Fertilization is a way of improving tree growth and thus profitability of forestry, however this practice may cause negative side effects, such as loss of biodiversity. Ground vegetation represents a major part of plant biodiversity in forest and it is sensitive to environmental changes. The aim of the study was to characterize a short-term impact of ammonium nitrate and wood ash application on floristic composition and species diversity in conifer and deciduous forests on drained mineral and

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... at soils. The study was conducted in 6 stands representing Myrtillosa, Myrtillosa turf.mel., Vacciniosa mel. and Vacciniosa turf. mel. forest types. The projective cover of each species was estimated visually, separately for moss, herb and shrub layer. Shannon diversity index, species richness and species composition were compared between the plots, where fertilizers were added, and control plots. Results show that species composition corresponds to the respective forest types regardless of the application of fertilizers. In all of the surveyed stands several nitrophilous species were more frequently observed and had a slightly larger projective cover in treatment plots, which could be explained by the impact of fertilization. Species diversity in the moss layer might have lowered as a result of fertilization, whereas no consistent patterns were observed for the herb layer. A repeated survey will show, if changes in ground vegetation persist longer.