Why does the abundance of native and invasive plants vary along rivers?
Riparian habitats are among those most prone to invasion by invasive alien plants due to their transitional nature, connectedness and history of fluvial and human disturbance. One species commonly found along rivers in Europe is Impatiens glandulifera (Balsaminaceae; EPPO List of Invasive Alien Plants), an annual species native to the western Himalayas and widespread and invasive within the EPPO region. In 2014, vegetation surveys were conducted along 20 lowland rivers in central Scotland where the presence of native and non-native species with their percentage cover were estimated. In addition, environmental data was collected at each site. The results showed that I. glandulifera is more sensitive to environmental conditions than dominant native vegetation. High soil moisture was a key determinant of I. glandulifera cover, having negative effects across the riparian zone. Spatially, I. glandulifera and dominant native vegetation responded differently to environmental conditions. Sites with steeper banks had less dominant native vegetation at the water’s edge, potentially favouring I. glandulifera cover through reduced competition. In general, greater abundance of dominant native vegetation presented a more invasion-resistant community. Maintaining dominant native vegetation at high abundance is thus key to preventing large monospecific I. glandulifera stands from forming.
Sources
Pattison Z, Vallejo-Marin M, Willby N (2018) Riverbanks as battlegrounds: Why does the abundance of native and invasive plants vary? Ecosystems, DOI: https://doi.org/10.1007/s10021-018-0288-3.