Emma Knight

Land management practices associated with house loss in wildfires

Losses to life and property from unplanned fires (wildfires) are forecast to increase because of population growth in peri-urban areas and climate change. In response, there have been moves to increase fuel reduction—clearing, prescribed burning, biomass removal and grazing—to afford greater protection to peri-urban communities in fire-prone regions. But how effective are these measures? Severe wildfires in southern Australia in 2009 presented a rare opportunity to address this question empirically. We predicted that modifying several fuels could theoretically reduce house loss by 76%–97%, which would translate to considerably fewer wildfire-related deaths. However, maximum levels of fuel reduction are unlikely to be feasible at every house for logistical and environmental reasons. Significant fuel variables in a logistic regression model we selected to predict house loss were (in order of decreasing effect): (1) the cover of trees and shrubs within 40 m of houses, (2) whether trees and shrubs within 40 m of houses was predominantly remnant or planted, (3) the upwind distance from houses to groups of trees or shrubs, (4) the upwind distance from houses to public forested land (irrespective of whether it was managed for nature conservation or logging), (5) the upwind distance from houses to prescribed burning within 5 years, and (6) the number of buildings or structures within 40 m of houses. All fuel treatments were more effective if undertaken closer to houses. For example, 15% fewer houses were destroyed if prescribed burning occurred at the observed minimum distance from houses (0.5 km) rather than the observed mean distance from houses (8.5 km). Our results imply that a shift in emphasis away from broad-scale fuel-reduction to intensive fuel treatments close to property will more effectively mitigate impacts from wildfires on peri-urban communities.

Marker-Based Quantitative Genetics in the Wild?: The Heritability and Genetic Correlation of Chemical Defenses in Eucalyptus

Marker-based methods for estimating heritability and genetic correlation in the wild have attracted interest because traditional methods may be impractical or introduce bias via G × E effects, mating system variation, and sampling effects. However, they have not been widely used, especially in plants. A regression-based approach, which uses a continuous measure of genetic relatedness, promises to be particularly appropriate for use in plants with mixed-mating systems and overlapping generations. Using this method, we found significant narrow-sense heritability of foliar defense chemicals in a natural population of Eucalyptus melliodora. We also demonstrated a genetic basis for the phenotypic correlation underlying an ecological example of conditioned flavor aversion involving different biosynthetic pathways. Our results revealed that heritability estimates depend on the spatial scale of the analysis in a way that offers insight into the distribution of genetic and environmental variance. This study is the first to successfully use a marker-based method to measure quantitative genetic parameters in a tree. We suggest that this method will prove to be a useful tool in other studies and offer some recommendations for future applications of the method.

The Effects of Wildfire on Mortality and Resources for an Arboreal Marsupial: Resilience to Fire Events but Susceptibility to Fire Regime Change

Background Big environmental disturbances have big ecological effects, yet these are not always what we might expect. Understanding the proximate effects of major disturbances, such as severe wildfires, on individuals, populations and habitats will be essential for understanding how predicted future increases in the frequency of such disturbances will affect ecosystems. However, researchers rarely have access to data from immediately before and after such events. Here we report on the effects of a severe and extensive forest wildfire on mortality, reproductive output and availability of key shelter resources for an arboreal marsupial. We also investigated the behavioural response of individuals to changed shelter resource availability in the post-fire environment. Methodology/Principal Findings We fitted proximity-logging radiotransmitters to mountain brushtail possums (Trichosurus cunninghami) before, during and after the 2009 wildfires in Victoria, Australia. Surprisingly, we detected no mortality associated with the fire, and despite a significant post-fire decrease in the proportion of females carrying pouch young in the burnt area, there was no short-term post-fire population decline. The major consequence of this fire for mountain brushtail possums was the loss of over 80% of hollow-bearing trees. The types of trees preferred as shelter sites (highly decayed dead standing trees) were those most likely to collapse after fire. Individuals adapted to resource decline by being more flexible in resource selection after the fire, but not by increased resource sharing. Conclusions/Significance Despite short-term demographic resilience and behavioural adaptation following this fire, the major loss of decayed hollow trees suggests the increased frequency of stand-replacing wildfires predicted under climate change will pose major challenges for shelter resource availability for hollow-dependent fauna. Hollow-bearing trees are typically biological legacies of previous forest generations in post-fire regrowth forests but will cease to be recruited to future regrowth forests if the interval between severe fires becomes too rapid for hollow formation.

Pocket parks in a compact city: how do birds respond to increasing residential density?

Abstract The desire to improve urban sustainability is motivating many city planners to adopt growth strategies that increase residential density, leading to substantial changes to urban landscapes. What effect this change will have on biodiversity remains unclear, but it is expected that the role of public greenspace in providing wildlife habitat will become critical. We explored the role of urban “pocket parks” as habitat for birds, and how this role changed with increasing residential density in the surrounding neighbourhood. We found that parks in neighbourhoods with high levels of public greenspace (corresponding to less residential land) supported more bird species and individuals overall, and more woodland-dependent species, insectivores and hollow-nesters. Total greenspace area was more important (included in the best ranked models for all bird responses) than the configuration (number, average size and connectivity) of greenspace patches. The majority of species were common suburban birds, indicating that species we assume are tolerant to urban areas will be negatively affected by increasing residential density. Parks form part of an interconnected network of urban open space. For parks to continue to support a diverse native bird community, the network must be viewed, managed, and maintained in its entirety. We suggest three key management actions to improve the bird diversity values of urban greenspaces in compact cities: (1) Increase urban greenspace cover in residential neighbourhoods. (2) Increase vegetation structure in greenspace. (3) Encourage homeowners to plant trees and shrubs.

Kin selection in den sharing develops under limited availability of tree hollows for a forest marsupial

Animal social behaviour is not static with regard to environmental change. Flexibility in cooperative resource use may be an important response to resource decline, mediating the impacts of resource availability on fitness and demography. In forest ecosystems, hollow trees are key den resources for many species, but are declining worldwide owing to forestry. Altered patterns of den sharing may mediate the effects of the decline of this resource. We studied den-sharing interactions among hollow-dependent Australian mountain brushtail possums to investigate how spatial variation in hollow tree availability affects resource sharing and kin selection. Under reduced den availability, individuals used fewer dens and shared them less often. This suggests increased territoriality in the presence of resource competition. Further, there was a switch from kin avoidance to kin preference with decreasing hollow tree availability. This was driven primarily by a change in den sharing among siblings. The inclusive fitness benefits of den sharing with kin are likely to increase under resource-limiting conditions, but are potentially outweighed by the benefits of associating with non-relatives (avoidance of inbreeding or pathogen transmission) where dens are abundant. We discuss how predictions from social evolutionary theory can contribute to understanding animal responses to landscape change.

Microhabitat heterogeneity influences offspring sex allocation and spatial kin structure in possums

1. Sex allocation theory predicts that where dispersal is sex biased, the fitness consequences of producing male or female offspring are mediated by resource availability and maternal competitive ability. Females in poorer condition are expected to favour dispersing offspring to minimize resource competition with kin. Environmental heterogeneity may drive spatial variation in sex allocation through resource competition-related benefits to females and territory quality benefits to dispersing or philopatric offspring. 2. Here, we demonstrate that microhabitat heterogeneity can drive extremely fine-scale spatial heterogeneity in offspring sex allocation. Female bobucks (Trichosurus cunninghami) in temperate rainforest were more likely to produce male offspring than those in surrounding Eucalyptus forest. 3. A maternal physiological effect was identified, in that females of lower body mass were more likely to produce male offspring. This finding is consistent with resource competition predictions, in that smaller females are expected to have poorer competitive ability. 4. Genetic spatial autocorrelation analysis identified males as the more dispersing sex. Furthermore, overproduction of males by mothers in the rainforest habitat was geographically concordant with reduced philopatry, as inferred from spatial genetic analysis. This provides empirical validation of dispersal-related explanations of offspring sex allocation: that production of offspring of the dispersing sex minimizes the potential for resource competition with kin. 5. Spatial variation in dispersal via sex allocation responses to environmental heterogeneity can potentially contribute to spatial patterns in population dynamics.

Magnitude-based inference: a statistical review.

Supplemental digital content is available in the text.

Linking bird species traits to vegetation characteristics in a future urban development zone: implications for urban planning

Identifying the relationships between species traits and patch-scale vegetation characteristics in areas designated for urban development can improve our understanding of how animal communities may change with urbanization. We explored the implications of this premise to the urban planning process in a mixed-use landscape in Canberra (Australia), prior to its development into new suburbs. We used RLQ analysis to relate bird foraging, nesting and body size traits to patch-scale vegetation characteristics. Relationships between species traits and vegetation characteristics within the development zone suggest that species that forage and nest on the ground and in the understory strata, and smaller-bodied species will be most negatively affected by urbanization. Identifying the relationships between species traits and vegetation characteristics may be used by urban planners to (i) identify potentially critical habitat and species at risk from development, (ii) inform the choice of impact mitigation measures, and/or (iii) distinguish between high and low mitigation measures. Analyses conducted early in the planning process can then be used to allocate proposed land uses in an ecologically sensitive way, and to plan appropriate mitigation measures.

Bird community responses to the edge between suburbs and reserves

New insights into community-level responses at the urban fringe, and the mechanisms underlying them, are needed. In our study, we investigated the compositional distinctiveness and variability of a breeding bird community at both sides of established edges between suburban residential areas and woodland reserves in Canberra, Australia. Our goals were to determine if: (1) community-level responses were direct (differed with distance from the edge, independent of vegetation) or indirect (differed in response to edge-related changes in vegetation), and (2) if guild-level responses provided the mechanism underpinning community-level responses. We found that suburbs and reserves supported significantly distinct bird communities. The suburban bird community, characterised by urban-adapted native and exotic species, had a weak direct edge response, with decreasing compositional variability with distance from the edge. In comparison, the reserve bird community, characterised by woodland-dependent species, was related to local tree and shrub cover. This was not an indirect response, however, as tree and shrub cover was not related to edge distance. We found that the relative richness of nesting, foraging and body size guilds also displayed similar edge responses, indicating that they underpinned the observed community-level responses. Our study illustrates how community-level responses provide valuable insights into how communities respond to differences in resources between two contrasting habitats. Further, the effects of the suburban matrix penetrate into reserves for greater distances than previously thought. Suburbs and adjacent reserves, however, provided important habitat resources for many native species and the conservation of these areas should not be discounted from continued management strategies.

The Effects of a Calcium-Rich Pre-Exercise Meal on Biomarkers of Calcium Homeostasis in Competitive Female Cyclists: A Randomised Crossover Trial

Cycling is recognised as a sport in which there is a high incidence of poor bone health. Sweat calcium losses may contribute to this. Purpose To examine whether a calcium-rich pre-exercise meal attenuates exercise-induced perturbations of bone calcium homeostasis caused by maintenance of sweat calcium losses. Methods Using a randomized, counterbalanced crossover design, 32 well-trained female cyclists completed two 90 min cycling trials separated by 1 day. Exercise trials were preceded 2 hours by either a calcium-rich (1352 ± 53 mg calcium) dairy based meal (CAL) or a control meal (CON; 46 ± 7 mg calcium). Blood was sampled pre-trial; pre-exercise; and immediately, 40 min, 100 min and 190 min post-exercise. Blood was analysed for ionized calcium and biomarkers of bone resorption (Cross Linked C-Telopeptide of Type I Collagen (CTX-I), Cross Linked C-Telopeptide of Type II Collagen (CTX-II), Parathyroid Hormone (PTH), and bone formation (Procollagen I N-Terminal Propeptide (PINP)) using the established enzyme-linked immunosorbent assay technique. Results PTH and CTX-I increased from pre-exercise to post-exercise in both conditions but was attenuated in CAL (p < 0.001). PTH was 1.55 [1.20, 2.01] times lower in CAL immediately post-exercise and 1.45 [1.12, 1.88] times lower at 40 min post-exercise. CTX-I was 1.40 [1.15, 1.70] times lower in CAL at immediately post-exercise, 1.30 [1.07, 1.57] times lower at 40 min post-exercise and 1.22 [1.00, 1.48] times lower at 190 min post-exercise (p < 0.05). There was no significant interaction between pre-exercise meal condition and time point for CTX-II (p = 0.732) or PINP (p = 0.819). Conclusion This study showed that a calcium-rich pre-exercise breakfast meal containing ~1350 mg of calcium consumed ~90 min before a prolonged and high intensity bout of stationary cycling attenuates the exercise induced rise in markers of bone resorption – PTH and CTX-I. Trial Registration Australian New Zealand Clinical Trials Registry ACTRN12614000675628