Experimental Studies on the Effects of Ozone on Growth and Photosynthetic Activity of Japanese Forest Tree Species

Abstract

Ozone (O3) is a main component of photochemical oxidants, and a phytotoxic anthropogenic air pollutant. In North America and Europe, the current concentration of O3 has been shown to have significant adverse effects on vegetation. In this review, we summarize the experimental studies on the effects of O3 on the growth and photosynthetic activity of Japanese forest tree species to understand the present knowledge and provide sound basis for future research toward the assessment of O3 impacts on Japanese forest ecosystem. Since the 1990s, several Japanese researchers have conducted the experimental studies on the effects of ambient levels of O3 on growth and physiological functions such as net photosynthesis of Japanese forest tree species. Although the sensitivity to O3 of whole-plant growth is quite different among the species, it was suggested that the current ambient levels of O3 in Japan are high enough to adversely affect growth and photosynthetic activity of Japanese forest tree species classified into high O3 sensitivity group such as Japanese beech. The N load to soil has been shown to reduce the sensitivity to O3 of Japanese larch and increase that of Japanese beech. To establish the critical level of O3 for protecting Japanese forest tree species, therefore, it is necessary to take into account the N deposition from the atmosphere. There is little information on the combined effects of O3 and other environmental factors such as elevated CO2 and drought on growth and physiological functions of Japanese forest tree species. Therefore, it is necessary to promote the experimental study and accumulate the information on the combined effects of O3 and any other abiotic environmental factors on Japanese forest tree species.

Keywords

• ozone
• japanese forest tree species
• growth
• photosynthetic activity
• critical level