Boreal rich fen vegetation formerly used for haymaking

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In the present study, we describe the variation in rich fen (brown moss‐dominated) vegetation of boreal uplands in Norway, based on studies in two nature reserves representing an oceanic and a more continental area. The vegetation description included 134 sample plots and 200 taxa, using TWINSPAN classification and DCA ordination. The main aims were to describe the rich fen vegetation used for traditional haymaking, to find important ecological gradients and to compare the fen vegetation to the main European classification systems. We classified the fen vegetation into six plant communities. Rich (including extremely rich) fen vegetation of lawns and open margins were most common, representing the alliances Caricion atrofuscae, including alpine/continental species like Equisetum variegatum and Pedicularis oederi and Schoenion ferruginei (Caricion davallianae), including lowland/oceanic species like Drosera longifolia and Narthecium ossifragum. A majority of the constant species were in common for the two alliances, e.g. Thalictrum alpinum, Trichophorum cespitosum, Campylium stellatum and Gymnocolea borealis. The lawn communities included 30–38 species per plot (12.5 m2). We classified the flat fens with carpet communities dominated by Scorpidium cossonii and S. scorpioides to the alliances Stygio–Caricion limosae and Caricion lasiocarpae. The carpets contained ca 30 species per plot. Shrub‐dominated fen margin represents Sphagno–Tomentypnion, with the highest species number, more than 50 species per plot, including Molinia caerulea as a constant and abundant species, and a large number of herbs as constants. The plots of the margin community were in an overgrowing process, invaded by shrubs and wet grassland species. The peak in floristic diversity in abandoned margin communities fits well with both the humped‐back model of species richness and the intermediate disturbance hypothesis.