Understanding the Geochemical Basis for Soil Organic Matter Storage at the Global Scale
Authors
Brooke Hunter* (brooke.hunter@yale.edu), Eric Slessarev
Institutions
Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT
Abstract
Terrestrial ecosystems capture atmospheric CO2 and incorporate it into soil organic matter (SOM). SOM can be decomposed by microbes—returning carbon (C) to the atmosphere—or stabilized by minerals and retained in soil. Predicting the balance between decomposition and SOM retention in soil is critical to forecasting future atmospheric CO2 levels yet remains a major challenge for biogeochemical models. These models use climate and soil clay content to constrain rates of SOM cycling; however, it is the overall reactivity of soil minerals and not simply clay content that controls SOM retention. Incorporating the effects of mineral reactivity on SOM cycling at the global scale is not currently possible because of a lack of detailed global maps of the soil geochemical environment. To close this knowledge gap, researchers have synthesized seven geochemical datasets that cover five continents. With this combined database (n = 21,000+ observations), researchers will test the extent to which geologic factors influence soil mineralogy and SOM storage. Specifically, the team will use this harmonized geochemical database to model and predict soil mineralogy and mineral reactivity globally. These modeling efforts will rely on a process-based geochemical model complemented by machine-learning derived predictions. The team will use the model outputs to evaluate how patterns and trends in mineral reactivity relate to SOM storage. Researchers will develop a publicly available version of the final harmonized database and derived model predictions to be hosted by the Environmental System Science Data Infrastructure for a Virtual Ecosystem (ESS-DIVE). The results will provide insight into the geologic and topographic controls on C dynamics important for climate predictions.
Furthermore, soil mineralogy data products will make models better equipped to include geochemical data and analysis of SOM stabilization.