Biogeochemical Cycling in Earth's Critical Zone

Earth's critical zone is the heterogeneous, near-surface environment in which complex interactions involving rock, soil, water, air, and living organisms regulate the natural habitat and determine the availability of life-sustaining resources. As far as we know, Earth is unique in the level of biological complexity that drives many of the chemical reactions that occur in the critical zone. Life depends on electron transfers that primarily start with solar capture and flow-through reaction chains that change the forms of many elements that are otherwise locked in rocks or dead organic matter. Consequently, our research is focused on the biogeochemical processes that determine the cycles and availability of nutrients (e.g., P and S), carbon (C), and trace metals (e.g., Mn) in Earth's critical zone, particularly the soil part. We combine molecular-scale characterization (with synchrotron X-ray and NMR spectroscopy and ultra-high resolution FT ICR mass spectrometry), molecular biomarkers (amino sugars, lignin phenols, etc.), and isotope techniques (stable or radioactive) to understand their sources and sinks, chemical speciation, transformation, distribution and availability at regional, continental and global scales, and to evaluate their responses to environmental changes (e.g., climate and land-use changes,and wildfires). Along with advanced analytical techniques, we use well-constrained environmental gradients (e.g., climate, soil substrate age, and aeolian dust transport pathways) and large networks of observatories (e.g., National Ecological Observatory Network, or NEON) to provide natural experiments designed to understand how biogeochemical cycling and processes in soils respond to different environmental forcing functions, and how physical and ecological processes jointly affect biogeochemical patterns at continental and global scales. We am particularly interested in C and nutrient dynamics in dryland ecosystems and how they respond to environmental changes, such as forest wildfires.

Ongoing Research projets:

  • Nitrogen limitation in high-elevation hay meadows: Understanding processes for improved agroecosystem health, function, and management (USDA NIFA)
  • Climate effects on Mn oxidation state and Mn/SOM interactions (NSF)
  • Critical Zone Network Cluster: Patterns and controls of ecohydrology, CO2 fluxes, and nutrient availability in pedogenic carbonate-dominated dryland critical zones (NSF)
  • Formation and sources of mineral-associated organic matter across environmental gradients (UW EPSCoR)
  • Mineralogical and geochemical control of phosphorus dynamics during pedogenesis (NSF CAREER)
  • Improving phosphorus availability in high-P fixing alkaline and calcareous soils (USDA NIFA Multistate/Hatch fund) 

Past reserach projects

  • Mineral protection of organic phosphorus and organic sulfur in soils (UW Faculty Grant Aid)
  • Impacts of climate on organic phosphorus dynamics in soils at the global scale (UW Global Perspective Grant)
  • Impacts of long-term flood irrigation on soil organic carbon and nitrogen dynamics in high elevation hay meadows (UW AES Competitive Grant)
  • Phosphorus (P) bioavailability in soil basalt weathering profiles of a 3-million-year-old chronosequence (Roy J. Shlemon Center for Quaternary Studies)
  • Modulation of vegetation effects on organic P composition during pedogenesis in a semi-arid ecosystem (Agriculture and Agri-Food Canada )
  • Phosphorus Speciation and Bioavailability Evolution During Soil Development in the Quaternary Period (UW Roy J. Shlemon Center for Quaternary Studies)
  • Trace Element Geochemistry of Soils in the Coalbed Natural Gas Produced Water Disposal Ponds in the Powder River Basin, Wyoming (Wyoming Restoration and Reclamation Center)
  • Temporal and Spatial Variations of Soil Phosphorus Speciation in a Cold Semi-arid Climate (UW AES Competitive Grant)

Collaborators (incompelte list):

 Oliver Chadwick (UC-Santa Barbara), Peter Vitousek (Stanford), Steve Hart (UC-Merced), Lixin Jin (UT-El Paso), Jay Norton (UWYO), Wei Li (Nanjing Univeristy), Yongfeng Hu (Canadian Light Source), Mohsen Shakouri (Canadian Light Source), and Amy Mckenna (National High Magnetic Field Laboratory)