54.4 - Bas-marais acides

Acidic fens

Typologie des habitats de Saint-Pierre-et-Miquelon

Descriptif anglais

Topogenous or soligenous valley, basin or spring mire systems fed by waters poor in bases. As in the rich fens, the water level is at or near the surface of the substratum and peat formation is infra-aquatic. The mire communities themselves, dominated by small sedges and brown mosses or sphagna, belong to the Caricetalia fuscae, but, in large fen systems, they are accompanied by acidocline wet grasslands (Molinietalia caeruleae), large sedge beds (Magnocaricion) and reed or related communities (Phragmition). Sphagnum hummocks (unit 51.11) form locally and transition mires (unit 54.5) or aquatic (unit 22.3), amphibian (unit 22.2) and spring (unit 54.1) communities colonize small depressions. Thus, codes from all the above categories are used in conjunction with the ones below to completely describe the fen. The subdivisions listed here are, in any case, understood to include, besides strict mire communities, their transitions to humid grasslands, and groupings phytosociologically affiliated with Molinion associations, but rich in species of the Caricion fuscae, provided they are integrated in a fen system (somewhat paralleling the Junco acutiflori-Caricetalia nigrae of Rameau et al., 1989). Acidic fen communities also occur on small surfaces or within mosaics in other ecosystems, in particular in typical humid grasslands (37), humid woodlands and thickets (44), decalcified dune slacks (unit 16.3) and spring systems (unit 54.1). Their presence can be indicated by codes from this unit used in conjunction with the relevant main codes. Characteristic species of acidic mire communities are Carex canescens, Carex echinata, Carex nigra, Eriophorum angustifolium, Eriophorum scheuchzeri, Scirpus cespitosus, Juncus filiformis, Agrostis canina, Viola palustris, Cardamine pratensis, Ranunculus flammula and the mosses Calliergon sarmentosum, Calliergon stramineum, Calliergon cuspidatum, Drepanocladus exannulatus, Drepanocladus fluitans, Sphagnum recurvum, Sphagnum auritum, Sphagnum cuspidatum, Sphagnum subsecundum, Sphagnum apiculatum, Sphagnum papillosum, Sphagnum russowii.

Correspondances phytosociologiques

Caricetalia fuscae: Caricion fuscae

Bibliographie

Devillers P., Devillers-Terschuren J. & Vander Linden C., 2001. PHYSIS Palaearctic Habitat Classification Database. Updated to 10 December 2001. Institut Royal des Sciences Naturelles, Bruxelles. (Source)

Duvigneaud, 1949; Braun-Blanquet, 1954, 1971a; Ellenberg, 1963, 1988; Berset, 1969; Schumacker and Froment, 1971; Parent, 1973; Horvat & al., 1974; Westhoff and den Held, 1975; Schumacker, 1976; Wattez, 1976; Schumacher, 1977; Brasseur & al., 1977; Guinochet and Vilmorin, 1978; Brasseur & al., 1978; Dierssen, 1978; Petermann and Seibert, 1979; Goodwillie, 1980; Ratcliffe, 1980; Sanda & al., 1980; Fernandez Prieto, 1983; Ruuhijärvi, 1983; Sjörs, 1983; Moravec & al., 1983; Botch and Masing, 1983; Matuszkiewicz, 1984; Nordiska ministerradet, 1984; Rivas-Martinez & al., 1984b; Bournérias, 1984; Ochsenbein, 1984a, 1984b; Gamisans, 1985, 1991; Diaz Gonzalez and Fernandez Prieto, 1987; Martinez Parras and Peinado Lorca, 1987; Rivas-Martinez & al., 1987; Martinez Parras & al., 1987; Rameau & al., 1989; Salomez, 1990; Succow and Jeschke, 1990; Oberdorfer, 1990; Elias & al., 1991; Korotkov & al., 1991; Coldea, 1991; Rodwell, 1991b: 22-24; Steiner, 1992; Oberdorfer, 1992a; Pott, 1992; Julve, 1993; Påhlsson, 1994: 211, 216; Pakarinen, 1995; Schubert & al., 1995; Ilijanic, 1996: 108; Hoda & al., 1998: 7.