Copper Uptake and Its Effects on Two Riparian Plant Species, the Native Urtica dioica, and the Invasive Fallopia japonica .

Copper accumulating in stream sediments can be transported to adjacent riparian habitats by flooding. Although being an essential element for plants, copper is toxic at high concentrations and restricts, among other things, plant growth. Besides copper, invasive plants, such as , which are known to be tolerant toward heavy metals, modify riparian habitats. If the tolerance of is higher compared to native plants, this could accelerate invasion under high heavy metal stress. Therefore, we aimed to compare the effect of copper on two common riparian plants, the invasive and the native . We performed a pot experiment with a gradient from 0 to 2430 mg kg of soil copper. We hypothesized that (i) negative effects on plant growth increase with increasing soil copper concentrations with being less affected and (ii) accumulating higher amounts of copper in plant tissues compared to . In support of our first hypothesis, growth (height, leaf number) and biomass (above- and belowground) of were impacted at the 810 mg kg treatment, while the growth of was already impacted at 270 mg kg. Due to 100% mortality of plants, the 2430 mg kg treatment was omitted from the analysis. In contrast, chlorophyll content slightly increased with increasing copper treatment for both species. While accumulated more copper in total, the copper uptake by increased more strongly after exposure compared to the control. In the 810 mg kg treatment, copper concentrations in were up to 2238% higher than in the control but only up to 634% higher in . Our results indicate that might be able to more efficiently detoxify internal copper concentrations controlling heavy metal effects compared to the native species. This could give a competitive advantage particularly in polluted areas, facilitating its invasion success.