GEO-BIOSPHERICAL INTERACTIONS IN REVEGETATION PROCESSES

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Field investigations were carried out in theree experimental basins in the drainage basin of River Otani, Shiga Prefecture, Japan, which drains the castern slope of the Hira Mountains. Hydrological analysis of the two major tributaries of River Otani has revealed that the cascade tank model for the mountain basins of northern Lake Biwa area applies well for these tributaries, except for much different parameters for top tank are needed for the tributary in which the humic soil has not well developed after the revegetation works.Structure of topsoil horizons was investigated in the experimental basin above the erosion front. Throughflow draining these horizons was also observed with recording tensiometers and gauging weirs. Although the rate of chemical weathering does not seem large, slow mechanical weathering has produced a thick topsoil mantle. The flow of water through the topsoil is likely to have dislocated the fine particles to cause local subsidence and to create a particular microtopography.Badlands at and below the erosion front were investigated with ground photographs and a digital terrain model. Quick denudation and retarded revegetation were found ascribable to the frost and thaw of surface soil. Topographic analysis has revealed that such slopes are commonly found in the steep and little rugged part of the fault scarps.