手入れ不足のスギ人工林の物質循環 : 地上部および土壌の養分集積量と養分還元量

The amounts of nutrient elements in aboveground, A_0-horizon and mineral soil and the amounts of nutrlent returned by litterfall and rainfall were measured in a 24-year-old Sugi（Cryptomeria japonica D.Don) stand at Sanbe Forest of Shimane University.
1. Aboveground biomass in the Sugi stand was 174.5t/ha. The dry weight of dead leaves and branches was 9.5t/ha. It was clearly owing to the insufficient management of stand. Nitrogen and phosphorus accumulated in leaves and potassium, calcium, and magnesium accumulated in stems.
2．The nutrient accumulations in A_0-horizon were comparatively little and the rates of nutrient accumulation were high in mineral soil.
3. The amount of litterfall was 4.37t/ha. The amounts of nitrogen and calcium returned by litterfall were larger than those of phosphorus and potassium. Especially, potassium was leached from dead leaves and branches by rainfall.
4. Therefore, the amount of potassium returned by rainfall was large.
5. Nitrogen and phosphorus accumulations concentrated to the aboveground, and potassium and calcium accumulations concentrated to the mineral soil. The amounts of nutrients in dead leaves and branches were 1.4-2.0 times as large as those of nutrient return, because of the death of branches owing to the insufficient management.