EAR-PF: Assessing the Potential for Enhanced Duration of Soil Carbon Storage via Anaerobic Microsites from the Plant Rhizosphere to Catchment Scale

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Dr. Hannah Naughton has been granted an NSF EAR Postdoctoral Fellowship to study the impact of anoxic microsites on soil carbon cycling at the University of California, Berkeley, in collaboration with Lawrence Berkeley National Laboratory. Upland soils, e.g. a typical farm soil, are considered completely oxic and thus unlimited with respect to microbial carbon oxidation to the greenhouse gas, carbon dioxide. However, upland soils contain up to 85% anaerobic pore space that hinders respiration and potentially exacerbates the release of potent greenhouse gases like methane. The goals of this fellowship are to develop a statistical and geospatial model predicting 1) the extent, and 2) the carbon storage in these anaerobic microsites along a hillslope-to-floodplain hydrologic gradient in East River, Colorado. This project will develop a conceptual framework that could be used as a tool for land managers and scientists to better understand carbon dynamics in their soils using readily available, remotely sensed data, thus minimizing time- and money-intensive field soil sampling and characterization. Such a tool and the basic scientific knowledge generated through this work will improve prediction and management of soil carbon storage under changing precipitation, temperature and vegetation going into the future, with extensions to calculating carbon credits, deciding between conventional and sustainable farming techniques, and better constraining countries’ terrestrial carbon emissions. This project will support women and other minority groups in the Earth Sciences through direct mentorship, campus and field site outreach discussing the uncommonly known diversity of (and in) soils, and through course development and teaching at UC Berkeley. Saturated conditions and organic inputs, two conditions that naturally vary along hillslope gradients, are known to deplete soil oxygen, but the role of roots in forming soil redox microheterogeneity has not yet been tested. Plant functional types (PFTs, e.g. shrub vs. grass) are adapted to landscape positions according to geomorphic and geologic controls on solar radiation, water and nutrient availability. Below-ground, PFTs differ significantly in root traits and role in soil aggregate formation. Previous East River work has demonstrated that PFT distribution is predictable based on remotely sensed surface and subsurface properties, suggesting soil redox microheterogeneity that controls carbon transformation may be predictable over larger scales. Using the hillslope-to-floodplain gradient, I propose to evaluate the relationship between landscape features, PFT distribution, soil physical characteristics, and microbial metabolism, and then determine the consequences for soil carbon composition and storage. These relationships will inform a geospatial model utilizing LiDAR and hyperspectral data to predict anaerobic microsite formation and resulting carbon storage potential. Mentoring and teaching opportunities and the scope of this project will prepare Dr. Naughton for a faculty position in an undergraduate-oriented college where she intends to continue studying the influence of micro-scale soil heterogeneity on carbon cycling and the means to predict and represent this knowledge over larger spatial scales.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.