Fire regime, soil fertility and growth form interact to shape fire and growth traits in two co-occurring 'Banksia' species

Abstract

Inter- and intra-specific comparisons were made between several co-occurring populations of two 'Banksia' species growing in Eastern Australian dry sclerophyll open woodland that experiences a grass-fueled surface-fire regime. The two species differ in life-history from a short basal resprouter (B. 'Neoanglica') to a tall fire-survivor (B. 'integrifolia'). Growth (LMA = leaf mass per unit mass area), persistence (bark thickness) and recruitment (serotiny) traits were determined across independent gradients in soil fertility and fire frequency. Trait correlations for the two species showed distinct patterns, from each other and across environments, with the resprouter having higher LMA and infructescence retention but lower bark thickness. However, there were no consistent intraspecific patterns with variation in fire and soil nutrients. LMA only varied in B. 'integrifolia' with soil fertility, and fire frequency had no effect on either species. Relative bark thickness varied with plant size but not among sites. There was a trend of increasing pyriscence with fire in B. 'neoanglica' and with lower nutrients soils but not in B. 'integrifolia'. Clearly the two species respond differently to variability in nutrients and fire. Nevertheless, growth form appears to be the strongest determinant of both growth (LMA) and fire traits (thicker bark; pyriscence) in these co-existing 'Banksia' species.