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| Titel |
Nitrogen mineralization and gaseous nitrogen losses from waterlogged and drained organic soils in a black alder (Alnus glutinosa (L.) Gaertn.) forest |
| VerfasserIn |
T. Eickenscheidt, J. Heinichen, J. Augustin, A. Freibauer, M. Drösler |
| 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 ; 11, no. 11 ; Nr. 11, no. 11 (2014-06-05), S.2961-2976 |
| Datensatznummer |
250117447
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| Publikation (Nr.) |
 copernicus.org/bg-11-2961-2014.pdf |
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| Zusammenfassung |
| Black alder (Alnus glutinosa (L.) Gaertn.) forests on peat soils
have been reported to be hotspots for high nitrous oxide (N2O) losses.
High emissions may be attributed to alternating water tables of peatlands and
to the incorporation of high amounts of easily decomposable nitrogen (N) into
the ecosystem by symbiotic dinitrogen (N2)-fixation of alder trees. Our
study addressed the question to what extent drainage enhances the emissions
of N2O from black alder forests and how N turnover processes and
physical factors influence the production of N2O and total
denitrification. The study was conducted in a drained black alder forest with
variable groundwater tables at a southern German fen peatland. Fluxes of
N2O were measured using the closed chamber method at two drained sites
(D-1 and D-2) and one undrained site (U). Inorganic N contents and net N
mineralization rates (NNM) were determined. Additionally a laboratory
incubation experiment was carried out to investigate greenhouse gas and
N2 fluxes at different temperature and soil moisture conditions.
Significantly different inorganic N contents and NNM rates were observed,
which however did not result in significantly different N2O fluxes in the
field but did in the laboratory experiment. N2O fluxes measured were low
for all sites, with total annual emissions of 0.51 ± 0.07 (U),
0.97 ± 0.13 (D-1) and
0.93 ± 0.08 kg N2O–N ha−1 yr−1 (D-2). Only 37%
of the spatiotemporal variation in field N2O fluxes could be explained
by peat temperature and groundwater level, demonstrating the complex
interlinking of the controlling factors for N2O emissions. However,
temperature was one of the key variables of N2O fluxes in the incubation
experiment conducted. Increasing soil moisture content was found to enhance
total denitrification losses during the incubation experiment, whereas
N2O fluxes remained constant. At the undrained site, permanently high
groundwater level was found to prevent net nitrification, resulting in a
limitation of available nitrate (NO3−) and negligible gaseous N
losses. N2O flux rates that were up to four times higher were measured
in the incubation experiment. They reveal the potential of high N2O
losses under changing soil physical conditions at the drained alder sites.
The high net nitrification rates observed and high NO3− contents bear
the risk of considerable NO3− leaching at the drained sites. |
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