VEGETATIONAL HISTORY SINCE THE LAST GLACIAL STAGE AT NAKAYAMA MOOR,SOUTH-WESTERN 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, deduced from the pollen record and 14C dating by accelerator mass spectrometry, at three sites along 43 degrees N, in subalpine Hokkaido since the last glacial stage. Fossil pollen from three cores taken at Loc.1 and Loc.2, which are both 870 m above sea level, and at Loc.3, which is 910 m above sea level, and now surrounded by the subarctic forest species Picea glehnii, revealed different vegetational histories. During the late glacial substage, mixed forest at Loc.2 composed mainly of Picea, Larix gmelinii, Pinus pumila, Betula and Alnus together with Selaginella selaginoides developed under a cold climate. Boreal coniferous forest characterized by Picea and Betula coexisting with a few aquatic plants developed after 10,830 yr BP. After 8935 yr BP, Juglans and Quercus increased. Aquatic plants such as Nuphar and Juglans increased relative to Betula. These aquatic plants grew until about 8,500 yr BP. Quercus, which grows in a warm climate associated with Ilex, persisted for a period of about 7500 years. Although Picea at Loc.1 increased after 1840 yr BP,at Loc.2 the Picea pollen count showed a sharp peak after 460 yr BP and then gradually decreased. From a depth of 0.2 m to the surface, there was a rapid increase of Betula and a decrease of Quercus. The surface appearance of Quercus is thought to have resulted from wind transport because at present Quercus forest does not grow in the vicinity. At Loc.2, the partial disappearance of the Picea forest that presently covers a wide area of the moors in the subalpine zone at 43 degrees N suggests that further global warming has continued. Evidence of Betula forest from the surface record at Loc.2 is considered to have resulted from human activity. The vegetational history at Loc.3 differs from that at both Loc.1 and Loc.2.