Wildfires impact soil carbon stocks. Fire removes carbon from an ecosystem via carbon dioxide, but also produces a special type of carbon called pyrogenic organic matter. Thea Whitman of UW-Madison tells us how priming by charred soils may either increase or decrease soil emissions. She initially found that the concentration of carbon affected how soil emissions responded to the addition of charred soils. By running experiments where she added char to different types of soil, she found that soils with low carbon concentrations lost more carbon proportionally than those with high carbon concentrations. The microbial community also shifted as carbon dioxide emissions changed.
Thea’s next question was how fire impacts soil microbes. Studies of fires are often limited in scope, but she was able to find a naturally occuring system with a range of fire severity and ecosystem types. Burn severity does matter for microbes. Even more, different types of microbes respond differently to fire. Some fungi are known as fire responders, and Thea goes more in depth to show that plant-associated fungi decrease in abundance while decomposing fungi increase. Similarly, there are fire responsive bacteria, especially strains that are related to bacteria that degrade aromatic compounds.
The next step in this research is isolating microbes and confirming that they can degrade pyrogenic organic matter. These experiments will help identify functional traits of microbes that respond to fire.