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| Titel |
Turn on, fade out – methane exchange in a coastal fen over a period of six years after rewetting |
| VerfasserIn |
Gerald Jurasinski, Stephan Glatzel, Juliane Hahn, Stefan Koch, Marian Koch, Franziska Koebsch |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250134200
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| Publikation (Nr.) |
 EGU/EGU2016-14899.pdf |
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| Zusammenfassung |
| The rewetting of drained peatlands is widely regarded as an adequate measure for the
mitigation of greenhouse gas emissions. Therefore, especially in NE Germany, many
peatlands are being rewetted. Our knowledge about greenhouse gas exchange associated with
rewetting is mainly based on short-term experiments or space-for-time substitutions. These
approaches do not consider the transient character of ecosystem acclimatization to
flooding by rewetting. Moreover data in this regard on coastal peatland ecosystems are
sparse.
Here, we present 7 years of data on CH4-exchange in a coastal fen after rewetting by
flooding. On the site „Rodewiese“, which is located within the NSG “Hütelmoor und
Heiligensee” in the Northeast of Rostock, NE Germany, we have established a long term
research observatory addressing atmospheric C-exchange. The site is part of the TERENO
network. Since summer 2009 we determine CH4 fluxes with closed chambers distributed
widely across the study site and CO2-exchange with eddy covariance as well as ancillary data
on vegetation, hydrology, and biogeochemistry. This talk addresses the CH4-exchange
over time whereas CO2-exchange data are presented by Koebsch et al. in the same
session.
Rewetting turned the site from a summer dry fen with mean annual water levels of around
-0.08m into a shallow lake with water levels up to 0.60m. In the first year after flooding, we
observed a substantial die-back of vegetation, especially in stands of Carex acutiformis.
Flooding increased methane release rates to extremely high levels of up to 4.3 t
ha−1 a−1 for sedge stands and 2.7 t ha−1 a−1 on average, which amounts to 75.6
t ha−1 a−1 in CO2-equivalents. Thereafter, the averaged annual CH4 emissions
decreased asymptotically and where at an average of 0.5 t ha−1 a−1 (14 t ha−1 a−1 in
CO2-equivalents) in 2015. Factoring in the NEE of the growing season (from Eddy
measurements) suggests that the system may be slightly above neutral with respect
to the greenhouse warming potential of its atmospheric C-exchange 7 years after
flooding. Analyses of peat and water biochemistry showed that the system had been
destabilized in the first year following flooding and repeated vegetation analysis
combined with remote sensing reveal strong and directed change in vegetation
patterns.
The successional development in atmospheric C-exchange in the 6 years after flooding
hint at an adaptation of ecosystem functioning to the flooded conditions associated with
reaching desirable annual rates of C-exchange and vegetation development during an
acceptable time frame. However, high CH4 emissions and a slow recovery to lower CH4
emissions that likely occur directly after rewetting by flooding should be considered when
forecasting the overall effect of rewetting on GHG exchange of a particular site. |
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