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Fluxes and 13C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought

Title data

Knorr, Klaus-Holger ; Glaser, Bruno ; Blodau, Christian:
Fluxes and 13C isotopic composition of dissolved carbon and pathways of methanogenesis in a fen soil exposed to experimental drought.
In: Biogeosciences. Vol. 5 (2008) . - pp. 1457-1473.
ISSN 1726-4189
DOI: https://doi.org/10.5194/bg-5-1457-2008

Abstract in another language

Peatlands contain a carbon stock of global concern and significantly contribute to the global methane burden. The impact of drought and rewetting on carbon cycling in peatland ecosystems is thus currently debated. We studied the impact of experimental drought and rewetting on intact monoliths from a temperate fen over a period of ~300 days, using a permanently wet treatment and two treatments undergoing drought for 50 days. In one of the mesocosms, vegetation had been removed. Net production of CH4 was calculated from mass balances in the peat and emission using static chamber measurements. Results were compared to 13C isotope budgets of CO2 and CH4 and energy yields of acetoclastic and hydrogenotrophic methanogenesis. Drought retarded methane production after rewetting for days to weeks and promoted methanotrophic activity. Based on isotope and flux budgets, aerobic soil respiration contributed 32–96% in the wet treatment and 86–99% in the other treatments. Drying and rewetting did not shift methanogenic pathways according to δ13C ratios of CH4 and CO2. Although δ13C ratios indicated a prevalence of hydrogenotrophic methanogenesis, free energies of this process were small and often positive on the horizon scale. This suggests that methane was produced very locally. Fresh plant-derived carbon input apparently supported respiration in the rhizosphere and sustained methanogenesis in the unsaturated zone, according to a 13C-CO2 labelling experiment. The study documents that drying and rewetting in a rich fen soil may have little effect on methanogenic pathways, but result in rapid shifts between methanogenesis and methanotrophy. Such shifts may be promoted by roots and soil heterogeneity, as hydrogenotrophic methanogenesis occurred locally even when conditions were not conducive for this process in the bulk peat.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER61920
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Chair Soil Physics
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Chair Hydrology
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Research Institutions > Research Units > Limnological Research Station
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Research Institutions
Research Institutions > Research Centres
Research Institutions > Research Units
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 15 May 2015 14:47
Last Modified: 15 May 2015 14:47
URI: https://eref.uni-bayreuth.de/id/eprint/13738