School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemHabitat use at fire edges: Does animal activity follow temporal patterns of habitat change?(Elsevier, 2019-11-01)Edges are ecologically important environmental features that have been well researched in agricultural and urban landscapes. However, little work has been conducted in flammable ecosystems where spatially and temporally dynamic fire edges are expected to influence animal activity patterns, particularly for animals reliant on vegetation for cover, foraging or nesting. We quantified the response of ground-dwelling mammals to fire edges and sought to determine whether animal activity mirrored temporal changes in regenerating understorey vegetation. We used a space-for-time substitution sampling design and selected a series of 26 treatment sites burnt by prescribed fire, where time since fire ranged from 0 to 7 years. Ten long-unburnt sites acted as controls. At each treatment site we identified a burnt/unburnt edge and used camera traps and Elliott traps to survey ground-dwelling mammals on either side. Habitat structure was measured at all 36 sites. We used general and generalised linear mixed models to determine the response of both habitat and animals to time since fire on both burnt and unburnt sides of edges. In addition, we used a resource selection index to assess the congruence between changes in understorey complexity and animal activity identified in the first set of analyses. On the unburnt side of the edge understorey complexity remained constant over time. On the burnt side understorey complexity followed a hump-shaped trend, peaking at 3 years post-fire where it exceeded the level of complexity on the unburnt edge. Larger animals with general resource requirements were more active at burnt compared to unburnt edges immediately after fire, but similarly active on both sides of fire edges from three years post-fire. Despite some activity on the burnt side of edges immediately after fire, small mammals were generally less active on burnt edges compared to unburnt edges for up to three years. Native species’ activity did not follow patterns of temporal change in structurally complex understorey vegetation. For all species, selection was strongest at recently burnt edges with little vegetation and substantially lower at 3–7 year old regenerating edges where understorey complexity was higher. In general, patterns of selection on the unburnt side of edges were similar over time. Our findings suggest that vegetation change on the burnt side of fire edges may not be a good predictor of native mammal use. Foxes and cats, exotic predators in our system, were also using the burnt edge more than expected immediately after fire. Immediate post-fire predation may be higher at fire edges than elsewhere, and recently burnt edge zones could be suitable locations for integrated predator and fire management.
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ItemSurvey design for precise fire management conservation targets(WILEY, 2018-01)Common goals of ecological fire management are to sustain biodiversity and minimize extinction risk. A novel approach to achieving these goals determines the relative proportions of vegetation growth stages (equivalent to successional stages, which are categorical representations of time since fire) that maximize a biodiversity index. The method combines data describing species abundances in each growth stage with numerical optimization to define an optimal growth-stage structure that provides a conservation-based operational target for managers. However, conservation targets derived from growth-stage optimization are likely to depend critically on choices regarding input data. There is growing interest in the use of growth-stage optimization as a basis for fire management, thus understanding of how input data influence the outputs is crucial. Simulated data sets provide a flexible platform for systematically varying aspects of survey design and species inclusions. We used artificial data with known properties, and a case-study data set from southeastern Australia, to examine the influence of (1) survey design (total number of sites and their distribution among growth stages) and (2) species inclusions (total number of species and their level of specialization) on the precision of conservation targets. Based on our findings, we recommend that survey designs for precise estimates would ideally involve at least 80 sites, and include at least 80 species. Greater numbers of sites and species will yield increasingly reliable results, but fewer might be sufficient in some circumstances. An even distribution of sites among growth stages was less important than the total number of sites, and omission of species is unlikely to have a major influence on results as long as several species specialize on each growth stage. We highlight the importance of examining the responses of individual species to growth stage before feeding survey data into the growth-stage optimization black box, and advocate use of a resampling procedure to determine the precision of results. Collectively, our findings form a reproducible guide to designing ecological surveys that yield precise conservation targets through growth-stage optimization, and ultimately help sustain biodiversity in fire-prone systems.
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ItemContrasting responses of small mammals to fire and topographic refugia(WILEY, 2016-06)Abstract Unburnt patches within burnt landscapes are expected to provide an important resource for fauna, potentially acting as a refuge from direct effects of fire and allowing animals to persist in burnt landscapes. Nevertheless, there is little information about the way refugia are used by fauna and how populations may be affected by them. Planned burns are often patchy, with unburnt areas generally associated with gully systems providing a good opportunity to study faunal use of refugia. We used a before–after control‐impact design associated with a planned burn in south eastern Australia to investigate how two small mammal species, the bush rat Rattus fuscipes and agile antechinus Antechinus agilis, used unburnt gully systems within a larger burnt area. We tested three alternative hypotheses relating to post‐fire abundance: (i) active refugia – abundance would increase in unburnt patches because of a post‐fire shift of individuals from burnt to unburnt areas; (ii) passive refugia – abundance in unburnt patches would remain similar to pre‐fire levels; and (iii) limited or no refugia – abundance would reduce in unburnt patches related to the change induced by fire in the wider landscape. We found the two species responded differently to the presence of unburnt refugia in the landscape. Relative to controls, fire had little effect on bush rat abundance in gullies, supporting hypothesis 2. In contrast, agile antechinus abundance increased in gullies immediately post‐fire consistent with a shift of individuals from burnt parts of the landscape, supporting hypothesis 1. Differences in site fidelity, habitat use and intraspecific competition between these species are suggested as likely factors influencing responses to refugia. The way unburnt patches function as faunal refugia and the subsequent influence they have on post‐fire population dynamics, will to some extent depend on the life history attributes of individual species.
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ItemCombining optimization and simulation modelling to measure the cumulative impacts of prescribed fire and wildfire on vegetation species diversity(WILEY, 2019-03)Growth‐stage optimization (GSO) offers a new approach to biodiversity conservation in fire‐prone regions by estimating the optimal distribution of vegetation growth stages that maximize a species diversity index. This optimal growth‐stage structure provides managers an operational goal explicitly linked to a positive conservation outcome but does not define the fire regime needed to achieve it. We paired GSO with LANDIS II, a landscape succession and disturbance simulation model, to (a) estimate the optimal growth‐stage structure that maximized vegetation diversity in a south‐east Australian heathy woodland, (b) define the fire regime needed to achieve it, and (c) determine the cumulative effects of different fire‐regime scenarios on vegetation diversity over a 60‐year period. Scenarios included 0%, 2%, 5%, and 10% of the landscape burnt per year by prescribed fire only, or in combination with three alternative wildfire regimes. Furthermore, we investigated the differences in the optimal growth‐stage structure relating to above‐ground, soil seedbank, and total (above and soil seedbank) diversity datasets. The growth‐stage structure that maximized total vegetation diversity comprised approximately even proportions of all stages. In contrast, separately analysed above‐ground and soil seedbank data resulted in a greater proportion of younger and older growth‐stages, respectively. Scenarios including 5% prescribed burning per year (with and without wildfire) resulted in diversity values within 1.5% of the theoretical maximum value. Scenarios including 2% and 10% prescribed fire resulted in diversity values 8%–12% and 1.5%–5% lower than the maximum, respectively. Scenarios without prescribed fire caused diversity to fall 30%–70%. Trends across the 60 years showed that wildfire depressed diversity and subsequent prescribed fire drove recovery within 15 years. The largest threat to vegetation diversity was the absence of fire. Synthesis and applications. Combining growth‐stage optimization and simulation modelling is a powerful way of defining a conservation‐based fire management goal and identifying the prescribed fire regime needed to achieve it. We demonstrated that vegetation diversity in heathy woodland was increased by prescribed fire, with and without the cumulative effect of wildfire, and declined sharply when fire was excluded. Our method provides a flexible platform for developing long‐term fire management strategies that seek to balance human safety and biodiversity conservation. Including both plants and animals in GSO will help land managers meet the needs of multiple taxa.
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ItemDetecting mammals in heterogeneous landscapes: implications for biodiversity monitoring and management(SPRINGER, 2014-02)With terrestrial mammals facing worldwide declines there is an increasing need to effectively monitor populations so that appropriate conservation actions can be taken. There are many techniques available to survey terrestrial mammals and in recent years there have been a number of studies comparing the effectiveness of different methods. Most of these studies have not considered complementarity (the degree to which techniques detect unique species) and effectiveness across ecological gradients. In this study we examined three widely used techniques, camera trapping, live trapping and hair detection, for their complementarity across a vegetation and disturbance gradient. Overall, camera trapping detected more species than any other single technique, but live trapping complemented the cameras by consistently detecting unique species. Additionally, technique effectiveness differed between vegetation types; cameras alone were most effective in dry forest systems while cameras combined with live traps were most effective in wetter forest systems. These results suggest that care needs to be taken when sampling across heterogeneous landscapes because relying on one technique alone could result in certain taxa being systematically overlooked, leading to potentially erroneous conclusions.
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ItemEdge effects in fire-prone landscapes: Ecological importance and implications for fauna(WILEY, 2018-06)Edges are ecologically important environmental features and have been well researched in agricultural and urban landscapes. However, little work has been conducted in flammable ecosystems where spatially and temporally dynamic fire edges are expected to influence important processes such as recolonization of burnt areas and landscape connectivity. We review the literature on fire, fauna, and edge effects to summarize current knowledge of faunal responses to fire edges and identify knowledge gaps. We then develop a conceptual model to predict faunal responses to fire edges and present an agenda for future research. Faunal abundance at fire edges changes over time, but patterns depend on species traits and resource availability. Responses are also influenced by edge architecture (e.g., size and shape), site and landscape context, and spatial scale. However, data are limited and the influence of fire edges on both local abundance and regional distributions of fauna is largely unknown. In our conceptual model, biophysical properties interact with the fire regime (e.g., patchiness, frequency) to influence edge architecture. Edge architecture and species traits influence edge permeability, which is linked to important processes such as movement, resource selection, and species interactions. Predicting the effect of fire edges on fauna is challenging, but important for biodiversity conservation in flammable landscapes. Our conceptual model combines several drivers of faunal fire responses (biophysical properties, regime attributes, species traits) and will therefore lead to improved predictions. Future research is needed to understand fire as an agent of edge creation; the spatio-temporal flux of fire edges across landscapes; and the effect of fire edges on faunal movement, resource selection, and biotic interactions. To aid the incorporation of new data into our predictive framework, our model has been designed as a Bayesian Network, a statistical tool capable of analyzing complex environmental relationships, dealing with data gaps, and generating testable hypotheses.
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ItemOpposing Responses of Bird Functional Diversity to Vegetation Structural Diversity in Wet and Dry Forest(PUBLIC LIBRARY SCIENCE, 2016-10-14)Disturbance regimes are changing worldwide, and the consequences for ecosystem function and resilience are largely unknown. Functional diversity (FD) provides a surrogate measure of ecosystem function by capturing the range, abundance and distribution of trait values in a community. Enhanced understanding of the responses of FD to measures of vegetation structure at landscape scales is needed to guide conservation management. To address this knowledge gap, we used a whole-of-landscape sampling approach to examine relationships between bird FD, vegetation diversity and time since fire. We surveyed birds and measured vegetation at 36 landscape sampling units in dry and wet forest in southeast Australia during 2010 and 2011. Four uncorrelated indices of bird FD (richness, evenness, divergence and dispersion) were derived from six bird traits, and we investigated responses of these indices and species richness to both vertical and horizontal vegetation diversity using linear mixed models. We also considered the extent to which the mean and diversity of time since fire were related to vegetation diversity. Results showed opposing responses of FD to vegetation diversity in dry and wet forest. In dry forest, where fire is frequent, species richness and two FD indices (richness and dispersion) were positively related to vertical vegetation diversity, consistent with theory relating to environmental variation and coexistence. However, in wet forest subject to infrequent fire, the same three response variables were negatively associated with vertical diversity. We suggest that competitive dominance by species results in lower FD as vegetation diversity increases in wet forest. The responses of functional evenness were opposite to those of species richness, functional richness and dispersion in both forest types, highlighting the value of examining multiple FD metrics at management-relevant scales. The mean and diversity of time since fire were uncorrelated with vegetation diversity in wet forest, but positively correlated with vegetation diversity in dry forest. We therefore suggest that protection of older vegetation is important, but controlled application of low-severity fire in dry forest may sustain ecosystem function by enhancing different elements of FD.
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ItemHuman-modified habitats facilitate forest-dwelling populations of an invasive predator, Vulpes vulpes(NATURE PORTFOLIO, 2017-09-25)Invasive and over-abundant predators pose a major threat to biodiversity and often benefit from human activities. Effective management requires understanding predator use of human-modified habitats (including resource subsidies and disturbed environments), and individual variation within populations. We investigated selection for human-modified habitats by invasive red foxes, Vulpes vulpes, within two predominantly forested Australian landscapes. We predicted that foxes would select for human-modified habitats in their range locations and fine-scale movements, but that selection would vary between individuals. We GPS-tracked 19 foxes for 17-166 days; ranges covered 33 to >2500 ha. Approximately half the foxes selected for human-modified habitats at the range scale, with some 'commuting' more than five kilometres to farmland or townships at night. Two foxes used burnt forest intensively after a prescribed fire. In their fine-scale nocturnal movements, most foxes selected for human-modified habitats such as reservoirs, forest edges and roads, but there was considerable individual variation. Native fauna in fragmented and disturbed habitats are likely to be exposed to high rates of fox predation, and anthropogenic food resources may subsidise fox populations within the forest interior. Coordinating fox control across land-tenures, targeting specific landscape features, and limiting fox access to anthropogenic resources will be important for biodiversity conservation.
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ItemFire regimes and environmental gradients shape vertebrate and plant distributions in temperate eucalypt forests(Ecological Society of America, 2017-04-01)Fire is a global driver of ecosystem structure, function, and change. Problems common to fire scientists and managers worldwide include a limited knowledge of how multiple taxonomic groups within a given ecosystem respond to recurrent fires, and how interactions between fire regimes and environmental gradients influence biodiversity. We tested six hypotheses relating to fire regimes and environmental gradients in forest ecosystems using data on birds (493 sites), mammals (175 sites), and vascular plants (615 sites) systematically collected in dry eucalypt forests in southeastern Australia. We addressed each of these hypotheses by fitting species distribution models which differed in the environmental variables used, the spatial extent of the data, or the type of response data. We found (1) as predicted, fire interacted with environmental gradients and shaped species distributions, but there was substantial variation between species; (2) multiple characteristics of fire regimes influenced the distribution of forest species; (3) common to vertebrates and plants was a strong influence of temperature and rainfall gradients, but contrary to predictions, inter‐fire interval was the most influential component of the fire regime on both taxonomic groups; (4) mixed support for the hypothesis that fire would be a stronger influence on species occurrence at a smaller spatial extent; only for vertebrates did scale have an effect in the direction expected; (5) as predicted, vertebrates closely associated with direct measures of habitat structure were those most strongly influenced by fire regimes; and (6) the modeled fire responses for birds were sensitive to the use of either presence–absence or abundance data. These results underscore the important insights that can be gained by modeling how fire regimes, not just fire events, influence biota in forests. Our work highlights the need for management of fire regimes to be complemented by an understanding of the underlying environmental gradients and key elements of habitat structure that influence resource availability for plants and animals. We have demonstrated that there are general patterns in biotic responses to fire regimes and environmental gradients, but landscape management must continue to carefully consider species, scale, and the quality of biodiversity data to achieve biodiversity conservation in fire‐prone forests.
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ItemFoothills Fire and Biota(Department of Environment, Land, Water and Planning, 2016)