DUST PREVENTION IN THE AMERICAN SOUTHWEST BY ARTIFICIAL MICROBIAL SELECTION

Abstract

Desert dust is a danger to ecology and human health. Land overuse and climate change are contributing to increasing dust emissions and decreasing biodiversity. In the desert Southwest, biocrust comprised of cyanobacteria, their extra polymeric substances, and a diverse array of other microbes are an essential component of healthy soil aggregation. Crusted soil produces less dust and is associated with diverse arid ecosystems. In this thesis, we investigated microbial inoculants as a method for growing biocrust artificially. We tested cyanobacteria, Lactobacillus spp., and arbuscular mycorrhizal fungi inoculant in a rhizobox experiment and cyanobacteria plus plants in a field experiment. The field experiment utilized MICROP cyanobacteria inoculant in conjunction with native grass seeds to find the combination that would result in the most diverse and altered soil microbiome. Richness, Shannon diversity, cyanobacteria relative abundance, and bacterial community composition were analyzed by treatment and spatial position in the field site. In the rhizoboxes, the AM fungi and MICROP were associated with a higher cyanobacteria % than control. In the field, inoculation was not an effective mechanism for promoting cyanobacteria over other microbes and was not associated with an altered and more diverse microbiome. However, spatial position in the field plots had a significant positive correlation with richness, Shannon diversity, cyanobacteria RA, and composition. This could mean the experimental design of the field experiment was compromised by uncontrolled environmental factors, but plant abundance in different plots is a possible explanatory variable. These experiments provide valuable insight to land managers searching for microbial dust controls, but more research is needed into the microbial interactions that produce biocrust.