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| Titel |
Mimicking floodplain reconnection and disconnection using 15N mesocosm incubations |
| VerfasserIn |
N. Welti, E. Bondar-Kunze, M. Mair, P. Bonin, W. Wanek, G. Pinay, T. Hein |
| 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 ; 9, no. 11 ; Nr. 9, no. 11 (2012-11-05), S.4263-4278 |
| Datensatznummer |
250007374
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| Publikation (Nr.) |
 copernicus.org/bg-9-4263-2012.pdf |
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| Zusammenfassung |
| Floodplain restoration changes the nitrate delivery pattern and dissolved
organic matter pool in backwaters, though the effects these changes have are
not yet well known. We performed two mesocosm experiments on floodplain
sediments to quantify the nitrate metabolism in two types of floodplains.
Rates of denitrification, dissimilatory nitrate reduction to ammonium (DNRA)
and anammox were measured using 15N-NO3 tracer additions in
mesocosms of undisturbed floodplain sediments originating from (1) restored
and (2) disconnected sites in the Alluvial Zone National Park on the Danube
River downstream of Vienna, Austria. DNRA rates were an order of magnitude
lower than denitrification and neither rate was affected by changes in
nitrate delivery pattern or organic matter quality. Anammox was not detected
at any of the sites. Denitrification was out-competed by assimilation, which
was estimated to use up to 70% of the available nitrate. Overall,
denitrification was higher in the restored sites, with mean rates of
5.7 ± 2.8 mmol N m−2 h−1 compared to the disconnected site
(0.6 ± 0.5 mmol N m−2 h−1). In addition, ratios of
N2O : N2 were lower in the restored site indicating a more complete
denitrification. Nitrate addition had neither an effect on
denitrification, nor on the N2O : N2 ratio. However, DOM (dissolved organic matter) quality
significantly changed the N2O : N2 ratio in both sites.
Addition of riverine-derived organic matter lowered the N2O : N2
ratio in the disconnected site, whereas addition of floodplain-derived
organic matter increased the N2O : N2 ratio in the restored site.
These results demonstrate that increasing floodplains hydrological
connection to the main river channel increases nitrogen retention and
decreases nitrous oxide emissions. |
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