Ambrosia artemisiifolia along roads in Germany
Ambrosia artemisiifolia (Asteraceae: EPPO List of Invasive Alien Plants) is native to North America and is a widespread invasive alien plant in the EPPO region. A. artemisiifolia is an annual weed which competes strongly with crop plants for water and nutrients. It is a very prolific seed producer (a plant typically produces 30 000- 40 000 seeds per year and can produce up to 100 000) and seeds can remain viable for 5-14 years. Habitats where it occurs include waterways, wasteland, railways and roads. Roads in particular have been shown to facilitate the spread of invasive plant species. Construction work, road maintenance and private vehicles can all act to spread plant propagules and factors like the size of the road and the volume of traffic can act to increase the movement of invasive plants. In Brandenburg (Germany), roadside populations of A. artemisiifolia were mapped along four road types, defined according to traffic volumes over five years (2008-2012), and habitat mapping was conducted in 2012 to define unshaded sites and shaded sites where the latter can limit the establishment of A. artemisiifolia. Unshaded roadside locations were further divided into disturbed (vegetation cover <50 %) and undisturbed (vegetation cover >50 %). The results showed that traffic intensity and roadside habitat features affect the population dynamics of A. artemisiifolia. High traffic intensity and high disturbance resulted in the highest population growth whereas population growth in less suitable habitats (e.g. shaded roadsides) declined with decreasing traffic intensity. High levels of traffic facilitate A. artemisiifolia invasion along roads, due to continued seed dispersal. Management efforts should be prioritised along roads with high traffic intensity and disturbed habitats along roadsides should be kept to a minimum.
Sources
Lemke A, Buchholz S, Kowarik I, Starfinger U, von der Lippe M (2021) Interaction of traffic intensity and habitat features shape invasion dynamics of an invasive alien species (Ambrosia artemisiifolia) in a regional road network. NeoBiota 64, 155-175.