Response of growth, photosynthesis, and mineral nutrition of red spruce seedlings to ozone and acidic cloud deposition

Abstract

A field exclusion chamber study was established at a high elevation site in the Appalachian Mountains to determine the individual and combined effects of cloud water and ozone on the growth and physiological response of red spruce seedlings. Native seedlings from the study site, Whitetop Mountain, VA (1689 m), and seedlings grown from seed obtained from the Great Smoky Mountains in Tennessee were used in the study. Three replicates of the chamber treatments consisting of (1) exclusion of clouds and ozone, (2) exposure to ambient ozone with clouds removed, and (3) exposure to both ambient cloud and ozone were used in the study. Except for a statistically significant increase in current year needle biomass of native seedlings in treatments removing clouds or clouds and ozone, treatment effects were minimal. Periodic gas exchange measurements of seedlings taken throughout the growing season indicated that treatment-dependent effects on photosynthesis and respiration of both seedling types were few. Seedlings exposed to cloud moisture appeared to accumulate greater levels of N but not S. Increased nutrient leaching of foliar ions was not consistently observed, and soil exchangeable cations did not differ among treatments. These data do not indicate treatment-induced changes in seedling growth that would serve as primary cause(s) in recently reported red spruce decline at high elevations.