A Study on Decline of Japanese Cedars in Kauto Plain by Growth of Ring Width

The decline phenomenons of Japanese Cedars were studied from increment cores and soil collected from 150 trees at 15 siter in the Kanto plain. The growth inhibition was estimated as standarized ring index (SRI) with Kato's way (1988). And values of soil acidity were mesured. From 1960 to 1970s the mean value of SRI decreased, but by 1980 it tend to restpre and then decreased agein. This tendfncy was clearfr in south sites. A close association was observed between SRI and consistency of SO2 from 1970s to 1980s. Values of soil pH in these sites were almost lower.