Testing hypotheses associated with bird responses to wildfire

Fenner School of Environment and Society, Australian National University, Canberra, ACT 0200, Australia.
Ecological Applications (Impact Factor: 4.09). 01/2009; 18(8):1967-83. DOI: 10.1890/07-1943.1
Source: PubMed


Disturbance is a key ecological process influencing the distribution and abundance of many elements of the earth's biota. Predicting the response of biota to disturbance is therefore important, but it nevertheless remains difficult to make accurate forecasts of response. We tested predictions from disturbance-related theories and concepts in 10 vegetation types at Booderee National Park (southeastern Australia) using a retrospective study of bird responses to fire history (over 35 years) on 110 sites and a prospective study following a single wildfire event in 2003 at 59 of these sites. Our data did not support predictions from the intermediate-disturbance hypothesis; observed bird species richness at a site was significantly (F(1,99) = 6.30, P = 0.014) negatively related to the number of fires since 1972 and was 8.7% lower (95% CI, 1.8-15.1%) for each additional fire. In contrast to fire history effects, we found that after the 2003 fire, the vast majority of individual species and the bird assemblage per se in most vegetation types recovered within two years. Thus, recovery after a single fire did not reflect long-term effects of multiple fires on overall bird species richness at a site. We postulated that the recovery of bird species richness and bird assemblage composition after the 2003 fire would be fastest in structurally simple vegetation types and slowest in structurally complex vegetation, but observed the opposite. Although observed bird species richness in vertically heterogeneous forest and woodland had returned to prefire levels by 2006, bird species richness in structurally simple vegetation types (e.g., sedgeland) had not. Postfire vegetation regeneration, together with a paucity of early-successional specialists, would explain the speed of recovery of the bird assemblage and why it changed relatively little during our investigation.

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    • "burnt landscapes (Letnic & Dickman 2005). For example, the availability of unburnt patches has been linked to the retention of birds and small mammals following large fires in Australia (Lindenmayer et al. 2008; Pereoglou et al. 2011) and South Africa (Yarnell et al. 2008). These studies conclude that species survival after fire is linked to the availability of complex, unburnt, habitat structures within small patches. "
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    ABSTRACT: 1. Mitigating the impacts of large-scale fires on biodiversity is becoming increasingly important as their frequency increases. In response, fire managers have engaged with the concept that retaining small unburnt residual areas of vegetation within extensively burnt landscapes may facilitate biodiversity conservation. However, it remains uncertain how the size and isolation of these unburnt residuals influence faunal distributions, persistence and recovery following fire.2. We used a replicated observation study to test bird responses to the size and isolation of unburnt residuals in a Mallee woodland area recently burnt by a 28,000-ha wildfire in southern Australia. The scale of our study provided a rare opportunity to consider the responses of large mobile organisms to fire-induced habitat fragmentation. Within five replicated spatial blocks, we crossed two levels of isolation with large (5–7ha) and small (1–3ha) unburnt patches and matrix sites burnt five years previously. We compared these site types to six continuous (non-fragmented) unburnt sites. We surveyed each site on eight occasions.3. Most birds occurred more frequently in unburnt habitat beyond the extent of the fire. Bird responses to the availability and spatial distribution of unburnt remnants within the fire were largely influenced by their ability to use the recently burnt matrix. Occurrence of five species was higher in unburnt residuals when more of the landscape within 500 m was burnt.4. A fire refuge effect may be likely for two competitive species that occurred more frequently in unburnt residuals than in the burnt matrix or continuous unburnt habitat. For the weebill, re-colonisation following fire was likely to occur gradually over-time from ex-situ sources.5. Synthesis and applications. To maintain avian diversity in fire-prone landscapes, our results suggest a need to shift management focus from creating networks of small unburnt patches, towards preserving large, intact areas of habitat. However, five species common to the burnt matrix preferentially selected residual patches when unburnt resources were locally scarce. Therefore, to benefit birds, land managers should limit the extent of applied burns and use narrow burns. When planning large burns, practitioners should consider that a number of species will remain absent from the landscape for several decades.This article is protected by copyright. All rights reserved.
    Journal of Applied Ecology 12/2014; 52(2). DOI:10.1111/1365-2664.12387 · 4.56 Impact Factor
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    • "The extensive and intense wildfires that occur in the Southern Hemisphere are increasingly being found to have strongly negative effects on alpha diversity in some areas (Cleary et al., 2004; Green & Sanecki, 2006; Pastro et al., 2011). In other areas, by contrast, wildfires have been found so far to have had few long-term effects on the diversity of flora and fauna (Williams et al., 2008; Lindenmayer et al., 2008b). The prescribed burns grouping was dominated by Australian studies (22 of the 32 Southern Hemisphere studies) and prescribed burns are known to interact in complex ways with other processes on that continent (Driscoll et al., 2010). "
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    ABSTRACT: AimWe conducted a quantitative meta-analysis to investigate the responses of vertebrate diversity to fire, controlling for variables such as fire type, taxon and ecoregion to identify trends across studies and locations.LocationWorld-wide.Methods We calculated indices of the difference in species richness (alpha diversity) and species composition (beta diversity) between burnt and unburnt habitats from studies reporting the species richness and assemblage composition of amphibians, reptiles, birds and mammals. We used a hierarchical approach to investigate the effects of fire on alpha and beta diversity. We tested first for the main effect of fire before investigating the potential influence of fire type (wildfire/prescribed burn), taxon, ecoregion and geographical location (hemisphere/continent).ResultsOne hundred and four studies were evaluated: 56 studies on birds, 26 on mammals, 17 on reptiles and 5 on amphibians. The studies fell into 14 ecoregions, with the three most common being temperate broadleaf and mixed forests, temperate grasslands and savannas and shrublands, and temperate coniferous forest. The effect of fire on species richness and community assemblage composition was strongly influenced by fire type. Prescribed burns significantly increased alpha diversity, whereas wildfires had no overall effect. However, wildfire increased the alpha diversity of temperate coniferous birds in North America. The effects of fire on alpha diversity were stronger in the Northern than the Southern Hemisphere. Turnover in species assemblages (beta diversity) was influenced primarily by fire type. Species assemblages in burnt and unburnt habitats were more similar after prescribed burns and generated lower levels of beta diversity than did wildfires.Main conclusionsThe divergent effects of wildfires and prescribed fires on the alpha and beta diversity of vertebrates and the disparate responses of vertebrate diversity to fires in the Northern and Southern Hemisphere suggest that there is no general response of vertebrate diversity to fire. Our results provide little support for the patch mosaic burn theory or the intermediate disturbance hypothesis to predict post-fire responses of vertebrate diversity.
    06/2014; 23(10). DOI:10.1111/geb.12195
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    • "Bird surveys consisted of two 10 min point interval counts at the 20 and 80 m marks of each transect (Lindenmayer et al., 2008). Individual bird detections were recorded as seen, heard or flying over and assigned to one of four distance classes (0–25 m, 25–50 m, 50–100 m and > 100 m) from the observation point. "
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    ABSTRACT: In many regions, planned burns are implemented to reduce fuel loads and mitigate wildfire risk; increasingly, they are also used to achieve conservation outcomes. However, there is uncertainty regarding how best to apply fire to landscapes in order to enhance biodiversity. The assumption that variable fire regimes are conducive to biodiversity conservation is appealing given its basis in landscape ecological theory, which predicts that spatially complex landscapes sustain greater biodiversity. This supposition is often used as a basis for fire management but has rarely been tested in the context of fire. We sought to test predicted positive relationships between bird diversity and both landscape diversity and configuration in the fire-prone Otway Ranges, southeast Australia, where vegetation transitions from treeless heath to tall open eucalypt forest across a rainfall gradient. We used a whole-of-landscape sampling approach, and mapped fire age classes and vegetation types separately within thirty-six 300 ha landscape sampling units. Bird surveys were undertaken at sub-sampling locations during two successive years, and presence-absence data were used to generate landscape-level estimates of species richness and turnover. Generalized linear mixed models, model selection and model averaging were used to investigate how birds responded to landscape diversity and configuration across the rainfall gradient. Species richness was positively associated with age class diversity, age class configuration and vegetation type diversity. Species turnover was positively associated with age class diversity in areas of lower rainfall but exhibited a negative response in areas of higher rainfall. Neither response variable was associated with vegetation type configuration. This study is one of few landscape scale analyses to provide empirical support for the widely held assumption that spatially variable fire regimes can increase the diversity of faunal assemblages. Further, our results demonstrated consistency in responses of species richness to fire-mediated landscape complexity across a rainfall gradient. Managers can potentially increase bird species richness by increasing both the diversity of fire age classes, and the complexity of age class configuration, within relatively small (300 ha) areas.
    Forest Ecology and Management 04/2014; 318:13–20. DOI:10.1016/j.foreco.2014.01.009 · 2.66 Impact Factor
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