Distribution and eco-coenotic patterns of the forest orchid Epipactis pontica in Slovakia

The present study is aimed at characterising the ecological niche of a typical forest orchid (Epipactis pontica) in Slovakia. Vegetation-environmental data were collected across mountain ranges and their foothills in the Western Carpathians in 2011. Numerical classification was performed to delimit the main forest vegetation types and a linear mixed effect model was applied to reveal differences between plots with versus without E. pontica. This endangered species of Slovak flora grows in thermophilous turkey oak forests (Quercion confertae-cerris), mesophilous broad-leaved mixed oak-hornbeam forests (Carpinion betuli), but most stands correspond to the acidic (Luzulo-Fagion sylvaticae) and mesotrophic beech forests (Fagion sylvaticae). Principal component analysis supported the floristic separation of plant communities and showed some significant vegetation environmental relationships. E. pontica prefers forests with closed canopy (mean canopy openness: 8.5–15.1%) occurring especially on slightly acidic (soil reaction: 4.48–5.65) and nutrient-poor soils (soil conductivity: 43.1–72.6 μS/cm). The proposed Ellenberg indicator values for light (4), temperature (5), continentality (4), moisture (5), soil reaction (6) and nutrients (5) follow species composition pattern of vascular plants in Slovak phytosociological relevés with E. pontica occurrence. They are also in accordance with its habitat conditions and ecological requirements in other parts of its range. The linear mixed effect model did not confirm any environmental peculiarity of plots with the presence of E. pontica at a microscale level and this result was consistent across the studied sites.