揭示半干旱流域水-能量平衡和下垫面条件对水分利用效率敏感性和非线性响应的规律。
Unraveling the sensitivity and nonlinear response of water use efficiency to the water-energy balance and underlying surface condition in a semiarid basin.
机构信息
Beijing Key Laboratory of Urban Hydrological Cycle and Sponge City Technology, College of Water Sciences, Beijing Normal University, Xinjiekouwai Street 19, Beijing 100875, China.
Beijing Key Laboratory of Urban Hydrological Cycle and Sponge City Technology, College of Water Sciences, Beijing Normal University, Xinjiekouwai Street 19, Beijing 100875, China.
出版信息
Sci Total Environ. 2020 Jan 10;699:134405. doi: 10.1016/j.scitotenv.2019.134405. Epub 2019 Sep 11.
Ecological water use efficiency (WUE) is a crucial indicator of hydrological and vegetation carbon cycle coupling and can drastically affect water and energy exchanges. However, little is known about the sensitivity of WUE to water-energy exchange in semiarid regions. Moreover, few studies have considered the link between WUE and water-energy exchange models, i.e., the Budyko-type framework. Here, we investigated the relationships between WUE and a Budyko-type model in a semiarid basin. Seven primary indicators were selected to represent the water, energy, and vegetation variations in the ecosystem: gross primary productivity (GPP), air temperature (T), potential evapotranspiration (PET), evapotranspiration (ET), precipitation (P), soil water content (SWC), and snow water equivalent (SWE). Three similar ecological WUEs were defined as GPP/ET, GPP/P, and GPP/SWC to analyze the factors of the water-energy exchange model (i.e., ET/P, PET/P, SWC/P, and SWE/P). Based on the results, four linear Budyko-type models were proposed for the basin (GPP/P, ET/P, SWC/P, and SWE/P as a function of PET/P). The results suggested that both SWC and P influenced the trend of GPP variation, whereas P influenced the lower limit of GPP or GPP/P within the Budyko model for grassland areas. The results indicated that the rate of increase of SWC was lower than that of P in forest areas because of differences in canopy structure. The results also revealed a nonlinear (s-type) relationship between the WUEs and the underlying surface parameter m within the Budyko framework, suggesting that unit plant productivity consumes less water when the water-energy supply condition is invariant, if the variation of the underlying surface characteristics promotes the increase of m. Our research provides new insight regarding quantification of the sensitivity of WUE to the water-energy balance in a semiarid region.
生态用水效率（WUE）是水文和植被碳循环耦合的关键指标，对水热交换有显著影响。然而，对于半干旱地区 WUE 对水热交换的敏感性，人们知之甚少。此外，很少有研究将 WUE 与水热交换模型（如 Budyko 框架）联系起来。在这里，我们研究了半干旱流域 WUE 与 Budyko 型模型之间的关系。选择了七个主要指标来代表生态系统中的水、能量和植被变化：总初级生产力（GPP）、空气温度（T）、潜在蒸散（PET）、蒸散（ET）、降水（P）、土壤含水量（SWC）和雪水当量（SWE）。定义了三种相似的生态 WUE，即 GPP/ET、GPP/P 和 GPP/SWC，以分析水热交换模型的因素（即 ET/P、PET/P、SWC/P 和 SWE/P）。基于结果，提出了四种适用于该流域的线性 Budyko 型模型（GPP/P、ET/P、SWC/P 和 SWE/P 作为 PET/P 的函数）。结果表明，SWC 和 P 均影响 GPP 变化趋势，而 P 则影响草原区 Budyko 模型中 GPP 的下限或 GPP/P。结果表明，由于冠层结构的差异，森林区 SWC 的增长率低于 P。结果还揭示了 Budyko 框架内 WUE 与基础表面参数 m 之间的非线性（s 型）关系，表明在水热供应条件不变的情况下，单位植物生产力消耗的水量较少，如果基础表面特征的变化促进 m 的增加。本研究为量化半干旱地区 WUE 对水热平衡的敏感性提供了新的见解。
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