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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 8, issue 9
Biogeosciences, 8, 2437-2459, 2011
https://doi.org/10.5194/bg-8-2437-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Stable isotopes and biogeochemical cycles in terrestrial...

Biogeosciences, 8, 2437-2459, 2011
https://doi.org/10.5194/bg-8-2437-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Reviews and syntheses 06 Sep 2011

Reviews and syntheses | 06 Sep 2011

Diel variations in the carbon isotope composition of respired CO2 and associated carbon sources: a review of dynamics and mechanisms

C. Werner1 and A. Gessler2,3 C. Werner and A. Gessler
  • 1Experimental and Systems Ecology, University of Bielefeld, Universitätsstr. 25, 33615 Bielefeld, Germany
  • 2Institute for Landscape Biogeochemistry, Leibniz-Zentrum für Agrarlandschaftsforschung (ZALF) e.V., Eberswalderstr. 84, 15374 Müncheberg, Germany
  • 3Professorship for Landscape Biogeochemistry, Faculty of Agriculture and Horticulture, Humboldt University at Berlin, Lentze-Allee 75, 14195 Berlin, Germany

Abstract. Recent advances have improved our methodological approaches and theoretical understanding of post-photosynthetic carbon isotope fractionation processes. Nevertheless we still lack a clear picture of the origin of short-term variability in δ13C of respired CO213Cres) and organic carbon fractions on a diel basis. Closing this knowledge gap is essential for the application of stable isotope approaches for partitioning ecosystem respiration, tracing carbon flow through plants and ecosystems and disentangling key physiological processes in carbon metabolism of plants. In this review we examine the short-term dynamics in δ13Cres and putative substrate pools at the plant, soil and ecosystem scales and discuss mechanisms, which might drive diel δ13Cres dynamics at each scale. Maximum reported variation in diel δ13Cres is 4.0, 5.4 and 14.8 ‰ in trunks, roots and leaves of different species and 12.5 and 8.1 ‰ at the soil and ecosystem scale in different biomes. Temporal variation in post-photosynthetic isotope fractionation related to changes in carbon allocation to different metabolic pathways is the most plausible mechanistic explanation for observed diel dynamics in δ13Cres. In addition, mixing of component fluxes with different temporal dynamics and isotopic compositions add to the δ13Cres variation on the soil and ecosystem level. Understanding short-term variations in δ13Cres is particularly important for ecosystem studies, since δ13Cres contains information on the fate of respiratory substrates, and may, therefore, provide a non-intrusive way to identify changes in carbon allocation patterns.

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