Late Quaternary vegetation of Chukotka (Northeast Russia), implications for Glacial and Holocene environments of Beringia

Two lake records from the Kankaren region of southern Chukotka, when combined with other palynological and macrofossil data, document spatial and temporal variations in the regional vegetation history since similar to 21,000 C-14/25,400 cal yr BP. Full-glacial environments were severely cold and arid in central and northern Chukotka, whereas southern sites experienced conditions that were relatively moist, although still drier than present. Southern Chukotka may represent a western extension of environments of the land bridge proper, including a possible "moisture" barrier to intercontinental migration. Shrub Betula tundra established earliest in southern Chukotka (similar to 15,800-14,000 C-14/19,000-16,700 cal yr BP; similar to 13,000 C-14/15,300 cal yr BP central and north), Pinus pumila earliest in the north (similar to 9600 C-14/11,100 cal yr BP; similar to 7600 C-14/8400 cal yr BP south), and shrub Alnus earliest in both the south and north (similar to 12,000-11,000 C-14/13,800-12,900 cal yr BP). These patterns support the presence of cryptic refugia for Betula and Alnus in Chukotka during the full glaciation. In contrast, P. pumila probably migrated into Chukotka from populations located in the northern coastal lowlands and from mountainous regions of southwestern Beringia. Evidence for a thermal optimum (similar to 11,000-8000 C-14/12,900-9000 cal yr BP) is strong in northern Chukotka but is absent in central and southern areas. (C) 2014 Elsevier Ltd. All rights reserved.