 |
| Titel |
Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River basin |
| VerfasserIn |
A. L. Zuijdgeest, R. Zurbrügg, N. Blank, R. Fulcri, D. B. Senn, B. Wehrli |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 24 ; Nr. 12, no. 24 (2015-12-21), S.7535-7547 |
| Datensatznummer |
250118225
|
| Publikation (Nr.) |
 copernicus.org/bg-12-7535-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
Floodplains are important biogeochemical reactors during fluvial transport
of carbon and nutrient species towards the oceans. In the tropics and
subtropics, pronounced rainfall seasonality results in highly dynamic
floodplain biogeochemistry. The massive construction of dams, however, has
significantly altered the hydrography and chemical characteristics of many
(sub)tropical rivers. In this study, we compare organic-matter and nutrient
biogeochemistry of two large, contrasting floodplains in the Zambezi River
basin in southern Africa: the Barotse Plains and the Kafue Flats. Both
systems are of comparable size but differ in anthropogenic influence: while
the Barotse Plains are still in large parts pristine, the Kafue Flats are
bordered by two hydropower dams.
The two systems exhibit different flooding dynamics, with a larger
contribution of floodplain-derived water in the Kafue Flats and a stronger
peak flow in the Barotse Plains. Distinct seasonal differences have been
observed in carbon and nutrient concentrations, loads, and export and
retention behavior in both systems. The simultaneous retention of particulate
carbon and nitrogen and the net export of dissolved organic and inorganic
carbon and nitrogen suggested that degradation of particulate organic matter
was the dominant process influencing the river biogeochemistry during the
wet season in the Barotse Plains and during the dry season in the Kafue
Flats. Reverse trends during the dry season indicated that primary
production was important in the Barotse Plains, whereas the Kafue Flats
seemed to have both primary production and respiration occurring during the
wet season, potentially occurring spatially separated in the main channel
and on the floodplain.
Carbon-to-nitrogen ratios of particulate organic matter showed that
soil-derived material was dominant year-round in the Barotse Plains, whereas
the Kafue Flats transported particulate organic matter that had been
produced in the upstream reservoir during the wet season. Stable carbon
isotopes suggested that inputs from the inundated floodplain to the
particulate organic-matter pool were important during the wet season,
whereas permanent vegetation contributed to the material transported during
the dry season. This study revealed effects of dam construction on organic-matter and nutrient dynamics on the downstream floodplain that only become
visible after longer periods, and it highlights how floodplains act as large
biogeochemical reactors that can behave distinctly differently from the entire
catchment. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|