We measured fluxes of N2O, CH4and CO2from control and urea-nitrogen fertilized soils of a mature slash pine (Pinuselliottiivar.elliottiiEnglem.) plantation in Alachua County, Florida. The fertilization did not affect CO2emissions, but significantly increased the emissions of N2O and lowered the uptake of atmospheric CH4. Daily average N2O emissions from the fertilized soils were 8–600 times higher (12–74 μg N2O-N•m−2•h−1) than daily average N2O emissions from control soils (0.02–4.0 μg N2O-N•m−2•h−1). Daily average CH4uptake by the fertilized soils were 5–20 times lower (0.001–0.007 mg CH4-C•m−2•h−1) than daily average CH4uptake by control soils (0.015–0.035 mg CH4-C•m−2•h−1). We also measured the relative activities of the bacteria populations that were responsible for CH4oxidation in the control and fertilized soils. Results from these measurements suggest that fertilization shifted the relative activities of the CH4oxidizing bacteria from those dominated by methanotrophs in the control soils to those dominated by nitrifying bacteria in the surface (0–2 cm) of the fertilized soils. The shift in relative activities of these bacteria may have been responsible for the lower CH4uptake by the fertilized soils.