Motivation and approach

I am motivated by curiosity about natural processes: how soils and ecosystems change over time, and how the carbon cycle works. Understanding these processes is intrinsically rewarding—but it has also become an urgent need in the face of global climate change. Despite the critical role of soil in Earth’s habitability, we have much to learn about how it will change in the future, and what role it might play in solving the climate crisis. Climate solutions that depend on soil must be studied and vetted at scale, even as we struggle to understand soil’s role in the carbon cycle. Striking the right balance between applied research and fundamental science is essential to meeting this challenge.

I approach scientific problem solving with a varied tool set. To answer large-scale questions, I build mechanistic models and test them with large public datasets. On the other hand, many fundamental processes can’t be understood in this way; rather, they need to be revealed with the edge a shovel, or probed in the laboratory. To this end, I also explore belowground ecology in the field and via controlled experiments.


Major research themes

(1) Soil development at the global scale. Earth’s soils are constantly changing—yet global scale models of soil properties are largely static. To predict the future of Earth’s soils, we must animate global models with our knowledge of how soils develop in different environments. I have followed this theme across a range of projects: identifying the major environmental controls on soil pH, constraining the legacy effects of the last ice age on silicate mineral weathering, and mapping geographic domains where soil minerals may favor organic carbon storage. My current research related to this theme focuses on the global calcium cycle, soil pH, and the role of cations in mediating soil organic carbon storage.

(2) Microbial physiology, the soil environment, and the carbon cycle. Plants fix carbon from the atmosphere and release it in soil; microorganisms make a living decomposing and recycling this carbon. Belowground carbon storage thus depends on microbial physiology and the way microbes respond to changes in the soil environment. I have explored this theme by studying the effects of drought on soil carbon fluxes, microbial carbon metabolism and nitrogen cycling. My current research interests related to this theme focus on how depth within the soil column limits microbial activity.

(3) Soil and climate mitigation. How can we reduce the climate footprint of agriculture? Can we fight climate change by trying to reverse soil carbon loss? What role can soils play in yielding durable geologic carbon storage? At Lawrence Livermore National Laboratory, I have assessed the potential and the limitations of soil-based carbon capture, studied carbon accrual under perennial bioenergy crops, and argued for improvements in the way soil carbon accrual rates are interpreted in agricultural settings. My current research aims to predict the effects of management on soil properties and soil carbon storage in different environments.

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