Abstract. This study compares the CH4 fluxes from two arctic wetland sites of different annual temperatures during 2004 to 2006. The PEATLAND-VU model was used to simulate the emissions. The CH4 module of PEATLAND-VU is based on the Walter-Heimann model. The first site is located in northeast Siberia, Indigirka lowlands, Kytalyk reserve (70° N, 147° E) in a continuous permafrost region with mean annual temperatures of –14.3°C. The other site is Stordalen mire in the eastern part of Lake Torneträsk (68° N, 19° E), ten kilometres east of Abisko, northern Sweden. It is located in a discontinuous permafrost region. Stordalen has a sub arctic climate with a mean annual temperature of –0.7°C. Model input consisted of observed temperature, precipitation and snow cover data. In all cases, modelled CH4 emissions show a direct correlation between variations in water table and soil temperature variations. The differences in CH4 emissions between the two sites are caused by different climate, hydrology, soil physical properties, vegetation type and NPP. For Kytalyk the simulated CH4 fluxes show similar trends during the growing season, having average values for 2004 to 2006 between 1.29–2.09 mg CH4 m−2 h−1. At Stordalen the simulated fluxes show a slightly lower average value for the same years (3.52 mg CH4 m−2 h−1) than the observed 4.7 mg CH4 m−2 h−1. The effect of the longer growing season at Stordalen is simulated correctly. Our study shows that modelling of arctic CH4 fluxes is improved by adding a relatively simple hydrological model that simulates the water table position from generic weather data. We conclude that CH4 fluxes at these sites are less sensitive to temperature variation than to water table variations. Furthermore, parameter uncertainty at site level in wetland CH4 process models is an important factor in large scale modelling of CH4 fluxes.

Our research investigates the spatial and temporal variability of methane (CH 4 ) emissions in two drained eutrophic peat areas (one intensively managed and the other less intensively managed) and the correlation between CH 4 emissions and soil temperature, air temperature, soil moisture content and water table. We stratified the land-5 scape into landscape elements that represent different conditions in terms of topography and therefore differ in moisture conditions. There was great spatial variability in the fluxes in both areas; the ditches and ditch edges (together 27% of the landscape) were methane hotspots whereas the dry fields had the smallest fluxes. In the intensively managed site the fluxes were significantly higher by comparison with the less 10 20 on groundwater level, soil moisture content, temperature, and grassland management (Blodau and Moore, 2003; Christensen et al., 2003; Hendriks et al., 2007; Hargreaves and Fowler, 1998; Pelletier et al., 2007; Van den Pol-Van Dasselaar et al., 1998a). CH 4 emissions are difficult to estimate because of their large spatial and temporal variability. Furthermore, there are two major challenges when upscaling: selecting the correct 25 ecosystem variables for the stratification and developing predictive relationships (Groffman et al. Abstract IntroductionConclusions References Tables tensively managed) are located in a polder in the west of the Netherlands (Coord. Abstract Introduction Conclusions ReferencesTables 20 abundant.The Oukoop experimental plots are situated on an intensive dairy farm. The management regime varies per year, but overall consists of mowing three times a year and manuring and fertilizing three times a year. The average C and N contents in the top 20 cm of the soil are 24% and 2.4%, respectively. Here too, Lolium perenne is the most 25 dominant species and Poa trivialis is co-dominant.

It is generally known that managed, drained peatlands act as carbon sources. In this study we examined how mitigation through the reduction of management and through rewetting may affect the greenhouse gas (GHG) emission and the carbon balance of intensively managed, drained, agricultural peatlands. Carbon and GHG balances were determined for three peatlands in the western part of the Netherlands from 2005 to 2008 by considering spatial and temporal variability of emissions (CO₂, CH₄ and N₂O). One area (Oukoop) is an intensively managed grass-on-peatland, including a dairy farm, with the ground water level at an average annual depth of 0.55 m below the soil surface. The second area (Stein) is an extensively managed grass-on-peatland, formerly intensively managed, with a dynamic ground water level at an average annual depth of 0.45 m below the soil surface. The third area is an (since 1998) rewetted former agricultural peatland (Horstermeer), close to Oukoop and Stein, with the average annual ground water level at a depth of 0.2 m below the soil surface. During the measurement campaigns we found that both agriculturally managed sites acted as carbon and GHG sources but the rewetted agricultural peatland acted as a carbon and GHG sink. The terrestrial GHG source strength was 1.4 kg CO₂-eq m⁻² yr⁻¹ for the intensively managed area and 1.0 kg CO₂-eq m⁻² yr⁻¹ for the extensively managed area; the unmanaged area acted as a GHG sink of 0.7 kg CO₂-eq m⁻² yr⁻¹. Water bodies contributed significantly to the terrestrial GHG balance because of a high release of CH₄ and the loss of DOC only played a minor role. Adding the farm-based CO₂ and CH₄ emissions increased the source strength for the managed sites to 2.7 kg CO₂-eq m⁻² yr⁻¹ for Oukoop and 2.1 kg CO₂-eq m⁻² yr⁻¹ for Stein. Shifting from intensively managed to extensively managed grass-on-peat reduced GHG emissions mainly because N₂O emission and farm-based CH₄ emissions decreased. Overall, this study suggests that managed peatlands are large sources of GHG and carbon, but, if appropriate measures are taken they can be turned back into GHG and carbon sinks within 15 yr of abandonment and rewetting

Abstract. Carbon dioxide and methane fluxes were measured at a tundra site near Chokurdakh, in the lowlands of the Indigirka river in north-east Siberia. This site is one of the few stations on Russian tundra and it is different from most other tundra flux stations in its continentality. A suite of methods was applied to determine the fluxes of NEE, GPP, Reco and methane, including eddy covariance, chambers and leaf cuvettes. Net carbon dioxide fluxes were unusually high, compared with other tundra sites, with NEE=–92 g C m−2 yr−1, which is composed of an Reco=+141 g C m−2 yr−1 and GPP=–232 g C m−2 yr−1. This large carbon dioxide sink may be explained by the continental climate, that is reflected in low winter soil temperatures (–14°C), reducing the respiration rates, and short, relatively warm summers, stimulating high photosynthesis rates. Interannual variability in GPP was dominated by the frequency of light limitation (Rg <200 W m−2), whereas Reco depends most directly on soil temperature and time in the growing season, which serves as a proxy of the combined effects of active layer depth, leaf area index, soil moisture and substrate availability. The methane flux, in units of global warming potential, was +28 g C-CO2e m−2 yr−1, so that the greenhouse gas balance was –64 g C-CO2e m−2 yr−1. Methane fluxes depended only slightly on soil temperature and were highly sensitive to hydrological conditions and vegetation composition.