Methane fluxes and nitrogen dynamics from a drained fenland peat

 Rates of methane uptake were measured in incubation studies with intact cores from adjacent fenland peats that have been under arable management and woodland management for at least the past 30 years. On two separate occasions the woodland peat showed greater rates of uptake than the arable peat. These rates ranged from 23.1 to 223.3 μg CH₄ m^–2 day^–1 for the woodland peat and from 29.6 to 157.6 μg CH₄ m^–2 day^–1 for the arable peat. When the peats were artificially flooded there was a decrease in the rate of methane oxidation, but neither site showed any net efflux of methane. ¹⁵N isotopic dilution was used to characterise nitrogen cycling within the two peats. Both showed similar rates of gross nitrogen mineralisation (3.58 mg N kg^–1 day^–1, arable peat; 3.54 N kg^–1 day^–1, woodland peat) and ammonium consumption (4.19 arable peat and 4.70 mg N kg^–1 day^–1 woodland peat). There were significant differences in their inorganic ammonium and nitrate pool sizes, and the rate of gross nitrification was significantly higher in the woodland peat (4.90 mg N kg^–1 day^–1) compared to the arable peat (1.90 mg N kg^–1 day^–1). These results are discussed in the light of high atmospheric nitrogen deposition. Received: 1 December 1997