Araucaria Bidwillii - Ecology

Ecology

A. bidwillii has unusual cryptogeal seed germination in which the seeds develop to form an underground tuber from which the aerial shoot later emerges. The actual emergence of the seed is then known to occur over several years presumably as a strategy to allow the seedlings to emerge under optimum climatic conditions or, it has been suggested, to avoid fire. This erratic germination has been one of the main problems in silviculture of the species.

The cones are 20–35 cm in diameter, and are opened by large birds, such as cockatoos, or disintegrate when mature to release the large (3—4 cm) seeds or nuts.

Although there are no reported dispersal agents for the seeds of A. bidwillii, macropods and various species of rats are known as predators of the seeds and tubers. It was observed the bush rat (Rattus fuscipes) was caching bunya seeds a limited distances uphill from parent trees, possibly allowing ridge-top germination. brushtail possums (Trichosurus spp.) were mentioned as carrying the seeds up trees. From a study in 2006, the short-eared possum (Trichosurus caninus) was shown to disperse the seed of A. bidwillii.

Natural populations of this species have been reduced in extent and abundance through exploitation for its timber, the construction of dams and historical clearing. Most populations are now protected in formal reserves and national parks.

A recent problem in small forestry plantations of A. bidwilli in Southeast Queensland is the introduction of red deer (Cervus elaphus). Red deer, unlike possums and rodents, eat bunya cones while still intact, preventing their dispersal.