Interrelationships between fire, habitat, and mammals in a fragmented heathy woodland

Abstract

Altered fire regimes threaten biodiversity, but there is limited understanding of the mechanisms driving population declines. Relationships between mammal occurrence and time since fire can be unclear because mammals respond directly to changes in habitat structure rather than time since fire per se, and patterns of regeneration can be highly variable. Previous studies have examined how mammals respond to time since fire and habitat structure separately, but rarely considered the three factors together. Furthermore, fires may interact with other threats such as habitat loss and fragmentation, also rarely incorporated into fire studies but known to influence mammal communities. Understanding each of these mechanisms and how they interact is critical for using fire effectively in conservation.We simultaneously related ground-dwelling mammal species activity to habitat structure, habitat structure to post-fire vegetation growth stage, and species activity to growth stage and landscape structure (extent of heathy woodland vegetation) using structural equation models (SEMs). This allowed us to find direct effects of growth stage on mammals, indirect effects mediated by habitat structure, and additional effects of landscape structure.Understorey cover, litter depth, and coarse woody debris responded to growth stage and were important contributors in all SEMs. Four of seven mammal species responded to at least one habitat structure variable. None of the mammal species were related directly to growth stage, but mammals were indirectly related to growth stage through the mediating influence of habitat structure. For example, western grey kangaroos were linked to recently burnt sites, but only through their negative association with litter depth. Extent of heathy woodland vegetation was also an important driver of mammal activity and was related to all but one species; two species showed a positive relationship, and four negative.Important relationships between fire and ground-dwelling mammals may be overlooked unless changes in important habitat resources are also considered. Fire management planning for fauna conservation should incorporate habitat responses as mammal responses to the fire regime may be mediated by fire-driven changes in resources. Knowing how time since fire affects important habitat structures can improve the effectiveness of using fire to manipulate these to support mammal species. Our results will help land managers understand direct and indirect effects of fire in a landscape where multiple drivers threaten biodiversity, and guide the use of prescribed fire to promote aspects of habitat structure that benefit mammals.