Plant cover of the Szum river valley (Roztocze, South-East Poland)

The break section of the Szum river and the mouth part of its left tributary, Miedzianka (Roztocze, SE Poland) were the object of the research conducted in the years 1999-2001. The aim of the study was to establish the abiotic conditions of the diversity of vegetation and the richness of vascular flora in a small lowland river valley. A real vegetation map was drawn in the scale 1:5000. The syntaxonomic classification of plant communities and habitat trophism were established on the basis of 120 phytosociological relevés and 160 soil samples, respectively. On the area of barely 35.4 ha identified were 48 plant associations and communities representing 11 phytosociological classes, among them habitats protected in Poland (16 types) and important at the EU scale (3). There were found 378 species of 72 families, including: 21 species under strict protection, 9 under partial protection, 25 plants threatened on the regional scale, and 2 included into the Polish Red Data Book. Most of interesting species and non-forest communities occur in the parts of the valley above and below a landscape reserve 'Szum', established in 1958, covering presently 18.17 ha. The greatest floral richness was found in the peatbog-meadow complexes (Phragmitetea, Molinio-Arrhenatheretea, Scheuchzerio-Caricetea), in bog-alder forests and willow bushes (Alnetea glutinosae), and streamline ash-alder carrs (Querco-Fagetea, Alno-Ulmion), while the smallest - in the pine and poorer upland mixed fir forests (Vaccinio-Piceetea). Vascular flora appears to be the richest in the sections of the valley where the bottom is overgrown by non-forest communities. The results of the study indicate that it is necessary to enlarge the area of the existing nature reserve.