Reading the rangeland: a guide to the arid shrublands of ...

Digital Library Digital Library

All other publications Miscellaneous works

1995

Reading the rangeland: a guide to the arid shrublands of Western Reading the rangeland: a guide to the arid shrublands of Western

Australia Australia

Don Burnside

Alec Holm

Alan Payne

Georgina Wilson

Follow this and additional works at: https://researchlibrary.agric.wa.gov.au/pubns

Part of the Environmental Education Commons, Environmental Indicators and Impact Assessment

Commons, Environmental Monitoring Commons, Natural Resources and Conservation Commons, Natural

Resources Management and Policy Commons, and the Other Earth Sciences Commons

Recommended Citation Recommended Citation Burnside, D, Holm, A, Payne, A, and Wilson, G. (1995), Reading the rangeland: a guide to the arid shrublands of

Western Australia. Department of Primary Industries and Regional Development, Western Australia, Perth. Book.

This book is brought to you for free and open access by the Miscellaneous works at Digital Library. It has been accepted for inclusion in All other publications by an authorized administrator of Digital Library. For more information, please contact [email protected].

https://researchlibrary.agric.wa.gov.au/

https://researchlibrary.agric.wa.gov.au/pubns

https://researchlibrary.agric.wa.gov.au/misc

https://researchlibrary.agric.wa.gov.au/pubns?utm_source=researchlibrary.agric.wa.gov.au%2Fpubns%2F2&utm_medium=PDF&utm_campaign=PDFCoverPages

https://network.bepress.com/hgg/discipline/1305?utm_source=researchlibrary.agric.wa.gov.au%2Fpubns%2F2&utm_medium=PDF&utm_campaign=PDFCoverPages








mailto:[email protected]

143

A guide tothe arid shrublands

of Western Australiaby Don Burnside, Alec Holm,

Alan Payne and Georgina Wilson

1

by Don Burnside, Alec Holm, Alan Payne and Georgina Wilson

Reading theRANGELAND

A guide to the arid shrublandsof Western Australia

Supported by the

2

First published in 1995 byDepartment of Agriculture3 Baron-Hay Court, South Perth, Western Australia 6151© The Chief Executive Officer of the Department of Agriculture, Western Australia, 1995

National Library of AustraliaCataloguing-in-Publication data

Reading the rangeland: a guide to the arid shrublands of Western Australia

Bibliography.Includes index.IBSN 0 7309 6464 7.1. Arid regions - Western Australia - Management. 2. Range management - Western Australia.3. Range plants - Western Australia. 4. Range ecology - Western Australia.I. Burnside, Donald Grosvenor, 1950-. II. Western Australia. Dept. of Agriculture.

333.7409941

Designed by Rodney D. LewisCover photographs by Richard Woldendorp of Photo Index and Andrew MitchellTypeset in 11pt TimesColour separations and prepress by Type FoundryPrinted by Frank Daniels Pty Ltd

3

ContentsPage

Background to authors 4

Acknowledgments 5

Foreword 7

Chapter 1 - Introducing the arid shrublands 9

Chapter 2 - Soil and vegetation processes 16

Chapter 3 - Main types of country 31

Chapter 4 - Mulga Shrubland 38

Chapter 5 - Saltbush and Bluebush 57

Chapter 6 - Sandplain 104

Chapter 7 - How the land is managed 124

Glossary of technical terms 130

Common names of plants in this manual 133

Botanical names of plants in this manual 137

Further reading 140

4

epartment of Agriculture senior adviser Don Burnside has spent most of hisworking years based at Kalgoorlie and Carnarvon in the WA arid shrubland. In theselocations he was involved with rangeland research and extension activities, in

particular the establishment of land conservation districts in the pastoral areas. He recentlycompleted post-graduate studies in Agricultural Extension at the University of Queensland.

Alec Holm has been working in the rangeland since 1968 based in the Kimberley andGascoyne. He has also worked in Nigeria and is currently involved in an FAO project in Iran.Alec holds a Master of Agricultural Science degree from the University of Western Australiaand has published many scientific papers on his research work in the rangelands. He iscurrently the senior adviser managing the soil and vegetation monitoring program in therangelands.

Alan Payne is the senior adviser leading the Rangeland Survey Group within theDepartment of Agriculture and has been actively involved in studying and surveying theoutback areas of Western Australia for many years. He has an unparalleled experience inAustralia in this work and has co-authored several of the detailed surveys of the rangelandwhich helped provide background material for this book.

Georgina Wilson is a journalist with a healthy curiosity about the rangeland, and adetermination not to become confused by technical jargon. Since graduating in AgriculturalScience from the University of Western Australia she has worked in WA, interstate andoverseas in broadcasting, newspapers and other communications media.

Background to authors

5

Acknowledgmentsompilation of this book would have been impossible without assistance from manypeople both inside and outside the Department of Agriculture, Western Australia. Theseincluded:

• National Landcare Program for generous financial support.

• Peter Curry for initiating the project.

• The patient members of the Rangeland Survey Team, particularly Hugh Pringle,Sandra Van Vreeswyk and Peter Hennig, for supplying information, reading drafts,chasing photographs and helping pull us back to reality.

• Philip Thomas for organising maps and other cheerful assistance.

• Department of Agriculture staff in the rangelands, notably Roderick O’Connor(Meekatharra), Julia Mattner and Geoff Carter (Kalgoorlie), Ian Watson and JohnStretch (Carnarvon).

• Pastoralists who ‘road-tested’ early text and possible photographs, sometimes debatingour conclusions at great length into the night, and offering practical suggestions andhospitality. Particular thanks to Tony Crook, Len Boladeras, Bob Symonds, Ted andMeg Officer, Geoff Lacy, Tom Seaman and Peter Brown.

• David Tongway from CSIRO Wildlife and Ecology in Canberra, for his enthusiasm,encouragement and the use of photographs and drawings.

• Ron Hacker from the NSW Department of Agriculture at Dubbo.

7

Forewords a farmer, I welcome this publication that can help translate detailed scientificresearch to the people who will benefit most.

Managing the rangelands is complex. Soils and vegetation can vary considerablyover short distances in distinct or subtle ways. Separating climatic from managementinfluences on the condition of the land has always been difficult.

Whether we live on a sheep station, in a country town, in an Aboriginal community, a miningcamp, or even if we only visit the Australian outback, it is vital that we understand andappreciate the unique character and management requirements of the rangelands. This bookfunded by the National Landcare Program will contribute to that understanding.

Much of our vast arid shrubland has only been settled by Europeans for just over a centurycompared with thousands of years of Aboriginal involvement. Consequently, ourunderstanding of its unique landscape and processes is still evolving. Learning to ‘read therangeland’ has been a slow process, involving the knowledge and skills of pastoralists,Aborigines and scientists. In particular, the Resource Inventory and Condition Surveyscommissioned by the Government since the late 1960s have given present and future users anexcellent body of knowledge to guide management. I acknowledge the efforts made bypeople in the Departments of Agriculture and Land Administration in mapping anddescribing the soil and vegetation in the arid shrubland areas.

Reading the rangeland has been prepared by an experienced team involving technical expertsin rangeland management and publication. It was also ‘road tested’ by a diverse group ofleading pastoralists and others with love for and interest in the country. I believe the final textmelds the ideas from both these groups in a way that both new and old users of the rangelandwill find fascinating.

I commend it to you.

Monty House MLAMINISTER FOR PRIMARY INDUSTRY

9

Chapter 1 - Introducing the arid shrublands

time and subsequently, considerabledamage was often wreaked unwittingly onsome areas of land. Most new settlers, forexample, knew little about the rangelandonto which they were releasing their herdsof cattle and flocks of sheep. Its grassesand herbs varied from those found in otherparts of Australia and were radicallydifferent from those known in Europe. Itsshrubs were also new but the stock soonfound which were more palatable. Ifstocking rates were excessive, particularlyaround rivers and other water sources, fewpastoralists would have understood thelong-term damage before the most

hen most people think ofAustralia’s outback they oftenvisualise the arid shrublands —

endless red-brown plains as far as the eyecan see, perhaps broken by an occasionalrange of low hills, scantily clothed instunted mulgas casting their shade overgrey-green shrubs and dry grasses.

In Western Australia, such lands stretchfrom the Indian Ocean between Kalbarriand Exmouth in a broad arc through theGoldfields to the Nullarbor and theSouthern Ocean. They cover about 850,000square kilometres bounded by the 23° lineof south latitude to the north, the drierdesert country in the north-east, and to thesouth by the agricultural areas where morereliable and more generous rainfallencourages landowners to plant and harvestcrops.

These shrublands, often known as ‘pastoralcountry’ or ‘station country’ becausepastoral leases occupy 85 per cent of thearea, were first opened for Europeansettlement in the 1870s. Towards the end ofthe nineteenth century gold discoveriesstimulated further interest, and by 1910most of the suitable grazing country hadbeen allocated to pastoralists.

Grazing of sheep for wool expandedsteadily as new settlers took advantage ofthe large tracts of land available, and sheepnumbers peaked in the 1930s. During this

Meekatharra

Kalgoorlie

PERTH

Carnarvon

10

palatable species were eaten out or tramplinghad led to soil erosion.

Mining also had a major impact on thelandscape from an early stage, particularlyon the vegetation of the Murchison andGoldfields. Timber was harvestedextensively for fuel and building purposes.Meat, dairy and draft animals needed forageand soon made use of the more palatablelocal shrubs and grasses close to miningsettlements.

Population of the rangelands is now verylow, mostly pastoralists, Aborigines andminers, but the very emptiness of the countryis an attraction to many seeking an escapefrom the cities, or a wilderness experience.

Some stations now offer accommodation totravellers and tourists, ranging frombedrooms with private facilities within thehomestead to self-contained cottages,shearers quarters and caravan parks. Guestsmay have the opportunity to becometemporary station hands, go bush walking,bird watching and sight seeing.

The main tourist season is in the coolermonths from May to October and details ofaccommodation can be obtained from localand city tourist offices, motoringorganisations and accommodation guides.

Though rainfall in the WA shrublands iscomparable to that experienced in otherfamous rangelands of the world such as theTexas plains or parts of north Africa, itsreliability here is lower. The most reliablerainfall occurs in the winter, the result of

rain-bearing depressions that stray northand eastward from the agricultural areas,but the heaviest rainfall events frequentlyresult from tropical cyclones in summer.

In the Murchison for example less than 20per cent of rain normally falls in summer,making the winter rain the most importantfor stock and vegetation. While raw rainfalldata are frequently used as a gauge ofseason, more sophisticated measures nowavailable consider the effects of bothrainfall and evaporation rates. For the aridshrublands a dry winter season (May toOctober) is considered to have less thantwenty five consecutive days suitable forplant growth while a wet winter has at leasta seventy five consecutive days suitable forgrowth.

Seasons in selected shrubland centres in 80 years from 1914 to 1993

Centre No. of No. of dry winters wet winters

Gascoyne Junction 18 15Meekatharra 33 14Leonora 23 16

Considering the records from threerangeland centres, it can be seen that somevery dry winters are inevitable, even closeto the coast. In the eighty years from 1914to 1993 Gascoyne Junction for example hadeighteen dry winters while further inlandthere were even more.

C H A P T E R 1

11

I N T R O D U C I N G T H E A R I D S H R U B L A N D S

Meekatharra

Kalgoorlie

Carnarvon Gascoyne Junction

Leonora

Wet winter

Average winter

Dry winter

1914

1921

1924

1933

1940

1945 1953

1957

1973

1975

1992

1943 1960

1962

1986

19801926

1931

1938

1947

1951

1914

1921

1924

19351938

1941

19451946 19

55

1973

1976

1993

1943 1961

1963

1970

1989

19801978

1914

1925

1930

1935

19371940

19441946

1949 1955

1959

1974

1976

1980

1990

1978

1952

1966

1983

1916

1929

1949

1964

1966

1989

1917

1919

1932

1942

1951 1953

1963

1965

1970

1984

1992

Gascoyne Junction

Leonora

Meekatharra

12

C H A P T E R 1

Sturt’s desert pea is one of the many attractive wildflowers that bloom in the shrublands in good seasons andattract the attention of travellers.

At Meekatharra four winters occurred inwhich the soil water store was neversufficient for plant growth on even fiveconsecutive days. One of the worst periodswas during the 1930s and 1940s, althoughthe late 1970s were also very dry.

All three of these centres experiencedextremely dry winters in some years, but atother times they fared differently due to thedifferent paths and intensity of the rainfallpatterns.

A wet winter season followed by goodsummer rain can produce a relativelyluxuriant growth of grasses and other plantsvery quickly, but successive dry seasons,which occur more frequently, result in fewnew plants and heavy pressure on existingvegetation from both native fauna andintroduced stock.

“It’s a wonderful season in the north. Thewildflowers look fantastic,” may be afrequent comment from travellers, but thecolourful everlasting daisies and otherannuals are poor indicators of the truecondition of the country. A little winter rainand ephemeral plants such as theeverlastings will germinate, mature and setseed within a very short time. But in drieryears after their remains have been whirledaway by the scorching, summer windleaving only bare soil surface, it will be theless eye-catching perennial grasses andshrubs which provide food for both stockand native fauna and lasting protection forthe soil.

Adaptation of some shrubs to these hot aridenvironments can be truly amazing. Even inlate summer when conditions are most

13

which explains their absence from the aridshrublands.)

All arid zone perennial shrubs have a highregeneration rate after defoliation whichmay result from grazing, fire or drought.(In fact defoliation may be a survivalmechanisms for some shrubs in prolongeddry periods. If they have no leaves, theyneed not continue photosynthesis!) But ifshrubs face a second defoliation soon afterrecovery from the first (perhaps due toheavy grazing), they often fail to survive.

Grazing by introduced animals issometimes considered to be universallyharmful to natural vegetation, but this isnot necessarily true. Heavy grazing by bothnative and introduced animals can certainlyremove palatable plants and tilt the balancein favour of less palatable species butlower levels of grazing pressure may do noharm or even benefit vegetation. Twentythree years after exclosure of a site atCoodardy near Cue the species diversitywas actually lower than on a similar grazedarea. However, in other cases exclosure hasresulted in increased species richness.

After more than one hundred and twentyyears of settlement in some areas of WA’srangeland, understanding of theinteractions between plants, animals, soilsand climate is still incomplete. This is dueto the complexity of the environment andthe relatively short period of scientificinquiry.

severe they continue, not only to survive,but produce food material. For example, theoptimum temperature for photosynthesis forthe berry saltbush is more than 37°C and itsheat resistance limit is 59°C. Values for hopmulga are only slightly lower.

With rainfall so irregular, plant communitieshave become very diverse because no singleset of survival strategies will remainsuccessful over long periods. Slow growing,deep-rooted plants are better able to survivelong droughts and to make better use ofwater than fast growing, shallow-rootedannual grasses or herbs but are lesscompetitive as seedlings. Short-lived plantsgrow faster, invest less energy intoproducing roots, but are less droughttolerant. This means that without influencefrom man or other animals the mix andhierarchy of species can change fairlyquickly.

Long-lived deep-rooting perennials tend todominate regions with intermittent rain andlow fertility but their regeneration may beirregular. Pearl bluebush plants for exampleare believed to have a lifespan of up to threehundred years but good establishment mayonly occur every twenty or thirty years inthe right combination of conditions. But thepassage of a deep rain-bearing depressioncan turn drought-stricken country into agarden almost overnight as perennialgrasses respond with new green shoots, andannual herbs and grasses germinate veryquickly. (Succulents that store water in theirstems such as cacti, require regular rain,


14

C H A P T E R 1

Official knowledge about the rangeland hasaccumulated slowly. The CommonwealthScientific and Industrial ResearchOrganisation (CSIRO) began mapping theWA rangelands in the 1950s but these firstsurveys were concerned mainly with broadscale description, without assessing rangecondition.

The Western Australian Department ofLands and Surveys began its own surveysin the 1960s and prepared maps showingbroad classification of pasture types. Themain use was to define land degradationand estimate paddock and station carryingcapacities for the pastoral industry.

More recently, detailed rangeland surveysof certain regions have been completed andreports published by the Department ofAgriculture (DAWA) and the Department ofLands and Surveys (now known asDepartment of Land Administration,DOLA). These began with a report on thecondition of the Gascoyne Catchment,commissioned by the Pastoral Board in1969 after a series of damaging floodsaffected the Carnarvon townsite. Morerecent surveys have included parts of theWA Nullarbor Plain (1979), the AshburtonRiver Catchment (1983), the CarnarvonBasin (1987), the Murchison (1994) and thenorth-eastern Goldfields (1994).

Overgrazing by feral and domestic animalshas been a common cause of landdegradation, frequently involving the mostproductive areas of fragile alluvial country

Rangeland condition can be consideredfrom two viewpoints: short-termseasonal condition and long-termcondition. Seasonal conditions relate to therelative abundance of short-lived plantsthat thrive in favourable conditions aftergood rains.

On a year-round or longer basis, animalscannot survive on seasonal growth alonebut require long-lived vegetation as well.In general terms, long-term condition isalmost independent of season but dependson grazing pressure, major climatic eventsand sometimes fire.

In good seasons, long-term condition isoften not a major influence on animalproduction. Indeed, some degraded areaswith reasonably healthy soil can producelarger amounts of forage than similarcountry in good condition. But it is duringthe inevitable dry spells that good long-term condition becomes vital – providing areadily available, if less attractive, sourceof perennial vegetation to protect the soiland succour its inhabitants.

New species of plants are still beingdiscovered and even major species such asthe mulga may be subdivided into newsub-species as distinctly different formsare revealed. Read a scientific descriptionconcerning rangeland plant species fromten or twenty years ago and severalbotanical names are sure to differ from thelatest publications.

15

because it was close to water. Over fivesurvey areas (Murchison, Gascoyne,Nullarbor, Ashburton and Carnarvon) about40 per cent of land was estimated to be ingood condition, a third in fair condition andjust over a quarter in poor condition basedon its potential for long-term sustainablepastoral production. The proportions variedconsiderably in different areas, with lessthan 10 per cent in poor condition in theAshburton but more than 40 per centdegraded to poor in the Murchison andNullarbor. However, on the Nullarbor thechange was caused by the effects of rabbitsand fire rather than domestic stock.

Rangeland monitoring using large scaleaerial photography was begun by DAWA inconjunction with CSIRO in 1970. Today,satellite imagery is combined with closerange ground data from seventeen hundredpermanent sites, helps to provide valuableinformation for both the government andpastoralists to aid future management. Withevery year the knowledge bank on thisunique area is growing, but much remainsunclear. It is important that we conserve theland for long-term sustainable pastoralproduction and other uses, and learn how toovercome past mistakes.

Modern mining operators are also makingfar fewer mistakes than the pioneers. Bylaw, companies must rehabilitate land as anintegral part of their operations. But miningdoes bring people, and the control of peoplecan be difficult. Uncontrolled access to landby off-road vehicles – four-wheel drives and

trail bikes – plus the lighting of bushfirescan damage land surrounding miningcommunities very easily.

Tourists too, travelling through country fora few brief days or weeks, may not realisethe impact they could have on what seemsa very tough environment. For example, awheel rut cutting through a crusted soilsurface can lead to an erosion gully,diverting natural water flow and resultingin water starvation of many hectares ofcountry. No wonder then that touristaccommodation for those wanting to seeAyers Rock (Uluru National Park) in theNorthern Territory is now sited well awayfrom the rock itself.

Any land manager is flying blind withoutan understanding of the processes that areshaping the landscape and its vegetation.Natural processes involving water, windand occasionally fire occur continually.Very little may happen for a long time,followed by sudden changes in the balanceor survival of species caused by very wetor very dry years.

If soil is lost from rangeland througherosion, it is effectively lost forever asnatural weathering of rocks and new soilformation are extremely slow. If plantspecies are lost or the structure and densityof the vegetation is permanently altered,the character of a whole area can change.There are seldom second chances when wemake mistakes!


16

Chapter 2 - Soil and vegetation processesseasons may still result in permanentchange in the vegetation as moreaggressive colonisers such as annualgrasses or unpalatable shrubs gain moreadvantage from regeneration opportunities.

Soil moisture is normally the limitingfactor for plant growth. Soil fertility tendsto be secondary, although most WArangeland soils are inherently infertile.(Phosphorus and nitrogen levels forexample are less than half of the averagefound in arid zones of other continents.)Rangeland soils support comparativelysparse vegetation, which in turn supportslow populations of animal life.

And while a general area may receive 200millimetres over a year, the effectiverainfall can be much less or much more forindividual patches in different parts of thelandscape. A stony hill for example mayonly absorb half of the rain that falls on itbecause the other half runs away down theslope. Meanwhile at the foot of that slope,small depressions may receive theequivalent of 600 millimetres – their ownbasic 200 millimetres plus double this inrun-off from surrounding slopes. The resultis a dramatic difference in ability tosupport vegetation and hence animal life.

Structures such as roads, a mine dump oreven a stock pad may affect the naturalflow of water across the land after rain.Instead of gentle sheet flow with much of

estern Australia’s shrublands havemany similarities with rangelandelsewhere such as the Russian

steppes, the veldt of South Africa and theplains of America, but tend to be moreancient, less fertile and flatter than most.They are distinctive for their red soils,caused by the presence of iron oxide – avaluable resource exploited further north.Average annual rainfall ranges from 150 to250 millimetres, but can vary enormouslybetween seasons both in distribution andamount. The statistics themselves can alsobe misleading as a few very high rainfallyears can boost the long-term average,while actual falls are much less in mostyears.

In agricultural areas the annual pattern ofrainfall is familiar to all and essential tocrops and herds alike. In the rangelands, theseasons matter less, and it is the climaticevents that are vital – events such as a deeprain-bearing depression or tropical cyclonebringing heavy rain in a very short time.Such events can result in a huge pulse ofregeneration of both plant and animalcommunities which declines slowly overyears or even decades. Similarly, successivedry years may result in loss of manyindividual plants and even particularspecies from certain areas. Depending onthe depletion of the seed bank and the soilloss through erosion, return of better

17

depressionalluvial plain

salt lakeriver or creek

gentle slope

stony hill

the water being absorbed as it moves slowlyacross the plain, a man-made bank mayresult in ponding on one side and drierconditions on the other.

Water starvation is often apparent whendriving through the shrublands, reflected bysmaller and more scattered shrubs on thedownslope side of the road. Where wateronce flowed gently across the landscape,road construction, even a simple gravel road,causes some flow to be diverted along theroadway to the detriment of the areas downthe slope. Within a couple of years thebalance of plant species in both these areaswill alter with corresponding changes in thenumbers of insects, micro-organisms andsmall animals.

It’s the ‘rich get richer and the poor getpoorer’ syndrome. The better the conditionof an area of land, the more effective it canbe in trapping and retaining scarce resourcesand therefore able to retain or even improveon that condition. On a soil in good condition

a fall of 15 mm of rain may be sufficient tostart plant growth, but at least 30 mm maybe needed on degraded soil where water ispoorly absorbed so less is available toplants.

Existing vegetation and its associated litteris also able to conserve precious moistureby shading and mulching effects on the soilsurface. These help maintain suitableconditions for further plant growth evenunder the harshest conditions. And thehealthier and more diverse the plantcommunity, the greater the protection andstabilisation for the ground below andaround it. Shade and shelter from existingvegetation helps create a niche forgermination of more plants and so thoseprocesses continue.

Temperature of the ground is also affectedconsiderably by the presence of vegetation.Exposed soil surfaces experience muchgreater extremes of both heat and cold thanthose protected by vegetation. On hardpan

A typical landscape in the arid shrublands.

S O I L A N D V E G E T A T I O N P R O C E S S E S

18

find food and shelter within the plantcommunity then fertilise the ground andfurther benefit the plants.

But if land loses its vegetation, the surfacebecomes more vulnerable to both water andwind, and likely to lose more soil andnutrients which are concentrated in the top5 to 10 centimetres. Penetration of rain thendeclines and the whole system can degradeeven further. And once a soil surface isworn smooth and sealed by the action ofeither wind or water or both, its ability to

Growth of one vigorous shrub often provides sufficient protection from both animals and the elements forsuccessful establishment of other plants close to its base. Clumps of three or four different species growingtogether are very common. Very palatable species often survive only where protected by other species that areless attractive to grazing animals.

plains the summer temperature beneath atree may be 40°C, but could build to 60° or70°C a few metres away on an exposedstony surface.

Local recycling is also important. Leaves,twigs, pieces of bark, flowers and seedsdrop continually from existing plants, andeventually break down to provide nutrientsfor other plants (or even the same plant if itlives long enough) and soil fauna. And thedroppings from the grubs, caterpillars,grasshoppers and other tiny animals which

C H A P T E R 2

19

High infiltration

Low levels of nutrient cycling

Low infiltration Concentrated litter fall, and high levels of nutrient cycling

Intergrove area with sparse vegetation

Grove of dense vegetation

Water and nutrient flow down slope

trap and incorporate even small amounts oforganic matter and water declines evenmore. It then becomes less fertile and veryinhospitable for seedling establishment.

Diversity is extremely important for long-term survival of a community of plants asindividual species react differently toopportunities and stresses. A light fall ofrain for example might do nothing for aparticular grass species except wash the dustfrom its leaves – certainly not produce newgrowth. But the same fall might be a usefulbonus for lichens growing on the surfaceand helping to bind the soil.

Similarly, some species of perennial grasseswill produce succulent green shoots fromlight falls of summer rain while other plantsmake their best and most useful growthduring winter. Important palatable shrubssuch as currant bush lose their leaves after

periods of moisture stress but resprout afterrain, springing to life from apparent death.Maintaining a mixture of species helpsensure that at least some vegetation willsurvive the extremes of climate and thisgives the system resilience.

Some country tends to be very resilient andcan recover fairly easily after majordisturbance such as overgrazing or drought.Other land has little resilience, so thatchange tends to be more permanent.Examples of resilient country include thebluebush communities on the plains nearKalgoorlie and Carnarvon. This resilienceis due to their very flat topographycombined with plant species that are bothlong-lived and resistant to grazing.

In contrast, alluvial plains adjacent tomajor rivers have much less resilience. Ifvegetation is removed, erosion is almost


Water and nutrient movement through groves in the arid shrublands.

20

inevitable and the soil fertility and the land’scarrying capacity are reduced permanently –at least in human time scales. After a fewthousand years there might be significantrecovery through new soil formation, but thatis pretty irrelevant for most of us.

Landscape processesWhen country is healthy, which usuallymeans supporting vegetation close to itspotential, the soil, water and nutrientsessential for life are conserved and recycledfor use within the system. A small amount ofwool, meat or other products may beharvested from the range, but the naturalprocesses such as nitrogen fixation byleguminous plants such as acacias andcassias and weathering to providephosphorus and other minerals, ensures thatthe system is self-perpetuating.

When rangelands are only in fair condition orworse, they tend to lose material (soil,nutrients, organic matter) through water andwind erosion and cannot recapturereplacement. In poor condition, even ifgrazing pressure is relieved, land recoverycan be long and arduous – if it happens at all.

Where land degradation does occur, theextent will depend on the soil type and theposition in the landscape. While oneparticular soil type would be quite stable todisturbance in a hollow or on a flat plain, itmight be far less resilient facing the erosivepower of water flowing down a slope.

One of the striking aspects of rangeland isthe existence of fertile patches in otherwise

less fertile surrounding country. Thesepatches may be a relatively small part ofthe whole landscape but responsible for alarge proportion of vegetative growth overtime. Each country type has a characteristicpattern of patches and any reduction intheir number and size is a sign ofdeterioration.

In mulga shrublands the fertile patch is adistinctive grove, obvious for its taller andthicker trees and shrubs compared with theareas between groves. As the vegetationbetween thickets deteriorates, the thicketsprobably receive additional run-on water,but the areas between are eventually leftbare. As the degradation process continues,the thickets themselves lose the capacity totrap run-on water so that water flowthrough the thicket increases and bothwater and nutrients pass unhindered andunused through the landscape.

Arid vegetation is well adapted to theclimate. The structure of some trees andshrubs allows them to channel rain downthe trunks and into the root zone belowmaking the most of any showers. Mulgasfor example can capture 40 per cent of therain that falls on their canopies as stemflow. This contrasts with the ‘drip line’below other trees which marks the outsideperimeter of the foliage above the ground.

The absorption of moisture into the soil ismuch greater around and beneath existingplants. In a trial near Carnarvon theinfiltration rate beneath bluebush shrubs

C H A P T E R 2

21

was found to be ten times that occurringbetween the shrubs. Similarly, underperennial grass tussocks such as woolly buttthe infiltration rate can be four times greaterthan in the areas between tussocks. If thetussocks are not present to hold and improvethe soil, much of the rain falling on theground just flows away and evaporates.During relatively light showers of rain grassmounds tend to absorb all the rain, whilebetween the tussocks the water pondsquickly and runs away.

In vegetation dominated by low shrubs orgrasses the individual plants tend to formthe fertile patches. This is very apparent in

the saltbush and bluebush plains whereindividual shrubs create bush mounds ofaccumulated dust, sand and litter beneathand around themselves. The older and moreestablished the plant, the larger and deeperthe mound and probably the larger andmore varied the associated populations ofinsects, lizards and other small animals.Their burrowing activity then adds to thenetwork of small channels in the soil,increasing the infiltration of water.

Mounds are topdressed with litter from theshrubs or grasses above which providesshelter and food for small animals andgradually decomposes and is incorporated

Cotton bush is regarded by many as an important indicator species, particularly in mulga country. It is fairlypalatable to stock, but its numbers are likely to be highest after loss of other more sensitive indicator plants.Individual plants can live for many years and tend to form mounds around their bases.


22

Low levels of nutrient cycling. Poor return of lost materials

High infiltration on bush mounds.

Small animals and micro-organisms active

Low infiltration between plants

Wind erosion and deposition

Tightly controlled litter fall, breakdown and cycling of nutrients

into the soil. Concentration of nutrientsessential for plant growth such asphosphorus and nitrogen is also muchgreater in the first centimetre of soilbeneath plants in the mounds than outsidethe mounds.

The mounds are able to capture and holdboth soil and water moved from other areasof the landscape. They tend to attract newlitter on the upslope side and lose from thedownslope side, so these are the aspects toexamine to determine whether mounds areextending or diminishing.

Some plant shapes are more effectivetrappers of litter than others. The leasteffective would be the icecream cone-shaped shrub which does little better than atelegraph pole. Wind swirls around its basewhipping away loose grains of sand plusany leaves, twigs or fruit that fall fromabove. The most effective trappers are thoseplants which branch low and spread over

the ground such as some saltbushes andbluebushes, blocking the wind and slowingblow and flow of material by wind orwater.

Particularly on deeper soil, a mound maybe occupied by one shrub and then attractseveral others. What at first glance appearsto be a single plant may really be multipleplants of the same species or three or fourdifferent species taking advantage of theprotection from wind and grazing animals,extra shade, moisture and greater fertility.In heavily grazed areas, many palatableplants such as the bluebushes may surviveonly where protected by larger, lesspalatable long-lived shrubs such asneedlebush.

Scientists often describe the fertile moundsor fertile grove areas as ‘sink zones’ intowhich flow resources such as soil particles,water and litter from other ‘source zones’.

The capture of water and nutrients by fertile bush mounds.

C H A P T E R 2

23

Where the fertile patches are individualmounds the distance between mounds canprovide a guide to range condition. In asaltbush plain in good condition, moundsmay be only 1 to 3 metres apart, but couldbe separated by 4 to 6 metres of bareground where condition is poorer.Comparing the number of bush mounds in acertain area gives an indication oflandscape health. Individual mounds mayhave a life of fifty years or more dependingon the life spans of their resident plants, butif the shrubs die and the mounds are notrecolonised, they are gradually erodedaway. The number of remnant bush moundsis another useful indication of rangecondition. Like empty houses in aneighbourhood, empty mounds are not anencouraging sign.

The amount of litter and its distribution isanother pointer to the health of any system.If the litter (leaves, seeds, sticks, feathers,animal droppings) is being activelyincorporated into the soil surface then thesystem is probably healthy. But if littertrains or paths created by either wind orwater are obvious, then it is a sure sign thatthe litter is on the move and less is beingretained.

Nature of the soilSoils vary considerably in their resilienceand ability to withstand battering fromeither the forces of nature or mankind.Sandy soils have the advantage of goodwater infiltration but may be more

Between the two there is usually a ‘transferzone’ which is downstream of the sourcezone. Temporary and intermittent storage ofmaterial occurs in this zone and manyerosional events such as major storms maybe required before sediment crosses thetransfer zone. Every source has itsassociated transfer zone and sink, eventhough the sink may be a considerabledistance away.

Litter trails and litter on the move are always a badsign, indicating that fallen leaves and other materialare not being retained, but are being washed or blownaway. Fallen branches or other objects on the groundcan help to trap small leaves and other organic matterallowing them to be incorporated into the soil ratherthan lost.


24

vulnerable to wind erosion than finer clayand loam soils which have well developedsurface crusts. After plants are lost from acommunity, wind erosion increases in thegreater spaces between the survivors, andsandy hummocks are deposited around thebases of larger shrubs and trees. Annualplants may grow on these hummocks afterrain, but they are too unstable for morepermanent growth.

Some soils have a stable surface, which maybe protected by stones, natural crusting orplants, but are unstable beneath that surface.Duplex or ‘texture contrast’ soils are acommon example. When the protectivesurface is cut by an animal hoof or tyretrack, the next heavy shower of rain maybegin to wash away the soil.

In the higher parts of the landscape somesoils are protected by a mantle of grit orstones. These stones deflect the energy ofraindrops falling on open ground andprevent erosion, although the soils beneathtend to be shallow and comparativelyinfertile.

Surface crusts also develop on some soils.They prevent further erosion, but reducewater infiltration. Thin layers of algae,lichens, mosses or other small primitiveplants grow over the surface of many soils,and help protect the surface and absorbnitrogen from the air. These plants areknown as cryptogams and while obviousand colourful during and after rains, at othertimes they appear merely as dark stains anduneven blotches on the soil surface.

Plant typesMost plants in the arid shrublands arenatives, having evolved to suit theparticular environment over thousands ofyears. But a few exotic plants have alsobecome established, often through humaninfluence, particularly along roadsides andother areas where the ground has beendisturbed. Such immigrants include onionweed and thistles that have spread overmany areas.

Many introductions are consideredundesirable because they provide littlepermanent pasture for animals and tend tothrive at the expense of more useful plants.Some, such as the doublegee with sharpspiny seeds, have proved extremelyunwelcome to both animals and humans.

Exceptions are buffel grass and Birdwoodgrass (Cenchrus species) which areintroduced perennial grasses that areproving a useful forage from the GascoyneRiver north. However, they may bedisplacing some native species, leading toconflict between production andconservation. Wild hops, a distinctive red-flowering winter annual that wasintroduced by the Afghans, has been usefulas an early coloniser of mine dumps.

Annuals, including both grasses andherbaceous plants (or forbs as they areknown) are a very important part of thevegetation, particularly in good seasons.While called annuals because they growand set seed in a single year, they may not

C H A P T E R 2

25

Any plant at least 2 metres high with asingle trunk to at least 1.5 metres isdefined as a tree. The most common treesare acacias, such as mulga or snakewood inthe northern and western areas, and westernmyall of the Nullarbor.

Plants more than 2 metres high withmultiple trunks are described as tallshrubs. Many of these are also acaciasincluding bowgada, sugar brother andmulga, which has several different forms,sometimes growing as a tall shrub and atother times as a tree.

Those plants between 1 and 2 metres highare known as medium shrubs and thoseless than one metre high as low shrubs.Low and medium shrubs include most ofthe famous saltbushes and bluebushes,which are both salt and drought tolerantwhile providing palatable forage. Otheruseful species include cotton bush, flannelbush and some of the sidas and cassias.

Spinifex is probably the best known of theperennial grasses, and several differentforms cover thousands of squarekilometres. Most spinifexes in the aridshrublands have very little value either tostock or larger native animals such askangaroos. However, spinifex clumps formimportant habitats for some birds and smallanimals. Their seed heads are importantfood sources for birds and the leaves areuseful for termites and other insects.

(To distinguish a perennial from an annualgrass species, the simplest method is to

appear every year, unless the rainfall andseasonal conditions are suitable. In thisregion most germinate over autumn andwinter, providing useful forage over thecooler months and into the spring, but thendry off and lose nutritional value rapidly.

Annuals include many colourful andfamous wildflowers such as everlastingdaisies and billy buttons, which oftenthrive on disturbed soil along roadsideswhere there is less competition fromestablished perennials. Degraded soil fromwhich perennials have been lost can oftenproduce magnificent stands of flowers.

Some plants produce roots, stems andleaves in the first year and flowers andseed in the second before dying. Suchshort-lived perennials are known asfacultative perennials or biennials.

But the most important plants in anysystem are the perennials, ranging fromlarge trees down through various sizedshrubs to the grasses. Whatever the size,they have a very important role instabilising the landscape – protecting thesoil from the action of both water and windin all weathers and seasons.

Because the environment is harsh, treesare rarely very tall, even when growingalong rivers. Among the tallest in therangelands is the beefwood which mayreach 15 metres and is reputed to live fornine hundred years or more. Freshly-cutheartwood supposedly resembles raw beef,hence its common name.


26

exoticsnatives

perennials

weedsuseful plants

increasers

annualsbiennials

decreasers

non-indicators

PLANT COMMUNITY

check the roots: if it pulls out of the groundeasily, it is normally an annual, asperennials need a much stronger rootsystem in order to survive.)

The presence of palatable grasses andshrubs is used frequently as an indicator ofthe health of the vegetation and landscape.If their number and/or size decline withovergrazing or declining soil health theyare described as decreasers.

Those plants best able to improve theirpositions after heavy grazing, erosion orother landscape disturbance are usuallyknown as increasers. Frequently these areless palatable plants which tend to beignored by grazing animals and thus areable to set more seed. They are oftenwoodier and pricklier than the decreasersand eaten only when few alternativesremain in a local area.

Some very palatable shrubs are decreasersin all areas, but others can vary dependingon what else is on offer to grazing animals.Plants such as flannel bush and three-winged bluebush could be decreasers incountry supporting few alternative browsespecies, but increasers in more fertilesituations where they are ignored.

Overgrazing often results in greater densityof woody unpalatable increasers. Apartfrom providing little forage value foranimals, some of these plants are long-lived and can produce thickets which limitstock access to other more palatable plants.The less palatable plants are frequentlyfrom the poverty bush (Eremophilaspecies) and cassia groups, although a fewindividual species have some feed value tostock.

Palatability of some other plants varieswith the soil. Wilcox bush is a very

Functional components of the plant community.

C H A P T E R 2

27

palatable low shrub in many locations,though its palatability is often lower onsandy soils. A fairly close relative, turpentinebush, so called for its distinctive tang, is atypical increaser shrub. Turpentine bush is abright green colour, contrasting with thegreyish tones of most shrubs, but isunpalatable to stock. Plants may live forsixty or seventy years and the numbersincrease following the grazing of morepalatable species.

The cassias (also known as sennas), aredistinguished by their yellow five-petalledflowers. They include a few palatable typessuch as green cassia and creeping cassia, butmany others are classic increasers.

In contrast, the non-indicator plantsinclude a large group which may or may notbe palatable, present in very small numbers,or often out of reach of stock so do not tendto increase to any great extent when othersare removed. Numbers remain relativelystable within a plant community and offerlittle information on the possible changes incondition, except when overgrazing orerosion reaches drastic levels and thenumber of all plants declines sharply. Manytrees, even those with palatable leaves suchas mingah bush, are regarded as non-indicators. Others are those plants whosedistribution is normally so thin on theground that their presence or absenceprovides no clue to condition. Distinctivetrees such as the light-green leavedkurrajong are in this category.


Condition of the rangeIn this guide, rangeland has been dividedinto three levels of long-term condition –good, fair and poor – depending on thepresence and abundance of palatableperennial plant species combined with theongoing landscape processes.

Good condition: When perennial plantspecies present include all or most of thespecies expected. Some species may haveincreased, but the total species compositionand number are close to optimal. Soil,water and nutrients are strongly conservedand used within the system. Erosion is non-existent or minor.

Fair condition: Moderate losses of certainperennials and/or increases in other shrubsand grasses have occurred but most originalspecies are still present. Some soil, waterand nutrients may have been lost, but mostare retained and erosion (if present) isminor. With good seasons and carefulmanagement sites can be returned to goodcondition.

Poor condition: Vegetation is characterisedby marked decreases in the number ofplants and occasional losses of plantspecies. This may result in either areas ofbare ground or areas dominated byincreaser species such as woody shrubs.Because of the loss of individuals and evenwhole species in rare cases, the soil is moreopen to water and wind erosion. It tends tolose soil, water and organic matter and isunable to capture replacement materials.

28

number

of species

increasing radius

saltbush plains

hardpan plains

20 metres

Numbers of species found in a given area can be much greater in some country types than others. In the mulgahardpan areas for example a larger area may reveal more species while in the saltbush plains a few speciesdominate large areas. A radius of about 20 metres usually provides a reliable guide to the species found in alocal area.

Erosion ranges from none to severe andmay be continuing.

In some country types distinct thresholdshave been found. Let the number of plantsfall beneath a certain level and there will bea high chance of erosion and a resultantshift from one condition level to another;keep it above this critical point and thesystem should remain more or less inbalance. Flood plains near river frontagesprovide typical examples of this. Wherepossible we have tried to indicate thesethreshold points for common types ofvegetation, although they vary considerablyin different country types.

In other country the shifts in condition aregradual over a continuum. Lose a fewplants and condition of both vegetation and

soil slips only slightly and may be fairlyeasily reversed by reduced grazingpressure and good seasons.

For each country type we have listedfeatures that should be present for eachlevel of condition, although not all may befound at a single site. For simplicity andease of reference, most of our measures ofplant numbers relate to an area about 10metres by 10 metres or 100 square metreswhich we have dubbed a centihec. This isone hundredth of a hectare which makesvalues easily comparable with those usedin technical publications such as rangelandsurvey reports. A centihec is a bit less thanhalf a tennis court. It is three-quarters ofthe area of a monitoring site (135 squaremetres) used by pastoralists, allowing

C H A P T E R 2

29

direct comparisons with plant numbersfound in these situations.

Numbers of species have been indicated forlocal areas within a radius of roughly 20metres. In some country, for examplesaltbush and bluebush on level plains orriver frontages, the vegetation is dominatedby just one or two species and a singlecentihec might give a good indication of thenumber of species present. But in othercountry such as mulga hardpan where theindividual plant numbers are much lower, asingle centihec might contain only four orfive different species while a larger areawould reveal the much greater diversity ofspecies present.

This small Wilcox bush growing in stony hardpan country near Meekatharra has been grazed heavily, but has thecapacity to regenerate given the right seasonal conditions and freedom from overgrazing. The number of Wilcoxbushes present is regarded as a key indicator to the health of the rangeland in many areas.

While the same basic country type can befound in geographically isolated areas,comparing a single factor such as thenumber of plants can be misleading on itsown. For example, the total plants presenton good condition mulga hardpan plains inthe Murchison will be around 20 plants percentihec but could rise to 35 per centihec inthe north-eastern Goldfields, even thoughthe species are similar. And the same broadtype of country may support silver saltbushin one area but bladder saltbush a fewkilometres away. Bladder saltbush maygrow as densely as 250 plants per centihec,but the densest ungrazed stand of silversaltbush may contain only 80 larger and


30

more spreading plants in the same area.

Total amount of plant growth can also bemisleading on its own as mass is stronglylinked to seasonal conditions and can beboosted enormously by the presence ofannuals that may die off and blow away afew months later. Such annual growth canbe a very useful addition to the diets ofgrazing stock in a good year, but may notexist in a drier season.

The size of plants may also not tell the fullstory. It is their presence or absence thatis more significant. If an observer views anarea that is being grazed by stock aftermonths of dry weather the size of manypalatable plants may be fairly small and thetotal amount of plant material very low. Butif good rains fell the next day, seeds wouldgerminate and the existing perennials wouldrespond rapidly with fresh green growth.Within a few weeks, country that appearedto be in only fair or even poor condition to acasual observer could suddenly appear verygood again.

Three main elements can affect long-termrange condition: seasons, grazing pressureand fire. These can act independently or incombination and result in very long-term oreven permanent changes. Where possiblewe have indicated these effects (as weunderstand them at present) for different

country types using flow charts. There isno starting point. A particular area ofcountry may be in pristine condition,totally degraded or somewhere in between.The charts indicate how it might havereached its current condition and how thislevel might be changed.

After a student of the rangeland gets a feelfor the plant communities and the likelynumbers of certain indicator plants thatshould be present, both decreasers andincreasers, he or she should be able toassess the country (read the rangeland)fairly easily regardless of seasonaldifferences.

Many of the plants described in this guideappear very similar to the untrained eye.This is probably not surprising as they haveevolved under the same environmentalconditions over thousands of years and areoften closely related. In order to gainmaximum advantage, we recommend thatReading the rangeland should be read inconjunction with Arid Shrubland Plants ofWestern Australia (first and secondeditions) which contains full colourillustrations and detailed descriptions ofmost of the plants listed.

C H A P T E R 2

31

ARID SHRUBLAND

sandplain

mulga shrubland

saltbush/bluebush

granitic shrublandstony hardpan plainshardpan plains

spinifexwanderriebowgadacurrant bush mixed shrub

stony bluebushgreenstone slopesGoldfields gum belt

breakaway slopesundulating plainsflood plains and river frontageslevel plains and lake frontagesNullarbor Plain

ver the years, scientists and otherobservers have sub-dividedrangeland into many different

categories for varying purposes. Geologistshave tended to look mainly at theunderlying rocks and have been lessinterested in what happens above theground; botanists have concentrated on theexact nature of the vegetation; soilscientists have had a close affinity with theprocesses that affect the soil, and so on.

In this guide, we have sampled the wisdomof all of these experts seeking commonfactors rather than differences, and haveconcentrated on the most extensive types ofcountry. That the tops of hills for example,or narrow fringes a few metres from themain rivers do not fit precisely into any ofour groupings will soon become apparent.But such areas are a tiny fraction of thetotal land and our concern is for the wider

Chapter 3 – Main types of countrylandscape that must be conserved forpastoralism, tourism and for itself.

Three main groups of country are apparentin the arid shrubland:

• Mulga shrubland• Saltbush and bluebush• Sandplain.

In some areas these broad country groupsmay extend for tens of kilometres while inothers they combine to form a smallermosaic across the landscape. Within eachmain group there are several country typeswhich have different features and differentproblems for management.

Some of the distinquishing features of thesoil and vegetation are listed on page 32and it should be fairly simple to identifythe main groups. Following the key to thenext level should help to identify theimportant country types.

32

MULGA SHRUBLAND

SALTBUSH/BLUEBUSH

SANDPLAIN

soil: non-saline, shallow

soil: non-saline, deep and sandy

main vegetation: open mulga and low shrubs

soil: saline, often eroded

main vegetation: dense tall shrubs and perennial grasses

main vegetation: low bluebush and/or saltbush shrubs

C H A P T E R 3

This area of mulga near Meekatharra is typical of large areas of the rangeland. The mulgas are the largest trees inthe landscape which also supports a variety of low shrubs. Standing dead timber is a common feature in theseinland areas. Note the distinctive bright green turpentine bush (an increaser species) in the middle groundgrowing with the grey Wilcox bushes which are useful forage in this country.

Key to country groups.

33

M A I N T Y P E S O F C O U N T R Y

Mulga ShrublandThis country is the most common and occupies about 60 per cent of the total shrubland.The shallow soils are relatively infertile and support only scattered vegetation, includingthe well-known mulga, which is a member of the acacia or wattle family. There are threedistinctive types of mulga shrubland:

Granitic Shrubland – see page 42

landscape position occurring upslope of hardpan plainstopography hilly or undulating with outcropping granite

soil surface gritty, coarse sand, cryptogam crusts in parts

water infiltration rate rapid

Stony Hardpan Plains – see page 47

landscape position above hardpan plainstopography gently undulating with distinct drainage lines

soil surface stony or gravelly

water infiltration rate slow

Hardpan Plains – see page 52

landscape position above river flood plains, level plains, lake frontages

topography level plains, no obvious drainage lines

soil surface crytogam crusts common

water infiltration rate slow

34

Saltbush and BluebushThis is some of the most fertile and productive country for grazing animals, althoughoccupying only about 20 per cent of the total rangeland area. The soils are generally ‘saline’ orsalty – a factor which determines which plants grow on them, the best suited including thelegendary saltbushes and bluebushes.

In most situations the saltbush and bluebush communities occur on alluvial plains, but are alsofound on the slopes below breakaways and the undulating plains below these.

Salt crystals lying on the surface of the ground and even on the plants themselves, are anobvious indication of very saline conditions. People familiar with local areas soon learn torecognise the distinctive plants which tolerate salty conditions. Very salty soil is also ‘puffy’under a crusted surface.

Low shrubs are the distinctive and dominating form of vegetation, either a single variety ofsaltbush or bluebush or a mixture of several different types. The soils may be susceptible towind and water erosion if degraded. We have separated the saltbush and bluebush country intothe five most important and commonly occurring groups:

Different forms of low saltbush and bluebush vegetation cover about a fifth of the arid shrubland on saline soils.This area is near the Ashburton River, but similar country carrying slightly different species is very common,particularly on the flood plains of the main rivers and near salt lakes.

C H A P T E R 3

35

Breakaway Slopes – see page 60

landscape position high, below breakawayssoil surface sandysoil colour greyish-whitesoil depth shallow

Undulating Plains – see page 66

landscape position mostly lower slopessoil surface stonysoil colour brown or red-brownsoil depth shallow

Flood Plains and River Frontages – see page 82

landscape position river plainssoil surface sandysoil colour red-brown to red-greysoil depth variable

Level Plains and Lake Frontages – see page 90

landscape position level plainssoil surface crusted, cryptogams commonsoil colour redsoil depth deep

Nullarbor Plain (geographically distinct area) – see page 96

landscape position gently undulating plainssoil surface cryptogams commonsoil colour buff (but very dark when cryptogams present)soil depth mostly shallow over limestone


36

SandplainSandplain may be found in small areas interspersed with other country such as mulgashrubland, or cover large areas on its own. There are four basic sandplain types, including theregionally separate currant bush mixed shrub, which occurs on less sandy soils nearCarnarvon.

Sandplain areas are often intermingled with other country types. Deep, sandy non-saline soil is usual, supportinga mixture of dense tall shrubs and perennial grasses. This pastoral country in the lower Murchison is dominatedby tall bowgada shrubs and wanderrie grasses.

C H A P T E R 3

37

Spinifex – see page 104

landscape position plains, or banks on hardpan plains

main vegetation many perennial hummock grasses, some shrubs

soil surface sandy


Wanderrie – see page 106

landscape position plains, or banks on hardpan plains

main vegetation many perennial tussock grasses,some shrubs

soil surface sandy


Bowgada – see page 112

landscape position gently undulating plains

main vegetation low trees/tall shrubs, fewer perennialgrasses than wanderrie

soil surface sandy


Currant Bush Mixed Shrub – see page 117

landscape position plains

main vegetation medium to tall shrubs, includingcurrant bush

soil surface thin crust

water infiltration rate moderate


38

Meekatharra

Kalgoorlie

PERTH

Carnarvon

favoured locations. Some forms have adefinite tree shape (single trunk) whileothers are multi-stemmed shrubs. Leafshapes range from broad to narrow to veryfine. It is less common on very sandy andvery clayey soils.

The mulga is very well adapted to lowrainfall environments and low fertility. Itsbranches and leaves slope upwardsallowing rain water to be channelled downthe stem, increasing the soil moisture closeto the trunk. Deep roots help overcomelengthy dry periods by tappingunderground soil moisture, while extensiveroots just below the soil surface enable it tobenefit from light rainfall whilesimultaneously stabilising the soil.

In inland areas around Meekatharra andWiluna, dead mulga and other species are afrequent feature of the landscape. Theirpresence does not mean a recent pestilence(although hail has been known to killmulga), but can reflect a gradual loss ofindividuals over many years. Instead offalling to the ground and rotting awayquickly under the influence of moistureand animal activity as happens closer to thecoast, the dead timber may remain standingfor fifty years or more in the dryenvironment. Mulga fence posts have beenknown to survive for eighty years in suchareas.

ulga shrubland occupies about500,000 square kilometres of thearid shrublands, stretching over

vast areas of the Murchison, Gascoyne andGoldfields above the river flood plains.

Chapter 4 – Mulga Shrubland

The mulga itself is probably not one of theworld’s most beautiful trees in many eyes butis regarded fondly by those who appreciateits important role in these dry environments.

It grows in several different forms from thesouthern Pilbara to the Nullarbor, and isfrequently the biggest tree or tall shrub in thelandscape, reaching 8 metres in some

39

Soils in the mulga shrubland are generallynon-saline, shallow and of uniformconsistency, that is if they are sandy in thefirst few centimetres, they remain sandythroughout. They tend to be stable to erosionfrom water or wind, but may be susceptibleto track erosion on tracks and in ‘washes’that carry concentrated flow. Basic fertilityis low.

Good quality underground water isfrequently available through bores or wellsless than 10 metres deep and this has madethe country easy to develop for pastoralism.Mulga country was often the first land to bedeveloped, because of the availability ofwater. Most mulga shrublands have been

Mulga groving patterns are clearly visible in aerial or satellite photographs (as above). The groves about 50 to100 metres long, tend to stretch along the contours of the land, even though the country may appear almost flat.

grazed by sheep and cattle, sometimesheavily, for a century or more. Many treeshave been removed for fence posts over thistime so numbers may now be less thanbefore white settlement.

Groving is a common feature on thehardpan plains, occurring across thedirection of the slope. Groves are densepatches of mulga and other shrubs whichmay range from only 10 metres long tomore than a kilometre. At the lowerextreme, a mulga grove may consist of onlythree or four trees, but can still provideprotection and a favourable location forsmaller shrubs and other plants. Clumpingof understorey shrubs within fertile patches

M U L G A S H R U B L A N D

40

mulga hardpan plains

river flood plains

granitic shrubland

stony hardpan

C H A P T E R 4

around the base of trees is common.

In these types of vegetation, grazing impactis not marked by dramatic change in speciesrelated to distance from water, but tends to bereflected in changes across whole paddocks.Some of the most widespread decreaserspecies include cotton bush, horse mullamulla, mulga bluebush and warty-leaferemophila, with the most sensitive beinghorse mulla mulla in the areas where itoccurs. Turpentine bush is the mostwidespread increaser following heavygrazing.

Palatable shrubs comprise both long-livedspecies such as Wilcox bush, compactpoverty bush and warty-leaf eremophila plusshort-lived species such as cotton bush andmulga bluebush. Germination of the short-lived species can be prolific in favourableyears but the long-lived species show steadyand less dramatic recruitment. Soils remain

largely intact following overgrazing, soalthough the soil becomes less suitable forrecruitment and water trapping is lesseffective, rehabilitation can be achieved inthe medium term – fifteen to twenty fiveyears.

Regeneration of shrubs is encouraged bybuilding up plant litter and slowing themovement of water and nutrients throughthe system. Opportunities for re-establishment probably involve a sequenceof reasonable to good seasons coupled withlow stocking rates to increase both seed andsurface litter.

While a casual observer might see a widevariety of vegetation types within themulga shrubland, it can be divided intothree broad types moving down the slopefrom the tops of any low hills or ridges:Granitic Shrubland, Stony HardpanPlains and Hardpan Plains.

Typical arrangement of country types in the mulga.

41

Fair(Few decreasers)

continued heavy grazing

Good(Numerous decreasers,stable soil)

light grazing, good seasons

Stable, unproductive except annuals

Some soil erosion, unproductive except for annuals. Further

degradation, shrub and tree deaths

Stable soils, unproductive

except annuals

Poor(No decreasers,

no seed for recovery, some soil erosion)

lots of overland flow little overland flow

Stony hardpan Mulga hardpan Granitic mulga

heavy grazing


In good condition, mulga shrubland carries a moderate number of decreaser low shrubs beneath the mulgas andother acacias. Soils are stable under conservative grazing pressure when decreaser shrub numbers are maintainedand there is no soil erosion. If some decreasers are lost (fair) they can be regained after good seasons and lightgrazing. However, long-term heavy grazing will result in the country reaching poor condition where no palatableshrubs remain and there is no seed. It is then almost impossible for recovery even if the range is spelled for manyyears. Reseeding might help recovery but success is uncertain and costs are very high.

42

Granitic ShrublandThis country type is often found adjacent toand outcropping slightly above the hardpanplains. The soils are generally shallow sandyloams which have been formed by the veryslow weathering of granite. Individual areasmay be fairly small – perhaps only a fewhundred metres across – or much larger.Low granite outcrops are frequent. A typicalexample is the grit-surfaced plains of theChallenge land system in the Murchison.

Soil surfaces are covered with coarse sandygrit plus some larger stones and pebbles ofquartz and granite. The soils tend to be apaler red than the hardpan plains below.Severely eroded sites are rare, and unlike thehardpan plains, roads and tracks rarely causeerosion here.

This country type grades into stony hardpanin some northern areas. Both landscapes aresimilar plains, but the soil surfaces aresandier in the granitic shrubland. Theunderlying granite rocks are rich in quartzbut relatively poor in other minerals,especially those required for plant growth.Even in good condition, vegetation will notsupport high stocking rates although thecountry is attractive to grazing animals.Granitic areas appear to be less droughtresistant than the mulga hardpan plains.Water infiltration is rapid but the soils areshallow and grades are steeper allowing run-off after fairly light showers of rain. Growthof annual species is often rapid after rain.

Differences in species with location areconsiderable, so that some species found ina typical granitic shrubland in theGoldfields for example, may vary fromthose found in the Murchison. Generallythough, the dominant plants will always beacacias, eremophilas, cassias or Ptilotusspecies (cotton bush and mulla mullas).

Groving effects are not common. Trees andtall shrubs are mostly sparse – usually onlyone or two per centihec (an area 10 metresby 10 metres or 100 square metres) – butinclude the granite wattle (also known aswitchetty bush), mulga, curara andminiritchie. Miniritchie is distinctive for itsred bark which separates into small curlsalong the trunk.

Tall saltbush (often called rhagodia orclimbing saltbush) can also be a feature.

The characteristic grasses are short annualssuch as wind grass and Murchison redgrass. Perennial grasses are few althoughlemon-scented grass is widely distributedthrough the Murchison, Gascoyne andnorthern Goldfields. This grass is rarely ifever eaten by stock, though pastoralistshave reported it grazed by euros.Occasional broad-leaved wanderrie andcreeping wanderrie may also be present.

Kite-leaf poison occurs around the granitedomes in some areas and has caused heavylosses of sheep, cattle, goats and horses. Itcontains a toxin similar to the widely used

C H A P T E R 4

43

rabbit poison 1080 (monosodium fluoroacetate), to which the native marsupials areimmune, having evolved in the same placeand time. The leaves are usually eatenwhen fresh green shoots are present but noother attractive forage is available.

Decreasers include felty fuchsia bush, flat-leaved bluebush, horse mulla mulla, laxbluebush, warty-leaf eremophila, silkybluebush, cotton bush and Wilcox bush.Tall sida and tall saltbush are very resilientto overgrazing and may be the lastremaining decreasers.

Some students of the rangeland put highvalue on the presence of individual speciessuch as cotton bush, but concentrating onone species only can be misleading. Itappears that certain sites may be unusuallyproductive for cotton bush, and that soilfertility varies over short distancesirrespective of range condition.

On degraded sites increasers occasionallyinclude turpentine bush, crinkled cassia,straight-leaved cassia and banana-leafcassia.

A good indicator of range condition is thenumber of species present and the numbersof the palatable plants or decreasers.

Good news signs• Many different species present

• Mixed aged plants

• Lots of cotton bush, Wilcox bush,flat-leaved bluebush, felty fuchsia bush,warty-leaf eremophila

• Plentiful cryptogamic crust

Bad news signs• Few species present and areas of bareground

• Absence of cotton bush, Wilcox bush,tall saltbush, curara, mulga

• Young crinkled cassia, banana-leafcassia

• Well chewed bushes

• Broken soil surfaces and absence ofcrusting

Indicator Good Fair PoorNumber of decreaser species in local area 4-9 4-6 <4

Average number of decreasers per centihec >10 5-10 <3


44

This site near Cue carrying sparse mulga with a good understorey of low shrubs including many decreaser speciesis in good condition. There are numerous cotton bush (12 per centihec) and compact poverty bush plants (10 percentihec) visible in the foreground plus a few horse mulla mulla, tall saltbushes and silky bluebushes.

Good condition• Dominant plants are acacias, poverty bushes, cotton bush and cassias. There could be ascattering of dead or moribund plants, but the stand is not dominated by dead individuals.

• Different aged plants (different sizes) may be evident within most species.

• The number of decreasers is at least 10 plants per centihec.

• Not all decreaser species grow at any one site but 4 to 9 palatable species are present.These include cotton bush, Wilcox bush, felty fuchsia bush, tall saltbush, horse mulla mulla,warty-leaf eremophila, sidas and small bluebushes.

• A few increaser species such as unpalatable cassias may be present but are not dominant inany of the vegetation layers.

• There is no accelerated soil erosion. Soil surface crusts of lichen and algae are welldeveloped.

C H A P T E R 4

45

This area of granitic shrubland north-east of Leonora is in fair condition. The low shrub layer is dominated bycotton bush (about 10 per centihec) with a few other small decreaser shrubs which are not readily visible in thephotograph. There is no soil erosion.

Fair condition• The number of decreaser low shrubs falls to between 5 and 10 plants per centihec andthe number of species is about 4 to 6 at any one site.

• Key decreaser species may become confined to protected areas under taller shrubswhere grazing is restricted.

• Some increaser species are present but not usually dominant.

• There is no accelerated soil erosion and soil surface crusts are still obvious and largelyintact.


46

Both the absence of decreaser (usually palatable) low shrubs and minor soil erosion indicate that this site westof Cue, photographed in January 1994, is in poor condition. It supports a few granite wattles and mulga plussome dry annual grasses and herbs.

Poor condition• The number of different decreasers at a local site is now less than 4 species and the totalnumber of decreaser plants is less than 3 per centihec.

• Increaser species such as turpentine bush, grey turpentine bush, spoon-leaved eremophilaand crinkled cassia are more frequent and dominate the low and/or medium shrub layers.

• There may be slight or minor soil erosion in the form of small scalds up to 5 metres indiameter with redistribution of soil surface material and litter. Soil surface crusts are stillpresent but patchy.

C H A P T E R 4

47


Stony Hardpan PlainsThese gently sloping or undulating plainsare one of the least productive countrytypes covered in this guide. They are clearlyrecognised by their stony surfaces,including a ‘quartzy strew’ aroundMeekatharra and quartzy strew or fineironstone grit mantles in the north-easternGoldfields. They normally occur slightlyhigher in the landscape than the moreextensive mulga hardpan plains and shedwater onto the lower plains via narrowdrainage lines or as broad sheet flow.

Soils beneath the stony mantle are infertileand very shallow, frequently less than 30centimetres deep. Water infiltration isgenerally slow, much of it running off downthe slope. As a result, vegetation isnormally scattered and stunted although itmay occur as fairly dense small grovesbetween much larger open spaces.

This type of rangeland often merges withseveral other types including graniticshrubland and mulga hardpan plains.

Vegetation resembles that of the hardpanplains but is much sparser. Medium shrubsare less prominent than the low shrubs, tallshrubs or trees which are found mainly onthe creeklines. Mulga is very common andgidgee grows in some areas.

Regeneration of mulga from seedlings hasbeen poorer here than in most othervegetation types. Groving effects areinfrequent and groves are usually less than

30 metres wide and 100 metres long. Soilswithin groves are usually deeper and lessstony.

Trees are fewer and species of acacias andpoverty bushes differ slightly from thosefound on the hardpan plains. Notableexamples present may include spoon-leaved eremophila, grey turpentine bush,rock fuchsia bush and Murchison willow.Small perennial shrubs such as cotton bush,horse mulla mulla and royal mulla mullaare often conspicuous, as is cannon ballswhich is a biennial.

The soil supports abundant annuals aftereffective rains including wind grass andhas a reputation for growing good woolalbeit at low stocking rates. Perennialgrasses are rare.

Watching the health and numbers of keydecreaser species provides a good guide tochanges in condition. Excess grazing mayresult in a loss of palatable acacias butencourage more unpalatable eremophilas(poverty bushes) and cassias which helpmaintain the total plant numbers whilereducing useful feed. This effect is seenoften near homesteads and shearing shedswhere stock are held in small paddocks.

Palatable perennials often grow in clumpsof tall shrubs and around decaying mulgalog mounds which provide some protectionand a more fertile niche.

48

C H A P T E R 4

Typical decreasers include mulgabluebush, cotton bush, warty-leaferemophila, tall saltbush, horse mullamulla, royal mulla mulla, George’sbluebush, flat-leaved bluebush and pussybluebush. Sidas and ruby saltbush aredecreasers in the Carnarvon area but lessimportant elsewhere.

Common increasers include turpentinebush, grey turpentine bush and spoon-leaved eremophila. Variable cassia andcrinkled cassia grow in the north-easternGoldfields; wait-a-while is common in theCarnarvon Basin and the Gascoyne.

Good examples of this type of country canbe found on the Windarra land system ofthe north-eastern Goldfields or theKoonmarra land system in the Meekatharraand Murchison districts where theindividual stony plains are up to 2kilometres wide and 3 kilometres long.

Good news signs• Horse mulla mulla, mulga bluebush,cotton bush, George’s bluebush,Wilcox bush, warty-leaf eremophila,young mulgas present

• Mixed age plants present

Bad news signs• Poverty bushes and nothing else

• Acacias and nothing else exceptpoverty bushes

Indicator Good Fair PoorNumber of different decreaser species present >7 4-6 <3

Number of decreaser plants per centihec >5 1-3 <1

Total low shrub numbers per centihec 15-30 10 <7

49


This stony hardpan plain near Leonora, photographed in the spring of 1993, is in good condition. Sparse mulga isgrowing on the slopes, with a dense stand of mulga on the creekline in the background. Low shrubs are abundant,with cotton bush (in bloom), mulga bluebush and Wilcox bush obvious in the photograph. This country type is oneof the least productive in the rangeland and vegetation is never very dense.

Good condition• Total low shrub numbers are usually between 15 and 30 plants per centihec.

• At least 5 decreaser low shrubs per centihec and 7 different decreaser species at a local siteincluding horse mulla mulla, cotton bush, warty-leaf eremophila, bluebushes and Wilcoxbush.

• Less palatable shrubs are always present including straight-leaved cassia, crinkled cassia,various eremophilas and flannel bush.

• There is no erosion.

50

C H A P T E R 4

This site in the north-eastern Goldfields is in fair to good condition. Decreaser shrubs are mainly cotton bushand tall sida. The ground is protected by a thin layer of stones and there is no soil erosion.

Fair condition• The number of decreasers falls to as low as 1 plant per centihec with few youngdecreaser species. Some of the more sensitive indicators such as horse mulla mulla, warty-leaf eremophila, flat-leaved bluebush and ruby saltbush may exist only as occasionaloverbrowsed individuals.

• Unpalatable species may increase in number marginally, but in general remain roughlyconstant while the more palatable plants decline.

• Decreaser species decline to about 4 to 6 in a local area.

• Total low shrub numbers are around 10 per centihec.

• There is no erosion.

51


This country north of Leonora is in poor condition. Mulgas are the most prominent trees or tall shrubs while thelower storey is dominated by turpentine bush (10 per centihec) which is an increaser species, unpalatable tograzing animals. There are virtually no decreaser shrubs present and none that are readily apparent in thephotograph.

Poor condition• Few (less than 3) decreaser species are present and the effect of overgrazing becomesobvious. No decreaser plants may be present per centihec. Understoreys are sparse,sometimes containing only unpalatable species such as turpentine bush.

• Total low shrub numbers fall to less than 7 per centihec.

• Even normally unpalatable shrubs may be grazed and decline in number.

• Erosion remains very uncommon because of protection from the stony mantles.

52

C H A P T E R 4

Hardpan PlainsHardpan plains, sometimes called washplains, occupy extensive areas of theGascoyne, Murchison and north-easternGoldfields between the low hills and theriver flood plains or salt lakes. They are themost widespread country type in therangelands of Western Australia and insome areas extend over 60 kilometreswithout change. The landscape oftenappears almost flat, but there is usually avery gentle slope (one in three hundred)allowing water to flow slowly across thecontour after rain. Some micro-terracing(1 to 2 millimetres deep) can be seen.

The red-brown soil is normally fairlyshallow – perhaps only 15 to 80centimetres thick – and overlays a red-brown ‘hardpan’ known locally as coffeerock or Murchison cement. This issometimes visible when exposed byerosion and can provide a frustratingbarrier to both human activity and plantroots. Once a mulga or other well adaptedplant penetrates this barrier, it is able togain advantage from good qualitygroundwater at comparatively shallowdepth (commonly 6 to 16 metres in theMeekatharra-Wiluna area) but growth ofsmaller species can be severely limited.The shrubs that grow do fairly well, butthere are comparatively few of them.

The soil has been formed by slowweathering and deposition and is normallystable and non-saline. Its surface may be

covered with a few stones and pebbles insome areas, but more commonly is stone-free. Tiny lichens, algae and fungi(collectively called cryptogams) arewidespread and help protect the soil surfacewhile fixing nitrogen from the atmosphere.Tiny annual plants are also common whichdry off to hard remnants at the end ofwinter. These also help to protect the soilsurface from erosion.

Vegetation on these soils is fairly scatteredand is sometimes concentrated into densergroves which are roughly aligned on thecontour. These groves intercept run-offwater and material carried with it fromhigher up the slope. Soils are deeper in thegroves and such areas are favoured by manyforms of animal life. Vegetation within thegroves is at least twice as dense as betweenthe groves.

Other areas, known as water course country,are dominated by ‘washes’ which carrymore concentrated water flow. Soil surfacesare frequently sealed, making plantgermination difficult. Some washes supportdense mulga and hop mulga with almost nounderstorey shrubs.

Groving is more developed in areas thatreceive concentrated sheet flow, whereindividual groves may be 500 metres longand up to 100 metres wide. In some flatterareas groving is indistinct on the ground butvisible from the air.

53


Hardpan plains often adjoin stony hardpanplains or granitic shrubland on the higherside of the gentle slope, and sandierwanderrie country on the low side.

Tall shrubs or low trees, most commonlymulga and sometimes hop mulga, are thedominant upper storey and curara, gidgee,bowgada and other acacias may also bepresent. Of the perennial grasses, woollybutt is found occasionally. In good seasonsmany annual grasses appear, but thisreflects seasonal condition only.

The best indicator of range condition is thenumber of all perennial shrubs anddecreaser low shrubs. However individualshrub numbers tend to be much higher inthe Goldfields than the Murchison for thistype of country.

Some of the most widely occurringdecreaser species include mulga bluebush,cotton bush, Wilcox bush, tall sida, warty-leaf eremophila, tall saltbush and flat-leaved bluebush. Other decreasers includefelty fuchsia bush, ruby saltbush, greencassia, red grevillea and mulga broombush.

Good examples of this country can befound in the Yanganoo land system near theMurchison and Roderick Rivers andRainbow and Jundee land systems in thenorth-eastern Goldfields.

Good news signs• Plentiful low shrubs

• Mulga bluebush, cotton bush, Wilcoxbush and tall sida of different ages• Intact groves, lots of cryptogamic crusts

Bad news signs• Very heavily grazed old Wilcox bush,tall saltbush• Palatable shrubs such as mulga bluebushhard to find• Reduced numbers of all plants, death ofmulgas and other tall shrubs and trees ingroves• Breakdown of groves, guttering throughgroves

• Obvious terraces in drainage lines

• Some signs of surface sealing

Indicator Good Fair Poor

Number of plant species present >10 >7 <5

Number of plants per centihec 20-35 12-18 <10

Number of decreaser shrub species present 5-10 6-8 <4

Number of decreasers per centihec 10-25 2-5 <2

54

Good condition• Total shrub number is at least 20 plants per centihec, possibly up to 35 in some ungrazedareas of the north-eastern Goldfields.

• Up to 10 different species grow in a local area.

• Variable understorey consists of between 5 and 10 different decreaser species includingcotton bush, Wilcox bush, mulga bluebush, flat-leaved bluebush and tall sida.

• Number of decreaser plants is more than 10 per centihec, possibly up to 25 in some areasof the north-eastern Goldfields.

• Mulga groves may be apparent, where the density and diversity of vegetation is muchgreater than between groves, except in the mulga washes where there are very few lowshrubs.

• Good cryptogamic crusts are present and there is no erosion.

C H A P T E R 4

This mulga hardpan site in the mid-Murchison area is in good condition. There is a good range of decreaserspecies present including mulga bluebush, cotton bush, horse mulla mulla, Wilcox bush and silky bluebush.There is no erosion.

55

Tall shrubs including mulga and bowgada are the dominant vegetation on this fair condition mulga hardpan sitenear Sandstone. There is a scattering of decreaser low shrubs such as Wilcox bush, cotton bush, tall saltbush,mulga broombush and silky bluebush, but their numbers are below the potential. The soil surface is well crustedwith small algae and lichens. The pink flowering annual under the trees is pink velleia which is common to theregion.

Fair condition• Most decreaser species are present but in reduced numbers (around 4 to 6 per centihec)and often confined to areas protected from heavy grazing within shelter of larger, unpalatableshrubs.

• About 6 to 8 decreaser species occur in a local area.

• Increaser species including cassias and poverty bushes may approach dominance.

• Mulga groves are likely to be less dense and less able to trap water and nutrients.

• Occasional minor soil erosion may occur, triggered by vehicle or animal tracks, but mostareas retain fairly good cryptogamic crusts.


56

The vegetation on this shallow soil is in poor condition only, as there are no decreaser low shrubs present. The tallshrubs are predominantly mulga and curara. The soil surface is still reasonably stable and capable of supportingannuals in season as shown in this photograph which was taken in July 1993.

Poor condition• Total shrubs number less than 10 per centihec, mainly tall shrubs.

• Decreaser shrub number is less than 2 per centihec with less than 4 different decreaserspecies present at a local site.

• Turpentine bush, other unpalatable poverty bushes and cassias may increase in bothnumber and size but woody weed invasion is rare.

• Loss of larger trees and shrubs allows more rapid water flow across the surface after rain.Soil surfaces may become bare and sealed, although many retain a patchy cryptogamic crust.

• Groves are no longer effective in trapping litter, allowing water to flow through causingfurther plant death and erosion.

• Between the groves the soil remains stable unless disturbed by vehicle or stock trackswhen erosion may reveal the underlying hardpan layer. Micro-terraces can amalgamate toform more obvious terraces. Wind erosion increases with greater space between tall shrubsand trees and sandy hummocks are deposited around trunks.

C H A P T E R 4

57

PERTH

Meekatharra

Kalgoorlie

Carnarvon

Chapter 5 – Saltbush and Bluebushaltbush and bluebush are some ofthe best known groups of plantsable to thrive on salty or saline soil.

Such country covers almost 20 per cent or150,000 square kilometres of the aridrangeland in WA and is very useful forstock, especially if ample supplies of freshwater are available.

drought evading, and also include thesamphires, frankenias and bindiis.

The chenopods are a young and vigorouslyevolving set of species, with forms whichoften dominate the vegetation in widelyvarying locations. They tend to flower andfruit after heavy rain regardless of seasonand their distribution is often clearlypatterned, usually through the spacing ofbush mounds of one or more individualplants.

Seeing a lot of saltbush and bluebush is asure sign to many people that the soil issaline. In very salty areas crystals of saltare visible on the soil surface or on someplant stems. The soil surface may be puffyunder a thin crust. Finding saline sitesindicates that saltbushes and bluebushesshould be present.

Anyone carrying an electrical conductivitymeter to check salinity of bores can alsotest soil salinity using a level tablespoon(10 g) in half a baby food jar (50 mL) ofclean water. A reading greater than50 milliSiemens per metre (mS/m) or about280 ppm indicates that the soil is salty. Useof fresh water is essential because salinebore water can make almost any soil appearsaline.

Saline soils occur on the uplands just belowbreakaways, on level plains, river and lakefrontages and on the Nullarbor Plain. Manyof their features such as depth,

Saltbush and bluebush are often known aschenopods (members of the familyChenopodiaceae named from the Greek forthe goosefoot shape of some leaves). Theplants are halophytes (salt-loving) and

58

laterite cap

breakaway slope

undulating plains

floodplains

river

lake

breakaways 5-20 m high

Most saltbushes bear separate male andfemale flowers on different plants, makingseed collection a trap for novices. Therehave been accounts of some peoplecollecting mostly male flowers and thenwondering why the germination was sopoor! In some species, including the widelyoccurring bladder saltbush, female plantsare more palatable than males.

Many bluebushes are quite small, growingto a maximum of only 30 centimetres tall,while the largest, pearl bluebush and sagobush, can reach 1.5 metres. Most speciesare less than a metre. When seeds arepresent the bluebushes are readily identifiedby their seed cases surrounded by paperywings which grow along the stems.

No single species of bluebush is distributedover the entire rangeland, but in local areasthree or four different types may becommon. George’s bluebush for example isa valuable fodder shrub over large areas of

C H A P T E R 5

susceptibility to degradation and structurevary widely, but the plant species growingon them are generally similar.

In some areas the silvery-leaved saltbushes(usually Atriplex species) are dominant,while in others the bluebushes (now calledMaireana but previously Kochia species)are more common. In general, one or twospecies will dominate a saltbush site whilebluebush sites may involve a mixture offrom six to ten different species, rangingfrom short-lived biennials to long-livedperennials.

Perennial saltbush plants usually live forfifteen to twenty five years, with seedlingsestablishing in most years, while somebluebushes such as pearl bluebush establishnew plants only rarely but may survive forthree hundred years. Gascoyne bluebushplants may also live for one hundred andfifty to two hundred years.

A typical landscape which often supports saltbushes and bluebushes.

59

the inland. Sago bush is found in similarareas but is not highly favoured by stockand resists both dry seasons and heavygrazing. Flat-leaved bluebush is widelydispersed over areas north of Kalgoorlie asis three-winged bluebush. Through theGoldfields to the Nullarbor, pearl bluebushis very common while Gascoyne bluebush isrestricted to the Gascoyne and Carnarvonareas.

Bluebush communities vary in dominantspecies, often over short distances. In onearea for example, thick growth of Gascoyne

S A L T B U S H A N D B L U E B U S H

bluebush may cover the ground for manyhectares, to be replaced within a shortdistance by a different bluebush or saltbushspecies.

For convenience, we have separated thesaltbush and bluebush communities intofive types on the basis of their differentunderlying geology and landscape position,management needs and plant species:Breakaway Slopes, Undulating Plains,Flood Plains and River Frontages, LevelPlains and Lake Frontages, and thegeographically distinct Nullarbor Plain.

60

Good(Natural erosion,

many saltbushes and low bluebushes)

light grazing

heavy grazing

Poor(Reduced shrubs, increased erosion)

Irreversible loss of soil and plants

Fair(Minor accelerated erosion,

frankenias, ball-leaf bluebush, sago bush dominate)

Irrespective of grazing

Occasional spelling,good seasons

C H A P T E R 5

Breakaway SlopesBreakaways are one of the more strikingfeatures of the shrubland landscape and areformed by erosion of a much earlier landsurface. Millions of years ago during a wetclimatic period, a gravelly surface crustknown as laterite, was formed. The iron andaluminium oxides migrated to the surface toform the distinctive laterite cap. Followinguplift of the land, the original plateau waseroded along the drainage lines, and its edgeis now marked by breakaways or cliffs. Asteep short scarp or laterite face surmounts a

stony footslope followed by a more gentleslope leading down to the lower plains.Some scarps are up to 20 metres high.Granite outcrops and low stony rises maybe frequent below the breakaway faces.

Breakaways are widely distributed, withsome of the most spectacular in theSherwood land system near Mount Magnetand the terraces north-east of Leonora. Thebreakaways themselves are distinctly whitein colour caused by the presence of kaolin,a product of weathered granite.

Likely range condition changes in breakaway country.

61


More seriously degraded areas showpatchy scalding, gullying or sheet erosionand support few plants of any sort.

Vegetation often seems to be ‘sweeter onthe mountain’ and many areas have beenselectively overgrazed by stock, kangaroos,euros, feral goats and donkeys. Goats andkangaroos in particular favour these areasbecause there are plenty of caves forshelter as well as delectable plants.

A wide variety of decreaser saltbushes andbluebushes grows on ungrazed and lightlygrazed breakaway slopes including bladdersaltbush, tall saltbush, shy bluebush,George’s bluebush, bronze bluebush, feltybluebush, ball-leaf bluebush and three-winged bluebush.

Another distinctive plant group is thefrankenias. These plants contain up to 10per cent salt which is exuded onto theleaves and stems as crystals. They are onlyeaten if the stock water contains little salt,but the foliage persists more than thesaltbushes and bluebushes during dryperiods. If only frankenias are present, itindicates a degraded state.

The best indicator of land condition is thenumber of low shrubs. As condition fallsthese are sometimes replaced by taller anddeeper-rooted acacias, needlebush andcassias. Increaser shrubs include mulga,miniritchie, limestone wattle and curaraplus banana-leaf, straight-leaved, desertand variable cassias.

Breakaway slopes may be up to a kilometrelong before grading into other countrytypes, usually undulating plains. Soils areusually shallow, saline sands over clay.They are normally a greyish-white colour,although become more brown further downthe slope. Water infiltration is fairly rapid,but because soils are shallow they soonreach capacity and run-off begins. The soilprocesses remain very active. Slopes arevery susceptible to water erosion,particularly if plant cover is removed bygrazing. But even in ungrazed areas, rillingand terracing erosion patterns can be causedby the ongoing natural erosion.

Typically, erosion creeps slowly upwards,but can quickly accelerate because of thedegree of slope. The soils often carry thescars of mismanagement. Becausebreakaway slopes sometimes covercomparatively small areas in awkwardshapes, they are expensive to fence fromsurrounding country. Maintaining a highlevel of plant cover is essential to protectthe soil. Vegetation cover needed tomaintain soil stability varies with the slopeof the land, the degree of protection fromany stone mantle and the amount of waterdraining through.

Slight overgrazing leads to loss ofsaltbushes allowing more persistent speciessuch as ball-leaf bluebush and sago bush tobecome more prominent. Further grazingwill remove these and other perennials but iftopsoil is retained the land will still supportannual plants.

62

Perennial grasses are sparse but Murchisonred grass (also called love grass or redgrass) is locally abundant. In most yearsthis is only weakly perennial or biennial.

Likely range condition changesBreakaway country is less resilient thanother types that support saltbush andbluebush vegetation. The diagram showshow excessive grazing can push it ‘over theedge’ forever. Regrettably, manybreakaway slopes in the Murchison andnorth-eastern Goldfields reached thatsituation many years ago.

With light grazing, there may be a changein relative numbers of different decreaserspresent with some selective removal of themore sensitive saltbushes and lowbluebushes. This process is reversible, buteven without further heavy grazingopportunity exists for woody weeds such asneedlebush and poverty bushes to take overthe site. Continued heavy grazing leads tothe removal of a sufficient number ofpalatable plants to expose the soil surfaceto the effects of water erosion. Once thesurface begins eroding, particularly downto the clay layer, recovery is not possible.

C H A P T E R 5

Good news signs• Five or six decreaser species present,particularly saltbushes and bluebushes

• Numerous seedlings or young plants ofdiverse decreaser species

• Thick cryptogamic crusts

• Intact soil surface and sheet water flow

• Erosion products trapped and stabilisedby vegetation

Bad news signs• Poor growth of annuals on bare surfaceseven after considerable rain

• Reduced numbers of low shrubs withonly less palatable or more resilient speciesremaining

• Incised channels and bare areas

• Obvious terracing, rilling and gullying

• Broken and dispersed cryptogamic crusts

63

Good condition• One or more key decreaser species such as bladder saltbush, shy bluebush, George’sbluebush, frankenia or low mulla mulla is dominant or co-dominant.

• Perennial plant numbers are near to the maximum for the site.

• Minor erosion is common even in ungrazed sites, reflecting inherent instability.

This slope below a breakaway in the Upper Murchison is in fair to good condition. In the foreground, bluebushesand some sago bushes are evident with bladder saltbush in the middle ground. Bladder saltbush is dominantclose to the breakaway. The site could support more low shrubs than are evident in the photograph, but thesurface of the duplex soil is stable.


64

C H A P T E R 5

Fair condition• Overall numbers of low shrubs are reduced.

• Stands of key decreaser species such as George’s bluebush are patchy.

• Very resistant species such as ball-leaf bluebush and sago bush may increase in number.

• Increasers such as silver poverty bush may be more common.

• Reasonable growth of annuals in winter.

• Minor and moderate soil erosion is common in the form of shallow gullies and gutters,sheeting and micro-terracing on the contour.

This site near Leonora is rated as being in fair condition because the number of low shrubs is well below thepotential, with only the more resistant species such as frankenias, ball-leaf bluebush and samphire remaining.Shrub numbers are inadequate to protect the surface and active erosion is removing soil from the area,producing bare scalded patches.

65


This breakaway slope east of Cue is in very poor condition. Loss of shrub protection has exposed the soil surfaceto water erosion which has removed much of the topsoil by sheeting, micro-terracing and rilling. Annual herbs aregrowing only on the small patches of remaining topsoil. The saline clay sub-soil is exposed in the foreground.Access tracks on this type of country, such as the one on the left of the photograph, invariably become eroded andwashed out. The area has suffered an irreversible loss of soil and plants.

Poor condition• Density of vegetation reduces further.

• Palatable species are scarce or absent, possibly replaced by cassias, needlebush and silverpoverty bush, but more commonly by bare ground.

• Reduced growth of annuals due to lower water-holding capacity as water is lost from thesystem through erosion channels.

• Soil erosion is frequently widespread and severe with more than half of the surfacedisturbed. This environment becomes very inhospitable for establishment of shrubs.

66

Undulating PlainsBelow the breakaway slopes and adjacentto the major rivers, the country is saline andoften stony over different types ofunderlying rocks. The terrain is undulating,receiving both run-on from upper slopesand contributing some run-off to the lowerplains.

Soils are normally fairly shallow dark todusky red loams or duplexes, up to half ofwhich may be strewn with quartz gravels.These stony mantles help protect the soilsurface, but if disturbed, soils become moresusceptible to erosion. Removal ofvegetation by grazing can triggeraccelerated erosion and a plant cover of atleast 5 per cent is considered to be thecritical level below which soil erosion isvery difficult to stop.

The plant species are rich and diverse,often very similar to those growing on thebreakaway slopes. Overall grazing capacityis high and the shrubs are very durable indry conditions, providing a reliable foodsource for stock and native animals. Waterabsorption is moderate, and the vegetationresponds quickly after rain.

Thickness of vegetation is closely related toposition in the landscape as this influencesthe supply of water. Tall shrubs or trees aresparse, rarely more than two per centihec,but include several larger acacias such asmulga, prickly acacia, wait-a-while andsnakewood varying slightly with region.

C H A P T E R 5

This country is typified by the Durlacherland system of the Carnarvon Basin,Paraburdoo land system in the Ashburton,and Gundockerta in the north-easternGoldfields.

The country type occurs over a variety ofrocks which can affect its stability and theplant species. In some areas, known asstony bluebush, the underlying rocks areacidic granite and gneiss. In others theunderlying rocks are basic (alkaline)greenstone or basalt. Within the greenstonebelt, south of Menzies, an area receivingslightly heavier rainfall appears visiblydifferent where a mixture of eucalyptsdominates the upper storey species. This isknown as the Goldfields gum belt.Stony bluebushStony bluebush is the most fragile of thethree undulating plain types because of thenature of the underlying granitic rocks.Extensive areas have been heavily stockedand appear to have lost many of theirpalatable shrub species, particularly closeto water.

Decreasers include most of the bluebushes,creeping cassia, frankenias and the morepalatable saltbushes such as silver saltbushand tall saltbush (although these are prettytough). Gascoyne mulla mulla is also oftenpresent near Carnarvon. Palatable lowshrubs are commonly aggregated aroundand directly below the tall shrubs.

67

plains slopes

Fair(Low shrubs

mainly Gascoyne mulla mulla)

Clumped vegetation in hollows

Some rilling, gullying

Poor(Loss of low shrubs,

increase in woody plants)

heavy grazing

Good

(Gascoyne bluebush)

light grazing

heavy grazing


Overuse leads to loss of low shrubs butmore tall shrubs and woody weeds(needlebush, wait-a-while, cassias, povertybushes). Reduced grazing pressure canincrease low shrub numbers (particularlyperennial mulla mullas) and enhancestability. Shrub recruitment is favouredbeneath the tall shrubs and trees.

The only common perennial grass is curlywindmill grass but it is very sparse andcontributes little to total forage. Localgrasses in northern areas include soft

spinifex, Roebourne Plains grass and buffelgrass. Wind grass is abundant in very goodseasons.

The best indicator of range condition is thenumber of both decreasers and increasers.

Erosion is confined to those areas notprotected by a stony mantle. It occurs asrilling and gullying along fencelines, tracksand animal pads and as sheeting on slopes.Redistribution of soil into hollows anddrainage lines causes ‘clumpiness’ invegetation. If the topsoil has been stripped

Likely range condition changes in stony bluebush in the Gascoyne.

68

to expose the infertile, saline soil below,then recovery by grazing management is notpossible.

Likely range condition changesThe diagram shows the likely responses tograzing stony bluebush in the Gascoyne(Durlacher land system). This type ofcountry is resilient to heavy grazing, butmost commonly there will be a shift from alow shrub population dominated byGascoyne bluebush to one dominated by themore robust Gascoyne mulla mulla.Gascoyne bluebush can re-establish underlight grazing.

Continued heavy grazing results in a loss ofdecreaser low shrubs (including Gascoynemulla mullas) and their replacement bywoody weeds such as wait-a-while andstraigh-tleaved cassia. On the stony plainsthe vegetation can be quite sparse with somerilling and gullying occurring where thestony mantle does not offer sufficient

C H A P T E R 5

Good news signs• Young George’s bluebush, silversaltbush, sago bush, Gascoyne bluebush• Mixed age plants

Bad news signs• Seedlings and young plants of pricklyacacia, needlebush and wait-a-while• Heavily grazed old plants of bluebush orsago bush• Unstable bush mounds, decline in mix ofsmall sensitive palatable shrubs

protection. On the drainage plains and flowzones, low shrubs are absent and theremaining vegetation consists of clumps ofwoody weeds around drainage hollows andin crab-hole areas. Where these plains carryoverland flow, stripping and gullying canbe extensive.

This pattern is repeated in other areas witha different set of species.

69


Good condition• Most sensitive decreaser indicators are George’s bluebush, ruby saltbush.

• Less sensitive decreasers include silver saltbush, frankenias, tall saltbush and Gascoynebluebush.

• In some local areas flat-leaved bluebush, shy bluebush, felty bluebush, creeping cassiaand sago bush are useful.

• Prickly acacia, needlebush and wait-a-while are present in small numbers.

• Soil surface is intact, supporting abundant cryptogams between stones.

This stony bluebush community near Sandstone,photographed in April 1994, is in good rangecondition. Sago bush, a species that is tolerant tograzing, is interspersed with more grazing-sensitivespecies such as George’s bluebush and ball-leafbluebush. The cover of vegetation indicates a stableand healthy soil surface.

This stony bluebush plain south of GascoyneJunction is in good condition with a mixture of trees(wait-a-while), tall shrubs (mainly curara) and lowshrubs. The low shrubs are dominated by Gascoynebluebush (3 per centihec), warty-leaf eremophila (10per centihec) and cassias. The soil surface is stableunder a light stone mantle.

70

This stony bluebush site east of Leinster is in faircondition. It carries a reasonable number of lowshrubs with sago bush, cotton bush and George’sbluebush obvious in the foreground. The site couldsupport greater diversity of species, with moreindividual plants. A patch of sheet erosion is evident inthe right middle ground. Water shed from this area isconcentrated in a well vegetated hollow immediatelydown the slope (behind the eroded area).

A fine pebble strew litters the soil surface of this stonybluebush country near the Lyndon River in thenorthern Gascoyne. The site is in fair condition,supporting many different shrub species. Soil surfacecondition is also fair with some signs of disturbanceand surface sealing in the middle ground. Wait-a-whileand snakewood grow as trees and tall shrubs. Sagobush (10 per centihec), three-winged bluebush (5 percentihec), cotton bush (3 per centihec), Gascoynemulla mulla (2 per centihec) and silver saltbush (1 percentihec) dominate the shrubs.

Fair condition• Fewer species present.

• Sensitive indicators such as the bluebushes and saltbushes may occur only as old, well-chewed individuals or where they are protected by larger shrubs.

• Straight-leaved cassia, prickly acacia and wait-a-while occur more frequently as seedlingsand young plants. More bindiis are present.

• Cryptogamic crusts are still fairly obvious and there is generally no soil erosion.

C H A P T E R 5

71

This stony bluebush community near Leinster is inpoor condition. A few low decreaser shrubsincluding George’s bluebush and frankenias can beseen. There are many three-winged bluebushes in theforeground and abundant young needlebushes in thebackground. Needlebush is a potent increaser in thisvegetation type. Soil surface condition is fair togood and protected by a mantle of quartz stones.

This stony bluebush site in the Gascoyne is derivedfrom rocks which characteristically weather toclayey soils that support abundant low shrubs. Thisvegetation is in poor condition with no decreaserlow shrubs and only sparse wait-a-while and royalpoverty bush (4 per centihec) mainly evident in thebackground. Soil surface condition is still good,being stable with obvious cryptogam crusts.

Poor condition• Relatively thick stands of wait-a-while, prickly acacia present.

• Palatable species may be absent or present only as heavily grazed relics.

• Some bush mounds are degraded and run-off is increased.

• Few cryptogamic crusts present.

• Minor or moderate sheet and channel erosion can be present.


72

Greenstone slopesExtensive areas of upland country whichcover metamorphosed volcanic rock occurthrough the Murchison and Goldfields. Theseare known popularly as the greenstones orgreenstone belts and contain the major goldand nickel deposits plus a varied assortmentof other minerals which are very beneficialfor plant growth. The country can be veryproductive and is usually considerably morefertile than similar granite or stony bluebushcountry because of the presence of the extraminerals. Some basalt and dolerite is hardand resistant to erosion while other rocks aresofter. Land systems which typify thiscountry include Austin in the Murchison, andGundockerta and Leonora in the north-eastern Goldfields.

Some of the most typical and distinctiveexamples of greenstone country are found inthe Goldfields around Leonora, Laverton andMenzies. In these areas the land has beenused extensively for both mining and pastoralactivity, mainly wool production. Very littlegreenstone occurs west of a line fromMeekatharra, Cue to Yalgoo.

Trees and perennial grasses are sparse butthere is a diverse mixture of scattered low,medium and tall shrubs.

The overstorey of the vegetation oftenincludes black oak or scattered eucalypts(south of Menzies), sparse needlebush andmulga. Understorey shrubs may be bladderand silver saltbush, cotton bush, sago bush,sage, George’s bluebush, three-winged

bluebush, false bluebush (well south ofKalgoorlie and on the western Nullarbor)or pearl bluebush (higher up the slope andgenerally south of Leonora). Samphire maygrow on saline slopes and broom bushappears on the less alkaline sites, usuallyon rising ground. A wide range of othereremophilas may also be present includingpixie bush.

The most sensitive decreasers areGeorge’s bluebush and the saltbushes.Feather spear grass is a common perennialwhere land is in good condition andneverfail often grows in drainage holes.

Annuals in season may includeeverlastings, large white paper daisy andpurple mulla mulla.

When land is degraded there is an increasein species such as desert cassia, tan wattle(south of Menzies), needlebush, three-winged bluebush and hop bush, while otherlow shrubs decline. Sago bush can occupysites that previously supported morepalatable species such as bladder saltbush,but this may not mean a lower grazingvalue. If pearl bluebush or sago bush is theonly shrub in the understorey it usuallyreflects previous overgrazing.

When shrubs are lost the annual speargrass and bindii numbers increase.

C H A P T E R 5

73

Likely range condition changesGreenstone country supports a variedpopulation of tall and low shrubs with thevariation between different sites resultingfrom different environmental and grazingimpacts.

Moderate grazing can result in some loss ofbladder and silver saltbush and smallbluebushes, but very little change in thenumber of pearl bluebush and perhaps someincrease in sago bush. In this condition, thevegetation retains its resilience and protectsthe soil surface from erosion.

Change from this stable state varies and willdepend on management and climate. Thecountry can be comparatively fragile wherethe stone mantles are not heavy. Conservativeuse and favourable seasons may lead to therecruitment of decreaser shrubs although thisrequires a seed source. More commonly,conservative use results in more George’sbluebush, sago bush and cotton bush.Continued heavy grazing results in furtherreductions in the low shrubs, and dependingon climatic events and the presence of seedsources, may encourage a dramatic increasein woody weeds such as needlebush. In somesituations, particular climatic events seem tohave led to a ‘take-over’ by three-wingedbluebush which may occupy a site for ten totwenty years.

Good news signs• Young saltbushes, George’s bluebushes,sago bushes

• Well branched low and medium shrubs(not hedged)

• Healthy bush mounds

• Well developed soil surface crusting

Bad news signs• Too much cotton bush

• Well grazed pearl bluebush and sagobush are the only plants present

• Young needlebush, desert cassia andhop bush

• Surface sealing and crust disturbancebetween shrubs


74

Good condition• Diversity of low and medium shrubs present such as George’s bluebush, sago bush, sageand bladder saltbush.

• A range of mixed age plants present on non-stony surfaces.

• Soil surface crusting should be evident on non-stony areas.

• Almost no young increaser plants present.

This greenstone slope on the Leonora common is in good condition. The wide range of low shrubs presentincludes George’s bluebush, cotton bush, sago bush, silver saltbush and felty bluebush. Further up the slope (inthe background) pearl bluebush is growing. Shrub numbers and annual vegetation production are highest insmall depressions that gain water from surrounding areas (shown in the middle ground). This photograph wastaken in September 1993 after two good seasons which resulted in abundant annual growth.

C H A P T E R 5

75

Scattered mulga and needlebush grow on this greenstone slope east of Leonora which is in fair to poor conditionwith a much reduced low shrub population dominated by hardy sago bush and sage. Cotton bush, which canincrease in such situations, is also obvious. Annual grass and herb production can be high in good seasons suchas when this photograph was taken in 1993.

Fair condition• Vegetation dominated by long-lived shrubs such as pearl bluebush, sago bush and sage.

• Few young decreaser species present.

• Increase in numbers of three-winged bluebush and cotton bush.

• Reduced soil surface crusting evident.

• Smaller bush mounds and signs of water flow between mounds.


76

This greenstone country east of Leonora is in poorcondition with few low shrubs surviving below oldneedlebushes. Some saline samphire plants can beseen in the background, but these are generallyresistant to grazing. Although the site is in poorcondition, the inherently high soil fertilityencouraged abundant growth of annual vegetationin the good 1993 season.

Young needlebush have taken over this alluvial plain ingreenstone country east of Leinster. Few decreasershrubs are evident, mainly old, resilient sago bush andsage. The needlebush plants appear to be of similarage, suggesting they became established in aparticularly favourable time (perhaps the wet mid-1970s). Their presence will profoundly alter the natureof this site for many years to come.

Poor condition• Distinct loss of decreaser shrubs, often leaving only sago and pearl bluebush, and notmany of them.

• More increaser species such as three-winged bluebush, needlebush, desert cassia, hopbush and some eremophilas. Three-winged bluebush dominates some sites.

• Possible loss of all shrubs with only bindiis and spear grass remaining.

• Reduced soil surface crusting and minor sand piling against fallen trees.

• Further loss of bush mounds through trampling, wind erosion, water erosion.

C H A P T E R 5

77

Meekatharra

PERTH

Carnarvon

Kalgoorlie

Goldfields water pipeline. Around 1904more than half a million tons a year wasbeing harvested in this way. Many treeshave now grown back to full size,sometimes in coppice form (multiple trunksfrom an old base). Recruitment from seedis common.

Trees are now more numerous on manysites than before European settlement.

Goldfields gum beltWithin the Goldfields lies an extensive areacovering about 200 kilometres by 150kilometres and extending from south ofMenzies to the north of Lake Moore, east toZanthus and west to the farming belt wherethe overstorey vegetation comprises a rangeof eucalypts instead of the more usualacacias such as mulga, snakewood and wait-a-while. The Graves and Campsite landsystems in the north-eastern Goldfields areexamples.

Much of the area has never been used forgrazing, particularly where the eucalyptsform a thick woodland. The areas ofsaltbush and bluebush between Kambaldaand Menzies provide some of the bestgrazing country in the shrublands but theiruse is hampered by lack of freshgroundwater. This changed for manypastoralists when large dams wereexcavated using heavy machinery afterWorld War II, and more recently during thegold mining boom. Pipelines have been runfrom the dams to open up grazing in newareas.

The main Goldfields eucalypts includesalmon gum and gimlet with less extensiveareas of York gum, several differentblackbutts and many others – reputedly upto a quarter of all Australian species.

In the early days of mining, larger treeswere felled extensively for firewood, miningand building timber, railway sleepers andfuel for the pumping stations on the

However, there are fewer salmon gums inthe broad valley floors that support densesaltbush and bluebush. These shrubs maybe suppressing the regrowth of eucalypts.

Soil depth is variable and the eucalyptsfavour alkaline loams where the soil issufficiently deep above the underlying


78

C H A P T E R 5

granite and greenstone. Granite is oftenvisible as outcropping rock. The eucalyptsbecome smaller, more scattered and moredrought tolerant as rainfall declines.

Fertile patches or groving effects existaround crabholes or drainage areas whereeucalypts are taller and thicker.

The most important shrubs are bladdersaltbush and pearl bluebush followed bysago bush, old man saltbush and frankenias.Several shorter-lived bluebushes such asfelty bluebush and George’s bluebush alsogrow widely.

Pearl bluebush is a valuable stabiliser of thelandscape and feed reserve in this countrybut is not grazed heavily if more attractivealternatives are available. It is relativelyunresponsive to season and new plantsappear to germinate if rain falls just afterfruiting. In ungrazed areas on GindalbieStation where plants were monitored foreleven years, numbers of pearl bluebushremained unchanged at around 6 plants percentihec on ungrazed sites. There wasneither recruitment of new plants nor majorloss of old plants although numbers of othershrubs such as bladder saltbush, broom bushand short-lived bluebush species waxed andwaned with season. Scientists believe that adramatic loss of pearl bluebush should beregarded as a catastrophe and any increaseis a bonus that should be cherished.

In contrast, bladder saltbush responds toboth season and grazing and new plants mayestablish even in fairly dry years. On

Gindalbie Station plant numbers doubledafter thirteen years of protection fromgrazing, but high losses were observed evenin exclosures during very dry years.

Old man saltbush is more plentiful onovergrazed country and appears to recruitmore readily when grazed. Plants can growvery big and may reach the size of a room.They are not very palatable but sheep willeat them when good water is available.

Tan wattle, three-winged bluebush, desertcassia, hop bush and broom bush areincreasers.Vegetation can be dense in the gum belt andoccasional fires occur after good seasons,for example early 1994 and the mid-1970s.At these times useful shrubs such asbluebush and saltbush are replaced bydesert cassia and tan wattle. Pearl bluebushappears to survive fires better than bladdersaltbush and has been known to regeneratefrom the roots after five years.

The presence of particular eucalypts can bea useful indicator of soil type. Goldfieldsblackbutt commonly grows with pearlbluebush on shallow clay loams on therises, while gimlet and salmon gumscombine with saltbushes on heavier soils invalley floors.

79


Good news signs• Young bladder saltbush, pearl bluebush,sago bush present

• Other bluebushes present

• Good soil surface crusting

Bad news signs• Heavily chewed pearl bluebush and littleelse present

• Young increasers present such as desertcassia, tan wattle, hop bush

• Sealed soil surface, rilled in places

This open plain in the eastern Goldfields is in good condition. The shallow loam soil formed on weatheredgreenstone supports abundant bladder saltbush which is obvious in the foreground. The taller shrubs in themiddle ground include broom bush, desert cassia and old man saltbush. The soil surface is well crusted andsupports annual spear grasses. Shrub numbers are lower in the areas underneath the gum trees in thebackground.

Good condition• Plentiful bladder saltbush and pearlbluebush growing beneath eucalypts; somesilver saltbush and sago bush.

• Smaller bluebushes present includingGeorge’s bluebush and felty bluebush.

• Extensive cryptogamic crusting present.

80

C H A P T E R 5

This open woodland west of Menzies is in fair to good condition with low shrubs limited by competition from thegum trees which grow in a groving pattern. Bladder saltbush is obvious in the foreground with some bluebushunder the trees in the middle ground. Dry annual spear grass is abundant following good seasons in 1992 and1993. The soil surface is stable although less productive areas are covered by small ironstone pebbles(foreground).

Fair condition• Fewer saltbushes present, bluebushes are more dominant.

• Reduced species diversity; longer lived shrubs are smaller and more rounded.

• Some desert cassia and hop bush evident, more cotton bush and old man saltbush.

• Some breakdown of soil surface crust.

81


This site north of Kalgoorlie has lost nearly all the decreaser low shrubs normally occurring in this country. It is inpoor condition with only tall salmon gums remaining. Some gum tree recruitment is occurring in the middleground. Soil surface condition is fair with some obvious sealing limiting growth of annual plants. This photograph,taken in January 1994 after two good seasons, shows abundant dry annual grass and herbs.

Poor condition• Few or no pearl bluebush plants are present.

• Old man saltbush showing effects of grazing.

• Tan wattle, desert cassia and hop bush are present in larger numbers.

• Surface sealing and loss of crust.

• Evidence of water erosion in valley floors.

82

Meekatharra

Kalgoorlie

PERTH

Carnarvon

C H A P T E R 5

Flood Plains and River FrontagesThis type of country includes the floodplains of the major river systems, theGascoyne, Murchison, Ashburton,Greenough, Minilya and Wooramel, whichflow westward to the Indian Ocean. Insome cases the flood plains are narrow beltsclose to the river beds, but may be 20kilometres wide along parts of theGascoyne and Murchison Rivers. Typicalexamples are the Delta land system of theCarnarvon Basin, the Beringarra landsystem of the Murchison and the Edwardland system of the Ashburton. While thenorth-eastern Goldfields lacks rivers, theWilson land system around majorephemeral creeks shares similar vegetationand soils.

In an undegraded state the soil is relativelyfertile, favoured by overbank flooding ofwater and sediments plus channelleddrainage. Because of the attractive feed,water and shade, river frontages arefavoured by both native and feral animalsand have been used heavily. Most earlyshearing sheds were sited close to the riversso the grazing pressure at shearing waseven greater than normal.

Soils are mostly loam over clay, and rangein colour from red-brown to red-grey.Depth varies depending on soil conditionwith some soils more than a metre deep,while others are shallow and eroded.

Overuse causes loss of many palatableshrubs and instability in the topsoil layer.The most susceptible soils are sandy at thesurface. The action of water and wind canscald, scour and create hummocks indestabilised soil, and some unfortunateexamples of this are common.

This is an all or nothing system!Maintaining adequate plant cover isessential. If shrubs are removed, soilerosion will follow almost inevitably. Majordegradation can occur and regeneration willbe extremely difficult. On degraded siteswoody weeds may invade and help torestabilise the soil. The critical level of

83

Fair(Loss of saltbush)

very light grazing

(Saltbush plains)

dry seasons and/ or heavy grazing

Clumped woody weeds

Bare eroded plains

Poor(Further loss of

shrubs, loss of soil)

heavy grazing

Good

plant cover appears to be at least 10 percent. Large areas should be fenced off toallow specific management.

The start of active soil erosion representsthe passing of a threshold from whichregeneration will not be achieved merely bymanipulating grazing pressure. It istherefore very important to monitor changesin vegetation to prevent crossing thisthreshold.

Likely range condition changesFloodplains and river frontages are fertileareas supporting a diverse range ofdecreaser shrubs, which rapidly erode whendisturbed. In the natural state these plains,

with their abundant plant cover, tolerateoccasional floods and windstorms withoutsignificant soil loss. The low shrubs areadapted to grazing. Moderate grazingstimulates growth and confers some‘drought proofing’ on species such as shybluebush.

Excessive grazing, especially in dry years,kills the less hardy perennial species such asbladder saltbush, silver saltbush and shybluebush. Excessive animal activity in drytimes cuts the soil surface which is then lostthrough floods and strong winds, exposinghardpan or clay subsoils. This transition canoccur over just a few years. Once thisthreshold is crossed, the topsoil and its


Likely range condition changes in flood plains.

84

C H A P T E R 5

associated plants cannot be replaced. Theerosion process and recovery of non-erodedparts of the landscape gives the characteristic‘islands of stability’ structure to the partiallydegraded state. Continued erosion of theseislands produces the totally degraded state ofbare, scalded flat with sandy accumulationsof eroded surface materials.

Woody weeds such as needlebush andprickly acacia colonise these sandy banks.Where useful summer rain falls, such asalong the Ashburton River, buffel grass isalso an active coloniser.

Nutritious annual species grow prolificallyafter seasonal rains and animals continue toobtain good grazing from these degradedsystems for short periods of the year.

Degradation is seen most clearly as the lossof individual plants followed by destructionof bush mounds. Unless this can be reversed,continued grazing leads to further loss ofperennial plants and loss of topsoil – whichhas happened to extensive areas. To preventirreversible damage, germination of newsaltbush or bluebush is required, followed byplant growth and increase in size of themounds.

Low saltbush and bluebush shrubland is themain vegetation and has considerabledrought durability when in good condition.Perennial shrubs are augmented by biennialssuch as bindiis, plus annual grasses andherbs in good seasons.

Saltbush communites are more sensitive tograzing than bluebush and will be eaten out

allowing soil erosion if country is notmanaged properly.

Trees to 4 metres high and tall shrubs to 3metres are diverse but scattered, and mayinclude wait-a-while, prickly acacia,curara, needlebush and coolabahs.

Leaves of prickly acacia (often known asbardi bush for the bardis or witchetty grubswhich inhabit it) appear quite bluish onyoung plants which are unpalatable, but areyellowish green on more mature plants.

Coolabahs are distinctive white-trunkedeucalypts growing along creek beds andclose to rivers. River gums, which lookvery similar, only grow close to permanentwater.

Medium shrubs including green cassia (alsocalled tall cassia), crinkled cassia, mingahbush and tall saltbush are common.

Low shrubs are dominant and diverse andmay include George’s bluebush, shybluebush, spiny bluebush, swamp saltbush,bladder saltbush, silver saltbush, flannelbush, samphire, frankenias and riversaltbush. Gascoyne bluebush is present insome areas.

These plains support high quality annualplants in good seasons. In winter theseinclude everlastings, billy buttons andsmall salt-tolerant plants such as the bindiisand annual mulla mullas. Summer raincauses germination of bindiis and someshort-lived grasses such as love grass andwind grass.

85

Indicator Good Fair Poor

Introduced buffel and Birdwood grasseshave colonised areas near the northernrivers. Their growth provides an appealingbiomass for both stock and native animals,but after a growth flush protein levels falland animals graze remnant shrubs heavily inan effort to maintain protein intake. Suchbuffel grass colonisation may also changethe habitat for fauna.

Increaser shrubs on the river frontagesinclude prickly acacia, needlebush, silverpoverty bush, straight-leaved cassia andcrinkled cassia.

The best indicator of range condition is thenumber of saltbushes and bluebushespresent, though precise numbers will dependon the dominant species. For examplemature silver saltbush plants are larger thanbladder saltbush so numbers per centihecwill be lower for country in similarcondition.


Good news signs• Abundant bush mounds supportingdecreaser species

• Young saltbushes, bluebushes

• No erosion

• Abundant cryptogamic crusts

Bad news signs• Many young needlebush, prickly acacia,silver poverty bush, cassias

• Dominant vegetation is increasers –prickly acacias, wait-a-while

• Breakdown of bush mounds

• Onset of soil erosion, bare scalded areas

• Poor cryptogamic crusts, powdering ofsurface crusts

Numbers of bladder saltbush >80 40-50 <20plants per centihec

Numbers of silver saltbush 30-50 20 >10plants per centihec

86

C H A P T E R 5

This river frontage country close to the Gascoyne River is in good range condition with a plentiful cover of thedecreaser low shrub, bladder saltbush. Another sign of a healthy community is the mixture of even-agedsaltbushes. The soil surface is stable and the areas between the shrubs are supporting annual grasses and herbsin this good 1992 season.

Good condition (bladder saltbush areas)• Bladder saltbush is dominant, and may occur as thickly as 250 plants per centihec,averaging about 80. This is the most useful indicator.

• Other palatable plants such as sage, green cassia, Wilcox bush and various bluebushes arealso present.

• Occasional prickly acacia, needlebush, wait-a-while and silver poverty bush may be seen.

• Good cryptogamic crusts are present.

• There is little or no erosion.

87

This Wooramel River frontage is in fair condition. In the foreground the soil remains intact with reasonablenumbers of Gascoyne bluebush and some young needlebush. The system is vulnerable to water and wind erosion.In the background of the photograph surface soil has been lost due to the action of water and wind. This mosaicpattern of stable and eroded soil surfaces is typical of river frontages.


Fair condition (bladder saltbush areas)• The number of bladder saltbush plants falls to 40 to 50 per centihec.

• Bush mounds are slightly reduced in size and elevation due to both the removal ofsurrounding soils through water and wind erosion and their local redeposition.

• Cryptogamic crusts are still present but some breakdown has occurred.

• Occasional minor to moderate soil erosion may be present.

88

This Murchison River frontage country is in poor condition with vegetation reduced to scattered needlebush andprickly acacia and a few remnant low shrubs on residual soil surfaces. More than half of the area has lost soil towater erosion, leaving a hard sealed surface that is almost impermeable. This is a very difficult environment forplant establishment and the country was probably overstocked in the early days of pastoral development.

C H A P T E R 5

Poor condition (bladder saltbush areas)• If the bladder saltbush numbers fall below about 20 per centihec, the total vegetationdeclines sharply also.

• Other palatable species are rarely present and the range of perennial species is usuallynarrow.

• Some invasion of increaser shrubs such as needlebush.

• Cryptogamic crusts are generally absent.

• Moderate to severe erosion in the form of scalding, hummocking, gullying and sheeting isoften apparent.

89


Good condition (silver saltbush areas)• Silver saltbush may occur from 30 to 80 plants per centihec.

• The low shrubs ruby saltbush, felty bluebush, ragged-leaf fan flower, Gascoyne bluebushand flat-leaved bluebush may be present, but distribution is patchy and absences do notnecessarily imply poor condition.

• Cotton bush, tall saltbush and flannel bush are commonly present at about 5 to 10 plantsper centihec.

• Increasers such as wait-a-while, tomato bush, prickly acacia and needlebush may bepresent but in very low numbers.

Fair condition (silver saltbush areas)• Overgrazing causes silver saltbush to decline and numbers fall to 10 to 20 plants percentihec with some plants grazed back to unpalatable woody material.

• Other decreasers may still be present but in smaller numbers.

• Cotton bush may increase in number as other shrubs disappear.

• Increaser shrubs rise slightly in number.

• Fair cryptogamic crusts, but partial breakdown of crusts in some places.

• Occasional minor wind and water erosion may occur.

Poor condition (silver saltbush areas)• If silver saltbush numbers fall below about 10 per centihec, the total vegetation declinessharply also.

• Degraded sites may be invaded by unpalatable larger shrubs such as needlebush, pricklyacacia, crinkled cassia and silver poverty bush.

• Bush mounds are nearly all remnants, greatly deflated, with no surviving bushes on them.

• Cryptogamic crusts are poor or absent.

• Wind erosion is common in the form of hummocking while water erosion occurs asrilling, gullying and sheeting.

90

PERTH

Carnarvon

Meekatharra

Kalgoorlie

C H A P T E R 5

Dense saltbush and bluebush shrubs arethe dominant plants of the level plains,which cover large areas of very valuablepastoral land north and south of Carnarvonand in the ancient drainage systemsthrough the Murchison and Goldfields.These drainage systems flow eastward intolocal salt lakes, unlike the main riverswhich flow west to the sea.

Good examples can be found in the Sableland system of the Carnarvon Basin andthe Carnegie land system of theMurchison.

Some of the salt lakes are very large,extending to 70 kilometres long. The lakebeds are bare of vegetation and some areused for sporting activities. Soils are verysaline close to the lakes but with distancegrade to less saline alluvial plains whosepastoral use is limited by supplies of freshwater.

In general, this country type is almostidentical to the river frontages and floodplains, but is much less prone todegradation. The plains are almost flatwith gradients less than one in threehundred. Soils are fairly deep loams overclay. They are normally internally drainedwith crytogamic crusts covering more thanhalf the soil surface.

A distinctive pattern of shrub mounds,creating individual fertile patches, is afeature of the landscape. In these mounds

the fertility and water infiltration are muchhigher than between the mounds. Theirdensity and size are a very good guide tocondition.

Decreaser shrubs are very similar to thosegrowing on the river frontages. They includeshy bluebush, bronze bluebush, George’sbluebush, bladder saltbush, silver saltbush,frankenias, Gascoyne mulla mulla, cottonbush, scrambling saltbush, Gascoynebluebush, currant bush and sage. Sage is oneof the toughest decreasers.

The variety of these species falls withdeclining condition and in the north-eastern

Level Plains and Lake Frontages

91

Fair(Fewer species,

occasional erosion, conspicuous increasers,

plant cover reduced)

good seasons with light grazing

Good(Many species, no increasers, good perennial

plant cover)

dry seasons and/ or heavy grazing

Poor(Loss of more decreasers,

increase in annuals)

heavy grazing

A major study over ten years wasconducted at Boolathana Station nearCarnarvon and completed in 1993.Following sustained heavy grazing, thenumbers of shy bluebush, Gascoynebluebush and other perennial shrubsdeclined sharply but in good years the lossof forage from this ‘degraded’ range wasmore than overcome by increased growthof annuals and biennials such as bindiis.

At conservative stocking rates within thelong-term capability of the range therewere no gains in animal production (woolor lambs) from sheep grazing numerouspalatable shrubs compared with thosegrazing very few shrubs. However at highstocking rates sheep on the degraded rangehad to be hand-fed in four of ten years to


Goldfields ranges from seven to ten speciesfor good condition country, around seven forfair condition and less than seven in poorcondition.

Most important increasers are needlebush,tomato bush, desert cassia, silver povertybush and wait-a-while. Kopi poverty bush iscommon in the north-eastern Goldfields.

In degraded sites sandy accumulations formaround annual plants which grow after rain.If these sandy accumulations persist theyprovide a niche for shrub germination.Some observers believe that successfulshrub establishment depends on avoidingdisturbance by animals, so conservativestocking and reduction of total grazingpressure are important after significantrainfall.

Likely range condition changes in level plains.

92

prevent losses, while the non-degradedrange supported sheep without extrafeeding.

Prominent or dominant low shrubs varywith geographical location and localfactors. For example, in more saline areasclose to salt lakes, the dominant shrub willbe a form of samphire. Two differentvarieties are common and the green oneappears much more palatable than thebrown, which has limited appeal to stockexcept when growth is fresh.

A short distance away as salinity levelschange, the dominant species may be silversaltbush or bladder saltbush. This country isvery valuable for pastoral use but the loose,coarse textured sandy surface may be lost towater and wind erosion without carefulmanagement. Once this occurs, the soilsurface can become smooth and niches forregeneration of perennial plants are limited.

The main indicators of condition are verysimilar to those for the flood plains andriver frontages except that the soil is morestable to erosion. Soils are normally mostsusceptible to water erosion in areasreceiving relatively concentrated run-on.Wind erosion can be a problem duringprolonged dry periods.

Good news signs• High diversity of species

• Young and healthy saltbushes,bluebushes present

• Intact bush mounds around the shrubs

• Abundant cryptogamic crusts on soilsurface

Bad news signs• Absence of young low or decreasershrubs

• Reduced diversity of species

• Many young increaser shrubs present• Very patchy or no cryptogam crusts• Signs of wind drift at surface

C H A P T E R 5

93

Good condition• Saltbush species such as bladder saltbush, silver saltbush are prominant.

• Other palatable plants such as sage, green cassia, Wilcox bush, bluebushes, cotton bush,tall saltbush, flannel bush and samphire are also present.

• Occasional prickly acacia, needlebush, wait-a-while and silver poverty bush occur.

• Good cryptogamic crusts are present.

• There is little or no erosion.


This level plain north of Carnarvon is in very goodcondition. The Gascoyne bluebushes number about 8per centihec and the soil is stable and well crusted.The taller shrubs are mainly prickly acacias (2 percentihec). Less obvious shrub species are flannelbush, warty-leaf eremophila, crinkled cassia andberry saltbush. The bush mounds below the Gascoynebluebushes are important ‘sinks’ for plant nutrientsand organic matter.

This lake frontage south-east of Leonora is in goodcondition with a diverse array of low shrubsincluding sage, sago bush, grey fan-leaf, threewinged bluebush, frankenia, silver saltbush, George’sbluebush and sweet samphire evident in thephotograph. The shallow duplex soil overlies ahardpan layer. Soil surface condition is good withobvious well developed shrub mounds. The treelessplain is surrounded by low sandy banks supportinglarge mulgas.

94

Fair condition• Fewer saltbush plants are present.

• Other palatable plants are present but only in low numbers, with some plants grazed backto unpalatable woody material.

• Bush mounds are slightly reduced in size.

• Cryptogamic crusts are still present.

• Occasional minor soil erosion may be present.

C H A P T E R 5

This small, gritty surfaced alluvial plain east ofLeinster is surrounded by more sandy plains withbuck wanderrie and spinifex. Shrub numbers arebelow the site’s potential and condition is betweenfair and good. The dominant shrub species are thosemost resistant to grazing overuse and includefrankenia (foreground), sage (the big plant in themiddle of the photograph), tall saltbush and sagobush. Other saltbush plants that could be expected inthis country are conspicuous by their absence. Soilcondition is fair to good.

This Gascoyne bluebush site just north of Carnarvon isin fair condition. The soil is duplex with a loamy sandlayer about 25 cm deep over sandy clay-loam. This istypical of the level plains found along the coast betweenthe Wooramel and Minilya Rivers and has few perennialplant species. Gascoyne bluebush plants dominate thearea (8 per centihec) with a few wait-a-while andprickly acacia. More could be present. The photographwas taken in mid-summer 1981 when dry annual growthremained from a very good season.

95


Poor condition• Sparse saltbushes are present.

• Other palatable species are rarely present and the range of perennial species is usuallynarrow.

• Some invasion of increaser shrubs such as needlebush, wait-a-while, tomato bush andprickly acacia.

• Cryptogamic crusts are generally absent.

• Moderate erosion is often apparent.

A degraded level plain north of Carnarvon. The site,which would have once supported Gascoyne bluebush,is now dominated by prickly acacia (4 per centihec)which is an increaser species. Low shrubs are sparsewith none evident is this photograph. The soil surfaceis in fair condition with some crusting and modestgrowth of annual vegetation.

Virtually all the decreaser shrubs have disappeared fromthis alluvial plain near Leonora which is in very poorcondition. A few hardy sage and grey fan-leaf plants aresurviving but have been grazed heavily. Soil surfacecondition is fair with evidence of sealing. The low andtall shrubs in the background are growing on a lessfavoured but more resilient country type.

96

Meekatharra

PERTH

Carnarvon

Kalgoorlie

C H A P T E R 5

Nullarbor PlainThe first European explorers includingEdward John Eyre and Ernest Gilestraversed the Nullarbor Plain as long ago asthe 1840s, but development was slowdespite favourable first impressions.Pastoral settlement began at Mundrabillaand Balladonia Stations in the 1870s withsheep driven overland from Albany.However, lack of underground waterdelayed further settlement, and atBalladonia earth tanks had to be dug byhand to collect water for the stock.

During World War I the transcontinentalrailway line was built across the Nullarbor,and World War II spurred construction of amain road closer to the coast linking WAand South Australia. But much of the WAarea remained vacant Crown Land until1961 when additional areas were openedfor grazing.

The Nullarbor Plain is the most southerlyof WA’s rangelands and its rainfall is veryvariable, falling mainly in the winter withthe passage of eastward movingdepressions. Falls are heavier closer to thecoast (about 250 millimetres) but decline toabout 150 millimetres or less north of thetranscontinental railway line. These moreinland areas are colder in winter and hotterin summer.

The Nullarbor region, or Bunda Plateau asit is also known, is one of the largestlimestone plains in the world. Soils arepaler in colour (more of a buff) than most

of the rangeland and are shallow silty loamswhich tend to be stable except whendisturbed. Rainfall infiltration is low tomoderate and run-off drains into largeshallow depressions, some known asdongas. Groundwater is generally deep –75 to 150 metres – and often highly saline.Stony rises occur in some areas and verydark cryptogams are widespread.

The name ‘nullarbor’ means no trees andwas coined from the Latin in 1866 byDelisser, an explorer for the SouthAustralian Government. However hisdescription applies to only part of the totalarea, the Nullarbor land zone, most of

97

which is north of the Eyre Highway.Leaving the centre of this treeless area, thevegetation becomes progressively taller,first with medium shrubs and sparse trees,and then into woodland. The distinctivetree species of the region is the westernmyall, and close to the coast eucalypts andsugarwoods also grow abundantly. Northand west of the treeless shrubland the maintree species are mulgas, blackoaks andsugarwoods.

No major rivers or lakes occur on theNullarbor, but run-off after rain flows intolocal drainage areas, either claypans ordongas. Dongas are a distinctive localfeature occurring away from the centre ofthe Nullarbor. Their floors contain gilgaiswhich are small mounds and depressionsassociated with uneven shrinking andswelling of clay soils. Large limestoneboulders have been brought to the surfaceby these forces in some areas. Dongas maybe up to a kilometre across and aregenerally round. They usually occur inchains and are thought to lie above jointsin the underlying limestone which issometimes dissected by deep caves.

Most dongas support sparse trees, mainlydesert willow and curara. They are notsaline, possibly because of the rapidvertical drainage through the floors. Goodquality water is sometimes found beneaththem.

Elsewhere, the drainage units are claypanswhich lack both the tree cover and gilgai

development of the dongas.

Besides its distinctive landform, themodern Nullarbor has been shaped by twospecific agents indirectly and directlyintroduced by European man – rabbits andfire.

Rabbits were introduced to Australia in1859, spreading gradually overland fromVictoria. By 1900 they had found a nicheon the Nullarbor where they were able tolive underground and eat only the mostsucculent parts of the plants, from whichthey obtained enough water to survive. Ingood seasons their numbers soared, rapidlyreaching plague proportions, stripping allavailable vegetation and contributing toland degradation.

In 1947 it was reported that a team of thirtyfive trappers near Cocklebiddy wascatching 20,000 rabbits a week, but thenumbers were later reduced bymyxomatosis.

Today rabbit populations remain very highand research in 1991 indicated that warrendensities were frequently between 100 and200 per square kilometre. This comparedwith three to twelve in other arid areas.Rabbits strip bark and leaf from shrubs tograzing height and have killed many shrubsand trees.

Bushfires are believed to be a naturalfeature of the environment resulting fromsummer thunderstorms after good seasons.They became more frequent in the era of


98

GREAT AUSTRAL IAN B IGHT

Saltbush and bluebush plains

Medium shrubs and sparse trees

Woodland

Rawlinna

Caiguna

Forrest

Eucla

Cocklebiddy

Trans Australian Railway

Eyre Highway

N u l l a r b o r P l a i n

GREAT VICTORIA DESERT

steam trains resulting in loss of shrubs andinvasion by annual grasses near thetranscontinental railway line. Thecombination of rabbits and fire has changedthe vegetation dramatically. The burnt areasare now dominated by annual grasses andherbs. Such grassy country is often knownas the Nullarbor herb field or prairie. Someof the most obvious examples are foundclose to the railway line and highway.

The time for re-establishment of vegetationafter fire is unknown, but in somesituations perennial vegetation may never

return. Elimination of shrubs results incolonisation by more annual grasses, whichin turn renders the burnt areas moresusceptible to further burning and so thecycle perpetuates.

Annual grasses such as spear grass areextremely common, especially in degradedcountry. Perennial grasses are infrequent,the main species being neverfail andcommon wallaby grass or white top.

The main shrubs throughout the Nullarborregion are pearl bluebush and bladdersaltbush with the bluebush favouring the

C H A P T E R 5

99

rises and saltbush hugging the depressions.Samphire covers some saline areas whichtend to grow fewer annual grasses, and aretherefore less prone to fire.

Bladder saltbush is a relatively short-lived(maybe twenty five years), shallow-rootedshrub, growing to about 45 centimetres.This is less than in some other areas. Itgerminates readily over the cooler months,and seedlings and young plants are verycommon after good rains.

Pearl bluebush, by contrast, has deep roots,grows more slowly, but can live for twohundred years or more. If removed, theyare difficult to regenerate except during arun of several exceptional seasons. Plantsgrow to about 45 centimetres high andabout 1 metre apart on well-grazed areas.In ungrazed areas the pearl bluebush istaller, about 1 metre, which makes it easyto distinquish from saltbush.

In a good season pearl bluebush shrubs canalmost disappear in a sea of annual grass.This can easily mislead casual observersabout the productivity of the area forgrazing – especially if they are unaware ofthe shortage of fresh water which haslimited its carrying capacity.

Higher rainfall areas to the south and westsupport a few medium and taller shrubsincluding false bluebush, broom bush,nitre bush and bullock bush (knownelsewhere as mingah bush). Western myall,sugarwood and some eucalypts (often

mallees) may also be present, especiallyclose to the coast.

Western myall is to the Nullarbor whatmulga is to the hardpan plains. It providesshelter and easily cut posts, some of whichhave endured for nearly a century. Butregeneration is limited if rabbits arepresent. Suckering is never seen andcoppicing is rare. Scientists believe thatwidespread natural germination onlyfollows heavy rain which may only happena few times a century. Large numbers ofseedlings germinate at such times,particularly when protected in naturalgroves, but the survival rate is very low.

For their first twenty years young myallsare very vulnerable to grazing by bothsheep and rabbits. If they survive this earlytime, the lifespan can be about two hundredand fifty years.

Weeds such as Ward’s weed and wild hopshave been introduced to some areas throughgrazing. Ward’s weed has good feed valuewhen young and appears to resist fire morethan grass.

The main indicator of condition is thedensity of the saltbushes and bluebushes. Ifland has been burnt the low saltbush andbluebush shrubs will be replaced by a goodcover of diverse herbs in most years. Desertcassias may invade some degraded areas.


100

Likely range condition changesAway from frequent fires, rabbits and stockhave reduced the shrub numbers leading tomore frequent grassy years, encouragingmore fires which are started by lightning.The outcome is a stable but more scatteredshrubland, with greater pearl bluebushdominance as this resists fire more thanbladder saltbush. This state is commonover much of the Nullarbor Plain and itsfringing woodlands, and is typified by thephotograph on page opposite left. This areahas not been grazed by domestic stock, butrabbit activity is very obvious.

Where major fires could once be expectedonly rarely after particularly high rainfall,the more flammable grassy vegetation nowresults in more frequent fires. Fires werevery extensive in 1974-76 and again overthe summers in 1992-94.

On large areas close to the railway line andthe Eyre Highway, frequent fires caused byhuman activity have almost removed theshrubs. With moderate or heavy grazing,this has encouraged a ‘herbfield’ of bindiis,Ward’s weed and other short-lived herbs.Spear grass still grows prolifically in wetteryears.

C H A P T E R 5

In areas that have received little or nograzing such as near the Eyre Highwaybetween Caiguna and Cocklebiddy thevegetation is dominated by spear grass thatusually exists as a dense stand of dry grass.This grassy state appears to be suppressingany likelihood of shrub recruitment fromremnant populations.

Good news signs• Young shrubs, plentiful saltbush andbluebush

• Diverse herbs present and good groundcover

• Lots of black cryptogamic crusts

• Plentiful shrubs of mixed ages and sizes

Bad news signs• No young shrubs, very scattered agedbluebush and saltbush

• Poor cryptogamic crusts, breaks in soilcrust

• Predominance of one or two annualspecies such as limestone bindii or Ward’sweed

101

This country between Rawlinna and Cocklebiddy istypical of the treeless bladder saltbush and pearlbluebush plains on the Nullarbor Plain. There isevidence of past shrub deaths caused by fire, but thesite is in good condition. The darker soil surfacecolour caused by the cryptogams contrasts with thedisturbed area on the track.

Vigorous bladder saltbush and pearl bluebush form astable shrub community beneath scattered westernmyall and sugarwood trees on the south-western edgeof the Nullarbor. The site is in good condition with verydark cryptogam crusting evident on the soil surface.


Good condition• At least 15 pearl bluebush plants and/or at least 30 bladder saltbush plants per centihec.

• Diverse grasses and herbs are present in season.

• Good cryptogamic crusts are visible.

• No erosion is present.

102

C H A P T E R 5

This site north of Cocklebiddy is in fair condition with an obvious reduction in the population of pearl bluebushand bladder saltbush on the slopes. In the more favoured locations on the drainage floor (darker green area inthe background) bladder saltbush is growing in association with samphire. The soil surface is still very stablewith good cryptogam crusting in the foreground and middle ground. The patches of white are limestoneboulders.

Fair condition• From 5 to 30 bladder saltbush plants and/or 4 to 15 pearl bluebushes per centihec.

• Land retains fair cryptogamic crusts.

• Diverse grasses and herbs in season.

• No erosion present.

103


Successive fires have profoundly altered this site on the southern edge of the Nullarbor Plain, changing it fromshrubland to annual grassland. Virtually all decreaser shrubs have been removed and it is unlikely that a seedsource now exists in the area. Spear grass grows prolifically in good seasons (such as 1992 when thisphotograph was taken) providing fuel for further fires. It is likely that the vegetation has been permanentlyaltered and is in poor condition compared with its original shrubby state.

Poor condition• Very sparse saltbush and bluebush shrubs. Dominated by limestone bindii if burnt.

• Abundant spear grass in very good seasons provides significant fire risk.

• Poor annual growth.

• Little or no cryptogamic crust.

• Minor erosion and redistribution of soil by wind may occur occasionally.

104

Spinifex dominated vegetation

Fire5-7 years

Range of short-lived palatable plants

ery sandy soils are a frequentfeature of many areas in therangelands, often producing some

of the most spectacular wildflowers. About afifth of the arid shrubland is sandplain –fairly flat to undulating plains covered withdeep, sandy soils which support a variety oftall shrubs or low trees and perennial grasses.

Sandplain areas sometimes extend for manykilometres, but in other places areinterspersed with other soil types. Soils arenon-saline and mainly red in colour. Theyabsorb rainfall well except in degraded siteswhere surfaces may become sealed, makingit difficult for plant germination. Except invery degraded sites accelerated erosion isusually absent.

Basic fertility of sandplain areas is very low,but their high infiltration rate allows plants totake advantage of relatively light showers ofrain. Four main types have been identified:Spinifex, Wanderrie, Bowgada andCurrant Bush Mixed Shrub.

SpinifexSpinifex is probably Australia’s best knownnative grass, and the name covers severalspecies that dominate large areas of infertilered sand. They are found in arid tracts of theeastern Goldfields, parts of the Gascoyne andAshburton. Very extensive areas also occur inthe Pilbara and other regions north and eastof the arid shrubland.

Spinifex grasses are known as hummockgrasses because they grow in low roundedhummocks, unlike the taller tussockgrasses. They are members of the Triodiaor Plectrachne genera.

Spinifex is usually labelled as either ‘hard’or ‘soft’, and while soft spinifex has someuse for grazing, the value of the moreextensive hard spinifex country liesbetween very low and useless – unlessrecently burnt when germination of morepalatable grasses and herbs is stimulated.

Spinifex grasses are well adapted to veryarid environments having narrow inrolledleaves and resinous exudates which help

Likely range condition changes.

Chapter 6 - Sandplain

105

This deep sandy plain carrying low gum trees and mulgas over old spinifex hummocks is south-east of Wiluna. Theblackened trunks and branches in the middle ground are evidence of past fires, although the moribund spinifexhummocks suggest that this site has not been burnt for some years.

minimise water loss. This resin also makesthem highly flammable.

Spinifex tends to dominate the vegetationwith varying numbers of trees and tallshrubs including mulga, marble gum, gidgeeand spreading gidgee.

Spinifex country’s greatest value for stock orother animals is about a year after fire andsubsequent rain, when diverse short-lived

grasses and woody herbs germinate. Thesegradually decline in diversity as spinifexregains dominance after about five years.Shrub cover falls below 15 per cent at thisstage.

The country is usually very stable, but winderosion is common on recently burnt areaswhich have yet to stabilise with seasonalgrowth.

S A N D P L A I N

106

Meekatharra

Kalgoorlie

PERTH

Carnarvon

WanderrieWanderrie country (pronounced wand’ryand sometimes spelt ‘wandarrie’) is one ofthe least understood vegetation types in theshrublands, and is scattered over extensiveareas of the Murchison River catchment,around Wiluna and through the north-eastern Goldfields.

The name wanderrie comes from a group ofperennial tussock grass species, commonlyknown as ‘wanderrie grasses’, which are aprominent feature and valuable grazingresource on many sandy soils. Wanderriecountry often exists as featureless grassyplains, although around the Murchison andGascoyne it also appears as ‘wanderriebanks’ up to a kilometre long and 100 to 200metres wide which are raised slightly abovethe general soil surface and escape floodingfollowing heavy rain. This difference intopography may be very slight and almostinvisible to the untrained eye, except whenindicated by a change in vegetation. Aerialphotographs often reveal a mosaic effect,with wanderrie floating in a sea of othervegetation, particularly mulga hardpanplains.

Vegetation varies considerably, but thecommon features include scattered shrubsand trees and an abundance of perennialgrass butts, particularly in good seasons.Local plant composition appears to dependon the rainfall in the past three to five yearsplus fire and grazing history of the area.

Although known collectively as wanderriegrasses, the individual grass species are notall from the same close botanical grouping.Creeping wanderrie and woolly butt are partof the Eragrostis genus while broad-leavedwanderrie, soft wanderrie and buckwanderrie are from three other genera, buthave the common link that they thrive insandy soils.

Woolly butt, also called wire wanderrie, isone of the easiest perennial grasses torecognise because of distinctive dense whitewoolly fluff at the base of the butts.Individual tussocks have been known to livefor twenty years and are palatable to

C H A P T E R 6

107

animals when green but fairly unpalatableand low in nutritive value as they dry off.Despite this, it is still one of the most usefulperennial grasses for grazing in theGoldfields and east of Meekatharra.

Buck wanderrie is generally unpalatable andis only grazed if there are few alternatives.When prevalent to the exclusion of morepalatable wanderrie grasses it indicates fairto poor range condition.

The most palatable wanderrie grasses aresoft wanderrie (sometimes called mulgagrass or barbed wire grass for the roughseed capsules) and broad-leaved wanderrie.Creeping wanderrie and woolly butt arerated as slightly less desirable but are thedominant species in some areas. Whengreen these grasses have a crude proteincontent of up to 15 per cent and are veryattractive to stock, but palatability andgrazing value decline rapidly as the grassdries off. They respond well to summer rainbut may be short-lived if the followingseasons are dry.

Even when perennial grasses are rare, ingood seasons the wanderrie banks supportlarge numbers of annual herbs such as mullamullas and everlastings, plus wind grass andfalse wanderrie grass. Summer rains favourthe growth of grasses which are veryflammable when dry, making occasionalfires possible.

Absorption of rainwater into the banks ismuch greater than on the sealed and crustedsurfaces between the banks, allowing more

S A N D P L A I N

efficient use of light rain. Wanderrie soilsare usually sand or loamy sand and resisterosion while they retain good perennialplant cover but can degrade under excessivegrazing pressure. Invasion of woody weedssuch as unpalatable poverty bushes maythen be possible.

The presence of broad-leaved wanderrie andsoft wanderrie is an indicator of good rangecondition but their relative abundance candepend heavily on seasons. Broad-leavedwanderrie germinates best after summer rainand may not persist as a perennial if seasonsare adverse.

False wanderrie grass is widely distributedin the more northerly areas of the Gascoyneand Murchison and resembles broad-leavedwanderrie grass. Most false wanderrie isannual in habit, low in palatability andremoved by trampling. Abundant falsewanderrie and wind grass in good seasonsusually indicate poor range condition.

Determining range condition is verydifficult in this country! In terms ofimmediate seasonal productive value forstock, wanderrie country is probably at itspeak when the number of perennial grassbutts is high. But the long-term health of therange may be reflected more accurately bythe number of palatable shrubs present.Carrying capacity of country with largenumbers of palatable grass butts could fallrapidly after two or three very dry yearswhile similar land supporting fewer grassesbut numerous palatable shrubs, would beaffected less by the seasons.

108

The palatable wanderrie grasses are notlong-lived and are sensitive to recentrainfall events, particularly summerrainfall. Their absence from a site may onlybe due to reduced germinating rain inrecent years. Another factor is the firehistory of a site which may only be evidentafter close search for burnt stumps. Woollybutt can be killed easily by fire and takessome years to recover.

Neither the shrubs nor the grasses alonecan act as reliable indicators of rangecondition, and it is possible to haveabundant wanderrie grasses associated withincreaser shrubs and few grasses withmany decreaser shrubs. Both vegetationcomponents need to be assessed in the lightof recent seasonal events to judge rangecondition.

Good news signs• Large numbers of palatable wanderriegrasses including young plants, particularlyif they are present in poor seasons

• Plentiful palatable shrubs such as mulgabluebush, including young plants

Bad news signs• Lots of false wanderrie and wind grassin good seasons

• Absence of palatable wanderrie grassesafter good seasons

• Increase in poverty bushes

• Little or no plant residue from previousseason’s growth

• Hummocks of sand around plant bases

• Bare and scalded areas

C H A P T E R 6

109

S A N D P L A I N

This wanderrie grass site in the lower Murchison hasexperienced a good winter season (1993) andsupports dense broad-leaved wanderrie and a littlewoolly butt. Virtually the only shrubs present aremulgas. It is possible that decreaser shrubs such asmulga bluebush were removed by past overgrazingand many observers would assess it as poor.Nevertheless, the site is still highly productive forsome months after rain.

This area west of Meekatharra supports only verydry buck wanderrie grass and Wilcox bush whichtends to be less palatable on such soils. It is notpossible to determine whether the absence of broad-leaved wanderrie and woolly butt is due to very dryseasonal conditions, overgrazing or combinations ofthe two. Assessment of condition is difficult but thesite is currently much less productive than itspotential, whether people focus on grass or shrubs.

Good long-term range condition• Usually an abundance of soft wanderrie, broad-leaved wanderrie, creeping wanderrie andwoolly butt present or a mixture of some of them in good seasons.

• A range of palatable shrubs such as flat-leaved bluebush, felty bluebush, mulga bluebush,tall saltbush, tall sida and cotton bush, depending on the area. Not all of these species growsat a single site and presence may vary considerably over short distances (less than akilometre).

• Few if any increaser shrubs such as sandbank poverty bush, turkey bush and little or nofalse wanderrie or wind grass.

• No evidence of accelerated erosion.

110

Fair long-term range condition• Blend of both palatable perennial grasses such as broad-leaved wanderrie and annualgrasses such as false wanderrie present in good seasons.

• The number of decreaser low shrubs balanced or exceeded by the number of increasersand restricted to protected areas.

• Occasional evidence of wind erosion.

C H A P T E R 6

This Goldfields site supports a mixture of wanderrie grasses including patches of woolly butt, broad-leavedwanderrie and buck wanderrie. There is a sprinkling of decreaser low shrubs such as cotton bush and mulgabluebush plus some unpalatable poverty bushes. The soil surface includes small bare sealed patches. The deadtrees probably resulted from past droughts.

111

S A N D P L A I N

Poor long-term range condition• Few if any palatable perennial grasses and shrubs are left in good seasons.

• Areas of bare ground or increasing numbers of unpalatable species such as sandbankpoverty bush, turkey bush and less commonly some cassias.

• Evidence of wind erosion.

This country north of Leonora is producing well below its potential. The perennial woolly butt tussocks areresponding to recent rain but have been grazed heavily in the past. No palatable shrubs are evident. Thesandbank poverty bushes are not palatable to stock and may be increasing in number. The dead mulgas stand asa reminder of the past droughts and fires.

112

Kalgoorlie

PERTH

Carnarvon

Meekatharra

BowgadaBowgada (pronounced bog-a-da) is thecommon name for two very similar tallspreading acacias which are the dominantforms of vegetation on extensive areas ofsandplain around Carnarvon, parts of theMurchison and the north-eastern Goldfieldssouth of Lake Barlee and Lake Raeside. Itoften occurs above breakaways on the oldplateau surface.

Until the 1980s the two shrubs wereconsidered to be the same species, butbotanists have since determined there areactually two separate species, Acacialinophylla and Acacia ramulosa which differonly in leaf shape. In cross-section, A.ramulosa leaves (the most common form)are flat while A. linophylla leaves are round.Some intergrades between the two mayoccur, but anything that is not perfectlycylindrical is considered to be A. ramulosa.In other respects however, the two speciesare very similar.

C H A P T E R 6

These shrubs may grow to 4 metres highdominating the vegetation and suppressingsmaller shrubs but providing limitedgrazing for either native fauna, sheep orcattle except from their pods. Sheep will eatthe leaves when few alternatives areavailable and pastoralists have describedsheep as wearing bowgada leaf ‘collars’.The seed pods contain over 20 per cent

A. ramulosa (x2) A. linophylla (x2)

crude protein and are sought eagerly bysheep when the pods drop after goodseasons. The shrubs themselves have noindicator value in terms of range condition.

While known as bowgada throughout mostof the shrublands the local name is wanyuin the west Gascoyne and Shark Bay areas.Wanyu covers about 25,000 squarekilometres or a third of the CarnarvonBasin and as bowgada it occupiesextensive undulating plains in otherregions. The soils are deep, sandy and non-saline, usually dark red or sometimesyellow. Infiltration of rainfall is very rapidand there is usually very little run-off.Erosion is not a problem. Typical examplesof this country would be the Kalli land

113

system of the Murchison, Sandplain landsystem in the Carnarvon Basin and Yowiein the north-eastern Goldfields.

While bowgada dominates many areas it isreplaced by sugar brother or spinifex wattleon very sandy areas of the lowerMurchison. Most other features of thecountry are similar. Pastoralists oftendescribe it as 'hungry country’.

Trees are scattered but include mulga,native pine and several species of eucalyptsin most areas except around Carnarvon.Besides the bowgada, other prominent tallshrubs can include limestone wattle, curaraand sandplain wattle (also called firewattle). Low shrubs are mainly sparse andstruggle to grow beneath the tall shrubs.

Common decreaser species include cottonbush, horse mulla mulla and silky bluebush.

Wilcox bush, which is quite palatable and anotable decreaser on granite soils is lesspalatable on bowgada country so should notbe used as an indicator.

Increaser low shrubs include povertybushes such as sandbank poverty bush andturkey bush, but shrub increase is rarely aproblem.

The country supports similar perennialgrasses to the wanderrie country, normallyin much lower numbers, although soft andbroad-leaved wanderries may be reasonablyplentiful following very wet years,particularly those with summer rains. In thelower Murchison wanderrie and bowgadacountry are very hard to separate.

Fire history is a major factor in thedistribution and size of various plants.Major fires have removed the bowgada/wanyu from some areas and it may takeforty years for it to regain dominance.Carrying capacity tends to increase afterfire as more palatable low shrubs andgrasses re-establish first when their growthis not suppressed by the larger shrubs.

Aerial photographs of the VictoriaSandplain near Shark Bay taken between1952 and 1981 show that about a quarterhad been burnt recently enough to bedetected. Most fires were thought to havebeen started by electrical storms and fuelledby unusually heavy growth of annualgrasses.

In 1963 for example, heavy summer rain(162 mm) in January-February followed byheavy winter rains (276 mm) resulted inprofuse growth of annuals. Several firesignited the following November andcontinued burning for several months. Theyremoved all small shrubs and most wanyuexcept for a few tall individuals whichsurvived by sprouting from upper branches.Other large perennials such as native poplarand fire bush then germinated followed bycotton bush, flannel bush, flat-leavedbluebush and felty bluebush under theshelter of the native poplar. These first tallcolonisers lived only four or five years,soon giving way to scattered limestonewattle, sandplain wattle and in some higherlocal areas, sandridge gidgee.

S A N D P L A I N

114

Ten to forty years after burning, sites ingood condition often show increased cottonbush, flat-leaved bluebush and flannel bush.It’s believed that it could take at least fortyyears for return of the dense wanyushrublands resulting in improved grazinguntil this time. Recent burning can berecognised by the presence of blackenedstumps, and large numbers of plants ofuniform height.

Major droughts have also causedwidespread death of bowgada or sugarbrother tall shrubs, and large areas of thelower Murchison still exhibited this in theearly 1990s following drought in the late1970s. Older shrubs appeared to succumbmore than younger plants and their deathshad a similar effect to fire, resulting invaluable regrowth of numerous perennialgrasses and palatable shrubs.

Likely range condition changesThe vegetation component of bowgada in itsnatural state is strongly influenced by fire.The tall acacia scrub is normally too densefor sufficient grass or herbage to build upfor fires. However, occasional extremedroughts will kill mature bowgada, orexceptional rainfall years, particularlysummer rainfall years, will permit sufficientmaterial to grow to allow fire to run.Summer thunderstorms with occasionallightning strikes start the fires. Fires mayoccur only once every thirty to fifty years.The last recorded fires in the Carnarvonregion were in 1964.

C H A P T E R 6

Good news signs• Sprinkling of decreaser low shrubs andoccasional grasses

• Difficult to crawl through because ofthick understorey close to ground

• Can’t see through vegetation at groundlevel

Bad news signs• Bare surfaces, little litter on ground –swept or vacuumed appearance

• Can see through vegetation belowgrazing height

• More tomato bush

Fire eliminates the bowgada allowing anabundant recruitment of cottonbush, firebush, desert poplar and fire wattle. Firebush, desert poplar and fire wattle die outwithin ten to twenty years or so and there isa slow recruitment of bowgada and returnto the natural bowgada community overthirty years or more.

Grazing has only a limited impact on thiscommunity. Excessive grazing of closedbowgada communities may eliminate thefew useful perennial shrubs such as warty-leaf eremophila and there may be someincrease in unpalatable shrubs such asturkey bush. Excessive grazing of the burntcommunity has similar effects but has littleeffect on the long-term processes.

115

This sandy slope is in fair to good condition with some Wilcox bush growing in association with low bowgada.Decreaser shrubs are sparse in number and there are some broad-leaved wanderrie tussocks evident in thephotograph. The soil surface is stable and productive and there is an abundant accumulation of litter beneath thetall shrubs. The soil is inherently infertile.

S A N D P L A I N

Good condition in unburnt areas• A narrow range of species forms a sparse understorey. Decreaser low shrubs such aswarty-leaf eremophila, flat-leaved bluebush, mulga bluebush, ruby saltbush, green cassia andtall saltbush are found scattered beneath the taller shrubs. Cotton bush and flannel bush areoccasionally present in small numbers.

• Sandbank poverty bush, tall poverty bush, pebble bush and tomato bush are occasionallypresent.

• Soil surface is usually soft and friable and often covered with plant litter providing nichesfor germinating seedlings and improved water infiltration.

Fair condition in unburnt areas• The range of species remains fairly constant but fewer decreasers are present.

• Density of unpalatables such as sandbank poverty bush, pebble bush and tomato bushmay increase marginally.

• Erosion is rare.

116

Poor condition in unburnt areas• Very reduced range of species and few if any decreasers left.

• Surviving decreasers often show evidence of heavy grazing. Cotton bush and flannel bushare less common while sandbank poverty bush, pebble bush and tomato bush may continue toincrease but are not usually a problem.

• Swept or vacuumed appearance to ground.

• Erosion is rare.

C H A P T E R 6

117

Meekatharra

Kalgoorlie

PERTH

Carnarvon

Currant Bush Mixed ShrubCurrant bush mixed shrub is unique to thewest Gascoyne area where it occupies morethan 4,000 square kilometres of the lesssandy soils. It often alternates with patchesof bowgada/wanyu; the currant bush mixedshrub occupying the lower plains of thelandscape on duplex soils and the wanyu onthe higher banks, dunes and sandier areas. Athin surface crust may be present. Mosaicpatterns showing the differing types ofvegetation can be seen clearly from the air.It occurs in Sandal, Spot and Target landsystems.

The distinctive plant species is currant bush,so-called for its small black edible berrieswhich grow singly on short stems along thebranches. The berries are usually foundbetween May and November in goodseasons. The white or cream flowers have adistinctive fan shape and a very sweet smell.Aborigines used the roots to make aninfusion for stomach pains and it issometimes used as a remedy for cancer.

While distributed across most of the aridshrublands, including the Goldfields, theMurchison and the Gascoyne, currant bushnormally grows sparsely except on thesesandy plains where it may occur in densepatches.

The shrub grows 3 metres high infavourable, non-saline conditions. It is animportant forage plant and the leaves, whichare dropped in dry seasons, contain up to 13per cent protein and are relished by stock.

Currant bush may also occur in south-westareas in a prominently spiny form whichappears to be highly resistant to grazingand will persist long after palatable specieshave been removed.

While currant bush is the most distinctiveof the palatable species and is locallydominant within stands in good condition,the general vegetation comprises a richmixture of both low and tall shrub species.Major tall shrubs include curara, pricklyacacia (bardi bush), needlebush, mingahbush and pebble bush. Numbers around 3to 4 per centihec are frequent.

S A N D P L A I N

118

The most common low trees aresnakewood, mingah bush and sandalwood.(At one stage sandalwood was WesternAustralia’s most valuable export. Thedistinctive smell is most apparent in the drywood including the roots, but the leaveshave no smell.)

In good condition country, every snakewoodshould have a high litter accumulation andsmaller shrubs such as ruby saltbush, flat-leaved bluebush, tall saltbush and feltybluebush growing beneath it.

Low shrub densities vary much morewidely than tall shrubs and may reach 200per centihec, although 30 to 40 would bemuch more common. Up to fifty differentlow shrub species have been counted insome areas. Because of the wide range anddensity of palatable shrubs, the country hashigh pastoral value and resists drought.

Widely distributed decreaser low shrubsinclude scrambling saltbush, ruby saltbush,flat-leaved bluebush, felty bluebush, cottonbush, Gascoyne mulla mulla, tall saltbushand flannel bush.

The most useful indicator plant is currantbush itself. In good seasons and condition,currant bush is a very luminous dark green,but as moisture is lost the leaves darken,then yellow and finally drop off. Bushesmay appear to die but will recover afterrain.

Ruby saltbush and felty bluebush are alsoimportant indicators but can be relativelyshort-lived and dependent on season. Other

useful indicators could be green cassia,ragged-leaf fan flower, narrow-leavedmulla mulla and warty-leaf eremophila.

Cotton bush is very plentiful on some sitesbut on its own is a poor indicator ofcondition. Increasing cotton bush numberscan be expected when long-term grazingpressure falls, but large numbers of plantsmay die in poor seasons.

The proportion of palatable to unpalatablespecies is a useful guide to range condition.Increasers include needlebush, tomatobush, prickly acacia, silver poverty bush,waxy-leaf poverty bush and straight-leavedcassia.The country is very prone to invasion bywoody increasers which make it difficult towalk through. Where invasion occurs,often near heavily-used watering points,there is no practical solution other thanexpensive mechanical removal. Fires arepossible but only after a run of exceptionalseasons – perhaps only once in thirty tofifty years.

Needlebush invasion is one of the mostinsidious. Low numbers can germinatealmost every year, with higher numbers insome years. Growth rates are very slowand mortality is low.

Burning trials were conducted south-eastof Carnarvon in 1985 where fire was foundto be useful in killing needlebush, but oflittle use against other increaser species.Waxy-leaf poverty bush, for example,survived even the most intense fires by

C H A P T E R 6

119

S A N D P L A I N

resprouting from the base. Palatable speciessuch as felty bluebush and ruby saltbushwere destroyed so that fire gave littleadvantage except to reduce the needlebush.

Perennial grasses are scarce in this country,but may include buffel grass (in northernareas), curly windmill grass and spinifex.Wind grass is weakly perennial in goodseasons and where grazing pressure is notgreat. Pastoralists have observed that sheepprefer it to mature buffel grass, but if eatendown to the crown it is unlikely to recover.Button grass is plentiful in good seasons.

Likely range condition changesCurrant bush mixed shrub occupies the landsystems flanking the erodible riverfloodplains in the Carnarvon area. The soilsare mostly stable.

In the natural state these shrublands supportan unusually diverse range of low shrubs,many of which are palatable, withoccasional taller shrubs includingneedlebush and snakewood. Fire is rare.

Grazing has a major impact and excessivegrazing, particularly in drier years,eliminates the less hardy species includingcotton bush, bluebushes and the youngercurrant bush and tall saltbush. Seed ofspecies such as cassias remains viable in thesoil and these species rapidly colonise thespace left after elimination of more

palatable shrubs. Needlebush seed is heldin aerial pods and conditions for its releaseand subsequent successful germination andestablishment, occur infrequently.However with the correct combination ofcircumstances, needlebush has explosiverecruitment potential and seedling stormsmay occur. There have been at least twomajor seedling storms within the past fortyto fifty years (including one in the mid-60s)leading to a degraded communitydominated by needlebush with otherunpalatable invaders including cassias andpoverty bushes.

This change in species producesneedlebush thickets which further reducethe opportunities for growth of annualspecies and hence fire. There are no knownexamples of fire-affected needlebushcommunities however it is known thatneedlebush is readily killed by fire.Pastoral management has therefore littleimpact on needlebush-invaded mixedcurrant bush shrubland. Changes for thiscommunity over perhaps a fifty to hundredyear time-frame rely on fire, butopportunities are exceedingly rare. Shorterlived species such as cassias may die outbut it may take more than a century forneedlebush to die and for other species toemerge.

120

Good news signs• Plenty of young plants especiallypalatables such as currant bush

• Wide variety of species present

• Currant bush plants carrying leaf up tograzing height except in very bad years

• Accumulation of plant litter andpalatable small shrubs beneath large shrubs

• Snakewood foliage close to ground level

• Curly windmill grass common

• Few young woody weeds

Bad news signs• Currant bush present only as few, oldindividuals with no leaves below grazingheight

• Increasing numbers of flannel bush andtomato bush, but not of more desirablespecies

• Numerous young and middle-sizedwoody weeds such as needlebush, pricklyacacia and waxy-leaf poverty bushes

• Palatable species present only as woodyindividuals

• Little or no curly windmill grass

• Wind erosion removing litter frombeneath shrubs

• Bare surface and sealed soils

• Sand piled up around some shrubs

C H A P T E R 6

121

This fair to good site shows a wide range of different aged currant bushes growing on level plains in theCarnarvon district. Other decreaser shrubs including warty-leaf eremophila, tall cassia and cotton bush arepresent, while numerous annual grasses and herbs grow in season. The scattered taller shrubs includesnakewood, needlebush and curara.

Good condition• Country supports numerous palatable shrub species but distribution is irregular.

• May be high densities (more than 5 per centihec) of currant bush and sometimessnakewood.

• Total shrub densities vary widely but are often from 30 to 50 per centihec.

• Increaser species such as tomato bush are uncommon.

• No erosion is present.

S A N D P L A I N

122

This currant bush mixed shrubland in the Carnarvon area carries about 4 decreaser shrubs per centihec,comprising currant bush, warty-leaf eremophila, scrambling saltbush and cotton bush. The soil surface is mostlystable. There has not been a proliferation of woody shrubs such as prickly acacia, cassias and eramophilas,although they are present in small numbers. Overall condition would be rated as fair.

Fair condition• Partial but obvious loss of species. The most palatable shrubs such as currant bush, tallcassia and warty-leaf eremophila may be present only as large, old individuals.

• Numbers of flannel bush, waxy-leaf poverty bush, needlebush, pebble bush and wait-a-while may increase.

• Most conspicuous shrubs are 2 to 3 metres tall rather than younger plants.

• Overall shrub numbers are reduced with increasing areas of bare ground.

• There is normally no erosion.

C H A P T E R 6

123

S A N D P L A I N

This currant bush mixed shrubland shows a proliferation of unpalatable waxy-leaf poverty bushes. A fewdecreaser shrubs are still present but overall condition is poor.

Poor condition• Palatable species are often absent, dead or exist only as occasional heavily browsedrelics.

• Species diversity is low and vegetation is dominated by unpalatables such as pricklyacacia, needlebush, waxy-leaf poverty bush, straight-leaved cassia or silver poverty bush.

• Erosion is uncommon but may occur as wind-blown soil around shrub bases or moreprominent pedestalling and surface soil loss and scalding between shrubs.

124

ost of the arid shrublands areleased to pastoralists for grazinguse, although some of the less

accessible and less productive grazing areasremain as vacant Crown Land, and specificareas have been excised as national parks,nature reserves or Aboriginal reserves.

Altogether, about three hundred and thirtyseparate pastoral leases occupy this countryranging in size from forty four squarekilometres on the fringes of the agriculturalareas, to nearly five thousand squarekilometres on the Nullarbor. Average leasesize is 172,000 hectares or 1,720 squarekilometres.

Administration of the land is through thePastoral Board which is part of theDepartment of Land Administration(DOLA) and responsible to the Minister forLands. The board consists of five members:two pastoralists, one representative eachfrom DOLA and the Department ofAgriculture (DAWA) and an independentchairman.

Current pastoral leases will all expire in2015 and until then lessees are required topay annual rent and comply with variousstatutes and conditions. In general, theseconditions have been set to ensure that theland is managed and worked according toaccepted standards and that its use isdirected towards the conservation andregeneration of vegetation. The Pastoral

Chapter 7 - How the land is managedBoard previously maintained its own fieldstaff of pastoral inspectors but these weretransferred to DAWA in 1987.

Pastoral Lease Reports are compiled forevery pastoral property on a five-yearlyschedule. Range Condition Reports arealso prepared when an application for leasesale is received and these are madeavailable to intending purchasers. Theycontain recommendations on managementto address specific land degradationproblems. These two reports coverinformation on stocking history and currentstock numbers, seasonal conditions and theeffectiveness of fences and waters inmanagement.

Concerns about land degradation throughloss of useful species or increased soilerosion are referred to the Commissionerfor Soil and Land Conservation for actionunder the Soil and Land Conservation Act.The Commissioner may issue a noticerequesting action such as destocking,fencing and development of a managementplan for the lease where it is considerednecessary.

Grazing pressureRangeland on most pastoral leases orstations supports natural vegetation only,where sheep graze at stocking rates rangingfrom one sheep to 5 or 6 hectares on goodsaltbush or bluebush country to one sheepon 30 or 40 hectares on poor condition

125

C H A P T E R 7

animals, but with rapid natural populationincrease it was believed that 750,000 goatswere still present in June 1993. The goatreduction program allowed the balance toswing back so that sheep exerted 51 percent of the total grazing pressure, but it isclear that some areas are supporting farmore animals than many people believe.

Wild dogs are mainly present in the drieroutlying areas and half a million baits havebeen dropped annually in the last fewyears, mainly as a preventive measure.

In the Murchison more than 14,000 freshmeat baits were laid on the ground againstfoxes in 1992-93. But numbers recoverquickly, usually through reinvasion fromuncontrolled areas and it is expected thatlethal baiting will need to be repeatedconsistently until some form of biologicalcontrol becomes available.

Emu population numbers build up in goodseasons and when food in the pastoralareas is insufficient, the emus tend tomigrate south in vast numbers. The StateBarrier Fence is maintained to prevent suchmigrations and stretches from the ZuytdorpCliffs north of Kalbarri to the JohnstonLakes in the Dundas Shire.

Kangaroo populations are alsoconsiderable and while pastoralists mayremove sheep to encourage regeneration ofvegetation, they often reckon without thekangaroos, which tend to be attracted tounstocked paddocks. In a ten-year trial atBoolathana Station near Carnarvon

stony hardpan plains. Cattle are also run insome areas and some properties havechanged from cattle to sheep and backagain with fluctuating profitability.

Most paddocks are stocked year-in year-out, but other country is spelled in eithersummer or winter to assist in recovery ofvegetation. Wethers are usually run onpoorer country, while more fertile areassuch as good lake country are reserved forewes and lambs which require higher levelsof nutrition. Water points - troughs adjacentto windmills or earth dams - are providedabout every 4,000 hectares of country andaverage paddock size is about 7,000hectares.

Besides the introduced stock, rangelandsare also home to a variety of native andferal animals including kangaroos, euros,donkeys, wild horses, goats, foxes, rabbitsand wild dogs. Pastoralists are required tocontribute to a ‘vermin rate’ which is usedto help finance control and eradicationprograms for problem plants and animals.Such programs are administered throughthe Agriculture Protection Board of WA(the APB).

It was estimated in 1990 that a milliongoats were present in the arid shrublandscontributing 12 per cent of the total grazingpressure on the vegetation. Kangaroos werethen exerting half of the total grazingpressure, while sheep provided theremaining 38 per cent. During 1991-92 and1992-93 major feral goat control programssuccessfully removed more than 900,000

126

might have been a very good reason forleaving it open such as allowing stockaccess to water.

Main highways are often fenced off fromthe station country beyond, but other roadsare frequently unfenced. Station countryshould be regarded as private property, withthe same laws of trespass that apply in thefarming areas. Travellers wishing to enter alease beyond the immediate road reserve(which can be up to 200 metres wide formain roads), should obtain permission fromthe occupier.

Absence of fencing means that livestock orwildlife can often be found crossing theroads or lying on them, so always watch forthe unexpected, particularly at night. Theanimal seen on the side of the road may notnecessarily be the danger. Beware of itsunseen friends and relations who may wantto join up from the other side. Collisionsbetween vehicles and kangaroos, emus,donkeys or sheep are never pleasant foreither party.

Wet weather can bring additional hazardsfor those travelling through the shrublands.After a light shower of rain on bitumen,kangaroos often come onto the road to drinksurface water. When wet, unsealed roadscan suffer considerable damage fromvehicles and take months to repair. Alwayscheck with the local shire or the occupierbefore driving on unsealed roads after rain.

Some stations now offer accommodation totravellers and tourists, ranging from

C H A P T E R 7

weighing of dung in different paddocksshowed clearly that the marsupialspreferred grazing in the unstocked andlightly stocked paddocks. Removing sheepfrom an area did not remove all the grazingpressure on its plants.

Numbers of kangaroos multiply followingthe provision of additional stock watersand when stations are destocked it isessential that the waters too are closeddown. The Department of Conservationand Land Management (CALM) has theresponsibility for managing kangaroopopulations in Western Australia. Amanagement program provides forconservation and the controlled harvestingof particular species.

The main problem weeds in the shrublandsare saffron thistle, mesquite andhorehound. Where they become a majorproblem, pastoralists are contracted to helpremove them.

Driving through stationsBecause stock numbers are low, travellerson the public roads traversing the stationsmight rarely see any sheep or cattle andmight assume none was present. Wherefences cross roads, grids usually allowunimpeded travel while preventing stockmovement. Gates are sometimes usedrather than grids and it is essential that theyare left as they are found. A shut gateshould be left shut after passing, but if it isopen, motorists should not try and behelpful by shutting it behind them. There

127

bedrooms with private facilities within thehomestead to self-contained cottages,shearers quarters and caravan parks. Guestsmay be offered the opportunity to becometemporary station hands, while bushwalking, bird watching, picnics andbarbecues are other recommendedactivities.

The main tourist season is in the coolermonths from May to October and details ofaccommodation can be obtained from localand city tourist offices, motoringorganisations and accommodation guides.

Moving off the road verge and campingovernight is also possible, but permissionshould always be sought from the nearesthomestead. Many environments are verydelicate and vehicle tracks across them maycause damage possibly leading to erosion.Accidental spread of noxious plants fromother areas is another concern, particularlyaround creek beds and other attractivecamping sites.

Several basic rules of common courtesy(and law) should be remembered:

• Littering is an offence under law in thestation country, just like elsewhere. Plasticcontainers and tin cans can be fatal tolivestock or native animals if chewed orswallowed. A campsite may be manykilometres from the nearest town butshould always be left as it was found. Allrubbish should be removed, not just buriedwhere it might be uncovered by curiousanimals.

H O W T H E L A N D I S M A N A G E D

• Troughs and bores are provided forstock drinking water, not for travellers.Never camp close to watering places as thiscould prevent stock coming in to drink.

• Fire prevention is essential and visitorsshould consult the local authority and abideby any fire bans in force. A fire should becovered completely with earth andextinguished before going to sleep orleaving camp.

• Dogs should not be taken onto pastoralproperties without permission. Travellers’dogs can also be in danger from poisonbaits which are sometimes laid to destroywild dogs and foxes.

• If going near a homestead, proceedwith care as small children and family petsmay be about.

• If in doubt about directions, consult thepastoralist. (Station boundaries are shownon the Western Australian Travellers Atlas.)

Under the Wildlife Conservation Actpicking of flora is prohibited except by theowners or occupiers of land, or with theirconsent. Being leasehold rather thanfreehold property, pastoral country isregarded as Crown Land but theleaseholders (station owners or managers)have grazing rights to native vegetationwhich includes the right to pickwildflowers as well as let their stock eatthem. (Station owners also have rights totake timber for buildings, stockyards,fences and domestic firewood, but not toharvest timber commercially.)

128

But the Crown (or State of WesternAustralia) allows other people only to takeflora if they have a licence – either aCommercial Purposes Licence or Licencefor Scientific or Other Prescribed Purposes.The second licence, which does not permitcommercial sale, is mainly used forbotanical, medical or other scientificresearch.

Licences can be obtained fromConservation and Land Management(CALM) offices in Perth or major centresincluding Geraldton, Carnarvon, Kalgoorlieand Karratha. Cost is currently $10 and thelicence can extend for up to a year. CALMencourages any traveller with a special

interest in wildflowers who may wish topick and photograph specimens to obtainsuch a licence. CALM also has a list ofrare and endangered flora which can onlybe taken with the specific written approvalof the Minister.

Mining activityAlthough leased to individual pastoralistsunder certain conditions, the stationcountry remains the property of the Crownand is therefore available for other usesincluding exploration for minerals. TheMining Act is the principal piece oflegislation which regulates this industryand over-rides many other Acts.

Natural water is scarce in much of the rangeland but pastoralists provide troughs for stock such as this onesouth of Wiluna which is supplied by a windmill. Checking on the windmills is an essential job on the stations,particularly in summer.

C H A P T E R 7

129

Relations between miners and pastoralistsare sometimes strained. On one hand,mining operations can severely disruptnormal pastoral activities, but on the otherthey have frequently become a veryimportant source of secondary income forpastoralists who have been able tosupplement their on-station earnings in leantimes by offering machinery and labour forroad grading, bulldozing and other work.

A code of conduct for mineral explorationon pastoral leases has been established andmineral explorers are required to avoidunnecessary damage to pastoralimprovements and natural vegetation. Theyare not allowed to take water from

pastoralists’ bores, dams, troughs or otherimprovements without agreement. In manyplaces mining companies have purchasedthe pastoral leases on which valuableminerals have been discovered, and runstock commercially as well as extractingthe minerals. In other cases they have beengranted permission to destock theproperties and have closed off the waters.

After exploration or mining is complete,sites have to be rehabilitated to a stable,non-erodible and safe condition.Compensation or restoration for loss ordamage caused by miners is required. TheDepartment of Minerals and Energy cansupply full details of these requirements.

H O W T H E L A N D I S M A N A G E D

130

Glossary of technical termsAcacias: Large group of yellow-flowered shrubs and trees, also known as wattles.Accelerated erosion: The more rapid erosion that follows the destruction or loss ofprotective cover, often resulting from man’s activities on the soil, vegetation and landform.This contrasts with geological erosion which may take thousands of years.Annual: Plant that completes its life cycle within a single year.Biennial: Plant that requires more than one season in which to complete its life cycle, but isunlikely to survive more than two or three years, depending on the seasonal conditions.Bindiis: Prickly biennial or annual low herbs, Sclerolaena species.Breakaway: Short scarp or cliff caused by erosion of ancient land surfaces. Breakaways arescattered throughout the arid shrubland.Bush mound: Mound of soil built up gradually around a shrub or several shrubs. A mound isable to trap water, nutrients and litter much more readily than the soil between mounds.Chenopod: Low shrub, member of the Chenopodiaceae family such as saltbush, bluebushand samphires, common to vast areas of arid shrubland and often growing in saline soils.Foliage is usually grey-green and palatable to stock although high in salts.Common: Area of common ground around a town. These may extend for several kilometresin some directions and have often been heavily grazed in the past. Conversely, some are nolonger grazed and have recovered to very good range condition.Copper burrs: Group of annual plants of Sclerolaena species. Alternative name for bindiis.Crusting: Sealing of soil surface to form a protective layer against erosion which mayreduce water infiltration rates. These crusts are readily broken by vehicles or stock tracks.Cryptogams: Small growth of primitive plant life such as lichens, algae and liverwortsfound on surface of some soils. May not be obvious when ground is dry, but easier to seewhen wet. Colour ranges through yellow, orange and green to black.Dongas: Large shallow drainage areas unique to the Nullarbor Plain.Duplex soil: Also known as texture contrast soil, where a sandy surface layer changesabruptly to a more clayey layer beneath. Such soils are common on the flood plains nearrivers, near lake frontages, on saline slopes. They are vulnerable to erosion when the sandysurface is disturbed.Eucalypts: Large group of trees of Eucalyptus species, including gums and mallees. Manyare found in the Goldfields, but they tend to be rare in other arid rangelands except nearpermanent water.

131

Everlasting daisies: Various species of annual pink, white and yellow daisy common tolarge areas of WA.Exclosure: Area fenced to restrict access of grazing animals, used by scientists to assesschanges in vegetation and soil condition. Such areas allow separation of climatic and grazingeffects.Floodplain: Area close to river which becomes flooded after heavy rains. Such areas areusually relatively fertile due to the deposition of sediments.Forbs: Small non-woody annual plants or forage herbs.Frankenias: Group of fairly tough but palatable, saline, perennial low shrubs of Frankeniaspecies.Greenstone: Distinctive dark coloured rock associated with uplands and mineral deposits inthe Goldfields. The term is also used to describe the relatively fertile soils formed from theserocks.Grove: Dense group of trees or shrubs of varying size which tends to become the fertilepatch for a given area. Groves are a distinct feature of some country types.Gully: A channel more than 30 centimetres deep with short, usually steep walls eroded on aslope by stream flow.Hardpan: Hard layers cemented by iron and silica just beneath the soil surface which canprevent penetration of plant roots. Local names include ‘coffee rock’ and ‘Murchisoncement’. The hardpan layer may be exposed by erosion in some places.Hummock/Hummocking: Accumulation of sand formed around plants or other objects as aresult of wind deposition caused by erosion elsewhere.Land system: An area or group of areas throughout which there is a recurring pattern oftopography, soils and vegetation. This method of land classification is used by the WesternAustralian Rangeland Survey and some land systems are common to several regions. It is aconvenient mapping unit, readily seen on aerial and satellite photographs.Mallee: Multi-stemmed varieties of Eucalyptus species.Natural erosion: Natural processes involving the movement of land surface material in allnatural environments.Pedestal: Vertical pillar of soil, usually associated with plant or root protection that remainsafter erosion has removed surrounding soil material.Perennial: Plant having a life cycle lasting more than two years. Perennials found in therangeland include small shrubs and grasses which live only a few years to trees and tallshrubs which may survive for hundreds of years.

132

Poverty bushes: Some members of Eremophila genus, mostly unpalatable shrubs. Allpoverty bushes are eremophilas but not all eremophilas are poverty bushes.Rill: A small channel up to 30 centimetres deep. The term is often used in relation to erosion.Saline: High in salt, a term used commonly to describe both water and soil. Saline soils arewidespread through the rangeland and support particular types of vegetation such assaltbushes and bluebushes.Samphires: Group of low growing, salt tolerant shrubs, mostly species of Halosarcia orGunniopsis.Scald: Ground that is bare of vegetation, and from which soil has been eroded by surfacewash or wind. Their sealed surfaces are usually impervious to water.Shrub: Woody plant multistemmed at the base (or within 20 centimetres of ground level) or,if single stemmed, less than 2 metres tall. Shrubs have been separated into low shrubs (lessthan 1 metre tall), medium shrubs (1 to 2 metres) and tall shrubs (more than 2 metres).Sidas: Group of plants within the Sida genus, mostly palatable perennial shrubs but includingsome annuals and biennials.Soil fertility: The ability to supply nutrients for plant growth when other factors arefavourable. Most rangeland soils in WA are not fertile except for greenstones and alluvialplains.Spinifex: Group of perennial hummock grasses, mainly Triodia and Pletrachne species.Strew: Often used to describe small rocks or pebbles ‘strewn’ over the surface of the ground.Occurs frequently on stony hardpan soils, greenstone and other country high in thelandscape.Terracettes: Shallow erosion faces on slopes resulting either from soil creep or sheet watererosion.Topography: Description of the relief features or surface configuration of an area such ashills, plains, outcrops of rock.Tree: Woody plant more than 2 metres tall with a single stem or branches well above thebase.Wanderrie grasses: Common name for group of perennial grasses found widely distributedin sandy soils of the arid shrublands.Wattle: Common name for members of Acacia family, mostly shrubs or trees.Woody weeds: Common term for unpalatable shrubs which invade degraded land. Examplesinclude needlebush, turpentine bush and some cassias.

133

buck wanderrie Eriachne helmsii

buffel grass Cenchrus ciliaris

bullock bush Alectryon oleifolius

button grass Dactyloctenium radulans

cannon balls Dissocarpus paradoxus

cassia, banana-leaf Cassia phyllodinea

cassia, creeping Cassia hamersleyensis

cassia, crinkled Cassia helmsii

cassia, green Cassia chatelaineana

cassia, grey Cassia helmsii

cassia, straight-leaved Cassia desolata

cassia, tall Cassia chatelaineana

cassia, variable Cassia sturtii

climbing saltbush Rhagodia eremea

common wallaby grass Danthonia caespitosa

coolabah Eucalyptus coolabah

corky-bark kallstroemia Tribulus platypterus

cotton bush Ptilotus obovatus

creeping cassia Cassia hamersleyensis

creeping wanderrie Eragrostis lanipes

crinkled cassia Cassia helmsii

curara Acacia tetragonophylla

curly windmill grass Enteropogon acicularis

currant bush Scaevola spinescens

desert cassia Cassia nemophila

desert kurrajong Brachychiton gregorii

desert poplar Codoncarpus cotinifolius

desert willow Pittosporumphylliraeoides

doublegee Emex australis

earlobe saltbush Chenopodiumgaudichaudianum

false wanderrie grass Eriachne aristidea

Common names of plants in this manualball-leaf bluebush Maireana glomerifolia

banana-leaf cassia Cassia phyllodinea

bardi bush Acacia victoriae

beefwood Grevillea striata

berry saltbush Rhagodia baccata

billy buttons Helipterumcraspedioides

bindii, limestone Sclerolaenaobliquicuspis

Birdwood grass Cenchrus setiger

black oak Casuarina cristata

blackbutt, Goldfields Eucalyptus lesouefii

bladder saltbush Atriplex vesicaria

bluebush, ball-leaf Maireana glomerifolia

bluebush, false Cratystylis conocephala

bluebush, five pin Maireana atkinsiana

bluebush, flat-leaved Maireana planifolia

bluebush, Gascoyne Maireana polypterygia

bluebush, golden Maireana georgei

bluebush, lax Maireana thesioides

bluebush, mulga Maireana convexa

bluebush, pearl Maireana sedifolia

bluebush, pussy Maireana melanocoma

bluebush, shy Maireana platycarpa

bluebush, silky Maireana villosa

bluebush, spiny Maireana aphylla

bluebush, three-winged Maireana triptera

bowgada Acacia ramulosa orA. linophylla

breelya Gastrolobium laytonii

broad-leaved wanderrie Monachather paradoxa

bronze bluebush Maireana atkinsiana

broom bush Eremophila scoparia

134

feather spear grass Stipa elegantissima

felty bluebush Maireana tomentosa

felty fuchsia bush Eremophila compacta

fire bush Gyrostemnon ramulosis

fire wattle Acacia murrayana

five pin bluebush Maireana atkinsiana

flannel bush Solanum lasiophyllum

flat-leaved bluebush Maireana planifolia

Gascoyne bluebush Maireana polypterygia

Gascoyne mulla mulla Ptilotus polakii

George’s bluebush Maireana georgei

gidgee Acacia pruinocarpa

gimlet Eucalyptus salubris

golden bluebush Maireana georgei

Goldfields blackbutt Eucalyptus lesouefii

granite poverty bush Eremophila platycalyx

granite wattle Acacia kempeana

green cassia Cassia chatelaineana

grevillea, red Grevillea deflexa

grey cassia Cassia helmsii

grey fan-leaf Lawrencia squamata

grey turpentine bush Eremophilamacmillaniana

hop bush Dodonea lobulata

hop mulga Acacia craspedocarpa

horse mulla mulla Ptilotus schwartzii

kerosene grass Aristida contorta

kite-leaf poison Gastrolobium laytonii

kopi poverty bush Eremophila miniata

kurrajong Brachychiton gregorii

lake fuchsia bush Eremophila miniata

large white paper daisy Helipterum floribundum

lax bluebush Maireana thesioides

lemon-scented grass Cymbopogon ambiguus

limestone bindii Sclerolaenapatenticuspis

limestone wattle Acacia sclerosperma

love grass Eragrostis dielsii

low mulla mulla Ptilotus beardii

marble gum Eucalyptusgongylocarpa

mingah bush Alectryon oleifolius

miniritchie Acacia grasbyi

mulga, hop Acacia craspedocarpa

mulga Acacia aneura

mulga bluebush Maireana convexa

mulga broombush Spartothamnellateucriiflora

mulla mulla, horse Ptilotus schwartzii

mulla mulla, Gascoyne Ptilotus polakii

mulla mulla, purple Ptilotus exaltatus

mulla mulla, Ptilotus rotundifoliaroyal or showy

Murchison red grass Eragrostis dielsii

Murchison willow Acacia demissa(formerly aff.quadrimarginea)

myall Acacia papyrocarpa

native pine Callitris columnellaris

native poplar Codoncarpuscotinifolius

needlebush Hakea preissii

neverfail Eragrostis setifolia

old man saltbush Atriplex nummularia

onion weed Asphodelus fistulosis

pearl bluebush Maireana sedifolia

pebble bush Stylobasium spathulatum

pink velleia Velleia rosea

pixie bush Eremophila oldfieldii

poverty bush, royal Eremophila cuneifolia

poverty bush, silver Eremophila pterocarpa

135

poverty bush, Eremophila spathulataspoon-leaved

poverty bush, warty-leaf Eremophila latrobei

poverty bush, waxy-leaf Eremophila crenulata

prickly acacia Acacia victoriae

purple mulla mulla Ptilotus exaltatus

pussy bluebush Maireana melanocoma

ragged-leaf fan flower Scaevola tomentosa

red grass Eragrostis dielsii

red grevillea Grevillea deflexa

rhagodia Rhagodia eremaea

ribbon gum Eucalyptus gongylocarpa

river saltbush Atriplex amnicola

Roebourne Plains grass Eragrostis xerophila

royal mulla mulla Ptilotus rotundifolia

royal poverty bush Eremophila cuneifolia

ruby saltbush Enchylaena tomentosa

sage Cratystylis subspinescens

sago bush Maireana pyramidata

salmon gum Eucalyptussalmonophloia

saltbush, berry Rhagodia baccata

saltbush, bladder Atriplex vesicaria

saltbush, silver Atriplex bunburyana

saltbush, old man Atriplex nummularia

saltbush, river or swamp Atriplex amnicola

saltbush, tall Rhagodia eremaea

sandalwood Santalum spicatum

sandbank poverty bush Eremophila margarethae

sandplain wattle Acacia murrayana

sandridge gidgee Acacia anastema

scrambling saltbush Chenopodiumgaudichaudianum

shy bluebush Maireana platycarpa

sida, tall Sida calyxhymenia

sida, dwarf or prostrate Sida corrugata

silky bluebush Maireana villosa

silver poverty bush Eremophila pterocarpa

silver saltbush Atriplex bunburyana

silver spear grass Stipa elegantissima

snakewood Acacia xiphophylla

soft spinifex Triodia pungens

soft wanderrie grass Thyridolepis multiculmis

spear grass Stipa scabra

spinifex wattle Acacia coolgardiensis

spiny bluebush Maireana aphylla

spoon-leaved eremophila Eremophila spathulata

standback Hakea preissii

straight-leaved cassia Cassia desolata

sugar brother Acacia coolgardiensis

sugarwood Myoporum platycarpum

swamp saltbush Atriplex amnicola

tall cassia Cassia chatelaineana

tall saltbush Rhagodia eremaea

tall sida Sida calyxhymenia

tan wattle Acacia hemiteles

three-winged bluebush Maireana triptera

tomato bush Solanum orbiculatum

tree balsam Euphorbia drummondii

turkey bush Eremophila gilesii

turpentine bush Eremophila fraseri

variable cassia Cassia sturtii

wait-a-while Acacia cuspidifolia

wanderrie, soft Thyridolepis multiculmis

wanderrie, buck Eriachne helmsii

wanderrie, broad-leaved Monachather paradoxa

wanderrie, wire Eragrostis eriopoda

wanderrie, creeping Eragrostis lanipes

wanderrie, false Eriachne aristidea

136

wanyu Acacia ramulosa orA. linophylla

Ward’s weed Carrichterea annua

warty fuchsia bush Eremophila latrobei

warty-leaf eremophila Eremophila latrobei

wattle, granite Acacia kempeana

wattle, limestone Acacia sclerosperma

wattle, sandplain Acacia murrayana

wattle, tan Acacia hemiteles

waxy-leaf poverty bush Eremophila crenulata

western myall Acacia papyrocarpa

white sunray Helipterum floribundum

white top Danthonia caespitosa

Wilcox bush Eremophila forrestii

wild hops Rumex vesicaria

wild tomato Solanum orbiculatum

wind grass Aristida contorta

wire wanderrie Eragrostis eriopoda

witchetty bush Acacia kempeana

woolly butt Eragrostis eriopoda

York gum Eucalyptus loxophleba

137

Acacia anastema sandridge gidgee

Acacia aneura mulga

Acacia coolgardiensis sugar brother,spinifex wattle

Acacia craspedocarpa hop mulga

Acacia cuspidifolia wait-a-while

Acacia demissa Murchison willow

Acacia grasbyi miniritchie

Acacia hemiteles tan wattle

Acacia kempeana granite wattle,witchetty bush

Acacia linophylla bowgada, wanyu

Acacia murrayana fire wattle,sandplain wattle

Acacia papyrocarpa myall, western myall

Acacia pruinocarpa gidgee

Acacia ramulosa bowgada, wanyu

Acacia sclerosperma limestone wattle

Acacia tetragonophylla curara

Acacia victoriae bardi bush, prickly acacia

Acacia xiphophylla snakewood

Alectryon oleifolius mingah bush,bullock bush

Aristida contorta wind grass,kerosene grass

Asphodelus fistulosis onion weed

Atriplex amnicola river or swamp saltbush

Atriplex bunburyana silver saltbush

Atriplex nummularia old man saltbush

Atriplex vesicaria bladder saltbush

Brachychiton gregorii desert kurrajong

Callitris columnellaris native pine

Carrichterea annua Ward’s weed

Cassia chatelaineana green cassia, tall cassia

Cassia desolata straight-leaved cassia

Cassia hamersleyensis creeping cassia

Cassia helmsii crinkled cassia

Cassia nemophila desert cassia

Cassia phyllodinea banana-leaf cassia

Cassia sturtii variable cassia

Casuarina cristata black oak

Cenchrus ciliaris buffel grass

Cenchrus setiger Birdwood grass

Chenopodium earlobe saltbush,gaudichaudianum scrambling saltbush

Codoncarpus cotinifolius native poplar,desert poplar

Cratystylis conocephala false bluebush

Cratystylis subspinescens sage

Cymbopogon ambiguus lemon-scented grass

Dactyloctenium radulans button grass

Danthonia caespitosa common wallaby grass,white top

Dissocarpus paradoxus cannon balls

Dodonea lobulata hop bush

Emex australis doublegee

Enchylaena tomentosa ruby saltbush

Eragrostis dielsii love grass, Murchisonred grass

Eragrostis eriopoda woolly butt,wire wanderrie

Eragrostis lanipes creeping wanderrie

Eragrostis setifolia neverfail

Eragrostis xerophila Roebourne Plains grass

Eremophila compacta felty fuchsia bush

Eremophila crenulata waxy-leaf poverty bush

Botanical names of plants in this manual

138

Eremophila cuneifolia royal poverty bush

Eremophila forrestii Wilcox bush

Eremophila fraseri turpentine bush

Eremophila gilesii turkey bush

Eremophila latrobei warty fuchsia bush,warty-leaf eremophila

Eremophila grey turpentine bushmacmillaniana

Eremophila margarethae sandbank, sandplainpoverty bush

Eremophila miniata kopi poverty bush,lake fuchsia bush

Eremophila oldfieldii pixie bush

Eremophila platycalyx granite poverty bush

Eremophila pterocarpa silver poverty bush

Eremophila scoparia broom bush

Eremophila spathulata spoon-leaved eremophila

Eriachne aristidea false wanderrie grass

Eriachne helmsii buck wanderrie

Eucalyptus coolabah coolabah

Eucalyptus lesouefii Goldfields blackbutt

Eucalyptus loxophleba York gum

Eucalyptus salmonophloia salmon gum

Eucalyptus salubris gimlet

Euphorbia drummondii tree balsam

Gastrolobium laytonii breelya, kite-leaf poison

Grevillea deflexa red grevillea

Grevillea striata beefwood

Gyrostemnon ramulosis fire bush

Hakea preissii needlebush, standback

Helipterum craspedioides billy buttons

Helipterum floribundum large white paper daisy,white sunray

Lawrencia squamata grey fan-leaf

Maireana aphylla spiny bluebush

Maireana atkinsiana bronze bluebush,five pin bluebush

Maireana convexa mulga bluebush

Maireana georgei George’s bluebush,golden bluebush

Maireana melanocoma pussy bluebush

Maireana planifolia flat-leaved bluebush

Maireana platycarpa shy bluebush

Maireana polypterygia Gascoyne bluebush

Maireana pyramidata sago bush

Maireana sedifolia pearl bluebush

Maireana thesioides lax bluebush

Maireana tomentosa felty bluebush

Maireana triptera three-winged bluebush

Maireana villosa silky bluebush

Monachather paradoxa broad-leaved wanderrie

Myoporum platycarpum sugarwood

Nitraria schoberi nitre bush

Pittosporum desert willowphylliraeoides

Ptilotus beardii low mulla mulla

Ptilotus exaltatus purple mulla mulla

Ptilotus obovatus cotton bush

Ptilotus polakii Gascoyne mulla mulla

Ptilotus rotundifolia royal or showymulla mulla

Ptilotus schwartzii horse mulla mulla

Rhagodia baccata berry saltbush

Rhagodia eremaea rhagodia, tall saltbush,climbing saltbush

Rumex vesicaria wild hops

Santalum spicatum sandalwood

Scaevola spinescens currant bush

Scaevola tomentosa ragged-leaf fan flower

Sclerolaena obliquicuspis limestone bindii

139

Sida calyxhymenia tall sida

Sida corrugata dwarf or prostrate sida

Solanum lasiophyllum flannel bush

Solanum orbiculatum tomato bush, wild tomato

Spartothamnella mulga broombushteucriiflora

Stipa elegantissima feather or silver spear grass

Stipa scabra spear grass

Stylobasium spathulatum pebble bush

Thyridolepis multiculmis soft wanderrie grass

Tribulus platypterus skeleton bark, corky-bark kallstroemia

Triodia basedowii hard spinifex

Triodia pungens soft spinifex

Velleia rosea pink velleia

Departments of Agriculture and Land Administration Rangeland Survey team at work in the Murchison.

140

Further readingRangeland survey reports• Lands of the Wiluna-Meekatharra Area, Western Australia, 1958 (1963) by J.A. Mabbutt etal. Commonwealth Scientific and Industrial Research Organization, Australia, Land ResearchSeries No. 7.

• A report on the condition of the Gascoyne Catchment (circa 1972) by D.G. Wilcox andE.A. McKinnon. Department of Agriculture, Western Australia, Technical Bulletin No. 2.

• A range inventory and condition survey of part of the Western Australian Nullarbor Plain,1979 (second edition, 1988) by A.A. Mitchell, R.C. McCarthy and R.B. Hacker. Departmentof Agriculture, Western Australia, Technical Bulletin No. 47.

• An inventory and condition survey of rangelands in the Carnarvon Basin, WesternAustralia (1984) by A.L. Payne, P.J. Curry and G.F. Spencer. Department of Agriculture,Western Australia, Technical Bulletin No. 73.

• An inventory and condition survey of rangelands in the Ashburton River catchment,Western Australia (1988) by A.L Payne, A.A. Mitchell and W.F. Holman. Department ofAgriculture, Western Australia, Technical Bulletin No. 62.

• An inventory and condition survey of rangelands in the Murchison River catchment (1994)by P.J. Curry, A.L. Payne, K.L. Leighton, P. Hennig and D.A. Blood. Department ofAgriculture, Western Australia, Technical Bulletin No. 84.

• An inventory and condition survey of rangelands of the north-eastern Goldfields, WesternAustralia (1994) by H.J.R. Pringle, A.M.E. Van Vreeswyk and S.A. Gilligan. Department ofAgriculture, Western Australia, Technical Bulletin No. 87.

Other relevant publications• Arid Shrubland Plants of Western Australia (1988, 1994) by A.A. Mitchell and D.G.Wilcox. University of Western Australia Press.

• Management of Australia’s Rangelands (1990) by G.N. Harrington, A.D. Wilson and M.D.Young. CSIRO Division of Wildlife and Technology, East Melbourne, Australia.

• A manual for the assessment of rangeland soil condition (1993) by David Tongway.CSIRO Division of Wildlife and Ecology, Canberra.

• Rangeland Management in Western Australia (1992) Department of Agriculture, WesternAustralia, Miscellaneous Publication 8/92.

943586/95/3M

141

The 850,000 square kilometres of WesternAustralia's arid shrublands stretch from theIndian Ocean north of Carnarvon, eastward andsouth to the famous Nullarbor Plain and theSouthern Ocean.

Across the expanse, larger than many individualnations, are vast sheep and cattle stations,historic settlements dating from the goldrushesand modern mining operations. This fascinatingenvironment has sometimes bee treatedcarelessly since Europeans began cutting itstimbers, digging its rich minerals and grazingtheir stock on the native shrubs and grasses.Damage has been done but experience of bothpastoralists and scientists is now offering help inproviding a better understanding of the needs ofthe land.

Reading the rangeland provides a practicalinsight into its condition, from the mulgashrubland to the spinifex sandplain, granites andthe breakaways. It will interest all who love andrespect this vast, uniquely Australianenvironment.

ISBN 0 7309 64647

Reading the rangeland: a guide to the arid shrublands of ...

Documents

Transcript of Reading the rangeland: a guide to the arid shrublands of ...