Divergent environmental responses of long-term variations in evapotranspiration over four grassland ecosystems in China based on eddy-covariance measurements
Divergent environmental responses of long-term variations in evapotranspiration over four grassland ecosystems in China based on eddy-covariance measurements
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DOI：
10.1016/j.jhydrol.2023.130030
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发表时间：
2023-10
影响因子：
6.4
通讯作者：
Han Zheng;Guirui Yu;Qiufeng Wang;Zhi Chen;Xianjin Zhu;Han Bao;Yuchen Sun;Panpan Niu;
中科院分区：
文献类型：
--
作者：
Han Zheng;Guirui Yu;Qiufeng Wang;Zhi Chen;Xianjin Zhu;Han Bao;Yuchen Sun;Panpan Niu;
了解草地蒸散量的长期变化规律是准确预测蒸散量对气候变化响应的关键。在这项研究中，我们分析了ET的年际变化（IAV）及其对环境条件的响应在4个草地生态系统在广泛的气候和生物群落条件的基础上的长期（9-11年）涡动协方差测量。这四种生态系统包括中国最普遍的草原植被，包括典型的温带草原，高山草甸草原，高山灌丛草甸，高山沼泽草甸。典型温带草原和高寒草甸草原年蒸散量的IAV主要受降水量（P）和相对湿度（RH）变化的影响。叶面积指数（LAI）是控制高寒灌丛草甸年蒸散量和生长季蒸散量IAV的主导因子，且LAI IAV与P变异显著相关。对于高寒沼泽草甸，净辐射是影响年蒸散量IAV的主导因子，水分供应条件（P和RH）对生长季蒸散量IAV的影响显著。类似的环境响应也被发现的IAV的平均表面电导（GS）在整个网站。具体而言，年度和生长季meangssignificantly增加，在高山灌丛草甸的LAI的增加，并出现在典型的温带草原和高山草甸草原的水分供应和VPD的变化更敏感。Priestley-Taylor系数（α =ET/ETeq，ETeq为平衡蒸发量）、解耦系数（Ω）和g的年和生长季IAV之间均存在显著的线性关系。此外，年平均值、Ω和α的变化进一步说明了高寒沼泽草甸的能量限制条件和其他3种草地的总体水分限制条件。本研究揭示了草地生态系统蒸散长期变化的不同环境响应，有助于对蒸散过程的全面认识和模拟工作。
Understanding the long-term variation in evapotranspiration (ET) for the spatially distributed grasslands is crucial for the accurate prediction of ET response to climate change. In this study, we analyzed the interannual variability (IAV) of ET and its responses to environmental conditions at four grassland ecosystems across a wide range of climatic and biome conditions based on the long-term (9–11 years) eddy-covariance measurements. The four ecosystems encompassed the most prevalent grassland vegetations in China, containing a typical temperate steppe, an alpine meadow-steppe, an alpine shrubland meadow, and an alpine marsh meadow. The IAVs of annual ET at the typical temperate steppe and the alpine meadow-steppe were primarily affected by either change in precipitation (P) or relative humidity (RH). Leaf area index (LAI) was the dominant factor controlling the IAVs of annual and growing-season ET at the alpine shrubland meadow, and the IAV of LAI was significantly correlated withPvariation. As to the alpine marsh meadow, net radiation turned to be the dominant factor for the IAV of annual ET, additionally with significant effects from water supply condition (Pand RH) on the IAV of growing-season ET. Similar environmental responses were also found for the IAVs of mean surface conductance (gs) across the sites. Specifically, annual and growing-season meangssignificantly increased with increases in LAI at the alpine shrubland meadow, and appeared to be more sensitive to changes in water availability and VPD at the typical temperate steppe and the alpine meadow-steppe. Significant linear relationships were also observed among the IAVs of mean Priestley-Taylor coefficient (α =ET/ETeq, where ETeqis the equilibrium evaporation), decoupling coefficient (Ω), andgson both the annual and growing-season basis in this study. Moreover, the variabilities of annual meangs,Ω, andαfurther demonstrated the energy-limited conditions at the alpine marsh meadow, and the overall water-limited conditions at the other three grasslands. This study reveals the divergent environmental responses of long-term ET variations over grassland ecosystems, and contributes to the comprehensive understanding on the ET process and modeling efforts as well.