Dissertation research: Does long-term drought alter the response of microbial communities to moisture?

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Molecular advances in recent decades have revealed the immense diversity of microorganisms that inhabit the soil. These microorganisms depend on moisture to regulate the water balance in their cells and access food. Drought is expected to increase in areas of the US West, likely causing more frequent water stress for these organisms. Other organisms, like plants, differ in their sensitivity to drought, and this causes the composition of the community to shift under drought, sometimes to one that responds differently to water. Despite the important role of microorganisms in the cycling of nutrients, and predictions of harsher climates, we know little about how these communities might change under drought or other disturbances. This project will study how these soil microbial communities will change under drought, and whether these new drought-tolerant communities respond differently to moisture than non-drought communities. To answer this question, soils will be collected from a long-term drought manipulation in a Colorado grassland and subject both non-drought and drought soils to a range of moisture levels in the lab. To describe how the community changed, two exciting new technologies will be used. First, microorganisms that are active in the soil will be isolated. Since microorganisms are able to survive in a dormant state for long periods of time, much like seeds, it is important to separate the actively growing microorganisms - those that are affecting the function of the ecosystem - from those that are dormant. Second, high-throughput sequencing and sample taxonomy at a fine resolution will be used to report whole-community changes as well as which species in particular might be more or less sensitive to drought.This research will elucidate how soil microbial communities might shift under drier climates, how this might influence nutrient cycles these communities control, and also how microbial communities, compared to plants and animals, respond to and recover from disturbance. The findings will both refine general ecological principles of how communities respond to disturbance, and improve our ability to predict changes and feedbacks that might occur under different climate regimes.