51 - Tourbières bombées

Raised bogs

Typologie des habitats de Saint-Pierre-et-Miquelon

Descriptif anglais

Highly oligotrophic, strongly acidic communities composed mainly of sphagnum growing on, and forming, peat and deriving moisture and nutrients only from rainfall (ombrotrophic). They form only in cool climates with heavy rainfall. They are most widespread in the boreal zone and in the mountains and hills of the nemoral zone; they occur locally in the lowlands of the nemoral zone and rarely in the middle Eurasian steppe zone. Within the western Palaearctic region, they are characteristic of lowlands and hills of northwestern and northern Europe, the adjacent Hercynian ranges, the Jura, the Alps, the Carpathians. In the eastern Palaearctic, they are known from Amurland, West Kamchatka, East Kamchatka, Sakhalin, the Altai. Their independence from ground water is the result either of upward growth or of changes in the water table. Bogs harbour, in addition to various sphagnum species, which are abundant, dominant and the major component of their formation, a small number of acidophilous plants such as Eriophorum vaginatum, Scirpus cespitosus (Trichophorum cespitosum), Carex pauciflora, Carex paupercula, Ledum palustre, Vaccinium oxycoccos, Andromeda polifolia, Drosera rotundifolia and lichens. Animal species are not numerous but those that are adapted to bogs are highly specialised. Among typical invertebrates figure dragonflies (Leucorrhinia dubia, Aeshna subarctica, Aeshna caerulea, Aeshna juncea, Somatochlora arctica, Somatochlora alpestris), lepidopterans (Colias palaeno, Boloria aquilonaris, Coenonympha tullia, Vacciniina optilete, Hypenodes turfosalis, Eugraphe subrosea), beetles, ants (Formica exsecta), bugs and spiders (Pardosa sphagnicola, Glyphesis cottonae). Most of the species that bogs harbour are rare and their populations fragmented into isolated relictual elements; several are threatened. The remaining intact or nearly intact communities are exceptional.

Correspondances phytosociologiques

Sphagnetalia magellanici, Scheuchzerietalia palustris p., Utricularietalia intermedio-minoris p., Caricetalia fuscae 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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