PATTERN OF SPECIES DOMINANCE AND FACTORS AFFECTING COMMUNITY COMPOSITION IN AREAS DEFORESTED DUE TO AIR-POLLUTION

Vegetation of mountain areas affected by SO2 pollution (Krusne hory Mt s., Czech Republic) was analysed using multivariate methods. Communiti es with prevailing species Calamagrostis villosa, a rhizomatous grass expanding into deforested sites, were sampled by Braun-Blanquet releve method. Canonical correspondence analysis was used to assess the effe ct of environmental variables (soil removal, deforestation, and shadin g). To test the effects of light, moisture, soil acidity and nitrogen, mean sample indicator values were correlated a posteriori with sample axes on ordination scores. Light, soil acidity, moisture, and site hi story (in terms of past deforestation and soil removal applied in recl amation procedures) were found to be the main factors responsible for the community composition. Nitrogen level had not a significant effect on the community composition. When analyzing the whole data set, i.e. including also remnants of natural spruce forests, light was the fact or affecting at most the composition of communities. Within the bare s pot vegetation, if treated separately, the highest variation was found along the soil acidity/moisture gradient. The effect of soil removal was only obvious at early successional stages. Species diversity incre ased with moisture and decreased with soil acidity. Species exhibiting S- and/or R-strategy are successful on extremely acid soils whereas f orbs present in bare spots appear to be supported by disturbances. .