School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemPlant traits linked to field-scale flammability metrics in prescribed burns in Eucalyptus forest (vol 14, e0221403, 2019)(PUBLIC LIBRARY SCIENCE, 2019-09-30)[This corrects the article DOI: 10.1371/journal.pone.0221403.].
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ItemFire planning for multispecies conservation: Integrating growth stage and fire severity(Elsevier, 2018-05-01)Setting suitable conservation targets is an important part of ecological fire planning. Growth-stage optimisation (GSO) determines the relative proportions of post-fire growth stages (categorical representations of time since fire) that maximise species diversity, and is a useful method for determining such targets. Optimisation methods can accommodate various predictor variables, but to date have only been applied using post-fire growth stages as the primary landscape variable. However, other aspects of fire regimes such as severity may influence species diversity but have not yet been considered in determining conservation targets in fire planning. Here we use a space-for-time substitution to address two objectives, 1. To determine the effects of growth stage and fire severity on plant and vertebrate species’ occurrence, and 2. To determine the optimal mix of growth stages and fire severities for sustaining the diversity of these groups. We used the tall wet forests of southeast Australia as the focal system because fire severity is expected to create distinct successional pathways and influence species’ responses. We found that growth stage predicted the occurrence of many species, and severity of the most recent fire was an important factor over and above growth stage for a small subset of species. The optimal distribution of growth stages for both plants and animals included a substantial proportion of young forest, however when fire severity was considered, areas burned at low severity were most important in driving the diversity of both groups. Growth stage is a good surrogate for developing conservation targets in tall wet forests, however growth stage alone does not capture the full range of species’ fire responses. More complex versions of growth stage optimisation that accommodate multiple fire-regime variables need to be explored to yield ecologically meaningful conservation goals.
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ItemScale-dependency of effective hydraulic conductivity on fire-affected hillslopes(AMER GEOPHYSICAL UNION, 2016-07)Abstract Effective hydraulic conductivity (Ke) for Hortonian overland flow modeling has been defined as a function of rainfall intensity and runon infiltration assuming a distribution of saturated hydraulic conductivities (Ks). But surface boundary condition during infiltration and its interactions with the distribution of Ks are not well represented in models. As a result, the mean value of the Ks distribution ( ), which is the central parameter for Ke, varies between scales. Here we quantify this discrepancy with a large infiltration data set comprising four different methods and scales from fire‐affected hillslopes in SE Australia using a relatively simple yet widely used conceptual model of Ke. Ponded disk (0.002 m2) and ring infiltrometers (0.07 m2) were used at the small scales and rainfall simulations (3 m2) and small catchments (ca 3000 m2) at the larger scales. We compared between methods measured at the same time and place. Disk and ring infiltrometer measurements had on average 4.8 times higher values of than rainfall simulations and catchment‐scale estimates. Furthermore, the distribution of Ks was not clearly log‐normal and scale‐independent, as supposed in the conceptual model. In our interpretation, water repellency and preferential flow paths increase the variance of the measured distribution of Ks and bias ponding toward areas of very low Ks during rainfall simulations and small catchment runoff events while areas with high preferential flow capacity remain water supply‐limited more than the conceptual model of Ke predicts. The study highlights problems in the current theory of scaling runoff generation.
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ItemFlammability at field-scales: conducting research in prescribed burns(UNIV COIMBRA, 2018)To better understand the role of plant flammability in driving landscape-scale fire behaviour and fire regimes, field-scale flammability research needs to occur. Yet, experimental fires are costly to implement and research within wildfires is both logistically challenging and potentially dangerous. As an alternative, we propose that operational prescribed burns undertaken for land management purposes should be exploited for flammability research.. In some parts of the world, large areas are burnt annually, providing extensive opportunities for research. In this paper we describe three broad methods that can be used to measure different facets of flammability in prescribed burns. We compare the strengths and potential limitations of each method before finally providing ten principles for conducting effective flammability research in prescribed burns. We conclude that operational prescribed burns are a largely untapped resource that could be used to better understand links between plant flammability and landscape-scale fire behaviour.
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ItemPlant traits linked to field-scale flammability metrics in prescribed burns in Eucalyptus forest(PUBLIC LIBRARY SCIENCE, 2019-08-26)Vegetation is a key determinant of wildfire behaviour at field scales as it functions as fuel. Past studies in the laboratory show that plant flammability, the ability of plants to ignite and maintain combustion, is a function of their traits. However, the way the traits of individual plants combine in a vegetation community to affect field flammability has received little attention. This study aims to bridge the gap between the laboratory and field by linking plant traits to metrics of field-scale flammability. Across three prescribed burns, in Eucalyptus dominated damp and dry forest, we measured pre-burn plant species abundance and postburn field flammability metrics (percentage area burnt, char and scorch height). For understory species with dominant cover-abundance, we measured nine traits that had been demonstrated to influence flammability in the laboratory. We used fourth-corner ordination to evaluate covariation between the plant traits, species abundance and flammability. We found that several traits covaried at the species level. In some instances, these traits (e.g. specific leaf area and bulk density) could have cumulative effects on the flammability of a species while in other instances (e.g. moisture and specific leaf area) they may have counteractive effects, assuming trait effects on flammability are akin to previous research. At field scales, species with similar traits tended to co-occur, suggesting that the effects of individual traits accumulate within a plant community. Fourth-corner analyses found the traitfield flammability relationship to be statistically significant. Traits significantly associated with increasing field flammability metrics were: bulk density (negatively associated) and hydrocarbon quantity, specific leaf area and surface area to volume ratio (all positively associated). Our study demonstrates that some traits known to influence flammability in the laboratory can be associated with field-scale flammability metrics. Further research is needed to isolate the contributions of individual traits to understand how species composition drives forest flammability.
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ItemManagement of firebrand potential through the candling of bark fuel(UNIV COIMBRA, 2018)Aerially suspended fuels play an important role in forest fire behaviour. They can act as a ladder to flames, increasing the potential for crownfire, and can ignite and act as firebrands. When large accumulations of these fuels are present, wildfires may spread more rapidly, be more difficult to suppress and be more likely to impact assets such as houses. However, as these fuels are suspended above the ground, their moisture status is predominantly a function of atmospheric humidity. As a result, bark and suspended fuels may become flammable at times when the remainder of the fuel bed is too wet to burn due to high soil moisture levels. This means that these fuels can be reduced by burning when conditions are unfavourable for prescribed burning using the practice candling. Candling is the deliberate ignition of bark and other dead fine ladder fuels under conditions where surface fires are unlikely to spread. We compared the number of days available for prescribed burning and candling for a locality in South Eastern Australia and found that in the period 2012 – 2016, candling could be undertaken for an average 124 days per year, 48 days more than the window available for prescribed burning (76 days). As each accumulation of aerial fuel must be individually lit during candling, the practice is labour intensive and inefficient over large areas relative to prescribed burning, so it is best used for targeted risk reduction such as near control lines or assets. However, it can be used to reduce risk with low chance of escape in locations where prescribed burning is difficult such as the Wildland Urban Interface. The practice is applied operationally in South Eastern Australia, however to date there has been limited research into its effects on wildfire spread and intensity. Given its suitability for strategic use near highly vulnerable assets, we believe further investigation into its utility is warranted.