DOMINANT AND SUBDOMINANT ASSOCIATIONS OF PLANT GROUPINGS IN THE WATERS OF THE RIVERSTYR WITHIN THE BORDERS OF RIVNE REGION

Abstract

The study deals with a geobotanical assessment of the existing hydrophilic flora of the river Styr within Rivne region. The research is based on the author’s monitoring studies. The paper outlines main point sources of river water pollution and their impact on the formation of the biotic component of the studied hydroecosystem. The author has carried out the analysis and assessment of aquatic and coastal aquatic vegetation in certain sections of the river Styr according to floristic, geobotanical, and coenopopulation research directions. It has been found that the species composition of plant communities in different sections of the river was not the same. Some species are characteristic only for a certain studied area. As a result of field research, the study outlines 125 species of higher vascular plants belonging to 75 genera and 38 families. The species composition includes 7 dominant families: Poaceae, Potamogetonaceae, Asteraceae, Cyperaceae, Polygonaceae, Ranunculaceae, Saliсaceace, which are 46.4% of the species composition. The author identifies such dominant genera as: Potamogeton, Salix, Juncus, Rumex and Carex; 8 species are adventitious plants. Other identified species represent the aboriginal flora of Rivne region. The paper highlights that the studied hydroecosystem of the river Styr within the region is characterized by the intensification of transformation processes associated with economic activity and climatic factors. The analysis of geobotanical characteristics has identified 14 plant groups. Within the middle reaches of the river Styr, the following groups are presented: Batrachietum circinati, Glycerietum maximae, Lemnetum minoris, Lemno minoris – Spirodeletum polyrrhizae Potametum perfoliati, P. pectinati. The coastal aquatic vegetation of the lower reaches of the river is represented by a poor hydrophilic flora. The author emphasizes on the fact that in a separate section of the lower reaches of the river (from the village of Zarichne and the village of Ivanchytsi), a rich and diverse species composition of hydrophilic flora has been identified. Cenopopulation studies of individual sites indicate the presence of 6 populations of rare species: Pulicaria vulgaris, Hippuris vulgaris, Batrachium rionii, Nymphaea candida (dead arm of river); Batrachium circinatum (the village of Verben); Potamogeton gramineus (the village of Ivanchytsi). The highly vulnerable species Batrachium rionii, which is included in the Red List of Hydroflora of Ukraine, was first found in the hydroecosystem of Rivne region. In total, 71.2% of species were found in the lower reaches of the river.