Research Starter Grant: Spatial Interactions between Microbes and Organic Matter across Different Scales

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Microorganisms are important drivers of biological and chemical processes that control the retention and loss of carbon and plant nutrients from terrestrial ecosystems. It is important to understand the factors controlling microbial distribution and activity in soil. The physical location, or spatial organization, of microbes in soil is critical in determining rates of plant detritus decay, nutrient release, and carbon sequestration. The proposed research will study how differences in plant type (pasture grasses versus forest trees) and soil disturbance (grazing) affect interactions between microbes, plant-derived organic matter, and mineral constituents of soils at multiple spatial scales, and how these affect carbon and nutrient cycling in soil. This study will apply new advances in spectroscopy and microscopy, in particular, secondary ion mass spectrometry (SIMS) and NanoSIMS, to visualize and chemically characterize individual biological and physical components in soils at the micro- and nanometer scales. Differences in microbial community composition and activity between sites, and within the soil architecture, will be measured using new methods coupled with NanoSIMS, as well as more conventional enzymatic and lipid analysis methods.Microorganisms are crucial agents in ecological processes, but are one of the least studied components of ecosystems. The study of their distribution and interactions in soils has been limited by methodological constraints. Technological advances now allow us to better describe their habitats and function. An exciting and challenging aspect of this study is the integration of data across different spatial scales, from that of soil aggregates (centimeters to millimeters) to that of bacterial cells and their component (micrometers and nanometers). These new methods have been successfully applied in the medical and geochemical fields, but there are only a handful of studies currently exploring their application in soil biology and biogeochemistry. The broader impacts of this research are many-fold. Accurate predictions of how terrestrial ecosystems will respond to future climate and land-use changes, and in particular, whether they absorb or release carbon to the atmosphere, require an understanding of the biological and physical interactions between microbes, plants, and soil. Soils are one of the largest and most dynamic terrestrial reservoirs of carbon, much greater than the atmosphere and land vegetation. Thus, they exert an important influence on atmospheric concentrations of carbon dioxide and other greenhouse gases. Another important application of this research is the management of microbiological processes that contribute to soil fertility for the sustainable production of food and bioenergy.