yuefei Huang;Guangqian Wang
中科院分区：
文献类型：
--
作者：
Sha Zhou;Bofu Yu;Yao Zhang;Yuefei Huang;Guangqian Wang
提高水分利用效率(WUE)和蒸散系数(T/ET)是干旱地区节水的关键。水分利用效率作为联系碳和水循环的纽带，被定义为生态系统尺度上的总初级生产力(GPP)与蒸散量的比率。通过考虑水汽压差对WUE的影响，最近提出了两个潜在的WUE公式，即潜在的UWUE(uWUEp = GPP·VPD0.5/T)和表观UWUE(uWUEa = GPP·VPD0.5/ET)。UWUEp和uWUEa都可以从涡旋协方差测量中估计出来，然后利用uWUEa和uWUEp的比值来估计T/ET。将该划分方法应用于黑河流域3个典型生态系统。由于地膜覆盖，大曼地的生长季T/ET(0.63)高于阿柔地和呼阳林地(0.55)。叶面积指数(LAI)对AROU(R2= 0.74)和大曼(R2= 0.76)站点的T/ET季节变化的影响较大，而对呼阳林(R2= 0.44)站点的影响较小。利用uWUE方法和同位素、蒸渗仪/涡动协方差方法计算的达曼站点生长旺季的逐日T/ET值基本一致。利用uWUE方法估算的T值与用树干流量法估算的T值具有一致的季节、日变化规律和大小。此外，uWUE方法可以在不存在尺度问题的情况下估计生态系统的T/ET，并且可以有效地捕捉与LAI变化相关的T/ET变化以及T/ET随单个灌溉事件的突变。这些优点使得uWUE方法在生态系统尺度上有效地进行了ET分配，并可通过预测实际植物需水量的季节格局来用于水资源管理，以支持干旱地区的灌溉策略。
It is crucial to improve water use efficiency (WUE) and the transpiration fraction of evapotranspiration (T/ET) for water conservation in arid regions. As a link between carbon and water cycling, WUE is defined as the ratio of gross primary productivity (GPP) and ET at the ecosystem scale. By incorporating the effect of vapor pressure deficit (VPD) on WUE, two underlying WUE (uWUE) formulations, i.e. a potential uWUE (uWUEp = GPP·VPD0.5/T) and an apparent uWUE (uWUEa = GPP·VPD0.5/ET), were proposed recently. Both uWUEp and uWUEa can be estimated from eddy covariance measurements, and the ratio of uWUEa and uWUEp was then used to estimate T/ET. This new method for ET partitioning was applied to three typical ecosystems in the Heihe River Basin. Growing season T/ET at the Daman site (0.63) was higher than that at the Arou and Huyanglin sites (0.55) due to the application of plastic film mulching. The effect of leaf area index (LAI) on seasonal variations in T/ET was strong for Arou (R2= 0.74) and Daman (R2= 0.76) sites, but weak for Huyanglin (R2= 0.44) site. Daily T/ET derived using the uWUE method agreed with that using the isotope and lysimeter/eddy covariance methods during the peak growth season at the Daman site. The estimated T using the uWUE method showed consistent seasonal and diurnal patterns and magnitudes with that using the sap flow method at the Huyanglin site. In addition, the uWUE method can estimate ecosystem T/ET without scaling issues, and can effectively capture T/ET variations in relation to LAI changes and the abrupt T/ET changes in response to individual irrigation events. These advantages make the uWUE method effective for ET partitioning at the ecosystem scale, and can be used for water resources management by predicting seasonal pattern of actual plant water requirements to support irrigation strategies in arid regions.