Warming affects the invasion ability and competitiveness of the invasive plant Alternanthera philoxeroides

Invasive plants may positively adapt to temperature increases caused by global warming, and these changes could promote their harmful effects. Therefore, it is important to control invasive plants in order to decrease the harm they cause. In this study, we focused on the invasive plant Alternanthera philoxeroides and chose Lolium perenne and Trifolium repens as its competition plants. There were three treatments. These were one plant of each species per pot (no competition), two plants of the same species in one pot (intraspecific competition), and two plants from different species in one pot (interspecific competition). Half the pots were placed under warming conditions. The results showed that (1) under warmer conditions, A. philoxeroides allocated more biomass to the growth of aboveground parts through improvements to light energy capture by its leaves and stems. Warming also increased the competition between A. philoxeroides and L. perenne or T. repens. Both responses indicated that warming will enhance invasion by A. philoxeroide. (2) Interspecific competition inhibited the growth of A. philoxeroides, but the inhibition did not significantly change (P > 0.05) as the competition density increased. The results showed that L. perenne and T. repens significantly inhibited A. philoxeroides growth, and an analysis of the A. philoxeroide relative yield under the different competition conditions showed that L. perenne inhibition of A. philoxeroide was more significant (P < 0.05) than inhibition due to T. repens. (3) Warming generally promoted L. perenne growth. However, growth was inhibited by interspecific competition under warming conditions, but there was no significant (P > 0.05) inhibition under non-warming conditions. In contrast, warming had no significant effect (P > 0.05) on T. repens growth, but its growth was considerably inhibited by interspecific competition. Furthermore, interspecific competition decreased A. philoxeroide aboveground biomass by 89.5%, L. perenne by 55.8%, and T. repens by 82.5%. The results suggest that L. perenne could be used as a competitive plant to control A. philoxeroide.