Disentangling the Relative Drivers of Seasonal Evapotranspiration Across a Continental‐Scale Aridity Gradient
Disentangling the Relative Drivers of Seasonal Evapotranspiration Across a Continental‐Scale Aridity Gradient
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DOI：
10.1029/2022jg006916
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发表时间：
2022-07
期刊：
影响因子：
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通讯作者：
A. Young;M. Friedl;K. Novick;R. Scott;M. Moon;S. Frolking;Xiaolu Li;C. Carrillo;A. Richardson
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文献类型：
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作者：
A. Young;M. Friedl;K. Novick;R. Scott;M. Moon;S. Frolking;Xiaolu Li;C. Carrillo;A. Richardson
蒸散是一种重要的生态系统通量，控制着地表能量的分配。了解ET的季节性模式和幅度对于预测一系列生态系统影响至关重要，包括干旱，热浪事件和植物死亡率。在这项研究中，我们确定了相对控制ET的季节性变化，以及这些控制如何在生态系统之间变化。我们使用重叠的AmeriFlux和PhenoCam时间序列，每天从20个站点的时间步长来探索这些联系（# site‐years >100），我们的研究区域覆盖了美国和加拿大广泛的气候干旱梯度。我们专注于解开最重要的控制散装表面电导（Gs）和蒸发分数（EF = LE/[H + LE]），其中LE和H代表潜热和感热通量，分别。具体而言，我们调查了植被物候变化的重要性相对于气象变量（蒸汽压赤字和前期降水）的驱动程序的Gs和EF使用路径分析，一个框架，量化和比较多个响应和解释变量之间的因果关系。我们的研究结果表明，Gs和EF季节性的驱动因素在能量和水有限的生态系统之间存在显着差异。具体而言，降水在水有限的生态系统中具有更高的影响，而冠层绿色度的季节性模式在能量有限的生态系统中成为更强的控制因素。鉴于物候预计将在未来气候下发生变化，我们的研究结果为理解和预测物候如何影响21世纪世纪水文气候制度和地表能量平衡提供了关键信息。
Evapotranspiration (ET) is a significant ecosystem flux, governing the partitioning of energy at the land surface. Understanding the seasonal pattern and magnitude of ET is critical for anticipating a range of ecosystem impacts, including drought, heat‐wave events, and plant mortality. In this study, we identified the relative controls of seasonal variability in ET, and how these controls vary among ecosystems. We used overlapping AmeriFlux and PhenoCam time series at a daily timestep from 20 sites to explore these linkages (# site‐years >100), and our study area covered a broad climatological aridity gradient in the U.S. and Canada. We focused on disentangling the most important controls of bulk surface conductance (Gs) and evaporative fraction (EF = LE/[H + LE]), where LE and H represent latent and sensible heat fluxes, respectively. Specifically, we investigated how vegetation phenology varied in importance relative to meteorological variables (vapor pressure deficit and antecedent precipitation) as a driver of Gs and EF using path analysis, a framework for quantifying and comparing the causal linkages among multiple response and explanatory variables. Our results revealed that the drivers of Gs and EF seasonality varied significantly between energy‐ and water‐limited ecosystems. Specifically, precipitation had a much higher effect in water‐limited ecosystems, while seasonal patterns in canopy greenness emerged as a stronger control in energy‐limited ecosystems. Given that phenology is expected to shift under future climate, our findings provide key information for understanding and predicting how phenology may impact 21st‐century hydroclimate regimes and the surface‐energy balance.