A LACUSTRINE POLLEN RECORD FROM NEAR ALTITUDINAL FOREST LIMIT, UPPER KOLYMA REGION, NORTHEASTERN SIBERIA

A sediment core that spans the last c. 15 000 yr BP was raised from El gennya Lake (62 degrees 05'N 149 degrees 00'E, 1040 m) which is locate d near the altitudinal forest limit in the western Annachag Mountains of the Upper Kolyma region, northeastern Siberia. Palynological data i ndicate the presence of a relatively unproductive herb-Salix tundra du ring full-glacial times. Although Betula shrubs first appeared in this upland valley at c. 12 100 yr BP, they probably were few in number. M ore significant changes in the vegetation date to c. 10 100 yr BP when Alnus shrubs, and perhaps a few Larix trees, colonized the Elgennya c atchment. A Larix dahurica forest established in the valley by c. 9400 yr BP. By c. 8600 yr BP, Pinus pumila grew within the forest understo rey and formed a shrub tundra beyond altitudinal tree-line. Arrival ti mes for Betula, Alnus, Larix and Pinus differ by 400 (for both Betula and Pinus), 2500 and 2200 radiocarbon years, respectively, when compar ed to mid-elevation sites located in the eastern Annachag Mountains. E vidence for tree-line fluctuations, originally inferred from these eas tern sites, is absent in the Elgennya record. Palaeoclimatic interpret ations of the pollen data from the Upper Kolyma region suggest that bo th summer temperature and late fall/early winter snowfall play key rol es in determining the observed palaeovegetational patterns. This relat ionship contrasts with the Alaskan pollen records which primarily seem to reflect changes in summer conditions.