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| Titel |
Impact of long term flooding on hydrogeochemistry and dissolved organic matter quality |
| VerfasserIn |
Klaus-Holger Knorr, Christian Blodau, Sven Frei, Klaus Kasparbauer, Stefan Durejka, Jonas Schaper |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093417
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| Publikation (Nr.) |
 EGU/EGU2014-8111.pdf |
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| Zusammenfassung |
| Peatlands store significant amounts of carbon but also contribute to global methane
emissions. Large areas in the boreal and temperate zones are predicted to undergo
changes in climate and concomitant changes in hydrology, according to climate
change scenarios. Thus, it is crucial to understand the response of peatlands to
altered climatic and hydrological boundary conditions. Here we investigated the
response of a peatland to long term wetting, as especially in winter for large areas
wetter conditions have been predicted. We hypothesized that long term wetting
will change hydrological fluxes, probably nutrient inputs from the adjacent water
body, and thereby result in changes in vegetation and concomitant changes in peat
decomposability.
The Luther Marsh site in Ontario, Canada, that has been partly flooded since the 1950s
due to the construction of a reservoir. Water management in the reservoir flooded a large part
of the peatland and also causes seasonal flooding especially in winter and spring, but also
draining in summer. This leads to shifting hydrological flow patterns and vegetation
gradients. Therefore, this site may serve as a model system to understand the effect of long
term wetting. Hydrology was monitored by means of piezometers and pressure transducers
over one growing season over a transect of 7 sites from the reservoir to the inner, pristine part
of the bog. At the same sites, we obtained pore water chemistry data and dissolved
gases.
Surprisingly, partial flooding only partly affected the general hydrological regime of the
peatland and the general flow direction of groundwater was still out of the peatland into the
adjacent lake. On the other hand, wetting resulted in obvious changes in vegetation, increased
nutrient availability, and thus increased decomposition activity in the wetted part. This was
reflected more narrow CH4 to CO2 ratios in the pore water and higher concentrations and
calculated turnover rates. Advective transport removed decomposition end products
and introduced nutrient enriched reservoir water, as indicated by elevated pH and
increased concentrations in Ca and Mg. Interestingly, DOC quality as assessed by
fluorescence spectroscopy also gradually approached quality indices observed in the
reservoir and the effect of wetting obviously reached far into the seemingly intact
peatland.
This study demonstrated that partial flooding of a peatland significantly changes
vegetation and the nutritional status, resulting in a shift towards more CH4 production and
higher turnover rates. |
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