Woody alien species along the Danube river in Austria
Urban environments have become hotspots for invasive alien species due mainly to high levels of anthropogenic disturbance and increased propagule pressure. Although the proportion of woody invasive alien species (trees and shrubs) is relatively low (0.5 % and 0.7 % of the global number of woody species), they can cause significant negative impacts on native biodiversity and ecosystem services. Once established these species can be difficult and expensive to eradicate. A case study was conducted at three sites (urban, semi urban and rural) along the Danube river in and near Vienna. Four key questions were addressed: (1) What is the proportion of alien woody species in different sections of the Danube River in eastern Austria? (2) Which alien woody species are the most common ones? (3) How does alien woody species abundance change along the urban-rural gradient? (4) Which factors explain the distribution of alien woody species? At each site, 25 plots were established at the riverbank and data were collected on the occurrence of native and alien woody species. In total, 44 native and 25 woody species were recorded in the 75 plots. The highest proportions of alien woody species were found in the urban site and in several plots in the semi-urban site. The rural site had lower proportions of alien woody species. Five of the most common woody species observed during the study were alien species: Fraxinus pennsylvanica (Oleaceae), Populus x canadensis (Salicaceae), Acer negundo (Sapindales), Robinia pseudoacacia (Fabaceae) and Ailanthus altissima (Simaroubaceae: EPPO List of Invasive Alien Plants). Through modelling, it was shown that human population density is significantly correlated with the presence of A. negundo and A. altissima. Management practices should be prioritized for the alien woody species along the Danube to mitigate their negative impacts.
Sources
Wagner S, Moser D, Essl F (2020) Urban rivers as dispersal corridors: which factors are important for the spread of alien woody species along the Danube? Sustainability 12 https://doi.org/10.3390/su12062185