Fires of the last millennium led to landscapes dominated by early successional species in Québec's Clay Belt Boreal Forest, Canada

Abstract

This study presents the long-term (over the last 8000 years) natural variability of a portion of the Picea mariana-moss bioclimatic domain belonging to Québec's Clay Belt. The landscapes are dominated by mesic-subhydric clay and early successional forests composed of Populus tremuloides, Pinus banksiana and Picea mariana. The natural variability (fires and vegetation) of one of these landscapes was reconstructed by means of pollen and macroscopic charcoal analysis of sedimentary archives from two peatlands in order to assess when and how such landscapes were formed. Following an initial afforestation period dominated by Picea (8000-6800 cal. Years BP), small and low-severity fires favored the development and maintenance of landscapes dominated by Picea and Abies balsamea during a long period (6800-1000 BP). Over the last 1000 years, fires have become more severe and covered a larger area. These fires initiated a recurrence dynamic of early successional stands maintained until today. A decline of Abies balsamea has occurred over the last centuries, while the pollen representation of Pinus banksiana has recently reached its highest abundance. We hypothesize that the fire regime of the last millennium could characterize Québec's Clay Belt belonging to the western Picea mariana-moss and Abies balsamea-Betula papyrifera domains.