Changes in carbon and nutrient fluxes from headwaters to ocean in a mountainous temperate to subtropical basin

Mutema, M and Chivenge, P and Nivet, F and Rabouille, C and Thieu, V and Chaplot, V (2017) Changes in carbon and nutrient fluxes from headwaters to ocean in a mountainous temperate to subtropical basin. Earth Surface Processes and Landforms, 42 (13). pp. 2038-2053. ISSN 01979337

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Water erosion provides major links in global cycles of carbon (C), nitrogen (N) and phosphorus (P). Although significant research on erosion mechanisms has been done, there is still little knowledge on C, N and P fluxes across landscapes to the ocean and their controlling factors in subtropical climates. A four-year study quantifying and comparing particulate and dissolved C, N and P from multiple scales (microplot, plot, microcatchment, subcatchment, catchment, sub-basin and basin) was performed in Thukela basin (≈30 000 km2), South Africa. The basin climate was largely subtropical-humid [mean annual precipitation (MAP) > 980 mm yr-1], but temperate (MAP >2000 mm yr-1) on the highlands. Open grassland, cropland and bushland were the major land uses. On average, 65, 24 and 4 g m-2 yr-1 C, N and P were displaced from original topsoil positions, but only 0.33, 0.005 and 0.002 mg m-2 yr-1 were, respectively, exported to the ocean. The fluxes decreased by 95, 97 and 84%, respectively, from plot to microcatchment outlet; and decreased further in downstream direction by >99% from microcatchment to basin outlet. The hillslope (microplot to microcatchment) fluxes correlated strongly with rainfall parameters. Particulate contributions dominated hillslope fluxes at 73, 81 and 76% of total annual C, N and P, respectively. Although particulate C dominated in the microcatchment-catchment reach (55%), N (54%) and P (69%) were dominated by dissolved forms. The lower basin zone was dominated by dissolved flux contributions at 93, 81 and 78% for C, N and P for the sub-basin outlet. These results suggested spatially varying drivers of C, N and P losses from the landscape to the ocean, via the river network. Deposition was envisaged the dominant hillslope level loss process, which gradually gave way to mineralization and biotic uptake in the river network as flux contributions shifted from being predominantly particulate to dissolved forms.

Item Type: Article
Divisions: Research Program : East & Southern Africa
Uncontrolled Keywords: Mineralization; C and nutrient fluxes; preferential detachment; selective deposition; transitory sites
Subjects: Others > Soil
Others > Climate Change
Others > Water Resources
Depositing User: Mr Ramesh K
Date Deposited: 29 Nov 2017 08:17
Last Modified: 29 Nov 2017 08:17
Official URL:
Projects: WHaTeR Project
Funders: European Community’s Seventh Framework Programme
Acknowledgement: The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under the WHaTeR project (Water Harvesting Technologies Revisited) grant agreement no. 266360 and the Water Research Commission of the Republic of South Africa (WRC K5/2266). Since gratitude also goes toMr DanielMuller-Nedebock and Miss Humbelani F. Thenga, colleagues of the main author during the PhD study bearing the results presented here, for collaborative assistance during field data collection.
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