Abstract
Microplastics in soils can affect plant performance, as shown in studies using individual plants. However, we currently have no information about potential effects on plant community productivity and structure. In a plant community consisting of seven plant species that co-occur in temperate grassland ecosystems, we thus investigated the effect of microplastics (i.e., microfibers) and drought, a factor with which microfibers might interact, on plant productivity and community structure. Our results showed that at the community level, shoot and root mass decreased with drought but increased with microfibers, an effect likely linked to reduced soil bulk density, improved aeration, and better penetration of roots in the soil. Additionally, we observed that microfibers affected plant community structure. Species such as Calamagrostis, invasive in Europe, and the allelophatic Hieracium, became more dominant with microfibers, while species that potentially have the ability to facilitate the establishment of other plant species (e.g., Holcus), decreased in biomass. As microfibers affect plant species dominance, the examination of cascade effects on ecosystem functions should be a high priority for future research.