Evapotranspiration: A process driving mass transport and energy exchange in the soil‐plant‐atmosphere‐climate system

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 (fe) 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 fe. The case of soil moisture stress is then considered using extensive gas exchange measurements collected in drought studies. Upscaling the fe 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.

Qualitative Performance and Consumer Acceptability of Starch Films for the Blueberry Modified Atmosphere Packaging Storage

“…For each wrapping fi lm, the effect of the high temperature (20±1°C) was more obvious in terms of blueberry weight loss than at 1±1°C; the highest weight losses were observed for the control (5.30%). This trend is expected because as the temperature increases, the free energy of water molecules also increases and thus enhances the molecular movement, and the potential for exchange [Katul et al, 2012]. At the end of the storage time (18 days), the F3 fi lm showed the lowest weight losses (2.48%).…”

A comparison of methods for determining field evapotranspiration: photosynthesis system, sap flow, and eddy covariance

“…As shown in the evapotranspiration partition results in this study, a portion of soil evaporation is significantly reduced through mulched drip irrigation, and most of the water is consumed by plant transpiration during the analysis periods. Because transpiration is accompanied by photosynthesis and plant productivity, higher transpiration indicates a better crop yield (Katul et al, 2012), and mulched drip irrigation tends to improve water use efficiency. Compared to the fraction of cotton transpiration to evapotranspiration of 65 % (Tang et al, 2010) and 56 % observed under traditional flood irrigation conditions during the same cotton growth stages (flower and bolling stages), the fraction of 87.1 % before irrigation and 82.3 % after irrigation that were obtained in this study are much higher, which confirms that mulched drip irrigation is a more efficient method for achieving water savings.…”

“…Evapotranspiration (ET) is a major component in energy balance and water cycling (Katul et al, 2012). Much effort has been devoted to the measurement of ET because it is a critically important process in many fields, including hydrology, ecology, agriculture, forestry, and horticulture.…”

Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest

“…Evapotranspiration (ET) accounts for 60-95% of precipitated water in terrestrial ecosystems, comprising the one of the largest components of the terrestrial hydrologic cycle [Fisher et al, 2005;Ford et al, 2007;Jasechko et al, 2013;Katul et al, 2012]. Transpiring vegetation recycles~62,000 km 3 of water, while sequestering~130 Gt of carbon annually at the global scale [Jasechko et al, 2013].…”