Attenuated post-fire fauna succession: the effects of surrounding landscape context on post-fire colonisation of fauna

Abstract

Context After fire, immigration from outside burnt areas is important for the recovery of faunal communities. However, for recovery to occur, the matrix around the fire must support source populations of immigrants. Therefore, the landscape context of fires may be a critical determinant of the species pool available for (re)colonisation, hence post-fire community composition. Increasingly, fires occur in fragmented systems, and there is limited knowledge of how the surrounding landscape interacts with post-fire community recovery. Aim The present study aimed to examine how landscape context influences faunal communities after large wildfires. Methods Three reserves burnt by wildfire were examined ~18 months before the study in the Mallee region of south-eastern Australia. In all cases the burnt area consisted of natural mallee woodland. Two fires occurred within a matrix of extensive natural vegetation, while the third fire burnt >80% of a reserve situated within a highly fragmented, largely agricultural landscape. Birds, reptiles and mammals were surveyed at 90 sites inside and outside the fire boundaries, and relationships of species occurrence to reserve location, burnt versus unburnt status and distance from fire edge were all examined. Key results Post-fire faunal communities reflected the species in the surrounding unburnt landscape. Notably, open habitat specialists, invasive species and species that can persist in small habitat patches were prominent within the fragmented system. Post-fire fauna communities were also influenced by variation of the natural vegetation surrounding the fire. The occurrence of species with low dispersal ability (i.e. reptiles) was influenced by local (patch scale) vegetation structure. 2Conclusions The landscape context of fires is a major driver of the composition of post-fire faunal communities. Our results highlight the potential loss of species sensitive to fragmentation from fire-prone natural vegetation within modified landscapes, and that a reduced pool of potential immigrants leads to ‘attenuated succession’, compromising recovery of the pre-fire community. Implications Post-fire colonists reflect the surrounding landscapes species pool, such that reserves surrounded by fragmented or otherwise low quality habitat are at risk of attenuated succession after fire. Landscape context should be incorporated into conservation planning in fire-prone ecosystems, including consideration of surrounding habitat quality and connectivity and protecting long unburnt vegetation.

A field test of mechanisms underpinning animal diversity in recently burned landscapes

“…Animal community composition pre‐fire—including in areas later burnt or unburnt—also affects patterns of recolonization in post‐fire environments (Simms et al, 2019). It is plausible that some early‐successional species were already absent, or at low abundance, in the area subject to planned fire.…”

“…Within the burnt area, sites 300-500 m from the external perimeter had lower mean reptile species richness than sites only 100 m away. Previous research on several species of diurnal reptiles in mallee vegetation found they were more sensitive to local patch conditions than external connectivity (Simms et al, 2019).…”

“…Habitat connectivity is an aspect of configuration that can be measured by the distance to unburnt patches or other preferred habitats (Simms et al, 2019). Although individual animals often survive a fire event in situ, animals dispersing from adjacent unburnt areas provide an important recolonisation source (Banks et al, 2017; Puig‐Gironès et al, 2018).…”

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

“…Should fire occur, these isolated patches (and even larger ones like Billiat Reserve, Figure 4) are now unlikely to follow the same patterns of plant and animal succession as observed in larger tracts of vegetation due to isolation limiting colonization (Nimmo et al, 2019). Their postfire faunal communities are likely to reflect the species present in surrounding modified environments (Simms et al, 2019), and result in more generalist faunal communities.…”

Resilience of reptiles to megafires

“…Reptiles typically respond to fire with a replacement of species along the post-fire succession process (Hu et al, 2013;Santos & Cheylan, 2013). However, reptiles respond poorly to predictable models of habitat succession as these responses are context dependent (e.g., biogeography, surrounding landscape, climate; Nimmo et al, 2012Nimmo et al, , 2014Simms et al, 2019). Therefore, reptile responses largely depend on the rate of vegetation recovery and the resilience of several ecosystem components (Lindenmayer et al, 2008;Santos et al, 2016).…”