Few mushrooms are as beloved as the morel. From recreational pickers jealously protecting their secret hunting spots, to world-class chefs coveting them for their springtime recipes, morels have acquired an almost mythic status and even have a few festivals in their honor (one in Michigan has been running for 55 years). Yet despite the enormous popularity of morels, surprisingly little research has quantified how the mushrooms respond to one of the greatest disturbances in their natural habitat: a forest fire.
Understanding that response is fairly crucial, as morels tend to proliferate most significantly in the first year following a fire. So several researchers—including six with ties to the School of Environmental and Forest Sciences (SEFS)—sought to address that hole in the literature with a new paper just published in Forest Ecology and Management, “Post-fire morel (Morchella) mushroom abundance, spatial structure, and harvest sustainability.”
Led by Professor Andrew Larson (’03, B.S.; ’09, Ph.D.) from the University of Montana, the study provides the most comprehensive picture yet of morel numbers and distribution after a wildfire, as well as the most concrete data to help forest managers set policies for sustainable morel harvesting (which is especially important since the mushrooms grow and are collected almost exclusively in the wild).
The project came together after the Rim Fire in the Sierra Nevada—the third-largest wildfire in California’s history—burned through parts of Yosemite National Park from August to October 2013. Among the affected areas was the Yosemite Forest Dynamics Plot, a long-term research site with years of accumulated data overseen by principal investigators Larson and Professor Jim Lutz (’05, M.S.; ’08, Ph.D.) from Utah State University.
“One of the benefits of a long-term plot is you can layer on additional studies,” says Alina Cansler (’15, Ph.D.), the second author on the study and a research ecologist at SEFS. So the research team was able to assess the morel population alongside other typical post-fire measurements, such as number of trees killed, fuel burned and decrease in forest biomass. Also, at the time of the wildfire, forest managers had backburned part of the area to stop the fire from burning further into Yosemite National Park, but otherwise allowed it to burn naturally under fairly dry fuel conditions—opening a rare opportunity to study a characteristic morel response.
The following May, in the spring when morels typically fruit after a fire, the researchers surveyed 1,119 small sample plots in the study area. They found, first of all, an incredible volume of morels, and they estimated the white-fir/sugarpine forests in Yosemite have an average of 1,693 morels per hectare (or 4,183 morels per acre). That translates to 1,083,520 morels per year, given the typical area that burns within that type of forest in Yosemite! Alina notes, moreover, that that is an underestimate of the total number of morels in the park, since morels also fruit after fire in other forest types, and fruiting of some species of morels are not tied to fire.
Two other big discoveries were that the highest occurrence of morels occurred on ground that had been 100-percent burned by the fire, and that the morels were generally found clumped closely together and distributed unevenly across the forest. In the paper, the researchers note that the practical application of this uneven distribution is that “if you find one mushroom, carefully search the area within about 3 m (10 feet) and continue to search out to about 7 m (23 feet), as additional mushrooms are likely to occur in this neighborhood.”
The latter findings will require further research to figure out the mechanisms behind them, says Alina, such as whether mycelial colonies (the belowground parts of the morels) are present in the soil before or after the fire, and how variations in the presence of the mycelium, forest vegetation and fire severity affect distribution patterns. “We still don’t know exactly what [the morels] are responding to in the environment,” she says. “There’s a lot more work to be done.”
More immediately, though, the paper’s estimation of the number of morels in the forest—coupled with a thorough literature review of similar sites in the Pacific Northwest and Alaska—could have direct management implications. Until now, managers didn’t have a clear picture of how many mushrooms are in the park on a given year. Current regulations in Yosemite limit pickers to one pint of morels a day, yet Alina says this research supports the potential for a more liberal, yet still sustainable, recreational harvest in the park.
“What stands out from this study,” she says, “is that morels are such a culturally important non-timber forest product, yet there had been very few reputable, statistically valid samples of their abundance after fire.”
But this latest research, with its large number of sampling points in an intensively monitored forest plot, fills at least one gap in the literature and provides strong evidence to guide the management of forests with morels—in California and around the Pacific Northwest. Next up: Figuring out precisely how and why morels respond so vigorously after a fire!
Photos © Alina Cansler.