Vegetation groups and habitats of neutro-basophilous fens in the Cantabro- Pyrenaean mountains

Neutro-basophilous fens are among the most species-rich and threatened wetlands in Europe. Because of their ecological and floristic variability, vegetation of these habitats may be subject to classification inconsistencies. Here we use a vegetation database of Cantabro-Pyrenean fens to analyze the main vegetation groups related to these fens and their relationship with the European habitat types and phytosociological classification. We selected 295 vegetation relevés from the study area according to the presence of four calcicole specialists (Carex lepidocarpa, C. davalliana, C. frigida and Eriophorum latifolium) and geographical stratification. We classified the relevés using cover data of vascular plants, modified TWINSPAN analysis and classification crispness. We analyzed the vegetation groups according to their geographical distribution, variation in altitude and slope, and similarity of species composition using gradient analysis (DCA). We finally established five major vegetation groups: (i) Pyrenean calcareous spring fens related to high mountain streamsides, including Caricion davallianae communities with Carex frigida and relict plant communities of the Caricion maritimae alliance; (ii) Cantabrian calcareous springs with the endemic Centaurium somedanum and few fen species, which should be better assigned to tufa-forming springs; (iii) Pyreneo-Cantabrian calcareous fen grasslands, which could be included in alkaline fens or Molinietalia wet grasslands; (iv) Pyreneo-Cantabrian calcareous fens, possibly related to limestone bedrocks of Cantabrian Range and Western Pyrenees; and (v) Pyrenean neutro-basophilous fens, which seem to be part of extremely rich fens distributed on non-limestone substrates of Central and Eastern Pyrenees.