JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Wiley-Blackwell is collaborating with JSTOR to digitize, preserve and extend access to Journal of Biogeography.Abstract. Greenhouse gas fluxes (CH4, N20 and C02) at a managed Finnish peat soil site were compared with those in a virgin fen in 1991 and 1992. The field site was drained about 60 years ago, and as it was used for pasturing and fodder production, the CH4 released by the cattle was estimated on the basis of data in the literature. The annual budgets of the gases were estimated and their GWP values calculated to assess the climatic impact of the current agricultural activity. Methane emission from the field site, 1 kg CH4-C ha-1 yr-1, was low, compared with that from the natural fen site, 260 kg CH4-C ha-1 yr-1. Annual N20 emission at the field site was 8 and 9 kg N20-N ha -1 yr -1 in 1991 and 1992, respectively. Summer N20 emission in 1992 from vegetationless soil was five times higher than that from actual grassland. The N20

Climate policies encourage the search for greenhouse gas (GHG) mitigation options in all economic sectors and peatland rewetting is one of the most efficient mitigation measures in agriculture and land use. The benefits shown in the national GHG inventories, however, depend not only on the actual mitigation actions on the ground but also how well the effects can be reported. Currently there are no specific emission factors for reporting GHG emissions from rewetted agricultural soils as the current emission factors are aggregated for several pre-rewetting land use types. Also, rewetting can aim at either restoration or different forms of paludiculture which may differ in their GHG profile and thus demand disaggregated emission factors. We compiled the current knowledge on GHG emissions on sites where rewetting has occurred on former agricultural peatland in temperate or boreal climate zones. The recent data suggest that on average the current emission factors for rewetting nutrient-rich sites published by the Intergovernmental Panel for Climate Change (IPCC) provide a good estimate for reporting emissions from rewetting in the temperate zone. However, the total GHG balances differed widely in restoration, Sphagnum farming and production of emergent plants in paludiculture and it is evident that disaggregated emission factors will be needed to improve the accuracy of reporting the effects of mitigation measures in the GHG inventories.

Using aerobic soil slurry technique nitrification and nitrous oxide production were studied in samples from a pine site in Western Finland. The site received atmospheric ammonium deposition of 7–33 kg N ha−1 a−1 from a mink farm. The experiments with soil slurries showed that the nitrification potential in the litter layer was higher at pH 6 than at pH 4. However, the nitrification potentials in the samples from the organic and mineral horizons at pH 6 and 4 were almost equal. Also N2O was produced at a higher rate at pH 6 than at pH 4 in slurries of the litter layer samples. The reverse was true for samples from the organic and mineral horizons. The highest N2O production and nitrification rates were measured in the suspensions of litter layer samples. Nitrification activity in field‐moist soil samples was lower than the activity in the slurries indicating that the availability of ammonium limited nitrification in these soils. Acetylene (2.5 kPa) retarded nitrification activity (70‐–100%) and N2O production (40 – 90%) in soil slurries. Acetylene inhibited the N2O production by 40–60% during the first 3 days after its addition to field‐moist samples incubated in aerobic atmosphere. After 3 days the inhibition became much lower (4–5%). The results indicate that, in soil profiles of boreal coniferous forests receiving ammonium deposition, chemolithotrophic nitrification may have importance in the N2O production, and that changes in soil pH affect differently nitrification as well as N2O production in litter and deeper soil layers.

No abstract

No abstract