590. WOLLEMIA NOBILIS

Araucariaceae

Authors

  • John Pastoriza-Piñol


Abstract

SummaryWollemia nobilis W.G. Jones, K.D. Hill & J.M. Allen, (Araucariaceae) was recently discovered in Australia. The male and female strobili and a typical shoot are illustrated, and photographs of the trees in habitat are shown.

Journalists the world over heralded the discovery of the Wollemi Pine (Wollemia nobilis) as equal to finding a living dinosaur. The discovery by David Noble of a single stand of trees deep within a narrow sandstone canyon of the Wollemi National Park just 150 km from Sydney captured the attention of scientists and horticulturalists worldwide. This was an important and unique find as Wollemia has survived for more than 90 million years against a decline in soil fertility, climatic pressures, fire and disturbance from human urbanisation.

Most of Australia’s native flora has evolved from Gondwanan rainforest stock. During the Mid-Tertiary, laterisation caused a reduction in soil fertility due to fixation of phosphorus in iron and aluminium complexes in the soil. Low nutrient soil and lower rainfall became selective pressures which led to the evolution of more sclerophyllous forest (Florence 1981). During the Cretaceous, forests were dominated by Wollemia, other primitive Araucariaceae and early ferns. Today the remaining stands of Wollemia are competing with more evolved angiosperms.

The Wollemia trees are emergent above warm temperate rainforest dominated by Ceratopetalum apetalum D.Don coachwood and Doryhora sassafras Endl, sassafras, in a deep sheltered gorge surrounded by sandstone cliffs of the Triassic Narrabeen Group. Tall eucalypt woodland dominated by Eucalyptus piperita Sm, is adjacent, giving way to dry open woodland up-slope. Soil is sandstone-derived boulder alluvium, with high organic matter, some shale component and a substantial basalt wash from higher reaches of small tributary canyons. The local microclimate is wet, with a permanent creek and an understorey dominated by ferns, including Dicksonia antarctica, Cyathea australis, Adiantum diaphanum, Doodia aspera and Blechnum nudum.

The Araucariaceae is well represented in Australia’s native flora and includes the Norfolk Island Pine (Araucaria heterophylla), Hoop Pine (Araucaria cunninghamii), Bunya (Araucaria bidwillii) and Queensland Kauri (Agathis robusta). The discovery of Wollemia is of particular interest to both paleobotanists and taxonomists as this genus has been genetically isolated for the last 90 million years and could provide an insight into the types of vegetation from the Cretaceous. Fossilised remains of Wollemia are estimated at 90 million years old and are geographically distributed as far as Antarctica and New Zealand.

Since the discovery of the first stand of Wollemia a further two sites have been discovered nearby. It is not uncommon for scientific researchers who visit these stands, to be blindfolded and flown into this wilderness via helicopter (Woodford 2000). Initial studies of the first stand of Wollemia have identified 40 individual trees, equally of juvenile and mature age, suggesting some gene flow through production and germination of seed. The largest of the trees, named King Billy currently reaches 40 m in height and is estimated to be more than 1000 years old.

Wollemia possesses unusual leaf axil anatomy. Most members of the Araucariaceae have a single main stem and only produce another leader after substantial damage (Burrows & Bullock 1999), while the meristems of the young Wollemia continue to develop very slowly beneath the bark, forming small buds. If there is some disturbance, such as a tree falling to the forest floor, these buds can develop into basal sprouts and develop into mature trees, allowing the tree to regenerate. This mechanism is known as coppicing.

Genetic studies have identified that there is little or no genetic variation in these trees. This is a great concern to researchers, as the introduction of a pathogen such as Phytophthora cinnamomi could decimate the entire population of surviving trees (Bullock 2001). Procedures have been put in place to conserve these stands and the Australian Government has a conservation plan to propagate trees. The first release of trees has been certified as vegetative propagations from the largest tree in the stand, King Billy (Hoy 2005).

On initial inspection, Wollemia exhibits some morphological similarities with Cephalotaxus and Cunninghamia. Wollemia has distinct juvenile and adult leaves, heteroblasty. The leaves are helically inserted and twisted to show four subopposite ranks in adult foliage, but spreading more pectinately in juvenile foliage, and are rich cobalt green in colour (Jones et al. 1995). Each single branch characteristically consists of 3–5 definite growth areas, where the ultimate leaves of each growth are quite small defining one growth from the other. New buds appear drenched in a thick impenetrable resin which in time erupt into vibrant green leaves or reproductive cones. The tree exudes quantities of this opaque white resin which may retard phytophagous insects/marsupials or fungal attack. The bark is unusual in texture and has been compared with rabbit faeces or black popcorn. Wollemia, like other members of the Araucariaceae, lack the ability to shed their leaves when they have passed their usefulness and shed entire branches once the leaves have aged (Hill 2001).

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[ Wollemia nobilis (young shoot) JOHN PASTORIZA-PIÑOL]

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[ Wollemia nobilis (female strobilus) JOHN PASTORIZA-PIÑOL]

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[ Wollemia nobilis (male strobilus) JOHN PASTORIZA-PIÑOL]

With the current restrictions on the collection and study of living material, fresh cones are difficult to obtain. Herbarium and preserved specimens provide a useful guide to the general shape and size of both the male and female cones. The Royal Botanic Gardens Sydney has probably the most comprehensive herbarium material to date of collected material of Wollemia. Wollemia reproductive cones are reminiscent of other Araucariaceae, as can be seen in the accompanying illustrations. Under magnification, the individual pollen sacs are attached to the microsporophyll, and this has a thin axis to the rachis of the cone. The female cone is also quite unusual and has been compared to a sea urchin. In contrast to the nut-like seeds of Araucaria, Wollemia produces winged and flattened seeds like Agathis, the wings being produced by the extended bract scale.

Conservation This species was discovered in 1994 and since then three sub-populations, all within 2–3 km distance in a single canyon system, have been found. Extensive searches have not yielded any other, more distant stands of this tree, so it is likely that the total population does not exceed 100 mature trees and is probably smaller. Counting individuals is difficult as the trees readily coppice from base or root meristems and several trunks may belong to a single individual. Access is difficult and the site is still kept a secret although by now (2007) there must be people who have unauthorized knowledge of it. The species occurs entirely within the undeveloped Wollemi Wilderness of Wollemi National Park. Regeneration occurs both from seeds and vegetatively and under entirely natural conditions the species seems able to survive. However, effects of human disturbance on site and, in the longer term, possible effects of climate change (e.g. drying of the permanent canyon bottom creek) make these small populations, the last to exist in a long declining trend as evidenced by the fossil record, critically endangered. IUCN: Critically Endangered (CR, criterion D) [Assessment: IUCN-SSC conifer Specialist Group, March 2007].

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[ Stand of Wollemia nobilis in the wild in Wollemi National Park. ]

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[ Stand of Wollemia nobilis in the wild in Wollemi National Park. ]

Cultivation On winning the commercialisation tender in March 1999 the Queensland Forestry Research Institute and Birkdale Nursery were selected as the recipients of 500 Wollemia plants propagated from the Royal Botanic Gardens Sydney. Germinating plants from seed has quite a low success rate as relatively few seeds are produced. As such, vegetative propagation is the best means by which to increase numbers of trees commercially. Queensland Forestry has now propagated almost 500,000 plants and Birkdale is marketing them in Australia and overseas, under Wollemi-Pine International www.wollemipine.com (Hoy 2005). Healthy specimens are currently growing in the Royal Botanic Gardens Sydney and another at Mount Annan Botanic Gardens in New South Wales, as well as one in the Royal Botanic Gardens, Kew. These trees are on public display but are still protected by means of iron cages. A special display and promotion coincided with the Chelsea Flower Show, 2007.

The tree seems to survive and grow well in temperate climates without special treatment. At Kew the main plant growing in the open has thrived in an open site on the lawn opposite the Orangery. An older plant in the Temperate House has produced male cones. There has been no prolonged cold winter since the trees were planted, but they have stood –5 C without damage.

The coloured plates show a female strobilus on adult foliage, with a dried bract-scale and seed, a developing male strobilus on immature foliage with a mature male strobilus, and a branch with juvenile foliage.

Wollemia nobilis W.G. Jones, K.D. Hill & J.M. Allen, Telopea, 6: 173–176 (1995). Type: Australia, New South Wales: Central Tablelands: Wollemi National Park, W.G.Jones NSW 362731, 17 Nov. 1994 (holo. NSW; iso. BM, BRI, CANB, E, HO, K, L, MEL, MO, NY, P).

Description Monoecious trees to 40m tall, frequently coppicing from the base; trunks to 1.2 m diam, crown slender, columnar, broadest at about 1/3 of total height. Bark peeling in thin, fragile, equidimensional dark red-brown scales on younger stems, becoming densely covered with soft and spongy nodules or tubercules to 10 mm in diameter. Orthotropic shoots with helical phyllotaxis and acute, pungent, keeled, decurrent, narrowly triangular leaves 3–10 mm long, 2–4 mm wide at base. Juvenile and lower canopy plagiotropic shoots horizontal, leaves opposite or sub-opposite, distichous and twisted to present adaxial surfaces uppermost, linear to narrowly triangular, chartaceous, rounded or obtuse, hypostomatic, deep green above, glaucous below, broad-based and decurrent, with 6–10 parallel veins and 4–6 parallel resin canals; repetitive growth units commencing with short scale-like leaves to 3 mm long, leaves increasing to 20–80 mm long, 2–5 mm wide. Adult upper canopy plagiotropic shoots initially near-vertical, becoming horizontal and later pendulous, leaves opposite or sub-opposite tetrastichous and twisted to present adaxial surfaces uppermost, narrowly oblong, coriaceous, rounded, dull light to mid green, unequally amphistomatic, broad-based and decurrent, with 9–14 parallel veins and 6–8 parallel resin canals; repetitive growth units commencing with short scales-like leaves to 3 mm long, leaves increasing to 10–40 mm long, 4–8 mm wide. Male strobili terminal o first-order leafy plagiotropic shoots, to 109 mm long, 19 mm diameter., subtended by c. 8 helically arranged broadly triangular to semicircular bracts 3–5 mm long, 3–5 mm wide. Microsporophylls numerous (more than 500), helically arranged, dark red-brown, peltate, with a raised angular termination, with 4–9 elongate, pendulous microsporangia. Pollen ovid, inaperturate, granular, unwinged. Female strobili terminal on first-order leafy plagio-tropic shoots, usually borne on ascending branches above male strobili, globular to broadly ellipsoidal, mid green, becoming brown and shedding individual bract-scales at maturity, to 125 mm long, 100 mm diameter. Bract-scales numerous (more than 300), flattened, laterally winged, 12–17 mm long, 14–22 mm wide, 3–5 mm thick, with a narrowly triangular apical extension 6–12 mm long, 2–4 mm wide at base, bearing a single inverted ovule adaxially and centrally. Scales wholly fused with and indistinguishable from bracts. Seeds circumferentially winged, pale brown, 7–11 mm long, 5–7 mm wide, 6–9 mm wide including wing. Germination epigeal, cotyledons 2, oblong, 20–30 mm long, 4–6 mm wide, with c. 8 parallel veins and no discernable midrib.

Distribution Australia, New South Wales, Wollemi National Park, within 200 km north-west of Sydney in the Central Tablelands.

Habitat In a deep humid gorge, with an understory of ferns.

Acknowledgments

Acknowledgments I would like to thank Katy Sommerville, Collections Manager, National Herbarium of Victoria for access to their herbarium specimens of Wollemia nobilis. I would sincerely like to thank Louisa Murray, Collections Co-ordinator, National Herbarium of New South Wales for her assistance with examining their extensive herbarium specimens and providing other important information and contacts; thanks also to Aljos Farjon for his comments on the text.

Ancillary