Palaeo-environmental changes during the Last Glacial Stage and the palaeo-ecology of Hemiptelea mikii using fossil pollen and wood profiles from the deposits along the Hanamuro River, Ibaraki Prefecture, eastern Japan

Abstract

We reconstructed the palaeo-environmental changes during the Last Glacial Stage from fossil pollen and wood profiles and radiocarbon dates of the deposits along the Hanamuro River, Ibaraki Prefecture, eastern Japan. The fossil pollen and wood profiles indicated that, on the upland, 1) in ca. >50–43 ka, a cool temperate deciduous broad-leaved forest was distributed in a somewhat warm climate, 2) in ca. 38–35 ka, a mixed forest of cooltemperate deciduous broad-leaved trees and boreal conifers dominated in a cool climate, and 3) in ca. 35–17 ka, a boreal coniferous forest was distributed in a cold climate. On gentle slopes and valley floors, a swamp forest consisting of Alnus and Salix developed in ca. >50–24 ka. In ca. 24–17 ka, a grassland expanded on the peat land. Additionally, we investigated the palaeo-ecology of an extinct Hemiptelea mikii Minaki et al. It grew around this region until ca. 43–38 ka and seemed to have died out, due to the cold and dry conditions during the Last Glacial Maximum. It is highly possible that its habitat was influenced by the soil disturbance and the fluctuation of ground-water level.