Soil Biology & Biochemistry 35 (2003) 535–547 www.elsevier.com/locate/soilbio
Micro-scale CO2 and CH4 dynamics in a peat soil during a water ??uctuation and sulfate pulse
Christian Blodau*, Tim R. Moore
Department of Geography and Centre for Climate and Global Change Research, McGill University, 805 Sherbrooke Street West, Montreal, Canada H3A 2K6 Received 10 October 2001; received in revised form 4 December 2002; accepted 11 December 2002
Abstract We investigated the response of CO2 and CH4 production to a water table ??uctuation and a SO22 pulse in a bog mesocosm. Net gas 4 production rates in the mesocosm were calculated from concentration data by diffusive mass-balances. Incubation experiments were used to quantify the effect of SO22 addition and the distribution of potential CO2 and CH4 production rates. Flooding of unsaturated peat resulted in 4 rapid depletion of O2 and complex patterns of net CH4, CO2, and H2S production. Methane production began locally and without a time lag at rates of 3 – 4 nmol cm23 d21 deeper in the peat. Similar rates were determined after a time lag of 10 – 60 days in the surface layers, whereas rates at lower depths declined. Net CO2 production was largest immediately after the water table position was altered (100 – 300 nmol cm23 d21) and declined to 250 – 50 nmol cm23 d21 after a few weeks. SO22 addition (500 mM) signi??cantly increased potential 4 CH4 production rates in the surface layer from an average of 132– 201 nmol cm23 d21 and reduced it below from an average of 418– 256 nmol cm23 d21. Our results suggest that deeper in the peat (40– 70 cm) under in situ conditions, methanogenic populations are less impaired by unsaturated conditions than in the surface layers, and that at these depths after ??ooding the substrate availability for CH4 and DIC production is signi??cantly enhanced. They also suggest that methanogenic and SO22-reducing activity were non-competitive in the 4 surface layer, which might explain contradictory ??ndings from ??eld studies. q 2003 Elsevier Science Ltd. All rights reserved.

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