Spread of alien plant species in the habitats of the Ukrainian Forest Steppe

In order to assess the level of anthropogenic transformation of the vegetation cover of the nature protected areas located within the Ukrainian Forest Steppe, we have analysed the distribution of alien species in natural and anthropogenic habitats. All recorded species are represented in habitats shaped by human activity: dominated by phanerophytes, which included deciduous and coniferous woodlands as well as shrublands of Rhamno-Prunetea class. The same number of species was found in grassland habitats and is caused by the huge number of potential ecological niches as a result of the complex structure and also by the proximity of transportation networks and watercourses. Biotopes of chamaephytes and nanophanerophytes, though being represented in all the studied sites, often have a very narrow ecological amplitude and occupy small areas, making it difficult for alien species to spread. About one-third of species were recorded across at least three habitat types; such species may be considered eurytopic in their secondary ranges. Most widespread species were Fallopia convolvulus L., Vicia angustifolia Reichard, Ambrosia artemisiifolia L., Conyza canadensis (L.) Cronqist, Phalacroloma annuum (L.) Dumort. and Setaria viridis (L.) P. Beauv. At the same time, there was not a single species that would have occurred in all habitat types. In sum, agricultural lands and ruderal biotopes were highly invaded; three times less alien plant species occurred in woodlands, shrublands, grasslands and wasteland; and only small number of non-native species were restricted to continental water habitats.