The Role of Dust on Snow and Other Aeolian Inputs in Soil Formation and Biogeochemical Cycling in Barren, Alpine Catchments

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There is an urgency to improve our understanding of how biogeochemical cycling and surface water quality in high-elevation catchments are responding to dust and other aeolian deposition events. The combination of increasing temperatures and dust emissions, melting glaciers, and surprisingly high amounts of microbial activity in recently deglaciated soils represent a new connectivity between geologic, biological, and hydrologic processes in barren, alpine catchments. Dust deposition, known to supply barren, alpine areas with important base cations, may also influence the soil cation exchange pool, soil pH, and export of cations from the watershed and may be more important than bedrock weathering in generating barren soils. Additionally, aeolian deposition is increasingly being recognized as an important source of nutrients, such as carbon and phosphorus, to high‐elevation ecosystems, and these inputs may drive biological processes, such as those that enhance nitrification and influence water quality. An overarching hypothesis that defines this project is that dust and other atmospheric inputs are important pathways to soil formation and biogeochemical processes, such as nitrification, in barren, alpine catchments. This project will evaluate the provenance and chemical quality of aeolian deposition and investigate the initial phases of weathering and biogeochemical cycling in barren, high-elevation soils using novel spectroscopic techniques, stable isotope and cation analyses, soil chemistry and mineralogy analyses, and bioavailability experiments. Hypotheses will be tested in the Green Lakes Four (GL4) catchment of the Colorado Front Range, where aeolian deposition, soil microbial processes, and nitrification, which have been studied independently over the last few decades, will be studied as interacting processes in an interdisciplinary investigation. Given unprecedented rates of glacier melting worldwide, the improved representation of biogeochemical processes that this research will produce is relevant for C- and P- limited mountain catchments on a global scale. Given the global relevance of this research, a subset of activities will be conducted at other Critical Zone Observatory sites in the US as well as at international alpine sites. New insights gained from investigating aeolian wet and dry deposition, microbial community composition, rates of microbial processes, and stream and soil water quality, and from conducting coupled snowmelt-biogeochemical modeling will further improve the capability to forecast changes in the biogeochemical cycling and hydrology of high-elevation watersheds with a changing climate. This project will support graduate students to participate in interdisciplinary research that spans geochemical, biological, and hydrologic studies. In addition, this project will engage high school students participating in the St. Vrain Math, Engineering, and Science Achievement (MESA) Program, which seeks to improve achievement by Latino students. MESA students will develop their own summer research projects, mentored by the PIs and graduate students and supported with stipends through this project. A larger group of MESA students will also visit the CU campus annually during the Institute for Arctic and Alpine Research (INSTAAR) Open House, a day of lab tours and field demonstrations for K-12 students hosted by INSTAAR.