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| Titel |
Peatland restoration measures may have dramatic consequences – Greenhouse gas exchange and peat properties in a coastal fen in the first year after rewetting |
| VerfasserIn |
Gerald Jurasinski, Juliane Hahn, Stefan Köhler, Stephan Glatzel |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110964
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| Publikation (Nr.) |
 EGU/EGU2015-11012.pdf |
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| Zusammenfassung |
| Rewetting is a common restoration measure for drained peatlands, i.e.Âto re-establish the
natural habitat and biodiversity and to decrease the amount of greenhouse gas (GHG)
emissions, especially of carbon dioxide (CO2). Every restoration measure, however, is itself
disturbance to the ecosystem that may, for instance, lead to partial die-back of vegetation or
to increases in CH4 emissions, especially when rewetting is actually achieved by
flooding.
Here, we examine an ecosystem shift in a coastal brackish fen at the southern Baltic Sea,
which was rewetted by flooding. The analyses are based on one year of bi-weekly dynamic
closed chamber data gathered in the year after rewetting at measurement spots that
were located in different vegetation stands (Carex acutiformis Ehrh., Phragmites
australis L., Schoenoplectus tabernaemontani (C.C. Gmel.) Palla and Bolboschoenus
maritimus (L.) Palla) and replicated at different inundation heights. During GHG
measurement campaigns we recorded data on water levels, peat temperatures, and peat
water chemical properties. Peat chemical properties were analysed before and after
flooding.
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. Peat water properties became more heterogeneous.
Both TOC and TNb in the peat water significantly increased in the first year after
flooding, whilst concentrations of (potentially) seaborne anions Cl- and SO42-
dropped. The changes in peat properties after flooding were inconsistent across
vegetation stands, inundation heights and peat depths. Only dry bulk density and
concentrations of C, N and S increased at (almost) all measurement spots. The average
exchange of GHG amounted to 0.26 ± 0.06 kg m-2 CH4 and 2.13 ± 0.34 kg m-2
CO2 from dark soil respiration. This is equivalent to a 190-times increase in CH4
compared to pre-flooding conditions. Highest GHG fluxes occurred in sedge stands that
suffered from the heaviest die-back due to water level rise. None of the recorded
environmental variables showed consistent correlation with the amounts of CH4 and CO2
exchanged.
In the short term perspective covered in this study, rewetting by flooding did not – especially
due to the dramatic increase in CH4 emissions – decrease GHG emissions. Furthermore, we
observed an overall destabilization of the ecosystem functioning: The environmental
parameters that are commonly used to explain variation in GHG exchange did not show any
consistent correlation and some showed dramatic changes when comparing pre- and
post-flooding. Our results suggest that rewetting projects should be monitored not only with
regard to vegetation development but also with respect to biogeochemical conditions. Further,
high 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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