Spatial distribution of microbial methane production pathways in temperate zone wetland soils: Stable carbon and hydrogen isotope evidence
The identity and distribution of substrates that support CH 4 production in wetlands is poorly known at present. Organic compounds are the primary methanogenic precursor at all depths within anoxic wetland soils; however, the distribution of microbial processes by which these compounds are ultimatel...
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Published in | Geochimica et cosmochimica acta Vol. 61; no. 4; pp. 745 - 753 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Elsevier Ltd
01.02.1997
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Subjects | |
Online Access | Get full text |
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Summary: | The identity and distribution of substrates that support CH
4 production in wetlands is poorly known at present. Organic compounds are the primary methanogenic precursor at all depths within anoxic wetland soils; however, the distribution of microbial processes by which these compounds are ultimately converted to CH
4 is uncertain. Based on stable isotope measurements of CH
4 and ΣCO
2 extracted from soil porewaters in two temperate zone wetlands, we present evidence that a systematic spatial distribution of microbial methanogenic pathways can exist in certain anoxic, organic-rich soils. CH
4 production by the acetate fermentation pathway is favored in the shallow subsurface, while methanogenesis from the reduction of CO
2 with H
2 becomes more predominant in older, less reactive peat at depth. This distribution can account for many of the reported CH
4 emission characteristics of wetlands, in particular, their sensitivity to changes in primary productivity, temperature, and hydrology. These factors play an important role in controlling the short-term supply of labile substrates to fermentive methanogens in the shallow subsurface where the most intense CH
4 production occurs. Predominance of the CO
2-reduction pathway at depth may help to explain reports of CH
4 with a semifossil age in lower peat layers. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0016-7037 1872-9533 |
DOI: | 10.1016/S0016-7037(96)00368-7 |