@article {bnh-7795, title = {Experiments on the influence of spot fire and topography interaction on fire rate of spread}, journal = {PLOS ONE}, volume = {16}, year = {2021}, month = {01/2021}, abstract = {

Spotting is thought to increase wildfire rate of spread (ROS) and in some cases become the main mechanism for spread. The role of spotting in wildfire spread is controlled by many factors including fire intensity, number of and distance between spot fires, weather, fuel characteristics and topography. Through a set of 30 laboratory fire experiments on a 3 m x 4 m fuel bed, subject to air flow, we explored the influence of manually ignited spot fires (0, 1 or 2), the presence or absence of a model hill and their interaction on combined fire ROS (i.e. ROS incorporating main fire and merged spot fires). During experiments conducted on a flat fuel bed, spot fires (whether 1 or 2) had only a small influence on combined ROS. Slowest combined ROS was recorded when a hill was present and no spot fires were ignited, because the fires crept very slowly downslope and downwind of the hill. This was up to, depending on measurement interval, 5 times slower than ROS in the flat fuel bed experiments. However, ignition of 1 or 2 spot fires (with hill present) greatly increased combined ROS to similar levels as those recorded in the flat fuel bed experiments (depending on spread interval). The effect was strongest on the head fire, where spot fires merged directly with the main fire, but significant increases in off-centre ROS were also detected. Our findings suggest that under certain topographic conditions, spot fires can allow a fire to overcome the low spread potential of downslopes. Current models may underestimate wildfire ROS and fire arrival time in hilly terrain if the influence of spot fires on ROS is not incorporated into predictions.

}, keywords = {air flow, analysis of variance, Bushfire, combustion, fire research, fire suppression technology, fuels, rotors}, doi = {https://doi.org/10.1371/journal.pone.0245132}, url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0245132}, author = {Michael Storey and Owen Price and M. Almeida and Carlos Ribeiro and Ross Bradstock and Jason J. Sharples} } @mastersthesis {bnh-8091, title = {How do wet forests burn? : Fuels and fire danger in the world{\textquoteright}s tallest flowering forest}, volume = {Doctor of Philosophy}, year = {2020}, month = {02/2020}, pages = {222}, school = {University of Tasmania}, address = {Hobart}, abstract = {

Wildfire is possibly the most widespread natural disturbance globally, as its spatial and temporal patterns shape vegetation assemblages throughout the world. This is especially true in Australia, where the dominant trees, Eucalyptus spp., are among the most well-adapted to fire on the planet. To protect communities in such a fire-prone landscape, we need to be able to predict fire behaviour and manage fuels in a fashion that reduces risk. But to do this effectively, we must understand the natural fire regimes that occur in Australian ecosystems. One Australian ecosystem for which fire regimes are poorly understood is the tall wet Eucalyptus forest (TWEF). These globally unique forests support a mix of flammable and fire-sensitive vegetation and are among the world{\textquoteright}s most carbon-dense forests, so understanding their flammability is critical.

This thesis attempts to describe the fire regime TWEF. It does so in a fashion that can inform fuels management and fire behaviour prediction, with a particular focus on the island of Tasmania. First, I used fire behaviour model simulations to analyse the effectiveness of fuel treatment on fire behaviour in different Tasmanian vegetation, which allowed me to contextualise fire risk across the island{\textquoteright}s diverse vegetation types. I then described the fire regime, namely the expected frequency and severity of wildfires, of TWEF. I did this using a combination of fuels, microclimate, and weather data, along with fire behaviour modelling, to estimate potential fire severities in these forests. I first investigated what drives fire severity across a continental-scale macroecological gradient of forests in an {\textquoteleft}early-mature{\textquoteright} successional stage. However, flammability of older forests can be different from that of younger forests, so I investigated how the flammability of TWEF changes as a stand develops from regrowth to old-growth forest. For the latter exercise I focused, on Tasmanian TWEF.

Fire behaviour model simulations indicated that an impractical extent of landscape-scale prescribed burning would be needed for the treatment to be effective, and that this is especially true for TWEF. The results also suggested that Tasmanian TWEF are capable of sustaining among the most intense fires on the planet. I suggest that prescribed burning needs to be conducted at local, targeted scales, and that alternatives to prescribed burning need to be investigated for Tasmanian TWEF. Analysis of the continent-wide dataset of fuels and microclimate in early-mature TWEF indicated both low-and high-severity fires play an important role, but that high-severity fire is much more likely in TWEF in the hotter and drier regions of the continent. Further, similar analysis of a chronosequence of TWEF stands in Tasmania indicated that high-severity fires become more likely in younger TWEF. Importantly, the results highlighted that the TWEF understorey (or elevated fuel layer) is the most important fuel layer from a fire danger perspective. Hence, I suggest that management needs to mimic mixed-severity fires to maintain the structural heterogeneity and microclimate that makes these forests fire resistant.

Results from fire behaviour model simulations and from measuring fire severity in eight burnt field sites also indicated that current operational models over-predict flame height and fireline intensity in TWEF, likely due to an over-simplistic representation of forest structure. As a result, I performed a detailed review of the three major current operational fire behaviour models, along with a next-generation physics-based model, and documented their shortcomings. I then investigated how applicable these different models were in TWEF. Despite its importance, the live understorey is composed of many fire-sensitive species whose flammability is poorly understood. Hence, I propose that small-scale burning studies combined with physical simulation of wildfire are needed to quantify flammability and fire behaviour in forests composed of such species.

}, keywords = {burn, fire danger, flowering forest, fuels, wet forests}, url = {https://eprints.utas.edu.au/34888/}, author = {Furlaud, James M.} }