Analysis of variance (ANOVA) of a completely randomized block design (SAS 9.3, SAS Institute Inc. Cary, NC, USA) was used to assess significant differences in soil N2O and CO2 flux rates among the four antibiotic treatments. We also used ANOVA of a split plot design with substrate treatments as the whole-plot factor and sampling times as the split-plot factor to evaluate significant differences in soil N2O and CO2 flux rates, fungal and bacterial contributions to soil N2O and CO2 flux rates, and the abundances of soil bacteria, fungi, and bacterial denitrifiers among substrate treatments. Further, correlation analysis was used to examine the relations between bacterial and fungal contributions to N2O and CO2. All data sets were tested for normal distribution and homoscedasticity. If data were non-normal and/or heteroscedastic, they were log transformed prior to statistical analysis