Environmental sciences and biology professor Nancy Johnson is renowned for her work on fungi and ‘harmonious’ sustainable agriculture.

NAU researchers unearth the potential of fungus in soil

Northern Arizona University research is helping lead the way for farmers to harness the power of soil instead of chemicals to fertilize crops.

Nancy Johnson, an environmental sciences and biology professor renowned for her work on fungi and “harmonious” sustainable agriculture, will present her research findings at the International Conference on Mycorrhiza, held August 9-14 in Brazil.

For more than 25 years, Johnson has been researching mycorrhizal fungi and their symbiotic relationship with most plants. The fungi provide plants with nutrients and water in exchange for carbohydrates.

Mycorrhizal fungi, as a group, associate with nearly all plants on Earth, but scientists are still figuring out the environmental factors that control their distribution and function.

“We continue to discover more efficient and cost effective ways to harness mycorrhizas for their benefits in sustainable agriculture and ecosystem restoration,” Johnson said. “Mycorrhizal fungi are present in most soils, so the addition of these organisms through inoculation is generally not necessary. However, a better understanding of their interactions with host plants and soil fertility will allow us to manage mycorrhizas to encourage a healthy symbiosis that benefits plants.”

	Arbuscular mycorrhizal fungi do not form mushrooms. Instead they form microscopic spores.

Johnson’s research focuses on arbuscular mycorrhizas, the most ubiquitous and ancient form of the symbiosis that evolved concurrently with terrestrial plants over 400 million years ago.

Mycorrhizal fungi form web-like filaments that spread through the ground and forage for nutrients and water. The filaments are so thin they cannot be seen with the naked eye, yet they are critical to structuring soil and reducing its loss through erosion, explained Johnson, who has written numerous book chapters and papers about mycorrhizas and manages NAU’s Soil Ecology Laboratory.

Various sources of funding, including many grants from the National Science Foundation, support Johnson’s studies of mycorrhizal ecology throughout the United States and other countries, including Venezuela, Tanzania and Sweden.

Bala Chaudhary, an NAU biology doctorate student and coauthor of the research Johnson is presenting in Brazil, is using statistical modeling to determine the most important environmental factors to predict mycorrhizal species distributions.  

She is conducting research in southern Utah and Venezuela to compare the factors that control fungal species distributions in tropical and temperate systems.

“Scientists generally know where polar bears live and that climate influences their home ranges. Seemingly simple statements such as these still cannot be made for most microbes, including mycorrhizal fungi, yet microbes make up the majority of biodiversity on Earth,” Chaudhary said.

She said it also is important to study mycorrhizal fungal distributions because certain species are currently being used as commercial biofertilizers. 

“Humans could potentially be spreading non-native, invasive mycorrhizal fungi into new environments,” she said.

Currently the Soil Ecology Laboratory is conducting field experiments measuring the mutualistic function of the fungi in different ecosystems. Students are joining in on the research to compare mycorrhizal function in grassland soils from Kansas, Minnesota and Illinois.

	Nancy Johnson at a research site in Minnesota.

NAU biology doctorate student Anita Antoninka is writing her dissertation on how global climate change could be affecting these fungi and other soil organisms—an important topic because soil organisms cycle, among other things, carbon and nitrogen.

“The rate at which soil organisms process materials and respire (breathe) determines the rate at which carbon is sequestered in the soil,” Antoninka said. “This means that soils have the potential to increase or decrease the rate of carbon dioxide released into the atmosphere.”

Antoninka began her research while working as an undergraduate with Johnson.

“A big part of the reason I stayed at NAU to do my Ph.D. is that Nancy is one of the premier mycorrhizal ecologists, as well as an exemplary mentor,” Antoninka said.