A group of scientists from Montana are studying a section of the Rim Fire burn scar near Crane Flat in Yosemite National Park, focusing on forest composition, tree mortality and fuel accumulation since the devastating 2013 megablaze burned more than 400 square miles in the Central Sierra.

They are also learning more about morel mushrooms, which thrive in some parts of Yosemite and the Stanislaus National Forest, especially after wildfires. University of Montana forest ecology professor Andrew Larson published research in June showing the abundance of morel mushrooms in a roughly 60-acre study site in Yosemite.

Morels are prized by mushroom hunters and mushroom gourmands because they are difficult to grow. They thrive at some elevations in the Central Sierra Nevada, especially in areas recently burned by fires.

Access to the mushrooms is limited. Gathering mushrooms for commercial purposes is not permitted in Yosemite, and the practice is regulated in Stanislaus National Forest by permit system.

Scientific research that measures abundance of morels after forest fires is also limited, Larson said.

“We wanted to give forest managers concrete data on morel abundance,” Larson said Thursday. “We were in Yosemite in late May 2014 for this work. It’s a long-term study site, we’ve been going every year since 2009.”

All 63.3 acres of the study site are in the Rim Fire footprint, but the section burned on the study site was intentionally ignited by the Park Service during the Rim Fire to deny fuel to the advancing blaze, Larson said.

Larson is lead author of the morel study. The Rim Fire and backfiring during the Rim Fire killed more than 70 percent of the trees in the research site in September 2013.

They surveyed for morels in May 2014 in 1,119 small sample plots, and where morels were found, the researchers found most of the ground surface was 100 percent burned.


People with the Bay Area Mycological Society know where to look for mushrooms and other fungi, and they kept track of morels that boomed after the Rim Fire. Because the Rim Fire burned primarily in the Stanislaus National Forest and in Yosemite, it was difficult for anyone to legally harvest morels during the first spring after the fire.

Morel season is May to June at 4,000 to 5,000 feet elevation, David Rust, a co-founder of the Bay Area Mycological Society, said Thursday. Harvesting morels to take them out of Yosemite is prohibited, though rules permit picking them and having them inside the park, Rust said.

“You can have a pint of mushrooms in your possession anywhere in the park,” Rust said. “You cannot pick them in the park and take them out of park. Picking them and taking them for commercial services is not allowed. When you ask about it, the people who work in the park will not tell you much because they do not encourage mushroom picking.”

Public affairs staff with Yosemite National Park could not be reached for comment.

Permits in Stanislaus NF

Morel enthusiasts said a significant crop sprouted more than two years ago in the wake of the Rim Fire. But morels that grew in burned sections of the Stanislaus National Forest, estimated to be worth up to $40 million, went largely uncollected because the Rim Fire footprint in the forest was closed to the public due to safety hazards.

Permits for morel picking in the Stanislaus National Forest were made available for spring 2015 and spring 2016, Rebecca Garcia, of forest public affairs, said Thursday. Free use permits for collecting up to 1 pound of mushrooms and commercial permits that cost $4 per pound harvested with a minimum charge of $20 were offered.

In addition, the Stanislaus National Forest offers commercial mushroom permits for up to 75 pounds per person per year, with a maximum charge of $300 per permit.

“Morels thrive after wildfires because they are feeding on the released carbon and minerals after a fire,” Rust said. “Post-fire they give off their spores and regenerate. If conditions are right, they can grow every spring in some parts of the Stanislaus and in Yosemite, but not in the tremendous abundance you find post-fire.”

In some cases, a really intense fire can burn soils to 2,000 degrees Fahrenheit, killing morel spores and reducing or eliminating chances of any mushrooms growing in intensely-burned areas, Rust said.


Larson said burned white fir forests in Yosemite can produce an average crop of more than 1 million morels per year, a sustainable amount for recreational picking.

“The magnitude of post-fire morel production, especially the first year after fire, clearly supports the park’s current rule allowing people to pick one pint per day for personal use,” Larson said.

Larson and his team were surprised at the start of their study by how little research existed for morel mushroom productivity.

“We reviewed every published paper on post-fire morel mushroom productivity we could find,” Larson said. “Amazingly, only three earlier studies, in Alaska, Oregon and British Columbia, Canada, provide statistically sound estimates of morel abundance after forest fires.”

Going forward, Larson said, Montana researchers in Yosemite are focusing on fire effects in the wake of the Rim Fire, including forest composition, tree mortality and fuel accumulation, with the goal of informing fire managers in Yosemite and elsewhere in the Sierra Nevada.

“Mortality has jumped this year,” Larson said. “Bark beetles are moving in, in response to the fire and to the drought. Every tree on the site that’s a half-inch diameter or greater has been tagged and visited. So our major push now is studying long-term tree mortality and fuel accumulation since the Rim Fire.”