Effects of Salt Stress on Interspecific Competition Between an Invasive Alien Plant and Three Native Species

Biological invasions and soil salinization have become increasingly severe environmental problems under global change due to sea-level rise and poor soil management. Invasive species can often outcompete native species, but few studies focus on whether invasive alien species are always superior competitors under increasing stressors. We grew an invasive grass species, L., and three native grass species ( Lévl. et Vant., L., and Thunb.) as a monoculture (two seedlings of each species) or mixture (one seedling of and one native species seedling) under three levels of salt treatments (0, 1, and 2 g/kg NaCl) in a greenhouse. We found that invasive exhibited greater performance over native and , but lower performance compared to , regardless of the soil salinity. However, salinity did not significantly affect the relative dominance of . Interspecific competition enhanced the growth of and inhibited the growth of . Although seedlings always had growth dominance over seedlings, was not affected by at any salt level. At high salt levels, inhibited the growth of , while did not affect the growth of . Salt alleviated the competitive effect of on but did not mitigate the competition between and the other two native species. Therefore, our study provides evidence for a better understanding of the invasive mechanisms of alien species under various salinity conditions.