Burning in Banksia Woodlands: How Does the Fire-Free Period Influence Reptile Communities?

Fire is an important management tool for both hazard reduction burning and maintenance of biodiversity. The impact of time since last fire on fauna is an important factor to understand as land managers often aim for prescribed burning regimes with specific fire-free intervals. However, our current understanding of the impact of time since last fire on fauna is largely unknown and likely dependent on vegetation type. We examined the responses of reptiles to fire age in banksia woodlands, and the interspersed melaleuca damplands among them, north of Perth, Western Australia, where the current prescribed burning regime is targeting a fire-free period of 8–12 years. The response of reptiles to fire was dependent on vegetation type. Reptiles were generally more abundant (e.g. Lerista elegans and Ctenophorus adelaidensis) and specious in banksia sites. Several species (e.g. Menetia greyii, Cryptoblepharus buchananii) preferred long unburnt melaleuca sites (>16 years since last fire, YSLF) compared to recently burnt sites (<12 YSLF). Several of the small elapids (e.g. the WA priority listed species Neelaps calonotus) were only detected in older-aged banksia sites (>16 YSLF). The terrestrial dragon C. adelaidensis and the skink Morethia obscura displayed a strong response to fire in banksia woodlands only. Highest abundances of the dragon were detected in the recently burnt (<7 YSLF) and long unburnt (>35 YSLF) banksia woodlands, while the skink was more abundant in older sites. Habitats from a range of fire ages are required to support the reptiles we detected, especially the longer unburnt (>16 YSLF) melaleuca habitat. Current burning prescriptions are reducing the availability of these older habitats

GAM relationships for reptile abundance and and the abundance of <i>C. buchanni</i> with time since last fire, reptile species number, and the abundance of <i>M. obscura</i> and <i>M. greyii</i> with vegetation cover, and <i>M. greyii</i> with sqrt-transformed litter depth.

<p>Adjusted r² values are plotted for all relationships. Values for the abundance of reptiles and species number are rescaled values based on the standardised sqrt-transformed abundance/species number per 10 trap nights.</p

ANOVA F-values for reptile abundance, species richness, diversity and evenness, and individual species abundances showing responses to vegetation type, fire age and the interaction of vegetation type and fire age.

<p>Significant values are in bold (* <i>P</i><0.5, ** <i>P</i><0.01). Letters beside significant values indicate results from post-hoc Tukey HSD tests for vegetation type (B = banksia, M = melaleuca) and fire age category (O = old, >16 YSLF; Y = young, <11 YSLF).</p

ANOVA F-values for plant taxa number, microhabitat variables and vertical vegetation density showing responses to vegetation type, fire age and the interaction of vegetation type and fire age.

<p>Significant values are indicated (* <i>P</i><0.5, ** <i>P</i><0.01) and values approaching significance are identified (∧ 0.06><i>P</i>≥0.05). Letters beside significant values indicate results from post-hoc Tukey HSD tests for vegetation type (B = banksia, M = melaleuca) and fire age category (O = old, >16 YSLF; Y = young, <11 YSLF).</p

GAM relationships for the abundance of <i>C. adelaidensis</i> with time since last fire and bareground cover, and <i>M. obscura</i> with time since last fire in banksia woodlands.

<p>Adjusted r² values are plotted for all relationships. Values for the abundance of reptiles are the rescaled values based on the standardised sqrt-transformed abundance per 10 trap nights.</p

Significant differences in reptile species number and reptile abundances for habitat and fire age categories.

<p>Mean (per 10 trap nights ±95%CI) a) reptile species number b) reptile abundance and c) – e) selected individual species abundances between banksia and melaleuca habitats and f) abundance of <i>Menetia greyii</i> in old and young fire age categories.</p

NMDS ordination (Sorensen distance measure) on the assemblage of reptiles.

<p>a) NMDS ordination of 21 reptile species at 30 sites of differing habitat (melaleuca vs banksia) and fire age (old versus young). The ordination is in two dimensions (stress = 0.193), with axis 1 and 2 cumulatively representing 75% variance (r² = 0.441 and 0.310 respectively). b) Correlations of species and habitat variables (r²>0.2) with NMDS ordination.</p

Top-ranking generalised additive models (GAM) for reptile response variables with time since last fire (YSLF) and microhabitat variables within each vegetation type.

<p>Only the models with a ΔAICc<2 and an adjusted r²>0.10 are shown. Variables detected for each model are indicated with an ‘X’. Microhabitat variables include: YSLF = years since last fire, Veg = vegetation cover and Bare = bareground cover.</p

GAM relationships between time since last fire and five microhabitat variables within each vegetation type.

<p>Adjusted r² values are plotted for all relationships. Values for microhabitat variables have been rescaled.</p

Fauna survey sites in the remnant vegetation extent surrounding Perth, Western Australia.

<p>Fauna survey sites in the remnant vegetation extent surrounding Perth, Western Australia.</p