Changes in vegetation, climate and snowfall regime since the late Pleistocene in a snowy mountainous region of central Japan

Abstract

Although the most crucial factor shaping vegetation history is temperature, snowfall regime is also important in regions of heavy snow. Pollen analysis in a mire in a snowy mountainous region of central Japan revealed histories of vegetation and precipitation regimes since the latest Pleistocene. The abundance of pinaceous pollen during the latest Pleistocene indicates a subalpine regional coniferous forest and cooler conditions; moreover, sandy sediment and significant occurrence of pollen from Artemisia along with several alpine elements suggest local plant communities of poor vegetation cover in an erosive environment. The increase in Betula and Quercus subgen. Lepidobalanus pollen and the decline in pinaceous pollen in 13,550 cal. yr BP indicates climatic amelioration favourable to temperate trees, and the invasion of sedges and Reynoutria to the small basin and the onset of peat deposition suggest an increase in summer rain. The increase in Fagus crenata pollen after 11,130 cal. yr BP and onwards indicates that the present heavy snowfall regime induced by inflow of the Tsushima Current has been established since that age. The climatic amelioration delayed establishment of the heavy snowfall regime for more than 2400 years. In addition, the retreat of sedges and subsequent invasion of several species of drier habitat after 11,130 cal. yr BP indicate a drier mire condition caused by increased summer temperatures. The recovery of sedges after 3740 cal. yr BP indicates the wettest mire conditions induced by climatic deterioration. A general increasing tendency of conifers in this period supports this interpretation.