Bioclimatic drivers of fire severity across the Australian geographical range of giantEucalyptusforests

Abstract

1. The relationships between productivity, fire frequency and fire severity shape the distribution of plant communities globally. Dry forests are expected to burn frequently and wet forests to burn infrequently. However, the effect of productivity on intensity and severity of wildfire is less consistent and poorly understood.One productive ecosystem where this is especially true is the Australian tall wet Eucalyptus-dominated forest (TWEF), which spans wet areas across the continent.This study aims to characterise how climate shapes the likelihood of low-and high-severity wildfire across Australian TWEF.2. We performed a continental-scale analysis of fuels in 48 permanent plots in earlymature stage TWEF across four climate regions in Australia. We estimated fuel loads and measured understorey microclimate. We then obtained historical fireweather observations from nearby meteorological stations and used fuel moisture and fire behaviour equations to predict the historical frequency with which TWEF could burn and what fire severities were expected. We investigated how this varies across the different TWEF climate regions. Lastly, we validated our approach by remeasuring eight plots that burned unexpectedly post-measurement.3. We found that surface fuels in cooler, moister regions were available to burn 1-16 days per year historically, with only low-severity, surface fire possible most of these days: high-severity fire was only possible under rare, extreme fire-weather conditions. However, in warmer, drier regions, fuels were available to burn 23-35 days annually, and high-severity fire was more likely than low-severity fire.Validation showed that we slightly overestimated flame heights, inflating highseverity risk estimates. If we used elevated fuel loads to predict flame heights, however, high-severity fire was more likely than low-severity fire everywhere.Lastly, the likelihood of high-severity fire increased with increasing temperature and worsening fire weather. Synthesis.Fire activity in early-mature TWEF is limited by climatic constraints on fire weather and availability to burn, with high-severity fire more likely in warmer, drier regions than in cooler, wetter ones. This indicates a particularly worrisome vulnerability to climate change, given TWEF's diminished ability to recover from disturbance in a warmer world. The occurrence of both low-and high-severity fire means the fire regimes of TWEF are best described as mixed severity.

Global and Regional Trends and Drivers of Fire Under Climate Change

“…For example, the eucalyptus forests of Southeast Australia are particularly noted for their tolerance of fire, with flammable properties such as leaves with high surface area and volatile oil content (Bond & Keeley, 2005; Cawson & Duff, 2019; Crisp et al., 2011; Rodriguez‐Cubillo et al., 2020; Tumino et al., 2019). Eucalyptus species show various evolutionary strategies that protect them from mortality or allow their communities to re‐establish quickly following fire (Burton, Bennett, et al., 2021; Furlaud et al., 2021; Poulos et al., 2018; Rodriguez‐Cubillo et al., 2020). In our analysis, correlations between tree cover and BA were usually negative but this differed in the case of southeast Australia and in the Mediterranean climates of the Pacific US and the Iberian Peninsula, where weak positive correlations are seen between tree biomass and BA (Figure 8, Table 4).…”

Forest fire pattern and vulnerability mapping using deep learning in Nepal

“…We considered 19 bioclimatic variables that were identified as the contributing factors for forest fire in this study. These variables have been identified as the governing factors for the spread of forest fire in several parts of the world (Furlaud et al 2021;Singh and Zhu 2021;Makhaya et al 2022). These bioclimatic datasets were acquired from WorldClim's Global Climate Data website (http:// world clim.…”

Frequently Burnt Subtropical Eucalypt Forest Is More Resilient to Wildfire Than Rarely Burnt Forest

“…High-intensity fires promote abundant recruitment of some woody s pecies, especially wattles, other legumes and some rainforest trees (Morrison, 2002;Lewis & Debuse, 2012;Williams et al, 2012;Collins, 2020;Baker et al, 2022). The risk of high-severity fire increases with high elevated fuel loads (Furlaud et al, 2021). For example, in Warrumbungle National Park, the abundance of Acacia species increased four-fold after a high-intensity wildfire, with their density positively correlated with fire severity (Gordon et al, 2017;Palmer et al, 2018).…”