Prodomus of plants of the first floodplain terrace (arena) of the Dnieper River valley within the Dnipro-Orilsky Nature Reserve

Geobotanical surveys of the first floodplain terrace of the Dnieper River within the Dnieper-Orilsky Nature Reserve were conducted between 2013 and 2024. We recorded the presence of all vascular plant species on 289 sample plots measuring 4 × 4 m (Fig. 1). Projective species coverage was determined as a percentage. For the purposes of this study, we generally accepted infraspecific taxa as species (Mykhailyuk et al., 2023). Critical samples were collected and identified using microscopy. The sample plots were distributed across the entire study area and their exact location was determined using GPS (Garmin eTrex, ± 5 m). We tried to select samples that represented the entire variation of community types and plot sizes within the grid system. Plant taxonomy was based on Euro+Med Plantbase (http://ww2.bgbm.org/EuroPlusMed). Vegetation classification was performed using the TWINSPAN programme (Hill, 1979) . The accuracy of diagnostic species for clusters was determined using the phi coefficient with an accuracy threshold of 25 (for highly diagnostic species – 50), species with a frequency of occurrence > 25% were considered constant (for highly constant species > 50%), and dominant species were considered to be those with a projective cover > 10% (Lavrinenko et al., 2023) . The phi coefficient was calculated using the indicspecies library (Cáceres, 2013) . Syntaxes were identified to the association level; syntax names are given according to the pan-European Vegetation of Europe (Mucina et al., 2016) (Mucina et al., 2016) and the Prodromus of the Vegetation of Ukraine (Dubina et al., 2019) . The phytoindicative assessment of ecological factors was carried out in accordance with the synphytoindication methodology of Y.P. Didukh(Y P Didukh, 2011) , and calculations were made using the ideal indicator method(Buzuk, 2017; Zhukov & Kunakh, 2025) . For clarity, the scores were converted into equivalent physical values(Zhukov & Kunakh, 2025) . The botanical database is freely available in the Global Biodiversity Information Facility (GBIF) database(Lisovets et al., 2025) .