Ecological and phytogeographical differentiation of oak-hornbeam forests in southeastern Europe

The aim of the study was to establish the main types of oak-hornbeam (Carpinus betulus and Quercus sp. div) forests on the Apennines, Balkan peninsula and southern Alps and their correlations with the main ecological and phytogeographical gradients in the region. Furthermore, the comparison with the major types recognized in the traditional expert-based classification was done. 1676 releves of oak-hornbeam forests (alliances Erythronio-Carpinion, Carpinion moesiacum, Physospermo verticillati-Quercion cerris) from the area of the Apennines, Balkan peninsula and southern Alps were collected and entered in a Turboveg database. 508 releves remained after stratification and were classified with a Modified Two Way Indicator Species Analysis, which resulted in four main clusters that are phytogeographically interpretable, such as (1) southern Apennines, (2) northern-central and central Apennines, (3) central-southern Balkan and (4) north-western Balkan and southern Alps, further divided into subclusters. Pignatti indicator values calculated for releves of each subcluster were subjected to PCA in order to show the ecological relationships among subclusters, and the spectra of geo-elements were calculated to show the phytogeographical relationship between them. The diagnostic species combination was calculated by a fidelity measure (phi-coefficient) and presented in a synoptic table. Synsystematic classification of the elaborated groups is proposed.