The non-native woody species of the flora of Ukraine: Introduction, naturalization and invasion

Abstract

The process of invasion, naturalization, dispersion and invasive activity of non-native woody species in 5 regional floras, 5 urban floras and over 30 floras of the protected areas is discussed. It has been established that 182 non-native species out of 95 genera and 45 families are currently at different naturalization stages in the spontaneous flora of Ukraine. In terms of life-forms, they may be divided as follows: trees – 41%, shrubs – 35%, trees/shrubs – 15%, lianas – 9%. Most species spread both via seed dispersal and the vegetative way – 56%, using only seed dispersal – 42%, only the vegetative way – 2%. According to the preliminary rating of species-wise invasive activity, 71 species (40%) have naturalized completely, among them 20 invasive species, including 12 transformer species, 29 potentially invasive species, and 22 naturalized species which demonstrate no invasive tendencies. The initial stages of invasion of 111 species are as follows: introduction – 9%, survival – 36%, adaptation of the reproductive sphere – 28%, establishment, formative of local populations – 27%. In terms of dispersion, non-naturalized species are divided as follows: rare – 45%, local – 16%, sporadic – 6%, unique – 12%, spreading under control beyond collections and expositions in botanical gardens and arboretums – 21%. Twelve transformer species, the greatest threat to local diversity, are Acer negundo, Ailanthus altissima, Amorpha fruticosa, Bupleurum fruticosum, Elaeagnus angustifolia, E. rhamnoides, Fraxinus ornus, Parthenocissus quinquefolia, P. vitacea, Robinia pseudoacacia, Rhamnus alaternus, Salix × blanda and 8 invasive proper species: Berberis aquifolia, Colutea orientalis, Daphne laureola, Prunus cerasifera, P. serotina, Quercus ilex, Viburnum tinus, Vitis vinifera. The list of alien species, most widespread in 50 regions of Europe, includes Robinia pseudoacacia (42 regions), Ailanthus altissima (40), Acer negundo (38), Prunus cerasus (34), Quercus rubra (34), Rosa rugosa (34), Prunus domestica (31). The mitigation of the impacts of these species on local biodiversity is possible via the restoration of local native plant communities, land use organization, strict selection of introduced species prior to the introduction, culture of planting management, preventive measures and extending awareness and sharing of information about plant invasions. Therefore, Ukraine’s spontaneous flora is notable for the active process of naturalization of non-native woody species with considerable involvement of invasive alien species. This is the first and preliminary evaluation of the invasive activity of woody species in Ukraine’s flora. The manifestations of the global tendency of increased involvement and invasive activity of alien woody species in domestic flora have been confirmed. These conclusions are also relevant for elaborating the system of preventive, containing and mitigating measures regarding plant invasions in Ukraine.