Boreal mud-bottom communities

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 Q25, 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 of EUNIS 2012 now split in Q22, Q23, Q24, in rich fens of unit Q41, in bog hollows of unit Q11, and, mostly, in flarks or rimpis of aapa mires of unit D3.2 of EUNIS 2012 and palsa mires of unit Q31.

Código Eunis 2021: Q25H2