Effect of Phytophthora cinnamomi on the habitat utilization of Antechinus stuartii in a Victorian forest

Phytophthora cinnamomi (Cinnamon fungus) is a pathogenic soil fungus which infects plant communities along the south-eastern coast of Australia, and the south-western corner of Western Australia. The symptoms of this disease include chlorosis, death of branches (ie. ‘dieback’), retarded growth and the eventual death of infected plants. This leads to devastating effects upon plant communities by altering both the structural and floristic characteristics of these communities. Small mammal species are dependent on specific features of their habitat such as vegetation structure and floristics. This thesis investigated alterations to the habitat of the insectivorous marsupial mouse, Antechinus stuartii, due to the presence of P. cinnamomi. The study was undertaken in an area of an open forest in the Brisbane Ranges, Victoria. Significant changes were found in both the floristic composition and structure of the vegetation at study sites infected with P, cinnamomi, compared to uninfected sites. The habitat utilization by A. stuartii of uninfected and infected vegetation was investigated using live trapping and radio-telemetric techniques. Capture rates were higher at sites uninfected by P. cinnamomi, and both male and females selected areas free from infection. Home range areas of males were significantly larger than those of females as assessed by telemetry. Both sexes spent a high proportion of time in areas dominated by Xanthorrhoea australis (Austral grass tree). There were significant relationships between the abundance of A. stuartii and the denseness of vegetation above 1 metre in height, and in particular, the proportion of cover afforded by X. australis. There were no significant differences in the cover of Eucalyptus spp. between uninfected and infected sites, but there were significantly more nest hollows in infected areas. The abundance of invertebrates was examined using pitfall traps. There were no significant differences in the abundance of the larger invertebrate taxa at infected and uninfected sites, but higher abundances of some micro-invertebrate groups in infected areas were recorded. The most likely factors considered to be influential in the habitat selection of A. stuartii were vegetation structure, and the presence of X. australis. To assess whether these factors were important the leaves of X. australis were removed with a brushcutter, to mimic the early effects of infection with P. cinnamomi. Animals did not respond to the alteration of vegetation structure in the short term (3-4 days). Longer-term experiments are required to assess the habitat utilization of A. stuartii at different periods following habitat manipulation. The implications of the presence of P. cinnamomi on the conservation of fauna are discussed. The destructive nature of the pathogen, and the slow rate of recovery from the disease, means that P. cinnamomi can be considered a threatening process to plant communities and the fauna that reside within that habitat. Future management of this disease within natural areas must therefore be cognisant of the potential of P. cinnamomi to significantly affect faunal as well as vegetative communities.

The short-term responses of small mammals to wildfire in semiarid mallee shrubland, Australia

Context. Wildfire is a major driver of the structure and function of mallee eucalypt- and spinifex-dominated landscapes. Understanding how fire influences the distribution of biota in these fire-prone environments is essential for effective ecological and conservation-based management.

Aims. We aimed to (1) determine the effects of an extensive wildfire (118 000 ha) on a small mammal community in the mallee shrublands of semiarid Australia and (2) assess the hypothesis that the fire-response patterns of small mammals can be predicted by their life-history characteristics.

Methods. Small-mammal surveys were undertaken concurrently at 26 sites: once before the fire and on four occasions following the fire (including 14 sites that remained unburnt). We documented changes in small-mammal occurrence before and after the fire, and compared burnt and unburnt sites. In addition, key components of vegetation structure were assessed at each site.

Key results. Wildfire had a strong influence on vegetation structure and on the occurrence of small mammals. The mallee ningaui, Ningaui yvonneae, a dasyurid marsupial, showed a marked decline in the immediate post-fire environment, corresponding with a reduction in hummock-grass cover in recently burnt vegetation. Species richness of native small mammals was positively associated with unburnt vegetation, although some species showed no clear response to wildfire.

Conclusions. Our results are consistent with the contention that mammal responses to fire are associated with their known life-history traits. The species most strongly affected by wildfire, N. yvonneae, has the most specific habitat requirements and restricted life history of the small mammals in the study area. The only species positively associated with recently burnt vegetation, the introduced house mouse, Mus domesticus, has a flexible life history and non-specialised resource requirements.

Implications. Maintaining sources for recolonisation after large-scale wildfires will be vital to the conservation of native small mammals in mallee ecosystems.

Fire and the conservation of the avifauna of mallee ecosystems

This research demonstrates that in mallee ecosystems the bird community changes with time-since-fire and is influenced by the spatial arrangement of landscape mosaics comprised of different post-fire-age vegetation. Fire alters vegetation structure and food availability for birds. The management of fire is critical for the conservation of mallee birds.

The Mallee Fire and Biodiversity Project

Fire is a widespread disturbance and an important ecological process in semi-arid mallee ecosystems of southern Australia. Understanding the effects of fire on plants and animals is a key challenge for the conservation and management of biodiversity in this ecosystem. Commenctngin2006, the Mallee Fire and Biodiversity Project is investigating the effects of fire on range of taxa (vascular plants, invertebrates, reptiles, birds and mammals), with a focus on the influence of the properties of 'fire mosaics' on biota. A 'whole of landscape' design was employed, in which the flora and fauna were sampled in 28 study landscapes, each4 km in diameter (12.5 km2) across a 104,000 km2 area of the Murray Mallee region of Victoria, SA and NSW. Here, we summarise some key results and outputs from this project to date. These include: detailed maps of fire history and major vegetation types; a method for predicting the age of mallee vegetation; novel information about the distribution of fire age-classes in the region; and changes to vegetation structure and in the occurrence of reptile, bird and mammal species over a century-long post-fire time-frame. We also present an overview of the effects of fire mosaics (extent of particular age classes, diversity of fire age-classes) on the richness of some mallee fauna. A wealth of knowledge has been developed through the Mallee Fire and Biodiversity Project that will assist the management of mallee ecosystems in southern Australia for the future.

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

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. 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.

Why do some species have geographically varying responses to fire history?

A capacity to predict the effects of fire on biota is critical for conservation in fire-prone regions as it assists managers to anticipate the outcomes of different approaches to fire management. The task is complicated because species' responses to fire can vary geographically. This poses challenges, both for conceptual understanding of post-fire succession and fire management. We examine two hypotheses for why species may display geographically varying responses to fire. 1) Species' post-fire responses are driven by vegetation structure, but vegetation - fire relationships vary spatially (the 'dynamic vegetation' hypothesis). 2) Regional variation in ecological conditions leads species to select different post-fire ages as habitat (the 'dynamic habitat' hypothesis). Our case study uses data on lizards at 280 sites in a ~ 100 000 km2 region of south-eastern Australia. We compared the predictive capacity of models based on 1) habitat associations, with models based on 2) fire history and vegetation type, and 3) fire history alone, for four species of lizards. Habitat association models generally out-performed fire history models in terms of predictive capacity. For two species, habitat association models provided good discrimination capacity even though the species showed geographically varying post-fire responses. Our results support the dynamic vegetation hypothesis, that spatial variation in relationships between fire and vegetation structure results in regional variation in fauna-fire relationships. These observations explain how the widely recognised 'habitat accommodation' model of animal succession can be conceptually accurate yet predictively weak. © 2014 The Authors.

A game of cat-and-mouse: microhabitat influences rodent foraging in recently burnt but not long unburnt shrublands

We investigated the influence of vegetation structure and fire history on the foraging behavior of small rodents (Notomys mitchellii, Pseudomys hermannsburgensis, and Mus musculus) by conducting giving-up density (GUD) experiments in recently burnt (9–13 years since last fire) and long unburnt shrublands (> 40 years), and open and sheltered microhabitats, in a semiarid region of Western Australia. We predicted that rodents would spend less time foraging in recently burnt shrublands and open microhabitat and that the influence of microhabitat would be weaker in long unburnt compared to more recently burnt vegetation. Our findings show that fire history and microhabitat structure influence the foraging behavior of the study species and that the influence of microhabitat varies between fire histories. GUDs were higher in long unburnt vegetation and in open microhabitats. There was a microhabitat effect in recently burnt vegetation, but not in long unburnt. Rodents foraged more in sheltered microhabitats probably because predator encounters are less likely to occur there and it provides them with greater refuge from predation. The presence of a microhabitat effect in recently burnt, but not long unburnt vegetation suggests that understory vegetation density is more important in mediating predation risk than canopy density. Future studies of small mammal responses to land management actions should include behavioral, as well as population-level responses to differing fire regimes.

Annual variation in the distribution of summer snowdrifts in the Kosciuszko alpine area, Australia, and its effect on the composition and structure of alpine vegetation

Australian alpine ecosystems are expected to diminish in extent as global warming intensifies. Alpine vegetation patterns are influenced by the duration of snow cover including the presence of snowdrifts in summer, but there is little quantitative information on landscape-scale relationships between vegetation patterns and the frequency of occurrence of persistent summer snowdrifts in the Australian alps. We mapped annual changes in summer snowdrifts in the Kosciuszko alpine region, Australia, from Landsat TM images and modelled the frequency of occurrence of persistent summer snowdrifts from long-term records (1954–2003) of winter snow depth. We then compared vegetation composition and structure among four classes that differed in the frequency of occurrence of persistent summer snowdrifts. We found a curvilinear relationship between annual winter snow depth and the area occupied by persistent snowdrifts in the following summer (r²=0.9756). Only 21 ha (0.42% of study area) was predicted to have supported summer snowdrifts in 80% of the past 50 years, while 440 ha supported persistent summer snow in 10% of years. Mean cover and species richness of vascular plants declined significantly, and species composition varied significantly, as the frequency of summer snow persistence increased. Cushion plants and rushes were most abundant where summer snowdrifts occurred most frequently, and shrubs, grasses and sedges were most abundant in areas that did not support snowdrifts in summer. The results demonstrate strong regional relationships between vegetation composition and structure and the frequency of occurrence of persistent summer snowdrifts. Reductions in winter snow depth due to global warming are expected to lead to substantial reductions in the extent of persistent summer snowdrifts. As a consequence, shrubs, grasses and sedges are predicted to expand at the expense of cushion plants and rushes, reducing landscape vegetation diversity. Fortunately, few vascular plant species (e.g. Ranunculus niphophilus) appear to be totally restricted to areas where summer snow occurs most frequently. The results from this study highlight potential indicator species that could be monitored to assess the effects of global warming on Australian alpine environments.

Thresholds, incidence functions, and species-specific cues : responses of woodland birds to landscape structure in south-eastern Australia

Looking out from a vantage point across a large tract of forest gives a superficial impression of uniformity: the crowns of canopy trees follow the folds and contours of the landscape to provide a continuous cover of wooded vegetation. But this visual appearance belies the truth: forested landscapes are far from uniform. On closer examination, they comprise a complex mosaic of different vegetation types and and stands of different age-classes, differing structural features, and modified to a varying extent by human land-uses. Forests have a critical role in the conservation of biodiversity throughout the world (Peterken 1996; Laurance and Bierregard 1997; Lindenmayer and Franklin 2002) and a key feature contributing to their conservation value is the response of forest biota to the heterogeneity inherent in forested landscapes (Lindenmayer et al. 2006). Consequently, an understanding of the implications of landscape structure for the maintainance of species and ecological processes is an important foundation for forest management and biodiversity conservation.

Mallee Emu-wren (Stipiturus mallee) : multi-scale habitat requirements and population structure

This multi-disciplinary investigation found that: i) in Triodia-mallee the Mallee Emu-wren requires vegetation greater than 16-18 years since last burned, with high coverage of mature growth-phase Triodia scariosa (spinifex) and, ii) the species is panmictic with relatively low genetic diversity and evidence of genetic drift and bottlenecks.

Stable isotope-based community metrics as a tool to identify patterns in food web structure in east African estuaries

1.Quantitative tools to describe biological communities are important for conservation and ecological management. The analysis of trophic structure can be used to quantitatively describe communities. Stable isotope analysis is useful to describe trophic organization, but statistical models that allow the identification of general patterns and comparisons between systems/sampling periods have only recently been developed. 2.Here, stable isotope-based Bayesian community-wide metrics are used to investigate patterns in trophic structure in five estuaries that differ in size, sediment yield and catchment vegetation cover (C3/C4): the Zambezi in Mozambique, the Tana in Kenya and the Rianila, the Betsiboka and Pangalanes Canal (sampled at Ambila) in Madagascar. 3.Primary producers, invertebrates and fish of different trophic ecologies were sampled at each estuary before and after the 2010–2011 wet season. Trophic length, estimated based on δ15N, varied between 3·6 (Ambila) and 4·7 levels (Zambezi) and did not vary seasonally for any estuary. Trophic structure differed the most at Ambila, where trophic diversity and trophic redundancy were lower than at the other estuaries. Among the four open estuaries, the Betsiboka and Tana (C4-dominated) had lower trophic diversity than the Zambezi and Rianila (C3-dominated), probably due to the high loads of suspended sediment, which limited the availability of aquatic sources. 4.There was seasonality in trophic structure at Ambila and Betsiboka, as trophic diversity increased and trophic redundancy decreased from the prewet to the postwet season. For Ambila, this probably resulted from the higher variability and availability of sources after the wet season, which allowed diets to diversify. For the Betsiboka, where aquatic productivity is low, this was likely due to a greater input of terrestrial material during the wet season. 5.The comparative analysis of community-wide metrics was useful to detect patterns in trophic structure and identify differences/similarities in trophic organization related to environmental conditions. However, more widespread application of these approaches across different faunal communities in contrasting ecosystems is required to allow identification of robust large-scale patterns in trophic structure. The approach used here may also find application in comparing food web organization before and after impacts or monitoring ecological recovery after rehabilitation.