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Tham khảo tài liệu 'air pollution part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Air Pollutants Their Integrated Impact on Forest Condition under Changing Climate in Lithuania 143 Despite the statements that below the phytotoxic level no direct threat to vegetation from SO2 Bytnerowicz et al. 1998 Hjellbrekke 1999 or synergetic interaction between SO2 and Os could be expected Krupa and Arndt 1990 the presented data confirm our earlier findings that acidifying air compounds and their deposition are the key factors resulting in pine defoliation changes Guderian 1985 Takemoto et al. 2001 . They could explain from 23-28 variance of residual defoliation of pine trees Table 3 . The effect of peak Os concentrations was less significant 19.3 however the presented data verified the statement that O3 could reinforce their effects Guderian 1985 Takemoto et al. 2001 . Ozone increased the explanation rate of defoliation residual variability by air concentration of acidifying species and their wet deposition by almost 3-8 Augustaitis et al. 2007d . Drought especially during the vegetation period is often mentioned as one of the key factors resulting in defoliation changes. However there are contrary statements indicating that the effect of O3 and drought might counterbalance each other Zierl 2002 . Closed stomata protect foliage from the highest concentrations of O3. This contrary interaction could be explained by the fact that despite increase in O3 concentrations from north towards south Matyssek and Innes 1999 Karlsson 2002 O3 exposure in northern latitudes often leads to plants becoming more susceptible to injury than in southern areas Matyssek and Innes 1999 . Long bright days and high humidity in air and soil are typical for the situation in large parts of the Nordic countries Karlsson 2002 . The peak concentrations are typical in spring Utrainen and Holopainen 2000 . Not very high air temperature low vapor pressure deficits and sufficient soil water supply is characteristic for this period. Therefore in these areas O3 flux inside the leaves could be .
