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.
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).
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.