Peatland dynamics in a complex landscape: Development of a fen-bog complex in the Sporadic Discontinuous Permafrost zone of northern Alberta, Canada

The development of a peatland complex in the Sporadic Discontinuous Permafrost zone of northwestern Alberta, Canada was reconstructed using a series of dated profiles. Peat-forming communities first established c. 10 230 cal. a BP, and by 8000 cal. a BP the site supported monocot fens or marshes in several isolated topographic depressions. Most of the current peatland area initiated between c. 8000 and 4000 cal. a BP, and involved the replacement of upland habitats by shrubby or treed fen and, in some areas, the establishment of Sphagnum on mineral terrain. Ombrotrophic hummock communities had established by c. 7000 cal. a BP, and permafrost was present at 6800 cal. a BP in at least some peat plateau areas. Macrofossil-based reconstructions show considerable local diversity in vegetation succession and permafrost dynamics, with cyclic collapse and aggradation in at least one profile and relative stability in others. Lichen-rich peat is rare in deep-peat plateau cores, and where charcoal was recovered, fire effects on vegetation trajectories varied between cores. Organic matter accumulation was high in the early Holocene and declined after permafrost formation, with low rates especially over the past 4000 years. The site was burned in a wildfire in 1971, and by 1998 permafrost had disappeared from almost all peat plateau areas. In this part of the discontinuous permafrost zone, peat plateaus are likely to be unsustainable under a warming climate. The hydrology and carbon dynamics of former plateau areas following large-scale permafrost degradation require further investigation.