Transpiration alters the contribution of autotrophic and heterotrophic components of soil CO2 efflux

Authors

  • Charlotte Grossiord,

    1. Ecologie et Ecophysiologie Forestières, Faculté des Sciences, Université de Lorraine, UMR1137, F-54500 Vandoeuvre-les-Nancy, France
    2. CIRAD, UMR 111, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France
    3. INRA, UMR1137, Centre de Nancy, F-54280 Champenoux, France;
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  • Louis Mareschal,

    1. CIRAD, UMR 111, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France
    2. CRDPI, Centre de Recherche sur la Durabilité et la Productivité des Plantations Industrielles, BP 1291, Pointe-Noire, République du Congo
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  • Daniel Epron

    1. Ecologie et Ecophysiologie Forestières, Faculté des Sciences, Université de Lorraine, UMR1137, F-54500 Vandoeuvre-les-Nancy, France
    2. CIRAD, UMR 111, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France
    3. INRA, UMR1137, Centre de Nancy, F-54280 Champenoux, France;
    4. CRDPI, Centre de Recherche sur la Durabilité et la Productivité des Plantations Industrielles, BP 1291, Pointe-Noire, République du Congo
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Author for correspondence:
Daniel Epron
Tel: +33 3 83684249
Email: daniel.epron@scbiol.uhp-nancy.fr

Summary

  • An unbiased partitioning of autotrophic and heterotrophic components of soil CO2 efflux is important to estimate forest carbon budgets and soil carbon sequestration. The contribution of autotrophic sources to soil CO2 efflux (FA) may be underestimated during the daytime as a result of internal transport of CO2 produced by root respiration through the transpiration stream.
  • Here, we tested the hypothesis that carbon isotope composition of soil CO2 efflux (δFS) in a Eucalyptus plantation grown on a C4 soil is enriched during the daytime, which will indicate a decrease in FA during the periods of high transpiration.
  • Mean δFS of soil CO2 efflux decreased to −25.7‰ during the night and increased to −24.7‰ between 11:00 and 15:00 h when the xylem sap flux density was at its maximum.
  • Our results indicate a decrease in the contribution of root respiration to soil CO2 efflux during the day that may be interpreted as a departure of root-produced CO2 in the transpiration stream, leading to a 17% underestimation of autotrophic contribution to soil CO2 efflux on a daily timescale.

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