HR: 09:15h
AN: B41F-05    [Abstracts]
TI: Below-ground C Turnover in a Northern Ombrotrophic Bog
AU: * Blodau, C
EM: christian.blodau@uni-bayreuth.de
AF: Limnological Research Station, University of Bayreuth, Unisersitaetsstrasse 30, Bayreuth, 95440 Germany
AU: Heitmann, T
EM:
AF: Limnological Research Station, University of Bayreuth, Unisersitaetsstrasse 30, Bayreuth, 95440 Germany
AU: Lafleur, P
EM:
AF: Department of Geography, Trent University, 1600 West Bank Drive, Peterborough, K9J7B8 Canada
AU: Tim, M R
EM:
AF: Department of Geography, McGill University, 805 Sherbrooke Street West, Montreal, Qc, H3A 2K6 Canada
AU: Heather, S
EM:
AF: Department of Geography, McGill University, 805 Sherbrooke Street West, Montreal, Qc, H3A 2K6 Canada
AU: Roulet, N T
EM:
AF: Department of Geography, McGill University, 805 Sherbrooke Street West, Montreal, Qc, H3A 2K6 Canada
AB: We lack estimates of the in situ production of dissolved C (C) and the contribution of vascular plants to below-water table production of dissolved C in peatlands, their environmental controls and relationship to the overall C budget. To address this gap, we measured fluxes of CO2 and CH4 from static chambers and in situ incubation experiments, recorded peat temperatures and water tables, time series of dissolved C pore water concentrations, and conducted a plant removal experiment at the ombrotrophic Mer Bleue peatland in Ontario, Canada, in 2003 and 2004. In situ production rates below the water table were estimated using pseudo steady-state diffusive pore water modelling. Concentrations of 0.1-2.0 mmol L-1 (DIC), 0 to 0.6 mmol L-1 (CH4) < 0.005 to 0.15 mmol L-1 (acetate, propionate, sulfate) and 30-120 mg L-1 DOC were recorded. CO2 fluxes averaged 58 mmol m-2 d-1 and were linearly related to temperature (flux (CO2) = 4.9 x T -23.7 [mmol m-2 d-1] [?°C]; R2 = 0.76), as were in situ rates of aerobic C mineralization (Q10= 5.0-6.1; R2 = 0.52-0.86). CH4 fluxes ranged from 0 to 2.7 mmol m-2 d-1 and peaked after a rapid water table rise of about 15 cm. CH4 production accounted on average for only 17 % of the estimated CO2 production in the saturated zone. Depletion of sulfate in 2004 did not result in increased relative CH4 production rates. Emissions were higher than diffusive fluxes, suggesting ebullition from larger depths as a main emission mechanism. CO2 production in the saturated zone averaged 1 mmol m-2 d-1 and might have reached 7mmol m-2 d-1 in the summer of 2004, including change in storage. It amounted, on average, to < 2% of the total CO2 flux. Removal of above-ground shrub biomass further reduced CO2 and CH4 production in the saturated zone by an estimated 30 to 50 % compared to control plots. Based on the small contribution of the saturated zone, oxygen deficiency apparently efficiently impeded the remineralization of plant biomass, highlighting the importance of water table levels as a control on autotrophic respiration.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: Fall Meeting 2005