Soil carbon stocks estimation with reference to the degree of volcanic ash additions in Japanese forest soils

摘要

The objective of this study is to clarify the influence of volcanic ash addition on the soil carbon stocks and their accumulation process in Japanese forest soils. Volcanic ash additions to the soil were estimated based on the acid ammonium oxalate extractable aluminium (Alox) content, lithic fragment abundance and their vertical distribution patterns. The carbon in soil samples is controlled by Al-humus complex formation which is determined by the free Al generated from accumulated volcanic ash. Thestratigraphical relationship of volcanic ash accumulation horizons affected the vertical distribution of carbon. In addition, successive accumulation of volcanic ash on the soil surface leads to development of the soil surface horizon and to increased soil carbon stock. These influences to soil carbon accumulation due to the degree of volcanic ash addition to soil resulted in variable soil carbon stocks among soil types reflecting the degree of volcanic ash addition. Our results suggest that volcanic ash addition controls the soil carbon stock of these Japanese forest soils.