Oak forests on loess are floristically one of the richest types of broadleaved forests and are among
the most threatened types of natural habitats in the Carpathian Basin. They are classified in several
communities in Hungary, Croatia and Serbia. These syntaxa are distinguished mostly on the basis of
traditional phytosociological methods without comparison across a larger geographical scale. The
recognition of some of these local syntaxa in the field, therefore, can be difficult, and the application
of their names to communities in other areas may be questionable. The goal of this study was to
develop an international typology for oak forests on loess based on a numerical analysis. A data set
of 437 phytosociological relevés (stands of 12 associations from three countries) was stratified and
270 relevés were analysed using multivariate statistical methods. Six types were distinguished:
Primula vulgaris type (xero-mesic to mesic sub-Mediterranean closed-canopy oak forests); Ruscus
aculeatus type (xeric to xero-mesic sub-Mediterranean type); Vinca herbacea type (xeric continental
open-canopywoodlands); Pulmonaria mollis type (xeric to mesic continental closed-canopy forests);
Corydalis cava type (mesic closed-canopy oak forests in nutrient-rich habitats); and Stellaria
media type (xeric to mesic oak forests in nutrient-rich habitats). The vegetation types identified are
related to syntaxa traditionally recognized by phytosociologists. Our analysis did not support the
distinction of some associations with local distributions. The geographical distributions of the two
main forest types exhibited a gradient-like pattern in a north-east–south-west direction. The dry
continental forest steppe woodland is mainly distributed in the north-eastern part of Hungary,
whereas the xero-mesic sub-Mediterranean forests are restricted to the southwestern and southern
part of our study area. This pattern corresponds to a climatic gradient from the North Hungarian Mts
to north-eastern Croatia and northern Serbia
