XVI International Botanical Congess

A comparative study on the chemistry and sulfur isotopic composition of rainwater was made at the adjacent forest stands : Japanese ceder (Cryptomeria japonica) and Kojii (Castanopsis cuspidata). 1) the yearly averaged pH of precipitation was 4.5 with a range of 3.5 to 5.4. 2) the pH values of throughfall in Japanese ceder and Kojii stand were 5.2 and 4.9. 3) the stemflow pH were 3.8 and 4.5. 4) while the sulfate concentrations increased in the order of precipitation < throughfall < stemflow, their sulfur isotope ratios decreased in the order of precipitation > throughfall > stemflow. These results suggest that there exits the mechanism of nutrient enhancement in throughfall and stemflow by the leaching and washing out from leaves, branches and stem.