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| Titel |
Water table depth regulates evapotranspiration and methane flux of a near-pristine temperate lowland fen measured by eddy covariance and static chambers |
| VerfasserIn |
Jorg Kaduk, Gong Pan, Alex Cumming, Jon Evans, Jon Kelvin, Mike Peacock, Vincent Gauci, John Hughes, Susan Page, Heiko Balzter |
| 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 |
250107861
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| Publikation (Nr.) |
 EGU/EGU2015-7579.pdf |
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| Zusammenfassung |
| Methane is the second most important greenhouse gas after carbon dioxide, although the
current atmospheric concentration is only about two parts per million. This results from a
radiative forcing of 0.48 +/-0.05 Wm-2, about 26 times that of carbon dioxide. Atmospheric
concentrations as well as emissions to the atmosphere have been increasing strongly over the
last decades. Emissions are to a large extent biogenic where the largest biogenic source,
wetlands, has the largest uncertainty. This precludes the construction of a reliable global
methane budget, as well as meaningful predictions, as results from wetland models are
uncertain and there are insufficient data for model improvement. We measured
evapotranspiration and methane flux of a near-pristine temperate lowland fen in East Anglia
in the United Kingdom from July 2013 to June 2014 by eddy covariance, which represents
the first annual cycle of eddy covariance measurements of methane flux in this category of
wetland. Methane fluxes from vegetation and ditches were additionally measured separately
with static chambers. Annual evapotranspiration was 720.4 to 732.6 mm yr-1. Annual
methane release was 3.77 to 4.03 g CH4 m-2 yr-1. Water table and methane fluxes were very
different in the two half years: an average of -0.63 nmol CH4 m-2s-1 (a net uptake) for
July-December 2013 and 16.2 nmol CH4 m-2s-1 (a net release) for January-June 2014
with a data range of -99 to 410 nmol CH4 m-2s-1 over the full year. Water table
has the dominant role in determining methane flux and, under a very low water
table, methane uptake was observed. Temperature has a clear impact on fluxes at
high water tables. Eddy covariance and chamber measurements show the same
annual pattern flux magnitude throughout the year. The fen can switch from being a
source to a sink if the water table changes over a small critical depth range. Our
measurements have implications for large scale wetland restoration plans in the eastern UK
and potential options for the management of methane emissions from wetlands. |
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