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 Elgennya Lake (62 degrees 05'N 149 degrees 00'E, 1040 m) which is located near the altitudinal forest limit in the western Annachag Mountains of the Upper Kolyma region, northeastern Siberia. Palynological data indicate the presence of a relatively unproductive herb-Salix tundra during full-glacial times. Although Betula shrubs first appeared in this upland valley at c. 12 100 yr BP, they probably were few in number. More significant changes in the vegetation date to c. 10 100 yr BP when Alnus shrubs, and perhaps a few Larix trees, colonized the Elgennya catchment. A Larix dahurica forest established in the valley by c. 9400 yr BP. By c. 8600 yr BP, Pinus pumila grew within the forest understorey and formed a shrub tundra beyond altitudinal tree-line. Arrival times for Betula, Alnus, Larix and Pinus differ by 400 (for both Betula and Pinus), 2500 and 2200 radiocarbon years, respectively, when compared to mid-elevation sites located in the eastern Annachag Mountains. Evidence for tree-line fluctuations, originally inferred from these eastern sites, is absent in the Elgennya record. Palaeoclimatic interpretations of the pollen data from the Upper Kolyma region suggest that both summer temperature and late fall/early winter snowfall play key roles in determining the observed palaeovegetational patterns. This relationship contrasts with the Alaskan pollen records which primarily seem to reflect changes in summer conditions.