A paleoecological analysis of a southern permafrost peatland, Charlevoix, Quebec

The southernmost site where permafrost has been located in the Quebec-Labra dor peninsula is in a peatland on the subalpine summit of Lac des Cygnes Mo untain (47 degrees 41'N, 70 degrees 36'W). Because of the thickness of its peat deposit, this site contains rich ecological information about the hist ory of the peatland and its surrounding subalpine environment. We conducted a detailed macrofossil analysis to reconstruct the 6000-year history of th e peatland. In general, the development of the Lac des Cygnes Mountain peat land has followed the classic succession of rich fen - poor fen - bog found in other peatlands in subarctic, boreal, and temperate environments. An ab rupt decline in all tree macrofossils ca. 4000 BP suggests that a major def orestation event occurred on the summit of Lac des Cygnes Mountain. The exa ct cause of this deforestation event is unknown, but fire is a possible fac tor. The lack of absolute chronological resolution near the top of the macr ofossil record precludes proper dating of permafrost inception, but the bal ance of evidence appears to indicate that the permafrost is modern.