Hydro-chemical cycle of forest ecosystem was investigated in the Norikura Highlands. The investigation period was from June to October, 2003 and 2004. The precipitated water that reached to the forest floor contained vastly different chemical constituents than those of the precipitation. The throughfall ion concentration was higher than precipitation. Generally it was in the following order: Ao-perocolation > 20 cm soil water ≒ 50 cm soil water. The concentration levels of NH4+ and NO3- in the soil water are lower than those in the throughfall, and HCO3- was higher in soil water. It is suggested that the transformation might be caused by microbes, such as nitrogen fixation, nitrification, and uptake by vegetation. The output flux of H+ from mineral horizon was lower than input flux by precipitation in both the coniferous site and the deciduous site. It showed the effect of acid neutralization. However, the internal cycling of base cations (K++Mg2++Ca2+) were more active in the deciduous site. Therefore, the activity of acid-neutralizing reaction was higher in the deciduous site than the coniferous site.
