Session

Palaearctic grasslands are known for the high species richness of vascular plants. So far, most of the records of different plot sizes up to 100 m2 were recorded in meso-xeric grasslands of the class Festuco-Brometea in the Carpathian region of Central Europe. In our study, we aimed to assess alpha diversity patterns among phytosociological classes of grasslands and other open habitats across taxonomic groups, plot sizes and regions of the Palaearctic. We extracted 121,633 vegetation plots of eight “standard” sizes (0.0001, 0.001, … 1,000 m2) with class assignment from the GrassPlot v.2.14 database. We obtained benchmarks of species richness of phytosociological classes for different plot sizes, taxonomic groups (vascular plants, bryophytes, lichens) and regions. For vascular plant species richness at 10 m2, the top ten classes were grasslands of different climate zones, with the Mediterranean therophyte-dominated grasslands on limestone (Stipo-Trachynietea) ranked first for the mean richness values, while temperate dry grassland and steppe vegetation (Festuco-Brometea) had the maximum richness values. The poorest group consisted of scree, coastal dune and saline classes. Mean species richness showed variation among regions, with patterns varying by class. We found new hotspots of maximum and mean species richness and demonstrated that mean species richness is generally higher in Palaearctic non-forest vegetation than previous studies have suggested. Our findings of new regional and syntaxonomic hotspots contribute to ecological theory and may spur the search for new records. Since high-quality data are still missing for many regions and syntaxa, GrassPlot calls for filling these knowledge gaps (https://edgg.org/databases/GrassPlot).