title: Contrasting wetland CH4 emission responses to simulated glacial atmospheric CO2 in temperate bogs and fens.
abstract: Wetlands were the largest source of atmospheric methane (CH(4) ) during the Last Glacial Maximum (LGM), but the sensitivity of this source to exceptionally low atmospheric CO(2) concentration ([CO(2) ]) at the time has not been examined experimentally. We tested the hypothesis that LGM atmospheric [CO(2) ] reduced CH(4) emissions as a consequence of decreased photosynthate allocation to the rhizosphere. We exposed minerotrophic fen and ombrotrophic bog peatland mesocosms to simulated LGM (c. 200 ppm) or ambient (c. 400 ppm) [CO(2) ] over 21 months (n = 8 per treatment) and measured gaseous CH(4) flux, pore water dissolved CH(4) and volatile fatty acid (VFA; an indicator of plant carbon supply to the rhizosphere) concentrations. Cumulative CH(4) flux from fen mesocosms was suppressed by 29% (P < 0.05) and rhizosphere pore water [CH(4) ] by c. 50% (P < 0.01) in the LGM [CO(2) ], variables that remained unaffected in bog mesocosms. VFA analysis indicated that changes in plant root exudates were not the driving mechanism behind these results. Our data suggest that the LGM [CO(2) ] suppression of wetland CH(4) emissions is contingent on trophic status. The heterogeneous response may be attributable to differences in species assemblage that influence the dominant CH(4) production pathway, rhizosphere supplemented photosynthesis and CH(4) oxidation.
authors: Centre for Earth, Planetary, Space and Astronomical Research, The Open University, Milton Keynes MK7 6AA, UK.
authors: Carl P
authors: CP
authors: Boardman
authors: Centre for Earth, Planetary, Space and Astronomical Research, The Open University, Milton Keynes MK7 6AA, UK.
authors: Vincent
authors: V
authors: Gauci
authors: Centre for Earth, Planetary, Space and Astronomical Research, The Open University, Milton Keynes MK7 6AA, UK.
authors: Jonathan S
authors: JS
authors: Watson
authors: Centre for Earth, Planetary, Space and Astronomical Research, The Open University, Milton Keynes MK7 6AA, UK.
authors: Stephen
authors: S
authors: Blake
authors: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
authors: David J
authors: DJ
authors: Beerling
mesh_terms: D000838:Anions; D001272:Atmosphere / Q000737:chemistry*; D002245:Carbon Dioxide / Q000032:analysis*; D002412:Cations; D003198:Computer Simulation; D017753:Ecosystem; D005232:Fatty Acids, Volatile / Q000032:analysis; D046448:Ice Cover / Q000737:chemistry*; D008697:Methane / Q000032:analysis*; D016062:Porosity; D012621:Seasons; D013696:Temperature; D014867:Water / Q000737:chemistry; D053833:Wetlands
chemical_list: D000838:Anions; D002412:Cations; D005232:Fatty Acids, Volatile; D014867:Water; D002245:Carbon Dioxide; D008697:Methane