Characteristics of Brown Forest Soils Developed under Beech Forests in the Kinki and the Tohoku Districts with Special Reference to Their Pedogenetic Processes

概要

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Properties of sesquioxides, clay mineralogical composition, and charge characteristics of Brown Forest soils developed under beech forests in the Kinki (Ohdaigahara) and the Tohoku District (Hakkoda) were studied with special reference to their pedogenetic processes. The Brown Forest soils in the Kinki District were characterized by the translocation of free Al, formation of Al and/or Fe-humus complexes throughout the profile, and the predominance of 2 : 1: 1-2 : 1 intergrade minerals in the subsurface horizons, whereas those in the Tohoku District were characterized by the formation of allophane and no remarkable translocation of free Al oxides. This difference in the pedogenetic processes under the same vegetation was reflected on the amounts of Al released from primary minerals in relation to the amounts of organic matter accumulated. Major distinctive characteristics included the values of the Alp/Alo, the Fep/Feo, the Alo/Ald ratios, the Sio content, and the STPT-ZPC and ph(H_2O) values. Among these the values of the Alo/Ald ratio and/or the Sio content were found to be suitable indices for the differentiation of Brown Forest soils from Andisols in Japan in addition to the criteria used to define andic soil properties.