Dissertation Research: Linking microbial ecophysiology to soil organic matter abundance and stabilization

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Terrestrial ecosystems depend on soil organic matter (SOM) for sustaining agricultural productivity and other vital ecosystem services, yet global SOM stocks are threatened by environmental change. Currently, the ability to mitigate SOM losses is limited by our understanding of the processes regulating SOM formation and long-term persistence. In recent years, new concepts of SOM formation and persistence have emerged suggesting that SOM is largely derived from soil microbes. Contrasting sharply with older concepts that emphasize the importance of complex plant-derived compounds in SOM formation, the new emphasis on microbial processes might dramatically improve SOM management if only the mechanisms were better understood. Specifically, there is relatively little known about the microbial physiological traits that regulate microbial production and the fate of microbial products in different soil types. To address this knowledge gap, the broad objective of this research is to link microbial physiological traits to SOM formation and persistence. This objective will be met using a long-term laboratory study to track newly formed SOM derived from microbial processes in different soil types. The soils vary in their clay mineralogy and carbon inputs from plants and, as a result, will select for different microbial communities and physiological traits, which together will presumably lead to differences in the long-term stability of the newly formed SOM. Throughout the experiment, measurements will be made of microbial physiological traits that can be linked to biomass synthesis, rates of SOM formation, SOM chemistry, microbial biodiversity, and SOM persistence.Results from this work will lead to improvements in current models of SOM formation and stabilization and will characterize the important relationships among microbial physiology, carbon input quality, and the soil environment. This study will make fundamental contributions to microbial ecology and soil and ecosystem science and could change how we mitigate the adverse effects of land-use conversion and climate change on SOM losses. Specifically, this research could encourage new approaches for land-use conservation, restoration, and agricultural management that emphasize the indirect building of SOM by managing microbial biomass production.