A contribution to the revision of acid fen-land communities of temperate western Europe
[Contribution à une révision des bas-marais acides d’Europe tempérée occidentale]
Thébaud, Gilles; Roux, Camille; Delcoigne, Arnaud; Pétel, Gilles
99 acid fen-land communities from different European geographical origins, set up from 2418 relevés, have been analysed and are compared in a first synoptic table. Eight of these come from recent observations in the french Massif Central. This sampling has been treated by cluster analysis and detrended correspondence analysis (DCA). Our results show that vegetation is mostly segregated according to nutrient availability and the altituderelated temperature gradient. Oxygenation of the groundwater and mineral basis content also appear to be discriminating variables, although their relative importance is low. Endogenous dynamic succession, linked to terrestrialization, was also found to be involved. 19 associations have finally been retained and are presented in an overall synthetic table. We suggest 15 of them should be included in Caricion fuscae Koch 1926 em. Klika 1934. Three suballiances can be distinguished: Ranunculo flammulae-Caricenion fuscae Passarge 1964 (mesotrophytic communities from plain and mountain belt); Sphagno-Caricenion curtae Passarge 1964 (oligotrophytic and oligomesotrophytic communities from mountain belt), Carici nigrae-Trichophorenion cespitosi suball. nov. (subalpine oligotrophytic and acidiphytic or neutrophytic communities). Contacts and relations with Caricetalia davallianae and Juncion acutiflori are underlined and discussed. Caricetum nigrae Braun 1915, a central association of the alliance and included very heterogenous vegetation, is redefined with greater precision. Moreover, two new associations from the French Massif Central are described. The other syntaxa, resulting from previous ones, are here restored, amended, typified and updated, according to standard rules of phytosociological nomenclature.