An Assessment of Effects of Air Pollution on the Ring Width of Japanese Cedars (Cryptomeria japonica D. Don) (II)

Relationships Between the Standardized Ring Index and the Pollution Levels of SO₂ and NO₂ in the Ambient Air at the Surrounding

Abstract

The effects of air pollution on the increment growth of the Japanese Cedars were studied in a surrounding area of thermoelectric power stations, located in Fukui Prefecture, Japan. The growth inhibition was estimated by normalizing the tree age and and meteorological conditions, i. e., standardized ring index (SRI).
A conspicuous growth inhibition was observed in the area within about 8km radius from the power stations. This agreed approximately with the calculated results based on the diffusion equation.
Conspicuous correlations were indicated between the standardized ring index and annual mean values of SO₂ and NO₂. When applying the multiple logistic regression analysis, about 70% of variation of the standardized ring index was accounted for by annual mean levels of SO₂ and NO₂. A possibility to estimate the levels of some air pollutants in the past years was also discussed, in relation to the dendrochronological method.