Abstract
To clarify the relations of nitrogen mineralization and water-soluble ions of forest soils, in situ incubation method of core soil was used to measure nitrogen mineralization and the changes of water-soluble ions of forent soils in Japanese cedar (Cryptomeria japonica) and cypress (Chamecyparis obtuse) stands. Nitrogen contents in both cedar and cypress soils changed a little with the seasons. Rates of nitrogen mineralization were closely related with the soil temperature, but not with the soil moisture. Annual amounts of mineralized nitrogen in 020 cm soil were estimated to be 67 kg/ha and 77 kg/ha in the cypress and cedar, respectively, and were mainly NO3-N form. Soil EC and water-soluble H+ concentrations increased with nitrogen mineralization rates. Al3+ increased much more in cypress soil than in cedar soil, but Ca2+ and Mg2+ increased much more in cedar soil than in cypress soil. Both in cedar and cypress soil, water-soluble NO3-increased significantly with nitrogen mineralization rates, Cl-changed little, and SO42-obviously decreased. All of these changes in soil water chemistry may be attributed to the differences in soil pH and base cation contents of the two stands.
