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Study: Soil Pore Structure Is Key to Carbon Storage

Published: Friday, December 13, 2019

The following is from Sarah Fronczak of Michigan State University Extension.

Alexandra Kravchenko, Michigan State University professor in the Department of Plant, Soil and Microbial Sciences, along with several of her colleagues discovered a new mechanism determining how carbon is stored in soils. Her research findings are published in the scientific journal Nature Communications.

Increasing the potential of the soil to remove carbon from the atmosphere is often acknowledged as one of the most efficient ways to limit global warming. Sequestering carbon in soil with better land management practices including reduced soil disturbance, cover cropping and diverse crop rotations are well recognized approaches. However, the scientific understanding of why this works is limited. This new research showed the importance of soil pore structure for stimulating soil carbon accumulation and protection, giving us a window to the microbial world of carbon cycling.

Karavchenko's recent research has started getting the attention of farmers interested in soil carbon and soil organic matter. The experiment examined five cropping systems in a replicated field trial. Using X-ray micro-tomography (an imaging process that uses x-rays to create cross sections of an object then recreates a virtual 3D model essentially like a medical CT scan) and micro-scale enzyme mapping (an imaging process for microbiological activity in the soil).

By overlaying these images the pore structures which affect microbial activity and carbon protection in the systems are reviled. This also illuminates how plant diversity impacts the development of soil pores are conducive to greater carbon storage.

Conventional thinking was that the best way to put more carbon into the soil was to have plants that produce more biomass, either as roots or residue on the surface for decomposition. However, this study found that the sequestered carbon is the result of soil microbes producing organic compounds that are then absorbed onto soil mineral particles. These soil microbes thrive in soil pores 30-150 micrometers in diameter. Diverse plant systems with root systems that vary in size and root architecture develop the strong pore network that are ideal for carbon storage and protection.

The study was conducted through the MSU Great Lakes Bioenergy Research Center, funded by the U.S. Department of Energy, and the Kellogg Biological Station Long-term Ecological Research program funded by the National Science Foundation.

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