Regeneration by three species of Banksia on the south coast of Western Australia in relation to fire interval

Abstract

The regeneration strategies of three Banksia species in relation to fire were studied over 20 years in a mediterranean heathland-shrubland on the south coast of Western Australia. Banksia baueri and B. nutans are both bushes 1–2 m high, while B. baxteri is a shrub 4 m high. All three species regenerated only from seed released from the canopy seed bank after fire. They did not start to flower until 6 years after fire and seed set took even longer. Differences between the species in age-related intensity of flowering were related to the rate at which each species accumulated seed in the canopy. Even plants over 40 years old were still increasing their overall canopy seed bank or replacing seeds that had been released or were no longer viable. The vegetation studied appeared to be little affected by humans historically and to have burnt only at intervals of 30–60 years or more. Consequently, although all three species needed fire to regenerate, management of fire regimes needs to allow adequate intervals between fires for the replacement of their canopy seed banks. Indeed, all three Banksia species studied were extinguished from one area burnt twice at an interval of 9 years. Models developed with Banksia species from the northern sand plains of Western Australia, where fires appear more frequent, may need modification to be applicable to all south-coastal species.