Allocasuarina decussata

Karri She-Oak
A. decussata, foliage and cones
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Fagales
Family:	Casuarinaceae
Genus:	Allocasuarina
Species:	A. decussata
Binomial name
Allocasuarina decussata (Benth.) L.A.S.Johnson

Allocasuarina decussata, commonly known as Karri Oak or Karri She–oak, is a medium tree to 15 metres high (or more rarely a shrub) endemic to the south–west of Western Australia. It is an understory tree in Karri forest but also occurs as a stunted shrub in places like Bluff Knoll in the Stirling Range.

Description

Karri Oak usually grows as a medium tree 8–15 metres high, although in harsh, exposed situations in places like the top of Bluff Knoll it is a stunted shrub or poorly–formed tree in shrubland. As with other members of the family Casuarinaceae, the foliage consists of wiry green branchlets called cladodes with rings of minute leaf scales. In this species, the branchlets are about 14 cm long, roughly square or X–shaped in cross section, with four scale-teeth in each ring. The rings of scale–leaves are 7–9 mm apart. Separate male and female flowers form on the same individual plant. The fruiting structure is a woody cone, shaped like a short cylinder with its diameter roughly equal to or slightly greater than its length. The fruit is a winged samara 7–9 mm long.^[1] It often grows in association with Acacia pentadenia.<ref name="FPC" and Asplenium aethiopicum often grows as an epiphyte on its branches.^[2]

Taxonomy

A. decussata was first described by George Bentham in 1873 in Flora Australiensis (Volume 6, page 200) from a specimen collected by James Drummond near Cape Riche, Western Australia.^[3] Bentham gave it the name Casuarina decussata but in 1982, Lawrie Johnson moved it to its current genus Allocasuarina in his revision of the she-oaks.^[4] It is closely related to A. torulosa of New South Wales and Queensland.^[5]

Bark of a young A. decussata in the Walpole-Nornalup National Park.

The specific epithet (decussata) is the Latin origin of decussated meaning X–shaped.^[6]

Distribution and habitat

A. decussata is restricted to the south–west corner of Western Australia in the Esperance Plains, Jarrah Forest and Warren biogeographical regions. It grows on loam in the Karri forest but also found on much poorer soils in the Stirling Range.^[7]

Cultivation and uses

Karri Oak is not known in cultivation and there is only limited availability of timber because most trees are in national parks but its pale reddish-brown heartwood has distinctive rays that potentially make it useful as a craft wood.^[5]

References