Effects of land use intensity on the full greenhouse gas balance in an Atlantic peat bog

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 tempera- ture, 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 warm- ing potential (GWP) by reducing GHG emissions. 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 fer- tilizer, cattle manure and 4-5 cuts per year); extensive grass- land (rewetted, no fertilizer or manure, up to 1 cutting per year); near-natural peat bog (almost no anthropogenic influ- ence). Daily and annual greenhouse gas exchange was es- timated 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 esti- mated by linear interpolation while NEE was modelled. Regarding GWP, the intensive grassland site emit- ted 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