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<p>Water use efficiency (WUE) represents the trade-off between carbon uptake and water consumption in terrestrial ecosystems. Utilizing eddy covariance, digital camera, and synchronous meteorological measurements at an underrepresented hyper-arid grassland, this study investigated the seasonal variations in WUE and evaluated its responsiveness to environmental and biological variables across different phenological periods. Additionally, we explored the response of WUE to drought events. Results showed that WUE exhibited opposite seasonal patterns compared to gross primary production (GPP) and evapotranspiration (ET), with peaks occurring during the senescence period. The annual mean WUE was 1.15 g C kg<sup>−1</sup> H<sub>2</sub>O. Seasonal variations of WUE were more controlled by the biophysical factors acting on ET than on GPP. Air temperature (<i>T</i><sub>a</sub>) and surface conductance (<i>g</i><sub>s</sub>) were the most important factors regulating WUE. Annually, WUE was markedly different between the dry and wet years, with values of 0.94 and 1.13 g C kg<sup>−1</sup> H<sub>2</sub>O, respectively. Seasonally, precipitation patterns exerted more pronounced effects on WUE than precipitation totals. Additionally, the seasonal processes of carbon and water coupling were highly related to vegetation phenology. Lastly, under varying moisture conditions, GPP and ET exhibited a significantly positive correlation, with decreasing slopes as soil water content increases, indicating heightened carbon–water coupling under drought stress. Under drought stress, both stomatal and non-stomatal factors governed WUE, with VPD directly regulating WUE or indirectly affecting g<sub>s</sub>. This study enhances our knowledge of ecohydrological processes and the coupled dynamics between carbon and water cycles in hyper-arid grassland ecosystems.</p>

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Water Use Efficiency of Grassland Ecosystem in Badain Jaran Desert and Its Relations to Biometeorological Variables

  • 期刊论文

  • 发表日期：

    2025年5月30日

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  • Nan Meng,
  • Nai’ang Wang,
  • Liqiang Zhao,
  • Xiaojun Liu,
  • Jinqiao Liu,
  • Sung-Ching Lee

摘要

Water use efficiency (WUE) represents the trade-off between carbon uptake and water consumption in terrestrial ecosystems. Utilizing eddy covariance, digital camera, and synchronous meteorological measurements at an underrepresented hyper-arid grassland, this study investigated the seasonal variations in WUE and evaluated its responsiveness to environmental and biological variables across different phenological periods. Additionally, we explored the response of WUE to drought events. Results showed that WUE exhibited opposite seasonal patterns compared to gross primary production (GPP) and evapotranspiration (ET), with peaks occurring during the senescence period. The annual mean WUE was 1.15 g C kg−1 H2O. Seasonal variations of WUE were more controlled by the biophysical factors acting on ET than on GPP. Air temperature (Ta) and surface conductance (gs) were the most important factors regulating WUE. Annually, WUE was markedly different between the dry and wet years, with values of 0.94 and 1.13 g C kg−1 H2O, respectively. Seasonally, precipitation patterns exerted more pronounced effects on WUE than precipitation totals. Additionally, the seasonal processes of carbon and water coupling were highly related to vegetation phenology. Lastly, under varying moisture conditions, GPP and ET exhibited a significantly positive correlation, with decreasing slopes as soil water content increases, indicating heightened carbon–water coupling under drought stress. Under drought stress, both stomatal and non-stomatal factors governed WUE, with VPD directly regulating WUE or indirectly affecting gs. This study enhances our knowledge of ecohydrological processes and the coupled dynamics between carbon and water cycles in hyper-arid grassland ecosystems.