Collaborative Research: Network Cluster: Geomicrobiology and Biogeochemistry in the Critical Zone

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The critical zone is the active upper crust of the Earth, from the lowest groundwater to the top of the highest tree. Critical Zone science is at an important juncture: it is incorporating life in more quantitative ways. This project will evaluate the contribution of the microorganisms that drive so many of the dynamics of the Critical Zone, addressing crucial gaps in our knowledge of surface and deep soil microbes and their functions. The major goal of this research is to develop a predictive understanding of the role of microbes as drivers of Critical Zone biogeochemistry and soil formation. The researchers’ preliminary investigations across the former Critical Zone Observatory Network identified variable patterns in microbial biodiversity with increasing soil depth across sites, with some sites showing little to no change with depth, and others a complete turnover of the microbial community members. The current project will illuminate the mechanisms underlying these trends. This project will train numerous undergraduate students, most of whom will be underrepresented minorities at several Hispanic Serving Institutions (HSIs) and high schools in underserved communities across California. Results will be disseminated to the greater public through a series of webinars that will provide real life examples of how to address Critical Zone science questions by leveraging diverse scientific backgrounds, as well as through incorporation into the “Welcome to the Critical Zone” public museum exhibit at The University of Arizona’s Flandrau Science Center.This project will address the hypothesis that soil type, hydrology, and lithology are key determinants of the depth to which surface influences such as vegetation and climate drive microbial community composition, diversity, and activity. Specifically, where soils are deep or are derived from nutrient- rich bedrock, the researchers hypothesize that rooting depths will be greater, resulting in a greater similarity between surface and deep soil microbial communities compared to those from shallower soils or those developed from less nutrient-rich substrates. In this proposed project, the researchers will use a novel combination of DNA and RNA sequencing, real-time soil gas and environmental monitoring, quantified enzyme activities, detailed soil organic matter and isotopic analyses, as well as root abundances to address the hypothesis. To amplify the impact of this approach, the project will develop a unique and detailed geomicrobiology characterization of key indicator species of bacteria, archaea and fungi, grouped to distinguish those that are surface-based and those representative of bedrock interactions. This novel framework will be tested across years and will generate a resource for the larger NSF Geoscience community for years to come. This project will also form an important interdisciplinary aspect of the new Critical Zone Collaborative Network, through collaborations with various other Clusters and the Hub. This award is co-funded by the Critical Zone Collaborative Network of the Division of Earth Sciences and the Ecosystem Sciences cluster of the Division of Environmental Biology.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.