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| Titel |
Greenhouse gas exchange of rewetted bog peat extraction sites and a Sphagnum cultivation site in northwest Germany |
| VerfasserIn |
C. Beyer, H. Höper |
| 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 ; 12, no. 7 ; Nr. 12, no. 7 (2015-04-07), S.2101-2117 |
| Datensatznummer |
250117890
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| Publikation (Nr.) |
 copernicus.org/bg-12-2101-2015.pdf |
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| Zusammenfassung |
During the last decades an increasing area of drained peatlands has been
rewetted. Especially in Germany, rewetting is the principal treatment on
cutover sites when peat extraction is finished. The objectives are bog
restoration and the reduction of greenhouse gas (GHG) emissions. The first sites were rewetted in the 1980s. Thus, there is a good opportunity to study
long-term effects of rewetting on greenhouse gas exchange, which has not
been done so far on temperate cutover peatlands. Moreover, Sphagnum
cultivating may become a new way to use cutover peatlands and agriculturally used peatlands as it permits the economical use of bogs
under wet conditions. The climate impact of such measures has not been
studied yet.
We conducted a field study on the exchange of carbon dioxide, methane and
nitrous oxide at three rewetted sites with a gradient from dry to wet
conditions and at a Sphagnum cultivation site in NW Germany over the
course of more than 2 years. Gas fluxes were measured using transparent and opaque
closed chambers. The ecosystem respiration (CO2) and the net ecosystem
exchange (CO2) were modelled at a high temporal resolution. Measured and
modelled values fit very well together. Annually cumulated gas flux rates,
net ecosystem carbon balances (NECB) and global warming potential (GWP)
balances were determined.
The annual net ecosystem exchange (CO2) varied strongly at the rewetted
sites (from −201.7 ± 126.8 to 29.7±
112.7g CO2-C m−2 a−1) due to differing weather
conditions, water levels and vegetation. The Sphagnum cultivation
site was a sink of CO2 (−118.8 ± 48.1 and −78.6 ±
39.8 g CO2-C m−2 a−1). The annual CH4 balances
ranged between 16.2 ± 2.2 and 24.2 ±
5.0g CH4-C m−2 a−1 at two inundated sites, while
one rewetted site with a comparatively low water level and the
Sphagnum farming site show CH4 fluxes close to 0. The net
N2O fluxes were low and not significantly different between the four
sites. The annual NECB was between −185.5 ± 126.9
and 49.9 ± 112.8 g CO2-C m−2 a−1 at the rewetted sites and −115.8 ± 48.1 and −77 ±
39.8 g CO2-C m−2 a−1 at the
Sphagnum cultivating site. The annual GWP100 balances
ranged from −280.5 ± 465.2 to 644.5 ±
413.6 g CO2-eq. m−2 a−1 at the rewetted sites. In
contrast, the Sphagnum farming site had a cooling impact on the
climate in both years (−356.8 ± 176.5 and −234.9 ±
145.9 g CO2-C m−2 a−1). If the carbon exported through the harvest of the Sphagnum biomass and the additional
CO2 emission from the decay of the organic material is considered, the
NECB and GWP100 balances are near neutral.
Peat mining sites are likely to become net carbon sinks and a peat
accumulating ("growing") peatland within 30 years of rewetting, but the
GWP100 balance may still be positive. A recommended measure for rewetting is
to achieve a water level of a few centimetres below ground.
Sphagnum farming is a climate-friendly alternative to conventional
commercial use of bogs. A year-round constant water level of a few
centimetres below ground level should be maintained. |
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