Small mammal responses to fire severity mediated by vegetation characteristics and species traits

Abstract

The frequency of large, high‐severity “mega‐fires” has increased in recent decades, with numerous consequences for forest ecosystems. In particular, small mammal communities are vulnerable to post‐fire shifts in resource availability and play critical roles in forest ecosystems. Inconsistencies in previous observations of small mammal community responses to fire severity underscore the importance of examining mechanisms regulating the effects of fire severity on post‐fire recovery of small mammal communities. We compared small mammal abundance, diversity, and community structure among habitats that burned at different severities, and used vegetation characteristics and small mammal functional traits to predict community responses to fire severity three years after one mega‐fire in the Sierra Nevada, California. Using a model‐based fourth‐corner analysis, we examined how interactions between vegetation variables and small mammal traits associated with their resource use were associated with post‐fire small mammal community structure among fire severity categories. Small mammal abundance was similar across fire severity categories, but diversity decreased and community structure shifted as fire severity increased. Differences in small mammal communities were large only between unburned and high‐severity sites. Three highly correlated fire‐dependent vegetation variables affected by fire and the volume of soft coarse woody debris were associated with small mammal community structures. Furthermore, we found that interactions between vegetation variables and three small mammal traits (feeding guild, primary foraging mode, and primary nesting habit) predicted community structure across fire severity categories. We concluded that resource use was important in regulating small mammal recovery after the fire because vegetation provided required resources to small mammals as determined by their functional traits. Given the mechanistic nature of our analyses, these results may be applicable to other fire‐prone forest systems, although it will be important to conduct studies across large biogeographic regions and over long post‐fire time periods to assess generality.

Increasing fire severity alters the species composition and decreases richness of seeds potentially dispersed by small mammals

“…Small mammal seed dispersal, however, can be influenced by several biotic and abiotic factors, including inter-and intraspecific interactions, climate, and fire (Godó et al, 2022). This disturbance may affect seed-small mammal interactions in several ways, including reducing the effectiveness of seed detection by the animals (Briggs & Vander Wall, 2004), and altering the species composition and relative abundance of available seeds (He et al, 2019;Scott et al, 2010), and markedly shaping vegetation structure (Camargo, Barrio, et al, 2018;Culhane et al, 2022).…”

“…These fire-induced changes in vegetation alter the availability of key resources to small mammals (Culhane et al, 2022), such as potentially protective herbaceous layer (Camargo, Sano, & Vieira, 2018), nesting sites (Innes et al, 2007;Vieira et al, 2005), and understory density (Chia et al, 2016;González et al, 2021), which ultimately also affects interactions between these animals and seeds.…”

“…Small mammal seed dispersal, however, can be influenced by several biotic and abiotic factors, including inter‐ and intraspecific interactions, climate, and fire (Godó et al., 2022). This disturbance may affect seed‐small mammal interactions in several ways, including reducing the effectiveness of seed detection by the animals (Briggs & Vander Wall, 2004), and altering the species composition and relative abundance of available seeds (He et al., 2019; Scott et al., 2010), and markedly shaping vegetation structure (Camargo, Barrio, et al., 2018; Culhane et al., 2022). These fire‐induced changes in vegetation alter the availability of key resources to small mammals (Culhane et al., 2022), such as potentially protective herbaceous layer (Camargo, Sano, & Vieira, 2018), nesting sites (Innes et al., 2007; Vieira et al., 2005), and understory density (Chia et al., 2016; González et al., 2021), which ultimately also affects interactions between these animals and seeds.…”

How do invasive predators and their native prey respond to prescribed fire?

“…Consequently, these species may suffer reduced fitness shortly after fire. For instance, the Trowbridge's shrew ( Sorex trowbridgii ) in North America, declined after fire in response to a loss of food or an increased predation risk (Culhane et al., 2022 ; Greenberg et al., 2007 ). Conversely, the abundance of larger herbivores, such as the red‐flanked duiker ( Cephalophus rufilatus ) and zebra ( Equus quagga ) in Africa, can increase in recently burnt areas, as the regenerating vegetation is typically more palatable and the risk of predation by ambush predators, such as lions ( Panthera leo ), is lower (Funston et al., 2001 ; Klop et al., 2007 ; Reid et al., 2023 ).…”

After the ‘Black Summer’ fires: Faunal responses to megafire depend on fire severity, proportional area burnt and vegetation type

“…In addition to fire characteristics, vegetation can influence how disturbance impacts a landscape and how species respond to disturbance. Different species rely on specific vegetation types for food and shelter (Culhane et al., 2022), but vegetation itself can influence the immediate and ongoing impact of fire due to its differing characteristics (Clarke et al., 2014). For instance, during fire, some vegetation types may exhibit pyrogenic traits (e.g.…”