Calcium accumulation alleviates soil acidification in Japanese cedar (Cryptomeria japonica) stands

Abstract

Larger amounts of exchangeable calcium (Ca2+) accumulated in the surface soil in an older Japanese cedar (Cryptomeria japonica) stand, compared with the younger stand. We estimated the Ca2+ accumulation rate and examined the difference in the amounts of exchangeable Ca2+ based on the Ca2+ fluxes. Samples of soil percolated water were taken using stainless tension-free lysimeters at different depths (under 0 horizon, 10,40, and 80 cm). Mobilization of base cations was controlled by total acid production. Proton load associated with N transformation was an important factor for the mobilization of base cations, especially for bivalent cations. Base cations tended to be mobilized in the 0 horizon and immobilized in soil horizons. The amount of Ca2+ supplied from the 0 horizon exceeded the amount recorded at the depth of 0–10 cm in the older Japanese cedar stand, resulting in the immobilization of 120 mmolc m−2 yr−1 of Ca2+ from October 2000 to September 2001. The amount of immobilized Ca2+ in the soil horizons in each period depended on the mobilized amounts in the 0 horizon. Lower amount of supplied Ca2+ in the 0 horizon and mobilization at the depth of 0–10 cm in the younger stand contributed to the difference in the amount of exchangeable Ca2+. Mobilization of base cations in the 0 horizon alleviated the loss of base cations in soil under Japanese cedar stands and contributed to the suppression of soil acidification.