Abstract
In order to make sure the reliability of soil-water extraction (WE) method for chemical composition of forest soil solution, we compared WE method with vacuum lysimeter (VL) method, which was the most popular method in forest soil solution study. Sampling was done once a month from May in 1996 to March in 1997 in Japanese cypress (Chamaecyparis obtusa Endl) and Japanese cedar (Cryptomeria japonica D. Don) forests in Shiga town of Shiga prefecture. The total cation and anion concentrations estimated by the WE method showed always higher value than the VL method. An addition of deionized water to soil in the WE method presumably caused the movement of soluble constituents from the solid phase to the aqueous phase, and consequently cation and anion concentrations became higher in the WE method. Divalent cation concentrations in soil solution, especially Mg^<2+>, estimated by the WE method were lower than that by the VL method, whereas monovalent cations, especially NH_4^+ were higher in the WE method. The result suggested that cation exchange occurred between monovalent cations at the solid phase and divalent cations in the aqueous phase when deionized water was added to soil in the WE method.
