Classification of the class Molinio-Arrhenatheretea in the forest and forest-steppe zones of Ukraine.

Aims: This paper reviews the classification of mesic grassland vegetation (phytosociological class Molinio-Arrhenatheretea) in Ukraine, and integrates the units recorded into the common European syntaxonomical system of the Molinio-Arrhenatheretea class. It also proposes solutions to a number of issues that cause conflict between the classical Central European concept of the Molinio-Arrhenatheretea class and its traditional syntaxonomy in the former USSR. Location: Forest and forest steppe zones of Ukraine. Methods: I analysed 2,105 relevés originally assigned to the Molinio-Arrhenatheretea class using the European Expert System and Kmeans clustering. The units were evaluated for quality and internal homogeneity using Sharpness index and Average Whittaker beta-diversity. I determined the diagnostic species of the vegetation units using calculations of their fidelity based on a phi-coefficient. The environmental assessment of the units follows the Didukh indicator values. Results: I interpreted the resulting vegetation units as alliances of the Braun-Blanquet system (Agrostion vinealis, Arrhenatherion elatioris, Cynosurion cristati, Deschampsion cespitosae, Molinion caeruleae, Potentillion anserinae and Calthion palustris) based on a complex of diagnostic species. I also analysed the distribution of the communities of the identified alliances in the study area, revealing their ecological features. Conclusions: The use of modern phytosociological methods in this study to analyse geobotanical data collected over a long period and a large area covering the whole range of the Molinio-Arrhenatheretea class in the country, clarified a number of controversial issues previously related to the lack of coordination between the Central and Eastern European phytosociology.