Background:The invasive plant species Fallopia japonica is suspected to use polyphenols as a novel weapon to inhibit nitrification in soil. Both specific polyphenols and their entry pathways are yet to be determined. As plants may increase the production of polyphenols under copper (Cu) stress, an additive effect can be expected in contaminated (riparian) areas.Aims: This study aimed to identify the entry pathways of total and specific polyphenols in F. japonica and to test whether polyphenols inhibit nitrification with Cu contamination. Methods: Combining F. japonica and a Cu gradient in a 2-year mesocosm experiment, total polyphenol, emodin, and resveratrol concentrations were analyzed in the plant (roots, root exudates, vital and senescent leaves) and soil (rhizosphere, non-rooted soil) representing different entry pathways. We measured the potential nitrification rate (PNR) under stress caused by F. japonica and Cu as well as the response of PNR under resveratrol and emodin addition.Results: Emodin and resveratrol were detected in all plant tissues. Emodin concentrations significantly increased in senescent leaves under Cu stress, while no Cu effect was observed for resveratrol or total polyphenols. Resveratrol decreased the PNR. The stressors had neither a synergistic nor additive effect. Nitrification inhibition was lower in the rhizosphere compared to the non-rooted soil, suggesting that F. japonica reduced nitrate availability for co-occurring plants.Conclusions: Joint occurrence of F. japonica and Cu did not amplify the PNR inhibition over the individual effect. Our study emphasizes the effectiveness of F. japonica in inhibiting the PNR in invaded riparian ecosystems with potentially negative effects on biodiversity.

science projects, but also data providers, relatively early on. However, at the core and perhaps the most important factor contributing to the successful continuity of this project, is the dedication and engagement of the CLIC community scientists. We are incredibly fortunate that our community scientists are passionate and supportive of this work.To date, this project has collected over 52,500 lake ice phenology observations for 1008 lakes, and involved 935 monitors over the years (Fig. 3). As we work toward organizing these vast datasets, we look forward to exploring important questions on how climate change is affecting lake ice phenology across small and large lakes in the United States and identifying which lakes are most vulnerable to rapid ice loss. AUTHOR CONTRIBUTIONSS conceived the idea and led the project. SS and LSL wrote the first draft. KB created figure 3. LSL, AB, KB, KS, DB, GB, and SS helped conceptualize the survey questions for the community scientists, contextualize the historical aspects of the project, and edited the manuscript. ACKNOWLEDGMENTSFirst and foremost, the authors are indebted to the participants and citizen scientists from the Community Lake Ice Collaboration for their dedication and enthusiastic efforts to collect lake ice phenology data from their local lakes over the past 30 years.

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 Fallopia japonica, which are known to be tolerant toward heavy metals, modify riparian habitats. If the tolerance of F. japonica 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 F. japonica and the native Urtica dioica. We performed a pot experiment with a gradient from 0 to 2430 mg kg−1 of soil copper. We hypothesized that (i) negative effects on plant growth increase with increasing soil copper concentrations with F. japonica being less affected and (ii) accumulating higher amounts of copper in plant tissues compared to U. dioica. In support of our first hypothesis, growth (height, leaf number) and biomass (above- and belowground) of F. japonica were impacted at the 810 mg kg−1 treatment, while the growth of U. dioica was already impacted at 270 mg kg−1. Due to 100% mortality of plants, the 2430 mg kg−1 treatment was omitted from the analysis. In contrast, chlorophyll content slightly increased with increasing copper treatment for both species. While U. dioica accumulated more copper in total, the copper uptake by F. japonica increased more strongly after exposure compared to the control. In the 810 mg kg−1 treatment, copper concentrations in F. japonica were up to 2238% higher than in the control but only up to 634% higher in U. dioica. Our results indicate that F. japonica might be able to more efficiently detoxify internal copper concentrations controlling heavy metal effects compared to the native species. This could give F. japonica a competitive advantage particularly in polluted areas, facilitating its invasion success.

Fallopia japonica and Impatiens glandulifera are major plant invaders on a global scale that often become dominant in riparian areas. However, little is known about how these species affect interactions in soil–plant systems. The aim of this study was to investigate the impact of both species on abiotic and biotic soil properties, with a special focus on fungi. We investigated eight sites along small streams invaded by F. japonica and I. glandulifera, respectively, and compared each with nearby sites dominated by the native species Urtica dioica. Three different types of samples were collected: bulk soil, rhizosphere soil and roots from invasive and native stands at each site. Bulk soil samples were analysed for soil physicochemical, microbial properties (soil microbial respiration and ergosterol) and soil arthropod abundance (Acari and Collembola). Soil respiration was also evaluated in rhizosphere samples. The fungal community composition of both bulk soil and roots were analysed using a metabarcoding approach. Soil physicochemical properties as well as soil microbial activity, fungal biomass and soil fungal operational unit taxonomic unit (OTU) richness did not differ between invaded and native riparian habitats, indicating only minor belowground impacts of the two invasive plant species. Soil microbial activity, fungal biomass and soil fungal OTU richness were rather related to the soil physicochemical properties. In contrast, Acari abundance decreased by 68% in the presence of F. japonica, while Collembola abundance increased by 11% in I. glandulifera sites. Moreover, root-associated fungal communities differed between the invasive and native plants. In F. japonica roots, fungal OTU richness of all investigated ecological groups (mycorrhiza, endophytes, parasites, saprobes) were lower compared to U. dioica. However, in I. glandulifera roots only the OTU richness of mycorrhiza and saprobic fungi was lower. Overall, our findings show that F. japonica and I. glandulifera can influence the abundance of soil arthropods and are characterized by lower OTU richness of root-associated fungi.