Evapotranspiration flux partitioning at a multi-species shrubland with stable isotopes of soil, plant, and atmosphere water pools

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Tonantzin Tarin
Enrico A. Yepez
Jaime Garatuza-Payan
Julio C. Rodriguez
Luis A. Méndez-Barroso
Christopher J. Watts
Enrique R. Vivoni

Abstract

Evapotranspiration is the second largest component of the hydrological cycle after rainfall precipitation in semiarid regions such as northwestern Mexico. In this study, we partitioned the evapotranspiration (ET) flux using stable isotopes of water in the soil-plant-atmosphere continuum in combination with eddy covariance flux measurements. We considered three methods for determining the isotopic composition of transpiration (δT): (1) isotopic steady state, (2) non-steady state, and (3) non-steady state weighting the relative importance of dominant species cover and accounting for the relative values of stomatal conductance. Three approaches of T/ET partitioning were estimated during several wet and dry days at the study site in Sonora, Mexico. The total ET flux was variable across years due to differences in precipitation amount between years. ET was lower during the drier-year and reached higher values during the wetter-year. Soil evaporation (E) dominated ET soon after large rain events (40 to 70 mm d–1 [DOY-196 and DOY-197] in 2008) but showed a rapid decrease in dominance as the soil surface dried. Estimated values of T/ET based on an isotopic mass balance were in the same range independent of three methods used. The mean T/ET ratio across all the periods studied was in the range of other studies in semiarid ecosystems and global trends with values of ~0.67 ± 0.02. This work contributes to a better understanding of the surface atmosphere interactions in semi-arid regions.

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Author Biographies

Tonantzin Tarin, University of Delaware, Newark, DE, USA

Department of Plant and Soil Sciences, 

Postdoctoral Research Associate

Enrico A. Yepez, Instituto Tecnológico de Sonora 5 de Febrero 818 Sur, Col. Centro Ciudad Obregón México, 85000

Profesor Investigador Titular C

Departamento de Ciencias del Agua y Medio Ambiente

Sistema Nacional del Ivestigadores nivel II

Jaime Garatuza-Payan, Instituto Tecnológico de Sonora 5 de Febrero 818 Sur, Col. Centro Ciudad Obregón México, 85000

Profesor Investigador Titular C

Departamento de Ciencias del Agua y Medio Ambiente

Sistema Nacional del Ivestigadores nivel II

Julio C. Rodriguez, Universidad de Sonora. Blvd. Luis Encinas y Rosales S/N, Col. Centro. 83000 Hermosillo, Sonora, México.

Departamento de Agricultura y Ganadería

Profesor Investigador Titular

Sistema Nacional del Ivestigadores nivel I

Luis A. Méndez-Barroso, Instituto Tecnológico de Sonora 5 de Febrero 818 Sur, Col. Centro Ciudad Obregón México, 85000

Profesor Investigador Titular A
Departamento de Ciencias del Agua y Medio Ambiente
Sistema Nacional del Ivestigadores nivel I

Christopher J. Watts, Universidad de Sonora. Blvd. Luis Encinas y Rosales S/N, Col. Centro. 83000 Hermosillo, Sonora, México.

Departamento de Fisica

Profesor Investigador Titular

Sistema Nacional del Ivestigadores nivel II

Enrique R. Vivoni, Arizona State University, Tempe, AZ, USA

PRofessor

School of Earth and Space Exploration and School of Sustainable Engineering and the Built Environment and 

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