On the classification and genesis of soils, derived from andesitic volcanic material under a monsoon climate.

Abstract

The Lawu volcano was sampled from an altitude of 500-3, 300 m and investigated morphologically, mineralogically and chemically. The soil organic matter was analysed in respect of its C, H, O and N content. Comparison of soils in a monsoon climate with those formed in a wet climate showed that the process of laterization proceeded to higher altitudes in a monsoon climate. It seems possible to recognize the following belts: a zone from 3, 300 to 2, 500 m altitude with brown podzolic soils, 2, 000-1, 400 m with brown forest soils, 1, 400-1, 000 m with latosolic brown forest soils and 1, 000-300 m with brown and reddish-brown latosolic soils. Organic acid was a more important soil-forming factor than CO₂ at altitudes > 1, 000 m and under a monsoon climate. An explanation is proposed for the curious trends of C/N ratios of the soil and organic matter and for the trends in the clay's molar Al₂O₃/Fe₂O₃ ratios.-From authors' summary. (Abstract retrieved from CAB Abstracts by CABI’s permission)