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    Assessing the sensitivity of biodiversity indices used to inform fire management
    Giljohann, KM ; Kelly, LT ; Connell, J ; Clarke, MF ; Clarke, RH ; Regan, TJ ; McCarthy, MA ; Blanchard, J (WILEY, 2018-03)
    Biodiversity indices are widely used to summarize changes in the distribution and abundance of multiple species and measure progress towards management targets. However, the sensitivity of biodiversity indices to the data, landscape classification and conservation values underpinning them are rarely interrogated. There are limited studies to help scientists and land managers use biodiversity indices in the presence of fire and vegetation succession. The geometric mean of species' relative abundance or occurrence (G) is a biodiversity index that can be used to determine the mix of post‐fire vegetation that maximizes biodiversity. We explored the sensitivity of G to (1) type of biodiversity data, (2) representation of ecosystem states, (3) expression of conservation values, and (4) uncertainty in species' response to landscape structure. Our case study is an area of fire‐prone woodland in southern Australia where G is used in fire management planning. We analysed three datasets to determine the fire responses of 170 bird, mammal and reptile species. G and fire management targets were sensitive to the species included in the analysis. The optimal mix of vegetation successional states for threatened birds was more narrowly defined than the optimal mix for all species combined. G was less sensitive to successional classification (i.e. number of states); although classifications of increasing complexity provided additional insights into desirable levels of heterogeneity. Weighting species by conservation status or endemism influenced the mix of vegetation states that maximized biodiversity. When a higher value was placed on threatened species the importance of late successional vegetation was emphasized. Representing variation in individual species' response to vegetation structure made it clearer when a decrease in G was likely to reflect a significant reduction in species occurrences. Synthesis and applications. Data, models and conservation values can be combined using biodiversity indices to make robust environmental decisions. Combining different types of biodiversity data using composite indices, such as the geometric mean, can improve the coverage and relevance of biodiversity indices. We recommend that evaluation of biodiversity indices for fire management verify how index assumptions align with management objectives, consider the relative merits of different types of biodiversity data, test sensitivity of ecosystem state definitions and incorporate conservation values through species weightings.
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    Putting pyrodiversity to work for animal conservation
    Kelly, LT ; Brotons, L ; McCarthy, MA (WILEY, 2017-08)
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    Does pyrodiversity beget alpha, beta or gamma diversity? A case study using reptiles from semi-arid Australia
    Farnsworth, LM ; Nimmo, DG ; Kelly, LT ; Bennett, AF ; Clarke, MF ; Andersen, A (WILEY-BLACKWELL, 2014-06)
    Abstract Aim A common assumption in fire ecology and management is that landscapes with a greater diversity of fire‐ages will support a greater diversity of animal species (i.e. ‘pyrodiversity begets biodiversity’). This assumption is based on the idea that landscapes with a more diverse fire history provide a greater array of post‐fire habitats, leading to a greater number of species within the landscape. We assessed the hypothesis that pyrodiversity begets biodiversity by enhancing community differentiation (β diversity), resulting in increased landscape‐scale richness (γ‐diversity). We used reptiles as a case‐study. Location The Mallee region of south‐eastern Australia. Methods We used a study design in which ‘whole’ fire mosaics (12.6 km2) were the unit of replication. Study landscapes (n = 28) were selected to represent a gradient in the diversity and extent of fire‐age classes. We surveyed reptiles by using pitfall traps at 10 sites within each landscape (280 sites in total). Reptile data were used to characterize reptile assemblages at the landscape‐scale in three ways: alpha (average within‐site diversity), beta (between‐site diversity) and gamma diversity (total diversity). Results The diversity of fire‐age classes had little influence on the alpha, beta or gamma diversity of reptile assemblages. The properties of fire mosaics that most influenced assemblages were the extent of structurally important fire‐age classes. The extent of long‐unburned vegetation increased beta diversity but reduced alpha diversity of the total reptile assemblage, essentially cancelling each other out at the landscape scale. Main conclusions This study highlights the importance of considering multiple measures of diversity when exploring the influence of landscape properties on biodiversity, as ‘null’ results at the landscape scale (gamma diversity) can result from contrasting patterns in alpha and beta diversity. Using fire to create habitat mosaics, at the scale of this study, is unlikely to enhance the status of reptiles in the region.
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    Do multiple fires interact to affect vegetation structure in temperate eucalypt forests?
    Haslem, A ; Leonard, SWJ ; Bruce, MJ ; Christie, F ; Holland, GJ ; Kelly, LT ; MacHunter, J ; Bennett, AF ; Clarke, MF ; York, A (WILEY, 2016-12)
    Fire plays an important role in structuring vegetation in fire-prone regions worldwide. Progress has been made towards documenting the effects of individual fire events and fire regimes on vegetation structure; less is known of how different fire history attributes (e.g., time since fire, fire frequency) interact to affect vegetation. Using the temperate eucalypt foothill forests of southeastern Australia as a case study system, we examine two hypotheses about such interactions: (1) post-fire vegetation succession (e.g., time-since-fire effects) is influenced by other fire regime attributes and (2) the severity of the most recent fire overrides the effect of preceding fires on vegetation structure. Empirical data on vegetation structure were collected from 540 sites distributed across central and eastern Victoria, Australia. Linear mixed models were used to examine these hypotheses and determine the relative influence of fire and environmental attributes on vegetation structure. Fire history measures, particularly time since fire, affected several vegetation attributes including ground and canopy strata; others such as low and sub-canopy vegetation were more strongly influenced by environmental characteristics like rainfall. There was little support for the hypothesis that post-fire succession is influenced by fire history attributes other than time since fire; only canopy regeneration was influenced by another variable (fire type, representing severity). Our capacity to detect an overriding effect of the severity of the most recent fire was limited by a consistently weak effect of preceding fires on vegetation structure. Overall, results suggest the primary way that fire affects vegetation structure in foothill forests is via attributes of the most recent fire, both its severity and time since its occurrence; other attributes of fire regimes (e.g., fire interval, frequency) have less influence. The strong effect of environmental drivers, such as rainfall and topography, on many structural features show that foothill forest vegetation is also influenced by factors outside human control. While fire is amenable to human management, results suggest that at broad scales, structural attributes of these forests are relatively resilient to the effects of current fire regimes. Nonetheless, the potential for more frequent severe fires at short intervals, associated with a changing climate and/or fire management, warrant further consideration.
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    ECOLOGY Using fire to promote biodiversity
    Kelly, LT ; Brotons, L (AMER ASSOC ADVANCEMENT SCIENCE, 2017-03-24)
    Biodiversity can benefit from fires tailored to suit particular ecosystems and species
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    Optimal fire histories for biodiversity conservation
    Kelly, LT ; Bennett, AF ; Clarke, MF ; McCarthy, MA (WILEY, 2015-04)
    Fire is used as a management tool for biodiversity conservation worldwide. A common objective is to avoid population extinctions due to inappropriate fire regimes. However, in many ecosystems, it is unclear what mix of fire histories will achieve this goal. We determined the optimal fire history of a given area for biological conservation with a method that links tools from 3 fields of research: species distribution modeling, composite indices of biodiversity, and decision science. We based our case study on extensive field surveys of birds, reptiles, and mammals in fire-prone semi-arid Australia. First, we developed statistical models of species' responses to fire history. Second, we determined the optimal allocation of successional states in a given area, based on the geometric mean of species relative abundance. Finally, we showed how conservation targets based on this index can be incorporated into a decision-making framework for fire management. Pyrodiversity per se did not necessarily promote vertebrate biodiversity. Maximizing pyrodiversity by having an even allocation of successional states did not maximize the geometric mean abundance of bird species. Older vegetation was disproportionately important for the conservation of birds, reptiles, and small mammals. Because our method defines fire management objectives based on the habitat requirements of multiple species in the community, it could be used widely to maximize biodiversity in fire-prone ecosystems.
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    A systematic review reveals changes in where and how we have studied habitat loss and fragmentation over 20 years
    Fardila, D ; Kelly, LT ; Moore, JL ; McCarthy, MA (ELSEVIER SCI LTD, 2017-08)
    Habitat loss and fragmentation are global threats to biodiversity and major research topics in ecology and conservation biology. We conducted a systematic review to assess where – the geographic locations and habitat types - and how – the study designs, conceptual underpinnings, landscape metrics and biodiversity measures - scientists have studied fragmentation over the last two decades. We sampled papers from 1994 to 2016 and used regression modelling to explore changes in fragmentation research over time. Habitat loss and fragmentation studies are geographically and taxonomically biased. Almost 85% of studies were conducted in America and Europe, with temperate forests and birds the most studied groups. Most studies use a binary conceptual model of landscapes (habitat versus non-habitat) and static measures of biodiversity. However, research on fragmentation is slowly shifting from a focus on coarse patterns to more nuanced representations of biodiversity and landscapes that better represent ecological processes. For example, empirical research based on gradient or continuum models, that offer new insights into landscape complexity and species-specific responses to habitat fragmentation, are increasing in prevalence. We recommend that fragmentation research focuses on developing knowledge on underlying mechanisms and processes of how species respond to landscape changes, and that fragmentation studies be conducted in the full range of habitats currently experiencing high rates of landscape modification. This is crucial if we are to understand relationships between biodiversity and ecosystems and to develop effective management strategies in fragmented landscapes.
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    Interactions between rainfall, fire and herbivory drive resprouter vital rates in a semi-arid ecosystem
    Giljohann, KM ; McCarthy, MA ; Keith, DA ; Kelly, LT ; Tozer, MG ; Regan, TJ ; Salguero‐Gómez, R (WILEY, 2017-11)
    Summary Global change is threatening ecosystems and biodiversity world‐wide, creating a pressing need to understand how climate and disturbance regimes interact and influence the persistence of species. We quantify how three ecosystem drivers – rainfall, fire and herbivory – influence vital rates in the perennial resprouting graminoid, Triodia scariosa, a foundation species of semi‐arid Australia. We used an 11‐year dataset from a fire and herbivore exclosure experiment, to model flowering, post‐fire recruitment and the post‐fire survival of seedlings and resprouting plants. Regression modelling quantified the effect of rainfall, inter‐fire interval, fire type (wildfire or prescribed fire), grazing by herbivores (native and feral) and an interaction between fire type and herbivory on T. scariosa populations. Rainfall, fire and herbivory had significant effects on post‐fire recruitment and the survival of seedlings and resprouting plants, including strong interactions between these drivers. Herbivory following wildfire had a minor effect, but in years of below‐average rainfall herbivory following prescribed fire had a large effect, reducing the survival of seedlings and resprouting plants by 20% and over 50% respectively, relative to post‐fire survival under average rainfall conditions. Variation in rainfall underpinned significant variation in post‐fire resprouting and seedling survival, thus we postulate rainfall primarily drives the dynamics of T. scariosa populations. Synthesis. This study highlights the importance of modelling interactions between key ecosystem drivers when predicting how changes in global climate and disturbance regimes influence plant vital rates. Relatively small changes to disturbance regimes can substantially alter population processes, even in perennial resprouting species. This work suggests that conservation of foundation species, such as T. scariosa, will benefit if fire management decisions are better integrated with inter‐annual weather forecasts and herbivore management.