Alan York

Prescribed burning: how can it work to conserve the things we value?

Prescribed burning is a commonly applied management tool, and there has been considerable debate over the efficacy of its application. We review data relating to the effectiveness of prescribed burning in Australia. Specifically, we address two questions: (1) to what extent can fuel reduction burning reduce the risk of loss of human life and economic assets posed from wildfires? (2) To what extent can prescribed burning be used to reduce the risk of biodiversity loss? Data suggest that prescribed burning can achieve a reduction in the extent of wildfires; however, at such levels, the result is an overall increase in the total area of the landscape burnt. Simulation modelling indicates that fuel reduction has less influence than weather on the extent of unplanned fire. The need to incorporate ecological values into prescribed burning programmes is becoming increasingly important. Insufficient data are available to determine if existing programs have been successful. There are numerous factors that prevent the implementation of better prescribed burning practices; most relate to a lack of clearly defined, measurable objectives. An adaptive risk management framework combined with enhanced partnerships between scientists and fire-management agencies is necessary to ensure that ecological and fuel reduction objectives are achieved.

Long-Term Effects of Frequent Low-Intensity Burning on the Abundance of Litter-Dwelling Invertebrates in Coastal Blackbutt Forests of Southeastern Australia

Low-intensity fire is extensively used in Australian dry eucalypt forests to reduce fuel levels. The long-term impact of this management practice on terrestrial invertebrates is, however, unknown and is of concern given their contribution to ecosystem function and forest biodiversity. This study found that areas subjected to frequent low-intensity fire had significantly lower numbers of spiders, ticks and mites, pseudoscorpions, woodlice, springtails, bugs, beetles, ants and insect larvae in the leaf litter compared with adjacent unburnt areas. Taxa numbers were between 41 and 82% lower and these reductions in abundance have led to an overall decline in taxon richness. This decrease was attributed to a reduction in the amount of litter and associated moisture levels, and a simplification of habitat structure. The extent of local and regional extinctions will depend upon the scale of this disturbance, with future studies investigating the impact on individual species within these communities. A comparison of two sampling techniques, pitfall-trapping and litter extraction, highlighted important considerations for spatial components of invertebrate sampling designs.

Fungi and fire in Australian ecosystems: a review of current knowledge, management implications and future directions

Fungi are essential components of all ecosystems in roles including symbiotic partners, decomposers and nutrient cyclers and as a source of food for vertebrates and invertebrates. Fire changes the environment in which fungi live by affecting soil structure, nutrient availability, organic and inorganic substrates and other biotic components with which fungi interact, particularly mycophagous animals. We review the literature on fire and fungi in Australia, collating studies that include sites with different time since fire or different fire regimes. The studies used a variety of methods for survey and identification of fungi and focussed on different groups of fungi, with an emphasis on fruit-bodies of epigeal macrofungi and a lack of studies on microfungi in soil or plant tissues. There was a lack of replication of fire treatment effects in some studies. Nevertheless, most studies reported some consequence of fire on the fungal community. Studies on fire and fungi were concentrated in eucalypt forest in south-west and south-eastern Australia, and were lacking for ecosystems such as grasslands and tropical savannahs. The effects of fire on fungi are highly variable and depend on factors such as soil and vegetation type and variation in fire intensity and history, including the length of time between fires. There is a post-fire flush of fruit-bodies of pyrophilous macrofungi, but there are also fungi that prefer long unburnt vegetation. The few studies that tested the effect of fire regimes in relation to the intervals between burns did not yield consistent results. The functional roles of fungi in ecosystems and the interactions of fire with these functions are explained and discussed. Responses of fungi to fire are reviewed for each fungal trophic group, and also in relation to interactions between fungi and vertebrates and invertebrates. Recommendations are made to include monitoring of fungi in large-scale fire management research programs and to integrate the use of morphological and molecular methods of identification. Preliminary results suggest that fire mosaics promote heterogeneity in the fungal community. Management of substrates could assist in preserving fungal diversity in the absence of specific information on fungi.

Detecting mammals in heterogeneous landscapes: implications for biodiversity monitoring and management

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.

Effects of fire on pollinators and pollination

Summary Increased incidence of landscape fire and pollinator declines with co-extinctions of dependent plant species are both globally significant. Fire can alter species distributions, but its effects on plant–pollinator interactions are poorly understood so its present and future role in coupled plant–pollinator declines cannot be assessed. We develop a conceptual model of fire effects on plant–pollinator interactions. We review the empirical literature in the context of this model to identify important knowledge gaps regarding the processes underlying these effects and the phenotypic traits of flowering plants and pollinators mediating these effects. Fire generates, and plant–pollinator interactions respond to, heterogeneity at multiple spatial scales. There is evidence of local-scale fire effects on these interactions, but landscape-scale effects are poorly understood. Nest location and floral resource utilization primarily mediate pollinator survival during and after fire. Voltinism and mobility traits are potentially important, but poorly studied. Plant traits mediating flowering responses to fire include growth form, phenology and potentially bud location, seasonal changes in bud exposure and response to bud damage. Synthesis and applications. We suggest management actions and an agenda for future research to fill knowledge gaps currently inhibiting predictions of fire effects on plant–pollinator interactions. Fire regimes promoting floral diversity at local scales provide a surrogate means of managing pollinators and pollination while empirical research continues. Above-ground nesting, univoltine pollinators may be particularly vulnerable under expected fire regime changes. Improved knowledge of traits mediating the exploitation of landscape heterogeneity could be used to enhance the persistence of these species. Ultimately, our conceptual framework could be used as a basis for understanding fire effects on aggregate network properties to inform fire management strategies buffering plant–pollinator networks against secondary species extinctions.

Predicting continuous variation in forest fuel load using biophysical models: a case study in south-eastern Australia

The increasing potential for wildfires in Mediterranean-type landscapes has resulted in pressure to mitigate fire threats. This is typically achieved by strategic reduction of fuel. To prioritise fuel management, it is necessary to understand vegetation dynamics and the relationships between plants and fuel. As the direct measurement of fuel in the field is labour intensive, mapped vegetation classes are typically used as to estimate fuel load. As vegetation properties vary continuously, the error in such estimates can be high. Remotely sensed and biophysical data are commonly used for vegetation classification, but rarely for estimating fuel load. This study investigated how fuel load varied with vegetation composition in an Australian woodland and assessed the potential for using biophysical models to create continuous estimates. Fuel was found to be influenced by species abundance, with some species having a greater contribution to load than others. Fuel was found to be somewhat predictable, with quantities related to fire history and several other biophysical variables. Models were applied to create continuous maps of fuel load; these provided a more precise representation of fuel variation than using discrete classes. Improved maps have the potential to facilitate improved prediction of fire behaviour and assist targeted fuel management.

Bird functional diversity decreases with time since disturbance: Does patchy prescribed fire enhance ecosystem function?

Animal species diversity is often associated with time since disturbance, but the effects of disturbances such as fire on functional diversity are unknown. Functional diversity measures the range, abundance, and distribution of trait values in a community, and links changes in species composition with the consequences for ecosystem function. Improved understanding of the relationship between time since fire (TSF) and functional diversity is critical given that the frequency of both prescribed fire and wildfire is expected to increase. To address this knowledge gap, we examined responses of avian functional diversity to TSF and two direct measures of environmental heterogeneity, plant diversity, and structural heterogeneity. We surveyed birds across a 70-year chronosequence spanning four vegetation types in southeast Australia. Six bird functional traits were used to derive four functional diversity indices (richness, evenness, divergence, and dispersion) and the effects of TSF, plant diversity and structural heterogeneity on species richness and the functional diversity indices were examined using mixed models. We used a regression tree method to identify traits associated with species more common in young vegetation. Functional richness and dispersion were negatively associated with TSF in all vegetation types, suggesting that recent prescribed fire generates heterogeneous vegetation and provides greater opportunities for resource partitioning. Species richness was not significantly associated with TSF, and is probably an unreliable surrogate for functional diversity in fire-prone systems. A positive, relationship between functional evenness and structural heterogeneity was comnon to all vegetation types, suggesting that fine-scale (tens of meters) structural variation can enhance ecosystem function. Species more common in young vegetation were primarily linked by their specialist diets, indicating that ecosystem services such as seed dispersal and insect control are enhanced in more recently burnt vegetation. We suggest that patchy prescribed fire sustains functional diversity, and that controlled use of patchy fire to break up large expanses of mature vegetation will enhance ecosystem function.

Bird diversity increases after patchy prescribed fire: implications from a before-after control-impact study

Increasingly, patchy prescribed fire of low severity is used by land managers to mitigate wildfire risk, but there are relatively few experimental studies on the effects of low-severity fire on fauna. We used a before–after control–impact experiment to examine avian responses to prescribed fire at two scales in topographically variable, tall-open eucalypt forest in south-east Australia. We surveyed birds at control and impact areas twice before and twice after fire, and applied mixed models to investigate responses of avian turnover, richness and the occurrence of selected species. Approximately half of the impact area was burnt and topographic variation generated a finger-like configuration of burnt patches on ridges and unburnt patches in gullies. Our findings at the smaller scale (0.8 ha) indicated that the fire resulted in increased bird diversity because a patchwork of burnt and unburnt areas provided a mosaic of distinct successional states in which different species occurred. Additionally, we found that the effect of fire on species richness and occurrence was a function of the presence of unburnt topographic refuges. In contrast, we found no compelling evidence to suggest that birds responded to the fire at the larger scale (400 ha). We conclude that application of low-severity fire in a patchy manner enhanced avian diversity and facilitated the persistence of the birds detected in pre-fire surveys. Although the levels of patchiness required to sustain diverse taxa warrant further study, our findings highlight the importance of formally incorporating patchiness into prescribed burning for the ecologically sensitive management of contemporary landscapes.

Fire effects on pollination in a sexually deceptive orchid

Research into the effectiveness of prescribed fire in managing pollination has only recently begun. The effects of fire on pollination have not been explored in sexually deceptive systems. Further, the potential for multiple effects operating at different spatial scales has not been explored in any pollination system despite multiscale effects on pollination observed in agricultural landscapes. We observed the frequency of pollinator visitation to flowers of sexually deceptive Caladenia tentaculata and related it to the post-fire age class of the vegetation at local and landscape scales. We also related the number of the pollinator’s putative larval hosts (scarab beetles) captured at these sites to age class. At the local scale (i.e. the sample location), visitation was highest in recently burnt sites. At the landscape scale, positive associations were observed between (1) putative pollinator hosts and vegetation burnt 36–50 years ago, and (2) pollinator visitation and vegetation burnt ≥50 years ago. Local- and landscape-scale effects on visitation were synergistic, such that visitation was greatest when fire age was heterogeneous within pollinator foraging range.

Do multiple fires interact to affect vegetation structure in temperate eucalypt forests

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.