Rainforest persistence and recruitment after Australia’s 2019–2020 fires in subtropical, temperate, dry and littoral rainforests

Abstract

Interactions between rainforest plants and fire occur when fires encroach into rainforest and when rainforest pioneers colonise fire-prone open forests. Although numerous studies show that many rainforest plants survive fire by resprouting and postfire seedling recruitment, data is lacking for several major Australian rainforest types. In this study, we examine fire-resilience traits among 228 taxa of woody rainforest plants in four rainforest classes (subtropical, warm temperate, dry and littoral rainforest) less than 1 year after being burnt in the extensive wildfires of 2019–2020. Among taxa with ≥ 5 records of complete crown scorch (126), resprouting occurred in 63% of taxa overall and 61% of late-successional taxa. Fire-cued seedling recruitment occurred in 62% of taxa overall and 48% of late-successional taxa. Surprisingly, species richness of woody plants increased 22% postfire due to high rates of persistence and emergence of new taxa into standing plant populations as seedlings. Stem density increased ∼400% postfire due to high rates of resprouting and reproduction through suckering and seedling recruitment, although there was a significant redistribution from medium to smaller stem size classes. Larger stems (>10 cm diameter at breast height) were not significantly reduced in rainforest stands. High resprouting rates in small rainforest plants (1 cm diameter at breast height, 1 m tall) suggests rapid attainment of resprouting capacity. Our findings demonstrate that most subtropical, dry, warm temperate and littoral rainforest plant taxa are resilient to rare fires, and suggest that rainforest plants that invade rarely-burnt open forests may quickly become resistant to removal by infrequent fires, with potential for increased populations through fire-enhanced seedling germination.

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

“…An overabundance of native saplings, especially wattles and eucalypts, is a recognised indicator of unhealthy subtropical eucalypt forests (Williams et al, 2020;Virkki et al, 2021). 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).…”

“…Large areas of eastern Australia were burnt in unplanned, high-intensity wildfires between August 2019 and February 2020 (Adams et al, 2020;Collins et al, 2021;Smith et al, 2021;Baker et al, 2022). High-intensity wildfires can damage the canopy and kill eucalypt trees which normally survive lower-intensity fires (Williams et al, 2020).…”

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“…An overabundance of native saplings, especially wattles and eucalypts, is a recognised indicator of unhealthy subtropical eucalypt forests (Williams et al, 2020;Virkki et al, 2021). 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).…”

Integrating soil microbial communities into fundamental ecology, conservation, and restoration: examples from Australia

“…This research will establish an important baseline understanding of Australian rainforest fungi and elucidate the effects of climate on fungal community composition. This information will be crucial to the future conservation and restoration of these unique ecosystems, especially with changing climate and fire frequencies (Baker et al, 2022). Australia appears to be a global hotspot of Serendipita mycorrhizal fungi with nine new species (of 22 species known world-wide) recently described from the continent (Crous et al, 2020(Crous et al, , 2022Oktalira et al, 2021).…”

“…2c). Extensive areas of rainforest were burnt within the Gondwana Rainforests of Australia during catastrophic wildfires in 2019–2020 (Nolan et al ., 2020; Baker et al ., 2022). Large parts of the rainforest were damaged as part of the 3.8 million ha of forest burnt in the state of New South Wales (Nolan et al ., 2020).…”