Casuarina pauper



Casuarina pauper, commonly known as black oak, belah or kariku, is a species of flowering plant in the family Casuarinaceae and is endemic to southern continental Australia. It is a dioecious tree with fissured or scaly bark, waxy branchlets, the leaves reduced to scales in whorls of 9 to 13, the fruit 13–18 mm long containing winged seeds (samaras) 5.5–7.0 mm long.

Description
Casuarina pauper is a dioecious tree similar to C. cristata, that typically grows to a height of 5–15 m, has a DBH of up to 0.5 m, and sometimes produces root suckers. The branchlets are more or less erect or spreading, up to 250 mm long, the leaves reduced to scale-like teeth 0.8–0.9 mm long, arranged in whorls of 9 to 13 around the branchlets. The sections of branchlet between the leaf whorls (the "articles") are waxy, 8–17 mm long and 1.0–1.8 mm wide. The flowers on male trees are arranged in spikes 10–30 mm long, the anthers 0.8–1.1 mm long. The female cones are covered with rusty hairs, on a peduncle 1–14 mm long. The mature cones are usually 10–22 mm long and 11–15 mm in diameter, the samaras 5.5–7.0 mm long.

This species is a poorer, stunted form of C. cristata, and the two species often intergrade where their ranges overlap.

Taxonomy
Casuarina pauper was first formally described in 1989 by Lawrie Johnson in the Flora of Australia from a Ferdinand von Mueller's unpublished description of a plant he collected in the Flinders Ranges in 1851. The specific epithet (pauper) means "scanty" or "poor", referring to the habit of the species compared to C. cristata.

Johnson had previously described Casuarina cristata subsp. pauper (Miq.) L.A.S.Johnson in the journal Nuytsia, based Miquel's C. pauper, but the name was not valid, because Miquel explicitly did not accept von Mueller's description of Casuarina pauper, considering it the same species as C. cristata.

Distribution and habitat
Black oak grows in red-brown soils on open woodland, sometimes with Callitris gracilis, and is widespread across southern Australia, including in the far south-west of Queensland, western New South Wales, north-western Victoria, South Australia, and inland Western Australia.

This species is generally found growing in groves ranging in area from less than 1 to 10 ha at altitudes from 400–500 m, and where the temperature ranges between 3 and 36 C.

Ecology
Casuarina pauper produces abundant viable seed, with regeneration success likely to be inhibited during periods of insufficient soil moisture. When present at low densities, plants tends to reproduce sexually, while established groves extend mostly from the fringes through root suckers, increasing the local area occupied by individual plants.