Nitrogen deposition modulates invasibility and stability of plant communities in microplastic-contaminated wetlands

Invasive plant species pose a significant threat to the integrity and biodiversity of local ecosystems. Microplastic pollution and nitrogen deposition, as detrimental consequences of human activities, impact the growth of wetland plants. However, the combined impacts of nitrogen deposition and microplastics on invaded plant communities remain unexplored. Here, we conducted a greenhouse experiment to examine the effects of simulated nitrogen deposition on the performance of invaded plant communities under polyethylene addition (PE, polyethylene addition alone, at ratios of 0.1 %, 0.5 %, 1 %; PEN, polyethylene addition combined nitrogen deposition, 30 kg N hm−2 a−1). Our findings suggested that both PE and PEN treatments reduced the morphological traits of invaded plant communities, including plant community abundance, height and biomass. Notably, the height and stem diameter of Amaranthus palmeri increased with higher PE ratios, indicating that invasive species has greater pollution tolerance than native plant Chenopodium album. Additionally, our results showed that the diversity and stability values of the PEN treatments were higher than those of the PE treatments, suggesting that the detrimental effects of microplastics on the community diversity and stability can be mitigated to some extent by the combined nitrogen deposition. We also demonstrated changes in the soil may have altered interspecific relationships among dominant plant species, with A. palmeri potentially modifying these relationships to enhance its survival. Overall, most PE and PEN treatments resulted in a decrease of 1.05∼41.44 % in community invasibility and 2.02∼88.73 % in invasion intensity of invasive species, which could be linked to changes in community diversity. This research enhances our understanding of the influence of microplastics alone or combined nitrogen deposition on the invaded plant communities, providing valuable insights for the environmental management of these ecosystems.