Ozone sensitivity of plants in natural communities

Field fumigation studies conducted in grassland, oak, aspen, and conifer, communities established the injury threshold of prevalent plant species to ozone. Several important species, including Bromus tectorum, Quercus gambelii, and Populus tremuloides, were injured by a single 2-hours exposure to 15 pphm ozone. Over half the perennial forbs and woody species studied were visibly injured at concentrations of 30 pphm ozone or less. It is postulated that lower concentrations at prolonged or repeated exposures to ozone may impair growth and affect community vigour and stability. Continued exposure of natural plant communities to ozone is expected to initiate major shifts in the plant composition of communities.