Distribution of plant species Iris sibirica and its vegetation affinity in Slovakia

Iris sibirica is a threatened plant species of the Central European flora, but its distribution and vegetation ecology in Slovakia have not been studied so far. Therefore, we aimed to compile a complex chorology of this species and to analyse phytosociological plots with the species occurrence. Our results suggest that Iris sibirica occurs almost in the whole Slovakia, with two distributional centres situated in the south-western region (Pannonian bioregion) and in the southern regions of central Slovakia (Carpathian bioregion), but a higher proportion of recent records was identified in the Carpathians. Vegetation classification using the TWINSPAN algorithm divided 80 vegetation plots into 5 clusters. They were interpreted syntaxonomically as follows: i) Calthion palustris alliance, ii) Deschampsion cespitosae alliance, iii) Molinion caeruleae alliance, iv) vegetation of the successional stages and transitional status between wet meadows (Calthion palustris and Molinion caeruleae) and fens (Scheuchzerio palustris-Caricetea fuscae), and v) vegetation with a transitional status between hygrophilous, fen vegetation of the alliances Molinion caeruleae, Caricion davallianae, Caricion fuscae and mesic habitats. Variation in the species composition of vegetation plots, analysed using detrended correspondence analysis (DCA) and interpreted using Ellenberg indicator values for vascular plants, showed a shift along the first DCA axis from taxa typical for nutrient-rich and shaded but thermophilic sites to taxa of open and relatively cold habitats on nutrient-poor soils. The second DCA axis corresponded to the moisture gradient, which controlled the pattern of plant species richness.