2. Données et outils
  3. Rechercher un habitat
  4. 54.5 - Tourbières de transition
  5. Description
54.5 - Tourbières de transition

Transition mires
54.4 - Bas-marais acides
54.6 - Communautés à Rhynchospora alba et communautés des fonds boueux

Typologie des habitats de Saint-Pierre-et-Miquelon

Descriptif anglais

Wetlands mostly or largely occupied by peat-forming plant communities developed at the surface of oligotrophic or meso-oligotrophic water reaching a level above, sometimes well above, the substratum, providing little or no mineral or nutrient supply. Their characteristics are thus intermediate between those of soligenous and topogenous mires and those of strictly ombrogenous bogs. In large systems, the most prominent communities are swaying swards, floating carpets or quaking mires formed by medium sized or small sedges, associated with sphagna or brown mosses. They are accompanied by aquatic and amphibious communities (units 22.3, 22.4) and by formations transitional to these on the one hand, to fens (units 54.2, 54.4), bogs (unit 51.1) or humid grasslands (37) on the other; sphagnum buttes (units 51.11), in particular, are often an important feature. Tall sedge and reed communities (53), willow and alder carrs (44) invade part of the peatland. Transition mires form mostly as colonists of oligotrophic ponds and lakes, large bog pools or laggs. Their distribution is mostly northern peri-Alpine, peri-Hercynian and northern European. Outside of transition mire systems, their communities can be found in bog hollows (unit 51.12), in blanket bogs (52), in depressions of rich or acidic fens (units 54.2, 54.4), in spring systems (unit 54.1), in humid heaths (unit 31.1) and a few other habitats. Characteristic species include Eriophorum gracile, Carex lasiocarpa, Carex chordorrhiza, Carex limosa, Scheuchzeria palustris, Hammarbya paludosa, Liparis loeselii, Calla palustris. Transition mires are an extremely important refuge of specialized, threatened species of both plants and animals; their richness and diversity in remarkable invertebrates, dragonflies among others, is even greater than that of most other mire ecosystems.

Correspondances phytosociologiques

Scheuchzerietalia palustris: Caricion lasiocarpae, Rhynchosporion albae p. i.a.

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)

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