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Research article - Peer-reviewed, 2012

EVAPOTRANSPIRATION: A PROCESS DRIVING MASS TRANSPORT AND ENERGY EXCHANGE IN THE SOIL-PLANT-ATMOSPHERE-CLIMATE SYSTEM

Katul, Gabriel G.; Oren, Ram; Manzoni, Stefano; Higgins, Chad; Parlange, Marc B.; Manzoni, Stefano

Abstract

The role of evapotranspiration (ET) in the global, continental, regional, and local water cycles is reviewed. Elevated atmospheric CO2, air temperature, vapor pressure deficit (D), turbulent transport, radiative transfer, and reduced soil moisture all impact biotic and abiotic processes controlling ET that must be extrapolated to large scales. Suggesting a blueprint to achieve this link is the main compass of this review. Leaf-scale transpiration (f(e)) as governed by the plant biochemical demand for CO2 is first considered. When this biochemical demand is combined with mass transfer formulations, the problem remains mathematically intractable, requiring additional assumptions. A mathematical "closure" that assumes stomatal aperture is autonomously regulated so as to maximize the leaf carbon gain while minimizing water loss is proposed, which leads to analytical expressions for leaf-scale transpiration. This formulation predicts well the effects of elevated atmospheric CO2 and increases in D on f(e). The case of soil moisture stress is then considered using extensive gas exchange measurements collected in drought studies. Upscaling the f(e) to the canopy is then discussed at multiple time scales. The impact of limited soil water availability within the rooting zone on the upscaled ET as well as some plant strategies to cope with prolonged soil moisture stress are briefly presented. Moving further up in direction and scale, the soil-plant system is then embedded within the atmospheric boundary layer, where the influence of soil moisture on rainfall is outlined. The review concludes by discussing outstanding challenges and how to tackle them by means of novel theoretical, numerical, and experimental approaches.

Published in

Reviews of Geophysics
2012, Volume: 50, number: 3, article number: RG3002
Publisher: AMER GEOPHYSICAL UNION

      SLU Authors

      UKÄ Subject classification

      Forest Science

      Publication identifier

      DOI: https://doi.org/10.1029/2011RG000366

      Permanent link to this page (URI)

      https://res.slu.se/id/publ/41094