Holocene climatic changes and vegetation development in the Kuril Islands

The response of Kuril Island vegetation to climatic changes during the Holocene is reconstructed from data obtained from key sections that included various depositional environments. These climatic fluctuations were not as marked in the Kuril archipelago as they were in nearby continental margins and large islands. During the Early Holocene dwarf stone pine, coniferous and birch forest, prevailed in the South Kurils, and tundra landscapes in the North Kurils. The greatest northward movement of Kuril vegetation zones occurred during the Holocene Optimum (similar to 6600-5000 C-14 BP). Mean annual temperatures in the Kuril Islands were 2-3 degrees C higher than modern. Shifts in the location of warm and cold marine currents, which strengthened or dampened insolation-driven climatic changes, played an important role in vegetation development. Cool-temperate broadleaf forests and mixed coniferous-broadleaf forests were widespread on South Kurils. Rising Holocene sea levels flooded land bridge connections to Hokkaido Island and the mainland, resulting in the formation of several small islands in the South Kurils, meadows and boggy landscapes prevailed. This flooding had a great effect on repopulation of island biota as did the deep straits that separate southern islands from the Central and North Kurils. All paleovegetation associations can be found on the current landscape, although their geographic distribution has changed during the Holocene. No introduction of plants from adjacent land occurred in the Holocene. Forb and graminoid meadows characterized the Middle Holocene vegetation of Central Kurils. On North Kurils forb meadows were widespread, tundra area decreased. Climatic changes did not occur synchronously throughout the Kurils, at times not even on the closest islands. Local volcanism played a special role in Kuril vegetation history. The considerable microclimatic variability within the islands also has been important in determining the development and preservation of vegetation communities and their reaction to more regional climatic changes. (C) 2012 Elsevier Ltd and INQUA. All rights reserved.