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.