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Aims Understanding fine‐grain diversity patterns across large spatial extents is fundamental for macroecological research and biodiversity conservation. Using the GrassPlot database, we provide benchmarks of fine‐grain richness values of Palaearctic open habitats for vascular plants, bryophytes, lichens and complete vegetation (i.e., the sum of the former three groups). Location Palaearctic biogeographic realm. Methods We used 126,524 plots of eight standard grain sizes from the GrassPlot database: 0.0001, 0.001, 0.01, 0.1, 1, 10, 100 and 1,000 m2 and calculated the mean richness and standard deviations, as well as maximum, minimum, median, and first and third quartiles for each combination of grain size, taxonomic group, biome, region, vegetation type and phytosociological class. Results Patterns of plant diversity in vegetation types and biomes differ across grain sizes and taxonomic groups. Overall, secondary (mostly semi‐natural) grasslands and natural grasslands are the richest vegetation type. The open‐access file ”GrassPlot Diversity Benchmarks” and the web tool “GrassPlot Diversity Explorer” are now available online (https://edgg.org/databases/GrasslandDiversityExplorer) and provide more insights into species richness patterns in the Palaearctic open habitats. Conclusions The GrassPlot Diversity Benchmarks provide high‐quality data on species richness in open habitat types across the Palaearctic. These benchmark data can be used in vegetation ecology, macroecology, biodiversity conservation and data quality checking. While the amount of data in the underlying GrassPlot database and their spatial coverage are smaller than in other extensive vegetation‐plot databases, species recordings in GrassPlot are on average more complete, making it a valuable complementary data source in macroecology.

Questions What is the diversity and main vegetation types in mesic grasslands on the Iberian Peninsula? What are the main diagnostic species of each type? What are the main environmental gradients that drive patterns of species composition? To what extent does biogeography influence community diversity? Location Iberian Peninsula (Portugal and Spain, including the French Pyrenees). Methods Formal definitions based on the Cocktail method were used to establish a typology of mesic grasslands of the Arrhenatheretalia order. This method was applied to a stratified data set of 3485 relevés, also including other types of perennial grassland. Semi‐supervised classification based on the K‐means algorithm was used to assign almost 757 relevés into the vegetation types defined by Cocktail and to identify new ones. The types were compared by means of detrended correspondence analysis (DCA) using climate data, altitude and Ellenberg indicator values as explanatory variables. Results Fourteen ecologically well‐defined associations were distinguished in the Arrhenatheretalia order: five in the Arrhenatherion alliance, two in Triseto‐Polygonion and seven in Cynosurion. Soil reaction, summer aridity and altitude were identified as the most important determinants of species composition. These lithological and bioclimatic gradients are related to the biogeographic diversity of the study area, which is the main driver of community diversity in Arrhenatheretalia grasslands; it is more important than the management practices expressed in the concept of alliances. The classification and ordination analyses also showed a clear differentiation in community diversity according to biogeographic sectors (eastern Cantabrian‐Atlantic, Galician‐Portuguese, Carpetan‐Leonese, Pyrenean, Orocantabrian/western Pyrenean and Oroiberian/Catalan‐Valencian). In addition, moisture and nutrient content were more important than altitude in differentiating Arrhenatherion and Triseto‐Polygonion communities in the Pyrenees. Conclusions We suggest a simplification of the traditional classification of the Iberian Arrhenatheretalia grasslands. For this revised classification, we propose an electronic expert system with consistent rules for assigning vegetation observations to the associations defined, and a list of the diagnostic species of each vegetation type. These results can be applied to identify and monitor the hay meadows included in Annex I of the European Habitats Directive, taking into account the biogeographic context of the indicator species.

Aim The first comprehensive checklist of European phytosociological alliances, orders and classes (EuroVegChecklist) was published by Mucina et al. (2016, Applied Vegetation Science, 19 (Suppl. 1), 3–264). However, this checklist did not contain detailed information on the distribution of individual vegetation types. Here we provide the first maps of all alliances in Europe. Location Europe, Greenland, Canary Islands, Madeira, Azores, Cyprus and the Caucasus countries. Methods We collected data on the occurrence of phytosociological alliances in European countries and regions from literature and vegetation‐plot databases. We interpreted and complemented these data using the expert knowledge of an international team of vegetation scientists and matched all the previously reported alliance names and concepts with those of the EuroVegChecklist. We then mapped the occurrence of the EuroVegChecklist alliances in 82 territorial units corresponding to countries, large islands, archipelagos and peninsulas. We subdivided the mainland parts of large or biogeographically heterogeneous countries based on the European biogeographical regions. Specialized alliances of coastal habitats were mapped only for the coastal section of each territorial unit. Results Distribution maps were prepared for 1,105 alliances of vascular‐plant dominated vegetation reported in the EuroVegChecklist. For each territorial unit, three levels of occurrence probability were plotted on the maps: (a) verified occurrence; (b) uncertain occurrence; and (c) absence. The maps of individual alliances were complemented by summary maps of the number of alliances and the alliance–area relationship. Distribution data are also provided in a spreadsheet. Conclusions The new map series represents the first attempt to characterize the distribution of all vegetation types at the alliance level across Europe. There are still many knowledge gaps, partly due to a lack of data for some regions and partly due to uncertainties in the definition of some alliances. The maps presented here provide a basis for future research aimed at filling these gaps.

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