Soil microbiomes offer major opportunities to increase soil carbon, improve soil health, and ensure the sustainability of dryland systems. However, in drylands of the southwestern USA, there are few avenues to incorporate knowledge of the soil microbiome and plant-microbe interactions into management plans. Meanwhile, in these arid and semi-arid ecosystems, the additive effects of land- use intensification (grazing), climate changes (e.g., increasing drought events), and increased soil erosion create a threatening self-reinforcing cycle that will inhibit these soils to effectively produce food, sequester carbon, and support other ecosystems services in the future. Mechanistic studies are needed that will 1) assess how soil microbial diversity, composition, and functions vary across heterogeneous rangelands in the southwestern USA, 2) quantify the impacts of combined land-use and climate change, and 3) provide realistic management solutions for future restoration and conservation efforts. Here we propose a study that will test for the interacting effects of climate change and land-use on soil microbial functions, plant productivity, and carbon storage across the Sonoran and Chihuahuan Deserts. Using novel microbiome analyses, combined with an arid- focused soil health assessment framework, and innovative greenhouse experiments we will quantify the genomic and functional variability of the soil microbiome across dryland ecosystems and advance the basic understanding of microbial controls on carbon pools in drylands under global change pressures. We will then identify scenarios in which plant-microbe interactions and consortia of soil microbes can be leveraged in land management to resist increasing drought regimes and increase soil carbon under different land-uses. \t