Stony acacia–cassia–eremophila pastures in the southern rangelands of Western Australia

Page last updated: Wednesday, 19 October 2022 - 2:28pm

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Stony acacia–cassia–eremophila pastures are one of the many pasture types in the southern rangelands of Western Australia. Note that cassias are in the genus Senna.

The Department of Primary Industries and Regional Development provides this pasture information as a reference for assessing pasture condition, and as a guide for pastoral station staff and others interested in the productivity and maintenance of the pastoral rangelands.

Pastoral potential – very low

Rugged terrain and lack of water render some parts of these pastures inaccessible to stock and pastoral value is very low. Shallow soils and poor infiltration limit the establishment of perennial vegetation. Palatable perennials are scarce and durability in dry times is poor.

Suggested levels of use (per annum)

Table 1 provides a rough guide to the range of pastoral values for good condition pastures, which must be checked against conditions in each region and paddock. Carrying capacities for fair condition pastures might be 75% to 50% of good, and poor condition pastures less than 50% of good.

See Introduction to pastures in the southern rangelands of Western Australia for an explanation of how carrying capacities are estimated.

Table 1 Estimated average annual carrying capacity for sandy granitic acacia shrub pastures in good condition
Condition Carrying capacity
Carrying capacity
ha/CU2 (ha/AE3)
Good >30 >210 (≥252)

1 DSE is based on the feed energy required to maintain a 45 kilogram liveweight Merino wether with zero weight change, no wool growth additional to that included in maintenance, and walking 7 km/day. 1 DSE has an energy requirement of approximately 8.7 MJ ME/day.
2 CU in the southern rangelands is based on a 400 kg steer at maintenance and equivalent to 7 DSE.
3 AE is based on the feed energy to maintain a 450 kg Bos taurus steer 2.25 years of age, walking 7 kilometres each day. 1 AE has an energy requirement of approximately 73 MJ ME/day and equivalent to 8.4 DSE.


These pastures are rarely suitable for carrying stock on a year-long basis. At best, they allow sparse grazing at very low stocking rates. Closely spaced water must be available to ensure even grazing pressure. Fencing these pastures off from more attractive pastures will reduce the potential for preferential grazing of higher pastoral value pastures. Flushes of annual species after good seasonal rains can be grazed for the short period that green feed is abundant, which allows managers to spell better quality pastures and promote recruitment of palatable shrubs where fencing is adequate.

Fire is not a management tool for these pastures. In most years, there will not be enough fuel to carry a fire. In wet years, annuals and ephemerals may produce enough fuel to carry a fire.

Pasture condition

Surveys revealed significant patterns of reduced populations of total perennials, with much reduced populations and species counts of palatable perennials in areas close to waters (within 1–3km). Areas showing a reduction in palatable perennial plant coverage and a general loss of acacias from mid and upper strata may exhibit compensatory increases in cover from unpalatable eremophilas.

Survey data generally indicate stony acacia-cassia-eremophila pastures often remain in relatively good condition, with deterioration occurring slowly only after intense grazing pressure. Water availability for herbivores, in particular sheep, is an important factor influencing degradation. The Murchison River catchment survey found that nearly half of the surveyed points for these pastures were in poor condition and that palatable perennials averaged significantly less in the north-east quadrant of paddocks than elsewhere. This observation suggests sheep grazing pressure was particularly focused in the north-eastern sectors of paddocks.

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See Figure 1. The density and vigour of palatable perennial shrubs indicates the condition of stony acacia-cassia-eremophila pastures. Palatable perennials are generally sparsely distributed and cotton bush is the dominant species; however, warty-leaf eremophila, ruby saltbush, golden bluebush, tall saltbush and currant bush are all important locally. The presence of any of these species as healthy robust individual plants indicates good condition.

Total low shrub densities are commonly around 1500 per hectare but may vary between 600 and 4000/ha according to soil type and depth. Species of marginal palatability usually dominate the stand with grey cassia, crinkle leaf cassia and royal poverty bush occurring widely. Bardie bush, wait-a-while and needlebush may occur at densities below 50 plants per hectare.

Dense stony mantles usually provide some degree of protection to the shallow soil.


See Figure 2. Cassias and poverty bushes are dominant, similar to good condition pastures. The major distinction is a reduction in density or absence of living palatable perennial plants. Gully erosion is absent but sheet erosion may occur after heavy rainfall.


See Figure 3. Desirable species are absent and even the marginally palatable species remaining are grazed; there is an overall decline in density and diversity. Pastures are characterised by bare stony ground with only a few individual shrubs remaining. Rilling or gully erosion may be present, particularly in areas where stock pad lines have disturbed the surface mantle.

Stony acacia–cassia–eremophila pastures condition photographs

Photograph of a stony mulga short grass forb community in good condition
Figure 1: A stony mulga short grass forb community in good condition. The combined desirable low shrub (golden bluebush and cotton bush) density is 1,200 plants per hectare (12/100 m2). The site is on the crest of a gently undulating plain in the Thomas land system.
Photograph of a stony short grass forb community in fair condition
Figure 2: A stony short grass forb community in fair condition. The only desirable low shrub is cotton bush at 1,000 plants per hectare (10/100 m2). The site is on the upper slope of an undulating rise in the Fossil land system.
Photograph of a stony short grass forb community in poor condition
Figure 3: A stony short grass forb community in poor condition. The combined desirable low shrub density (bluebushes, tall saltbush and cotton bush) is 232 plants per hectare (2/100 m2). The site is on a level plain in the Three Rivers land system.

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Vegetation structure and composition

Stony acacia-cassia-eremophila pastures typically occur as very scattered or scattered (PFC 2–15%) low (<2m) shrublands. Upper strata are very sparse or absent. Trees occur rarely and sparse tall shrubs may include mulga, curara or other acacias. Low shrubs form the dominant layer, although they are relatively sparse and contain fewer desirable species when compared with the similar, and often adjacent, acacia-cassia short grass forb pastures.

Common low shrubs include Murchison willow, grey cassia, crinkle leaf cassia, grey turpentine bush, limestone fuchsia, royal poverty bush, cotton bush and flannel bush. These pastures can also occur as tall (>2m) scattered (10–20% PFC) shrublands in restricted areas where mulga and curara are the dominant tall shrubs. Perennial grasses are generally absent and do not form an important component, though some may be present in creeklines and on open plains. Annual grasses and herbs provide considerable cover for a limited time in good seasons.

Occurrence estimate: 3.51Mha, 4.3% of the southern rangelands

Stony acacia-cassia-eremophila pastures occur on broad convex rises among undulating upland stony plains and near level interfluvial plains, and cover an estimated 3.51 million hectares (4.3% of the southern rangelands). Some small remnant plateaux also support these pastures. The soils are usually shallow (<60cm) red lithosols with sandy or loamy textures throughout the profile, though uniformly fine-textured and texture-contrast soils occasionally occur.

Surface mantles are a common feature and fragments of quartz, mixed or gneissic material often provide a dense cover (>50%). These pastures are often associated with hardpan mulga shrubland pastures, occurring in the landscape below them, as the interfluvial plains grade into adjacent sheetwash plains.

Map of estimated distribution of stony acacia-cassia-eremophila pastures  in the Southern Rangelands
Figure 4: Map of estimated distribution of stony acacia-cassia-eremophila pastures  in the Southern Rangelands

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Associated plants

Table 1 Common and important species of stony acacia-cassia-eremophila pastures

Common name

Scientific name (links to FloraBase)



Eremophila longifolia



Maireana spp.


Cotton bush

Ptilotus obovatus


Curly windmill grass

Enteropogon ramosus


Currant bush

Scaevola spinescens


Golden bluebush, George's bluebush

Maireana georgei


Horse mulla mulla

Ptilotus schwartzii


Ruby saltbush

Enchylaena tomentosa


Scrambling saltbush

Chenopodium curvispicatum


Tall saltbush

Rhagodia eremaea


Tall sida

Sida calyxhymenia


Warty-leaf eremophila

Eremophila latrobei


Wilcox bush

Eremophila forrestii


Bardie bush

Acacia synchronicia/A. victoriae



Senna artemisioides subsp. oligophylla


Broom bush

Eremophila scoparia


Crinkle leaf cassia

Senna artemisioides subsp. helmsii


Desert cassia

Senna artemisioides subsp. filifolia


Grey cassia, desert cassia

Senna artemisioides subsp. x coriacea


Grey turpentine bush

Eremophila macmillaniana


Limestone fuchsia

Eremophila sp.



Hakea preissii


Royal poverty bush

Eremophila cuneifolia


Sandbank poverty bush

Eremophila margarethae


Spoon-leaf eremophila

Eremophila spathulata


Straight leaf cassia, variable cassia

Senna artemisioides subsp. x sturtii


Turpentine bush

Eremophila fraseri



Acacia cuspidifolia


Bowgada, wanyu, horse mulga

Acacia ramulosa



Acacia tetragonophylla


Fine leaf jam

Acacia burkittii


Flannel bush

Solanum lasiophyllum


Gidgee, yalardy

Acacia pruinocarpa


Granite poverty bush

Eremophila platycalyx



Acacia acuminata



Acacia grasbyi



Acacia aneura


Murchison willow

Acacia demissa


Poverty bush

Eremophila alternifolia


Western myall

Acacia papyrocarpa


White cassia

Senna glutinosa subsp. pruinosa


Royal mulla mulla

Ptilotus rotundifolius


* D = desirable, U = undesirable, I = intermediate, N = no indicator value, ann. = annual

Contact information

Joshua Foster