Lindenmayer, D., Blanchard, W., MacGregor, C., Barton, P., Banks, S.C., Crane, M., Michael, D., Okada, S., Berry, L.E. and Gill, M., 2015, Temporal trends in mammal responses to fire reveals the complex effects of fire regime attributes. Ecological Applications, In Press.
Aims: To identify which attributes of fire regimes affect temporal change in the presence and abundance of native mammals
Study area: Booderee National Park, south-eastern Australia
Methods: Our study was underpinned by time series data on 11 mammal species at 97 long-term sites between 2003 and 2013. We employed AIC-based selection of hurdle models to explore how temporal aspects of fire regimes influenced both the presence and the conditional abundance of a species at a site. The three key fire regime components examined were: (i) severity of a major fire in 2003, (ii) the interval between the 2003 fire and the previous fire, and, (iii) number of past fires – a reflection of the fire history at a site. The unique nature of our long term dataset enabled us to quantify the interactions between survey year and each of these three fire regime variables, an important aspect of ecological relationships missing from temporally-restricted studies.
Key findings: We found that multiple aspects of fire regimes influenced temporal variation in the presence and abundance of mammals. The best models indicated that 6 of the 11 species responded to two or more fire regime variables, with terrestrial rodents and the Long-nosed Bandicoot influenced by all three fire regime attributes. Almost all species responded to time since fire, either as an interaction with survey year or as a main effect. Fire severity or its interaction with survey year was important for most terrestrial rodents, the Long-nosed Bandicoot, and Common Ringtail Possum. Further complexity emerged through differences in the presence/absence versus the conditional abundance components of the hurdle models we constructed for each mammal species. The number of fires at a site was significant for species of terrestrial rodent (but not the eastern Chestnut Mouse), the Long-nosed Bandicoot, Common Ringtail Possum, and the Eastern Grey Kangaroo. Our findings contain evidence of the effects on native mammals of heterogeneity in fire regimes. They also strongly suggest that the invisible mosaic (sensu (Bradstock et al. 2005)) will have a large influence on the response of species to the next fire at a given site.
Implications: Temporal response patterns of mammal species were influenced by multiple fire regime attributes, and often in conjunction with survey year. This underscores the critical importance of long-term studies of biota that are coupled with datasets characterized by carefully documented fire history, severity and frequency. Long-term studies are essential to predict animal responses to future fires and guide future management such as when and where more (prescribed) fires are needed or, conversely, where and when long unburned vegetation is required. The complexity of observed responses highlights the need for large reserves in which patterns of heterogeneity in fire regimes can be sustained in both space and over time. Conservation managers also need to be cognisant of the effects on biota of some variables that are indirectly related or unrelated to fire.