• Energy Research

Abstract The effects of ozone exposure on species of an upland grassland were assessed. Thirty-three species from Snowdonia, North Wales, UK, were exposed for 10 weeks to a weekly episodic ozone regime in solardomes representing predicted future concentrations. Two solardomes were used as controls, with ozone added to charcoal-filtered air to give a continuous ozone concentration of 30 ppb (O 3 (30)). A weekly episodic ozone regime was applied to two other solardomes, with concentrations rising for 8 h per day to 80 ppb on day 1, 100 ppb on days 2 and 3, and 80 ppb on day 4; ozone concentrations remained at 30 ppb at all other times (O 3 (30+peaks)). The control and background ozone concentrations of 30 ppb were maintained throughout the night as well as during the daytime. During exposure to the episodic ozone regime, some species were sensitive to ozone and showed ozone-specific leaf injury symptoms (e.g . Carex echinata ) and/or premature senescence (e.g. Festuca rubra ) and/or changes in above-ground biomass (e.g. Armeria maritima ), whereas other species (e.g Holcus lanatus and Carex demissa ) showed no effects. Some species, although showing no effects during the 10-week ozone exposure, showed carry-over effects on biomass the following spring, after a winter period of ambient ozone exposure (e.g. Galium saxatile, Nardus stricta and Saxifraga stellaris ). The carry-over effects shown in this study indicate the potential ecological impact of ozone on semi-natural vegetation species and indicate the importance of longer-term studies on the effects of ozone on plants.

We review current knowledge of the processes by which ozone will cause injury and damage in crop plants. We do this both through an understanding of the limitations to ozone uptake (i.e. ozone being transferred from some height in the atmosphere to the leaf boundary layer and subsequent uptake via the stomata) as well as through the internal plant processes that will result in damage and /or injury. We consider these processes across the range of scales that are impacted in the plant, from cellular injury and damage (that can result in visible injury and alterations to photosynthesis and stomatal conductance) through to leaf level impacts on physiology and leaf senescence and ultimately to alterations in whole plant canopy and root systems that will affect biogeochemical cycling within the plant. We consider these processes from the viewpoint of developing crop growth models that are capable of incorporating key ozone impact processes within modelling structures that asses crop growth under a variety of different stresses. This would provide a dynamic assessment of the impact of ozone on crop growth within the context of other key variables considered important in determining crop growth and yield. We consider the ability to achieve this through an assessment of the different types of crop model (e.g. empirical, radiation use efficiency, and photosynthesis based crop growth models. Finally, we show how international activities such as the AgMIP (Agricultural Modelling and Improvement Intercomparison Project) could provide a network of crop growth modellers to assess the capabilities of different crop models to simulate the effects of ozone and other stresses to improve future regional and global risk assessments.