Vegetation gradients of minerotrophically rich fens in western Alberta

Abstract

The vascular plant and bryophyte vegetation of 50 stands in nine sites from the foothills of western Alberta were quantitatively sampled in order to determine the major vegetation gradients. These fens are mostly patterned, with pools of water (flarks), alternating with raised ridges (strings), and are minerotrophically rich. Mean calcium ion concentrations of the nine fens range between 18 and 37 ppm and mean pH values range between 6.8 and 7.9, with electrical conductivities varying from 140 to 456 μmho/cm (1 mho = 1S). One string community type, dominated by Tomenthypnum nitens, Betula glandulifera, and Larix laricina. and one flark community type, dominated by Scorpidium scorpioides, Drepanocladus revolvens, and Carex limosa, are described, with three phases recognized in the flarks. (The Scorpidium scorpioides phase is most prominent in the wettest flarks, with the Campylium stellatum – Scirpus spp. phase found in slightly drier habitats.) The water chemistry and vegetation of these rich fens compares well with similar mires described from eastern Canada and Fennoscandia. Indirect and direct gradient analysis techniques illustrate a wet–dry ecological series of bryophytes rich in Amblystegiaceae and lacking in Sphagnaceae.