干旱区生态环境知识资源中心

A 14,000 yr high-resolution pollen and lake-level record from Windmill Lake in central Alaska provides new evidence for the Late Pleistocene and Holocene paleoenvironments of this region. At 14,000 C-14 yr BP, sparse herb tundra and low lake-levels indicate a cold, arid environment. About 11,800 (14)CyrBP, the vegetation abruptly shifted to a shrub tundra and lake-levels increased, suggesting warmer and more mesic conditions. Ca 10,500-10,200 C-14 yr BP, herbaceous taxa increased at the expense of the shrubs, suggesting a transient episode of climatic deterioration nearly contemporaneous with the Younger Dryas chronozone. By 8000 C-14 yr BP, spruce was present in the watershed and alder grew locally by 6500 C-14 yr BP. The AMS radiocarbon chronology indicates later expansions of Betula, Picea, and Alnus than at most sites in central Alaska, which are conventionally dated. (C) 2000 Elsevier Science Ltd. All rights reserved.