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Evapotranspiration partitioning in a semiarid woodland; ecohydrologic heterogeneity and connectivity of vegetation patches

Brent D. Newman, David D. Breshears and Marvin O. Gard
Evapotranspiration partitioning in a semiarid woodland; ecohydrologic heterogeneity and connectivity of vegetation patches (in Coupling soil science and hydrology with ecology, Michael H. Young (prefacer), David A. Robinson (prefacer) and Ronald J. Ryel (prefacer))
Vadose Zone Journal (August 2010) 9 (3): 561-572


Partitioning evapotranspiration into its evaporation and transpiration components is critical for understanding ecohydrologic processes in drylands. Existing partitioning estimates, however, have not adequately accounted for the heterogeneity associated with woody plant canopy patches and intercanopy patches so characteristic of dryland ecosystems. We measured water contents, stable isotopes (delta (super 2) H and delta (super 18) O), Cl (super -) , and NO (sub 3) (super -) from core samples collected during an intense drought in canopy and intercanopy patches in a semiarid, pinon-juniper [Pinus edulis Engelm.-Juniperus monosperma (Engelm.) Sarg.] woodland in northern New Mexico to assess patch-scale heterogeneity and evapotranspiration partitioning. Soil zone residence times based on Cl (super -) ranged from 6 to 37 yr, highlighting the long time scale of percolation in these woodlands. The average NO (sub 3) (super -) concentration was nearly seven times lower in canopy patches, indicating substantial biogeochemical heterogeneity. Average delta (super 2) H values from shallow soil (<0.1 m) were 11 to 17 per mil lower in canopy patches, suggesting lower soil evaporation losses compared with intercanopy patches; however, significantly larger Cl (super -) inventories in canopy patches indicate up to four to six times more total evapotranspiration. Taken together, lower evaporation and greater evapotranspiration suggest that canopy patches have substantially larger transpiration rates and lower evaporation/transpiration ratios than intercanopy patches. Our results support a basic but untested conceptual model of patch connectivity where woody plants utilize substantial amounts of intercanopy water that has been redistributed from intercanopy to canopy patches via hydraulic gradients created by root uptake--a finding not generally modeled but potentially relevant to globally extensive patchy-structured drylands.

ISSN: 1539-1663
Serial Title: Vadose Zone Journal
Serial Volume: 9
Serial Issue: 3
Title: Evapotranspiration partitioning in a semiarid woodland; ecohydrologic heterogeneity and connectivity of vegetation patches
Title: Coupling soil science and hydrology with ecology
Author(s): Newman, Brent D.Breshears, David D.Gard, Marvin O.
Author(s): Young, Michael H.prefacer
Author(s): Robinson, David A.prefacer
Author(s): Ryel, Ronald J.prefacer
Affiliation: Los Alamos National Laboratory, Earth and Environmental Sciences Division, United States
Affiliation: Desert Research Institute, Division of Hydrologic Sciences, Las Vegas, NV, United States
Pages: 561-572
Published: 201008
Text Language: English
Publisher: Soil Science Society of America, Madison, WI, United States
References: 66
Accession Number: 2010-088900
Categories: Isotope geochemistryHydrogeology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch map
Source Medium: WWW
N35°45'00" - N35°57'00", W106°25'60" - W106°15'00"
Secondary Affiliation: Environment Centre Wales, GBR, United KingdomUtah State University, USA, United StatesUniversity of Arizona, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Soil Science Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201047
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