Burning for biodiversity: highly resilient ant communities respond only to strongly contrasting fire regimes in Australia's seasonal tropics

Abstract

Summary1. According to the pyrodiversity paradigm, a wide range of fire regimes is required to maintain biodiversity in fire-prone landscapes. However, the requisite level of pyrodiversity has seldom been tested and may actually be very low. 2. Here, we examine the sensitivity of tropical savanna ants to variation in fire regimes using results from a long-term fire experiment near Darwin, Australia. Six experimental fire regimes, with varying fire frequency and seasonality, have been applied to 18 one-ha plots in three replicated blocks since 2004, with ants sampled prior to experimental burning and then annually after up to 2009. Our primary focus is on the extent to which different patterns of ant richness and composition are associated with each of the six treatment regimes, or whether there is such high overlap that differences only become apparent when experimental treatments are grouped to provide strongly contrasting fire regimes. 3. When treating each of the six fire treatments separately, we were unable to detect a significant influence of fire on any ant community response variable. We were only able to detect significant ant responses when we grouped the experimental treatments into two contrasting fire frequency classes, low (burnt at most once over the 5 years) vs. high (burnt every 1 or 2 years). Even then, these responses were only evident after 3 years of fire treatment. 4. Our findings demonstrate that ant communities have very high resilience in relation to fire, with differences evident only between strongly contrasting regimes. Such resilience appears to be characteristic of savanna ants throughout the world. 5. Synthesis and applications. A large range of finely tuned fire regimes is unlikely to promote regional ant diversity. Rather, only very limited pyrodiversity (a combination of frequently and infrequently burnt areas) would appear to be sufficient for maintaining diversity at a landscape scale. It is important that fire management for biodiversity conservation focuses on the demonstrated requirements of target species, rather than be based on an assumption that 'pyrodiversity begets biodiversity'.

An experimental test of whether pyrodiversity promotes mammal diversity in a northern Australian savanna

“…Compared with invertebrates, there has been limited research relating savanna mammal diversity to pyrodiversity (Briani, Palma, Vieira, & Henriques, ; Griffiths, Garnett, & Brook, ). While our results concur with those of Maravalhas and Vasconcelos (), who demonstrated the importance of pyrodiversity for ant diversity in Brazilian cerrado (savanna), they contrast with research of Australian and African savanna invertebrates, which exhibited a high level of resilience to fire (Andersen et al., ; Parr, Robertson, Biggs, & Chown, ). Again, while our results concur with some studies linking pyrodiversity to the diversity of faunal groups in biomes other than savanna (Ponisio et al., ; Tingley et al., ), they contrast with others (Farnsworth et al., ; Taylor et al., ).…”

Temporal Turnover of Species Maintains Ant Diversity but Transforms Species Assemblage Recovering from Fire Disturbance

“…Parr et al (2004) and Andersen et al (2014), suggest that little intense fire does not have effect on ground ant fauna, and our results indicate that the ant fauna in rupestrian complex vegetation are highly resistant and resilient to fire disturbance. Nevertheless, we observed species turnover over time, common in both areas but possibly due to different causes.…”

Fauna and vegetation responses to fire and invasion by toxic cane toads (Rhinella marina) in an obligate seeder-dominated tropical savanna in the Kimberley, northern Australia

“…Savanna faunas both in Australia (Andersen and Muller 2000;Corbett et al 2003;Andersen et al 2005Andersen et al , 2010Andersen et al , 2014aAndersen et al , 2014bRadford 2012;Radford and Andersen 2012) and elsewhere worldwide (Gillon 1983;Parr and Chown 2003;Parr et al 2004) are often thought to be relatively fire resilient, consistent with fire being intrinsic to this biome (Bond et al 2005). Despite this, some savanna groups are more fire-sensitive than others, for instance, small mammals (Andersen et al 2005;Woinarski et al 2010Woinarski et al , 2011 and granivorous finches in northern Australia (Woinarski and Legge 2013).…”

“…A long-term absence of fire in savannas is known to result in radical assemblage responses among some fauna (e.g. forest-specialist ants; Woinarski et al 2004;Andersen et al 2012Andersen et al , 2014b. However, the only known data that detail fauna assemblages from long-unburnt (>40 years) pindan woodland (C. Palmer, unpubl.…”

“…In contrast, larger fauna such as mammals may be severely affected by the same fire regime (Andersen et al 2005Legge et al 2008). Differences in recovery rates and post-fire seral stages may be important for conservation management because particular species or groups may respond only to a subset of post-fire serial stages or habitat attributes (Andersen et al , 2014bRadford et al 2015).…”