Formalized classification of semi-dry grasslands of central and eastern Europe

The European semi-dry grasslands belong to the most species-rich vegetation types of the northern hemisphere and form an important part of habitat mosaics of the forest-steppe zone. However, a comprehensive evaluation of compositional variation and phytosociological classification of these grasslands is still missing. For our syntaxonomic revision, we used a dataset of 34,173 vegetation plot records (relevés) from Central and Eastern Europe which were assigned to the class Festuco-Brometea using the diagnostic species listed in the EuroVegChecklist. To determine the diagnostic species of the orders, we used a TWINSPAN classification of the whole dataset. 15,449 relevés were assigned to the order Brachypodietalia pinnati, which corresponds to semi-dry grasslands. This subset was again classified with TWINSPAN. We established formal definitions for the following alliances: Mesobromion erecti, Cirsio-Brachypodion pinnati (incl. Fragario-Trifolion montani, Agrostio-Avenulion schellianae, Scabioso ochroleucae-Poion angustifoliae and Adonido vernalis-Stipion tirsae), Scorzonerion villosae and Chrysopogono-Danthonion. Another alliance, Armerion elongatae (= Koelerio-Phleion phleoidis p.p.), is transitional towards the class Koelerio-Corynephoretea and its status needs further evaluation. We also established formal definitions of all associations of the Mesobromion and Cirsio-Brachypodion within the study area. Associations were identified using (i) the TWINSPAN classification of the whole order, (ii) TWINSPAN classifications of regionally restricted data sets (usually all Brachypodietalia plots of one country) and (iii) existing national classification schemes. All formal definitions were written in the expert system language of the JUICE program. To get a more complete picture of the floristic similarities and gradients, we performed a DCA ordination of the associations. Our results show that meadow steppes of the forest-steppe zone of Eastern Europe are very similar to semi-dry grasslands of Central Europe