The relative tolerance of some Eucalyptus species to ozone exposure.
Surface ozone (O3) concentrations have proved to be difficult to control and regional O3 concentrations appear to be increasing in many parts of the world. Eucalyptus spp. are widely used as plantation trees in many regions that have Mediterranean, warm temperate and subtropical climates. An increased knowledge of the effects of tropospheric O3 on Eucalyptus trees may assist in the management of these plantations and choice of species. The study described here was set up to evaluate injury and measure growth reduction caused by O3 in 8 Eucalyptus species (E. camaldulensis, E. globulus, E. gomphocephala, E. grandis, E. marginata, E. microcorys, E. robusta, E. viminalis). Seven-month-old saplings were exposed to diurnally varied concentrations of 26 or 172 nl/litre O3 (7 h mean) 7 h/day, 5 days in every 14 days, for 18 wk. The plants were grown in open top field chambers fitted with rain excluders in Australia. Significant differences were found between the responses of different species. There was no visible injury or dry weight reduction in E. globulus. However O3 exposure caused a 30% weight reduction and 90% leaf injury in E. microcorys. E. gomphocephala also experienced a 30% weight reduction but no significant leaf injury. Hence for Eucalyptus plantations in regions with the potential for photochemical smog formation, such as some of the rapidly developing industrializing nations in Asia and South America, tolerance to O3 will need to be considered in selecting plantation trees.