Abstract
Results of phytosociological studies conducted in the southern part of Opole Silesia within the Sudetes mountain range in 2014-2015 are presented. The main aim of our research was to confirm the occurrence of Viscario vulgaris-Quercetum petraeae Stöcker 1965, which had previously been noted in Poland only within the Central Sudetes Foothills in Lower Silesia province. Two additional sites of this extremely rare in Poland plant association were confirmed, located within the Opawskie Mts in Opole province. The association develops on steep slopes, near rocky outcrops, on southern or western expositions at altitudes between 350 and 410 m a.s.l. All plots of the association consists of several diagnostic taxa and the share of thermophilous plants is clear. The Viscario vulgaris-Quercetum petraeae is rather species poor forest phytocoenosis with the herb layer abundance shrink by a scree downslides. The most frequent taxa contributing to the sampled plots were: Luzula luzuloides, Galeopsis ladanum, Hieracium laevigatum, Lembotropis nigricans, Vaccinium myrtillus, Deschampsia flexuosa and Viscaria vulgaris. In all forest plots the Quercus petraea apparently dominates and shrub layer is scarce.