Dr. Whitman’s lab grew pine seedlings in a carbon dioxide atmosphere containing carbon-13, an isotope whose unusual weight makes it easy to trace, and then put the trees in a specialised furnace to form charcoal, which was fed to the Pyronema to confirm that it was actually doing what it appeared to be doing. Mushrooms are like us in that they need oxygen to live and need carbon dioxide to expel. The fungus’s carbon-13-labeled emissions, therefore, indicated that it was actually eating charcoal.
Dr. Whitman believes the fungus was eating something else, perhaps the agar it was growing on, or some carbon that entered during inoculation, based on the amount of carbon dioxide it released.
Doctor Fischer explained, “Pyronema can eat charcoal but it really does not like to.” The authors speculated that the fungi may first enjoy the layer of dead organisms, then switch to charcoal when necessary.
Kathleen Treseder, an ecologist at the University of California, Irvine who was not involved in the study, said: “Fungi are amazing at degrading all kinds of compounds.” They should be able to decompose this material because it has been pyrolyzed. Also not involved in the study, soil microbiologist Aditi Sengupta of the California Lutheran University noted the importance of confirming the findings outside of the lab and in the wild.
For microbes and other organisms that can’t get their nutrients from the food source of charcoal, Pyronema is an important player in post-fire recovery if this fungus is breaking down some of the charcoal, Dr. Fischer said. Pyronema, she said, may be able to do the same.
Dr. Sengupta stated, “We want these kinds of activities in the soil.” However, she noted that “eventually, that might lead us to lose the carbon in the soil.” We need to know if the carbon stored in the ground as charcoal will stay there as climate change and other human actions drive more frequent and intense wildfires, or if that’s not something we can really count on, because the fungus can degrade it and release it as CO2.”