Data.xlsx

As multiple invaders co-occur in similar habitats, understanding the interactions between different invasive species is very important. Invasional meltdown and neutral and interference relationships have been reported. However, interspecific interactions may vary with environmental change due to the different responses of various invaders. To better understand the interaction of notorious invasive alien plants under global climate change, the growth characters of common ragweed (Ambrosia artemisiifolia) and redroot pigweed (Amaranthus retroflexus) were compared when they were planted in monoculture or mixed culture under four environmental treatments: elevated CO₂, enriched N, elevated CO₂ + enriched N and a control. The results showed that 1) the plant height, basal stem diameter, and shoot, root, and total biomass of common ragweed all consistently increased in response to the treatments, while the growth traits of redroot pigweed were all inhibited. A significant CO₂×N interaction was found only for the shoot and total biomass of common ragweed. 2) Invasional interference between these two notorious alien invasive plants was discovered. Common ragweed consistently displayed an obvious competitive advantage over redroot pigweed regardless of treatment. 3) Elevated CO₂ and enriched N obviously changed the seed mass frequency distribution of common ragweed: elevated CO₂ increased the proportion of small seeds, while enriched N increased the proportion of large seeds. We conclude that common ragweed can outcompete redroot pigweed; moreover, elevated CO₂ and N addition hasten this competitive advantage.