Modeling variability in the fire response of an endangered bird to improve fire‐management

Abstract

Conservation managers regularly burn vegetation to regenerate habitat for fire-dependent species. When determining the time since fire at which to burn, managers model change in a species' occurrence over time, post-fire (fire-response curve) and identify the time since fire associated with decline in occurrence. However, where species exhibit variability in their fire response across space, using a single fire-response curve to determine the timing of burns may lead to burning habitat at an inappropriate time since fire. We tested if elevation, local topography, soil properties, vegetation type or evapotranspiration affect the fire response of the endangered Mallee Emu-wren Stipiturus mallee and its hummock-grass habitat Triodia scariosa in southeastern Australia (n = 217). Previous work on the Mallee Emu-wren found a unimodal fire response with decline in occurrence at~30-50 yr since fire and a time window of occurrence of~30 yr. We found that time since fire and elevation interact to affect the Mallee Emu-wren fire response. At high elevations (55-98 m), Mallee Emuwrens declined in occurrence at~50 yr since fire, with a time window of occurrence of 20-40 yr. However, at low elevations (28-55 m), Mallee Emu-wrens showed no decline in occurrence with increasing time since fire with a time window of occurrence of up to 107 yr. Extent cover of Tall T. scariosa showed similar patterns to the Mallee Emu-wren, indicating that vegetation structure is a likely driver of variability in the Mallee Emu-wren fire response. We speculate that the effect of low elevation is mediated by increased soil nutrient and water availability for key plants. We used our findings to map the appropriate time since fire at which to burn to regenerate habitat for the Mallee Emu-wren across the study region. We recommend no burning for regeneration across one-third of potential habitat, because the Mallee Emu-wren showed no decline in occurrence in these areas. We recommend managers model variability in species' fire responses across space to improve the timing of burns for regeneration.

Post‐fire development of faunal habitat depends on plant regeneration traits

“…Similar patterns to those shown here have been observed previously in temperate eucalypt forests (Swan et al 2015, Haslem et al 2016) and mallee woodlands (Haslem et al 2011). Understorey vegetation provides nesting, foraging and shelter sites for many bird and mammal species typical of these and similar ecosystems (Ford et al 1986, Fox et al 2003, Simonetti et al 2013, Swan et al 2015, Verdon et al 2019. Consequently, the temporal responses of such faunal species to fire are likely to be positively influenced by these post-fire trajectories in habitat suitability (e.g.…”

Fire and Its Interactions With Other Drivers Shape a Distinctive, Semi-Arid ‘Mallee’ Ecosystem

“…The subdued topography of mallee ecosystems and their nutrient-poor soils appear to offer little in the form of permanent drought refuges. Nevertheless, there remains much to learn about how variation in habitat suitability is associated with topography (Selwood et al, 2019;Verdon et al, 2019). Much will depend on a species' ability to move between resources (Nimmo et al, 2019), and whether habitat connectivity enables such movement.…”

Western Bristlebird Dasyornis longirostris: Response to fire and persistence of home range in the Fitzgerald River National Park, Western Australia

“…Our data are broadly consistent with this hypothesis, but also show that the actual time depends on site and context and, for the FRNP, is likely to be at the long end of this spectrum. There could be multiple factors influencing the actual time; for example, Verdon et al (2019) have shown that elevation and time since fire interact to affect fire response in the Mallee Emu-wren Stipiturus mallee. In the case of the Western Bristlebird, the optimal interval is likely to be considerably longer in low-rainfall areas such as around Fitzgerald Track (northern area of the FRNP), and there can be variation within such areas.…”

“…Threatened species that have specific requirements for fire age in their habitat are the ones likely to suffer the most from inappropriate fire regimes, and management is complicated when co-occurring species have stringent but different requirements in relation to fire (Kelly et al 2015;Woinarski et al 2015). Fire management is further complicated where the optimal time since fire for habitat to regenerate varies according to environmental conditions or habitat parameters (Verdon et al 2019). It becomes even more challenging where there have been large changes in land use with consequent habitat loss, and fire regimes (fire extent, intensity, seasonal timing and frequency) are also changing in relation to ongoing climate change, such as in south-western Australia (Abbott & Burrows 2003;Mariani et al 2018).…”