Active aluminum status in surface horizons showing continuous climosequence of volcanic ash-derived soils in Towada district, northeastern Japan

The relationship between the status of active Al of surface horizons formed in Towada-a ash and climatic conditions was studied in the Towada district, Aomori Prefecture. The mean monthly air temperature and precipitation were estimated from 1-km 2 mesh data supplied by the Japan Meteorological Agency. Thornthwaite's P-E (precipitation-evapotranspiration) index was used as the single climatic index combining the temperature and precipitation. The results showed that the status of active Al was definitely dependent on the P-E index, representing a continuous Spodosol-nonallophanic Andisol-allophanic Andisol transition.