Ecological conditions affect plant species richness of beech forests along an altitudinal gradient

Spatial heterogeneity of biodiversity is linked to environmental gradients across landscapes. In forest vegetation, trees essentially affect the forest understorey flora, not only by forming the microecological conditions but also by their competitiveness. Here, we investigate the changes in taxonomic diversity along the altitudinal gradient in forests dominated by the strongly competitive, European beech (Fagus sylvatica), considering different ecological drivers important for vegetation diversity. The response of plant species diversity to changing characteristics is mostly non-linear or has an increasing trend. This reflects the specific environments of the studied region of Western Carpathians (Central Europe), where a high variability of geological substrates and the occurrence of base-rich rocks at higher altitudes increase species diversity. The beech cover, the geological substrate and the orography were found to be the most significant factors determining the diversity patterns. The increasing trend towards higher altitudes is significant on carbonate bedrock regardless of any other studied factors. The geological conditions multiply the number of species almost twice on carbonates compared to the communities on silicates. The Veľká Fatra Mts and Slovenský raj Mts are the plant diversity hotspots of beech forests in the Western Carpathians.