Plant-Plant and Plant-Soil Interactions Under Drought and the Presence of Invasive Buffelgrass

Drylands are predicted to become more arid with future climate change scenarios and have the potential for expansion. Invasive grasses with drought-tolerating strategies proliferate in these areas although limited resources characterize these ecosystems. Buffelgrass is a particularly invasive grass species with a high dominance in the southwestern United States. Plant-plant and plant-soil interactions could play a major role in mechanisms of invasion and could prove to be an essential link in understanding potential ecosystem alteration. However, we currently have a poor understanding of how soil microbial communities potentially enhance or obstruct invasive dominance. We used a greenhouse experiment in Tucson, Arizona to assess changes in native plant traits and soil bacterial and fungal communities in response to drought, buffelgrass presence, and their interaction. We found that buffelgrass increases its growth from growing in the presence of a native and that this effect may be mediated by increases in bacterial richness and a higher abundance of nitrogen-fixing soil microorganisms. A simulated drought had no obvious effects on plants or soil microbial communities in this experiment. Overall, plant-plant and plant-soil interactions should be integrated into the science of invasion and restoration ecology, with significant potential for mediating the effects of interacting abiotic and biotic anthropogenic stressors.