EGU2020-3343, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-3343
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The dominant environmental driver of leaf water stable isotope enrichment differs for H-2 compared to O-18

Matthias Cuntz1, Lucas A Cernusak2, and the Isotopists*
Matthias Cuntz and Lucas A Cernusak and the Isotopists
  • 1Université de Lorraine, AgroParisTech, INRAE, UMR Silva, Nancy, France (matthias.cuntz@inrae.fr)
  • 2James Cook University, Cairns, Australia
  • *A full list of authors appears at the end of the abstract

Several important isotopic biomarkers derive at least part of their signal from the stable isotope composition of leaf water (e.g., leaf wax δ2H, cellulose δ2H and δ18O, lignin δ18O). In order to interpret these isotopic proxies, it is therefore helpful to know which environmental variable most strongly controls a given leaf water stable isotope signal. We collated observations of the stable isotope compositions of leaf water, xylem water, and atmospheric vapour, along with air temperature and relative humidity, to test whether the dominant driver of leaf water 2H concentration could differ from that of 18O concentration. Our dataset comprises 690 observations from 35 sites with broad geographical coverage. We limited our analysis to daytime observations, when the photosynthetic processes that incorporate the leaf water isotopic signal primarily take place. The Craig-Gordon equation was generally a good predictor for daytime bulk leaf water stable isotope composition for both δ2H (R2=0.86, p<0.001) and δ18O (R2=0.63, p<0.001). It showed about 10% admixture of source water was caused by unenriched water pools such as leaf veins or the Péclet effect. Solving the Craig-Gordon equation requires knowledge of relative humidity, air temperature, and the stable isotope compositions of source water and atmospheric vapour. However, it is not possible to invert the Craig-Gordon equation to solve for one of these parameters unless the others are known. Here we show that the two isotopic signals of δ2H and δ18O are predominantly driven by different environmental variables: leaf water δ2H correlated most strongly with the δ2H of source water (R2=0.68, p<0.001) and atmospheric vapour (R2=0.63, p<0.001), whereas leaf water δ18O correlated most strongly with air relative humidity (R2=0.46, p<0.001). We conclude that these two isotopic signals of leaf water are not simply mirror images of the same environmental information, but carry distinct signals of different climate factors, with crucial implications for the interpretation of downstream isotopic biomarkers.

Isotopists:

Adrià Barbeta (12,20), Rebekka Bögelein (3), Rosemary T Bush (4), Juan Pedro Ferrio (5), Lawrence B Flanagan (6), Arthur Gessler (7), Paula Martín-Gómez (12), Regina Hirl (8), Ansgar Kahmen (9), Claudia Keitel (10), Chun-Ta Lai (11), Niels Munksgaard (2), Daniel B Nelson (9), Jérôme Ogée (12), John S Roden (14), Hans Schnyder (8), Steven Voelker (17), Lixin Wang (16), Hilary Stuart-Williams (13), Lisa Wingate (12), Wusheng Yu (18), Liangju Zhao (19) -- (3) University of Trier, Faculty of Regional and Environmental Sciences – Geobotany, Trier, Germany (4) Northwestern University, Evanston, IL, United States (5) ARAID-Forest Resources Unit, Agrifood Research and Technology Centre of Aragón (CITA), Zaragoza, Spain (6) University of Lethbridge, Lethbridge, AB, Canada (7) WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland (8) Technische Universität München, Freising, Germany (9) University of Basel, Environmental Sciences – Botany, Basel, Switzerland (10) University of Sydney, Sydney, Australia (11) San Diego State University, San Diego, CA, United States (12) INRAE Bordeaux-Aquitaine, Villenave d'Ornon Cedex, France (13) Australian National University, Canberra, Australia (14) Southern Oregon University, Ashland, OR, United States (15) Utah State University, Department of Plants, Soils and Climate, Logan, UT, United States (16) Indiana University Purdue University Indianapolis, Department of Earth Sciences, Indianapolis, IN, United States (17) Department of Environmental and Forest Biology, State University of New York, Syracuse, NY, United States (18) Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China (19) Northwest University, Xi'an, China (20) BEECA, Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, Barcelona, Catalonia, Spain

How to cite: Cuntz, M. and Cernusak, L. A. and the Isotopists: The dominant environmental driver of leaf water stable isotope enrichment differs for H-2 compared to O-18, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3343, https://doi.org/10.5194/egusphere-egu2020-3343, 2020

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Display material version 1 – uploaded on 01 May 2020
  • CC1: Comment on EGU2020-3343, Grzegorz Skrzypek, 07 May 2020

    Hi Matthias

    What method did you use for analyses of leaf stable isotope composition?

     

    Best regards

     

    Greg

    grzegorz.skrzypek@uwa.edu.au

    • AC1: Reply to CC1, Matthias Cuntz, 08 May 2020

      Dear Grzegorz,

      this is a meta analysis, so isotopes were measured with a variety of methods. But most people measured leaf water from cryogenic extraction and water vapour with ice traps. I would say that most data predates the laser methods. But I would have to check that.

       

      Kind regards
      Matthias