This acacia is mainly confined to the Pilbara area in north-western Western Australia. Its latitudinal range is 20-24o S and it is found from near sea level to 400 m. (WA)
A moderately fast-growing, nitrogen-fixing, multi-stemmed shrub or small tree, 1-8 m tall with dark red bark, peeling in narrow curled strips. The phyllodes are flat, 3-8 cm long by 1-2 mm wide, dull, slightly resinous with 1-2 prominent longitudinal nerves. The foliage is dense, soft and delicate. Flower heads are yellow, cylindrical spikes, 1-2 cm long. Pods are strongly curved 8-10 mm wide, resinous and sticky, frequently with sparse golden hairs and a net-like venation. Flowering is from April - August and seeds mature in October - November. There are about 12 000 viable seeds per kilogram and pretreatment with boiling water for one minute promotes germination.
Ecology/Way of Life:
It occurs in the warm to hot, arid and semi-arid zones. Coastal areas are frost-free but inland there are 2-5 frosts annually. Mean annual rainfall is 230-400 mm with a summer maximum and a dry season of 7-8 months. It is commonly found along watercourses, on sand plains and in rolling, stony topography. The soils are mainly shallow gravelly sands, but also cracking clays and calcareous earths. They are infertile and neutral to alkaline. This acacia is a component of tall shrubland and is also present in the understorey of open-forest or woodland along watercourses. It may form pure thickets or be associated with other acacias. In stony areas it occurs with Eucalyptus gamophylla and E. leucophloia.
Interaction with Humans/Threats:
The small size of the stem limits its use to fuelwood. It is not regarded as a fodder species in Australia but it has been planted in West Africa where its characteristic of retaining its foliage in the dry season and palatability to sheep, cattle and goats makes it useful for fodder. It has potential for erosion control, fixation of sand dunes and has been used as a low windbreak. Its tendency to form thickets and tolerance of harsh conditions suggest it has potential to become a weed in suitable situations.
Acacia trachycarpa was named in 1904 by Ernest Pritzel, a German plant taxonomist; the name is based on the Greek akakia = a thorny plant, specifically Acacia arabica, and a comination of trachys = rough and carpos = fruit, referring to the surface texture of the pod.
Doran, J.C. and Turnbull, J.W. (eds.) 1997. Australian trees and shrubs; species for land rehabilitation and farm planting in the tropics. ACIAR Monograph no. 24. Australian Centre for International Agricultural Research, Canberra. 384p.
Thomson. L.A.J., Turnbull, J.W. and Maslin, B.R. 1994. The utilisation of Australian species of Acacia, with particular reference to those of the subtropical dry zone. Journal of Arid Environments 27: 279-295.
Wheeler, J.R., Rye, B.l., Koch, B.L. and Wilson, A.J.G. 1992. Flora of the Kimberley region. Western Australian Herbarium, Department of Conservation and Land management, Perth. 1327p.
Topics:Plant structure Climatic zones Soils Vegetation types Fodder Firewood Soil Conservation Windbreak Germination Aboriginal resources
Text & map from Australian Trees and Shrubs, courtesy Australian Centre for International Agricultural Research; text edited by J. Turnbull; photo courtesy T. Vercoe.
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