Nov 28, 2017
Science Tuesday: Fire Fungus
Type: Research Synthesis
All of my friends know that I’m a bit of a holiday scrooge. Holidays involve all kinds of societal traditions that put me on edge, like setting off explosives, dressing up in costumes, and obligatory gift giving. But Thanksgiving is a different story — not only is there a focus on food and drink (my two favorite things!), but it’s also the perfect time of year to get outside and appreciate the bounty of our places: the crab in the bay, the salmon in the creeks, the mushrooms in the woods.
Every year on Thanksgiving morning, my family and I hike a half mile up the hill behind my in-laws’ house and hunt for mushrooms in a second-growth forest above their spring. Each year is different. Sometimes we load up on chanterelles, hauling them in overflowing paper bags down the hill just in time to add them to the stuffing and gravy. Other years, like last year, we don’t find any chanterelles, but we’ll see a few mature matsutakes popping out of the duff, and we’ll gently unearth dozens more of the white, bulbous beauties growing just beneath the surface. And then there are years like this year, when all we see is a few scattered russulas and coral mushrooms, but nothing that makes our mouths water. I love mushroom hunting, not only for the culinary treats that we sometimes find, but also because of its unpredictable and mysterious nature: a reminder that we don’t have it all figured out.
And this year’s empty-handed hike back down the hill got me thinking (as I’m wont to do) about the connection to fire. It’s common knowledge that morels do well after fire, but what about these more mesic species — our beloved chanterelles, matsutakes and boletes?
In my reading on chanterelles, I found surprisingly little on their relationship with fire. In “Predicting Species Occurrences” (2002), Dreisbach et al. wrote a chapter on the challenges of modeling fungal habitat, with an emphasis on chanterelles (PDF, 445 KB). Although they do not explicitly look at fire, they discuss the importance of stand age and disturbance in predicting the presence of chanterelles. And in their models, they assume that any fire or timber harvest within twenty years would preclude their presence. For those of us who hunt these mushrooms in the Douglas-fir-tanoak forests of northern California, this makes some sense: most of those forests haven’t seen fire in the last twenty years. But that’s the interesting thing — given a more natural fire regime, these forests would probably see fire at least every twenty years, and what does that say for the mushrooms? Can they take advantage of frequent fire more than the models assume, or are they present at current levels because fires have been suppressed?
A 2013 paper by Kat Anderson and Frank Lake provides important cultural and historical perspective on this issue. Their paper, California Indian Ethnomycology and Associated Forest Management, includes excerpts of interviews with native elders, and specifically addresses forest management in the mixed-evergreen forests that are common where I live (PDF, 1320 KB). According to their interviews, frequent, human-ignited fire was a critical component of forest health in tanoak stands, and the benefits to the trees extended to the associated mushrooms, especially the matsutakes, which locals call “tanoak mushrooms.” The benefits of frequent fire to specific species of mushrooms aren’t spelled out in detail, but the paper speculates that burning in tanoak stands may have reduced pest problems on host trees and created a fruiting response in mushrooms by reducing duff depths. However, two socioecological benefits are clear from their work: historically, fire kept the forest open to allow for foraging, and it created heterogeneous conditions that favored a wide assortment of desirable fungi.
The importance of habitat heterogeneity for mushrooms can’t be overstated. Novice mushroom hunters (me included!) might be able to discern yellow chanterelles from white, and king boletes from queens, but there is a world of diversity within each genus that is likely escaping us. And within genera, the relationship to habitat conditions and fire is highly variable. For instance, research has shown that different species of chanterelles in the Cascade Range in Oregon have significantly different relationships to stand age, with some species strongly associated with old-growth forests, others distributed more broadly across stands of different ages, and others rare altogether (Dunham et al., 2006). These same types of patterns are common for morels, too. Though well-recognized as a fire-following genus, different species of morels relate differently to fire. A 2004 paper by Pilz et al. showed that although the greatest overall morel diversity occurs in the first year following fire, different types of morels are able to thrive under different disturbance regimes, including areas with little to no disturbance at all (PDF, 321 KB).
It seems to me that there is a lot left to learn about mushrooms and fire. Mushrooms have an enigmatic quality, and the linkages to fire appear deep and complex — tied to the cultural history of a place and to biodiversity and resilience — but they also act as a reminder of all the connections and synergies that we don’t totally understand. And as long as my Thanksgiving hike remains unpredictable and fun (and occasionally fruitful), I think I’m fine with not understanding it all.
Anderson, M. K., and Lake, F. K. (2013). California Indian Ethnomycology and Associated Forest Management (PDF, 1320 KB). Journal of Ethnobiology, 33(1), 33–85.
Dreisbach, T. A., Smith, J. E., and Molina, R. (2002). Challenges of Modeling Fungal Habitat: When and Where Do You Find Chanterelles. Predicting Species Occurrence: Issues of Accuracy and Scale (PDF, 445 KB). Covelo, California: Island Press, 475–481.
Dunham, S. M., O’Dell, T. E., and Molina, R. (2006). Forest Stand Age and the Occurrence of Chanterelle (Cantharellus) Species in Oregon’s Central Cascade Mountains. Mycological Research, 110(12), 1433–1440.
Pilz, D., Weber, N. S., Carter, M. C., Parks, C. G., and Molina, R. (2004). Productivity and Diversity of Morel Mushrooms in Healthy, Burned and Insect-Damaged Forests of Northeastern Oregon (PDF, 321 KB). Forest Ecology and Management, 198(1), 367–386.
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