Post-fire Seed Dispersal and Species Re-establishment in Proteaceous Heath

Abstract

Aspects of seed dispersal of five functionally similar, serotinous species, Banksia serrata L.f., B. ericifolia L.f., B. marginata Cav., Hakea sericea Schrader, and H. teretifolia (Salisb.) Britten (Proteaceae), from coastal heath near Sydney were investigated. These species have seeds with large papery wings apparently suited to dispersal by wind. Terminal falling velocities of seeds of all species were close to 1 m s^-1 despite significant differences in seed sizes and wing loadings. Patterns of aerial dispersal of seeds in a wind tunnel and in a burnt heath site were also similar among species, with seeds dispersed up to 12 m. Seeds were also dispersed along a sandy substrate in burnt heath distances of up to 3 m in 1 h under windy conditions. A survey of post-fire seedling distribution relative to a seed source found seedling density to be highest in and near seed sources, decreasing log_e–linearly with distance from the source up to 40 m. The similarity between distances of seed dispersal determined experimentally and patterns of in situ seedlings relative to a seed source led to the conclusion that wind dispersal of seed is the major determinant of seedling patterns after fire. Recolonisation of areas of local extinction of species following high fire frequency is likely to occur at the rate of a few tens of metres after each successive fire providing that plants have matured during the inter-fire period.