The impact of Phytolacca americana on ground-dwelling forest arthropods
Phytolacca americana is native to North America and widespread within the EPPO region. Within the EPPO region, the species occurs in clear-cut areas, along hedgerows and wasteland (e.g. in Switzerland) along field margins, canals and coastal areas. The species is found in forest plantations in Hungary and in disturbed woodlands. In France, the species can be found in riparian habitats, clearings and forest edges, near dwellings, in wastelands, railway stations, old quarries, rubble, and corn crops. A study was conducted in three forest locations in the southern part of the Rhineland-Palatinate (upper Rhine Valley), Germany. At each location, six paired plots were selected where each pair consisted of one site invaded by P. americana and one site which is free from the plant (as a control). In each site, three pitfall traps were installed in the ground between July and September 2016. The traps were emptied every two weeks and the ground dwelling arthropods were sorted into taxonomic groups. Additionally, the percentage cover of native plants and P. americana was estimated at each site. In total, over 56 000 ground dwelling arthropods were identified during the course of the study. When comparing arthropod numbers with the percentage cover of vegetation, it was clear that P. americana significantly influenced the arthropod community. Carabid density was significantly lower in invaded sites compared to native sites. Acari showed a higher abundance in invaded sites compared to uninvaded and in contrast, the abundance of the cricket Nemobius sylvestris was negatively affected by P. americana. Future studies could be conducted to evaluate the potential impact on ecosystem functioning, for example litter decomposition of P. americana especially as the leaves contain toxins.
Schirmel J (2020) Differential effects of American pokeweed (Phytolacca americana) invasion on ground-dwelling forest arthropods in southwest Germany. Biological Invasions 22, 1289-1298.