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

This study examined nitrogen dynamics in decomposing Quercus prinus L. litter, confined in litterbags, in two tropical forests (La Selva Biological Station, Costa Rica and Luquillo Experimental Forest, Puerto Rico) and one temperate forest site (Coweeta Hydrologic Laboratory, NC). Using regressions of %N in the decomposing litter against litter mass remaining. we demonstrated similar concentrations of N at all sites when the amount of litter lost was 50%. By using naphthalene, an arthropod repellent, we examined the effect of microarthropods on the N fluxes in the litterbags. Microarthropods had little effect on the %N remaining. At La Selva, the presence of fauna resulted in a marginally significant increase in litter nitrogen concentrations (p <0.06). At both tropical sites, there was a significant net immobilization of N followed by N mineralization after four months. Although there was a net immobilization of N at Coweeta, this lasted for a longer period and 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 sites during the first few months after leaf fall can result in the retention of mobile nitrogen ions in soils. The subsequent mineralization, in later decomposition stages, can make N available to trees during leaf hush. (C) 1999 Elsevier Science B.V. All rights reserved.