PALEOENVIRONMENTAL CHANGES SINCE THE LAST GLACIAL STAGE IN CENTRAL HOKKAIDO, JAPAN

Hokkaido is situated at the northeastern edge of continental Eurasia, surrounded by the North Pacific, the Sea of Okhotsk, and the Sea of Japan. We present a brief report concerning the changes in vegetation on Hokkaido during the last glacial stage. At that time, high mountains were the only areas in the Japanese islands that were covered with glaciers. Five moorland sites located along 43 degree N were studied with regard to their forest history, and the following results were obtained: 1. Some pyroclastic layers in the peat cores were correlated with pyroclastic ash deposits from the Tarumae volcano in Hokkaido, and their stratigraphy has already been established. 2. Site Yu2 is located at an altitude of 75 m, where there are 3 pollen zones in descending order from zone Yu2-A to zone Yu2-C. Yu2-A is characterized by Picea pollen, Yu2-B by Quercus, and Yu2-C by Salix. 3. Moor Ku1 is located at an altitude of 49 m, where there are 4 pollen zones in descending order from Ku-A to Ku-D. In these zones, Tsuga, which has already disappeared due to paleoenvironmental changes in this area, accounted for about 5% of total pollen continuously since the last glacial stage. 4. Moor Yb1 is located at an altitude of 305 m, where there are 5 pollen zones in descending order from Yb-A to Yb-E . After a warm period in the hypsithermal interval (ca. 6000 yBP), there was a short period during which Quercus increased and Picea decreased in Yb-C. Such a change is rare elsewhere in Hokkaido. 5. Yo1 is located at an altitude of 1820 m, at the summit of Mt. Yotei. There are 2 pollen zones, Yo-A to Yo-B, in descending order. Yo-A is characterized by Pinus, and Yo-B by Betula. The admission numbers are 4-30, 4-718, and 46-19. 6. Moor Su1 lies at an altitude of 35 m, where there are 2 pollen zones, Su-A to Su-B, in descending order. Su-A is characterized by Quercus and Abies, and Su-B by Betula. The surface sample in particular contains a lot of Betula and reduced amounts of conifer pollen. The bottom of Su-B is characterized by an increase of Fagus pollen from a depth of 58 cm. 7. The 14C date determined by accelerator mass spectrometry between Su-A and Su-B was 160±30 yr BP (NUTA2-1401). 8. The increase of Salix at Yu2-C may be due to human activity, whereas the increase of Betula at the surface may be due to global warming.