Wintertime Greenhouse Gas Fluxes in Hemiboreal Drained Peatlands

The aim of this study is to estimate wintertime emissions of greenhouse gases CO2, N2O and CH(4)in two abandoned peat extraction areas (APEA), Ess-soo and Laiuse, and in two Oxalis site-type drained peatland forests (DPF) on nitrogen-rich sapric histosol, a Norway spruce and a Downy birch forest, located in eastern Estonia. According to the long-term study using a closed chamber method, the APEAs emitted less CO(2)and N2O, and more CH(4)than the DPFs. Across the study sites, CO(2)flux correlated positively with soil, ground and air temperatures. Continuous snow depth > 5 cm did not influence CO2, but at no snow or a thin snow layer the fluxes varied on a large scale (from -1.1 to 106 mg C m(-2)h(-1)). In all sites, the highest N2O fluxes were observed at a water table depth of -30 to -40 cm. CH(4)was consumed in the DPFs and was always emitted from the APEAs, whereas the highest flux appeared at a water table >20 cm above the surface. Considering the global warming potential (GWP) of the greenhouse gas emissions from the DPFs in the wintertime, the flux of N2O was the main component of warming, showing 3-6 times higher radiative forcing values than that of CO(2)flux, while the role of CH(4)was unimportant. In the APEAs, CO(2)and CH(4)made up almost equal parts, whereas the impact of N2O on GWP was minor.