Kenophytes in different forest types of Ukraine.
The article aims to (1) describe the distribution of non-native species of vascular plants (only kenophytes, i. e. naturalized species introduced after the 15th century) in different types of forests and different biogeographical regions of Ukraine; (2) compare proportions of kenophytes in forests of different areas; (3) detect statistically significant changes in the occurrence of kenophytes over the last 80 years. The material consists of 2701 relevés sampled in 1990-2018. They were taken from Ukrainian phytocoenological publications and databases. In Ukraine, as in other European countries, the highest proportion of kenophytes (percentage of species number per relevé) is in floodplain forests (up to 9.1% in willow and poplar forests). The lowest proportion is characteristic for bog woods (0%) and most types of mountain forests. Among biogeographical regions, the highest values were found in the flatland areas of the Steppic region and the forest-steppe part of the Continental region. The most frequent species are Impatiens parviflora (predominantly in broadleaved woods, absent in relevés from the steppic biogeoregion) and Erigeron canadensis (pine woods on sand). Comparison with 1466 older relevés sampled in 1950-1989 allows us to make a conclusion that the proportion of kenophytes increased at least in one habitat type (oak-hornbeam forests).