Humus Composition of Charred Plant Residues

Abstract

Japan is a typical volcanic country. Volcanic ash soils which develop in deposits of volcanic ash are widely distributed in Japan. Studies have shown that an important feature of humus in the A horizons of volcanic ash soils is the predominance of Type A humic acids with a high degree of humification (1, 2). The formation of Type A humic acids may proceed with the mediation of soil enzymes and inorganic components, since they are capable of accelerating the conversion of phenolic compounds to humic polymers with a high degree of darkening (3–5). As another possible mode, the authors suggested that the charring process of plants might contribute to the formation of Type A humic acids, because the abundant accumulation of humus in volcanic ash soils may be attributed to the presence of a dense grass vegetation and to the burning of these materials (6). Furthermore, carbonaceous materials such as charcoal and cinder are considered to be one of the possible sources of soil humus (7). In the present study, to ...