AMHERST, Mass. — An international review led by researchers at Amherst College, the James Hutton Institute and Umeå University has revealed the critical role that plant roots play in shaping how Arctic tundra ecosystems respond to climate change, emphasizing that processes occurring beneath the soil surface could be as important as above-ground vegetation shifts in predicting future climate feedbacks.
The review, published ahead of the 5th International Polar Year (2032-2033) and assembled through the International Arctic Science Committee, finds that rising temperatures and permafrost thaw are altering root productivity, depth, seasonal growth patterns and plant-soil interactions — mechanisms that could determine whether Arctic tundra becomes a carbon source or sink.
Arctic permafrost contains an estimated 1,460 to 1,600 billion tons of organic carbon, roughly twice the amount currently floating in the atmosphere. As the region warms and permafrost thaws, some of that carbon is being released into the atmosphere. Thawing permafrost is also allowing trees and shrubs to encroach into treeless tundra areas, a change that has drawn significant scientific attention for its potential to absorb carbon through increased plant growth.
However, the study's authors argue that root and rhizosphere processes may be just as important. The researchers found that roots can help lock carbon into soils by supporting plant growth and contributing organic matter. At the same time, roots can stimulate soil microbes that break down existing soil carbon, releasing greenhouse gases such as carbon dioxide and methane — a dynamic that could offset any carbon uptake from above-ground vegetation.
Because these processes can go in opposite directions, the review concludes that improving climate predictions will require a more nuanced understanding of how plant roots, soil microbes and thawing permafrost interact. The authors are urging a new focus on soil processes to reduce uncertainty in climate models and better assess the risk of runaway climate feedbacks from the Arctic.
"As the Arctic warms, we can see dramatic changes across the landscape, from expanding shrubs and trees to ground subsidence caused by thawing permafrost," said lead author Dr. Rebecca Hewitt of Amherst College. "Our team is particularly fascinated by what happens out of sight, and with this paper, we wanted to highlight how roots and their associated microbes influence whether carbon stored in Arctic soils remains there or is released to the atmosphere."
Co-author Dr. Thomas Parker of the James Hutton Institute added: "What happens in the Arctic doesn't stay in the Arctic — by understanding how plants and microbes interact with these carbon-rich soils we can not only understand the severity of climate feedbacks but also learn lessons for the UK's own soil resources."
Dr. Gesche Blume-Werry of Umeå University said the paper highlights the central role of root and rhizosphere processes in feedbacks from the Arctic to the global climate, and hopes it will inspire more research on this important, but understudied topic.
