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When and where does storage matter for plants: the effect of root zone water storage capacity on evapotranspiration
  • Christopher J Heckman,
  • Christina Tague,
  • Kelly Caylor
Christopher J Heckman
Wake Forest College

Corresponding Author:[email protected]

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Christina Tague
University of California, Santa Barbara
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Kelly Caylor
University of California, Santa Barbara
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Abstract

Root zone water storage capacity (SR) plays a fundamental role in determining the magnitude of evapotranspiration (ET) during both average and extreme climatic conditions. While methods exist to estimate SR globally at relatively fine spatial scales, the effects of uncertainty in these broad-scale estimates on evapotranspiration are largely unknown. We present a new method to efficiently describe the relationships between SR and evapotranspiration across all possible values of SR, for a given climate. This approach replaces computationally expensive model sensitivity analyses and provides a means for characterizing the importance of uncertainty and spatial variability in SR across various climates and timescales. To demonstrate the utility of our framework, we apply our approach to nine sites across the United States that vary in their seasonal climatology. In doing so, we show that evapotranspiration can be dramatically different between sites even with the same SR. For example, a very shallow SR (15 mm) would limit evapotranspiration to 27% of its maximum value (given no storage limitation) in some sites but to only 68% in others. Furthermore, if SR was estimated to be 250 mm with an uncertainty of +- 20%, the effect on estimated evapotranspiration in Eel (a site in Northern California) would be significant (+- 10%) but negligible in Boulder (a site in the Colorado Rockies). Furthermore, we find distinct site-specific SR–ET relationships that substantially impact how uncertainty and spatial variability in landscape distributions of SRaffect evapotranspiration patterns.
31 Oct 2024Submitted to ESS Open Archive
01 Nov 2024Published in ESS Open Archive