Because of precipitation serves as a major vehicle of nutrient input into the forest ecosystem, the accurate measurement of its volume and ion concentration is of prime importance in an evaluation of any bio-geochemical cycle. Therefore, chemistry of the precipitation and throughfall of forest ecosystem was investigated in the Norikura Highlands. The investigation period was from January, 2003 to October, 2006. The throughfall volume in growing season and dormant season were 86 % and 93 % of the precipitation volume. Throughfall pH increased with increasing K + concentration showed that H + was held within the canopy by cation exchange reaction. And the concentration level of K + , Mg 2+ and Ca 2+ in the throughfall was much higher than that in the precipitation. It was the cause of canopy leaching. In growing season, proportions of canopy leaching of K + , Mg 2+ and Ca 2+ were 95 %, 70 % and 43 % of the throughfall deposition respectively. At Coniferous site, the flux of dry deposition was higher in dormant season than growing season. It is suggested that aerosol of the atmosphere and leaf area might be influenced.
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 + +Mg 2+ +Ca 2+ ) were more active in the deciduous site. Therefore, the activity of acid-neutralizing reaction was higher in the deciduous site than the coniferous site.
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