51.11 - Buttes, bourrelets et gazons tourbeux (Habitats de Saint-Pierre-et-Miquelon)

51.11 - Buttes, bourrelets et gazons tourbeux

Bog hummocks, ridges and lawns

Typologie des habitats de Saint-Pierre-et-Miquelon

Descriptif anglais

Vegetation of the higher parts of the plateau of Palaearctic bogs and of its drier, marginal slope. Intact, typical, raised bogs of northern, lowland and low montane central and eastern Europe display an alternance of well-marked sphagnum hummocks, colonized or not, especially in their drier upper part, by small shrubs, lower, wetter, flat lawns and wet hollows or schlenken. Sphagnum hummocks with no, or few, shrubs are listed in unit 51.111, sphagnum hummocks, or parts of them, colonized by shrubs in unit 51.113, lawns in unit 51.112. In bogs under strong oceanic influence, in high-altitude bogs, in bogs subjected to mineralotrophic influences or anthropogenic degradation, a sparse cover of shrubs or tussock-forming graminoids may become ubiquitous and the distinction between hummock and lawn, or even between hummock, lawn and hollow, blurred, in bogs that are often somewhat intermediate towards blanket bogs. Such communities are listed in units 51.114 to 51.116, as well as in 51.17 and in 51.2; in some of them sphagna may be scarce or replaced by bryopsid mosses. Well-defined sphagnum hummocks of unit 51.111 may nevertheless develop in conjunction with them. The dominance role is played by deergrass, Scirpus cespitosus, in montane central European bogs, or parts of bogs listed in unit 51.114. In Atlantic bogs listed in unit 51.115 it is played by Erica tetralix. Somewhat degraded bogs, in particular, bogs affected by anthropozoogenic influences in Atlantic climates, may be overwhelmingly dominated by Eriophorum vaginatum, usually with complete blurring of the structure. They are listed in unit 51.116. More severely degraded bogs, invaded by Molinia caerulea, are listed in unit 51.2. The highly distinctive shrub and sphagnum or shrub and moss hummocks bog expanses of the montane, rapidly dessicating, bogs of the boreal and subarctic zones are listed in unit 51.17. Sphagnum hummocks forming in acidic fens (unit 54.4), transition mires (unit 54.5) or, sometimes, rich fens (unit 54.2), are also indicated by codes of units 51.111 or 51.113.

Correspondances phytosociologiques

Sphagnion magellanici, Oxycocco-Ericion tetralicis p.

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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