We examined soil-forming processes along a climobiotic transect in the southern Hakkoda Mountains of northeastern Japan. The soils have developed on the same volcanic ashes that were deposited approximately 1000 and 5000 B.P., In Japan, chemical and morphological criteria based on the solid phase fail, in some cases, to distinguish between Spodosols and Andisols formed in volcanic materials. This problem also occurred along the transect examined in this study; however, collection and analysis of ecosystem waterflows, which included soil solutions, canopy throughfall, and precipitation, have allowed documentation of current soil-forming processes. Podzolization was found to be active in the subalpine Abies mariesii-Sasa kurilensis ecosystem. Iron, Al, and dissolved organic carbon were mobilized from the A horizon and became arrested in the Bw horizon. In contrast, andosolization dominated soil formation in the Miscanthus sinensis grassland ecosystem. This process was characterized by an accumulation of Fe, Al, and dissolved organic carbon in the A horizon with little subsequent leaching of these components into the B horizon. Formation of B horizons under both soil-forming processes appears to be dominated by in situ weathering rather than illuviation.
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