Trace metal dynamics in decomposing leaf litter in habitats variously influenced by coal strip mining

Abstract

In a 20-year-old abandoned surface coal-mining area in eastern Ohio, fiber-glass litterbags containing thalli of two cryptogam species and leaves of 10 dominant tree species were set out in four vegetated stands influenced to varying degrees by the impact of strip mining. Decomposition rate of the litter types studied was correlated with the soluble carbohydrate, ash, and macronutrient fractions of the litter. No effects of strip mining on litter decomposition were apparent in any of the vegetated stands.Metal elements (Mn, Fe, Al, Cu, Zn, and Mo) were found to accumulate in decomposing litter with time. The degree to which dominant metals (Mn, Fe, and Al) were lost or accumulated with time was significantly correlated with the initial metal content of litter, indicating that a cation-exchange process is probably involved in observed metal-mobilization patterns.Leaching experiments using distilled water acidified to pH5.5 with H2SO4 to simulate rainfall in this region revealed that litter types which exhibited generally high decomposition rates or high initial amounts of metals tended to lose metal elements as a result of leaching. Metal-mobilization patterns evident from the litter-decomposition experiment indicated that the 1st month of litter decomposition results in metal loss owing to leaching.