Variation in serotiny of three Banksia species along a climatic gradient

Abstract

AbstractThe degree of serotiny (i.e. the proportion of follicles remaining closed in each year's crop of cones since the last fire) was measured in Bank‐sia attenuata, B. menziesii and B. prionotes at five sites along a climatic gradient extending 500 km north of Perth, Western Australia. The decrease in annual rainfall and increase in average temperature along the gradient paralleled a decrease in plant height and an increase in the degree of serotiny of all species. Extreme serotiny was recorded in the scrub‐heath at the xeric end of the gradient whereas two species were essentially non‐serotinous in the low woodland at the most mesic site.It is concluded that degree of serotiny is related to the fire characteristics of the site which depend on plant height. In xeric scrub‐heath, the entire canopies of the Banksia spp. are consumed by fire which promotes massive release of seed. This facilitates recruitment in an otherwise unpredictable and unreliable seedbed. In mesic woodland, where cones rarely come into contact With flames, seeds are released spontaneously and site conditions are more conducive to recruitment in the inter‐fire period.