Impacts of fire regime on small mammal communities in California

Across the world, climate change is contributing to altered fire regimes, including increases in the frequency, area burned, and severity of wildfires. As a result, our understanding of the effects of these changes on ecosystems, biodiversity, and wildlife remains incomplete. The Sierra Nevada region of California supports many important species and includes unique small mammal communities that represent a crucial component of healthy ecosystems. Recently, the Sierra Nevada has experienced increasing impacts of climate change, most notably demonstrated through extreme drought and alterations to the fire regime, such as increases in fire severity, intensity, frequency, and area burned. These factors contribute to changes in vegetation and habitat, to which small mammals are highly sensitive. However, the long-term influence of these changes is poorly understood. This study aims to understand the drivers of small mammal community composition, with a focus on fire regime. We make use of historical survey and resurvey data from the Sierra Nevada, which provide high-quality species occurrence records from several periods over the last century. We examine how small mammal richness and community turnover vary with different components of fire regime, climate, and habitat using single- and multiple-variable linear regression. We found that several fire regime variables explain variation in modern small mammal richness across the Sierra Nevada. Specifically, mean time since last fire had a significant positive relationship with small mammal richness, whereas number of fires, fire return interval, and the standard deviation of time since last fire had significant negative relationships with richness in the multivariate models, in combination with non-fire variables. Additionally, mean time since last fire, standard deviation of time since last fire, and number of fires in a sample area had significant positive relationships with small mammal community turnover. Overall, this work establishes that fire is an essential element that influences small mammal community structure in an era of global change and must be considered alongside climate and habitat. Worldwide, global climate change and anthropogenic influences impact natural fire regimes. We used multivariate linear models to test the impact of fire regime on small mammal communities (Rodentia, Eulipotyphla) in the California Sierra Nevada mountains. Small mammal richness was lower in areas with less time since last fire, longer fire return intervals, and a higher number of fires. Small mammal community turnover was higher in areas with more time since last fire and a higher number of fires.