Fire temperatures and follicle-opening requirements in 10 Banksia species

Temperature requirements for follicle rupture were assessed in 10 Banksia species from south-western Australia. Species examined varied in degree of serotiny, persistence of dead florets, height, follicle size and number, and dependence on seed for regeneration. When treated for 2 min at temperatures over the range 100–500°C, follicles of some species ruptured at quite low temperatures (e.g. Banksia tricuspis with 50% opening at 145°C). Others required substantially higher temperatures (e.g. Banksia hookeriana with 50% opening at 390°C). There was a significant correlation between temperature requirements for follicle rupture and persistence of the highly combustible florets. However, there was no overall correlation between degree of serotiny and temperature requirements, nor with the other biological attributes assessed. Cone temperatures and follicle rupture in five co-occurring Banksia species were monitored for an experimental spring burn in Banksia- dominated shrubland. Temperatures recorded at follicle surfaces were higher than those needed for follicle rupture in the four species with persistent florets. Critical temperatures were rarely reached for the weakly serotinous Banksia menziesii which possesses bare cones and an open canopy