Multivariate Associations between Environmental Variables and the Invasion of Alien Plants in Floodplain Waterfront Parklands along the Nakdong River

Riparian zones are more susceptible to invasions of alien plant species than other ecosystems. Plant invasion is determined by multiple interacting factors, such as the characteristics of the invasive plants, the climate, disturbance patterns, and competition with native plants. To investigate the multiple interactions of environmental factors with regard to the invasion of an alien plant species, we considered a range of factors, including the topography, accessibility (or anthropogenic disturbances), competition with aquatic plants, and land-use history in 115 waterfront parklands along the Nakdong River. The waterfront parks were constricted after a river restoration project from 2009 to 2012. The most common alien plants were Oenothera odorata, Erigeron annuus, and Coreopsis lanceolate in our study areas. Alien plant areas were negatively associated with aquatic plant areas, which indicated that dominant alien plants mainly occur in drier uplands in the area under study. Accessibility (or anthropogenic disturbances) to waterfront parklands had a positive effect on the proportion of alien plant species. We assumed that frequent human visits and disturbances may increase the potential for invasions of diverse alien species. In addition, historic agricultural areas were positively associated with an invasion of an alien plants species. Our results suggest that invasions of alien species to waterfront parklands depend on multiple factors, including the characteristics of the alien species, the degree of accessibility, the topography, and historical land-use patterns.