Keywords: Peatlands; Carbon dioxide; Methane; Sulfate; Pore water
1. Introduction Northern peatlands function as long term sinks for atmospheric carbon dioxide (CO2) (Gorham, 1991; Botch et al., 1995) and as sources of atmospheric methane (CH4) (Barlett and Harriss, 1993; Bubier et al., 1993, 1995). About 5 –10% of the global CH4 emissions to the atmosphere have been attributed to peatlands (Fung et al., 1991). Due to the important role of peatlands in the global carbon cycle their response to environmental change is currently investigated. Recent observations suggest for example that CO2 may be net released due to changes in environmental conditions, such as drought and permafrost melting (Oechel et al., 1993; Moore et al., 1998; Grif??s et al., 2000; Turetzky et al., 2002). The production of CO2 and CH4 depends on the microbial activity in the peat, the soil temperature, plant
* Corresponding author. Present address: Limnological Research Station, University of Bayreuth, D-95444 Bayreuth, Germany. Tel.: ?? 49-92155223; fax: ?? 49-921-552366. E-mail address: christian.blodau@uni-bayreuth.de (C. Blodau).
community structure, the chemical characteristics of the peat, and the position of redox boundaries associated with the water table (Bubier et al., 1993, 1995; Whiting and Chanton, 1993; Yavitt et al., 1997). Both CO2 and CH4 production rates are controlled by the availability of oxygen in the peat, which is in??uenced by the position of the water table. Strictly anaerobic conditions are a prerequisite for CH4 production and generally reduce CO2 production rates from peat (Moore and Dalva, 1993). Methane production and emission might also be in??uenced by the reduction of SO22 (Dise and Verry, 2001; Nedwell and Watson, 1995; 4 Watson and Nedwell, 1998; Wieder et al., 1990) because SO22 reducers can compete with methanogens for organic 4 substrates and H2 (Kristjanson et al., 1982; Lovley and Klug, 1983). SO22 availability in peatlands is in??uenced by 4 atmospheric input and by the reoxidation of reduced inorganic organic sulfur compounds during water table ??uctuations (Bayley et al., 1986; Devito and Hill, 1999; Shannon and White, 1996). Carbon dioxide and CH4 production rates in peatlands are therefore affected by the seasonal water table pattern, typically at its lowest level

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