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Stable Carbon Isotopes δ13C as a Proxy for Characterizing Carbon Sources and Processes in a Small Tropical Headwater Catchment: Nsimi, Cameroon

Nkoue Ndondo, Gustave Raoul and Probst, Jean-Luc and Ndjama, J. and Ndam Ngoupayou, Jules Remy and Boeglin, J.-L. and Takem, G. E. and Brunet, Frédéric and Mortatti, Jefferson and Gauthier-Lafaye, François and Braun, J.-J. and Ekodeck, G. E. Stable Carbon Isotopes δ13C as a Proxy for Characterizing Carbon Sources and Processes in a Small Tropical Headwater Catchment: Nsimi, Cameroon. (2020) Aquatic Geochemistry, 26. 1-30. ISSN 1380-6165

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Official URL: https://doi.org/10.1007/s10498-020-09386-8

Abstract

Stream carbon fluxes are one of the major components in the global C cycle, yet the discrimination of the various sources of stream carbon remains to a large extent unclear and less is known about the biogeochemical transformations that accompany the transfer of C from soils to streams. Here, we used patterns in stream water and groundwater δ13C values in a small forested tropical headwater catchment to investigate the source and contribution from the soil carbon pools to stream organic and inorganic carbon behavior over seasonal scales. Stream organic carbon (DOC and POC) comes mainly from the upper rich soil organic carbon horizons and derived from total organic carbon (TOC) of biogenic source. The isotopic compositions δ13CTOC, δ13CDOC and δ13CPOC of these carbon species were very close (− 30‰ to − 26‰) and typical of the forested C3 vegetation. The relationship observed between DOC and log pCO2 and δ13CDIC indicated that besides the considerable CO2 evasion that occurs as DIC is transported from soils to streams, there were also other processes affecting the stream DIC pool. In-stream mineralization of DOC and mixing of atmospheric carbon had a significant influence on the δ13CDIC values. These processes which varied seasonally with hydrological changes represent the main control on DOC and DIC cycling in the wet tropical milieu. The rapid turnover of carbon on hillside soils, the transformation of TOC to DOC in wetland soils and further mineralization of stream DOC to DIC favor the evasion of C, making the zone a source of carbon to the atmosphere.

Item Type:Article
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National d'Études Spatiales - CNES (FRANCE)
French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
French research institutions > Institut de Recherche pour le Développement - IRD (FRANCE)
Other partners > University of Douala (CAMEROON)
Other partners > Université Louis Pasteur-Strasbourg I - ULP (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Other partners > Université de Yaoundé I (CAMEROON)
Other partners > Institut de Recherches Géologiques et Minières - IRGM (CAMEROON)
Other partners > Institut national des sciences de l'Univers - INSU (FRANCE)
Other partners > Universidade de São Paulo - USP (BRAZIL)
Laboratory name:
Funders:
SCAC Yaoundé - Toulouse INP - Laboratoire Ecologie fonctionnelle et Environnement, UMR CNRS 5245
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Deposited On:10 Jul 2020 13:06

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