Environmental Associations with Post-Fire Butterfly Occupancy in the Sierra Nevada, California

Abstract

Fire affects environmental attributes associated with the distribution, abundance, and reproduction of butterflies, and studies have demonstrated that species richness and abundance of butterflies respond to fire. However, the effects of fire on resources used by adult butterflies, and on butterfly occupancy, are largely unknown. In 2014 and 2015, we surveyed butterflies and elements of their habitat within the boundary of the Rim Fire (Stanislaus National Forest, Tuolumne County, California), one of the largest fires known to occur in California during the past century. We examined the extent to which butterfly occupancy and abundance in the first two years following the Rim Fire were associated with environmental attributes that were affected by fire. We also tested whether vegetation and soil burn severity, two indices used by resource management agencies, explained variation in the environmental attributes that we included in models of butterfly occupancy and abundance. We found that the percentage of live ground cover and canopy cover were strongly associated with occupancy of the majority of the species we modeled. In some cases, environmental attributes associated with occupancy also were associated with the abundances of those species. Values of environmental attributes that explained substantial variation in butterfly occupancy and abundance were associated with vegetation and soil burn severity. Understanding how fire affects environmental attributes that are associated with butterfly occupancy and abundance may inform strategies for managing these species with prescribed fire or following wildfire, or when fire treatments are applied for other reasons.