Some Problems on the Genesis of “Kurboku” Soils

Abstract

The term “Kuroboku” soils is a tentative name for black-colored, mellow soils of both volcanogenous and non-volcanogenous origin. Pedological studies of the soils, especially on their humus accumulation suggest their genesis under grass vegetation and monsoonal climate. Part of the discussion on these problems was already presented in this Bulletin (Vol. 3, pp. 40-50).
It is revealed, based on field occurrence, that the “Kuroboku” soils have been formed since an age not so older than late Pleistocene.
The possible genetic conditions deduced from pedological studies seem to correspond with the history of late Quaternary. The climate aquired its present monsoonal character probably since the end of the last glacial age. No extensive grass vegetation could be introduced without destruction of naturally stable forest cover under the monsoonal climate. The destruction might be accelerated under more advanced human culture starting at later stage of the pre-Jomon culture (latest Pleistocene).