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Fire risk and severity decline with stand development in Tasmanian giant Eucalyptus forest

Citation

Furlaud, JM and Prior, LD and Williamson, GJ and Bowman, DMJS, Fire risk and severity decline with stand development in Tasmanian giant Eucalyptus forest, Forest Ecology and Management, 502 Article 119724. ISSN 0378-1127 (2021) [Refereed Article]

Copyright Statement

Copyright 2021 Elsevier B.V. All rights reserved.

DOI: doi:10.1016/j.foreco.2021.119724

Abstract

Forest fire risk, and how it changes over time, has important influences on forest dynamics. Two common models describing how fire risk changes with stand development, known as flammability functions, are (a) the ‘moisture model’, where fire risk initially increases, then decreases, as a stand develops after a fire, and (b) the ‘Olson model’, where fire risk increases asymptotically as a function of time since previous fire. These two flammability functions have both been used to describe the world’s tallest angiosperm forest, the Australian tall wet Eucalyptus forest (TWEF). It is unclear, however, which function is more appropriate for TWEF, as there are little empirical data describing fuels and microclimate, two important influences on fire risk and potential severity, across the long lifespan of these forests. Accordingly, we use a chronosequence of TWEF stands in southeast Tasmania, Australia, to see how fuels, microclimate, and resulting fire risk and potential fire severity changed amongst four stand-development stages ranging from regrowth to old forests. We measured fuel loads, understorey microclimate, and forest physiognomy. We then used these data with historical fire weather data and fire behaviour models to estimate how often low- and high-severity fire was possible historically. We also investigated if the severity of the previous disturbance influenced the likelihood of a subsequent high-severity fire. We found that, while fuel loads remained unchanged across the chronosequence, later development stages had a significantly moister understorey, an increased abundance of rainforest trees, and more vertically discontinuous fuels. These factors resulted in a significantly reduced fire risk, with high-severity fire much more likely in the early stages. Further, we found that stands that had been initiated by stand-replacing fire were more susceptible to subsequent high-severity fire than those that experienced non stand-replacing fire, due to a lack of a remaining mature canopy. We concluded that, unlike most other fire-dependent ecosystems where the Olson curve is an appropriate model, the flammability function in TWEF is best described by the moisture model. Our results indicate that TWEF is vulnerable to a ‘landscape trap’ effect, where intensive disturbance creates large areas of regrowth stands with increased risk of high-severity fire, which increases the likelihood of landscape-wide, demographic collapse. We suggest that fire and forest management incorporate techniques mimicking low-severity disturbances to create more resilient landscapes.

Item Details

Item Type:Refereed Article
Keywords:forest, fire, eucalyptus, risk, chronosequence, fire behaviour, fire severity, flammability function, forest dynamics, fuel loads, moisture model
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Forestry sciences
Research Field:Forestry fire management
Objective Division:Plant Production and Plant Primary Products
Objective Group:Forestry
Objective Field:Native forests
UTAS Author:Furlaud, JM (Mr James Furlaud)
UTAS Author:Prior, LD (Dr Lynda Prior)
UTAS Author:Williamson, GJ (Dr Grant Williamson)
UTAS Author:Bowman, DMJS (Professor David Bowman)
ID Code:146919
Year Published:2021
Deposited By:Plant Science
Deposited On:2021-10-04
Last Modified:2021-11-24
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