Classification of Quercus trojana forests in southeastern Europe and Türkiye

This paper deals with Quercus trojana forest plant communities on the Balkan Peninsula, in Italy and Türkiye. Many syntaxa were described, but no unified syntaxonomic system based on a numerical analysis of vegetation has been proposed for the whole geographical range of Quercus trojana. Previous studies on Quercus trojana communities proposed to distinguish the alliance Quercion trojanae or the suballiance Quercenion trojanae. Here we aim to provide a revised syntaxonomic system of Quercus trojana forests in southeastern Europe and Anatolia. The analysed dataset included 246 relevés and 1011 species. Eleven associations and subassociations were identified using hierarchical cluster analysis (the Sørensen index as a dissimilarity measure and the Flexible Beta clustering method). Four subassociations were described as new: Quercetum trojanae chrysopogonetosum grylli, festucetosum callieri, seslerietosum autumnalis, and rutetosum graveolentis. Balkan and Italian communities belong to Quercetalia pubescenti-petraeae (the alliances Carpinion orientalis and Fraxino-Ostryion) and communities from Türkiye belong partly to Quercetalia pubescenti-petraeae (alliance Quercion crispatae) and partly to Querco-Cedretalia libani (alliance Querco vulcanicae-Ostryion carpinifoliae).