Araucaria muelleri (Carrière) Brongn. & Gris.

Araucariaceae

One of 13 species of Araucaria endemic to New Caledonia where it has a restricted distribution and has become Endangered due to mining and fire.

Description

Habit

A monoecious tree up to 20m tall, with a d.b.h. up to 0.8m at maturity. Pyramidal when young and developing a very distinct open, candelabriform crown as it matures. The thick bark is light grey or reddish-grey, often almost white, peeling in horizontal plates.

Foliage

Adult leaves lanceolate to ovate with an obtuse apex, 2–3 x 1–2cm.

Cones

Male pollen-cones terminal, up to 25cm long, mature early July (variant with lustrous leaves), or in September to December (typical form). Female seed-cones terminal on very short branches, mature cones broadly ovoid, up to 15cm long; bracts with prominent long tips. Young female cones appear in October, mature cones appear in March.

Key characters

A. muelleri has the largest adult leaves of any New Caledonian Araucaria species (up to 35mm in length). The stomata on the underside of adult leaves are numerous and scattered along the length. The almost white bark, the trunk with lax, long, horizontally spreading primary branches always in whorls of 4, and the candelabra-shaped crown also distinguish this species. In certain parts of its range (e.g. Goro Plateau and Mamie) a variant occurs that only has a few stomata at the base of the adult leaves so that it resembles a very large leafed A. rulei.

Distribution

Restricted to New Caledonia on Grand Terre where it is limited to a few locations in the southernmost part of Province Sud between 150 to 1,000m above sea level. Subpopulations may consist of several hundred trees within a relatively small area (e.g. Montagne des Sources and Mamié) or in small scattered groups (e.g. Plaine des Lacs, Col de Yaté).

Habitat and Ecology

Usually found on ridges at altitudes ranging from 150–1,000m in maquis minier, a distinctive type of vegetation only found in New Caledonia that consists of an evergreen, sclerophyllous shrub layer over-topped by emergent trees, usually Araucarias (Enright & Hill, 1995). Rarely found in dense humid forest with Nothofagus spp. This species is restricted to serpentine soils. In lowland areas it is commonly associated with Dacrydium araucarioides and Gymnostoma chamaecyparis.

Conservation Status

Global status and rationale

Endangered B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)

The restricted distribution which is due to its edaphic specificity means that the current extent of occurrence is considerably less than 1,000km². The major subpopulations are severely fragmented and the area, extent and quality of habitat have declined. The principal threats are the expansion of mining activities (e.g., construction of a smelter on Goro Plateau) and an increased risk of fire, even in protected areas such as Montagne de Sources. Several locations contain less than twenty trees and these are likely to disappear in the near future. Regeneration and reproduction is very limited. Some restoration activities have been initiated on the Goro Plateau but these are at a very early stage (Cornu et al., 2001).

Global threats

Mining developments on the Goro Plateau threaten subpopulations in that area. In other parts of its range, including protected areas, it is susceptible to wildfires and an increase in their frequency.

Conservation Actions

This species has been used in local reforestation and ecological restoration projects, e.g. at Chûtes de la Madeleine (Sarrailh et al., 2003) and Ouénarou (Mazzeo, 2004).