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“Sticky Roots” And The Fate Of Soil Carbon In Natural Ecosystems

Plant with long roots

Human activities are driving increasing concentrations of CO2 into the atmosphere. The good news is that nature has built-in mechanisms operating in ecosystems that can transform atmospheric CO2 into organic forms and store it in soil long term.

A very close up image of roots.

MSU plant biologist Carolyn Malmstrom is part of a team of scientists that is using a DOE grant to study “sticky roots” and the fate of soil carbon in natural systems. Credit: Shutterstock/Taigi

In particular, organic matter can become bound to—or “stick” to—soil minerals, where it can remain protected for millennia. Such long-term protection has great value to humans as our climate changes. However, the growth of living plants and soil microbes may depend on accessing nutrients trapped in the mineral-associated organic matter.

Michigan State University plant biologist Carolyn Malmstrom is part of a team of scientists that is using a 3-year, $1 million Department of Energy (DOE) Office of Science Environmental Systems Science Program award to study “sticky roots” and the fate of soil carbon in natural ecosystems. The grant began on August 15.

The DOE allocated $6 million in Fiscal Year 2020 for nine collaborative projects to study the complex chemical, physical, and biological processes in watersheds, salt marshes, wetlands, and a range of other terrestrial environments to improve representation of these processes in earth system models.  MSU’s portion of this collaborative grant is $224,982.

Malmstrom, MSU co-principal investigator (Co-PI), is teaming up with project PI Zoe Cardon, the Ecosystems Center, Marine Biological Laboratory, Woods Hole, Mass.; and Co-PIs Marco Keiluweit, University of Massachusetts Amherst; and William Riley, Lawrence Berkeley National Laboratory, to use experiments and modeling to examine the mechanisms by which plant roots and their associated microbes can dislodge organic matter from soil minerals.

Potted plants on a shelf.

Infected grass growing in hydroponics. Credit: Carolyn Malmstrom

“This is an exciting project because to my knowledge, this is the first major project anywhere to look at plant virus impact on biogeochemical cycling on land,” said Malmstrom, associate professor in the Department of Plant Biology in the MSU College of Natural Science.

“Viruses are found everywhere in nature but have been long overlooked,” she explained. “We are using viruses as a tool to manipulate root carbon secretions. When carbon in organic matter in the soil gets bound up with minerals, it is protected from release to the atmosphere. The question is how this protected carbon can be influenced, and perhaps released, by plant roots.”

The novel use of viruses will allow the team to explore below-ground ecosystem function in new ways. Viral infection makes roots “stickier” by strongly affecting the types and amounts of compounds—including sugars—released by plant roots.

Kota Nakasato holding the plant while looking at the long roots.

Graduate student Kota Nakasato measures length of roots of grass grown in hydroponics. Credit: Carolyn Malmstrom

The team hypothesized that some of these compounds can dislodge stored organic matter from minerals. Since viral infection of plants is widespread in terrestrial ecosystems—with 25-70 percent of plants commonly infected—this new work promises to build knowledge about a prevalent, natural phenomenon with large potential to affect the productivity of ecosystems and the fate of large reserves of carbon stored in soil.

Malmstrom, who originally noticed the “sticky” root phenomenon, has expertise in plant–virus interactions.  Her team uses aphids to extract plant sap that flows to roots so it can be studied with high resolution analysis. Cardon has expertise with biosensors; Keiluweit has expertise in soil physics and the chemistry of carbon associated with minerals; and Riley has expertise in large-scale modeling.

“I have been working on viruses since graduate school,” Malmstrom said. “This project is thrilling because it allows us to see how small things such as viruses—which are just a few billionths of a meter in size—affect big things such as ecosystems that are a trillion times larger measured in thousands of meters.”

Aphid bug.

A magnified image of an aphid feeding on a grass root. Credit: Kota Nakasato

Projects were chosen by competitive peer review through the DOE funding opportunity announcement, which is under the Environmental System Science Program, sponsored by the Office of Biological and Environmental Research, within the Department’s Office of Science.  

Via College of Natural Science 

Banner image: Carolyn Malmstrom and her team are using viruses as a tool to manipulate root carbon secretions. When carbon in organic matter in the soil gets bound up with minerals, it is protected from release to the atmosphere. The question is how this protected carbon can be influenced, and perhaps released, by plant roots. The image above shows Infected and uninfected grasses grown in hydroponics used in the study. Credit: Carolyn Malmstrom

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