The health of red fir (Abies magnifica) and other upper montane forests is declining in California under regional warming trends, recent drought, and fire exclusion. Increased use of wildland fire, especially wildfires managed for resource objectives, is one management strategy that may restore the structure and function of red fir forests in the Sierra Nevada and other montane regions of California. We examined the influence of burning on the structure, diversity, and health of red fir stands by comparing twice burned and unburned plots established in 19 separate, paired fires of Yosemite, Sequoia, and Kings Canyon National Parks.
Results/Conclusions
Burned red fir plots were characterized by lower tree densities and canopy cover, greater mean tree diameter, and fewer tree clusters than unburned plots. Twice burned stands also were higher in understory plant species richness, including herbaceous plants, shrubs, and tree regeneration. Burned plots retained similar densities of large trees and snags compared to unburned plots. Forest health indicators were similar between burned and unburned sites, and crown loss ratings were positively related to topographic variables associated with increased moisture stress (i.e., greater crown loss at lower elevations and south-facing slopes). Our results suggest that use of wildland fire may restore red fir forest structure and diversity in active fire regime landscapes, but it does not influence red fir health especially in areas of greater moisture stress. Nevertheless, fire builds adaptive capacity in red fir forests by increasing the representation of drought tolerant tree species, enhancing structural complexity, retaining key structures, and promoting red fir regeneration.