Rea Maria Hall, Gerhard Karrer, Lisa Zant and Miriam Aliabadi
Department of Integrative Biology and Biodiversity Research; University of Natural Resources and Life Science Vienna, Austria
Common ragweed (Ambrosia artemisiifolia L.) is an invasive annual plant with highly allergenic pollen. Its spread often occurs on roadsides, where it builds stable and rapidly growing populations. The most sustainable way of controlling the population size of this species is to prevent seed production in order to deplete the soil seed bank. Populations on roadsides are submitted to regular mowing management, this can even exacerbate the situation by inducing re-sprouting after cutting or by accidentally spreading seeds along the road. From former experiments in Austria, we know that an important factor influencing the growth potential of common ragweed along roadsides is the presence and the composition of (native) competitors which can be very effective in prohibiting the successful emergence of ragweed seedlings.
Therefore, in a 3-year field trial five different cutting regimes differing in timing and frequency of cuts were tested on eight roadside verges in Bavaria, characterized by different climatic conditions and traffic densities. On the basis of soil seedbank samplings along these roadside verges as well as on the road embankments (July and October 2018), the study should reveal which cutting regime is most effective in the prevention of flower and seed formation of common ragweed.
In addition, a 3-year field trial on the competitive suppression of common ragweed by four different seed mixtures combined with three different cutting regimes was implemented at three different sites. First, results showed that the primary habitat of common ragweed is the roadside verge: 97.9% of all plants counted as well as 96.7% of all seeds found in the soil seed bank were concentrated on the first 1.5 m next to the lane, irrespective of the soil properties and the inclination of the embankment. Furthermore, it could be revealed that contamination of the soil seedbank with ragweed seeds as well as the viability of the seeds differed significantly between the sites. The first cutting treatments will start in May 2019 and the results of this study should contribute to a local adapted management system of common ragweed which can sustainably inhibit the further production and spread of seeds not only along road verges but also into surrounding areas.