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| Titel |
Pathway of CH4 production, fraction of CH4 oxidized, and 13C isotope fractionation in a straw-incorporated rice field |
| VerfasserIn |
G. B. Zhang, Y. Ji, J. Ma, G. Liu, H. Xu, K. Yagi |
| 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 ; 10, no. 5 ; Nr. 10, no. 5 (2013-05-22), S.3375-3389 |
| Datensatznummer |
250018257
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| Publikation (Nr.) |
 copernicus.org/bg-10-3375-2013.pdf |
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| Zusammenfassung |
| Straw incorporation generally increases CH4 emission from rice fields,
but its effects on the mechanism of CH4 emission, especially on the
pathway of CH4 production and the fraction of CH4 oxidized, are not
well known. To investigate the methanogenic pathway, the fraction of CH4
oxidized as well as the stable carbon isotope fractionation during the
oxidation and transport of CH4 as affected by straw incorporation,
observations were conducted of production and oxidation of CH4 in paddy
soil and rice roots and δ13C-values of produced CH4 and
CO2, and emitted CH4 in incubation and field experiments. Straw
incorporation significantly enhanced CH4 production potentials of the
paddy soil and rice roots. However, it increased the relative contribution of
acetate to total CH4 production (Fac) in the paddy soil by
∼10–30%, but decreased Fac-value of the rice roots
by ∼5–20%. Compared with rice roots, paddy soil was more
important in acetoclastic methanogenesis, with Fac-value being
6–30% higher. Straw incorporation highly decreased the fraction of
CH4 oxidized (Fox) by 41–71%, probably attributed to
the fact that it increased CH4 oxidation potential whereas CH4
production potential was increased to a larger extent. There was little
CH4 formed during aerobic incubation, and the produced CH4 was more
13C-enriched relative to that of anaerobic incubation. Assuming
δ13C-values of CH4 aerobically produced in paddy soil to be
the δ13C-values of residual CH4 after being oxidized,
(Fox-value still appeared to be 45–68% lower when straw was
incorporated. Oxidation fractionation factor (αox) was
higher with straw incorporation (1.033) than without straw incorporation
(1.025). The δ13C-values of CH4 emitted after cutting of the
plants (−50 to −43‰) were more positive than those of before
(−58 to −55‰), suggesting a transport fractionation factor
(ϵtransport) was −8.0‰ with straw
incorporation and −12.0‰ without straw incorporation. Causes of
this difference may be related to the diffusion process in transport as
affected by growth of rice plants and pressure in the rhizosphere. The
experiment shows that straw incorporation increases the contribution of
acetate to total methanogenesis in paddy soil but decreases it on rice roots,
and it significantly decreases the fraction of CH4 oxidized in the
field and expands oxidation fractionation while reducing transport
fractionation. |
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