The forest gradual destruction caused by acid deposition has become a serious social problem in Europe and north America. Acid deposition is
also widely observed in Japan. Fortunately, in this country, there are few symptoms of forest destruction caused by acid deposition. The effects of acid deposition on terrestrial ecosystems are chronic and accumulative. So the author surveyed the pH and concentration of several ions in precipitation, throughfall and stemflow in Cryptomeria japonica and Quercus serrata forests in Toyama prefecture from 1988 to 1992. There is no relationship between the stemflow pH, the precipitation pH and the amount of precipitation. The pH values showed different ranges. The concentration of anions
(SO4 , NO3, Cl ) and cations (Ca++, Mg , Na+,
K+) in the stemflow were higher in Cryptomeria japonica than in Quercus serrata. Their amount increased especially during winter months (Oct. to Feb.). The concentration of anions and cations composing the stemflow changed seasonally, and differed among tree species. The soil acidification around trees was studied by grid sampling method. The soil pH is the highest around the stems of both Cryptomeria japonica and Quercus serrata, and decreases with the distance to the basis of the trunk.
Key words: acid deposition, Cryptomeria japonica, Quercus serrata, stemflow, soil pH.
Correspondence: Hiroshi Yasuda, Toyama Forestry and Forest Product Research Center, Yoshimine 3, Tateyama-cho, Toyama 930-13, Japan