The magnitude of exchageable Ca accumulation and other changes in soil properties were assessed for the soils beneath 4- to 180-year-old cryptomeria stands (Cryptomeria japonica D. Don), and for the soils beneath 4- to 100-year-old Japanese cypress stands (Chamaesiparis obtusa S. et Z.) growing on the similar thick humic Andosols in the same region. 1) In the soils beneath cryptomeria stands more than 18 years old, the mass of A_0 horizon was held constant. Calcium and other bases were supplied through the decomposition of cryptomeria litter. Exchangeable Ca has increased rapidly in the upper layer (0-5 cm depth) beneath cryptomeria stands of 35 years or above. The accumulation rate of exchangeable Ca in the upper layer reaches to constant after 45 years, and the layer of exchangeable Ca accumulation moves to the lower layer. An increase in the content of exchangeable Ca results in an increase in both pH and base saturation. 2) In the soils beneath Japanese cypress stands, soil organic matter content has accumulated at a nearly constant rate after 18 years old in the upper layer (0-5 cm depth). The reason for a high organic matter content may be due to the permeation of finely dispersed and undecomposed scale of cypress to the A horizon. Other soil characteristics beneath cypress stands differed markedly from those beneath adjacent cryptomeria stands ; exchangeable Ca was not accumulated, and pH and base saturation were much lower. 3) Considerably high content of exchangeable Ca has been observed in the lower layers (60 - 100 cm depth) beneath 4-year-old cryptomeria and Japanese cypress stands ; these stands were regenerated after the clear cutting of about 60-year-old cryptomeria stand.