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Introduction Propagule pressure (i.e., the number of propagules) has long been recognized to play an essential role in plant invasion. But it is not clear whether propagule pressure influences the invasion of exotic plants into native plant communities when different frequencies of nitrogen are added. Method We established an experiment with three plant communities that included native plant communities alone (four grasses, two legumes and two forbs) or native plant communities with one or five invasive plants, Solidago canadensis , under three frequencies of nitrogen addition (no addition or low or high addition with the same amount). Results High propagule pressure significantly enhanced the biomass and relative dominance index of S. canadensis . Moreover, high propagule pressure only decreased the total and aboveground biomass of the legumes. However, the competitive effect between S. canadensis and the native community and biomass of the whole native community varied according to different frequencies. Conclusion Overall, high propagule pressure encouraged invasion by S. canadensis , while alow nitrogen frequency was advantageous for the native community to resist invasion in this experiment. The results provide a scientific basis to manage and control the invasion of S. canadensis .

Aims Native plant communities are commonly invaded by invasive plants to different degrees. However, the relative contribution of the invasive plant abundance vs. phylogenetic evenness to the responses of wetland communities to different degrees of invasion is still unclear. In addition, whether such contribution varies with environmental conditions such as flooding is also unclear. Methods To address these questions, we chose Alternanthera philoxeroides as the invasive plant, and set up four invasive degrees by changing the community species composition under both flooding and non-flooding conditions. The relative abundance of A. philoxeroides and phylogenetic evenness changed simultaneously with the change in the community invasion degree. Important Findings The invasion degree significantly affected the individual biomass of A. philoxeroides and some native species. Variation partitioning showed that the relative abundance of A. philoxeroides contributed more to variation in community indicators than phylogenetic evenness, regardless of flooding. Spearman rank correlation test showed that the relative abundance of A. philoxeroides was negatively correlated with the individual biomass of A. philoxeroides and some native species, while the phylogenetic evenness was positively correlated with only a few native species. And their correlation strength and significance were all affected by specific species and flooded environment. In conclusion, our results suggest that the relative abundance of A. philoxeroides can more effectively explain the wetland community response to different invasion degrees than phylogenetic evenness, regardless of flooding.