Status, future prospects, and management recommendations for alkaline fens in an agricultural landscape: A comprehensive survey

Due to agricultural intensification and cessation of traditional land use, alkaline fens of the Caricion davallianae alliance (EU-FFH 7230) are among the most endangered ecosystems in Europe. This study exhibits a vegetation analysis of these systems in Schleswig-Holstein (Northern Germany). We analyzed across three scales the effects of grazing and mowing on phytodiversity of core areas and recorded their adjacent vegetation to estimate the capability for habitat enlargement of fen species. Results revealed that species richness, evenness and number of endangered species varied insignificantly between mowing and grazing treatments, regardless of scale. The high proportion of fen species and Red-Book-listed species in core areas, along with a state-wide representation of only 2 ha of these vegetation types, underlines the need for further conservation measures. Floristic differences between grazed and mowed sites derived from the individual appearance of species within one treatment. Thus, to preserve the species pool of alkaline fens, both management strategies have to be considered. Moreover, as most small sedge reed species are low-productive and light-demanding, sufficient biomass removal of dominant tall-growing species is required. One cut per year in late summer, the traditional management, does not satisfy the requirements of target species, which is indicated by an increase of Phragmitetea species at larger plot sizes. Additionally, in grazed fens, vegetation adjacent to the core areas consisted mainly of more eutrophic wet grasslands, and, in mowed fens, mainly of reeds or woods. We recommend therefore several changes in current conservation measures that include an increase to two cuts per year in mowed fens, and stocking rates of at least 2 LU ha−1 (summer grazing) or 0.7 LU ha−1 (year-round grazing).