Sediment cores were obtained from nine small lakes located along a broad latitudinal transect extending from central Alberta to the middle Mackenzie River valley, Northwest Territories. The radiocarbon dated fossil pollen records from these cores provided data for the reconstruction of postglacial vegetation development in the western Canadian Boreal Forest. The results from this research were combined with information provided in previously published palaeobotanical studies from the western Canadian interior and Alaska to reconstruct postglacial plant migration patterns in western Canada. An extensive network of modern pollen surface samples from western Canada aided in the interpretation of the fossil pollen record.
The western Canadian Boreal Forest region was deglaciated by at least 11,000 to 10,500 BP and initially supported a sparse, herb dominated vegetation. Populus was the only tree present during this period. This early vegetation was replaced by Picea forest in central Alberta and adjacent British Columbia at 10,000 BP. In the western Northwest Territories, extensive Betula glandulosa tundra developed between 10,500 and 10,000 BP and was subsequently replaced by Picea forest at 9000 to 8500 BP. Betula papyrifera, Pinus contorta, Pinus banksiana and Alnus crispa appeared in the western Boreal Forest during the mid-Holocene. This pattern of vegetation development was probably primarily controlled by the differential migration rates of plan species into the region following deglaciation, and by progressive edaphic development.