Chaplot Vincent auteur aut IRD Ribolzi Olivier auteur aut IRD text journalArticle eng text/pdf born digital access Dissolved organic carbon (DOC) is a key component of the global carbon cycle, but, to date, large uncertainties still exist on its source and fate in first-order streams. In a 23 ha rangeland and steep-slope headwater of South Africa, our aim was to quantify the contribution of overland flow (OF), soil water (SW) and ground water (GW) to DOC fluxes (DOCF), and to interpret the results in terms of DOC sources and fate. The average 2010-2011 DOC concentration (DOCC) at the catchment outlet was 4.7 mg C l(-1) with a standard error of +/- 2.5 mg C l(-1), which was significantly lower than in SW (15.2 +/- 1.6 mg C l(-1)) and OF (11.9 +/- 0.8 mg C l(-1)), but higher than in GW (2.3 +/- 0.6 mg C l(-1)). Based on end-member mixing using Si and Na concentration in the water compartments, the average SW contribution to DOCF was 66.4%, followed by OF (30.0%) and GW (3.6%). The resulting estimated DOCF at the catchment outlet was 8.05 g C m(2) y(-1). This was much higher than the observed value of 2.80 g C m(2) y(-1), meaning that 5.25 g C m(2) y(-1) or 65% of the DOC is lost during its downslope and/or downstream transport to the catchment outlet. Complementary investigations revealed that the DOCC in SW dropped from 15.2 +/- 1.6 to 2.6 +/- 0.3 mg C l(-1) during its downslope transport to the river system, which corresponded to a net loss of 5.10 g C m(2) y(-1), or 97% of the catchment DOC losses. These results on DOC sources and potential fate in headwaters are expected to improve our understanding of the impact of hydrology on the global C-cycle. specialized nutrient cycles global change greenhouse gases ecosystems carbon AFRIQUE DU SUD 062 064 082 021 28 21 5354-5366 2014 0885-6087 https://www.documentation.ird.fr/hor/fdi:010062610 10.1002/hyp.10010 0885-6087 [F B010062610] https://www.documentation.ird.fr/hor/fdi:010062610 https://www.documentation.ird.fr/intranet/publi/2014/11/010062610.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2014-12-05 2017-08-23 fdi:010062610 fre