Nitrogen dynamics in decomposing chestnut oak (Quercus prinus L.) in mesictemperate and tropical forest

This study examined nitrogen dynamics in decomposing Quercus prinus L. litt er, confined in litterbags, in two tropical forests (La Selva Biological St ation, Costa Rica and Luquillo Experimental Forest, Puerto Rico) and one te mperate forest site (Coweeta Hydrologic Laboratory, NC). Using regressions of %N in the decomposing litter against litter mass remaining. we demonstra ted similar concentrations of N at all sites when the amount of litter lost was 50%. By using naphthalene, an arthropod repellent, we examined the eff ect of microarthropods on the N fluxes in the litterbags. Microarthropods h ad little effect on the %N remaining. At La Selva, the presence of fauna re sulted in a marginally significant increase in litter nitrogen concentratio ns (p <0.06). At both tropical sites, there was a significant net immobiliz ation of N followed by N mineralization after four months. Although there w as a net immobilization of N at Coweeta, this lasted for a longer period an d the litterbags had not begun to mineralize N after 10 months. We suggest that the rapid accumulation of N in decomposing litter at the tropical site s during the first few months after leaf fall can result in the retention o f mobile nitrogen ions in soils. The subsequent mineralization, in later de composition stages, can make N available to trees during leaf hush. (C) 199 9 Elsevier Science B.V. All rights reserved.