Banksia Oblongifolia - Ecology

Ecology

Banksia oblongifolia plants can live for more than 60 years. They respond to bushfire by resprouting from buds located on the large woody lignotuber. Larger lignotubers have the greatest number of buds, although buds are more densely spaced on smaller lignotubers. A 1988 field study in Ku-ring-gai Chase National Park found that shoots grow longer after fire, particularly one within the previous four years, and that new buds grow within six months after a fire. These shoots are able to grow, flower and set seed two to three years after a fire. The woody infructescences also release seeds as their follicles are opened with heat, although a proportion do open spontaneously at other times. One field study in Ku-ring-gai Chase National Park found 10% opened in the absence of bushfire, and that seeds germinated, and young plants do grow. Older plants are serotinous, that is, they store large numbers of seed in an aerial seed bank in their canopy that are released after fire. Being relatively heavy, the seeds do not disperse far from the parent plant.

Bird species that have been observed foraging and feeding at the flowers include the Red Wattlebird (Anthochaera carunculata), Lewin's Honeyeater (Meliphaga lewinii), Brown Honeyeater (Lichmera indistincta), Tawny-crowned Honeyeater (Gliciphila melanops), Yellow-faced Honeyeater (Lichenostomus chrysops), White-plumed Honeyeater (L. penicillatus), White-cheeked Honeyeater (Phylidonyris niger), New Holland Honeyeater (P. novaehollandiae), Noisy Friarbird (Philemon corniculatus), Noisy Miner (Manorina melanocephala) and Eastern Spinebill (Acanthorhynchus tenuirostris). Insects recorded visiting flower spikes include the European Honey Bee and ants. The swamp wallaby (Wallabia bicolor) eats new shoots that grow from lignotubers after bushfire.

One field study found 30% of seeds were eaten by insects between bushfires. Insects recovered from inflorescences include the banksia boring moth (Arotrophora arcuatalis), younger instars of which eat flower and bract parts before tunneling into the woody axis of the spike as they get older and boring into follicles and eating seeds. Other seed predators include unidentified species of moth of the genera Cryptophasa and Xylorycta, as well as Scieropepla rimata, Chalarotona intabescens and Chalarotona melipnoa and an unidentified weevil species. The fungal species Asterina systema-solare, Episphaerella banksiae and Lincostromea banksiae have been recorded on the leaves.

Like most other proteaceae, B. oblongifolia has proteoid roots—roots with dense clusters of short lateral rootlets that form a mat in the soil just below the leaf litter. These enhance solubilisation of nutrients, allowing nutrient uptake in low-nutrient soils such as the phosphorus-deficient native soils of Australia. A study of coastal heaths on Pleistocene sand dunes around the Myall Lakes found B. oblongifolia on slopes (wet heath) and B. aemula grew on ridges (dry heath), and the two species did not overlap. Manipulation of seedlings in the same study area showed that B. oblongifolia can grow longer roots seeking water than other wet heath species and that seedlings can establish in dry heath, but it is as yet unclear why the species does not grow in dry heath as well as wet heath. Unlike similar situations with Banksia species in Western Australia, the two species did not appear to impact negatively on each other.