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| Titel |
Effects of free-air CO2 enrichment (FACE) and soil warming on CH4 emission from a rice paddy field: impact assessment and stoichiometric evaluation |
| VerfasserIn |
T. Tokida, T. Fumoto, W. Cheng, T. Matsunami, M. Adachi, N. Katayanagi, M. Matsushima, Y. Okawara, H. Nakamura, M. Okada, R. Sameshima, T. Hasegawa |
| 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 ; 7, no. 9 ; Nr. 7, no. 9 (2010-09-08), S.2639-2653 |
| Datensatznummer |
250004963
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| Publikation (Nr.) |
 copernicus.org/bg-7-2639-2010.pdf |
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| Zusammenfassung |
| Paddy fields are an important source of atmospheric CH4, the second
most important greenhouse gas. There is a strong concern that the increasing
atmospheric CO2 concentration ([CO2]) and global warming are
further stimulating CH4 emissions, but the magnitude of this
stimulation varies substantially by study, and few open-field evaluations
have been conducted. Here we report results obtained at a Japanese rice
free-air CO2 enrichment (FACE) site under water and soil temperature
elevation during two growing seasons. Our objectives were to evaluate the
effects of high [CO2] (ambient + 200 μmol mol−1) and elevated
soil temperature (+ 2 °C) on CH4 emissions under completely
open-field conditions. We found about 80% enhancement in total seasonal
emissions by the additive effects of FACE and warming, indicating a strong
positive feedback effect of global warming.
The enhancement in CH4 emission from the FACE-effect alone (+ 26%)
was statistically non-significant (P = 0.19). Nevertheless, observed positive correlations between
CH4 emissions and rice biomass agreed well with previous studies, suggesting that
higher photosynthesis led to greater rhizodeposition, which then acted as substrates for methanogenesis.
Soil warming
increased the emission by 44% (P < 0.001), which was equivalent to a
Q10 of 5.5. Increased rice biomass by warming could only partly explain
the enhanced CH4 emissions, but stoichiometric analysis of the electron
budget indicated that even a moderate enhancement in organic matter
decomposition due to soil warming can cause a large increase in CH4
production under conditions where Fe(III) reduction, which was little
affected by soil warming, dominates electron-accepting processes. At later
rice growth stages, advanced root senescence due to elevated temperature
probably provided more substrate for methanogenesis. Our stoichiometric
evaluation showed that in situ Fe reduction characteristics and root
turnover in response to elevated temperature should be understood to
correctly predict future CH4 emissions from paddy fields under a
changing climate. Challenges remain for determination of in situ
root-exudation rate and its response to FACE and warming. |
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