Soil physicochemical properties in Kahoku Experimental Watershed No. 2

Abstract

Focusing on microtopography units, we examined the physicochemical properties of soils within a small watershed (Kahoku Experimental Watershed No. 2) in the northern part of Kumamoto Prefecture. This watershed is part of the Forestry and Forest Products Research Institute Flux Observation Network. Regarding general physical properties, our results revealed that bulk density was high, while total porosity was low, particularly in the B horizons. Saturated hydraulic conductivity was greater at the mid-slope than at the ridge. Effective porosity, which contributes to the soil’s water storage capacity, was generally low, with small porosity being especially low. In terms of chemical properties, our findings indicated that the soil had low pH and exchangeable cation concentrations, classifying it as acidic and oligotrophic. Additionally, both carbon and nitrogen concentrations were considerably lower than the national average, suggesting that the soil was more weathered than in other areas of Kyushu.