Growth of Pinus Taeda L. Seedlings varies with Family and ozone exposure level

Abstract

Loblolly pine seedlings of five half-sib families were grown under ambient, subambient (approximately 0.6 × ambient), and elevated [ambient + 60 ppb O3 (120 μg m−3)] O3 levels for one growing season in open-topped chambers. Diameter and height of the seedlings were measured periodically over the growing season, and above ground and below ground biomass were determined at harvest. Significant genetic differences were found in above ground volume (D2H) 1 mo after 03 fumigation began and continued until harvest. Biomass of secondary needles and coarse and fine roots also differed significantly among families. Elevated O3 resulted in significantly decreased D2H and secondary needle biomass relative to seedlings grown in ambient air. Seedlings receiving subambient O3 levels were intermediate in size, but were not significantly different from seedlings fumigated at ambient O3 levels. Root and stem biomass did not differ significantly among treatments. A significant interaction of O3 and genotype was detected, suggesting that the response of loblolly pine to O3 is influenced by genotype.