Seasonal variation in CH emissions and production and oxidation potentials at microsites on an oligotrophic pine fen.

Temporal and spatial variation in CH emissions was studied at hummock, Eriophorum lawn, flark and Carex lawn microsites in an oligotrophic pine fen over the growing season using a static chamber method, and CH production and oxidation potentials in peat profiles from hummock and flark were determined in laboratory incubation experiments. Emissions were lowest in the hummocks, and decreased with increasing hummock height, while in the lawns and flarks they increased with increasing sedge cover. Statistical response functions with water table and peat temperature as independent variables were calculated in order to reconstruct seasonal CH emissions by reference to the time series for peat temperature and water table specific to each microsite type. Mean CH emissions in the whole area in the snow-free period of 1993, weighted in terms of the proportions of the microsites, were 1.7 mol CH m. Potential CH production and oxidation rates were very low in the hummocks rising above the groundwater table, but were relatively similar when expressed per dry weight of peat both in the hummocks and flarks below the water table. The CH production potential increased in autumn at both microsites and CH oxidation potential seemed to decrease. The decrease in temperature in autumn certainly reduced in situ decomposition processes, possibly leaving unused substrates in the peat, which would explain the increase in CH production potential.