The Forest, the Fire and the Fungi: Studying the Effects of Prescribed Burning on Mycorrhizal Fungi in Crater Lake National Park

A first-of-its-kind study, conducted in a forest of old-growth ponderosa pine and white fir in Oregon’s Crater Lake National Park, explored the relationships among seasonal prescribed burning, an array of soil attributes, and mycorrhizal fungal fruiting patterns. This three-fold approach not only made the study unique, but also enabled researchers to separate the effects of fire treatment from the effects of soil attributes on fungal fruiting patterns. The study’s site encompassed three different prescribed burn treatments—applied in the early spring, late spring, and fall of 2002—as well as non-burned control plots. Analyzing statistics with multiple variables, the researchers identified how the treatments affected specific soil attributes, which soil attributes affected fungal fruiting patterns, and how the burn treatments affected fungal fruiting patterns. The study revealed that soil attributes—specifically carbon-to-nitrogen (C:N) ratios—drive fungal fruiting patterns, and that while fungal communities respond more to C:N ratios in the soil than to burn treatments, prescribed fire can reduce soil C:N ratios. Most importantly for forest managers concerned with the effects of prescribed fires, the study determined that mycorrhizal fungal communities can withstand even hot prescribed burns in the forests above them.Key Findings

• Fungal fruiting patterns seem to be driven primarily by C:N ratios in the soil.
• Fungal communities respond more to C:N ratios in the soil than to burn treatments.
• Mycorrhizal fungal communities can withstand the level of disturbance created by a hot prescribed burn.
• The C:N ratios and mycorrhizal fungal fruiting patterns were remarkably consistent, irrespective of burn treatment or location within the study site.