Tree-ring Chemistry and Growth Response to Experimental Watershed Acidification

AN ABSTRACT OF THE THESIS OF Nicole K. Jensen, for the Masters of Science degree in Forestry, presented on April 3, 2012, at Southern Illinois University Carbondale. TITLE: TREE-RING CHEMISTRY AND GROWTH RESPONSE TO EXPERIMENTAL WATERSHED ACIDIFICATION MAJOR PROFESSOR: Dr. Eric Holzmueller Forest ecosystems in the eastern United States are threatened by acid deposition rates that have increased dramatically since industrialization. We utilized two watersheds at the Fernow Experimental Forest in West Virginia to examine long-term effects of acidification on ecological processes. One watershed has been treated with ammonium sulfate (approximately twice the ambient deposition rate) since 1989 to simulate acid deposition while the other served as a control. Prior to treatment both watersheds were similar in age and species composition. Ten dominant overstory Prunus serotina and Liriodendron tulipifiera trees were selected and cored from each watershed to measure bolewood concentrations of elements essential for growth over time. In addition, changes in tree species basal area were analyzed utilizing 50 long-term growth plots established in 1990. Results of this experiment show lower calcium and magnesium concentration and increased acidic cation concentration in the treated watershed for both species indicating a negative treatment effect. These results were similar to that of a previous study conducted at the Fernow with periods of significant differences in cation concentrations between the treated and control watershed. Growth response, measured through relative growth rates of cored trees and changes in basal area from growth plots, was not as conclusive, but it did appear that treatment may be having a negative affect for both species during the last measurement of the growth plots. These results indicate a need for further research to understand the impact of long-term acidification so that sustainable forest management practices in areas affected by acid deposition may be developed