Tag Archives: fire

Responses of invasive predators and native prey to a prescribed forest fire

Authors: Bronwyn A Hradsky, Craig Mildwaters, Euan G Ritchie, Fiona Christie, and Julian Di Stefano

Published in: Journal of Mammalogy (early view)

Abstract

Fire shapes biome distribution and community composition worldwide, and is extensively used as a management tool in flammable landscapes. There is growing concern, however, that fire could increase the vulnerability of native fauna to invasive predators.

We developed a conceptual model of the ways in which fire could influence predator–prey dynamics.

Using a before–after, control–impact experiment, we then investigated the short-term effects of a prescribed fire on 2 globally significant invasive mesopredators (red fox, Vulpes vulpes, and feral cat, Felis catus) and their native mammalian prey in a fire-prone forest of southeastern Australia. We deployed motion-sensing cameras to assess species occurrence, collected predator scats to quantify diet and prey choice, and measured vegetation cover before and after fire. We examined the effects of the fire at the scale of the burn block (1,190 ha), and compared burned forest to unburned refuges.

Pre-fire, invasive predators and large native herbivores were more likely to occur at sites with an open understory, whereas the occurrence of most small- and medium-sized native mammals was positively associated with understory cover. Fire reduced understory cover by more than 80%, and resulted in a 5-fold increase in the occurrence of invasive predators. Concurrently, relative consumption of medium-sized native mammals by foxes doubled, and selection of long-nosed bandicoots (Perameles nasuta) and short-beaked echidnas (Tachyglossus aculeatus) by foxes increased. Occurrence of bush rats (Rattus fuscipes) declined. It was unclear if fire also affected the occurrence of bandicoots or echidnas, as changes coincided with normal seasonal variations.

Overall, prescribed fire promoted invasive predators, while disadvantaging their medium-sized native mammalian prey. Further replication and longer-term experiments are needed before these findings can be generalized. Nonetheless, such interactions could pose a serious threat to vulnerable species such as critical weight range mammals. Integrated invasive predator and fire management are recommended to improve biodiversity conservation in flammable ecosystems.

Hradsky BA, Mildwaters C, Ritchie EG, Christie F, Di Stefano J (2017) Responses of invasive predators and native prey to a prescribed forest fire, Journal of Mammalogy PDF DOI

Stemming the tide: progress towards resolving the causes of decline and implementing management responses for the disappearing mammal fauna of northern Australia

Authors: Mark R Ziembicki, John C Z Woinarski, Jonathan K Webb, Eric Vanderduys, Katherine Tuft, James Smith, Euan G Ritchie, Terry B Reardon, Ian J Radford, Noel Preece, Justin Perry, Brett P Murphy, Hugh McGregor, Sarah Legge, Lily Leahy, Michael J Lawes, John Kanowski, Chris N Johnson, Alex James, Anthony D Griffiths, Graeme Gillespie, Anke S K Frank, Alaric Fisher and Andrew A Burbidge.

Abstract

Recent studies at some sites in northern Australia have reported severe and rapid decline of some native mammal species, notwithstanding an environmental context (small human population size, limited habitat loss, substantial reservation extent) that should provide relative conservation security.

All of the more speciose taxonomic groups of mammals in northern Australia have some species for which the conservation status has been assessed as threatened, with 53% of dasyurid, 46% of macropod and potoroid, 33% of bandicoot and bilby, 33% of possum, 31% of rodent, and 24% of bat species being assessed as extinct, threatened or near-threatened.

This paper reviews disparate recent and ongoing studies that provide information on population trends across a broader geographic scope than the previously reported sites, and provides some information on the conservation status and trends for mammal groups (bats, larger macropods) not well sampled in previous monitoring studies. It describes some diverse approaches of studies seeking to document conservation status and trends, and of the factors that may be contributing to observed patterns of decline.

The studies reported provide some compelling evidence that predation by feral cats is implicated in the observed decline, with those impacts likely to be exacerbated by prevailing fire regimes (frequent, extensive and intense fire), by reduction in ground vegetation cover due to livestock and, in some areas, by ‘control’ of dingoes. However the impacts of dingoes may be complex, and are not yet well resolved in this area.

The relative impacts of these individual factors vary spatially (with most severe impacts in lower rainfall and less topographically rugged areas) and between different mammal species, with some species responding idiosyncratically: the most notable example is the rapid decline of the northern quoll Dasyurus hallucatus due to poisoning by the introduced cane toad Rhinella marina, which continues to spread extensively across northern Australia. The impact of disease, if any, remains unresolved.

Recovery of the native mammal fauna may be impossible in some areas. However, there are now examples of rapid recovery following threat management. Priority conservation actions include: enhanced biosecurity for important islands, establishment of a network of substantial predator exclosures, intensive fire management (aimed at increasing the extent of longer-unburnt habitat and in delivering fine scale patch burning), reduction in feral stock in conservation reserves, and acquisition for conservation purposes of some pastoral lands in areas that are significant for mammal conservation.

Ziembicki MR, Woinarski JCZ, Webb JK, Vanderduys E, Tuft K, Smith J, Ritchie EG, Reardon TB, Radford IJ, Preece N, Perry JP, Murphy BP, McGregor H, Legge S, Leahy L, Lawes MJ, Kanowski J, Johnson CN, James A, Griffiths AD, Gillespie G, Frank ASK, Fisher A, Burbidge AA (2015) Stemming the tide: progress towards resolving the causes of decline and implementing management responses for the disappearing mammal fauna of northern Australia, Therya 2015 6(1) 169-225 PDF DOI

The effects of topographic variation and the fire regime on coarse woody debris: Insights from a large wildfire

Fire shapes the composition of ecosystems through its effects on vegetation structure. Fire is integral to the dynamics of coarse woody debris - logs and dead trees - as it both consumes existing debris and generates new material through its influence on tree death and collapse. Image credit: Edgar Vonk via Flickr

Fire shapes the composition of ecosystems through its effects on vegetation structure. Fire is integral to the dynamics of coarse woody debris — logs and dead trees — as it both consumes existing debris and generates new material through its influence on tree death and collapse. Image credit: Edgar Vonk via Flickr

Authors: Michelle Bassett, Evelyn K Chia, Steve W J Leonard, Dale G Nimmo Greg J Holland, Euan G Ritchie, Michael F Clarke and Andrew F Bennett

Published in: Forest Ecology and Management, volume 340 (March 2015)

Abstract

Coarse woody debris (CWD) is a common structural component of terrestrial ecosystems, and provides important habitat for biota.

Fires modify the distribution of CWD, both spatially and temporally. Changes in fire regimes, such as those arising from prescribed burning and changing climatic conditions, make it critical to understand the response of this resource to fire.

We created a conceptual model of the effects of fire on logs and dead trees in topographically diverse forests in which trees often survive severe fire. We then surveyed paired sites, in a damp gully and adjacent drier slope, ~3.5 years after a large wildfire in south-eastern Australia.

Sites were stratified by fire severity (unburnt, understorey burnt and severely burnt), and fire history (burnt ≤3 years or ≥20 years prior to the wildfire).

Both components of the fire regime influenced CWD availability in gullies. Severe wildfire and fire history ≤3 years reduced the volume of small logs (10–30 cm diameter) in gullies, while severe wildfire increased the number of large dead trees in gullies. CWD on slopes was not affected by fire severity or history at ~3.5 years post-fire.

Log volumes on slopes may recover more quickly after wildfire through rapid collapse of branches and trees. Gullies generally supported more logs than slopes, but longer inter-fire intervals in gullies may allow fuel loads to accumulate and lead to comparatively larger fire impacts.

Given that fire severity and fire interval are predicted to change in many fire-prone ecosystems in coming decades, this study highlights the importance of understanding the interacting effects of multiple components of the fire regime with landscape structure. In particular, variation in fire interval and fire severity in relation to topographic position will influence the pattern of accumulation of coarse woody debris across the landscape, and therefore the structure and quality of habitats for biota.

Bassett M, Chia EK, Leonard SWJ, Nimmo DG, Holland GJ, Ritchie EG, Clarke MF, Bennett AF (2015) The effects of topographic variation and the fire regime on coarse woody debris: Insights from a large wildfire, Forest Ecology and Management, 340, 126–134 PDF DOI

Does fire influence the landscape-scale distribution of an invasive mesopredator?

Authors: Catherine J Payne, Euan G Ritchie, Luke T Kelly and Dale G Nimmo.

Abstract

Predation and fire shape the structure and function of ecosystems globally. However, studies exploring interactions between these two processes are rare, especially at large spatial scales. This knowledge gap is significant not only for ecological theory, but also in an applied context, because it limits the ability of landscape managers to predict the outcomes of manipulating fire and predators.

We examined the influence of fire on the occurrence of an introduced and widespread mesopredator, the red fox (Vulpes vulpes), in semi-arid Australia. We used two extensive and complimentary datasets collected at two spatial scales.

We examined the influence of fire on the distribution of introduced red foxes in semi-arid Australia. Image credit Area51Bel [CC-BY-SA 3.0] via Wikimedia Commons.

We examined the influence of fire on the distribution of introduced red foxes in semi-arid Australia. Image credit Area51Bel [CC-BY-SA 3.0] via Wikimedia Commons.

At the landscape-scale, we surveyed red foxes using sand-plots within 28 study landscapes — which incorporated variation in the diversity and proportional extent of fire-age classes — located across a 104 000 km² study area. At the site-scale, we surveyed red foxes using camera traps at 108 sites stratified along a century-long post-fire chronosequence (0–105 years) within a 6630 km² study area.

Red foxes were widespread both at the landscape and site-scale. Fire did not influence fox distribution at either spatial scale, nor did other environmental variables that we measured.
Our results show that red foxes exploit a broad range of environmental conditions within semi-arid Australia.

The presence of red foxes throughout much of the landscape is likely to have significant implications for native fauna, particularly in recently burnt habitats where reduced cover may increase prey species’ predation risk.

Payne CJ, Ritchie EG, Kelly LT, Nimmo DG (2014) Does Fire Influence the Landscape-Scale Distribution of an Invasive Mesopredator? PLoS ONE 9(10): e107862 PDF DOI 

Published: Refuges for fauna in fire-prone landscapes — their ecological function and importance

Authors: Robinson NM, Leonard SWJ, Ritchie EG, Bassett M, Chia EK, Buckingham S, Gibb H, Bennett AF and Clarke MF

Summary

Rapid environmental change is placing increasing pressure on the survival of many species globally. Ecological refuges can mitigate the impacts of change by facilitating the survival or persistence of organisms in the face of disturbance events that would otherwise lead to their mortality, displacement or extinction. Refuges may have a critical influence on the succes- sional trajectory and resilience of ecosystems, yet their function remains poorly understood.

We review and describe the role of refuges in faunal conservation in the context of fire, a globally important disturbance process.

Refuges have three main functions in relation to fire: they enhance immediate survival during a fire event, facilitate the persistence of individuals and populations after fire and assist in the re-establishment of populations in the longer term. Refuges may be of natural or anthropogenic origin, and in each case, their creation can arise from deterministic or stochas- tic processes. The specific attributes of refuges that determine their value are poorly known, but include within-patch attributes relating to vegetation composition and structure; patch- scale attributes associated with their size and shape; and the landscape context and spatial arrangement of the refuge in relation to fire patterns and land uses.

Synthesis and applications: Refuges are potentially of great importance in buffering the effects of wildfire on fauna. There is an urgent need for empirical data from a range of eco- systems to better understand what constitutes a refuge for different taxa, the spatial and tem- poral dynamics of species’ use of refuges and the attributes that most influence their value to fauna. Complementary research is also required to evaluate threats to naturally occurring ref- uges and the potential for management actions to protect, create and enhance refuges. Knowledge of the spatial arrangement of refuges that enhance the persistence of fire-sensitive species will aid in making decisions concerning land and fire management in conservation reserves and large natural areas. Global change in the magnitude and extent of fire regimes means that refuges are likely to be increasingly important for the conservation of biodiversity in fire-prone environments.

Robinson NM, Leonard SWJ, Ritchie EG, Bassett M, Chia EK, Buckingham S, Gibb H, Bennett AF, Clarke MF (2013) Refuges for fauna in fire-prone landscapes: their ecological function and importance. Journal of Applied Ecology DOI PDF