Giant hogweeds (Heracleum mantegazzianum and H. sosnowskyi) in Ukraine: distribution, ecological and coenotical features

The paper aims to study the distribution and communities of two giant hogweed species Heracleum mantegazzianum and H. sosnowskyi in Ukraine. This research was motivated by strong invasive trends, risks for native vegetation and a lack of data on giant hogweeds in Ukraine. We presented phytosociological tables of giant hogweeds communities, maps of their modern distribution in Ukraine, a dendrogram of similarity of the communities, phytoindicative evaluation, and proportions of diagnostic species in the syntaxa. According to our survey and literature data, there are 102 locations of H. mantegazzianum and 405 locations of H. sosnowskyi throughout most of Ukraine, except for the steppe zone, where the limiting factor is the arid climate. The amplitudes of both studied Heracleum species have a significant overlap in the factors of humidity, nitrogen, and salt regime. There are differences between the species in the factors of light, temperature and continentality. The amplitudes of the studied species are the widest for moisture and the narrowest range for soil acidity. Both species favour soils enriched in nitrogen. Based on the phytosociological survey, the species forms two distinct associations Urtico dioicae-Heracleetum sosnowskyi and Urtico dioicae-Heracleetum mantegazzianii and also occurs with lower abundance in communities belonging to 8 vegetation classes. The obtained data can be used to carry out preventive measures against the further spread of giant hogweeds in new habitats with varying degrees of anthropogenic transformation.