Drainage has turned peatlands from a carbon sink into one of the world's largest greenhouse gas (GHG) sources from cultivated soils. We analyzed a unique data set (12 peatlands, 48 sites and 122 annual budgets) of mainly unpublished GHG emissions from grasslands on bog and fen peat as well as other soils rich in soil organic carbon (SOC) in Germany. Emissions and environmental variables were measured with identical methods. Site-averaged GHG budgets were surprisingly variable (29.2 ± 17.4 t CO -eq. ha yr ) and partially higher than all published data and the IPCC default emission factors for GHG inventories. Generally, CO (27.7 ± 17.3 t CO ha yr ) dominated the GHG budget. Nitrous oxide (2.3 ± 2.4 kg N O-N ha yr ) and methane emissions (30.8 ± 69.8 kg CH -C ha yr ) were lower than expected except for CH emissions from nutrient-poor acidic sites. At single peatlands, CO emissions clearly increased with deeper mean water table depth (WTD), but there was no general dependency of CO on WTD for the complete data set. Thus, regionalization of CO emissions by WTD only will remain uncertain. WTD dynamics explained some of the differences between peatlands as sites which became very dry during summer showed lower emissions. We introduced the aerated nitrogen stock (N ) as a variable combining soil nitrogen stocks with WTD. CO increased with N across peatlands. Soils with comparatively low SOC concentrations showed as high CO emissions as true peat soils because N was similar. N O emissions were controlled by the WTD dynamics and the nitrogen content of the topsoil. CH emissions can be well described by WTD and ponding duration during summer. Our results can help both to improve GHG emission reporting and to prioritize and plan emission reduction measures for peat and similar soils at different scales.

Wetlands can either be net sinks or net sources of greenhouse gases (GHGs), depending on the mean annual water level and other factors like average annual temperature, vegetation development, and land use. Whereas drained and agriculturally used peatlands tend to be carbon dioxide (CO₂) and nitrous oxide (N₂O) sources but methane (CH₄) sinks, restored (i.e. rewetted) peatlands rather incorporate CO₂, tend to be N₂O neutral and release CH₄. One of the aims of peatland restoration is to decrease their global warming potential (GWP) by reducing GHG emissions. <br><br> We estimated the greenhouse gas exchange of a peat bog restoration sequence over a period of 2 yr (1 July 2007–30 June 2009) in an Atlantic raised bog in northwest Germany. We set up three study sites representing different land use intensities: intensive grassland (deeply drained, mineral fertilizer, cattle manure and 4–5 cuts per year); extensive grassland (rewetted, no fertilizer or manure, up to 1 cutting per year); near-natural peat bog (almost no anthropogenic influence). Daily and annual greenhouse gas exchange was estimated based on closed-chamber measurements. CH₄ and N₂O fluxes were recorded bi-weekly, and net ecosystem exchange (NEE) measurements were carried out every 3–4 weeks. Annual sums of CH₄ and N₂O fluxes were estimated by linear interpolation while NEE was modelled. <br><br> Regarding GWP, the intensive grassland site emitted 564 ± 255 g CO₂–C equivalents m⁻² yr⁻¹ and 850 ± 238 g CO₂–C equivalents m⁻² yr⁻¹ in the first (2007/2008) and the second (2008/2009) measuring year, respectively. The GWP of the extensive grassland amounted to −129 ± 231 g CO₂–C equivalents m⁻² yr⁻¹ and 94 ± 200 g CO₂–C equivalents m⁻² yr⁻¹, while it added up to 45 ± 117 g CO₂–C equivalents m⁻² yr⁻¹ and −101 ± 93 g CO₂–C equivalents m⁻² yr⁻¹ in 2007/08 and 2008/09 for the near-natural site. In contrast, in calendar year 2008 GWP aggregated to 441 ± 201 g CO₂–C equivalents m⁻² yr⁻¹, 14 ± 162 g CO₂–C equivalents m⁻² yr⁻¹ and 31 ± 75 g CO₂–C equivalents m⁻² yr⁻¹ for the intensive grassland, extensive grassland, and near-natural site, respectively. <br><br> Despite inter-annual variability, rew...

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The assessment of emission factors for many peatlands is difficult, and reliable data on the exchange of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) between soil and atmosphere of these areas is particularly scarce. Reasons for this are the multitude of soil and land use combinations that control greenhouse gas exchange and the high effort associated with data acquisition. <br><br> We investigated the greenhouse gas exchange of a peat bog restoration sequence over a period of 2 yr (July 2007–June 2009) in an Atlantic raised bog in Northwest Germany. We set up three sites representing different land use intensities: intensive grassland (mineral fertilizer, cattle manure and 4–5 cuts per year); extensive grassland (no fertilizer or manure, maximal 1 cutting per year); near-natural peat bog (almost no anthropogenic influence). <br><br> We obtained seasonal and annual estimates of greenhouse gas exchange based on closed chamber measurements. CH₄ and N₂O fluxes were recorded bi-weekly, CO₂ NEE determinations were carried out 3–4 weekly. To get annual sums the CH₄ and N₂O fluxes were interpolated linearly while NEE was modelled. The intensive grassland site emitted 548 &plusmn; 169 g CO₂-C m^&minus;2 in the first and 817 &plusmn; 140 g CO₂-C m^&minus;2 in the second year. The extensive grassland site showed a slight uptake in the first year (&minus;148 &plusmn; 143 g CO₂-C m^&minus;2), and a small emission of 88 &plusmn; 146 g CO₂-C m^&minus;2 in the second year. In contrast to these agriculturally used sites, the near-natural site took up CO₂-C in both years (&minus;8 &plusmn; 68 g CO₂-C m^&minus;2 and &minus;127 &plusmn; 53 g CO₂-C m^&minus;2). Under consideration of N₂O and CH₄ exchange, the total average greenhouse warming potential (GWP) for 2008 amounts to 441 &plusmn; 157 g m^&minus;2, 14 &plusmn; 152 g m^&minus;2 and 31 &plusmn; 68 g m^&minus;2 CO₂-C-equivalent for the intensive grassland, the extensive grassland and the near-natural site, respectively. <br><br> Despite inter-annual variability, rewetting contributes considerably to mitigating GHG emission from formerly drained peatlands. Already extensively used grassland on moderately drained peat approaches the carbon sequestration potential of near-natural sites, albeit it may oscillate bet...

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