Humus accumulation in Holocene paleosols formed in Japanese tephra

Andisol profiles develop according to the rates of volcanic ash supply and of soil formation. In many parts of Japan, there are tephra-Andisol sequences with buried soils which are rich in humus and clay. The buried soils were formed approximately 5–8 ka ago during the Holocene Climatic Optimum, and since then extensive environmental changes have occurred. The vertical distributions of organic C, the C/N ratio and molecular weathering ratios (silica/alumina, alumina/bases) were examined in Holocene tephra-Andisol sequences in Northern, Central and Southern Japan to trace changes in the strength of pedogenetic weathering and variations in biomass during the Holocene.