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| Titel |
Soil carbon cycling and sequestration in a seasonally saturated wetland receiving agricultural runoff |
| VerfasserIn |
J. J. Maynard, R. A. Dahlgren, A. T. O'Geen |
| 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 ; 8, no. 11 ; Nr. 8, no. 11 (2011-11-23), S.3391-3406 |
| Datensatznummer |
250006207
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| Publikation (Nr.) |
 copernicus.org/bg-8-3391-2011.pdf |
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| Zusammenfassung |
| The fate of organic carbon (C) lost by erosion is not well understood in
agricultural settings. Recent models suggest that wetlands and other small
water bodies may serve as important long-term sinks of eroded C, receiving
~30 % of all eroded material in the US. To better understand the
role of seasonally-saturated wetlands in sequestering eroded C, we examined
the spatial and temporal dynamics of C and sediment accumulation in a
13-year-old constructed wetland used to treat agricultural runoff. The fate
of C sequestered within deposited sediment was modeled using point-sampling,
remote sensing, and geostatistics. Using a spatially-explicit sampling
design, annual net rates of sedimentation and above-ground biomass were
measured during two contrasting years (vegetated (2004) vs. non-vegetated
(2005)), followed by collection of sediment cores to the antecedent soil
layer, representing 13 years of sediment and C accumulation. We documented
high annual variation in the relative contribution of endogenous and
exogenous C sources, as well as absolute rates of sediment and C deposition.
This annual variation, however, was muted in the long-term (13 yr) sediment
record, which showed consistent vertical patterns of uniform C distribution
(~14 g kg–1) and δ13C signatures in high
depositional environments. This was in contrast to low depositional
environments which had high levels of surface C enrichment (20–35 g kg–1)
underlain by C depleted (5–10 g kg–1) sediments and an
increasing δ13C signature with depth indicating increased
decomposition. These results highlight the importance of sedimentation in
physically protecting soil organic carbon and its role in controlling the
long-term C concentration of seasonally-saturated wetland soils. While
significant enrichment of surface sediments with endogenous C occurred in
newly deposited sediment (i.e., 125 kg m2 in 2004), fluctuating
cycles of flooding and drying maintained the long-term C concentration at the same
level as inflowing sediment (i.e., 14 g kg–1), indicating no additional
long-term storage of endogenous C. These results demonstrate that
constructed flow-through wetlands can serve as important sinks for eroded C
and sediment in agricultural landscapes, however, additional C sequestration
via enrichment from endogenous sources may be limited in
seasonally-saturated wetlands due to rapid decomposition during drying
cycles. |
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