''Acacia aneura'', commonly known as mulga or true mulga, is a shrub or small tree native to arid

outback The Outback is a remote, vast, sparsely populated area of Australia. The Outback is more remote than the bush. While often envisaged as being arid, the Outback regions extend from the northern to southern Australian coastlines and encompass a n ...

areas of

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. It is the dominant tree in the habitat to which it gives its name ( mulga) that occurs across much of inland Australia. Specific regions have been designated the

Western Australian mulga shrublands The Western Australian Mulga shrublands is a deserts and xeric shrublands ecoregion of inland Western Australia. It is one of Australia's two mulga ecoregions, characterized by dry woodlands of mulga trees (''Acacia aneura'' and related species) ...

in Western Australia and

Mulga Lands The Mulga Lands are an Interim Biogeographic Regionalisation for Australia, interim Australian bioregion of eastern Australia consisting of dry sandy plains with low mulga (habitat), mulga woodlands and shrublands that are dominated by ''Acacia ...

in Queensland.

Description

Mulga trees are highly variable, in form, in height, and in shape of phyllodes and seed pods. They can form dense

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

s up to high, or small, almost heath-like low shrubs spread well apart. Most commonly, mulgas are tall shrubs. Because the mulga is so variable, its

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

has been studied extensively, and although ''A. aneura'' 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, mulgas are long-lived, a typical life span for a tree undisturbed by fire is of the order of 200 to 300 years. Mulga has developed extensive adaptations to the Australian

desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...

. Like many ''

Acacia ''Acacia'', commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia. The genus na ...

'' species, it has thick-skinned

phyllode Phyllodes are modified petioles or leaf stems, which are leaf-like in appearance and function. In some plants, these become flattened and widened, while the leaf itself becomes reduced or vanishes altogether. Thus the phyllode comes to serve the ...

s. These are optimised for low water loss, with a high oil content, sunken

stomata In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...

, and a profusion of tiny hairs which reduce

transpiration Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth a ...

. During dry periods, mulgas drop much of their foliage to the ground, which provides an extra layer of

mulch A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth and enhancing the visual appeal of the area. A m ...

and from where the nutrients can be recycled. Like most Australian ''Acacia'' species, mulga is thornless. 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 channelled down the phyllodes and branches to be collected in the

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

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 Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

that fix atmospheric

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

and thus help deal with the very old, nutrient-poor soils in which the species grows.

Aboriginal peoples Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original people ...

of the

Coober Pedy Coober Pedy () is a town in northern South Australia, north of Adelaide on the Stuart Highway. The town is sometimes referred to as the "opal capital of the world" because of the quantity of precious opals that are mined there. Coober Pedy is ...

area in

South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...

refer to mulga trees as ''Umoona'', which means "long life".

Habitat and ecology

Mulga

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...

and mulga codominant tussock

grassland A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...

s cover roughly 20% of the Australian continent, or about 1.5 million square kilometres. The

mean There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value (magnitude and sign) of a given data set. For a data set, the ''arithme ...

rainfall Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...

for much of the

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

for ''A. aneura'' in Australia is roughly 200–250 mm/year, but it goes to as high as 500 mm/year in

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 , established_ ...

. The lowest mean rainfall where it grows is about 50–60 mm/year. Both summer and winter rainfall are necessary to maintain mulga, and the species is absent from semiarid regions that experience summer or winter

drought A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...

. Mulga scrub is distinctive and widespread, with the

of eastern Australia defined as a specific

bioregion A bioregion is an ecologically and geographically defined area that is smaller than a biogeographic realm, but larger than an ecoregion or an ecosystem, in the World Wide Fund for Nature classification scheme. There is also an attempt to use the ...

. The dominant species in these

woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...

s is mulga, with poplar box (''

Eucalyptus populnea ''Eucalyptus populnea'', commonly known as poplar box, bimble box or bimbil box, is a species of small to medium-sized tree that is endemic to eastern Australia. It has rough, fibrous or flaky bark on the trunk and branches, egg-shaped, elliptic ...

'') forming an increasingly important codominant in the eastern districts. The extent of

ground cover Groundcover or ground cover is any plant that grows over an area of ground. Groundcover provides protection of the topsoil from erosion and drought. In an ecosystem, the ground cover forms the layer of vegetation below the shrub layer known as t ...

in mulga woodlands varies with canopy density of the overstorey, becoming almost nonexistent in extremely dense stands. In more open stands, the

herbaceous layer Stratification in the field of ecology refers to the vertical layering of a habitat; the arrangement of vegetation in layers. It classifies the layers (sing. ''stratum'', pl. ''strata'') of vegetation largely according to the different heights to w ...

consists of wire grasses (''

Aristida ''Aristida'' is a very nearly cosmopolitan genus of plants in the grass family. ''Aristida'' is distinguished by having three awns (bristles) on each lemma of each floret. The genus includes about 300 species found worldwide, often in arid war ...

'' spp.)mulga is long-lived, mulga oats ('' Monocather'' sp.), mulga mitchell ('' Thyridolepis'' sp.), wanderrie (''

Eriachne ''Eriachne'' (common name Wanderrie grass) is a genus of plants in the grass family. Most of the species are found only in Australia, with the ranges of a few extending northward into New Guinea, parts of Asia, and Micronesia. It is found in ar ...

'' spp.), finger grasses (''

Digitaria ''Digitaria'' is a genus of plants in the Poaceae, grass family native to tropical and warm temperate regions but can occur in tropical, subtropical, and cooler temperate regions as well. Common names include crabgrass, finger-grass, and fonio. ...

'' spp.) and love grasses (''

Eragrostis ''Eragrostis'' is a large and widespread genus of plants in the grass family, found in many countries on all inhabited continents and many islands. ''Eragrostis'' is commonly known as lovegrass or canegrass. The name of the genus is derived fr ...

'' spp.). Various other woody species are also significant in mulga woodlands, particularly hop bushes (''

Dodonaea ''Dodonaea'' is a genus of about 70 species of flowering plants, often known as hop-bushes, in the soapberry family, Sapindaceae. It has a cosmopolitan distribution in tropical, subtropical and warm temperate regions of Africa, the Americas, so ...

'' spp.), '' Eremophila'' and cassia ('' Senna'' spp.). In contrast to the

eucalypt Eucalypt is a descriptive name for woody plants with capsule fruiting bodies belonging to seven closely related genera (of the tribe Eucalypteae) found across Australasia: ''Eucalyptus'', '' Corymbia'', '' Angophora'', ''Stockwellia'', ''Allosyn ...

woodlands that dominate much of Australia, mulga woodlands are not well adapted to regular

fire Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products. At a certain point in the combustion reaction, called the ignition ...

and species in mulga communities vary in their ability to survive fires. Many species, including mulga, 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 also may require the stimulus of fire to scarify and promote

germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...

. Long-lived seed stores in soil is also common in these woodlands. The recognised varieties are: * ''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

Agriculture

Mulga can be planted with

sandalwood Sandalwood is a class of woods from trees in the genus ''Santalum''. The woods are heavy, yellow, and fine-grained, and, unlike many other aromatic woods, they retain their fragrance for decades. Sandalwood oil is extracted from the woods for us ...

in plantations as a host tree. The tree's flowers provide

forage Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used m ...

for bees, especially when there is enough water available.World AgroForestry Centre
/ref> Mulga is of great economic importance to the Australian

pastoral A pastoral lifestyle is that of shepherds herding livestock around open areas of land according to seasons and the changing availability of water and pasture. It lends its name to a genre of literature, art, and music (pastorale) that depicts ...

industry. Despite containing considerable amounts of indigestible

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'', ...

s, mulga leaves are a valuable

fodder Fodder (), also called provender (), is any agriculture, agricultural foodstuff used specifically to feed domesticated livestock, such as cattle, domestic rabbit, rabbits, sheep, horses, chickens and pigs. "Fodder" refers particularly to food g ...

source, particularly in times of drought, as they are palatable to stock and provide up to 12% crude

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

. The seeds of ''Acacia aneura'' are traditionally used to make

seedcakes Bush bread, or seedcakes, refers to the bread made by Aboriginal Australians by crushing seeds into a dough that is then baked. The bread is high in protein and carbohydrate, and forms part of a balanced traditional diet. It is also sometimes ...

. The

mulga apple The mulga apple is an Australian bush tucker food, often eaten by the Indigenous Australians of Central Australia. The mulga apple is in fact a combination of plant and animal; the insect gall grows inside the wood of the mulga tree ''( Acaci ...

is an insect

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...

commonly eaten by

Aboriginal people Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original people ...

. Mulga tree gum (''ngkwarle alkerampwe'' in the

Arrernte language Arrernte or Aranda (; ) or sometimes referred to as Upper Arrernte (Upper Aranda), is a dialect cluster in the Arandic language group spoken in parts of the Northern Territory, Australia, by the Arrernte people. Other spelling variations are A ...

) is a type of lerp scale found on mulga branches. It provides a tasty,

honey Honey is a sweet and viscous substance made by several bees, the best-known of which are honey bees. Honey is made and stored to nourish bee colonies. Bees produce honey by gathering and then refining the sugary secretions of plants (primar ...

-like treat.

Wood

Wood from ''Acacia aneura'' stands up very well to being buried in soil, so it is used for posts. The wood has a

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

of about 850–1100 kg/m³. It is also good as

firewood Firewood is any wooden material that is gathered and used for fuel. Generally, firewood is not highly processed and is in some sort of recognizable log or branch form, compared to other forms of wood fuel like pellets or chips. Firewood can ...

, and good-quality

charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...

can be produced from it. Mulga is a vital tree to

Aboriginal Australians Aboriginal Australians are the various Indigenous peoples of the Australian mainland and many of its islands, such as Tasmania, Fraser Island, Hinchinbrook Island, the Tiwi Islands, and Groote Eylandt, but excluding the Torres Strait Islands ...

in central and

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 ...

; the wood is a good

hardwood Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...

for making various implements, such as

digging stick A digging stick, sometimes called a yam stick, is a wooden implement used primarily by subsistence-based cultures to dig out underground food such as roots and tubers, tilling the soil, or burrowing animals and anthills. It is a term used in ar ...

s, woomeras, shields and wooden bowls.

References

Notes

General references

* * *

External links

''Acacia aneura'' (ILDIS LegumeWeb)''Acacia aneura'' Photos (FloraBase)''Acacia aneura'' (Google Images)
* {{Taxonbar, from=Q1817001 aneura Flora of New South Wales Flora of the Northern Territory Flora of Queensland Flora of South Australia Acacias of Western Australia Bushfood Forages Plants described in 1855 Taxa named by Ferdinand von Mueller