In this study, we attempt to evaluate the influence of forest or grassland use history on the acidity of Andosols in Nakaizu-town, Izu Peninsula. According to the analytical results, Andosols developed under the forest use tended to have stronger soil acidity and higher carbon content than the Andosols developed under grassland use. Acidification degree also differed between the Andosols developed under the broad-leaved forest and coniferous forest. Under the broad-leaved forest, the pedon with the short term forest use had low pH(H_2O) than the pedon with long term use. This may reflect on increase in the water soluble fr and organic acids. On the other hand, in the pedon developed under the coniferous forest, the soil acidity was higher under the long term forest use than short term use. This may be because of the poor litter decomposition and cation uptake to the trunk.
