U of I doctoral student’s research helps lay groundwork for Deep Soil Ecotron

Gabrielle Feber is digging deep into a largely unexplored scientific frontier.

By looking beneath the Earth’s surface, the doctoral student with University of Idaho’s College of Agricultural and Life Sciences aims to shed light on major questions affecting food production and the environment. For example, she’s exploring how rising ambient temperatures affect the ability of deep soils to store carbon, a process that limits the flux of carbon dioxide into the atmosphere. Her work should also provide farmers with insights on how to adapt to changing soil conditions following multiyear droughts.

Feber, of Detroit, is part of the research team commissioning U of I’s unique, new Deep Soil Ecotron — a facility designed to enable scientists to study soils at greater depths than anywhere else in the world. The facility comprises 24 ecounits containing soil columns that are nearly 10 feet tall and more than 3 feet wide, with technology enabling researchers to manipulate factors such as climate, plant communities and soil types to better understand the impact of subsurface soils on ecosystems.

“Deep soil is really important, and it’s something that is really understudied,” said Feber, who is enrolled in U of I’s water resources engineering and science doctoral program. “We know a lot about topsoil, but it’s unknown what happens as you go deeper.”

Feber, who holds a bachelor’s degree in chemical engineering from Michigan Technological University, knew little about soil when she saw a post about a graduate research position at the Ecotron and chose to apply.

“It looked like it combined my engineering background with some of the natural sciences, and that was really the direction I wanted to go,” Feber said.

She’s been working on a multifaceted dissertation. Feber specifies soil depths throughout the country. She evaluates the mechanisms associated with storing and releasing deep-soil carbon. She also analyzes water, carbon and nitrogen in deep soil samples dug from throughout Idaho. took deep soil samples from throughout Idaho and analyzed water, carbon and nitrogen in those soils. She’s developing a model to understand the durability of carbon in deep soil in the face of changing conditions.

The journal Geoderma published Feber’s analysis of soil depth throughout the United States in February 2026. In her paper, “How deep is your soil? Quantifying and spatially analyzing understudied deep soil in the United States,” Feber defines deep soil essentially as the layer of soil extending to bedrock. After mapping the nation’s soils based on existing datasets, she concluded the average U.S. soil extends to nearly 66 feet deep. Most soil studies, however, have gone less than 5 feet deep.

Feber took deep soil samples from several sites in Idaho, as well as a site in Alaska, to measure carbon and nitrogen concentrations at different depths. She also studied water flow in deep soil. Her work helped guide the six locations at U of I’s Sandpoint Organic Agriculture Center where 9-ton, intact soil cores were removed to fill ecounits at the Ecotron.

Alfalfa, which is a deep-rooted plant, was planted both at the sampling locations in Sandpoint and above the soil cores in the Ecotron to facilitate research into how well carbon fixed by the crop remains stored in the soil. Instruments were set up in the field to record soil and air temperatures and soil gas exchanges.

Using the field data, she also worked with a specialist at the Lawrence Berkeley National Laboratory in Berkeley, California, to develop a soil reactive transport model, which is a computer model that simulates the movement of water, gases and dissolved substances through soil and the reactions that occur as they move. She hypothesizes that the data will show soil carbon is released as carbon dioxide in correlation with rising temperatures.

Carbon is especially concentrated in the frozen tundra of Alaska and the Arctic, where Feber warns warming temperatures could result in large-scale carbon dioxide emissions at the expense of soil health.

Conditions evaluated by her model will be mimicked in the Ecotron, both to help calibrate the facility and validate and refine her model.

“You think about how people are interested in soil health and carbon markets, and they are thinking we are building up our carbon, but, ‘Are you?’ is the question,” said Feber’s advisor, Zachary Kayler, an associate professor in the Department of Soil and Water Systems and a director of the Ecotron. “We put this new carbon down with plants, and then we heat the soil up to metabolically kickstart the microbes below ground and get a better idea of how long carbon below ground will hang around.”