School of Agriculture, Food and Ecosystem Sciences - Research Publications
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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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ItemEnvironmental factors associated with the abundance of forest wiregrass (Tetrarrhena juncea), a flammable understorey grass in productive forests(CSIRO PUBLISHING, 2020-05-07)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.
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ItemEstimation of surface dead fine fuel moisture using automated fuel moisture sticks across a range of forests worldwide(CSIRO Publishing, 2020-02-07)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 samples), 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 individual 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.
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ItemFrequency of Dynamic Fire Behaviours in Australian Forest Environments(MDPI, 2020-03)Wildfires can result in significant social, environmental and economic losses. Fires in which dynamic fire behaviours (DFBs) occur contribute disproportionately to damage statistics. Little quantitative data on the frequency at which DFBs occur exists. To address this problem, we conducted a structured survey using staff from fire and land management agencies in Australia regarding their experiences with DFBs. Staff were asked which, if any, DFBs were observed within fires greater than 1000 ha from the period 2006–2016 that they had experience with. They were also asked about the nature of evidence to support these observations. One hundred thirteen fires were identified. Eighty of them had between one and seven DFBs with 73% (58 fires) having multiple types of DFBs. Most DFBs could commonly be identified through direct data, suggesting an empirical analysis of these phenomena should be possible. Spotting, crown fires and pyro-convective events were the most common DFBs (66%); when combined with eruptive fires and conflagrations, these DFBs comprise 89% of all cases with DFBs. Further research should be focused on these DFBs due to their high frequencies and the fact that quantitative data are likely to be available.
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ItemImproving Fire Behaviour Data Obtained from Wildfires(MDPI, 2018-02)Organisations that manage wildfires are expected to deliver scientifically defensible decisions. However, the limited availability of high quality data restricts the rate at which research can advance. The nature of wildfires contributes to this: they are infrequent, complex events, occur with limited notice and are of relatively short duration. Some information is typically collected during wildfires, however, it is often of limited quantity and may not be of an appropriate standard for research. Here we argue for a minimum standard of data collection from every wildfire event to enhance the advancement of fire behaviour research and make research findings more internationally relevant. First, we analyse the information routinely collected during fire events across Australia. Secondly, we review research methodologies that may be able to supplement existing data collection. Based on the results of these surveys, we develop a recommended list of variables for routine collection during wildfires. In a research field typified by scarce data, improved data collection standards and methodologies will enhance information quality and allow the advancement in the development of quality science.
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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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ItemNo Preview AvailableChanges in soil moisture drive soil methane uptake along a fire regeneration chronosequence in a eucalypt forest landscape(WILEY-BLACKWELL, 2015-11)Disturbance associated with severe wildfires (WF) and WF simulating harvest operations can potentially alter soil methane (CH4 ) oxidation in well-aerated forest soils due to the effect on soil properties linked to diffusivity, methanotrophic activity or changes in methanotrophic bacterial community structure. However, changes in soil CH4 flux related to such disturbances are still rarely studied even though WF frequency is predicted to increase as a consequence of global climate change. We measured in-situ soil-atmosphere CH4 exchange along a wet sclerophyll eucalypt forest regeneration chronosequence in Tasmania, Australia, where the time since the last severe fire or harvesting disturbance ranged from 9 to >200 years. On all sampling occasions, mean CH4 uptake increased from most recently disturbed sites (9 year) to sites at stand 'maturity' (44 and 76 years). In stands >76 years since disturbance, we observed a decrease in soil CH4 uptake. A similar age dependency of potential CH4 oxidation for three soil layers (0.0-0.05, 0.05-0.10, 0.10-0.15 m) could be observed on incubated soils under controlled laboratory conditions. The differences in soil CH4 uptake between forest stands of different age were predominantly driven by differences in soil moisture status, which affected the diffusion of atmospheric CH4 into the soil. The observed soil moisture pattern was likely driven by changes in interception or evapotranspiration with forest age, which have been well described for similar eucalypt forest systems in south-eastern Australia. Our results imply that there is a large amount of variability in CH4 uptake at a landscape scale that can be attributed to stand age and soil moisture differences. An increase in severe WF frequency in response to climate change could potentially increase overall forest soil CH4 sinks.
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ItemRecognising fuzzy vegetation pattern: the spatial prediction of floristically defined fuzzy communities using species distribution modelling methods(WILEY, 2014-03)QUESTION: Plant communities are not necessarily spatially exclusive; a point in space can exhibit properties of multiple communities. Such variation can be described using floristically defined ‘fuzzy’ units, however these may not be easily delineated using standard remote sensing methods. Is there value in considering communities as fuzzy? Can species distribution modelling methods be used to represent fuzzy communities spatially? LOCATION: Western Victoria, Australia. METHODS: Fuzzy communities were objectively identified from vegetation census quadrats with a cluster analysis of ordinated species data. Boosted regression trees were used to create models that defined relationships between the sampled communities and environmental predictor variables. These were applied to the mapped predictors to create maps of estimated fuzzy community membership for the entire study area. RESULTS: Four separate fuzzy communities were identified from the sampled vegetation data. Models were created for each community and these were effectively used to generate maps of fuzzy community membership. Individual fuzzy community maps illustrated vegetation variation that could not be discerned on a discretely classified map. CONCLUSIONS: Fuzzy communities were found to represent a greater proportion of species variation than discretely classified units. Species distribution modelling methods were effective in creating independent spatial maps of each floristically defined fuzzy community; however the interpretation of these maps is more complex than with a single discrete community map.