Effect of Air Pollution on Annual Ring Width of Pinus densiflora Sieb. et Zucc. and Cryptomeria japonica D. Don, in Kitakyushu City

Abstract

We investigated the effect of air pollution on annual ring width of two conifer species, namely, Pinus densiflora Sieb. et Zucc. and Cryptomeria japonica D. Don, in Kitakyushu City.
Six forest stands were chosen to collect their increment cores. Four stands were located in Kitakyushu City, where an intensity of air pollution was high in the late 1960s, and it has decreased since 1970. The rest two stands were located in Mt. Hikosan, 50 km south of the city, as the control sites. We obtained the ten to sixteen cores at each stand. The cores have ca. 50 years annual rings from 1941 to 1990.
Annual ring width was converted to normalized indices. Then the indices were analyzed by linear multiple regression to evaluate the effect of air pollution upon them. Data for climatic factors were obtained from the records of seasonal precipitation and temperature for 50 years (1941-1990), and data for air pollution were obtained from records of sulfur oxides and dust fall at Kitakyushu City for 31 years (1959-1989).
The regression of annual ring indices on the air pollution factors alone or on the climatic factors alone was compared with that on both of these factors in terms of determination coefficients. The results showed that both the air pollution factors and the climatic factors affected the annual ring width with the effect of air pollution greater than climate.