Plant canopy effects on litter accumulation and soil microbial biomass in two temperate forests

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.