When wildfires swept through the North Bay in 2017, a graduate student saw a unique opportunity to study how fire affected his research subject: soil fungi.

So, Smith and his mother spent his winter break collecting soil samples from burned areas near trees in Santa Rosa’s Trione-Annadel State Park and Hood Mountain Regional Park and Preserve. For comparison, they also gathered samples from unburned locations.

«I wanted to know how these ecosystems that, on the outside, looked so burned and so destroyed might have been affected at a level that is not so obvious — the soil fungi that I study,» said Smith, who is a member of the lab of Kabir Peay, an associate professor of biology in the School of Humanities and Sciences. Most people know soil fungi by their fruit — mushrooms — but there’s much more to these organisms, both physically and functionally. Working alongside plant roots and other microbes that live in the soil, soil fungi play important roles in their ecosystems, including helping trees grow and aiding in decomposition.

The research, which was published Dec. 9 in Molecular Ecology, focused on two ecosystems in these parks, oak woodland and mixed evergreen forest. As the researchers expected, analysis of dozens of soil samples established that, among the areas that had not burned, the ecosystems contained a different mix of soil fungi. The analysis also showed that, when comparing burned and unburned areas, the oak woodland soil fungal community was less altered by the fires than those in the evergreen forests. This aligns with the fact that oak woodlands depend on regular fire to thrive, whereas evergreen forests are less dependent on fire to survive. The researchers have continued this work by planting seedlings in some of the soil samples — those results will be detailed in a future paper. They are also hoping to find out more about the physiological mechanisms that could explain the responses of the fungi.

«There has been renewed interest in how climate change is influencing the frequency of fires and how that’s going to affect fire-mediated ecological processes in California going forward,» said Peay, who is senior author of the research. «So it’s important to have specific details about how changes in the fire regimes in California, and the West Coast in general, are going to be influencing ecosystems.»

Looking deeper

Oak woodlands benefit from fire to the extent that many parks, including Trione-Annadel, are treated with prescribed burns to keep their oaks healthy. Fire clears leaf litter and dead branches, creates improved conditions for some seeds, and controls insects and pathogens that might otherwise cause disease. Most importantly, fire can prevent other trees — such as those found in evergreen forests — from invading the oak forests. While mature evergreens can survive, and even benefit from, fires, encroaching seedlings may not.

Story Source:
Materials provided by Stanford University. Original written by Taylor Kubota. Note: Content may be edited for style and length.