ORCID Profile
0000-0003-3702-9504
Current Organisation
University of Melbourne
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Publisher: Elsevier BV
Date: 09-2017
Publisher: Elsevier BV
Date: 09-2022
Publisher: CSIRO Publishing
Date: 15-09-2023
DOI: 10.1071/WF23007
Publisher: CSIRO Publishing
Date: 22-09-2023
DOI: 10.1071/WF22219
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/BT19112
Abstract: When flammable plant species become dominant they can influence the flammability of the entire vegetation community. Therefore, it is important to understand the environmental factors affecting the abundance of such species. These factors can include disturbances such as fire, which can promote the dominance of flammable grasses causing a positive feedback of flammability (grass–fire cycle). We examined the potential factors influencing the abundance of a flammable grass found in the understoreys of forests in south-east Australia, the forest wiregrass (Tetrarrhena juncea R.Br.). When wiregrass is abundant, its structural characteristics can increase the risk of wildfire ignition and causes fire to burn more intensely. We measured the cover of wiregrass in 126 sites in mountain ash forests in Victoria, Australia. Generalised additive models were developed to predict cover using climatic and site factors. The best models were selected using an information theoretic approach. The statistically significant factors associated with wiregrass cover were annual precipitation, canopy cover, disturbance type, net solar radiation, precipitation seasonality and time since disturbance. Canopy cover and net solar radiation were the top contributors in explaining wiregrass cover variability. Wiregrass cover was predicted to be high in recently disturbed areas where canopy cover was sparse, light levels high and precipitation low. Our findings suggest that in areas with wiregrass, disturbances such as fire that reduce canopy cover can promote wiregrass dominance, which may, in turn, increase forest flammability.
Publisher: MDPI AG
Date: 20-05-2019
DOI: 10.3390/F10050436
Abstract: High frequency wildfires can shift the structure and composition of obligate seeder forests and initiate replacement with alternative vegetation states. In some forests, the alternative stable state is drier and more easily burned by subsequent fires, driving a positive feedback that promotes further wildfire and perpetuates alternative stable states. Mountain Ash (Eucalyptus regnans (F.Muell.)) forests are highly valued for their bio ersity, water, timber and carbon. Fires are a natural part of the lifecycle of these forests, but too frequent fires can eliminate Mountain Ash and trigger a transition to lower stature, non-eucalypt forests which are dominated by understorey species. This study sought to better understand the fuel moisture dynamics of alternative stable states resulting from high frequency wildfires. A vegetation mosaic in the Central Highlands, Victoria created a unique opportunity to measure fuel moisture in adjacent forest stands that differed in overstorey species composition and time since fire. Specifically, we measured fuel moisture and microclimate at two eucalypt sites (9 and 79 years old) and three non-eucalypt sites (two 9 year old and one 79 year old). Fuel availability, defined here as the number of days surface fuels were below 16% and dry enough to ignite and sustain fire, was calculated to estimate flammability. Fuel availability differed between sites, particularly as a function of time since fire, with recently burnt sites available to burn more often (4–17 versus 0–3 days). There were differences in fuel availability between non-eucalypt sites of the same age, suggesting that high frequency fire does not always lead to the same vegetation condition or outcome for fuel availability. This indicates there is potential for both positive and negative flammability feedbacks following state transition depending on the composition of the non-eucalypt state. This is the first study to provide empirical insight into the fuel moisture dynamics of alternative stable states in Mountain Ash forests.
Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 02-2019
Publisher: MDPI AG
Date: 20-06-2021
DOI: 10.3390/F12060812
Abstract: Shrub encroachment of grassland and woodland ecosystems can alter wildfire behaviour and threaten ecological values. Australian fire managers are using mechanical mastication to reduce the fire risk in encroached ecosystems but are yet to evaluate its effectiveness or ecological impact. We asked: (1) How does fuel load and structure change following mastication? (2) Is mastication likely to affect wildfire rates of spread and flame heights? and (3) What is the impact of mastication on flora species richness and ersity? At thirteen paired sites (masticated versus control n = 26), located in Victoria, Australia, we measured fuel properties (structure, load and hazard) and floristic ersity (richness and Shannon’s H) in 400 mP2 plots. To quantify the effects of mastication, data were analysed using parametric and non-parametric paired s le techniques. Masticated sites were grouped into two categories, 0–2 and 3–4 years post treatment. Fire behaviour was predicted using the Dry Eucalypt Forest Fire Model. Mastication with follow-up herbicide reduced the density of taller shrubs, greater than 50 cm in height, for at least 4 years. The most recently masticated sites (0–2 years) had an almost 3-fold increase in dead fine fuel loads and an 11-fold increase in dead coarse fuel loads on the forest floor compared with the controls. Higher dead coarse fuel loads were still evident after 3–4 years. Changes to fuel properties produced a reduction in predicted flame heights from 22 m to 5–6 m under severe fire weather conditions, but no change in the predicted fire rate of spread. Reductions in flame height would be beneficial for wildfire suppression and could reduce the damage to property from wildfires. Mastication did not have a meaningful effect on native species ersity, but promoted the abundance of some exotic species.
Publisher: Elsevier BV
Date: 09-2016
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/WF18070
Abstract: Fires burning under marginal fire-weather conditions tend to be patchy in terms of their spatial coverage. This patchiness is partially driven by variability in the ignitability of the fuel bed. An understanding of fuel-bed ignitability through space and time would help fire managers to more effectively carry out prescribed burns to achieve desired levels of burn coverage in Eucalyptus forests. We sought to identify the key fuel-bed attributes influencing ignitability under marginal weather conditions. We recorded ignition successes and failures at 45 points within 5 operational prescribed burns and used the data to build logistic regression models to predict the probability of ignition as a function of fuel-bed attributes. Models were ranked using an information theoretic approach. The four highest ranked models explained 48–54% of the variance in ignitability. Surface fine-fuel moisture content (FFMC) and overall fuel hazard (i.e. fuel arrangement) were the strongest predictors of ignitability, occurring in all four highest ranking models. Both surface FFMC and overall fuel hazard were negatively related to ignition likelihood, contradicting a commonly assumed positive relationship between fuel hazard and flammability. Our field method to measure ignition success could be applied across more prescribed burns to develop operationally useful models of ignitability.
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/WF19061
Abstract: Field measurements of surface dead fine fuel moisture content (FFMC) are integral to wildfire management, but conventional measurement techniques are limited. Automated fuel sticks offer a potential solution, providing a standardised, continuous and real-time measure of fuel moisture. As such, they are used as an analogue for surface dead fine fuel but their performance in this context has not been widely evaluated. We assessed the ability of automated fuel sticks to predict surface dead FFMC across a range of forest types. We combined concurrent moisture measurements of the fuel stick and surface dead fine fuel from 27 sites (570 s les), representing nine broad forest fuel categories. We found a moderate linear relationship between surface dead FFMC and fuel stick moisture for all data combined (R2=0.54), with fuel stick moisture averaging 3-fold lower than surface dead FFMC. Relationships were typically stronger for in idual forest fuel categories (median R2=0.70 range=0.55–0.87), suggesting the sticks require fuel-specific calibration for use as an analogue of surface dead fine fuel. Future research could identify fuel properties that will enable more generalised calibration functions.
Publisher: Wiley
Date: 10-12-2021
Publisher: MDPI AG
Date: 06-04-2018
DOI: 10.3390/F9040189
Publisher: MDPI AG
Date: 03-06-2022
DOI: 10.3390/FIRE5030076
Abstract: Mechanical mastication is a fuel management strategy that modifies vegetation structure to reduce the impact of wildfire. Although past research has quantified immediate changes to fuel post-mastication, few studies consider longer-term fuel trajectories and climatic drivers of this change. Our study sought to quantify changes to fuel loads and structure over time following mastication and as a function of landscape aridity. Measurements were made at 63 sites in Victoria, Australia. All sites had been masticated within the previous 9 years to remove over-abundant shrubs and small trees. We used generalised additive models to explore trends over time and along an aridity gradient. Surface fuel loads were highest immediately post-mastication and in the most arid sites. The surface fine fuel load declined over time, whereas the surface coarse fuel load remained high these trends occurred irrespective of landscape aridity. Standing fuel (understorey and midstorey vegetation) regenerated consistently, but shrub cover was still substantially low at 9 years post-mastication. Fire managers need to consider the trade-off between a persistently higher surface coarse fuel load and reduced shrub cover to evaluate the efficacy of mastication for fuel management. Coarse fuel may increase soil heating and smoke emissions, but less shrub cover will likely moderate fire behaviour.
Publisher: Elsevier BV
Date: 09-2022
Publisher: Springer International Publishing
Date: 29-07-2023
Publisher: Public Library of Science (PLoS)
Date: 26-08-2019
Publisher: Elsevier BV
Date: 04-2021
Publisher: Springer Science and Business Media LLC
Date: 11-06-2021
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/WF19199
Abstract: Fire management agencies use fire behaviour simulation tools to predict the potential spread of a fire in both risk planning and operationally during wildfires. These models are generally based on underlying empirical or quasi-empirical relations and rarely are uncertainties considered. Little attention has been given to the quality of the input data used during operational fire predictions. We examined the extent to which error in weather forecasts can affect fire simulation results. The study was conducted using data representing the State of Victoria in south-eastern Australia, including grassland and forest conditions. Two fire simulator software packages were used to compare fire growth under observed and forecast weather. We found that error in the weather forecast data significantly altered the predicted size and location of fires. Large errors in wind speed and temperature resulted in an overprediction of fire size, whereas large errors in wind direction resulted in an increased spatial error in the fire’s location. As the fire weather intensified, fire predictions using forecast weather under predicted fire size, potentially resulting in greater risks to the community. These results highlight the importance of on-ground intelligence during wildfires and the use of ensembles to improve operational fire predictions.
Publisher: Wiley
Date: 05-2018
DOI: 10.1002/ECS2.2211
Abstract: There are multiple pathways for vegetation to change following disturbances. Understanding those post‐disturbance pathways is critical for managing wildfire risk since vegetation is fuel in a wildfire context. Across forest systems, there is considerable debate about disturbance‐related changes to fuels and flammability. This study investigated post‐disturbance fuel trajectories following three disturbance types—high severity wildfire, low severity wildfire, and clear‐fell logging. Fuels were measured in a chrono‐sequence of 141 sites in Mountain Ash ( Eucalyptus regnans )‐dominated wet sclerophyll forest in southeastern Australia, a particularly contentious forest system. Wildfires are an important part of the lifecycle of these forests, but too frequent fire can threaten post‐fire regeneration. Large wildfires (in 2009, 1983 and 1939) and ongoing public and scientific debate over clear‐fell logging highlight the need to better understand post‐disturbance trajectories for fuel and flammability in wet sclerophyll forests. We used empirical data to test 10, sometimes contradictory, hypotheses from the scientific literature regarding post‐disturbance pathways for fuel following wildfire and logging. Only five hypotheses were supported with surface fine fuels, fuel hazard, species composition, and vertical structure driving overall differences in post‐disturbance fuel trajectories. The implications for flammability remain uncertain because the independent and interactive effects of many fuel components on overall flammability remain unquantified. Importantly, we found there were always high quantities of fuel, irrespective of disturbance history, which demonstrates that fire occurrence is not fuel‐limited in wet sclerophyll forests. Under conditions of abundant fuel, fuel moisture could become critical to fire occurrence. Therefore, forest management should prioritize efforts to quantify not only the importance of in idual fuel components to flammability but also fuel moisture dynamics in wet sclerophyll forests. As the climate (and fuels) becomes drier under climate change, it will be a major challenge to manage fire regimes in these highly valued forests.
Publisher: Springer International Publishing
Date: 29-07-2023
Publisher: American Geophysical Union (AGU)
Date: 07-2016
DOI: 10.1002/2016WR018998
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/WF16146
Abstract: Messmate stringybark is common in forests across south-eastern Australia. The bark of these trees is persistent and produces firebrands that contribute to house loss and the difficulty of fire suppression during wildfires. The trees typically survive fire with the amount of bark depleted. We compared two common methods to assess messmate bark fuels: (1) field-based hazard assessment, and (2) desk-based assessment using mapped time since fire. Our measurements included space-for-time field surveys and laboratory flammability tests. Although several physical properties of bark could be approximated from both assessment methods, some bark properties important to flammability were not captured. Ignitability was found to be dependent on the amount of char on bark fragments and could be predicted by the site assessment methods, whereas sustainability was dependent on bark fragment dimensions and could not be predicted by current methods. Bark fragment properties were found to be partially a function of tree size. Overall, these findings indicate that current bark assessment methods do not capture all the key bark properties that contribute to messmate bark’s flammability. Further research is warranted to improve bark assessment methods so they better reflect bark’s contribution to fire behaviour.
Publisher: MDPI AG
Date: 10-01-2023
DOI: 10.3390/FIRE6010024
Abstract: Understanding the conditions when litter beds will ignite from firebrands is critical for predicting spot fire occurrence. Such research is either field- or laboratory-based, with limited analysis to compare the approaches. We examined the ability of a laboratory method to represent field-scale ignitability. The laboratory method involved collecting litter-bed s les concurrently with the field experiments and then reconstructing and burning the litter-bed s les in the laboratory. We measured the number of successful and sustained ignitions in the laboratory (n = 5) and field (n = 30 attempts). The laboratory and field results were more similar for successful (bias = 0.05) than sustained ignitions (bias = 0.08). Wind, fuel structure (in the field) and near-surface fuel moisture influenced the differences between the methods. Our study highlights the value in conducting simultaneous laboratory and field experiments to understand the scalability of laboratory studies. For our ignitability method, our results suggest that small-scale laboratory experiments could be an effective substitute for field experiments in forests where litter beds are the dominant fuel layer and where the cover of the near-surface fuel is low.
Publisher: Springer Science and Business Media LLC
Date: 24-06-2020
Publisher: Wiley
Date: 12-2019
DOI: 10.1111/ECOG.04714
Publisher: CSIRO Publishing
Date: 19-05-2021
DOI: 10.1071/WF20157
Abstract: Mechanical mastication is growing in popularity as a wildfire mitigation technique. Yet few studies quantify its effects on fire behaviour. Such information is needed by fire managers to evaluate its efficacy. Our aim was to develop an understanding of how mastication alters flaming and smouldering durations and the longevity of any effects. Flaming and smouldering duration are important determinants of soil heating and smoke emissions. We used a paired s ling design, collecting litter bed (hereafter surface fuel) s les from 15 sites with masticated and untreated vegetation in shrub-encroached Eucalyptus woodlands. We measured a range of fuel bed properties and then burnt the s les in the laboratory. Average smouldering durations increased 88% from 25 to 47 min in untreated v. masticated fuel flaming durations increased 100% from 6 to 12 min. These changes were attributable to higher fine and coarse fuel loads in the masticated fuel bed. However, fine and coarse fuel load declined significantly over 4 years, meaning the effects of mastication on combustion duration are likely to be short-lived. Despite being a laboratory study, the results assist with evaluating mastication as a fuel treatment by demonstrating the potential magnitude of changes to flaming and smouldering duration.
Location: No location found
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