Based on research led by the University of Montana, with co-authors from the University of Washington and other institutions, a paper was published on Oct. 1 in the journal Forest Ecology and Management documenting and analyzing the patterns of morel growth following a wildfire. Andrew Larson, an associate professor at the University of Montana, and other collaborators drew from a meticulously mapped, well-studied section of forest in Yosemite National Park for their morel research. The roughly 60-acre plot burned during the 2013 Rim Fire, but for four years prior, these researchers — along with more than 100 students and professionals volunteering their time — have mapped every live tree, downed wood slab and shrub patch. For a week in May 2014, the researchers searched for morels in 1,119 plots within the Yosemite research site. They found the mushrooms did in fact cluster in parts of the forest that had burned completely, where no “fuel” was left on the ground. These are areas where the fire consumes everything along the forest floor, leaving only blackened soil, ash or burnt needles. Additionally, they found that morels clustered in groups across burned areas, meaning that after finding one mushroom, the likelihood of finding more increased within 10 to 23 feet of the first. This is the first study in Yosemite, and the entire Sierra Nevada, to examine morel abundance after fire. The park has a morel recreational harvest limit of 1 pint a day per person. The researchers believe that limit could potentially quadruple without depleting park morels, given what they now know about the mushroom’s abundance in the region. They estimate that burned white fir and sugar pine forests throughout Yosemite — the type of forest that burned in their study site — could produce more than one million morels a year in the park. The researchers expect similar clustering patterns among morels in forests in Washington and Oregon that also see mushrooms pop up after fire disturbances. Cansler, for example, has found fruiting morels in Washington’s North Cascades after a fire at nearly 6,000 feet in August — not a typical time for fruiting, but indicative of their tight relationship with fire.
Frequency of morel counts within 3.14 m2 circular plots within the Yosemite Forest Dynamics Plot (left) and relationship of morel abundance to proportion of 3.14 m2 plot surface burned (right; results have been “jittered” by adding small random variation in the x and y dimensions to avoid plotting over identical data values). May 2014 inset photo by A.J. Larson.
Andrew J. Larson, C. Alina Cansler, Seth G. Cowdery, Sienna Hiebert, Tucker J. Furniss, Mark E. Swanson, James A. Lutz. Post-fire morel (Morchella) mushroom abundance, spatial structure, and harvest sustainability. Forest Ecology and Management, 2016; 377: 16 DOI: 10.1016/j.foreco.2016.06.03811.21.16