OZONE EFFECT ON NUTRIENT RESORPTION IN LOBLOLLY-PINE

A three-year study on the effects of chronic exposure to elevated ozon e on loblolly pine (Pinus taeda L.) was conducted at a site in the Pie dmont of North Carolina. Open-top chambers were used to control six le vels of ozone, from 0.50 times ambient to 3.0 times ambient ozone conc entration, on two open-pollinated families with suspected differences in sensitivity to ozone. Nutrient concentrations and contents were mea sured in fascicles obtained before and after abscission. Ozone strongl y accelerated fascicle abscission and also tended to increase most nut rient concentrations in-both pre- and post-abscission fascicles. There was, however, no significant impact of the ozone treatment on the amo unts 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 th e pre- and post-abscission fascicle concentrations.