PhD Final Seminar: How do Wet Forests Burn?

Lecture Theatre 1 -- Rm 106
Life Sciences Building
College Road, Sandy Bay Campus
University of Tasmania
14 Feb 2020 4pm

The Fire Centre will be co-hosting the Final Seminar of one of it’s PhD students. James Furlaud will talk about fuels and fire danger in wet Eucalypt forest. The event will be held in Lecture Theatre 1 of the Lifes Sciences Building on the UTAS Sandy Bay Campus.

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’s most carbon-dense forests, so understanding their flammability is critical.

I attempt to describe the fire regime TWEF. I 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’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 the fire regime across a continental-scale macroecological gradient of old-growth forests. However, flammability of old-growth 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 old-growth TWEF indicated that these forests support a mixed-severity fire regime, and that high-severity fires only occur in exceptional cases. 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 low-moderate severity fires to maintain the structure and microclimate that makes these forests fire resistant.

Results from fire behaviour model simulations and from measuring fire severity in four 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 elevated fuels. As a result, I performed a detailed review of the 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.

Biography

James Furlaud is a PhD Student at the University of Tasmania and the Fire Centre Research Hub. He is an ecologist with a statistics background. Over the past decade he’s spent most summers in the field studying forests around the world, and is now attempting to apply this field based experiential knowledge to mathematical modelling and statistical exercises. He’s passionate about natural ecological processes and how they can inform the way we interact with and manage the environment. Originally from New York City, a passion for the outdoors had led him away from the city, slowly heading west until He ended  up in Tasmania. He loves spending time in Tasmania’s bush, whether on foot or in a kayak.