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| Titel |
Trace gas fluxes of CO2, CH4 and N2O in a permanent grassland soil exposed to elevated CO2 in the Giessen FACE study |
| VerfasserIn |
M. Kaleem Abbasi, C. Müller |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 17 ; Nr. 11, no. 17 (2011-09-09), S.9333-9342 |
| Datensatznummer |
250010066
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| Publikation (Nr.) |
 copernicus.org/acp-11-9333-2011.pdf |
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| Zusammenfassung |
| Long-term field observations showed that N2O fluxes observed shortly
after N application were not significantly affected by elevated CO2 in
the Giessen Free Air Carbon dioxide Enrichment (FACE) study. To further
investigate this unexpected result a 15N tracer study was carried out
under controlled conditions where in parallel treatments either the
NH4+ pool (15NH4NO3) or the NO3− pool
(NH415NO3) was enriched with 15N. Fluxes of CO2,
CH4, and N2O as well as the 15N enrichment of the N2O
were measured. Denitrifying Enzyme Activity (DEA), total denitrification
(N2 + N2O) and N2-to-N2O ratios were quantified in
separate experiments. Over the 57 day incubation, N2O fluxes averaged
0.090 ng N2O-N g−1 h−1 under ambient and 0.083 ng N2O-N g−1 h−1 under elevated CO2 (not significantly
different). The N2O production processes were identified by a
two-source model. Results showed that N2O must have also been produced
by a third source – possibly related to organic N transformation – which
was stimulated by elevated CO2. Soil CO2 fluxes were approximately
20 % higher under elevated CO2 than soil from ambient but the
differences were not significant. CH4 oxidation rates were on average
−1.75 ng CH4-C g−1 h−1 in the elevated and
−1.17 ng CH4-C g−1 h−1 in the ambient indicating that elevated
CO2 increased the CH4 oxidation by 49 % compared to ambient
CO2 under controlled conditions. N fertilization increased CH4
oxidation by 3-fold in both CO2 treatments. CO2 did not have any
significant effect on DEA while total denitrification and
N2-to-N2O ratios increased by 36 and 33 %, respectively. The
results indicate that shortly after N application elevated CO2 must
have stimulated both the N2O production and reduction to N2 to
explain the increased N2-to-N2O ratio and at the same time explain
the non-responsiveness of the N2O emissions. Thus, the observed
variation of the CO2 effect on N2O emissions throughout the year
is possibly governed by the dynamics of the N2O reductase activity. |
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