Two people digging with shovels near trees and tarps in a sunny field
An oak tree’s death reshapes life below ground. UC Davis researchers found major shifts in soil fungi beneath dead blue oaks, but no detectable difference in soil carbon compared with living trees three years after death. (Laura Bogar / UC Davis)

When Trees Die, Soil Fungi Shift—but Carbon Remains

A New Study Finds Soil Carbon Unchanged Three Years After Tree Death

A new study from UC Davis researchers shows that when oak trees die, it triggers major changes to the community of soil microbes living beneath them. These changes have implications for soil health that could ripple out to impact entire ecosystems, especially given the recent rise in tree deaths due to droughts and wildfires. Surprisingly, however, the researchers didn’t detect any change in the amount of carbon stored in the soil three years after the trees had died, suggesting that decomposition takes substantially longer.

“Trees link the atmosphere to deep layers of the soil, and by interacting with microbes, they change the way the whole landscape works,” said Laura Bogar, assistant professor of plant biology and senior author on the paper. “When we see a bunch of trees die, that’s not just an aesthetic problem on the surface; it’s really shifting the function of the soil, and potentially the future of that landscape broadly.”

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