The purpose of this study was to investigate the influence of microbial biomass on the litter decomposition in relation to litter quality, litterfall, canopy leaf area and soil characteristics. The mean values for litterfall were 4245, 3510 and 2935 kg ha(-1) year(-1) for beech, fir-beech and fir stands, respectively. In the research area, beech stand has higher litterfall than fir, this may be attributed to high allocation of biomass to leaves, thus, makes them fall as litter more easily. One-year mass loss of litter decreased in this order: fir (23.6%) > fir-beech (17.2%) > beech (13.16%). Annual decay constant was significantly lower for beech (k=0.159) than fir litter (k=0.254), reflecting differences in nitrogen and lignin content between litter types (beech, 0.63% and 36.15%; fir, 1.40% and 28.10%). Fir litters have greater microbial biomass C content during the sampling period compared with beech and fir-beech litters. Microbial communities in fir litter were energetically more efficient (had a lower qCO(2)) with a higher C-mic/C-org compared to those in beech leaf litter. The results of this study indicate that admixed fir needles tended to speed up decomposition of beech foliage in these types of forest ecosystems.