CAREER:Mineralogical and Biogeochemical Control of Phosphorus Transformation during Soil Development

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Phosphorus (P) cycling and bioavailability in soils shapes ecosystem structure and function. At a given soil developmental stage during soil formation, the P chemical composition provides a useful context for evaluating contemporary cycling of P, carbon and other nutrients, and for determining how changes in P availability might affect diverse ecosystem processes, such as primary productivity. In this project, the PI and his team will address transformation of P composition in soils and its coupling to organic carbon cycling during long-term ecosystem development. The proposed work will transform the current understanding of P dynamics and its coupling to carbon cycling in terrestrial ecosystems. This work also has important implications for P utilization in agriculture and will advance the understanding of P fate after P fertilizer application. The proposed education work will have broad impacts on Earth Science education of various levels of students in the state of Wyoming through developing courses, curriculum and STEM activities, and preparing earth science teachers. The research, education and outreach components of this proposal have been developed synergistically to maximize the impact on the PI's, as well as existing on-campus outreach organizations.The well-received Walker and Syers model describing P transformation during pedogenesis or soil development is based on operationally-defined P fractions as measured by chemical extractions, rather than P speciation. Thus, it has significant limitations in describing P biogeochemical transformation involving P interactions with minerals and organics. Moreover, the model was developed from humid environment and has limited applicability to semi-arid ecosystems as the model does not consider aeolian dust deposition as another important P input in the semi arid environment. There is, therefore, a great need to develop P speciation-based models that can accurately describe P transformation in both humid and semi-arid ecosystems. In this project, P X-ray absorption spectroscopy will be used to determine P speciation in soils, the P pools of the Walker and Syers model, and aeolian dust. Chronosequences in contrasting climate conditions and/or parent materials will be examined. A P-speciation based transformation model during ecosystem development will be proposed. To gain insights into coupled cycling of organic P and carbon facilitated by interacting with minerals, P speciation in soil organic matter associated with soil particles of different size regimes will be characterized using spectroscopic and biochemical analyses. Results are expected to have significant implications for understanding P cycling and bioavailability in terrestrial ecosystems.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.