Ozone effects on nutrient resorption in loblolly pine

Abstract

A three-year study on the effects of chronic exposure to elevated ozone on loblolly pine (Pinustaeda L.) was conducted at a site in the Piedmont of North Carolina. Open-top chambers were used to control six levels of ozone, from 0.50 times ambient to 3.0 times ambient ozone concentration, on two open-pollinated families with suspected differences in sensitivity to ozone. Nutrient concentrations and contents were measured in fascicles obtained before and after abscission. Ozone strongly accelerated fascicle abscission and also tended to increase most nutrient concentrations in both pre- and post-abscission fascicles. There was, however, no significant impact of the ozone treatment on the amounts of nutrients resorbed during abscission. These data suggest that nutrient resorption associated with elevated ozone exposure followed a pattern more closely approximating accelerated senescence rather than premature abscission per se. The two open-pollinated families did not differ in nutrient resorption but did have isolated differences in the pre- and post-abscission fascicle concentrations.