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

Abstract

Planned burning generates different types of pyrodiversity, however, experimental tests of how alternative spatial patterns of burning influence animal communities remain rare. Field tests are needed to understand the mechanisms through which spatial variation in planned fire affects fauna, and how fire can be applied to benefit biodiversity. We tested five hypotheses of how fire‐driven variation in habitat composition and configuration affects fauna at fine scales. Small mammal, reptile and invasive predator activity was monitored at 12 burnt and eight unburnt sites through the year following a large, planned burn in semi‐arid ‘mallee’ woodlands of southern Australia. We explored measures of burnt or unburnt habitat (‘habitat status’); amount of unburnt vegetation (‘habitat amount’); interspersion of burnt and unburnt patches (‘habitat complementation’); distance to external or internal unburnt vegetation (‘habitat connectivity’); and unburnt patch size and local vegetation cover (‘habitat refuge’). Generalized linear models were used to test the influence of each variable on capture rates of three small mammal and 11 reptile species; activity of the introduced red fox (Vulpes vulpes); and species richness of native animals. We found strong support for the habitat status hypothesis and moderate support for four hypotheses relating to spatial patterns of fire. Reptile assemblages varied between burnt and unburnt sites, and relationships were identified between abundance of one or more reptile species and each measure of spatial variation. Reptile species richness was higher at unburnt sites and at sites with more unburnt vegetation in the surrounding area. Sites that were less connected to unburnt vegetation had fewer reptile species. Mammals did not have clear relationships with fine‐scale fire patterns. Synthesis and applications. Application of planned fire to promote biodiversity is globally important. We show that retaining unburnt areas and well‐connected habitat refuges is important for reptile diversity. We also found that several species of small mammals and reptiles appear resilient to the fine‐scale patterns of planned fire experienced in this study, despite activity of introduced predators. The diversity of animals can remain relatively high in areas subject to planned fire, provided that internal and external habitat refuges are retained.

The red fox (Vulpes vulpes) is the dominant predator of lizard models in a semi‐arid landscape, and predation risk is reduced by vegetation cover

“…Retaining patches of unburnt spinifex within the fire boundary could be one way of maintaining reptile species diversity during prescribed burning. In support of this, Senior et al (2023) found three species of reptile and reptile richness was higher in areas near large unburnt refuges following a prescribed fire in the mallee.…”

“…In support of this, Senior et al. (2023) found three species of reptile and reptile richness was higher in areas near large unburnt refuges following a prescribed fire in the mallee.…”

“…Fire regimes that result in large amounts of recently burnt vegetation are likely to heighten predation risk for a variety of spinifex-dependent species by removing the protection from predation that is afforded by spinifex. This predation pressure could be magnified if red foxes and cats are drawn into recently burnt areas, which has recently been demonstrated in the Murray mallee (Senior et al, 2023). Retaining patches of unburnt spinifex within the fire boundary could be one way of maintaining reptile species diversity during prescribed burning.…”

How do invasive predators and their native prey respond to prescribed fire?

“…We predicted that cat and fox activity would be higher in areas burnt by the prescribed fire, however, we found no strong evidence to support this. Although some studies have found strong evidence of cat or fox activity increasing after fire (Birtsas et al., 2012; McGregor, Cliff, & Kanowski, 2016; Miritis et al., 2023), others have found a negative response (Alexandre et al., 2020; Bird et al., 2018; Lothian et al., 2022), no response (Hradsky, Robley, et al., 2017; Moore et al., 2018; Senior et al., 2022), or a context‐dependent response. For instance, in the USA, swift foxes ( V. velox ), which are closely related to red foxes, only used burnt areas more frequently if their existing core home ranges were burnt (Thompson et al., 2008).…”

Ant diversity in relation to time since fire in a mallee landscape of South‐Eastern Australia

“…However, this model will not necessarily apply to vegetation types that have low complexity at maturity, such as many of those occurring in arid and semi‐arid regions. For example, in semi‐arid mallee habitat of south‐eastern Australia patterns of fire age‐classes had little influence on the frequency of occurrence of termite species (Avitabile et al, 2015) or on reptile diversity (Farnsworth et al, 2014), and most mallee reptile and mammal species occur at both burnt and unburnt sites (Senior et al, 2022).…”