The objective of this study was to determine whether differences in canopy structure and litter composition affect soil characteristics and microbial activity in oak versus mixed fir-beech stands. Mean litter biomass was greater in mixed fir-beech stands (51.9t ha(-1)) compared to oak stands (15.7t ha(-1)). Canopy leaf area was also significantly larger in mixed stands (1.96m(2) m(-2)) than in oak stands (1.73m(2) m(-2)). Soil organic carbon (C-org) and moisture were greater in mixed fir-beech stands, probably as a result of increased cover. Soil microbial biomass carbon (C-mic), nitrogen (N-mic), and total soil nitrogen (N-tot) increased slightly in the mixed stand, although this difference was not significant. Overall, mixed stands showed a higher mean C-org/N-tot ratio (22.73) compared to oak stands (16.39), indicating relatively low rate of carbon mineralization. In addition, the percentage of organic C present as C-mic in the surface soil decreased from 3.17% in the oak stand to 2.26% in the mixed stand, suggesting that fir-beech litter may be less suitable as a microbial substrate than oak litter.