The late Holocene record of aeolian and fire activity in northern Québec, Canada

Abstract

A set of 196 14C dates was used to reconstruct Late Holocene aeolian activity in the Hudson Bay area along a south-north transect crossing the northern boreal forest, the forest tundra and the shrub tundra zones. The record indicates a minor period of aeolian activity between 4650 and 4050 BP, and three major periods at 3650-2750 BP and after 700 BP. In the northern boreal forest, there was little temporal variation in dune activity, except around 1300-950 BP where a major peak of activity is recorded. In the forest tundra, two major peaks of activity are recorded between 1650-950 BP and after 700 BP. Only minor activity occurred in the shrub tundra during the last 4000 14C-yr and some aeolian events appear to have been slightly out-of-phase compared to the two other zones. Most dates were obtained from non-charred material in the shrub tundra where, unlike in the Subarctic, the aeolian activity responded to a triggering process unconnected with fire. The dune record is compared with that of gelifluction activity in snowpatch environments and with a detailed fire chronology derived from radiocarbon-dated conifer charcoal sampled in present-day treeless sites of the forest tundra. Post-fire gelifluction reached a maximum around 1500-1100 BP and 750 BP. Fire activity was also at a maximum after 2000 BP in the forest tundra. The similarity of the chronologies suggests that fires occurring during cold periods of the late Holocene were catastrophic, having a significant impact on soil erosion and deforestation.