title: Transpiration alters the contribution of autotrophic and heterotrophic components of soil CO2 efflux.
abstract: • An unbiased partitioning of autotrophic and heterotrophic components of soil CO(2) efflux is important to estimate forest carbon budgets and soil carbon sequestration. The contribution of autotrophic sources to soil CO(2) efflux (F(A)) may be underestimated during the daytime as a result of internal transport of CO(2) produced by root respiration through the transpiration stream. • Here, we tested the hypothesis that carbon isotope composition of soil CO(2) efflux (δ(FS)) in a Eucalyptus plantation grown on a C(4) soil is enriched during the daytime, which will indicate a decrease in F(A) during the periods of high transpiration. • Mean δ(FS) of soil CO(2) 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 CO(2) efflux during the day that may be interpreted as a departure of root-produced CO(2) in the transpiration stream, leading to a 17% underestimation of autotrophic contribution to soil CO(2) efflux on a daily timescale.
authors.affiliation: Ecologie et Ecophysiologie Forestières, Faculté des Sciences, Université de Lorraine, UMR1137, F-54500 Vandoeuvre-les-Nancy, France.|CIRAD, UMR 111, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France.|INRA, UMR1137, Centre de Nancy, F-54280 Champenoux, France.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Grossiord
authors.affiliation: CIRAD, UMR 111, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France.|CRDPI, Centre de Recherche sur la Durabilité et la Productivité des Plantations Industrielles, BP 1291, Pointe-Noire, République du Congo.
authors.forename: Louis
authors.initials: L
authors.lastname: Mareschal
authors.affiliation: Ecologie et Ecophysiologie Forestières, Faculté des Sciences, Université de Lorraine, UMR1137, F-54500 Vandoeuvre-les-Nancy, France.|CIRAD, UMR 111, Ecologie Fonctionnelle & Biogéochimie des Sols & Agro-écosystèmes, F-34060 Montpellier, France.|INRA, UMR1137, Centre de Nancy, F-54280 Champenoux, France.|CRDPI, Centre de Recherche sur la Durabilité et la Productivité des Plantations Industrielles, BP 1291, Pointe-Noire, République du Congo.
authors.forename: Daniel
authors.initials: D
authors.lastname: Epron
mesh_terms: D052818:Autotrophic Processes / Q000502:physiology*; D001692:Biological Transport; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D019069:Cell Respiration; D002980:Climate; D003223:Congo; D005052:Eucalyptus / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D052836:Heterotrophic Processes / Q000502:physiology*; D006813:Humidity; D018517:Plant Roots / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects; D018526:Plant Transpiration / Q000502:physiology*; D011827:Radiation; D012987:Soil / Q000737:chemistry*; D013696:Temperature; D052584:Xylem / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects
chemical_list: D002247:Carbon Isotopes; D012987:Soil; D002245:Carbon Dioxide