Rule araucaria (Araucaria rulei)

Description

Rule araucaria fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Rule araucaria description

Araucaria rulei is a tall, rather unusual looking conifer with a dome-shaped canopy and a straight, relatively slender trunk, from which radiate numerous, widely spaced branches. The branches are long but narrow, and turn up abruptly at the tips, so that the tree somewhat resembles a chandelier ^{(2) (4) (5)}. At the tip of each branch are compact tufts of upright, rope-like branchlets, up to 50 centimetres in length and covered in densely overlapping, scale-like leaves. In the juvenile tree, the leaves are narrow and sharply pointed, while in mature individuals they are a glossy dark green, leathery and slightly curved, and measure up to 2.5 centimetres in length. The bark of Araucaria rulei is dark brown, becoming whiter with age, and peels off in horizontal strips, or in irregular scales in older specimens ^{(2) (3) (4)}.

Although potentially growing to 30 metres in height, most individuals of Araucaria rulei are shorter, at around 20 to 25 metres ^{(2) (3) (4)}. The species can be distinguished from the closely related Araucaria muelleri mainly by its deeper, fuller and more round-topped crown, and by its more ‘delicate’ appearance ⁽²⁾. The branches of Araucaria rulei may also occasionally produce secondary branches, whereas those of A. muelleri never do so ^(4) (5).

Size

Height: up to 30 m ^{(2) (3)}

Trunk diameter: up to 0.6 m ⁽²⁾

Rule araucaria biology

Like most Araucaria species ⁽²⁾, Araucaria rulei is monoecious, with male and female cones occurring on the same tree, borne at the tips of the branchlets. However, in this species, individual branches produce either all male or all female cones, with branches at the top of the tree typically producing female cones, and those towards the centre and bottom producing male ones ⁽⁵⁾. The male cone of Araucaria rulei is relatively large and cylindrical, up to 15 centimetres long and 3 centimetres wide, and covered in triangular scales, while the female cone is more spherical, around 12 centimetres by 8 centimetres, with long, overlapping scales that have upturned, thorn-like tips ^{(2) (3) (4)}.

Araucaria rulei apparently produces the female cones first ⁽⁵⁾, from around January to February, with pollination occurring from August to September ⁽⁴⁾. The cones then take from two to three years to ripen, after which they disintegrate to release large seeds, each measuring up to three centimetres in length ^{(2) (3) (4)}.

Rule araucaria range

Araucaria rulei is endemic to New Caledonia, where it occurs in small areas on several isolated massifs (mountain ranges) in the north-west of the main island ^{(1) (6) (7)}, although others report it to also occur in the centre and south ^{(2) (3) (4)}.

Rule araucaria habitat

This species grows on ultramafic rocks and soils, occurring in open woodland and in maquis shrubland (a characteristic scrub-like vegetation), at elevations of around 400 to 1,000 metres ^{(1) (2) (3) (4) (6)}.

Rule araucaria status

Classified as Endangered (EN) on the IUCN Red List ⁽¹⁾.

Rule araucaria threats

As on many Pacific islands, the native vegetation of New Caledonia has been significantly modified by human activities, with over 50 percent of the original cover now gone ^{(8) (9)}. The island has the largest known nickel deposits in the world ⁽⁹⁾, and land clearance for mining is the greatest threat both to Araucaria rulei and to the many other endemic conifers, which are often restricted to the mineral-rich areas from which the nickel ore is obtained. In addition to causing widespread deforestation, mining activities have also resulted in large waste heaps and increased erosion ^{(1) (2) (6) (7) (9)}. Further threats to the native vegetation include human-generated wildfires, which are often started deliberately to clear brush, as well as agriculture, livestock grazing, and the spread of invasive exotic species ^{(6) (7) (8) (9) (10)}.

As a result of these threats, Araucaria rulei has suffered severe population declines, and is now restricted to relatively small and isolated stands, none of which occur in any protected areas ^{(1) (4) (6) (7)}. The species also appears to grow slowly and to regenerate poorly, meaning it may take a long time to recover from these losses ^(1) (6). Araucaria rulei is occasionally grown in cultivation, particularly in Australia ^(2) (3), but fortunately has not been exploited for its timber ^(2) (4).

Rule araucaria conservation

New Caledonia is considered a biodiversity ‘hotspot’, having, for its size, a remarkably unique and diverse flora and fauna ^{(8) (9) (10)}. Of the 3,000 or so plant species, over 74 percent are endemic ^(8) (9), as are all but one of 44 conifer species ^(6) (9). Two thirds of the world’s Araucaria species are also unique to this island ^{(2) (5) (9)}. However, the protected area network on New Caledonia is not currently representative of this diversity, and most of the island’s native plants, including Araucaria rulei, do not occur in any protected areas. In addition, very few existing reserves are covered by any mining regulations ^(8) (9). Conservation priorities therefore include the expansion of New Caledonia’s protected area network, with the creation of new, more representative reserves, as well as a ban on mining within these areas ^{(6) (7) (8) (9)}. More effective fire control, public education programmes, the control of invasive species, and the potential development of ecotourism have also been recommended ^{(6) (7) (9)}.

Specific conservation measures recommended for Araucaria rulei include the establishment of a reserve for the species, for example at the Boulinda Massif, where a significant population occurs ^(6) (7). Attempts have been made to help this species recolonise areas of mine spoil, and have so far shown good results ^(1) (7). Mining is also now being more strictly controlled ⁽¹⁾, bringing hope for the recovery of this unusual and unique conifer.

Find out more

To find out more about the conservation of Araucaria rulei and other conifer species, see:

• The Gymnosperm Database:
  http://www.conifers.org/
• Farjon, A. and Page, C.N. (1999) Conifers: Status Survey and Conservation Action Plan. IUCN/SSC Conifer Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at:
  http://data.iucn.org/dbtw-wpd/edocs/1999-024.pdf
• Eckenwalder, J.E. (2009) Conifers of the World: The Complete Reference. Timber Press, Portland, Oregon.

For more information on conservation on New Caledonia see:

• Conservation International: Biodiversity Hotspots - New Caledonia:
  http://www.biodiversityhotspots.org/xp/hotspots/new_caledonia/Pages/default.aspx

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Glossary

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Monoecious

An organism in which separate male and female organs occur on the same individual.

Pollination

The transfer of pollen grains from the stamen (male part of a flower) to the stigma (female part of a flower) of a flowering plant. This usually leads to fertilisation, the development of seeds and, eventually, a new plant.

Ultramafic

Also known as ultrabasic; refers to igneous rocks (rocks formed when molten rock cools and solidifies) that have a very low silica content and are composed mainly of mafic minerals (dark coloured minerals that are rich in magnesium and iron). The term can also be applied to soils derived from these rocks.

References

1. IUCN Red List (February, 2010)
   http://www.iucnredlist.org
2. Eckenwalder, J.E. (2009) Conifers of the World: The Complete Reference. Timber Press, Portland, Oregon.
3. The Gymnosperm Database (February, 2010)
   http://www.conifers.org/ar/ar/rulei.html
4. Sarrailh, J.M., Chauvin, J.P., Litaudon, M., Dumontet, V. and Pieters, R. (2004) Araucaria rulei Mueller. Bois et Forêts des Tropiques, 282(4): 81-82.
5. Veillon, J.M. (1978) Architecture of the New Caledonian species of Araucaria. In: Tomlinson, P.B. and Zimmermann, M.H. (Eds.) Tropical trees as living systems. Cambridge University Press, Cambridge.
6. Farjon, A. and Page, C.N. (1999) Conifers: Status Survey and Conservation Action Plan. IUCN/SSC Conifer Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at:
   http://data.iucn.org/dbtw-wpd/edocs/1999-024.pdf
7. Jaffré, T., Munzinger, J. and Lowry II, P.P. (2010) Threats to the conifer species found on New Caledonia’s ultramafic massifs and proposals for urgently needed measures to improve their protection. Biodiversity and Conservation, published online 02 February 2010.
8. Jaffré, T., Bouchet, P. and Veillon, J.M. (1998) Threatened plants of New Caledonia: is the system of protected areas adequate?. Biodiversity and Conservation, 7: 109-135.
9. Conservation International: Biodiversity Hotspots - New Caledonia (February, 2010)
   http://www.biodiversityhotspots.org/xp/hotspots/new_caledonia/Pages/default.aspx
10. WWF: New Caledonia Moist Forests (February, 2010)
    http://www.panda.org/about_our_earth/ecoregions/newcaledonia_moist_forests.cfm