Soil greenhouse gas emissions from afforested organic soil croplands and cutaway peatlands

The effects of land-use and land-use change on soil greenhouse gas (GHG) fluxes are of concern due to Kyoto Protocol requirements. To quantify the soil GHG-fluxes of afforested organic soils in Finland, chamber measurements of soil CO2, CH4 and N2O fluxes were made during the years 2002 to 2005 on twelve organic soil cropland and six cutaway peatland sites afforested 9 to 35 years ago. The annual soil CO2 effluxes were statistically modelled using soil temperature as the driving variable and the annual CH4 and N2O fluxes were estimated using the average fluxes during the measurement period. Soil CO2 effluxes on afforested organic soil croplands varied from 207 to 539 g CO2-C m–2 a–1 and on cutaway peatlands from 276 to 479 g CO2-C m–2 a–1. Both the afforested organic soil cropland and cutaway peatland sites acted mainly as small sinks for CH4; the annual flux ranged from –0.32 to 0.61 g CH4-C m–2. Afforested organic croplands emitted more N2O (from 0.1 to over 3.0 g N2O-N m–2 a–1) than cutaway peatland sites (from 0.01 to 0.48 g N2O-N m–2 a–1). Due to the decrease in soil CO2 efflux, and no change in CH4 and N2O fluxes, afforestation of organic croplands appears to decrease the greenhouse impact of these lands.