Soil pH and divalent cations after clear-cutting on a Japanese cypress plantation

Although Chamaecyparis obtusa reduces soil pH and cation levels, limited information is available regarding their alterations after clear-cutting. We examined the soil pH and base cations on the upslopes and downslopes of individual trees and stumps of C. obtusa at two distances (0.5 m and 1.0 m) and three depths (0–5, 5–10, and 10–30 cm) in intact- and cut-tree plots. The soil pH was higher in the cut-tree plot than in the intact-tree plot, indicating the recovery of soil pH after clear-cutting. The recovery was more evident in the surface soils (0–5 cm) of downslope areas (0.5 m) than in other soil depths, which implies that the recovery of soil pH was caused by the lack of H⁺ supply from stumps after clear-cutting. The results of H⁺ (in H₂O: water-soluble and KCl: exchangeable) suggested a lack of soluble H⁺ in the cut-tree plot. Soil Ca²⁺ and Mg²⁺ levels in the surface soil (0–5 cm) were 1.86-fold and 1.93-fold higher in the cut-tree plot than in the intact-tree plot, respectively, implying that the recovery of divalent cations after clear-cutting was caused by a reduction in cation loss through cation exchange with H⁺ derived from the stemflow. Collectively, soil pH and divalent cations were recovered after clear-cutting because the stemflow had ceased.