Based on field and literature data, a classification scheme of grassland vegetation of Prut and Siret rivers within Ukraine was developed with ecological and floristic method of Braun-Blanquet. It includes 9 classes, 18 orders, 32 alliances, 59 associations. For the first time in Carpathian region a new association Violo declinatae-Agrostetum capillaris was described within Triseto flavescentis-Polygonion bistortae order, Molinio-Arrhenatheretea class. In general, 73% of the total number of orders, 56% of the total number of alliances and 28% of the total number of associations of 9 classes of vegetation, which are provided in the «Prodrome of the Vegetation of Ukraine» (2019), are represented in the study area.
The habitat affinity of grassland communities of Prut and Siret rivers basins within Ukrainewas analysed. It represented by 19 habitat types of fourth-level. Risks of their loss were assessed. For the first time, the characteristics of the habitat types were supplemented with information on presence of alien plant species in their composition, which is considered as one of the threats for their existence.
It was established that 1253 species of vascular plants were found in the grassland cenoflora, which belong to 499 genera, 112 families and 5 divisions. Species richness of grassland syntaxa at alliance level was evaluated and their comparative characteristics were provided. It is shown that 59% of their species diversity is concentrated within the 10 leading families. The highest species richness was recorded for the communities of Cirsio-Brachypodion pinnate, Triseto flavescentis-Polygonion bistortae, Cynosurion cristati, Festucion valesiacae alliances. It is established that the grassland coenoflora of the study region reflects the typical flora of the Palaearctic Fabaceae-type, which is also typical for the territory of Ukraine. At the same time, high positions of Cyperaceae family in the spectra of some alliances give it some features of boreality, and the Rosaceae family brings it closer to the Central European flora. Significant participation of the family Orchidaceae (47% of the spectra of the leading families of alliances) indicated the high conservational value of the grasslands of of Prut and Siret rivers basins within Ukraine.
It was found that 182 species from the grassland coenoflora of in the study region (23.7% of the total number of species) are listed as protected in red lists of different levels. The coenotic affinity was analyzed and the phytoindication assessment of the rare component of the grasslands’ flora of basins of Prut and Siret rivers was carried out. The greatest number and diversity of rare species was revealed in the communities of Calthion palustris, Triseto flavescentis-Polygonion bistortae, Cynosurion cristati, Festucion valesiacae, Cirsio-Brachypodion pinnatae, Caricion ferrugineae alliances. For 108 species from the Red Data Book of Ukraine (2009) information on coenotic affinity and ecological peculiarities at the alliance level has been supplemented. The information on the ecological amplitude range for 77 species from the Red Data Book was complemented or corrected, and for four of them (Crepis jacquinii, Fritillaria montana, Ligularia glauca, Poa rehmannii) the ecological values based on Didukh scales were calculated for the first time.
The level of transformation of grassland vegetation of basins of Prut and Siret rivers is determined with the modified coefficient of destruction. Based on the results of phytoindication assessment of communities and alien species, three-dimensional models have been developed to illustrate the relationships between the proportion of overlap of the species optimum zone, stress zone and community optimum zone, which can be used to predict the possibility of alien species introduction to natural phytocenoses and identifying potential communities for them. The presence of model alien species in communities of those alliances where there is a total overlap of tolerance zones of ecofactors by 80-100% is determined.
Conservation and preservation of grasslands is provided on the territory of 5 national nature parks (the area of grasslands in their composition is 7760.7 ha (6.86% of the total area of NNPs and 43.5% of the area of protected grasslands)), 20 reserves (9912.4 ha), 18 natural monuments (146.2 ha) and 4 protected tracts (52.4 ha).
Based on GIS technologies, approaches to the identification of «important botanical areas» and «hotspots of biodiversity» as a tool for assessment and monitoring have been developed. The use of the algorithm for creating thematic maps based on the available database allowed to identify squares with high concentration of rare species and plant communities not covered by protection, and to identify promising grassland areas for inclusion to the network of natural reserve fund.
