Arid and semi-arid lands cover a large fraction of Earth’s surface and support the livelihoods of hundreds of millions of people. Many of these landscapes are changing. A critical, but often overlooked, component of healthy drylands is biological soil crusts (“biocrusts”), thin, living soils formed by communities of microorganisms. Biocrusts stabilize soil, support nutrient cycling, and regulate dust emissions, thereby protecting soil fertility and human health. Biocrusts are sensitive to environmental stress, particularly exposure to strong daily and seasonal temperature variations that characterize dryland environments. Recent research suggests that abrupt or extreme events may be more disruptive to biological systems than average conditions alone. This project seeks to improve understanding of how biocrust microorganisms respond to temperature volatility, knowledge that is essential for predicting biocrust persistence and guiding efforts to maintain and restore dryland soil function. By advancing soil microbiology research, supporting education and training, and informing land management practices, this project advances science and contributes to national priorities in biotechnology, agriculture and workforce development. The project integrates laboratory experiments, global data analysis, and education-focused research to examine how biocrust microorganisms respond to temperature fluctuations. First, controlled mesocosm experiments will be used to define the thermal tolerance range of biocrust microbial communities and to identify thresholds at which community composition and metabolic function shift. Microbial activity and community structure will be characterized using genomic sequencing and functional assays. Results from these experiments will guide analyses of a global biocrust survey dataset spanning diverse dryland regions to evaluate whether similar microbial responses are observed across natural thermal gradients. Second, the project will focus on k