Research Shows Warming Impact on Soil Ecosystem
Within only a few decades of higher temperatures, microbial systems change in ways that disrupt carbon and nutrient cycles.
Long-term ecosystem warming changes not only plants but the fungi in the soil below, according to a new study including researchers from the University of Tennessee, Knoxville.
“Hidden mycorrhizal fungi below ground are much more vulnerable to warming winters than we expected before,” said Associate Professor Stephanie Kivlin from UT’s Department of Ecology and Evolutionary Biology, senior author on a new study published in the Proceedings of the National Academy of Sciences (PNAS).
“The timing of their growth is disrupted by warmer winters, and they can’t form the beneficial symbioses that currently occur,” she said. “We now have evidence that the mycorrhizal fungi never recover from warmer winters and will decline in many temperate ecosystems.”
The research was funded by a National Science Foundation grant Kivlin wrote with Lara Souza, associate professor in the School of Biological Sciences at the University of Oklahoma (OU) and lead author on the paper.
UT, OU, and University of Michigan labs participated in the field work at the Rocky Mountain Biological Laboratory in Colorado, where heaters have been warming experimental plots of ground for nearly three decades.
The long-term warming has shifted the area from an alpine grassland to a desert shrubland. “What is really exciting about these findings is that they demonstrate that not only do plant communities shift, which has been documented before, but the soils that are associated with these communities can also change,” said Souza, associate professor in OU’s School of Biological Sciences. “The changes we’re seeing below ground are driven by the changes in the plants.”
The mycorrhizal fungi that help plants absorb water and nutrients in exchange for carbon decreased, while there was an increase in saprotrophic fungi, which are involved in organic decomposition.
Most warming experiments last only a few years, and the researcher expected that after 29 years mycorrhizal fungi could adjust or acclimate to the higher temperatures. “The fact is that they can’t, and that has consequences for ecosystem carbon and nutrient cycles,” Kivlin said.
“Our experiment is the first to demonstrate how vulnerable links among components of ecological communities are under environmental change,” she said.
The paper also advances a novel conceptual and mathematical framework to detect when plants and microorganisms will become decoupled under global change. “More work is necessary to determine the timeframe of when decoupling will occur and if mitigation can restore communities back to their coupled state following disturbance,” Kivlin said.
“Our current work is investigating the impacts on snowmelt timing on plant-fungal interactions below ground,” she said. “We’re finding that advancing snowmelt caused by warming allows fungi to grow before plants. When mycorrhizal fungi are active before plants, they take up nutrients from the soil but can’t transfer them to the plant host. These nutrients are then leached out of the soil before plants can use them, leading to smaller plants.”
In addition to Kivlin, authors on the paper include EEB lab technician Ruth Simberloff (MS ’23) and UT microbiology Teaching Assistant Professor Jessica Pyle (PhD ’16), who was a postdoctoral researcher.
The UT Genomics Core worked with Kivlin and her team to develop tailored pipelines for DNA extraction, amplification, and analysis. The researchers also used computational resources from the National Institute for Modeling Biological System (NIMBioS) for the bioinformatics analysis. Kivlin, Souza and Professor Aimee Classen from the University of Michigan also wrote about their research on fungi under the snow in The Conversation.
by Amy Beth Miller