THE VEGETATIONAL COVER OF QUEBEC-LABRADOR AT 6000 YEARS BP - AN ESSAY

The vegetational cover of Quebec-Labrador at 6000 years BP: An essay. A cartographic reconstruction of the vegetational cover of Quebec-Labr ador for 6 ka BP is based on palynological and plant macrofossil recor ds. A dense Shrub Tundra occupied the stretches of land between marine waters (Tyrrell Sea or d'Iberville Sea) and the residual ice masses t hat still occupied over 100 000 km(2), from Ungava (Nunavik) to the Sc hefferville area. This Tundra belt was narrow along the southern limit of glaciers but expanded eastward to a width of more than 400 km, ext ending to the Labrador Sea north of latitude 54 degrees. The tree-line thus ran approximately through the middle of the present-day Taiga zo ne (open boreal forest), but the northern limit of the Closed Forest a lready corresponded to its modern position. Like the Tundra, the 6 ka BP Taiga was shrubby, more dense, and more diversified than todays, pr obably due to favorable climatic conditions but also because soils con tained more nutrients than today. The southern forest vegetation zones , dominated respectively by spruce, fir, and maple, generally occupied their modern positions, but the abundance of some companion tree-spec ies differed markedly from the modern. The differences are attributed 1) to delayed migration, as in the case of jack pine (Pinus banksiana) in the Western Spruce Forest domain or American beech (Fagus grandifo lia) in the Maple Forest domain, 2) to a generally lower incidence of natural fires, 3) to a lower impact of paludification on hydric sites, and 4) to an overall milder climate. An analysis of the records at a regional scale permits the identification of more detailed, ultimately climatically-controlled phytogeographic gradients and fields, especia lly in mountain and subalpine zones.