Format: ORAL

Thomsen. A1, Keith. D1, Lemmon. J2, Allen. V2, Ooi. M1

1 Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, UNSW Sydney NSW, 2052, Australia 2 Office of Climate Change, Energy, the Environment and Water, 84 Crown St, Wollongong, NSW 2500

Shifts in the fire regime caused by climatic and anthropogenic influences mean that we are currently experiencing more frequent and severe fires at larger scales. Fire is a dominant disturbance in Eucalyptus forests in temperate Australia. Wet sclerophyll forests are often bordered by dry sclerophyll and/or rainforests and changes to the fire regime can shift these borders by allowing more dry sclerophyll or rainforest species to disperse into current wet sclerophyll forests. The Black summer fires of 2019-20 saw around 50% of the threatened Upland Basalt Eucalypt forests of the Sydney Basin Bioregion ecological community burnt, with some areas experiencing extreme severity fire. Much of this ecological community is often disturbed and fragmented, making it potentially less resilient to disturbance changes, such as extreme fire events. To assess how these wet sclerophyll forests respond to different fire severities, we surveyed areas impacted by the 2019-20 Black Summer fires one-year later. We quantified the mortality rates of dominant tree species including Acacia melanoxylon, Eucalyptus blaxlandii, Eucalyptus cypellocarpa and Eucalyptus radiata, and compared how the dominance of different functional groups varied across the fire severity gradient. We have uncovered evidence that rainforest trees within wet sclerophyll forests may be highly susceptible to extreme fire events especially and at sites previously subjected to frequent fires. This study highlights the importance of understanding how severity of fire impacts wet sclerophyll forests and can inform management decision on conserving threatened ecological communities.