Fire regimes for Banksias

ARI research on the life-cycle of Banksia spinulosa var cunninghamii (Hairpin Banksia) is helping maintain plant diversity in forests when applying fuel reduction burns and assessing recovery after bushfires.

Hairpin Banksia populations are vulnerable to decline if burnt too often, because plants do not resprout after fire, take a long time before producing seed, and have no soil seed banks. The interval between fires needs to be long enough for plants to mature and produce sufficient seed, and for enough seedlings to survive to replace the parent populations.

Investigations into seed production and seedling recruitment in response to fire were undertaken between 2014 and 2017, to the east of Melbourne and in East Gippsland. Results showed that:

• In populations less than ten years old, only about 40% of plants had any seed cones.
• Maximum canopy seed bank was reached between 15 and 30 years post-fire.
• Very low numbers of seedlings (~ one seedling per adult plant) were recorded at sites 18 months after fuel reduction burns.
• Differences in seedling recruitment are likely to be influenced by rainfall following fires.

During bushfires in 2019 and 2020, a large proportion of Hairpin Banksia populations in East Gippsland and Bunyip State Park were burnt. Post-fire surveys found that:

• Seedling recruitment occurred for around 90% of plants that were ten years or older, but almost no seedlings were recorded for plants that were five years or younger.
• Recruitment was also low at sites in East Gippsland that had experienced high severity fire, because seed cones were destroyed by extreme heat.