Impacts of drought and native grass competition on buffelgrass (Pennisetum ciliare)

Invasive species are detrimental to ecosystems worldwide, and long-term invasive treatment outcomes are generally poor. Integrating active restoration into an invasive species treatment plan by seeding with species that that can competitively suppress the invader may help to improve treatment outcomes. Buffelgrass is a drought tolerant perennial grass that is highly invasive and disruptive to dryland ecosystem biodiversity across the globe. In this greenhouse experiment, we examine how buffelgrass growth and traits were impacted by the combination of competition with eight native grasses species and water availability. We found that when buffelgrass was grown with species that establish rapidly and have large biomass, buffelgrass tends to exhibit rapid growth, despite becoming more drought stressed. Conversely, when buffelgrass was grown with species that are slow growing and conserve their size under drought conditions, buffelgrass biomass is arrested. The ability to adjust its strategy depending on its neighbor’s strategy and on the amount of precipitation makes buffelgrass a robust invader. However, our results showed that growing buffelgrass with drought tolerant perennial grass neighbors reduced buffelgrass shoot biomass by up to 95% when grown in drought conditions. This indicates that seeding with native grasses after buffelgrass treatment is a beneficial option for suppressing re-invasion from the seedbank.