''Allocasuarina decussata'', commonly known as karri oak or karri she-oak, is a medium-sized tree, or more rarely a shrub, that is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the

south west The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each se ...

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

. 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 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 long, roughly square or X-shaped in cross section, with four scale-teeth in each ring. The rings of scale-leaves are 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 long. It often grows in association with ''

Acacia pentadenia ''Acacia pentadenia'', commonly known as karri wattle, is a shrub or tree of the genus '' Acacia'' and the subgenus ''Pulchellae''. Description The slender willowy shrub or tree typically grows to a height of . The slender erect habit forms a ...

'' and '' Asplenium aethiopicum'' often grows as an epiphyte on its branches.

Taxonomy

This species was first formally described in 1873 by

George Bentham George Bentham (22 September 1800 – 10 September 1884) was an English botanist, described by the weed botanist Duane Isely as "the premier systematic botanist of the nineteenth century". Born into a distinguished family, he initially studie ...

Flora Australiensis ''Flora Australiensis: a description of the plants of the Australian Territory'', more commonly referred to as ''Flora Australiensis'', and also known by its standard abbreviation ''Fl. Austral.'', is a seven-volume flora of Australia published be ...

'' from specimens collected by James Drummond near

Cape Riche Cape Riche is a cape and rural locality in the Great Southern region of Western Australia. By road, it is 525 km south-east of Perth and 123 km north-east of Albany Facilities in the locality include a boat launching ramp and a c ...

, Western Australia. Bentham gave it the name ''Casuarina decussata''. In 1982,

Lawrie Johnson Lawrence Alexander Sidney Johnson Fellow of the Australian Academy of Science, FAA, (26 June 1925 – 1 August 1997) known as Lawrie Johnson, was an Australian Taxonomy (biology), taxonomic botany, botanist. He worked at the Royal Botanic Garden ...

moved it to its current genus ''

Allocasuarina ''Allocasuarina'' is a genus of trees in the flowering plant family Casuarinaceae. They are endemic to Australia, occurring primarily in the south. Like the closely related genus '' Casuarina'', they are commonly called sheoaks or she-oaks. ...

'' in his revision of the she-oaks. It is closely related to '' A. torulosa'' of

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

and

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , establishe ...

The specific epithet (''decussata'') is a

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

word meaning "like the letter X" or "the Roman numeral ten".

Distribution and habitat

Karri oak is restricted to the southwest of Western Australia in the

Esperance Plains Esperance Plains, also known as Eyre Botanical District, is a biogeographic region in southern Western Australia on the south coast between the Avon Wheatbelt and Hampton bioregions, and bordered to the north by the Mallee region. It is a p ...

Jarrah Forest Jarrah forest is tall open forest in which the dominant overstory tree is ''Eucalyptus marginata'' (jarrah). The ecosystem occurs only in the Southwest Botanical Province of Western Australia. It is most common in the biogeographic region named i ...

and

Warren A warren is a network of wild rodent or lagomorph, typically rabbit burrows. Domestic warrens are artificial, enclosed establishment of animal husbandry dedicated to the raising of rabbits for meat and fur. The term evolved from the medieval A ...

biogeographical regions. It grows on loam in the karri forest but also found on much poorer soils in the Stirling Range.

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.

References

{{Taxonbar, from=Q15376171 Fagales of Australia decussata Trees of Australia Plants described in 1873 Endemic flora of Southwest Australia