Effects of air pollution on the tree growth and vigor on the Japan Sea coast-a dendrochronological study-

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1.The effects of low level air pollution on various tree elements, including Cryptomeria japonica (Japanese Cedar), Pinus densiflora, Pinus thunbergii, and numerous other broad-leaved evergreen as well as deciduous trees, have been studied in the surrounding area of two thermoelectric power stations in Sakai-gun, Fukui Prefecture, on the Japan Sea side of central Honshu, Japan. The monitoring on the degree of visual injury of tree species in the whole area has been cotinued for 23 years since 1974, and in the present report the results of the field survey on the visual injury during 1995 and 1996 are compiled. There are no trees at present without any visual injury in this area, reflecting effects of air pollution. Morphological and phyiological symptoms were also examined.2.A dendrochronological study was also carried out to evaluate the effects of air pollution on the increment growth of Japanese Cedars. Conspicuous correlations between the levels of air pollution and decline in tree ring growth were recognized. The growth inhibition was also revealed by the tree ring analysis.3.Pine forests consisting of Pinus densiflora and P.thunbergii have been devastated by pine wilt disease for past 40 years in the large areas, especially in the southwestern part of Japan. In the present study we have examined radial growth of pine trees which were killed by pine wilt to elucidate how environmental stresses such as air pollution and/or acid deposition affect the disease in its development. Aged trees, about 100 years old or more, show reduction in radial growth in accordance with SOx increase in the air. However, such trees, even though survived under the stress, were abruptly killed when their growth recovered.