PROCEEDINGS: Index of Abstracts

RELATIVE NITROGEN MINERALIZATION AND NITRIFICATION POTENTIALS IN RELATION TO SOIL CHEMISTRY IN OAK FOREST SOILS ALONG A HISTORICAL DEPOSITION GRADIENT

Ralph E.J. Boerner-1 and Elaine Kennedy Sutherland-2

1-Department of Plant Biology, 1735 Niel Ave., Ohio State University, Columbus, OH 43210-1293. 2-USDA Forest Service, Northeastern Forest Experiment Station Delaware, OH 43015.

This study quantified soil nutrient status and N mineralization/nitrification potentials in soils of oak-dominated, unmanaged forest stands in seven USDA Forest Service experimental forests (EF) ranging along a historical and current acidic deposition gradient from southern Illinois to central West Virginia. Among these seven sites (that spanned 8.5° of longitude) soil pH and Ca₂⁺ decreased and soil organic C and soluble Al₃⁺ increased from west to east. In general, initial soil solution NO₃^- and NH₄⁺ was uncorrelated with longitude. The Fernow EF (WV), the easternmost site, was the exception to this trend. Soils from the Fernow had the highest concentrations of both NO₃^- accumulation, and the greatest N mineralization potential. Stepwise regressions of N mineralization rate, net NO₃^- accumulation, and proportional nitrification on initial soil properties produced models with overall r² of 0.705, 0.772, and 0.708, respectively. Rates of N turnover were positively correlated with initial NO₃^-, pH, and Ca:Al ratio and negatively correlated with soil solution Al₃⁺ concentrations. Differences in oak growth and mortality may be related to the differences in soil chemical status and soil N dynamics along these seven experimental forests.