Casuarina pauper

Description

C. pauper is a dioecious tree, 5 to 15 metres tall and up to 0.5 metre in diameter (Boland, Brooker & McDonald 2006; Callister 2004). Specimens growing in the open often develop a dense crown, and when growing in dense stands the main stem tends to be straight for more than half the total height (National Research Council 1984).

The foliage is not composed of true leaves but rather of jointed branchlets that function like leaves (Wilson & Johnson 1989). The true leaves are tiny, tooth-like structures protruding from around the top of each joint (DAFF). Leaves are strongly waxy, densely and very shortly hairy, with teeth spreading to recurved (Wilson & Johnson 1989).

Bark is hard, dark brown to blackish, with a tight scaly appearance (Wilson & Johnson 1989). Sapwood is wide and creamy coloured, heartwood is reddish brown and very dense (Boland, Brooker & McDonald 2006).

Seedlings consist of both deciduous and persistent branches similar in morphology. Whorls of 4 leaf teeth are closely oppressed to the branch at the joint, gradually increasing in number, with internodes being 0.3-0.4 cm long (Boland, Brooker & McDonald 2006).

Adult plants consist of both deciduous and permanent branches, which are noticeably different in morphology (Boland, Brooker & McDonald 2006). The deciduous branches are robust, dark olive-green to grey, consisting of mostly pendent branchlets 10–20 cm long, shed after 2-3 seasons (Boland, Brooker & McDonald 2006). Erect leaf teeth occur in whorls of 9-16, consist of internodes of approximately 0.7-1.5 cm long, spreading to recurved (Boland, Brooker & McDonald 2006).

As the species is dioecious, male and female inflorescences are on separate trees. Male flowers are located on small slender terminal spikes at the end of deciduous branches (Boland, Brooker & McDonald 2006). Female flowers are grouped in alternating whorls of 9-16, eventually forming a cone, which is grey, subspherical to rounded oblong in shape measuring 1.5-3 x 1.5-2.5 cm (Boland, Brooker & McDonald 2006). Bracteoles are short and tawny, pubescent and opening widely at dehiscence (Boland, Brooker & McDonald 2006). Fruits are dull yellow-brown, elliptical, flattened, up to 5.5-7.0mm long (Boland, Brooker & McDonald 2006).

Taxonomy

The word ‘casuarina’ is derived from the word kasuari (the Malay word for cassowary), in reference to the similarity of the tree’s drooping branches to the feathers of the bird (DAFF & n.d). The word ‘pauper’ is Latin (meaning poor, scanty, meagre), relating to the smaller, poorer habit of this species when compared to C.cristata (Boland, Brooker & McDonald 2006).

Previous nomenclature - Casuarina stricta ssp. pauper, Casuarina cristata, Casuarina pauper ssp. pauper, Casuarina lepidophloia, Casuarina cambagei (Callister 2004), Casuarina cristata subsp. pauper (Miq.) L.A.S. Johnson (Wilson & Johnson 1989; National Research Council 1984).

Common names - Black Oak, Inland Sheoak, Belah (Callister 2004; National Research Council 1984).

Distribution

C. pauper is widespread across a band of southern Australia, including western New South Wales, north-western Victoria, inland South Australia, Central Australia, south-western Queensland, and southern inland Western Australia (Boland, Brooker & McDonald 2006; Wilson & Johnson 1989).

C.pauper is generally found growing in groves ranging from ≤1 to 10ha (Barrit & Facelli 2001). This species can withstand compact clay soils and high alkalinity (National Research Council 1984).

The species occurs in the altitudinal range of 400-500m, surviving in areas where the hottest month is 32-36 °C and 3-7 °C in the coldest month, being moderately tolerant of frosts. Generally located in areas averaging 200-350mm of rainfall per year (Boland, Brooker & McDonald 2006).

Reproduction and dispersal

C.pauper produces abundant viable seed, with regeneration success likely to be inhibited during periods of insufficient soil moisture required for seedling survival (Callister 2004; Auld 1995). Seeds consist of a papery transparent wing with conspicuous midrib (Wilson & Johnson 1989), and may be dispersed by wind, surface run-off, and animals such as ants and emus (Callister 2004). The species also regenerates from basal shoots (Callister 2004). Vegetative recruits tend to have a high survival rate, although the survival of both forms of recruits under rabbit and kangaroo grazing is extremely low, as both are highly palatable (Keith 2004). When present at low densities, C.pauper tends to reproduce sexually, while established groves extend mostly from the fringes through vegetative shoots, increasing the local area occupied by the individuals (Barrit & Facelli 2001).

Uses

C.pauper is fast growing, and improves the levels of nitrogen in the soils, produced by biological fixation (DAFF & n.d), with their roots fixing atmospheric nitrogen through nodules that contain specially adapted symbiotic bacteria of the genus Frankia spp. (Barrit & Facelli 2001; DAFF & n.d). This allows Casuarina species to grow on nutrient poor soils, and other limiting environments such as sandy soils or granite outcrops (DAFF & n.d).

Casuarina species may be of benefit to farming communities as they provide an excellent source of shade, shelter and erosion control on farms, (DPI 2010) and to a limited extent, is a source of emergency drought fodder (National Research Council 1984). The timber they provide is hard and durable, suitable for fencing, woodturning and firewood (Boland et al. p. 74).

Indigenous people traditionally use the hard wood of Casuarina species for making a number of implements such as boomerangs, spears, clapping sticks, digging sticks, shields and clubs (Merideth, & Yeo n.d; DAFF & n.d). Young shoots and branchlets can be chewed to reduce thirst, and cones may also eaten (Merideth, & Yeo n.d; DAFF & n.d). Casuarina cones can also be soaked in water to provide a lemon flavoured drink (Merideth, & Yeo n.d).

Conservation

Not considered rare or endangered.