Fires in rainforests: Quantifying litter bed flammability of cool temperate rainforests in eastern Australia

Rainforests are usually too wet to burn, acting as natural barriers to fire spread and as refuges for biodiversity. However, climate change is increasing the risk of fire incursion into rainforests. Our capacity to manage these impacts is hindered by limited research on rainforest flammability.

Fallen leaf and litter bed samples were collected from cool temperate rainforest and eucalypt forest in Willi Willi and Werrikimbe National Parks, New South Wales, Australia. Litter bed flammability of 13 common temperate rainforest species was measured in the laboratory. The flammability of rainforest litter beds and fire-prone eucalypt forest litter beds were compared for 0.07 m² and 7.2 m² beds. We also examined links between flammability and key structural and chemical leaf traits.

Rainforest species varied in their litter bed flammability; 64% of the species had lower flammability than litter comprising eucalypt leaves, which typically occur in more fire-prone environments. Species with smaller leaves and less leaf cellulose were associated with lower flammability. Rainforest litter beds had slower flame spread rates, smaller flames, and less material consumed compared to eucalypt litter beds.

Fire characteristics in cool temperate rainforests will vary depending on the species composition of the litter bed, which depends on the litterfall composition of the rainforest stand. This study provides key insights into litter bed flammability in cool temperate rainforests in Australia, which will inform decisions on management of wildfires.