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

The palynological records of arctic tree-lines in North America give c lear evidence of large scale northward displacement of the forest limi t during the early Holocene. However, small scale or local changes in forests that occurred during the mid or late Holocene have been more d ifficult to detect using pollen analysis. A grid of sites from the reg ion to the east of the MacKenzie Delta, N.W.T., provides a good tempor al and spatial record of tree-line (forest) movements. Detailed pollen and macrofossil analyses at three sites, Reindeer Lake, Sleet Lake an d Bluffer's Pingo, which lie 50, 75, and 100 km north of the modern fo rest limit, respectively, provide a detailed paleoecological record. T he evidence indicates that the northward displacement of forests in th e 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 wo odlands with black spruce grew as far north as Sleet Lake from 8400 to 3500 yr BP. These woodlands gradually retreated to just south of Rein deer Lake during the late Holocene.