Simulated distribution of an invasive grass, Lehmann lovegrass, in the Chihuahuan Desert under future climate scenarios
Lehmann lovegrass (Eragrostis lehmanniana), a perennial grass introduced to the Southwest US in the 1930s from South Africa, has had a limited distribution in the Chihuahuan Desert while it has dominated many grassland sites in the Sonoran Desert. Previous observational studies and our site-based model simulations suggest that climate (precipitation and temperature) is the main driver for the difference in the current species’ distributions in the two Southwest deserts. Our goal was to predict the distribution of Lehmann lovegrass throughout the Chihuahuan Desert under current climate conditions and future climate scenarios. We used the SOILWAT simulation model to simulate Lehman lovegrass seedling establishment, with SSURGO data as input for soil related variables. The 1971-2000 mean precipitation and temperature from PRISM were used for the current climate conditions, and these data were adjusted based on the projected changes in National Climate Assessment for Southwest US to simulate future climate scenarios.
Under current climatic conditions, the simulated distribution of Lehmann lovegrass in the Chihuahuan Desert is mainly in the southern portion of the desert, similar to observed populations. Under future climate scenarios, the spatial distribution of the species varies due to the combined effects of precipitation and temperature. The species distribution decreases when precipitation decreases or temperature increases a large amount. The species distribution expands when precipitation increases and temperature increases in low to moderate amounts. Our study shows that the distribution of Lehmann lovegrass in the Chihuahuan Desert will depend on the amount and direction of changes in future temperature and precipitation. This uncertainty in the projected distribution adds one more challenge to land management of this invasive grass under climate change.