NSFDEB-BSF: Sources, controls, and significance of soil geosmin emissions in dryland ecosystems

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Those who have spent time in deserts are likely familiar with the 'smell of rain' - the earthy scent characteristic of soils moistened by recent precipitation. One of the key compounds contributing to this scent is geosmin, a compound exclusively produced by soil microbes. Geosmin was discovered over fifty years ago. What is its biological function? This is as yet unknown, as are which soil microbes produce geosmin and how its release from soil varies across time and space. These knowledge gaps are unsettling given that geosmin is likely to have critical roles in desert systems, influencing the growth and activity of soil microbes and plants. This project will study soils collected from deserts in Israel and the U.S. to determine how and why rates of geosmin release from soil vary, identify the microbial sources of geosmin, and determine how geosmin can influence the growth of plants and microbes. This work will provide insight into a widely-observed phenomenon that is key to understanding how rain storms influence desert systems and how to best monitor and manage the health of desert landscapes under changing environmental conditions. The study of geosmin also provides a unique opportunity to introduce students to the field of soil ecology. This project will leverage research activities to enhance educational opportunities for groups typically under-represented in scientific disciplines (high school-aged Bedouin students in Israel and Native American undergraduates in the U.S.) with activities focused on desert soil ecology. In addition, as a collaboration between U.S. and Israeli researchers, this project presents a unique opportunity to foster international research and educational training efforts.Although volatile organic compounds (VOCs) are increasingly recognized as being important in belowground systems, the specific nature of these emissions and the associated consequences for soil biota remain poorly understood. This project focuses on one such VOC, geosmin - a microbially-produced metabolite often emitted in high concentrations from desert soils following rain events. This project will examine geosmin emissions across aridity gradients in southern Israel and the southwestern U.S., pairing gas chromatography/mass spectrometry analyses with DNA and RNA-based approaches to identify the specific taxa responsible for the production of this VOC and the controls on its emission rates. This project will also use a series of experimental assays to test the hypothesis that geosmin acts as a signaling molecule with wide-ranging effects on the germination, growth, and activities of microbes and plants in desert ecosystems. Together, this work will advance our understanding of a poorly understood, phenomenon in desert systems that is likely to have important consequences for understanding biotic responses to rewetting events in arid environments. As such, this work will be relevant to researchers in disciplines ranging from ecosystem ecology to microbiology to soil science, and is very relevant to understanding the impacts of climate change. Training opportunities that broaden participation in science will be incorporated into different aspects of the project, and information will be disseminated to K-12 students and the public via science-based graphic novels.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.