Effects of ozone and simulated acidic precipitation on above- and below-ground growth of loblolly pine (Pinustaeda)

Loblolly pine (Pinustaeda L.) seedlings from two families differing in ozone sensitivity were exposed to four ozone concentrations (charcoal-filtered (subambient ozone concentration), nonfiltered (ambient ozone concentration), non-filtered × 1.7, and nonfiltered × 2.5) and three levels of acidic precipitation (pH = 3.3, 4.3, and 5.3) in modified open-top chambers for one growing season at Auburn, Alabama. Seedlings were planted in the ground in root-exclusion tubes that isolated root systems of individual seedlings. Foliage, stem, and root biomass, three-dimensional root surface area (root surface area × π; in cm 3 ), final height, and groundline diameter were recorded and analyzed. Foliage dry matter and root surface area decreased and root to shoot ratio significantly increased with increasing ozone concentrations for the ozone-sensitive family. There were no significant pH effects for this family. No significant differences in either ozone or pH treatments occurred for the ozone-tolerant family. The possible implications on long-term effects of ozone and acidic precipitation on loblolly pine growth are discussed.