Abstract
The relationships among the distributions of secondary air pollutants represented with oxidant index (OxI), precipitation in the growing season (ATP), and the distribution of declined Japanese cedar (Cryptomeria japonica D. Don) trees in the Kansai-Setouchi District were discussed. OxI is the average total number of hours per year from May to September in 1980 to 1984 for which oxidants exceeded the Japanese environmental standard of 0.06 ppm/hr and ATP is the average total precipitation from May to September in 1979 to 1987. The distribution of declined Japanese cedar comprised a large region coinciding roughly with the regions having an OxI more than 100. These regions tended to be inland areas suffering the effects of air pollutants transported long-range and coastal regions where air pollutants were circulated by the action of land and sea breezes. However, in spite of a high OxI, damage was less pronounced in those areas with an ATP more than 800mm. This suggests that a combination of high levels of secondary air pollutants and low levels of precipitation during the cedar growing season is a possible contributing factor to Japanese cedar decline.
