Variation in morphological and biochemical O3 injury attributes of mature Jeffrey pine within canopies and between microsites

Crown morphology and leaf tissue chemical and biochemical attributes associated with ozone (O-3) injury were assessed in the lower, mid- and upper canopy of Jeffrey pine (Pinus jeffireyi Grev. & Balf.) growing in mesic and xeric microsites in Sequoia National Park, California. Microsites were designated mesic or xeric based on topography and bole growth in response to years of above-average precipitation. In mesic microsites, canopy response to O-3 was characterized by thinner branches, earlier needle fall, less chlorotic leaf mottling, and lower foliar antioxidant capacity, especially of the aqueous fraction. In xeric microsites, canopy response to 03 was characterized by higher chlorotic leaf mottling, shorter needles, lower needle chlorophyll concentration, and greater foliar antioxidant capacity. Increased leaf chlorotic mottle in xeric microsites was related to drought stress and increased concurrent internal production of highly reactive oxygen species, and not necessarily to stomatal O-3 uptake. Within-canopy position also influenced the expression Of O-3 injury in Jeffrey pine.