Chemical Modification of Rain Water by Alnus japonica Wetland Forest in Kiritapp Mire, Eastern Hokkaido, Japan

A survey was made of seasonal changes in pH and electronic conductivity (EC) of precipitation in Alnus japonica (Thunb.) Steud. forest in Kiritapp mire, Hokkaido, Japan. The average pH of throughfall and stem flow was higher than that of bulk deposition. When the pH of bulk deposition exceeded 5.5, however, pH of throughfall and stem flow was lower than that of bulk deposition. The EC of stem flow was always higher than throughfall, and that of throughfall higher than that of bulk deposition. The EC of stem flow was highest during the first defoliation period of A. japonica. On the other hand, the differences in the EC of throughfall and bulk deposition was very few just after the first defoliation period of A. japonica. This implies that the chemical properties of throughfall and stem flow are strongly affected by the phenology of the plants.