LATE HOLOCENE DEFORESTATION AND PEAT FORM ATION IN CHARLEVOIX HIGHLANDS - ONSET OF THE SUB-ALPINE AND ALPINE BELTS

Late Holocene deforestation and peat formation in the Charlevoix highl ands: Onset of the subalpine and alpine belts. Fire history based on C -14 ages of soil charcoal in the Charlevoix highlands was reconstructe d for the late Holocene. The subalpine and alpine belts developed afte r 3000 BP. Fire occurred sporadically and contributed to forest fragme ntation and reduction in tree regeneration likely in relation to clima te deterioration. The subalpine and alpine vegetation is thus a respon se to ecological changes induced by recurrent fires, rather than a dir ect response to a climatic gradient associated with topography. Differ ences found in highland vegetation (forested or open) at similar altit udes resulted from differential fire influence among sites. Feat forma tion on slopes started after 1250 BP and intensified after 600 BP. The delay between fire occurrence and peat formation indicates that peat actually started to accumulate when a general trend toward climate coo ling occurred after the Little Climatic Optimum period, a thousand yea rs ago. In spite of this delay, it is likely that shallow ombrotrophic peat formed over steep slopes in reponse to postfire forest opening o n the highlands.