THE PALYNOLOGICAL RECORD OF LATE-QUATERNARY ARCTIC TREE-LINE IN NORTHWEST CANADA

The palynological records of arctic tree-lines in North America give clear evidence of large scale northward displacement of the forest limit during the early Holocene. However, small scale or local changes in forests that occurred during the mid or late Holocene have been more difficult to detect using pollen analysis. A grid of sites from the region to the east of the MacKenzie Delta, N.W.T., provides a good temporal and spatial record of tree-line (forest) movements. Detailed pollen and macrofossil analyses at three sites, Reindeer Lake, Sleet Lake and Bluffer's Pingo, which lie 50, 75, and 100 km north of the modern forest limit, respectively, provide a detailed paleoecological record. The evidence indicates that the northward displacement of forests in the early Holocene from 10,000 to 8400 yr BP was not simply a northward shift of trees but that a complex pattern of vegetation developed with white spruce populations growing north of open poplar stands. Open woodlands with black spruce grew as far north as Sleet Lake from 8400 to 3500 yr BP. These woodlands gradually retreated to just south of Reindeer Lake during the late Holocene.