A comparative floristic and ecological analysis of herbage layers of spruce forests and clear-cut vegetation was performed in the National Nature Reserve Kněhyně-Čertův mlýn in the Moravian-Silesian Beskydy Mts affected by air pollution. Understory vegetation was studied in the following forests: in a spruce stand with partly opened canopy (Site 1), in a less damaged spruce monoculture, with more opened canopy (Site 2), in a thin, dying back forest on the top plateau of the Kněhyně hill (Site 4) and in clear cut area covered by grass vegetation (Site 3). The obtained data demonstrate that favourable light conditions support the spreading of ferns and grasses, particularly. The aboveground dry mass of the whole herbage layer ranged from 580 kg ha-1 (Site 2), over 2510 kg ha-1 (Site 4), and to 5711 kg ha-1 in the Site 3. Both greater concentration and accumulation of nutrients in plant biomass of herb layer were found in the Site 4 and in the Site 1. The highest values of amount of nutrients accumulated in aboveground biomass (e.g. 83.9 kg N ha-1, 6.9 kg P ha-1) were calculated for Calamagrostis villosa stands on the clearing (Site 3). The decomposition of C. villosa litter was substantially greater than was recorded for Athyrium distentifolium litter. In the course of the first year, 35.6% of leaf dry mass and 23.3% of culm dry mass of C. vilosa was decomposed. In the same period, 19.1% leaflets and 19.5% stalks dry mass was decomposed in the A. distentifolium stand in the Site 4. Average amount of dry mass of aboveground plant parts entering soil of C. villosa stand reached 170 g m-2, while in the A. distentifolium stand it was substantially lower (37 to 42 g m-2 per year). The release of Ca and Mg was slower from fern litter (24.6 and 69.4% respectively) than from C. villosa litter (42.5 and 76.8%). In comparison with the soil of spruce forests, the soil pH values and as well as the concentration of Ca2+ and Mg2+ ions were higher only under the influence of clear-cut grass vegetation.