EAR-PF: Mechanism of Soil Organic Matter Stabilization within Subsurface Soil Aggregates

Slowey Yoko M, Palo Alto CA

Investigators

Abstract

Abstract Yoko Masue-Slowey Dr. Yoko Masue-Slowey has been awarded an NSF Earth Sciences Postdoctoral Fellowship to develop an integrated program of research and education at the University of California, Santa Barbara (UCSB). The project aims to advance our understanding of mechanisms controlling subsurface soil organic matter (SOM) stabilization while preserving the natural assemblage of soils. Understanding SOM turnover rate and its stabilization mechanisms are important because large amounts of carbon (2500 Pg) are stored in the top 3 m of soils. Predicting changes in SOM turnover rate requires understanding SOM stability mechanisms that consider the three-dimensional architecture of soils. This study will determine SOM stabilization mechanisms within subsurface soils that maintain their native structure and to test if variation in aggregate-scale processes is the prime determinant of net SOM turnover time. SOM turnover time within soil aggregates will be quantified at millimeter-scale resolution using 14C, and key SOM stabilization mechanisms in corresponding sections of soil aggregates will be identified by integrating a range of novel techniques including synchrotron based X-ray fluoresce imaging, 13C nuclear magnetic resonance spectroscopy, molecular bioassay, and redox measurement by microelectrode voltammetry. The redox profile and metabolic diversity within aggregates will be studied to investigate if the redox-controlled metabolic rate is a protection mechanism in soils. A major outcome of this research will be to quantitatively evaluate the importance of aggregate/ped-based heterogeneity in microbial processing of carbon controlling the SOM turnover in subsurface soils. Specific training objectives include gaining experience conducting field site-driven research, learning how to link laboratory-scale investigation to field-scale observations, and expanding the knowledge of coupled soil-ecosystem interactions. This project will enable collaboration between UCSB, Stanford University, and the U.S. Geological Survey, and create an opportunity for high school students to participate in hands-on laboratory-based research.