Managing wet fen meadows for nature conservation leads to a moderate warming effect

Wet fen meadows are a traditional form of land use that is nowadays mainly preserved through nature conservation measures. Recent discussions suggest that this land use may also be considered as a form of paludiculture (that is, wet peatland use with the preservation of the peat body). However, the climate effect of this land use type is largely unknown. My presentation shows a complete two-year greenhouse gas (GHG) balance of two previously unexplored, long-term rewetted fens under a nature conservation management regime resulting from biweekly chamber measurements of GHG fluxes at two north-east German sites with acute sedge and at one site with creeping bentgrass from 2014 to 2016. Including harvest and dissolved carbon export, the three sites emitted between 10.4 and 16.3 t CO₂-eq ha^-1 yr^-1, with mean annual water levels between -10 and -19 cm. Emissions consisted mainly of CO₂ uptake and release and were influenced by harvest time and frequency as well as inundation periods during vegetation growth. In addition, CH₄ emissions contributed to the net GHG balance at two sites due to inundation in late summer 2014. N₂O emissions were of minor importance at all three sites. The presentation demonstrates that, depending on proper water management, nature conservation-managed fen meadows can have a similar climate effect as other fen paludicultures, with a GHG mitigation potential of between 15 and 20 t CO₂-eq ha^- 1 yr^-1 compared to drainage-based grassland use on fens.