Boreal mud-bottom communities

Description (English)

Sparse, bryophyte-poor, sedge and rush communities of bare, extremely wet peat muds of boreal Palaearctic mires, frequently inundated, remaining wet for a prolonged part of dry periods. The elastic substrate expands and raises when saturated, shrinks in dry periods, forming polygonal networks of surface cracks; there is no peat formation. Mud-bottom communities comprise the same vascular plants as transition mires of unit D2.3, such as Carex limosa, Carex chordorrhiza, Carex rariflora, Carex rostrata, Equisetum fluviatile, Eriophorum angustifolium, Eriophorum gracile, Eriophorum russeolum, but they are more dispersed. Juncus stygius and Utricularia intermedia are, however, characteristic. Bryophytes are absent or scattered, although the small hepatics Cladopodiella fluitans and Gymnocolea inflata are sometimes abundant; a well-developed surface film is formed by microalgae, including filamentous algae such as Zygogonium erieetorum, and numerous desmids and diatoms in fen mud-bottoms. In situations of ochre formation, iron bacteria are abundant. Mud-bottom communities occur in acidic fens of unit D2.2, in rich fens of unit D4.1, in bog hollows of unit D1.1, and, mostly, in flarks or rimpis of aapa mires of unit D3.2 and palsa mires of unit D3.1.

Source: EUNIS habitat classification