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Controls on the D/H ratios of plant leaf waxes in an arid ecosystem

Feakins, Sarah J. and Sessions, Alex L. (2010) Controls on the D/H ratios of plant leaf waxes in an arid ecosystem. Geochimica et Cosmochimica Acta, 74 (7). pp. 2128-2141. ISSN 0016-7037.

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The extent to which leaf water D-enrichment (transpiration) and soil water D-enrichment (evaporation) affect the D/H ratio of plant leaf waxes remains a contentious issue, with important implications for paleohydrologic reconstructions. In this study we measure δD values of precipitation (δD_p), groundwater (δD_(gw)), plant xylem water (δD_(xw)) and leaf water (δD_(lw)) to understand their impact on the δD values of plant leaf wax n-alkanes (δD_(wax)) in an arid ecosystem. Our survey includes multiple species at four sites across an aridity gradient (80–30% relative humidity) in southern California. We find that many species take up groundwater or precipitation without significant fractionation. D-enriched soil water is a minor source even in species known to perform and utilize waters from hydraulic lift, such as Larrea tridentata (+10‰). Measurements of leaf water isotopic composition demonstrate that transpiration is an important mechanism for D-enrichment of leaf waters (+74 ± 20‰, 1σ), resulting in the smallest net fractionation yet reported between source water and leaf waxes (L. tridentata −41‰; multi-species mean value is −94 ± 21‰, 1σ). We find little change in leaf water D-enrichment or net fractionation across the climatic gradient sampled by our study, suggesting that a net fractionation of ca. −90‰ may be appropriate for paleohydrologic reconstructions in semi-arid to arid environments. Large interspecies offsets in net fractionations (1σ = 21‰) are potentially troublesome, given the observed floristic diversity and the likelihood of species assemblage changes with climate shifts.

Item Type:Article
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URLURL TypeDescription
Feakins, Sarah J.0000-0003-3434-2423
Sessions, Alex L.0000-0001-6120-2763
Additional Information:© 2010 Elsevier Ltd. Received 8 July 2009; accepted 5 January 2010; available online 15 January 2010. Part of this work was performed at the University of California (Riverside) Natural Reserve System (UCNRS) James Reserve and Sweeney Granite Mountain Desert Research Center. We are grateful to the assistance of Jim Andre, Jamie King and Michael Hamilton of the UCNRS for their assistance with plant identification and fieldwork support. Lauren Colloff assisted with fieldwork and sample preparation for the Topanga Canyon site. Michael Cheetham assisted with production of Fig. 1. Thanks to Darren Sandquist, Lisa Welp and Leonel Sternberg for helpful discussions and to the 6 anonymous reviewers. We gratefully acknowledge the support of the NOAA/UCAR Global and Climate Change postdoctoral fellowship to SF and NSF award EAR-0645502 to ALS.
Funding AgencyGrant Number
National Oceanic and Atmospheric Administration (NOAA)UNSPECIFIED
NSFEAR- 0645502
University Corporation for Atmospheric ResearchUNSPECIFIED
Issue or Number:7
Record Number:CaltechAUTHORS:20100406-110940817
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Official Citation:Sarah J. Feakins, Alex L. Sessions, Controls on the D/H ratios of plant leaf waxes in an arid ecosystem, Geochimica et Cosmochimica Acta, Volume 74, Issue 7, 1 April 2010, Pages 2128-2141, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17870
Deposited By: Ruth Sustaita
Deposited On:06 Apr 2010 20:24
Last Modified:03 Oct 2019 01:34

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