NUTRITIONAL RESPONSE OF LOBLOLLY-PINE EXPOSED TO OZONE AND SIMULATED ACID-RAIN

The effects of ozone and simulated acid rain on the aboveground nutrie nt composition of loblolly pine (Pinus taeda L.) seedlings were studie d in a 2-year open-top chamber experiment in the Piedmont of North Car olina. Multivariate analysis of variance tests indicated significant o zone response in the 2nd year but no significant simulated acid rain e ffect in either year. No interaction among treatments was detectable. Seedlings responded to increasing ozone exposures with increasing conc entrations of nitrogen, phosphorus, potassium, magnesium, and calcium in the stem, branches, and foliage. The response of increased nutrient concentration was associated with decreased total biomass accumulatio n. The nutritional responses were most prominent in late season flushe s of foliage and are probably related to ozone-induced premature absci ssion of early-season flushes. High nutrient concentrations in the ste m, branches, and late-season flushes of trees exposed to elevated ozon e levels suggest retranslocation and slower growth rates resulted in b etter aboveground nutrient status and lower nutrient demand from the s oil.