Lehmann lovegrass (Eragrostis lehmanniana) is an invasive exotic perennial grass throughout the Sonoran Desert. However, in the neighboring Chihuahuan Desert, this species is generally present in low abundance, although data on its geographic distribution are scarce. Our objectives were to identify the climatic and edaphic factors important to seedling establishment of Lehmann Lovegrass in order to predict its spatial distribution in the Chihuahuan Desert under current and alternative climate scenarios.
We used the SOILWAT model to simulate seedling establishment of Lehmann lovegrass at 57 weather stations with daily precipitation and temperature data during 1981-2010; stations were distributed throughout the Chihuahuan Desert in the southwestern US. Combinations of 10 climate scenarios and 12 soil texture classes were simulated. The simulation results were used to develop logistic regressions to identify important factors related to seedling establishment. These regression equations at the weather stations were extrapolated using PRISM climate grids and SSURGO soil data to generate maps of simulated distribution of Lehmann lovegrass in the Chihuahuan Desert under current and alternative climate scenarios.
Simulation results for current climate were consistent with the observed patterns: in general, simulated probability of seedling establishment was low for most of southern New Mexico and western Texas, but there were localized areas with high probabilities (> 0.8) along the transition with the Sonoran Desert in southeast Arizona and north of Big Bend, Texas. Increases in precipitation and temperature caused increases in simulated probability of seedling establishment, and the effects of increasing temperature and precipitation on seedling establishment increased as silt content of the soil increased throughout the region. For fine-textured soils with high resistance to seedling root penetration, there was no change in probability of seedling establishment with increase in temperature or precipitation. In conclusion, fine-textured soils will be least responsive to Lehmann lovegrass invasion with climate change, and there are complex interactions between soil texture, temperature, and precipitation for the other soil types and locations.