Foliar nutrient contents in tree species of the Atlantic rain forest as influenced by air pollution from the industrial complex of Cubatao, SE-Brazil

Air pollutant emissions from the industrial complex of Cubatao, SE-Brazil, have caused a severe decline of the Atlantic Forest in that region. In orde r to test the influence of air pollution on the mineral nutrition of trees, leaves of the native species Tibouchina pulchra Cogn. (Melastomataceae), M iconia pyrifolia Naud. (Melastomataceae) and Cecropia glazioui Snethl. (Cec ropiaceae) were sampled during winter and summer seasons at four sites with different pollution characteristics. Additionally, saplings of T. pulchra were cultivated in uniform soil and exposed to ambient air at the same expe rimental sites for periods of 16 weeks. In both kinds of leaf samples, the concentrations of macro-nutrients were determined and nutrient ratios calcu lated. In leaves of mature T. pulchra and C. glazioui growing at polluted s ites N, P and S levels were significantly higher than in trees from the ref erence area. With respect to K contents, C. glazioui showed an increase, T. pulchra a decrease when compared to reference trees. Mg and Ca concentrati ons generally did not exhibit great variations. As a consequence of the cha nges in mineral contents nutrient ratios (N/K, N/Ca, S/K, S/Ca) shifted to higher values. The results of the exposure experiments together with data o n pollutant concentrations in ambient air and rain water demonstrated that atmospheric deposition to the plants and pollution effects on the soil chem istry are the main reasons for the observed alterations in mineral nutritio n of trees.