Ambrosia artemisiifolia seed movement along roadsides
Transportation corridors can provide suitable habitats to facilitate the spread of invasive alien plants. In addition, vehicles can act as dispersal vectors for the spread of invasive alien plant propagules, as seeds can become attached to vehicles and vehicle movement can initiate increased airflow that aid seed movement. Both of these scenarios can act to move plant propagules over large distances. To evaluate the role of primary dispersal of invasive alien plants along a roadside corridor and the secondary dispersal by vehicle movement, two experiments were undertaken using Ambrosia artemisiifolia (Asteraceae: EPPO List of Invasive Alien Plants) as the study species. A. artemisiifolia is commonly found along roadsides within Europe. The study site was the federal state of Brandenburg (DE) which has harboured large populations of A. artemisiifolia since the mid-1800s. Primary dispersal was evaluated by planting three individual plants close to maturity within an arable field and surrounding vegetation was removed. Seeds were captured on adhesive material placed on the ground and the distance from the parent plant was measured. Secondary seed dispersal was measured with a mark and recapture experiment along three road corridors with different volumes of traffic. At each road corridor, 100 seeds tagged with UV markers were placed on the asphalt surface (30-40 cm from the edge to ensure proximity to passing traffic). After two days, searches for the seeds were conducted using LED-UV lamps up to 500 m in the driving direction and 50 m against the driving direction. The mean dispersal of seeds from the planted specimens was 0.39 metres, whereas secondary dispersal by vehicles was up to 53.2 metres on roads with the highest volume of traffic. It is interesting to note that almost all of the seeds recaptured were found on the road verges rather than the road surface. These results can be transferred to the management of the species along roads as they indicate that mowing before seed set can reduce the potential of spread.
Sources
Lemke A, Kowarik I, von der Lippe M (2018) How traffic facilitates population expansion of invasive species along roads: the case of common ragweed in Germany. Journal of Applied Ecology DOI: 10.1111/1365-2664.13287.