Litter decomposition and nutrient dynamics in oak-hickory forests along a historic gradient of nitrogen and sulfur deposition

White oak (Quercus alba L.) leaf litter decomposition rates and patterns of N, S and P immobilization and release in decomposing litter were quantifie d in oak-hickory forests in the Ohio river valley along a long-term (severa l decades) bulk atmospheric deposition gradient from Illinois, Indiana to O hio. Historical data on deposition patterns between 1956-1985 showed that 3 0-y cumulative annual total (wet + dry) SO4-S concentrations were 19.9, 20. 8 and 23.9 kg ha(-1) y(-1) and total (wet + dry) N concentrations were 5.99 , 6.57 and 7.50 kg ha(-1) y(-1) in Illinois, Indiana and Ohio, respectively . In 1988-1989, amounts of total dry N deposition in Illinois, Indiana and Ohio were, respectively 2.71, 3.21, and 3.88 kg ha(-1) y(-1). Annual decay rates based on 19 months of decomposition data increased (p < 0.05) with in creased N deposition and were -0.294, -0.480, and -0.720, respectively. The decay rates correlated highly with both the total N concentration in the f orest floor (r(2) = 0.869, p < 0.0001) and the amount of total dry N deposi tion (r(2) = 0.999, p = 0.007). Nitrogen mineralization from the litter was highest in Ohio and lowest in Illinois. Immobilization of S and P occurred only in Illinois. Litter at both the Ohio and Indiana sites showed a net m ineralization of S and P but the rates were higher in Ohio. The results of the study suggest that atmospheric N inputs can affect litter decomposition and nutrient mineralization in oak-hickory forests in the lower Midwestern United States. (C) 1998 Elsevier Science Ltd. All rights reserved.