RAISE-SitS: Designing models to forecast how biogeochemical fluctuations in soil systems govern soil development, terrestrial water storage and ecosystem nutrient fluxes

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Managing water resources requires a full understanding of the water cycle. The current understanding may, however, be missing a fundamental factor of the water cycle-soil structure. Soil structure, the arrangement of soil particles and pores, was recently discovered to be changing faster than previously thought - over a few decades - in response to shifts in precipitation patterns. Fluctuations in soil structure alter the amount of water that can be stored near the surface and the ease with which water moves through the soil. Although plants, animals, and microbes may have dominant roles in altering soil structure, it is unclear how these processes work together or are modified by soil properties. New mathematical models are needed to study the causes of these observed alterations in soil structure and to examine plant-soil-water responses to varying environmental conditions. The research may fill this need by developing the next generation of models to include biological, physical, and chemical interactions from local soils in the US. Through the development of these models, five faculty from minority groups underrepresented in STEM fields, four postdoctoral scholars, and ten undergraduate researchers will be trained. The discoveries will be disseminated to the community through webinars, online tools, and local presentations as well as integrated into current curricula across four universities. The models will allow the effects of soil structure fluctuations on ecosystem processes to be evaluated at diverse spatial and time scales. The research may improve forecasting of future availability and quality of water resources, soils, and associated ecosystem services. Soil ecosystem models (empirical and process-based) will be developed at multiple spatial scales to link soil structure and function in order to enhance the prediction of water and biogeochemical fluxes on timescales of decades to centuries. These models will be parameterized using soil, plant, and aquatic microbiome data collected across a strong precipitation gradient in the central USA (part of NSF Kansas Established Program to Stimulate Competitive Research, EPSCoR) and continental-scale soil databases (e.g., the National Cooperative Soil Survey Soil Characterization Database, United States Department of Agriculture). Structural equation, 2-D pedon, watershed and continental scale models will be developed to examine and account for the interaction between soil hydraulic properties (e.g., macropores and Ksat) and terrestrial biogeochemical fluxes. Products from this work will include: a mechanistic understanding of macropore evolution with climate; development of climate-dependent pedotransfer functions for pedon, watershed, and continental-scale models; predictive capabilities for soil microbial community responses to changing soil structure; a mechanistic understanding of soil macropore-topography-hillslope structure-climate interactions; and quantification of climate-induced macropore changes to biogeochemistry and water cycles from the pedon to the continental scale. The modeling tools proposed here are expected to address environmental sustainability over time and enhance the ability to predict land-atmosphere dynamics, subsurface water storage, water table fluctuations, and flood events. These models will provide community-accessible tools to examine how soil, hydrologic and biogeochemical feedbacks govern nutrient fluxes, and will ultimately be useful toward alleviating nationwide problems such as managing the nitrogen cycle and the Gulf of Mexico dead zone. Finally, this work will test a new Rule of Life (RoL): Life's responses to climate driven changes in the soil fabric which prompt the emergence of integrated terrestrial responses that are more rapid than typically considered.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.