Difference in Past Vegetation between Black Soils and Brown Forest Soils Derived from Volcanic Ash at Mt. Kurohime, Nagano Pref. Japan

Abstract

A mosaic distribution pattern of Black soil and Brown forest soil is commonly observed on the lower slopes of volcanoes in Japan. These two soils are often distributed on similar topography, and they are derived from the same parent material.One of the hypotheses concerning the genesis of these soils is that the Black soil may have been formed under grassland vegetation and the Brown forest soil under the forests in the past. Little research has, however, been carried out until the present.Plant opal and pollen analyses of soils were carried out to distinguish differences in past vegetation between the two soil types on Mt. Kurohime in Nagano Prefecture. The results obtained are as follows.(1) Plant opals from Panicoideae, Festuceae and Sasa spp. are dominant in the Black soils, whereas in the Brown forest soils those from Sasa spp. are dominant.(2) Non-arboreal pollens such as Gramineae and Compositae are dominant in the Black soils, although pollen of Fagus is a major component in the Brown forest soils.(3) From the results mentioned above, it is concluded that grassland vegetation covered the Black soils but the Beech-Sasa community grew on the Brown forest soils in the past.