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 ∼21,000 14 C/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 (∼15,800–14,000 14 C/19,000–16,700 cal yr BP; ∼13,000 14 C/15,300 cal yr BP central and north), Pinus pumila earliest in the north (∼9600 14 C/11,100 cal yr BP; ∼7600 14 C/8400 cal yr BP south), and shrub Alnus earliest in both the south and north (∼12,000–11,000 14 C/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 (∼11,000–8000 14 C/12,900–9000 cal yr BP) is strong in northern Chukotka but is absent in central and southern areas. [ABSTRACT FROM AUTHOR]