Effects of air pollution on the Central and Eastern European mountain forests

摘要

Ambient ozone (O_3) concentrations in the Northern Hemisphere have gradually been increasing during the past 100 years, from about 10 ppb in the end of the nineteeth century to the present-day background summer-time average concentrations of typically about 40-50 ppb in remote locations (Guiherit and Roemer, 2000). Even higher levels of 50-60 ppb O_3 occur in the mid-latitudes where anthropogenic emissions of O_3 precursors are high (Brasseur et al., 2001; Lefohn et al., 2001). In Central and Eastern Europe (CEE) since the late 1980s, while levels of industrial pollutants have been declining, there has been an increase of ambient O_3. It is expected that this trend will continue due to the long-range transport of O_3 from Western Europe and local generation of O_3 precursors. Ozone is a well-known phytotoxic agent causing damage to vegetation (Krupa and Manning, 1988) and indirectly increasing the phytotoxic effects of other air pollutants, especially sulfur and nitrogen oxides (Guderian et al., 1989). Various phytotoxic O_3 effects have been observed in parts of Europe, including visual symptoms of injury on many native species (Bussotti and Ferretti, 1998;-VanderHeyden et al., 2001; Manning et al., 2002; Novak et al., 2003), and reduction of growth of key forest tree species (Karlsson et al., 2004). The recently observed deterioration of forest tree crown condition in Poland, Czech Republic and Slovakia (Elvingson, 2000) indicate that elevated levels of ambient O_3 (including gradually increasing high background concentrations), as well as other abiotic and biotic stressors (especially drought and bark beetle infestations), contribute to forest decline.