Soil pore structure key to carbon storage

A window to the microbial world of carbon cycling

A picture of cover crops
Photo by USDA/NRCS

Dr. 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 into the microbial world of carbon cycling.

Dr. 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 and micro-scale enzyme mapping. Micro-tomography is 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 is an imaging process that finds microbiological activity in the soil. When these images are overlaid, the pore structures which affect microbial activity and carbon protection in the systems are revealed. This imagery also illuminates how plant diversity impacts the development of soil pores, which 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 a strong pore network that is ideal for carbon storage and protection. Read the full study.

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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