2001 Volume 10 Issue 2 Pages 67-79
Vegetation history since the Late Glacial was reconstructed by means of pollen analysis and radiocarbon measurement for sediments obtained from Habomai Bog and Ochiishi Cape Bog, Nemuro Peninsula, eastern Hokkaido. Four tephra layers, Ko-c2, Ko-d1, Ta-c1, and Ma-f1, were discriminated in Habomai Bog in the descending order. Two layers, a mixed one of Ko-c2 and Ta-a and one of Ta-c1, were also discriminated in Ochiishi Cape Bog. In Habomai Bog, high bog has developed since 12,000 yr B.P. Taiga composed mainly of Larix gmelinii with Picea jezoensis and/or Picea glehnii and a few Abies sachalinensis and Pinus pumila was distributed between 11,000 and 12,000 yr B.P. Between 10,000 and 11,000 yr B.P., open Larix taiga was distributed under an extremely cold and dry climatic condition. We named this period “Habomai Stadial”, which probably correspond to the Younger Dryas. After disappearance of Larix gmelinii at 7000 yr B.P., Picea jezoensis and/or Picea glehnii survived there till 5200 yr B.P. A broad-leaf forest composed mainly of Quercus was established at 5200 yr B.P. and has existed there to the present. The dry condition caused by the strong local wind prohibited the distribution of conifer trees. In Ochiishi Cape Bog, peat has been deposited since 4600 yr B.P. A Picea glehnii forest mixed mainly with Abies sachalinensis and Quercus has developed around the bog till present. Fluctuations in forest components around the bog might be caused by changes of the underground water level.
