Mixed-severity wildfire shapes habitat use of large herbivores and carnivores

• Published in: Forest ecology and management 2022-02, Vol.506, p.119933, Article 119933
• Main Authors: Lewis, Jesse S., LeSueur, Loren, Oakleaf, John, Rubin, Esther S.
• Format: Article
• Language: English
• Subjects: Bottom-up; Disturbance; Fire severity; Heterogeneity; Pulsed resources; Top-down
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2021.119933

•Large mammals exhibited high habitat use in areas of higher fire severity.•Some species also exhibited relatively high use of unburned forest.•Mixed-severity wildfire may provide important pulsed resources for large mammals. Ecological disturbance is a driving force that structures ecosystems and shapes landscape pattern. Wildfire is a widespread form of ecological disturbance, and in some vegetation communities fires are increasing in extent and severity. Across the gradient of fire severity, fire can have both positive and negative effects on animals, where some species require mature climax vegetation conditions and other species select for early successional stages. However, further work is necessary to understand how large mammalian herbivore and carnivore populations respond to the gradient of fire severity. The overall objective of this research was to understand the relative roles of fire, landscape, and human factors across the gradient of fire severity on occupancy and/or relative habitat use of large herbivores (i.e., elk and mule deer) and carnivores (i.e., black bear, mountain lion, and gray wolf) seven years post fire. We predicted that animals would increase use of areas characterized by higher fire severity (moderate, moderate/high, or high fire severity) and heterogeneity, where food resources were expected to be greatest. In addition, road density could either increase or decrease animal use of areas, where some animals might increase use near roads due to increased forage along roadsides or decrease use due to higher human activity. Remote wildlife (RW) cameras sampled the gradient of fire severity seven years post a large mixed-severity wildfire (Wallow Fire, year 2011, 2,177 km2) in the White Mountains of Arizona, USA. We evaluated RW camera data using single-species occupancy and Royle-Nichols (relative habitat use) models. As predicted, large mammals (black bear, elk, mountain lion, mule deer, and wolves) exhibited high occupancy and/or habitat use in relation to higher levels of fire severity and/or fire heterogeneity, which was likely related to bottom-up factors related to increased food resources. Some species (black bear and elk) also exhibited relatively high use of unburned forest. Elk reduced use of areas with higher road density, likely to avoid human activity, whereas mule deer increased use of areas with high road density. Mixed-severity wildfire may provide important resources, including pulses of food in early successio