Superior performance of invasive grasses over native counterparts will remain problematic under warmer and drier conditions

Elevated temperatures and drought may exacerbate invasion success of non-native grasses, as non-native species often possess traits favored by a warmer, drier world. In our study, we assessed plant traits potentially linked to invasion success under elevated temperature and drought, including biomass production, reproductive allocation, arbuscular mycorrhizal (AM) fungal root colonization, and germination of native grasses and non-native invasive grasses. We selected two caespitose warm-season grasses [native ( Schizachyrium scoparium ) and non-native ( Bothriochloa ischaemum )] and two cool-season grasses [native ( Pascopyrum smithii ) and non-native ( Bromus inermis )]. Plant biomass, reproductive effort, and AM fungal colonization were assessed at two temperatures (ambient or elevated) and four levels of soil water-availability; germination was assessed at two temperatures and three levels of soil water-availability. Non-native warm- and cool-season grasses produced greater vegetative biomass, initiated seed production more frequently, and displayed greater germination when grown under elevated temperature and drought, compared to their paired native counterparts. Percent AM fungal root colonization of the non-native grasses was generally greater than native grasses regardless of soil moisture or elevated temperature. Our results suggest that under warmer and drier conditions non-native grasses will continue to outperform native species, due to greater biomass production, germination capabilities, and colonization by AM fungi.