Holocene Refugium of Shrubby Birch Betula humilis Schrank and Avens Dryas sp. in Kazakh Uplands.

Abstract

Macrofossils of shrubby birch (Betula humilis) of the boreal species group and avens (Dryas sp.) of the Arctic-alpine species group, both dated to ~2500 radiocarbon years ago, were found in the Kazakh Uplands (Abylai site, 49°15' N, 75°07' E). The species are currently absent from the region. The finds indicate that a refugium of the species existed in the Kazakh Uplands in the Holocene. The species appeared on the territory of the Kazakh Uplands at the end of the Late Pleistocene. At the beginning of the Holocene, their ranges retreated to the north and a refugium formed on the territory of the Kazakh Uplands. Sharply continental climate and favorable edaphic conditions contributed to the preservation of the refugium. The disappearance of the refugium was associated with biocenotic reorganization, which affected the vegetation in the second half of the Late Holocene and was caused by climate changes.