Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos
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 cultiv...
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doaj-c46d5e31f1aa4dfdaeffc3c9b729e47b2020-11-25T00:10:16ZengCopernicus PublicationsBiogeosciences1726-41701726-41892015-02-011241073108910.5194/bg-12-1073-2015Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern LaosE. Gourdin0S. Huon1O. Evrard2O. Ribolzi3T. Bariac4O. Sengtaheuanghoung5S. Ayrault6Laboratoire des Sciences du Climat et de l'Environnement (LSCE), UMR 8212 (CEA-CNRS-UVSQ-IPSL), Domaine du CNRS, avenue de la Terrasse, 91198 Gif-sur-Yvette CEDEX, FranceUniversité Pierre et Marie Curie (UPMC), UMR 7618 iEES (UPMC-CNRS-IRD-INRA-Université Paris 7-UPEC), case 120, 4 place Jussieu, 75252 Paris CEDEX 05, FranceLaboratoire des Sciences du Climat et de l'Environnement (LSCE), UMR 8212 (CEA-CNRS-UVSQ-IPSL), Domaine du CNRS, avenue de la Terrasse, 91198 Gif-sur-Yvette CEDEX, FranceIRD, Géosciences Environnement Toulouse (GET), UMR 5563 (CNRS-UPS-IRD), 14 avenue Edouard Belin, 31400 Toulouse, FranceCNRS, UMR 7618 iEES (UPMC-CNRS-IRD-INRA-Université Paris 7-UPEC), campus INRA – AgroParisTech, Bâtiment EGER, 78550 Thiverval-Grignon, FranceDepartment of Agriculture Land Management (DALam), P.O. Box 4199, Ban Nogviengkham, Xaythany District, Vientiane, LaosLaboratoire des Sciences du Climat et de l'Environnement (LSCE), UMR 8212 (CEA-CNRS-UVSQ-IPSL), Domaine du CNRS, avenue de la Terrasse, 91198 Gif-sur-Yvette CEDEX, FranceThe 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 km<sup>2</sup> 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 m<sup>2</sup> plot scale during a storm. The composition of particulate organic matter (total organic carbon and total nitrogen concentrations, δ<sup>13</sup>C and δ<sup>15</sup>N) was determined for suspended sediment, soil surface (top 2 cm) and soil subsurface (gullies and riverbanks) samples collected in the catchment (<i>n</i> = 57, 65 and 11, respectively). Hydrograph separation of event water was achieved using water electric conductivity and δ<sup>18</sup>O measurements for rainfall, overland flow and river water base flow (<i>n</i> = 9, 30 and 57, respectively). The composition of particulate organic matter indicates that upstream suspended sediments mainly originated from cultivated soils labelled by their C<sub>3</sub> vegetation cover (upland rice, fallow vegetation and teak plantations). In contrast, channel banks characterized by C<sub>4</sub> 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<sup>−1</sup>), total organic carbon specific yield (8.3 kg C ha<sup>−1</sup>) 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.http://www.biogeosciences.net/12/1073/2015/bg-12-1073-2015.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
E. Gourdin S. Huon O. Evrard O. Ribolzi T. Bariac O. Sengtaheuanghoung S. Ayrault |
spellingShingle |
E. Gourdin S. Huon O. Evrard O. Ribolzi T. Bariac O. Sengtaheuanghoung S. Ayrault Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos Biogeosciences |
author_facet |
E. Gourdin S. Huon O. Evrard O. Ribolzi T. Bariac O. Sengtaheuanghoung S. Ayrault |
author_sort |
E. Gourdin |
title |
Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos |
title_short |
Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos |
title_full |
Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos |
title_fullStr |
Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos |
title_full_unstemmed |
Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos |
title_sort |
sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern laos |
publisher |
Copernicus Publications |
series |
Biogeosciences |
issn |
1726-4170 1726-4189 |
publishDate |
2015-02-01 |
description |
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 km<sup>2</sup> 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 m<sup>2</sup> plot scale during a
storm. The composition of particulate organic matter (total organic carbon
and total nitrogen concentrations, δ<sup>13</sup>C and δ<sup>15</sup>N) was
determined for suspended sediment, soil surface (top 2 cm) and soil
subsurface (gullies and riverbanks) samples collected in the catchment (<i>n</i>
= 57, 65 and 11, respectively). Hydrograph separation of event water was
achieved using water electric conductivity and δ<sup>18</sup>O measurements
for rainfall, overland flow and river water base flow (<i>n</i> = 9, 30 and 57,
respectively). The composition of particulate organic matter indicates that
upstream suspended sediments mainly originated from cultivated soils labelled
by their C<sub>3</sub> vegetation cover (upland rice, fallow vegetation and teak
plantations). In contrast, channel banks characterized by C<sub>4</sub> 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<sup>−1</sup>), total organic carbon specific
yield (8.3 kg C ha<sup>−1</sup>) 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. |
url |
http://www.biogeosciences.net/12/1073/2015/bg-12-1073-2015.pdf |
work_keys_str_mv |
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