The present study concerns the floristic-sociological classification of the floodplain meadow vegetation of the Seym and the Dnieper rivers (within the eastern part of Polissya of Ukraine). The relevé matrix was clustered using the DRSA (DistanceRanked Sorting Algorithm) method, and the Ochai fidelity index was applied for species sorting and allocating the differentiating species. Species composition of the syntaxa has been evaluated using the phytoindication method and an assessment of shares of species of different classes of vegetation (phytosociological spectrum). These variables were used for phytocoenological characterization and to fit with the NMDS ordination axes using the multiple regression approach. We identified 8 associations of psammophytic, mesic and temporarily wet meadows which were assigned to 3 alliances and 3 orders of the MolinioArrhenatheretea class. Syntaxa were characterized using a unified scheme: habitat type according to EUNIS classification, ecological and synmorphological traits, distribution, and anthropogenic transformation. Comparative floristic tables were constructed taking into account the synoptic columns of the studied associations and western syntaxa including the holotypes. Four associations have been introduced, such as Galio molluginis-Festucetum pratensis ass. nova in the alliance Arrhenatherion, and Veronici longifoliae-Iridetum sibirici ass. nova, Poo trivialis-Alopecuretum arundinaceae ass. nova, Dactylorhizo incarnatiCaricetum nigrae ass. nova in all. Deschampsion cespitosae.

Floodplain . Meadow vegetation . Molinio-Arrhenatheretea class . Syntaxonomy . Ukraine