An 11,000 year record of plant community stability and paludification in a patterned rich fen in northeastern Alberta, Canada

Patterned rich fens have a diverse flora and are maintained by unidirectional inflowing water with high concentrations of base cations, along with high pH and limited nutrients. Rich fens are among the most threatened ecosystems in Europe, but are not uncommon across the western boreal forest zone of Canada. Utilizing 10 radiocarbon dated cores extracted from the wetland, we investigated the Holocene developmental history of a large patterned rich fen in northeastern Alberta (McClelland Wetland). Organic matter accumulation began around 11,457 cal yr BP as primary peat formation on recently deglaciated substrates. Over the 10,000+ years history of McClelland Wetland, the central portions of the wetland have been remarkably resistant to change, with little alteration in dominant species. The resistance to change is set against a background of fluctuations in regional Holocene climate and local varying water balance. The dominant bryophyte species (Hamatocaulis vernicosus and Scorpidium scorpioides) continued to play a foundational role on site for the duration of the Holocene, dependent on a persistent long-term ground water source. Accumulation rates of organic matter have remained steady once the dominant bryophyte layer was established, but with accumulation rates at paludifying marginal sites lower than those of the central moss-graminoid-dominated areas.