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

Abstract

Open eucalypt forests with a grassy understorey are becoming rare in the volcanic landscapes on the Queensland-New South Wales border, as woody plants thicken with the cessation of regular planned burning. Whether previous planned burning reduced the impact of the 2019 unplanned wildfires on forest condition is debated. We evaluated the role of planned burning on the condition of a subtropical eucalypt forest following a wildfire in 2019. Two years after a wildfire at Mt Lindesay, a section of forest that had been frequently burnt was in better condition than adjacent rarely burnt forest. Specifically, there was significantly greater cover of kangaroo grass and a lower density of tree saplings in frequently burnt forest. The canopy of rarely burnt forest showed more signs of dieback. The pattern of healthier eucalypt forest with frequent burning was observed at other South East Queensland sites, Mt Gillies and Spicer's Gap. These observations suggest long-term frequent burning under mild conditions with good soil moisture maintains grassy eucalypt forest that is resilient to occasional intense wildfires during drought, such as seen in late 2019.

Kangaroo grass is a keystone species for ecological fire management

“…Kangaroo grass ( Themeda triandra ) dominates many grassy ecosystems across Australia where rainfall exceeds 500 mm per annum, though its abundance has diminished considerably in recent decades (Chevis et al, 2022; Lunt & Morgan, 2002; Williams et al, 2020). Regular fire maintains kangaroo grass abundance (Morgan & Lunt, 1999; Morris & Watson, 2020; Prober et al, 2007).…”

“…Current fire regime guidelines often do not adequately consider the ecology of kangaroo grass and its role in managing fire regimes (Baker & Catterall, 2015; Stone et al, 2022; Watson & Morris, 2020). This risks the loss of important grassy ecosystems due to overly long fire intervals or high‐intensity fires in dry conditions (Baker et al, 2020; Lewis et al, 2012; Williams et al, 2020).…”