ABSTRACT
Though the soils appear to be found in a wide range of climatic conditions, from subalpine regions to the humid tropics, they seem to constitute a group of soils with similar morphological, physical, and mineralogical characteristics (Shoji et al., 1994; Tan, 1964). Conspicuous among these is the common thick black surface horizon, rich in humus and dominated by amorphous, noncrystalline, or paracrystalline clays. The latter are considered to be allophane and imogolite, weathering products of volcanic glass. The soil colloidal fractions may also contain hydrated silica and alumina, which together with allophane reect the soil’s highly reactive surfaces. The black color was the reason why U.S. soil scientists previously called the soils ando soils (Simonson, 1979; Thorp and Smith, 1949). In Japanese an means “dark” or “black” and do means “soil.” Many Japanese scientists are also referring to them as kuroboku (kuro means “black” and boku means “friable”) soils, whereas others use the name humic allophane soils (Kanno, 1962; Wright, 1964).
