Évolution holocène d'une tourbière à pergélisol (Québec nordique)

• Published in: Canadian Journal of Botany
• Main Authors: Couillard, Line, Payette, Serge
• Format: Article in Journal/Newspaper
• Language: French
• Published: Canadian Science Publishing 1985
• Subjects: Plant Science; Tamarack; palsas; Thermokarst; pergélisol
• Online Access: http://dx.doi.org/10.1139/b85-152; http://www.nrcresearchpress.com/doi/pdf/10.1139/b85-152

The Holocene development of a peat plateau peatland in northern Québec has been reconstructed from present vegetation and buried macrofossil analogues found in peat. This peatland is presently formed by nine morphological units characterized by homogenous site conditions (drainage, topography, and vegetation cover). Seven ombrotrophic and eight minerotrophic vegetation types are found in the peatland, but the ombrotrophic types cover 66% of the peatland surface. Reconstitution of the Holocene peatland development from 3700 BP to present was based on the succession of bryophytes within the morphological units. Between 3200 and 2700 BP, minerotrophic vegetation such as sedge fens, pools, and tamarack woodlands (now locally extinct) dominated the peatland. Peat plateaus and palsas were progressively formed after 2700 BP. The expansion of these units is closely related to several cooling periods that occurred after 2700, 1400, 1100, 700, and 150 BP. Thermokarst pools were created within the peat plateaus around 1100 BP after a burn, and other similar depressions formed around 340 BP and Present because of the recent climatic warming. Plant successions show that long-term vegetation development in the peatland is rather complex and diversified. These successions indicate that peat plateaus gradually developed during the last thousand years in relation with topographical conditions, drainage, vegetation cover, fire, and climate. Palsas were formed more recently than peat plateaus, between 700 and 500 years BP, and around 150 years BP.