ARI research on the life-cycle of Banksia spinulosa var cunninghamii is being used by fire managers as a case study of how to maintain plant diversity in forests when applying fuel reduction burns. This species typifies plants that decline if burnt too often, because they don’t 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. It is therefore important to determine the minimum time between fires needed to retain these types of species.
Seed production (number of cones per live adult plant) and seedling recruitment (number of seedlings per dead adult plant) in response to fire were studied at two Banksia populations; just east of Melbourne, and in far east Gippsland. Results indicate that fire intervals of at least 15 years enable Banksia populations to maintain an adequate seed source. Where fire intervals were lower than this plants produced very little seed and populations may decline. Very low numbers of seedlings were recorded at almost all sites, and observations suggest that a fire hot enough to burn Banksia canopies rather than only scorch them may better trigger seed release and subsequent germination. Further research is needed to determine optimal fire severity for seedling recruitment.
The findings on fire intervals for seed production are being applied in regional fire planning by DELWP and Parks Victoria to support Victorian Government fire policy. Funds and in-kind support were provided by DELWP's Forest, Fire and Regions Group, and Parks Victoria.