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| Titel |
High soil solution carbon and nitrogen concentrations in a drained Atlantic bog are reduced to natural levels by 10 years of rewetting |
| VerfasserIn |
S. Frank, B. Tiemeyer, J. Gelbrecht, A. Freibauer |
| 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 ; 11, no. 8 ; Nr. 11, no. 8 (2014-04-25), S.2309-2324 |
| Datensatznummer |
250117376
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| Publikation (Nr.) |
 copernicus.org/bg-11-2309-2014.pdf |
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| Zusammenfassung |
Anthropogenic drainage of peatlands releases additional greenhouse gases to the
atmosphere, and dissolved carbon (C) and nutrients to downstream ecosystems.
Rewetting drained peatlands offers a possibility to reduce nitrogen (N) and
C losses. In this study, we investigate the impact of drainage and rewetting
on the cycling of dissolved C and N as well as on dissolved gases, over a
period of 1 year and a period of 4 months. We chose four sites within one
Atlantic bog complex: a near-natural site, two drained grasslands with
different mean groundwater levels and a former peat cutting area rewetted
10 years ago.
Our results clearly indicate that long-term drainage has increased the
concentrations of dissolved organic carbon (DOC), ammonium, nitrate and
dissolved organic nitrogen (DON) compared to the near-natural site. DON and
ammonium contributed the most to the total dissolved nitrogen. Nitrate
concentrations below the mean groundwater table were negligible. The
concentrations of DOC and N species increased with drainage depth. In the
deeply-drained grassland, with a mean annual water table of 45 cm below
surface, DOC concentrations were twice as high as in the partially rewetted
grassland with a mean annual water table of 28 cm below surface. The deeply
drained grassland had some of the highest-ever observed DOC concentrations of
195.8 ± 77.3 mg L−1 with maximum values of
>400 mg L−1. In general, dissolved organic matter (DOM) at the
drained sites was enriched in aromatic moieties and showed a higher
degradation status (lower DOC to DON ratio) compared to the near-natural
site. At the drained sites, the C to N ratios of the uppermost peat layer
were the same as of DOM in the peat profile. This suggests that the uppermost
degraded peat layer is the main source of DOM. Nearly constant DOM quality
through the profile furthermore indicated that DOM moving downwards through
the drained sites remained largely biogeochemically unchanged. Unlike DOM
concentration, DOM quality and dissolved N species distribution were similar
in the two grasslands and thus unaffected by the drainage depth.
Methane production during the winter months at the drained sites was limited
to the subsoil, which was quasi-permanently water saturated. The recovery of
the water table in the winter months led to the production of nitrous oxide
around mean water table depth at the drained sites.
The rewetted and the near-natural site had comparable DOM quantity and
quality (DOC to DON ratio and aromaticity). 10 years after rewetting quasi-pristine biogeochemical conditions have been re-established under
continuously water logged conditions in the former peat cut area. Only the
elevated dissolved methane and ammonium concentrations reflected the former
disturbance by drainage and peat extraction. Rewetting via polder technique
seems to be an appropriate way to revitalize peatlands on longer timescales
and to improve the water quality of downstream water bodies. |
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