Nitrogen oxide fl uxes and nitrogen cycling during postagricultural succession and forest fertilization in the humid tropics. Ecosystems 4(1):67–84

The effects of changes in tropical land use on soil emissions of nitrous oxide (N2O) and nitric oxide (NO) are not well understood. We examined emis-sions of N2O and NO and their relationships to land use and forest composition, litterfall, soil nitrogen (N) pools and turnover, soil moisture, and patterns of carbon (C) cycling in a lower montane, subtropical wet region of Puerto Rico. Fluxes of N2O and NO were measured monthly for over 1 year in old (more than 60 years old) pastures, early- and mid-successional forests previously in pasture, and late-successional forests not known to have been in pasture within the tabonuco (Dacryodes excelsa) forest zone. Additional, though less frequent, measures were also made in a