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| Titel |
Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos |
| VerfasserIn |
E. Gourdin, S. Huon, O. Evrard, O. Ribolzi, T. Bariac, O. Sengtaheuanghoung, S. Ayrault |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 4 ; Nr. 12, no. 4 (2015-02-19), S.1073-1089 |
| Datensatznummer |
250117824
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| Publikation (Nr.) |
 copernicus.org/bg-12-1073-2015.pdf |
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| Zusammenfassung |
| The yields of the tropical rivers of Southeast Asia supply large quantities of carbon to
the ocean. The origin and dynamics of particulate organic matter were studied
in the Houay Xon River catchment located in northern Laos during the first
erosive flood of the rainy season in May 2012. This cultivated catchment is
equipped with three successive gauging stations draining areas ranging
between 0.2 and 11.6 km2 on the main stem of the permanent stream, and
two additional stations draining 0.6 ha hillslopes. In addition, the
sequential monitoring of rainwater, overland flow and suspended organic
matter compositions was conducted at the 1 m2 plot scale during a
storm. The composition of particulate organic matter (total organic carbon
and total nitrogen concentrations, δ13C and δ15N) was
determined for suspended sediment, soil surface (top 2 cm) and soil
subsurface (gullies and riverbanks) samples collected in the catchment (n
= 57, 65 and 11, respectively). Hydrograph separation of event water was
achieved using water electric conductivity and δ18O measurements
for rainfall, overland flow and river water base flow (n = 9, 30 and 57,
respectively). The composition of particulate organic matter indicates that
upstream suspended sediments mainly originated from cultivated soils labelled
by their C3 vegetation cover (upland rice, fallow vegetation and teak
plantations). In contrast, channel banks characterized by C4 vegetation
(Napier grass) supplied significant quantities of sediment to the river
during the flood rising stage at the upstream station as well as in
downstream river sections. The highest runoff coefficient (11.7%),
sediment specific yield (433 kg ha−1), total organic carbon specific
yield (8.3 kg C ha−1) and overland flow contribution (78–100%)
were found downstream of reforested areas planted with teaks. Swamps located
along the main stream acted as sediment filters and controlled the
composition of suspended organic matter. Total organic carbon specific yields
were particularly high because they occurred during the first erosive storm
of the rainy season, just after the period of slash-and-burn operations in
the catchment. |
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