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| Titel |
Erosion of particulate organic material from an Andean river and its
delivery to the Amazon Basin |
| VerfasserIn |
Kathryn Clark, Robert Hilton, A. Joshua West, Arturo Robles Caceres, Darren Gröcke, Toby Marthews, Greg Asner, Mark New, Yadvinder Mahli |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250134478
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| Publikation (Nr.) |
 EGU/EGU2016-15210.pdf |
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| Zusammenfassung |
| Organic carbon and nutrients discharged by mountainous rivers can play an important role in
biogeochemical cycles from regional to global scales. The eastern Andes host productive
forests on steep, rapidly eroding slopes, a combination that is primed to deliver sediment,
carbon and nutrients to the lowland Amazon River. We quantify clastic sediment
and particulate organic carbon (POC) discharge for the Kosñipata River, Peru, an
Andean tributary of the Madre de Dios River, using suspended sediment samples and
discharge measurements over one year at two gauging stations. Calculations of
sediment yield on the basis of this data suggest that the Madre de Dios basin may have
erosion rates ∼10 times greater than the Amazon Basin average. The total POC
yield over the sampling period was up to five times higher than the yield in the
lowland Amazon Basin, with most POC (70-80%) exported between December and
March in the wet season. We use radiocarbon, stable C isotopes and C/N ratios to
distinguish between the erosion and discharge of POC from sedimentary rocks
(petrogenic POC) and POC eroded from the modern terrestrial biosphere, from
vegetation and soil (biospheric POC). We find that biospheric POC discharge was
significantly enhanced during flood events, over that of clastic sediment and petrogenic
POC.
The ultimate fate of the eroded POC may play a central role in the net carbon budget of
Andean forest. In these forests, net productivity minus heterotrophic respiration is close to
zero at the scale of forest plots, and the erosion of biospheric POC by this Andean river is
sufficiently rapid that its fate downstream (sedimentary burial/preservation versus
oxidation/degradation) may determine whether the mountain forest is a carbon sink or source
to the atmosphere. In addition, the measured discharge of petrogenic POC suggests that
fluxes from the Andes may be considerably higher than measured downstream
in the Madeira River. If this petrogenic POC is oxidised rather than stored in the
Amazon River floodplains, it could contribute an important release of CO2 which is
not considered in forest-plot scale measurements. Overall, our results suggest that
the erosion of biospheric and petrogenic POC from the Andes and its discharge
by rivers comprise an important part of the organic carbon budget of the Amazon
River Basin, one that depends on the fate of material delivered to the lowlands. |
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