Estimation of degree of volcanic ash additions for decision to distribution high functional soils in forest lands of Japan

通过在日本各地约800个样地采集的土壤样品中草酸提取铝的浓度和砾石含量，评价了火山灰对森林土壤的添加效果。据估计，20%的森林土壤是火山灰土壤，其中60%被认为多少含有火山灰。分布在火山附近的土壤中，火山灰添加率较高，而高火山灰土壤仅分布在远离火山的平坦或中等坡度的土壤中。结果表明，森林土壤中火山灰含量越高，碳储量越高。结果表明，火山灰的加入提高了日本森林土壤的碳含量。

The addition of volcanic ash to forest soil was evaluated by the concentration of Al extracted by acid oxalate and the gravel content in soil samples collected in ca.800 plots all over Japan. Twenty percent of forest soils were estimated to be volcanic ash soil and 60% of those were considered to be somewhat contained volcanic ash. The volcanic ash addition rate was high in the soils which were distributed in the area near volcanoes, while the soils having highly volcanic ash were only distributed on the flat or moderate slope in remote area from volcanoes. It was observed that the forest soils, having higher volcanic ash, showed higher carbon stock. We concluded that the addition of volcanic ash enhanced the carbon content in Japanese forest soils.