Acacia aneura

Taxobox
name = Mulga

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image_width = 250px
regnum = Plantae
divisio = Magnoliophyta
classis = Magnoliopsida
ordo = Fabales
familia = Fabaceae
genus = "Acacia"
species = "A. aneura"
binomial = "Acacia aneura"
binomial_authority = F.Muell. ex Benth.

Acacia aneura, commonly known as Mulga or True Mulga, is a shrub or small tree native to arid outback Australia.

Description

Mulga is highly variable, in form, in height, and in shape of phyllodes and seed pods. It can form dense forest up to 15 metres high, or small, almost heath-like low shrubs spread well apart. Most commonly, it is a tall shrub. Because it is so variable, the taxonomy of the Mulga has been studied extensively, and although it is likely to be split into several species eventually, there is as yet no consensus on how or even if this should be done. Although generally small in size, Mulga is long-lived, a typical lifespan for a tree undisturbed by fire is in the order of 200 to 300 years.

Mulga has developed extensive adaptations to the Australian desert. Like many "Acacia" species, Mulga has thick-skinned phyllodes. These are optimised for low water loss, with a high oil content, sunken stomata, and a profusion of tiny hairs to reduce transpiration. During dry periods, a Mulga drops much of its foliage to the ground, which provides an extra layer of mulch and from where the nutrients can be recycled.

Like most Australian Acacia species, mulga is thornless. [ [http://www.aridzonetrees.com/AZT%20Interactive%20Buttons/Tree%20Index/Cut%20sheets/Acacia/Acacia%20aneura.htm Arid Zone Trees] ] The needle-like phyllodes stand erect to avoid as much of the midday sun as possible and capture the cooler morning and evening light. Any rain that falls is channeled down the phyllodes and branches to be collected in the soil immediately next to the trunk, providing the tree with a more than threefold increase in effective rainfall. Mulga roots penetrate far into the soil to find deep moisture. The roots also harbour bacteria that fix atmospheric nitrogen and thus help deal with the very old, nutrient poor soils the species grows in.

Habitat and ecology

Mulga savanna and mulga co-dominant tussock grasslands cover roughly 20% of the Australian continent, or about 1.5 million square kilometres. The mean rainfall for much of the habitat for "Acacia aneura" in Australia is roughly 200–250 mm/year, but it goes to as high as 500 mm/year in New South Wales and Queensland. The lowest mean rainfall that it grows in is about 50–60 mm/year. [ [http://www.fao.org/docrep/006/Q2190E/Q2190E10.htm FAO] ] Both summer and winter rainfall are necessary to maintain mulga and the species is absent from semiarid regions that experience summer or winter drought. [Weston, E. J. (1988). Native Pasture Communities. Native pastures in Queensland their resources and management. W. H. Burrows, J. C. Scanlan and M. T. Rutherford. Brisbane, Department of Primary Industries.]

Mulga scrub is distinctive and widespread. The dominant species in these woodlands is Mulga with poplar box ("Eucalyptus populnea") forming an increasingly important co-dominant in the eastern districts. [Harrington, G. N., D. M. D. Mills, et al. (1984). Semi-arid woodlands. Management of Australia's Rangelands. G. N. Harrington and A. D. Wilson. Melbourne, CSIRO Publishing.] [Burrows, W. H., J. O. Carter, et al. (1990). "Management of savannas for livestock production in north-east Australia: contrasts across the tree-grass continuum." Journal of biogeography 17: 503-512.] The extent of ground cover in mulga woodlands varies with canopy density of the overstorey, becoming almost non-existent in extremely dense stands. In more open stands the herbaceous layer consists of wire grasses ("Aristida" spp), Mulga oats ("Monocather" sp.), Mulga mitchell ("Thyridolepis" sp.), Wanderrie ("Eriachne" spp.), finger grasses ("Digitaria" spp.) and love grasses ("Eragrostis" spp.). Various other woody species are also significant in mulga woodlands, particularly hop bushes ("Dodonaea" spp.), "Eremophila" and Cassia ("Senna" spp.). [Weston, E. J. (1988). Native Pasture Communities. Native pastures in Queensland their resources and management. W. H. Burrows, J. C. Scanlan and M. T. Rutherford. Brisbane, Department of Primary Industries.] [Burrows, W. H., J. O. Carter, et al. (1990). "Management of savannas for livestock production in north-east Australia: contrasts across the tree-grass continuum." Journal of biogeography 17: 503-512.]

In contrast to the eucalypt woodlands that dominate much of Australia, mulga woodlands are not well adapted to regular fire and species in mulga communities vary in their ability to survive fires. [Hodgkinson, K. C., G. N. Harrington, et al. (1984). Management of vegetation with fire. Management of Australia’s Rangelands. G. N. Harrington and A. D. Wilson. Melbourne, CSIRO Publishing.] [Dyer, R., A. Craig, et al. (1997). Fire in northern pastoral lands. Fire in the management of northern Australian pastoral lands. T. C. Grice and S. M. Slatter. St. Lucia, Australia, Tropical Grassland Society of Australia.] Many species, including mulga itself, have a very limited ability to resprout after fire, and rely instead on mechanisms of seed production for species survival. Many plants produce hard, woody fruits or seeds, which can not only survive intense heat but may require the stimulus of fire to scarify and promote germination. Long-lived seed store in soil is also common in these woodlands. [White, M. E. (1986). The Greening of Gondwana. Frenchs Forest, Australia, Reed Books.] [Hodgkinson, K. C. (1991). "Shrub recruitment response to intensity and season of fire in a semi-arid woodland." Journal of Applied Ecology 28: 60-70.] [Dyer, R., A. Craig, et al. (1997). Fire in northern pastoral lands. Fire in the management of northern Australian pastoral lands. T. C. Grice and S. M. Slatter. St. Lucia, Australia, Tropical Grassland Society of Australia.]

There are a number of recognised varieties:
* "A. a." var. "aneura"
* "A. a." var. "argentea"
* "A. a." var. "fuliginea"
* "A. a." var. "intermedia"
* "A. a." var. "macrocarpa"
* "A. a." var. "major"
* "A. a." var. "microcarpa"
* "A. a." var. "pilbarana"
* "A. a." var. "tenuis"

Uses

Host tree

Can be planted in relation to Sandalwood plantations as a host tree

Bee forage

The tree's flowers provide forage for bees, especially when there is enough water available. [http://www.worldagroforestry.org/Sites/TreeDBS/aft/speciesPrinterFriendly.asp?Id=5 World AgroForestry Centre] ]

Fodder

Mulga is of great economic important to Australia, especially the pastoral industry. Despite containing considerable amounts of indigestible tannins, mulga leaves are a valuable fodder source, particularly in times of drought, as it is palatable to stock and provides up to 12% crude protein..]

Food

The seeds of "Acacia aneura" were used to make seedcakes. The mulga apple is an insect gall commonly eaten by Aborignal people. Mulga tree gum ("Ngkwarle alkerampwe" in the Arrernte language) is a type of lerp scale found on mulga branches. It provides a tasty honey-like treat for Indigneous people..]

Wood

Construction

Wood from "Acacia aneura" stands up very well to being buried in soil and it is used for posts. The wood has a density of about 850-1100 kg/m³..]

Fuel

The wood is very good as firewood. Very good quality charcoal can be produced from it..]

Implements

Mulga was a vital tree to Indigenous Australians in Central Australia; the wood was a good hardwood for making various implements, such as digging sticks and woomeras.

References

Notes

General references

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ee also

*Acacia

External links

* [http://www.ildis.org/LegumeWeb?version~10.01&LegumeWeb&tno~214&genus~Acacia&species~aneura "Acacia aneura" (ILDIS LegumeWeb)]
* [http://florabase.calm.wa.gov.au/science/timage/3217ic1.jpg"Acacia aneura" Photos (FloraBase)]
* [http://images.google.com/images?svnum=10&um=1&hl=en&ie=ISO-8859-1&oe=ISO-8859-1&gbv=1&q=%22Acacia+aneura%22&btnG=Search+Images "Acacia aneura" (Google Images)]