3
090A.EVM J58 c.2
RESPONSE OF AR¡D VEGETATION TO CATTLE GRAZING AND THE DEVELOPMENT OF INDICATORS FOR RANGE ASSESSMENT WITH PARTICULAR REFERENCE TO THE RANGELANDS OF NORTHERN SOUTH AUSTRALIA
by Peter Jessop
Department of Environmentat Science and Rangeland Management' The University of Adelaide
Thesls submltted for the Degree of Master of Applied Science (Natural Resource Management) The University of Adelaide
November, 1995.
+ CONTENTS
Acknowledgements ..""""""""""""'v Plant nomenclature...... """"""""vi
SECTION A: INTRODUCTION AND RESOURCE MAPPING CHAPTER 1 INIBODUqTION
1.1 Background to research. """""""'1 1.2 ptan ót research...... """""""""""'5 1.3 The Land condition lndex (LCl) as used in the assessment process...... 9 1.4 Climate of South Australia's northern cattle rangelands...'."..... """""'11 1.5 Stock induced grazing gradients (piospheres) """""""""' 16 19 1.6 The use of indiõators to assess range condition..'."...... ". """"""""""' 1.7 Comparison of the impact of sheep and cattle grazing"...... """"""""'23 1.8 The impact of cattle on chenopod shrublands """""""""'25 1.9 The imbact of catllê on perennial grasses..... """""""""" 26
CHAPTER 2 LAND SYSTEMS MAPPIrc
2.1 Mapping land systems...... """""""""'33 2.2 l-and systems described. """"""'36
SECTION B: PRINCIPAL METHODS FOR DATA GATHERING
CHAPTER 3
3.1 3.2 3.3 3.4
CHAPTER 4
4.1 4.2 4.3 Results... 76 4.4 Discussio 87
CHAPTER 5
5.1 lntroduction. 89 5.2 Methods...... 91 5.3 Results...... 93 5.4 Discussion'. """"""102 SECTION C: SUPPLEMENTARY METHODS FOR DATA GATHER¡NG CHAPTER 6 USE OF EXCLOSURES
6.1 lntroduction. 105 6.2 Exclosure sites and methods...... 108 6.3 Results...... 112 6.4 Discussion.. 116
CHAPTER 7 CROSS FENCE COMPAR
CHAPTER 8 TACCI¡¡C PENEHruNI
8.3 Results...... 127 8.4 Discussion.. 129
CHAPTER I nlsronlcal pnoroc
9.3 Results and discussi0n...... """""""""'132 g.4 Conclusions ...... 145
GHAPTER 10 pnoropolrur smes
10.1 10.2 10.3 10.4
SECTION D: DERIVED INDICATORS OF RANGE CONDITION, AND CONCLUSIONS
CHAPTER 1 1
11.1 Evaluation of indicators ....."""" 158 11.2 Application of the LCI concept in northern South Australia. 190 1 1.3 lncorporation of the derived indicators of range condition i into a draft LCI manual. :::*::::T::::::1i ,,,
CHAPTER 12
12.1 Reflections on the process used to derive indicators during this study 202 12.2 Conclusions 203 SUMMARY
This thesis investigates the response of perennial plants and soil surfaces to cattle grazing and develops indicators for range condition assessment in South Australia's northern cattle rangelands, the first time this has been done for this region. These indicators of range condition were needed (a) for incorporation into the Land Condition lndex (LCl) used by the South Australian Department of Environment and Natural
Resources to assess the condition of pastoral leases and (b) for use by pastoralists to
monitor their own performance as land managers.
Field work was mainly conducted on Todmorden Station (134'18' - 135'25'E.
26"54'- 27'35'5) in the remote north of South Australia, from March 1991 to September
1 993.
Three main methods were used to derive range condition indicators, all predicated
on the trend of increasing stocking impact with proximity to water:
1) The trends of frequency of occurrence of perennial plants along radial traverses
from four permanent watering points were analysed by a binomial logistic model.
2)Trends of density and cover of perennial plants and of litter cover were analysed
visually, by regression, and from interpretation of field notes.
3) Defoliation ratings, derived from observation of grazing impact and applied over
more traverses via rapid field survey, confirmed these indicator species and revealed
more indicators.
Other methods were also used where possible to supplement this information.
Historical photographs were of limited use because few were discovered and sites were
hard to relocate. lnterpretable cross fence differences were rare, and tagged plants and exclosures were of little value to me due to the short time period of observat¡ons.
The main indicators found were:
Sclenüflc namc Common namo Response to grazlng Range @mponent' Acaciaaneun (wenile) mdga lncreæe Irls,Sd Aeciaaneu¡a (mature) mulga D€creasg ¡Is,Sd,P
Acec¡e l¡guletr sarìdh¡ll waüe lncrease lrrs,Sd Aædabtesonqhyile dead finish lncrease ils,P Astedapctinaâ batuy Mbtell grass Decreass o,P bladder salbush D€crease o,P,c ,Attplexveslæria C¡otalziae¡emaæ loose-lowsed ratüepod Deqeass lils,Sd Enúylaena to'nentos€ ruby saltbush Decrease lrts,Sd Eragrætis eriopoda ìvoollybut Decrease t\,ls,Sd Erqrostis ætiÍolia nevsÈil lnitial inc¡eas€r but d€creas€s ¡f o,P hævy grazing conünues Erenofiilagilesil green ü.irl€y bush lncrease [,ls ErenØtilalatobd cdmson t¡rloy br¡s¡ Decrease ils,Sd úennphlandoorcllt ftrchs¡a bush lncrease l¡ls ttairænaa$yüa cotbobush lncrease o iilairæna astotld7á lorY blu€bush Deqease c lvbnadøther patadoxa bendcoot grass Decreasg rrs Panicum deæmposÌtum nalive milþt Decreas€ o,P nl/oùtsoùp/vafirs smokebush Decrease fvb,Sd var. obovatus Rhagodia s¡inesæns thorny saltbush Decreass ¡rs,Sd *nna atÞmisioidesssp. silver cassia lncrease l,ls,Sd a¡temislokles &nne erþrrl,¡s¡o¡desssp. pun$ bush lncrease sd frliloüt Sidaannqhila sand sila lncrease lvls,C Sldañbtl¡îê¡a ¡in sHa lncrease ÀIs,C %lanunellþîianr velvd potaùc bustr lncrease Iús,Sd adnodadus l€bora D€crease o,P
Rangc componenl' f :O -Oodnada¡tasalücushÞbl€land 2:P - Salôush end Me*rell gtass plains and plabaux 3: lr¡b - ùtrlga and horse mdga on deep ted san(s and dunes 4: C - It/laitæna asbotldø I Atiplex vesícana calcareous lab 5: Sd - Mulga and sendhil watlþsand dunæ
The use of the Land Condition lndex in the area stud¡ed remains problematical
because: 1) many perenn¡al grasses are hard to detect in drought e.g. grass tussocks
surv¡ve even if grazed flush with the soil surface, and
ll 2) the high resilience of most perennial grasses to drought means that vegetation which appears severely degraded often recovers markedly following rain.
Examples of such species are Astrebta pectinata, Sporobolus actinocladus and
Panicum decompositum. Any use of these species in LCI criteria will inevitably result in the value of the index reflecting seasonal conditions rather than reflecting true range condition.
In Chapter 11.2|conclude that a land degradation assessment system based on remotely-sensed data recently developed by CSIRO should be trialed for use in northern South Australia as an alternative to the LCI or more use should be made of
"utilisation" criteria in the LCI as a way around the problems.
ilr DECLARATION
This work contains no material which has been accepted for the award of any degree or diploma in any university or other tertiary institution and, to the best of my knowledge and belief, contains no materiat previously published or written by another person, except where due reference is made in the text.
I give consent to this copy of my thesis, when deposited in the University Library,
being available for loan and photocopying.
6 November 1995
lV ACKNOWLEDGEMENTS
Throughout the course of this study the Lillecrapp family, especially Douglas, were helpful and support¡ve. They allowed me access to their knowledge of Todmorden
Station and provided some of the materials for my study. However, thanks must also go to my Masters Degree supervisors, Brendan Lay (who also assisted in the development and execution of field work), Associate Professor Martin Andrew and Dr
Bob Lange who were always willing to help with advice when it was needed.
Other people and organisations who contributed to this study include:
Roseworthy Key Centre for Dryland Agriculture and Land Use Systems (¡n¡t¡ally) and the South Australian Cattle Compensation Fund (substantially)
which contributed generous research grants to enable this study to be
u ndertaken and completed.
Dr Bill Venables (Dept of Statistics, Adelaide University) for statistical advice and
Keith Cowley (Laboratory Manager, Roseworthy Campus) for field equipment.
Staff of the State Herbarium of South Australia for identifying my plant specimens.
The expeditioners of the Australian and New Zealand Scientific Exploration Society expedition "Simpson Desert One" (1991) and "Simpson Desert Two"
(1ee2).
Willing field assistants (Jamie Cornett, Matthew Turner and David Miller).
Staff of Todmorden Station for their company and help.
My parents who otfered advice and support throughout this study.
v PLANT NOMENCLATURE
Botanical nomendature follows that of Jessop and Toelken (1986), updated with recent specific changes as adopted by the South Australian Herbarium (J. Jessop, pers. comm.).
vt SECTION A: INTRODUCT¡ON AND RESOURCE MAP
CHAPTER 1 INTRODUCTION
1.I BACKGROUND TO RESEARCH 1.1.1 Changing attitude toward rangeland use
Throughout the world people's attitudes toward conservation and the management of natural resources are changing. Relatively recently, Australia's pastoral lands have become the focus of conservation groups who have highlighted the degradation and misuse of our arid lands. Already Australia, which has only recently
been developed in comparison with other countries, has the world's highest rate of extinction of native mammals, largely due to loss of habitat from changes in land use (Walker and Steffen, 1992). A report in 1986 on the state of the environment in
Australia estirnated that 51 percent of rural land in Australia requires treatment for some
form of land degradation (Commonwealth of Australia, 1986).
In the arid zones of Australia, where extensive livestock grazing has been the predominant land use for over a century, there is growing concern that these rangelands are still not being managed on an ecologically sustainable basis, i.e.
pastoralism, based on sheep and cattle, is causing continuing land degradation. ln the
past there was often severe degradation of the arid rangelands which Harrington et al.
(1984c) said was due to the lack of a coherent philosophy for their management. ln the
1890's one of the most severe cases of land degradation in Australia's history occurred in western New South Wales where sheep numbers crashed to a quarter of the¡r
previous level, never to recover. This prompted a Royal Commission in 1901 which
found that over-exploitation caused degenerative changes to the vegetation ànd land
(Roberts, 1924).
I However, while pastoral practices have improved there is still evidence in the literature that environmental degradation is continuing. A recent survey conducted in
Queensland's grazing lands suggests 20/" of the grazing resource was in a degraded condition and was not able to be restored economically (Tothill and Gillies, 1991). Mabbutt (1984) notes that around the world this trend is similar wherever rangeland occurs. Wuerthner (1993) reports that in the United States the Department of
Agriculture estimates almost 85 percent of all rangelands are at only 60 percent of their potential because of the loss of plant cover.
Because of this documented occurrence in rangelands of land degradation, desertification and reduced biodiversity, conservation groups are calling for stricter guidelines for exploitation through legislation which will require adherence to principles of ecologically sustainable use (Morton, 1993). This call for sustainable use has developed wider public support; thus governments are under pressure to implement stricter guidelines through legislation, leading to sustainable stocking rate controls and penalties for those land users who do not manage the land sustainably.
ln Australia land is controlled primarily by the States and Territories, most of whom are moving to ¡mplement stricter guidelines on the use of their rangelands and their management.
Recently Knight and Holmes (1994) reviewed regulations in each Australian
State aimed at achieving sustainable land use. Their review shows that South Australia and the Northern Territory lead the rest of Australia in the implementation of legislation aimed at sustainable land use. There legislation provides for a general duty of care (SA s7, NT s6) to prevent land degradation and to improve the condition of land (within the bounds of their capability).
2 ln Western Australia legislation is not as strict, requiring lessees to use the land 'in a proper and husbandlike manner'and to conserve the land to its best advantage
(s103). In New South Wales and Queensland there are no such general requirements, but in New South Wales lessees are directed not to overstock their land (s18D).
1.1.2 Relevance of this study
ln South Australia the recent Pastoral Land Management and Conservation Act (1989) requires (s4 & s6) that pastoral leases be scientifically assessed for "range condition", âîy problems specified and their carrying capacities prescribed, all by 7 March 1998. This legislation places obligations on both pastoralists and the Government. Pastoralists need indicators of range condition which can be used to make management decisions i.e. when to reduce or increase stock numbers and rest are¿F from grazing, in order that they can manage their properties sustainably, or risk penalties under the new Act. The State Government needs ¡nd¡cators to meet its obligations under the Act and determine objectively trends in land condition.
The South Australian Department of Environment and Natural Resources has developed a range assessment methodology to meet the requirements of the Act fl-he Land Condition lndex, hereafter referred to as the "LCl"). The LCI requires knowing, for any particular range type, what are the indicators (plant and soil) of range condition; e.g. which plant species become more abundant under grazing and which species tend to disappear.
However, while useful indicators of range condition are known for the South
Australian sheep rangelands south of the dog fence', they are not well defined for the northern cattle rangelands above the dog fence. This is because the majority of rangetand research in South Australia has been confined, for logistic and eòonomic
'The dog bnoe was bu¡lt b prer/ent dirBoes from harassÍng and k¡ll¡rìg streep in the ûavourable sh€€p pastrr€s (Fig. 1.3).
3 reasons, to the study of sheep rangelands closer to South Australia's populated centres. Tynan et al. (1992), for example, note that "in the southern chenopod shrublands of South Australia, the degradation sequence has long been documented in literature and from pastoralists themselves". While some ecological research has been conducted in northern South Australia by Jessup (1951) and Laut et al. (1977), none has specifically dealt with the impact of cattle grazing on these rangelands. lmportantly, the northern rangelands were not included in the Land System Survey work done by the Commonwealth Scientific and lndustrial Research Organisation (CSIRO) in the early 1950's.
1.1.3 Distinctiveness of the northern rangelands
There are many differences between the northern and southern South Australian rangelands which make it necessary to conduct research specifically to determine indicators of range condition for the northern rangelands. Firstly, unlike the southern rangelands, the northern rangelands are used exctusively for grazing cattle, because of dingo predation on sheep north of the dog fence. Cattle have different dietary preferences, different grazing behaviour, and it is suspected they have less grazing impact than do sheep. Refer to the comparison of the impact of sheep and cattle grazing in Section 1.7.
Secondly, rainfall in the north is markedly episodic and has a summer predominance unlike the southern parts where rainfall exhibits little seasonal predominance, but generally has a more reliable winter component. As there are also ditferent soiltypes between the northern and southern rangelands there are also major differences in the vegetation and thus the indicator plants of range condition. The southern rangelands are dominated by the family Chenopodiaceae and perennial grasses are of minimal importance while in the north there are fewer chenopods and a greater abundance of perennial grasses. These differences are discussed in more detail later in this chapter.
4 1.1.4 The main aims of this study were:
1. To develop a reliabte and credible Land Condition lndex for assessíng the condition of leases in the northern cattle rangelands of South Australia, as required under the Pastoral Land Management and Conservation Act (1989), and
2 To identífy and develop indicators of range condition for use by pastoralists.
1.2 PLAN OF RESEARCH
A plan of research is outlined in Fig. 1.1. Before commencing the field work, a review of literature relevant to cattle grazing in northern South Australia was conducted.
This review focused on the impact of cattle on chenopod shrubs and perennial grasses because very little work has been undertaken on this topic in South Australia. lt is summarised at the end of this chapter.
Before research methodology was decided upon, a visit was made to Alice
Springs where talks were held with scientists from rangeland units of the CSIRO, the
Northern Territory Conservation Commission and Department of Primary lndustries and
Fisheries about the feasibility and usefulness of techniques for identifying indicators of
range condition in central Australia. Almost all research conducted on the impact of cattle grazing relevant to South Australia's northern rangelands has been conducted
by these Government agencies.
My research has focused on determining ground surface and perennial plant indicators of range condition. Ephemeral and annual plant indicators were not determined because their presence and growth is reliant on favourable seasonal
conditions. By contrast perennial plants persist in all seasons in numbers sutficient for
range assessment purposes.
5 SECTION: A
CHAPTER 1 INTRODUCTION Background information
CHAPTER 2 LAND SYSTEMS MAPPING Basis of field work
B c MAIN METHODS SUPPLEMENTARY METHODS
CHAPTERS 3-4 CHAPTER 6 STUDIES OF GRAZING GRADIENTS EXCLOSURES
CHAPTER 5 CHAPTER 7 PALATAB¡LITY AND DEFOLIATION CROSS FENCE COMPARISONS OF PLANTS BY CATTLE CHAPTER 8 TAGGING PERENNIAL GRASSES & SHRUBS
CHAPTER 9 HISTORICAL PHOTOGRAPHS
CHAPTER.IO PHOTOPOINT STTES
SECTION: D
CHAPTER 11 INDIVIDUAL SPECIES DIGEST AND DRAFT LCI CRÍTERIA FOR THE BANGE COMPONENTS STUDIED
CHAPTER 12 FINAL CONCLUSIONS ON THE PROCESS USED TO DERIVE INDICATORS ¡N NORTHERN SOUTH AUSTRALIA
Fig. 1.1 Outline of thesis.
6 Research was conducted from March 1991 to September 1993 (2.5 years) and the focus was on identifying indicators of range condition rather than developing new rangeland sampling techniques. Hence proven rangeland sampling techniques were employed and informat¡on was obtained using a range of methods.
Originalty it was considered that three adjoining pastoral leases Todmorden, Allandale and Welbourn Hill should be studied because they collectively contain representatives of the major land systems of the study region. However, later reconnaissance showed Todmorden to possess a good representation of most of the land systems occurring on the other cattle leases in the region and this station otfered certa¡n logistic and scientific advantages. Thus the majority of research was conducted there. However, limited research was conducted on other Stations i.e. Hamilton and
Bitla Kalina because they contained more uniform representations of some range types.
Five approaches were used: 1) The first involved mapping the land systems in the study area. After ground reconnaissance and overlaying with station and topographic features (fences,
waterpoints etc.) this map became the basis of most field work (Chapter 2).
2) Notes on cattle grazing impact were recorded from my observations and the opinions of pastoralists during extensive field trips, and have been used as
sources of information. The National and Conservation Parks in the region
(Witjira National Park and the Simpson Desert Conservation Reserve) were also visited so that comparison of vegetat¡on ungrazed by cattle could be
made with similar vegetation on cattle stations.
3) Quadrat sampling along grazing gradients ("piospheres" Lange, 1969; see Section 1.5) from permanent watering points of known grazing history were
used to reveal plant indicators of range condition by showing changes in the abundance of plants and ground surface parameters induced by cattle
grazing (Chapters 3-4).
7 4\ A defoliation index was developed which enabled fast and accurate documentation of the preferences and thus impact cattle have for particular plant species (Chapter 5). lt is known that generally those plants most palatable to livestock usually decrease while those not palatable usually remain static or increase in abundance (Heady, 1964). Thus information gained from this index provided supportive documentation for the more
objective sampling techniques and provided information to pastoralists on the
palatabilities of their forage species. 5) Supplementary studies included the establishment of exclosures and photopoints to document the recovery of grazed areas after rain. The degree
of recovery of plants after rain can be used as an indicator of range condition
by showing whether plant survival and vigour has been reduced. Exclosures
also highlight the preference cattle have for particular plant species and the
degree of grazing on them (Chapter 6).
Other supplementary studies involved: a) the comparison of cross fence differences, b)tagging of perennial plants to determ¡ne the¡r palatab¡¡¡ty and the impact
of cattle on them, c) re-location of scenes from old photographs and d) with independent
evidence such as pastoralists knowledge of stocking rates and comparison of similar areas not stocked to show stock induced changes over time. These techniques are outlined and discussed in Chapters 7-10.
1.2.1 Outline of chapters
Each chapter contains an Introduction, Methodology and brief Results section
but discussion regarding range condition indicators is drawn together in Chapter 11 of
this thesis.
I 1.3 THE LAND COND|T|ON TNDEX (LCr) AS USED lN THE ASSESSMENT PROCESS
As already mentioned the Land Condition lndex (LCl)was developed in southern
South Australia as a tool for assessing the condition of leases in South Australia (Tynan et al., 1992). Thus a summary of the LCI is given here.
, Before the LCI can be used a manual must be prepared identifying the main range types in the district to be assessed e.g. "Low woodlands" and "Chenopod shrublands". The sub-units called range components within these range types e.g.
"Maireana astrotríchacalcareous flats within chenopod shrublands" are then identified.
Then for each range component a set of three classes are determined which describe the condition of the land as st¡pulated by the South Australian Pastoral Land
Management and Conservation Act (1989) (class 1 : does not comply with the Act = poor condition;class 2: nominal compliance: fair condition;and class 3: compliance with the
Act = good condition). Condition classes are based on indicators of range condition such as density of perennial plants known to increase or decrease following grazing, and ground surface indicators such as the exposure of bare soil to wind and water and its subsequent erosion. These indicators of land condition and subsequent assessment criteria can be determined from stock grazing gradients out from water (piospheres). The further from water the less intense the stock grazing pressure and the higher the
condition class rat¡ng tends to be.
Once the indicators of range condition have been determined for a range component a set of reference photographs are prepared as a field guide, and assessment criteria are written which enable the three land condition classes to be
identified in the field.
9 These photographs and written criteria comprise the manual and arc subsequently used by range assessors to determine the land condition of pastoral
leases comprising these described range components.
The actual process of assessment using these land condition criteria is briefly
summarised as follows.
First the assessors measure (from maps) the total length of the assessment tracks to be followed during the¡r assessment of a particular pastoral lease. These
tracks are based on existing station roads and an attempt is made to travel through all
the major range components. A traverse is divided into 100 equal intervals. A random
number generator is then used to determine 100 stopping points along the tracks (one
within each interval). At each point the assessment standards are used to derive a
score, assisted by photo-guides in the manual. The results from all these scores are
used to calculate the overall weighted condition of the lease (Table 1).
A "Robustness lndex" is also derived to provide an adjustment for the different
inherent susceptibilities of different range components to degradation. However, this
is a separate index from the LCI and is not relevant to my study; thus I shall not discuss
it further.
For a more detailed description of the assessment process and how the LCI and
Robustness lndex are used, see Tynan et al. (1992).
10 Table 1 Example of the determination of the weighted condition of a lease from 100 assessn¡ent stops. The minimum and maximum values possible are 100 (all points are class 1) and 300 (all points are class 3).
f chss Percentage of Total (100) Land Condition Stopping Points
3 x 50= 1 50 t2 x 20= 40
1 x 30 Condition Score for Lease 220 lClass of Land Condition | - poof I = fair 3 = good
1.4 CLIMATE OF SOUTH AUSTRALIA'S NORTHERN CATTLE RANGELANDS.
Major climatic, soil and vegetat¡on differences exist between the northern and southern rangelands. Powell and Badman (1990) state that "arid rangelands of South
Australia are divided into grasslands in the north and chenopod shrublands in the south.
However, there is no clear cut boundary between these range types but rather a large area of intergradation. This is due predom¡nantly to summer rainfall pattern in the north and less well defined rainfall pattern in the south" (Fig. 1 .2). Leigh and Noble (1969) show the boundary of this rainfall separation (Fig. 1.3).
The ephemeral growth response periods in central Australia are mostly initiated
by single rainfall events and last less than five weeks (McAlpine, 1970). The greatest number of rainy days in northern South Australia occur in the "summer" months (October to February) and in the winter months (June to August) (Jessup, 1951). However there is no marked seasonal rainfall as the region lies in a zone where the limits of the southern w¡nter rainfall and the northern monsoonal summer rainfall systems overlap (Jessup, 1951).
11 zl
'Áepo¡ oules aq¡ 6u¡aq sB Etlellsnv qlnos lo unlleqlaH alels aql r{q palllra^ uooq SELI tnq uolleloôen ueedolnf -aJd smoqs deu s¡q1 '(OeO t 'slmol pue eu.Jstlloog laUB :9901 'llllseCct^l pue ullluÐ :acrnog) Elprlsnv qnos lo suolletcosse uollele6en rofey\ z'l'6lJ
.-,r'.61] l ,n,"."."." t",""ol -,,"'".'""",,,-.... i I ' I- Èt'.óldô uaoue 6rc PUEtqnrqs púetqhrqÉ IPI qnii6 uadO nunrnoonn Fã ra"ror I s€rJ06olej uorlElã68^ uotlele6aA ueedo¡nf -erd P å .-:,'-, . 1r;i;. ill 'ìl & .- dË-è oqF I "Þ 't:J ri \. l: I I I .s\¡]. tt t. auf,pt I r 136 I 130 132 l3{ N.T QLD. z6 ---___ _ -';::.'...-; ú a ?få¡Tæ z v) { a 8ec¡t Dos fææ: )çXiff Adel¡lde Eo@düy of Yi¡rter rnd arF€r r¡i¡f¡ll 1969)' tntt m (Sq¡ræ: f:i6h t Foble. '-':.':'.. - lesea æ vithi¡ tlris ¡¡e¡:;:-":':' P8.6toral :.-: . fodærda St¡tldl: I auLltoo St¡tÍ6: Z H 0 ¡OO 100 300tm o Bilt¡ f,allor 6t¡t1oo: 3 Fig. 1.3 South Australia locality map 13 Laut et al. (1977) state that most of the northern rangelands have a mean annual rainfall of about 150mm with the exception of the Musgrave ranges in the north west with a mean annual rainfall of 200mm. The pattern of rainfall for South Australia is shown in Figure 1 .4. The rainfall records for Todmorden Station since 1948 show the average annual rainfall has been approximately 175mm for the past 42 years while the average annual rainfall for Billa Kalina Station (the most southerly cattle station studied) i5 153mm for the period 1955 to 1989 (Department of Environment and Planning, 1991). These averages have littte practical meaning because rainfall is extremely variable (Stafford Smith and Morton, 1990). The Bureau of Meteorology ranks ten of the northern South Australian cattle Stations as being in the driest places in Australia. This includes Murnpeowie Station which holds a42year record for having the least rainfall in Australia (between 1893 and 1936), with an average yearly rainfall of 105mm. But while dry conditions are common in northern South Australia, after rain the river channels and creeks provide some of the best cattle fatten¡ng country anywhere. George Bennett (a pastoralist) was quoted in 1907 as saying that in the far north of South Austratia "if every season were good no country in Australia could approach it for healthfulness or for stock raising" (Burges, 1907). Temperatures in the study region range from mild in winter to very hot in summer. At Oodnadattathe January mean maximum is 38.2'C and the mean minimum is 23.2"C. The coolest month at Oodnadatta is July when the mean maximum temperature ¡s 19.4'C and the mean minimum 5.8"C (Laut et al., 1977). ln this region winds from southerly to easterly directions are frequent. during summer (January) while winds from northerly to westerly directions are tarc. ln winter (July) winds are more commonly from a westerly direction, and not as strong as in summer (Laut et al., 1977). 14 13e 132. 134' t36' t 3a' 140. 25' 26' 2q. 28' 150 30' 3tr ¡Cook ¡ Woomera 37 3T ¡ I Pt 34' 34' 500 MEDIAN ANNUAL RAINFALL iN M ILLIMETRES ALLYEARS OF RECOBDS 36' 36' Ending APRIL 1992 Eleqa6 600 t@søonO lø ñ m m¡sffgE l:tOO -- o Mount O æ' t30' l3? 134' 136' ræ" 140f Fig. 1.4 Rainfall map of South Australia, showing mean annual isohyets (Source: Bureau of Meteorology, Adelaide). 15 1.4.1 Hainfall during the study period At the start of this study in March 1991 South Australia's northern rangelands were experiencing drought. On Todmorden Station rainfall for 1990 (106mm) and 1991 (85.Bmm) was well below average. However, good rainfall was recorded throughout 1992 (308.4mm) and 1993 (218.4mm). As I had not begun the piosphere work until 1992 all my measurements for this work were undertaken during two years of good rainfall when perennial plants, especially perennial grasses had sufficient time to grow. lnvestigations involving exclosures, photopoints, historical photographs and monitoring of perennial plants were, however, begun in 1991 and therefore reflect not only dry conditions but also wet conditions. 1.5 STOCK TNDUCED GRAZING GRADIENTS (PIOSPHERES) 1.5.1 The piosphere concePt Cattle grazing in northern South Australia is similar to other arid environments and is centred around places where cattle can drink. Therefore, there is a gradient of increasing grazing pressure towards any watering point. A normal grazing gradient is roughly linear away from water and involves those environmental variables which register the effect of stocking e.g. erosion, soil structure breakdown or responses of forage plants; on average there will be a gradual increase in vegetation cover with distance from water (Pickup & Chewings, 1991). ln South Australia this was first studied by Osborn et al. (1932) and later by Lange (1969), Barker and Lange (1969), Rogers and Lange (1971), Barker (1972), Graetz (1978), Graetz and Ludwig (1978), Andrew and Lange (1986a,b) and Andrew (1988) all of whom identified sheep grazing gradients in chenopod shrublands. The term "piosphere" is used to describe th.e zone of grazing influence around a watering point (Lange, 1969). t6 The piosphere phenomenon is important to this study because it is has been used successfully in South Australia's southern sheep rangelands to determine indicators. The piosphere provides a means for determining indicators of range condition by sampling plant and soil surface parameters across the grazing gradient. 1.5.2 Cattle lnduced grazing gradients I In South Australia the study of cattle grazing gradients has been confined to the chenopod shrublands and has been studied by Fatchen (1975, 1978) and Fatchen and Lange (1979). Fatchen (1975) reported that the basic form of a cattle piosphere is similar to that of the sheep piosphere, in that (a) radial gradients centred on the water point exist in the vegetation; and (b) these gradients can be detected by sampling for linear relationships between various plant parameters and distance from water. Most research relevant to cattle grazing gradients in Australia, other than those by Fatchen (1975, 1978), have been undertaken in central Australia. Afewauthors have studied the grazing behaviour of cattle from water, e.g. Hodder and Low (1978)' Low et al. (1978) and Squires (1978), but not many have sampled grazing gradients. Foran (1ggo) reports that the etfect of distance from a watering point was examined for two range types in central Australia grazed by cattle. He found that because the vegetation around the watering point was not uniform and indeed was rather patchy, no clear piosphere pattern was evident. He attributed this to the different preferences cattle showed for the different types of vegetation. However, beyond 2km in the open woodland and at about 2km in the mulga annual woodland environmental degradation caused by grazing animals decreased. Bastin et al. (1983), also working in central Australia, examined how vegetation cover changed with distance from water at two sites grazed by cattle. Results showed 17 that litter and herbage components affected by grazing pressure increase with distance from water ln the U.S.A. Valentine (1947) detected cattle induced radial vegetation patterns in forest range centred on the watering point similar to those proposed by Osborn et al. (1932) for sheep, but Herbel et al. (1967) could find no such cattle induced patterns on árid range in New Mexico. 1.5.3 ldentifying piospheres in South Australia's northern rangelands It was not known whether it would be possible to ¡dent¡fy cattle grazing gradients in northern South Australia because the conditions required for a piosphere pattern to emerge often do not hold, for three reasons. 1. The vegetation is not uniform in many areas but strongly patterned as a mosaic of several vegetation types of differlng overall palatability. Thus Pickup & Chewings (1988), working in central Australia, suggest the common outcome is a star shaped pattern of distinct corridors of activity between the water point and the areas of more palatable vegetation. Hodder and Low (1978) found this to be the case. They examined the effect of differential grazing pressure on the mosaic of plant types around watering points in central Australia. Cattle were observed to walk through seemingly good forage to get to another community. 2. This grazing behaviour, combined with unreliable rainfall which is usually localised, tends to concentrate grazing in areas of recent rainfall where preferred range types are greenest. Therefore there may be patches of heavy cattle grazing which are not consistent with the average grazing gradient. This confounds any attempt to define the grazing gradient. 3. Another possible problem is that after rain, water is ponded for long periods in depressions on many of the land systems e.g.the Oodnadatta land system 18 which has a high proportion of gilgais. This means cattle do not need then to rely on permanent art¡fic¡al water such as bores. Heavy grazing may then take place anywhere. Thus an objective of this Masters Degree research was to determine whether it is indeed possible to detect cattle grazing gradients and use them to determine indicators of range condition, as has proved successful in southern Australia. 1.6 THE USE OF INDTCATORS TO ASSESS RANGE CONDITION 1.6.1 Plant indicators Plant indicators are those species which portray the character of the habitat and are most important in showing the initial decline, or improvement of forage cover (Sampson, 1g3g). ln areas subjected to grazing, indicator species generally manifest themselves via a palatability hierarchy. Grazing pressure favours species of low palatability and discourages the growth of palatable plants. The increase or decrease of particular ptants is based on their sensitivity or resilience to grazing and whether they are growing in a marginal habitat (wilson and Harrington, 1984). The more useful indicators are those confined to a narrow range because they react strongly to habitat changes rather than a species which is tolerant of many conditions (Sampson, 1939). Atso a group of species rather than an individual is regarded as a more favourable indicator because they usually reflect more consistently environmental factors (Tansley and Chipp, 1926). Clements (1928) says that plants affected by indirect factors such as wind or slope are unreliable indicators while the more reliable are those which react strongly to direct factors, such as soil aeration or temperature. The concept of indicators to show changes in environmental conditions is not new. Sampson (1939) says that plant indicators have been used since 300 B.C. when Theophrastus recognised that on exposed, sunward slopes the growth of trees was t9 different from those growing on the cooler northern slopes. ln medievaltimes Tragus noted lhat Asarum is confined to shady moist spots, usually under thickets of hazel. ln the eighteenth century Unger (1836) recognised that the growth of plants is largely influenced by the chemical composition of the soil and that a change in chemical composition of soil will bring about a change in plant species composition. Today indicators are used in agriculture to show over-utilisation of paddocks and in mining to l'ielp find mineral dePosits. ln rangeland ecology the concept of indicators has been used extensively in the United States of America where much emphasis has been placed on the increase or decrease of certain plant species under grazing. However, in Australia not much has been written on this concept nor has it been studied to as great an extent. The concept of increaser and decreaser plant species was first outlined by Weaver and Hanson (1941) working in Nebraska, who subjectively categorised dominant range species into three groups according to their response to grazing. These three categories were: those plants which decrease, those that increase and those which invade. This represented the first use of indicators to show decline in range condition. The first quantitative assessment of range condition using indicator plants was undertaken by Dyksterhuis (1949) who quantitatively grouped species as decreaser, increaser and invaders based upon percentage cover of "climax vegetation" in response to grazing. Climax vegetation is the plant community which represents a long term steady state of productivity, structure and species composition at a given site (Odum and Odum, 1959). The proport¡ons of increaser to decreaser plant species represent ditferent states of range condition. This method known as the "Dyksterhuis Quantitative Climax" approach (Friedel, 1991), is based on the notion that community change is gradual and predictable, with downward trend in range condition occurring in response to grazing, and it is assumed that reduction or removal of grazing pressures allows 20 successional processes to restore the range to what it was. This method now forms the basis of one of the most widely used methods for assessing range condition. ln Australia, Barker and Lange (1969, 1970) identified indicator plants of range condition while studying chenopod shrublands in South Australia. They found that there was a change in density of certain plant species from water. Two main indicator plants rri,ere Drbs oærpus paradoxuswhich increases with grazing and Atríplex vesicaria which decreases with sheeP grazing. Lendon and Lamacraft (1976) described the standards for testing and assessing range cond1ion in central Australia (STARC). They are partly based on the Quantitative Climax method as they use indicators to show change in range condition. For instance bluebush (Maireana astrotricha) slopes show decline in range condition by a decrease in Enneapogon avenaceus and an increase in Salsola kali (Bastin et al., 1983). Williams (1969), working on the Riverine Plain in New South Wales, determined increaser and decreaser plants using a response index and a grazing pressure index based on plant densities in grazed and ungrazed treatments. Tainton (1986) described the range condition assessment methods then in use in South Africa and says species are classified, within each recognisable range type' into a number of categories, each category representing a particular seral stage. These categories were classified according to increaser and decreaser indicator plant species. 1.6.2 Soil surtace indicators While the use of indicator plants usuatly forms the major basis of range condition assessment, soil surface indicators can atso be used to determine condition. lt is well known that trampling and grazing by livestock has the affect of reducing vegetation cover and ground surface structure. This leads to truncated soil horizons; lack of a 21 normal amount of organic soil between groups of herbs or shrubs and the built up of soil at the base of trees and shrubs indicating soil erosion (Sampson, 1939). Rogers (1g7z\showed that the soil cryptogamic crust in South Australia's semi- arid rangelands is susceptible to trampling by livestock. lt therefore exhibits the piosphere pattern and can be used as an indicator of range condition (Rogers and Lange,1971). Johns et al. (1984) report that grazing by livestock pulverizes the soil surface thereby reducing aggregate size and compaction of the soil which leads to reduced infiltration, increased runoff and smaller soil water store. Andrew and Lange (1986a) found there was increased soil compaction caused by trampling of sheep on Middleback Station in South Australia. Condon et al. (1969) said that isolated areas of erosion have always been part of Australia's rangelands but these have become more widespread with the advent of stock. Tatnell (1992), working near Broken Hill, found percentage bare ground to be an indicator of the ability of the landscape to harvest seed, water and dung (nutrients). Tongway and Friedel (1992) found there was reduced stab¡l¡ty of soil surfaces in areas where cattle were heavily utilising shrublands in central Australia. Thus by examining soil surfaces in areas of different cattle utilisation it might be possible to identify soil surface indicators of changing range condition for northern South Australia. 22 1.7 COMPARTSON OF THE IMPACT OF SHEEP AND CATTLE GRAZING As most literature from South Australia deals with sheep grazing it seemed logical to try to determine whether there are likely to be differences in the impact of sheep grazing compared with that of cattle. Although there is very little literature available on comparison of sheep and cattle grazing, it is generally agreed cattle are less destructive than sheep. Here is some of the evidence. jaw 1 Cattle cannot graze as close to the ground. The structure of the lower of cattle makes it impossible for them to graze closer than 12mm from the soil (Hafez et al., 1969; Leigh, 1971). But sheep can graze virtually to soil level damaging the roots in awaythat cattle cannot (Hafez et al., 1969). This means that sheep are able to harvest small grass tussocks and out compete cattle during drought conditions (Wilson, 1976; Graetz and Wilson, 1980). Hence, cattle grazing in competition with sheep will lose weight faster than sheep. ln Australia this has lead to a higher degree of defoliation and mortality of grasses in the south compared with the cattle rangelands in the north (Graetz, 1980). 2. Cattle are less selective than sheep. Cattle tend to eat more of the dominant plant, whether it be grass or bush, more dry grass and less of the smaller grasses and forbs such as medics. This is thought to be due to cattle having a lesser physical ability to select at a finer scale than sheep rather than to an intrinsic difference in the acceptance of plant species (Arnold, 1981). This conflicts with point three and my own observations which indicate that cattle actively Waze gr¿Fses in preference to shrubs. g. Shrub mortality is less under cattle because cattle graze more and browse less than sheep (Vallentine, 1989). Harrington and Pratchett (1973), working 23 on the Ankole rangeland in uganda found cattle avoided non-grass species, while chippendale (1968) found cattle only utitised small quantities of the browse. Galt et al. (1969) demonstrated the low proportion of browse in rangeland' diet of cattle compared with sheep grazing an arid united states Fatchen (1975), studying sheep and cattle piospheres in a rangeland density of dominated by Maireana astrotricha and ephemeral grass, found that the grazing decreased Enneapogon avenaæus increased away from water under cattle but of Aristida from water following sheep grazing. .However, he found that the average size with distance contortaincreased with distance under cattle but its density increased under sheep. For Maireana astrotricha, piosphere symmetries were consistently detected for sheep but not for cattle. Gritfin and Friedel (1985) report that comparative studies of the etfects of cattle and sheep on saltbush (Atríptex vesicaría\ and bluebush (Maireana death of astrotricha) are not available but it appears cattle are less destructive, since bluebush is rare and regeneration of bluebush, although highly variable has not been shown to be inftuenced by cattle in central Australia. pressland (1976) found that sheep were more destructive of mulga seedlings are harder than were cattle and there appears to be a commonly held belief that sheep on shrubs than are cattle. (1983) Opposing views are presented by Low et al. (1973), Squires and Siebert prefer annual and Squires and Low (19g7) who all found that in central Australia cattle grasses and forbs to perennial species but browse made up a large proportion of the diet when annuals were not available. 5. Cattle usually gtaze further from water than sheep. During good feed conditions in central Australia, most cattle graze within 3km of water, but 24 under moderate to poor conditions they can gtaze to 8km (Hodder and Low, 1978; Low et al. 1978). Sheep however usually graze within 1 .Skm of water in arid areas (Squires, 1978) but may graze to Skm when feed is scarce (Lynch, 1974). Thus the cattle piosphere gradient is less steep and grazing is less concentrated than for sheep. ¡ The above evidence indicates that sheep grazing is generally more destructive to vegetation than is the equivatent amount of cattle grazing and that the impact of cattle is probably more likely shown by grasses,than by the (less preferred) shrubs. 1.8 THE IMPACT OF CATTLE ON CHENOPOD SHRUBLANDS ln South Australia very little has been written on the impact of cattle grazing chenopod shrubtands because most rangeland research has been confined to the study of sheep south of the dog fence. But because some of the range types above the dog fence comprise a high proport¡on of chenopod shrubs it was important to determine the probable impact of cattle on these range types. Because the chenopod shrublands are so different from the grasslands and sorìe work has been done on chenopod shrublands I shall examine the two broad range types separately. The grasslands are reviewed in Section 1.9. 1.8.1 Northern South Australian chenopod shrublands In northern South Australia the chenopod shrublands occur as dominants or as understorey constituents of woodlands or in association with tussock grasslands (Specht, 1972\. These shrublands are dominated by species ol Atriplex, Sclerolaena and Maireana with local dominance by Rhagodia. Of the chenopod species ltriplex vesíæriais most frequently the dominant chenopod and can be present at densities of lOOO to 2000 plants/ha of 30cm diameter and height (Williams, 1982). 25 1.8.2 Cattle grazing chenopod shrublands Within South Australia the only literature which deals with research into cattle grazing on chenopod shrublands has been undertaken by Fatchen (1975) who studied the ¡mpact of cattle introduction onto sheep rangelands in southern South Australia. Fatchen (1975, 1978) found that cattle eliminated Atríplex vesicaria and caused a decrease in the density ol Maireana astrotrícha. Fatchen and Lange (1979) found there was no change in the abundance ol M. astrotrichafrom water following replacement of sheep with cattle grazing on Mount Victor Station. Gritfin and Friedel (1985) reported that bluebush (M. astrotricha) and saltbush (A. vesicarial¡ communities are grazed by cattle in Australia. Both species are eaten by cattle but only during drought. Saltbush may have been lost north of the MacDonnell Ranges where the environment is marginal but both are considered to be resilient under cattle grazing in the south. Leigh and Mulham (1965) and Askew and Mitchetl (1978) report that heavy grazing ol Rhagodia spinescens by cattle may lead to its decline or total elimination on the Riverine Plain and in the Northern Territory. Graetz and Wilson (1980) say that within the chenopod shrublands cattle have strong preferences, with bladder saltbush (A. vesicana) being preferred over bluebush (M. astrotricha), cottonbush (Maireana aphytla), and pearl bluebush (M. sedifolr,a), whilst black bush (M. pyramidata) is rarely eaten. 1.9 THE IMPACT OF CATTLE ON PERENNIAL GRASSES 1.9.1 Grass formations There are principally two grass formations in northern South Australia rangelands grazed by cattle: those communities with tussock grasses and those with hummock grasses as dominants or in the understorey (Specht, 1972). Firstly, tussock grasslands 26 occupy the margins of the semi-arid zone where the rainfall has a summer incidence. The community consists characteristically of small circular or oval tussocks of Mitchell grasses and provides the bulk of the d¡et of the majority of cattle in the northern rangelands during or immediately following drought. Hummock grasslands are associated with the far northern areas of the State especially the Simpson, Tirari, Strzelecki and Great Victoria Deserts (Powell and Badman, 1990) and comprise the genera Stipa, Aristida, Eragrostis, Tríodia and Zygochloa. Triodia and Zygochloa species are perennial but unpalatable, and are never grazed to a large extent. Of the remainder, Eragrostis, Stipaand some Aristidaspecies are perennial but vary in their palatability (Specht, 197 2\. 1.9.2 Cattle preference Squires (1981) and Wilson and Harrington (1984) agree that cattle have a preference for certain plant species. lt is agreed that grasses make up the majority of the diet. However, it is also agreed that the diet selected by cattle in inland Australia is extremely variable and is governed principally by the choice of forage available. Thus a food that has a relatively low palatability in one season or area may form the bulk of the d¡et at another time or place. Secondary factors atfecting the diet selected are the frequency with which cattle encounter a forage plant, as opposed to the bulk of that food available to it and the degree to which hunger is satisfied. Because the bulk and quantity of the food avaitable to cattle in inland Australia is so variable, no general statement about their diet composition can be made, other than that they are generalist herbivores with a capacity to eat forbs, grasses or topfeed species as the situation dictates (Squires, 1 981 ). Leigh (1971) reports that grass is the most important component of the diet of cattle grazing in the semi-arid regions of Australia, contributing from 80 to 100% of the volume of forage. 27 Cattle have a preference for soft and "sweet" plants. This preference involves the selection of green plants or green components of plants before dry components, and leaf before stem (Arnold, 1981). The material eaten is usually high in nitrogen, phosphorous and gross energy but lower in fibre. When ephemerals are growing they usually make up the majority of the diet. Squires (1981) says that following summer rains cattle select the short lived perennial, annual and ephemeral grasses such as bottlewashers (Enneapogon avenaceus, E. polyphyllus), button grass (Dactyloctenium radulans) and the various panic grasses (Panícum effusum, P. decompositum). However, when the ephemerals dry off or have been grazed beyond their usefulness the more palatable perennial grasses such as woollybutt (Eragrostis eriopoda) are selected because these retain green leaf longer and so are the next to be eaten (Williams, 1970). The final category is the less palatable perennial grasses which supply drought fodder. When the ephemerals are available these perennial grasses such as Mitchell grass (Astrebtaspp.) escape grazing and therefore are able to build up their food reserves. Grazing pressure on these plants can be intense during dry times but by then the reserves are held either close to or beneath the ground. The growing points of these grasses are low enough to escape most grazing and so the plants are able to respond rapidly to rain (Harrington et al., 1984a). The dietary preference hierarchy of cattle for plant species varies slightly from winter to summer due primarily to different plant species' growth responses. ln winter, some forbs and perennial grasses respond to rain; hence gilgaid areas wilh Eragrostis setifoliaand E. xerophita are sought out initially. After summer rains, the flood plains produce annual grasses and appear to be sought out first. A complicating factor here is that perennials tend to respond most quickly after rain, and cattle initially gtaze these plants. However, as soon as annual grasses reach grazeable height, cattle prefer these over perennials (Low, 1972). 28 1.9.3 Response to grazing All, or nearly all, established perennial grasses survive a single complete defoliation,.whether by clipping or by heavy grazing (Williams, 1970; Hodgkinson, 1976; Brown, 1986). Wilson et al. (1988) say that rangeland plants differ in their ability to withstand defoliation by grazing. At low levels of defoliation the survival of all species is unatfected; however at some threshold level of defoliation (defined by both severity and/or frequency and which is presumably different for each species) plant survival is reduced, as is the productive vigor of those individuals that survive. Because of their basally located meristems, grasses are better adapted to close grazing than shrubs with their predominantly aerial meristems. Some grasses, although resistant to grazing when established, succumb to defoliation at the juvenile phase (Wilson et al., 1988). Grazing can alter the botanical composition of rangeland vegetation directly by accelerating mortality of some species and, indirêctly, by altering the competitive environment of the plants that remain, and by influencing the recruitment success of species in the gaps created by plant death. The shape of the response curve to grazing pressure will be species dependant and linear, convex or concave, but most plant growth and reproduction parameters decline with increasing grazing pressure (Ellison, 1960). McNaughton (1979) proposed that grazing may benefit plants by compensatory mechanisms (such as increased tillering, photosynthetic rejuvenation of leaves, etc.), but the limited experimental evidence supporting this theory has been found to be inconclusive (Belsky, 1986). lt may apply in special environments, such as nutrient rich soils, but for rangeland grasses it should be assumed that leaf area production is diminished, often substantially, by grazing. For example Bosch and Dudzinski (1984) 29 found that in central Australia the h¡ghest seed head production lor Cenchrus ciliaris (buffel grass) came from ungrazed and lightly defoliated plants. An exception are the Mitchell grasses (Astrebta spp.), where moderate grazing is often regarded as producing a more desirable and vigorous community than no grazing; exclosure leads to lower seed production (Groves and Williams, 1981 ; Orr and Evenson, 1991) and a decline in plant density (Groves and Williams, 1981). With increased frequency or intensity of grazing, production by grasses usually decreases (McQarty and Price,1942i Lewis et al., 1956; Klipple and Costello, 1960; Dwyer et al., t g63; Jameson, 1963; Bosch and Dudzinski, 1 984; Richards, 1 993)' Both above ground and below ground production and root reserves have been shown to be inversely related to frequency or intensity of use (Weaver, 1950; Troughton, 1957; Reed and Peterson, 1961;Dwyer et al, 1963; Jarvis and Macdutf, 1989; Richards, 1993). Weaver (1950) indicated that with increased utilisation of grasses, root weight and depth of penetration were reduced. 1.9.4 Trampling and excretion Snaydon (1981) says that few quantitative studies have been made regarding the effects of treading on the grourth and botanical composition of pasture; lt seems that usually treading does not have a major effect on yield, except in wet conditions. Vallentine (1ggQ) saystrampling does not have a maioreffect on pasture efficiency unless the forage is dense. Dung or urine have large local effects upon the yield, quality, palatability and botanical composition of pasture. However, the etfects on the whole pasture are much less, because only a small area is atfected (Snaydon, 1981). Thus in the extensive arid zone, these etfects are minor but they could accumulate over time near the centres of piospheres. 30 1.9.5 Morphological resPonse This section is included for completeness, but these issues proved rather peripheral to this thesis. Hence, this topic is only briefly discussed. Booysen et al. (1963), Jameson (1963), Davidson (1968), Arnold (1972), Va¡entine (1989), Vallentine (1990) and Richards (1993) describe the morphology of perennial grasses and how this is affected by grazing and the response which follows. The account given here is a summary of their work. The response of a perennial grass to grazing is dependant on species, stage of growth, its condition, and the extent to which it is defoliated (Booysen et al', 1963; Arnold, 1g72; Richards, 1993). When the vegetative shoot apices of perennial grasses grow to a height of more than 12mm above the soil surface they are susceptible to removal by the grazing animal (Booysen et al., 1963; Jameson, 1963; Arnold, 1972). lmmediately following defoliation there is a reduction in photosynthesis, carbon gain, translocation of previously fixed carbon temporarily stored in source tissues and phloem loading activity stops (Richards, 1993). Once the shoot apex is removed, no more leaves are produced on that axis and vegetative growth is greatly decreased until new tillers develop. Also, when the apical meristem enters the reproductive stage no new leaves are produced on that tiller. Thus the effect of either the removal of the vegetative shoot or apex or the transition of the apical meristem from the vegetative to the reproductive condition is to prevent any further development or replacement of photosynthetic tissue on the tillers of the plants. This will reduce the ability of the tiller to recover from defoliation and the plants will have a low degree of resistance to grazing as new foliage is dependent on the production of new tillers. Species differ in regard to the time and duration of elevation of the shoot apices and the proportion of apical meristems which become reproductive during the growing season (Booysen et al., 1963; Richards, 1993). 31 Grasses less tolerant to grazing usually have weak shoot meristematic activity following defoliation. This is because a higher proportion of carbon resources are allocated to the roots following defoliation (Richards, 1984). Nevertheless, root elongation ceases within 24hrs after removal of 40-50% or more of the shoot system and fine roots may die (Jarvis and Macdutf, 1989) leading to a decline in nutrient absorption because of reduced root respiration. Thus carbon is lost from the actively growing shoots. These effects may increase in nutrient deficient environments (Chapin and Slack, 1979). However, in grazing tolerant plants the effect of reduced root growth generally benefits the plant by reducing carbon and nitrogen loss to the roots and allocating it to actively growing meristematic regions in the shoots. This restores photosynthesis and has a multiplicative effect on the plants carbon balance by allowing the plant to recover more rapidly (Richards, 1993). 32 CHAPTER 2 LAND SYSTEMS MAPPING 2.1 MAPP¡NG LAND SYSTEMS Before commencing field work it was first necessary to undertake some form of map-based survey of the region to determine the extent of the major range types and their variability. The South Australian Department of Environment and Natural Resources (Pastoral Management Branch) suggested land systems mapping should be undertaken for Todmorden, Allandale and Welbourn Hill pastoral leases because they collectively comprise the major land systems in the study region. Land systems mapping involves defining an area or groups of areas throughout which there is a recurring pattern of topography, soil and vegetation (Christian & Stewart, 1953) and is based on the premise that each type of country appears on satellite imagery and aerial photographs as a distinctive pattern. Other researchers who have used land systems mapping include Wilson et al. (1984) who say that for mapping purposes, land units are otten collected together into land systems for rangeland assessment. Land units are the "geomorphic entities which make up the total landscape and include such features as alluvial fans, channel systems, footslopes, and mesas" (Pickup, 1985). Dawson and Boyland (197a) report on the work conducted by the Commonwealth Scientific and lndustrial Research Organisation Division of Land Research in Queensland. Christian & Stewart, (1953), Perry et al. (1964), Gunn et al. (1967), Story et al. (1967), Speck et al. (1968), and Galloway et al. (1970) have shown the usefulness of an inventory of rangeland ecosystems based on land systems surveys of land units. "Range component" is used by the South Australian Department of Environment and Natural Resources as an equivalent term to land unit and so it has also been used in this thesis. 33 Land system mapping was attempted on two separate occasions during this study. First, Multi Spectral Scanner (MSS) hard copy satellite imagery of the scale 1:250,000 was used in conjunction with geological and topographical map sheets at the scale 1:250,000, to map the land systems onto paddock plans for Todmorden, Welbourn Hill and Allandale Stations. Ground truthing showed this was relatively successful but that the land system boundaries were not always accurate. At this stage of the mapping process it was decided to make Todmorden Station the main focus of field work because it has good representation of most of the land systems in the study region and had certain logistic advantages. Thus colour aerial photographs at the scale 1:88,000, which afford a higher level of resolution than Multi Spectral Scanner Landsat imagery, were used in another attempt to map the land systems accurately, on Todmorden Station only. The use of aerial photographs to map land systems is recommended by Low et al. (1981), Bastin et al. (1983), Wilson et al. (1984) and Payne et al. (1987). Following this, another ground reconnaissance was undertaken with Douglas Lillecrapp (the Todmorden lessee) whose detailed knowledge of Todmorden proved invaluable in helping to produce an accurate map of the six land systems on Todmorden (Fig. 2.1). This land system map was subsequently adopted by the Marla/Oodnadatta Soil Board in conjunction with the South Australian Department of Environment and Natural Resources as part of their land systems mapping of the district. However, only five land systems on Todmorden contained range components which were uniform enough to enable a cattle piosphere pattern to be detected (Oodnadatta, Coongra, Wooldridge, Alberga and Pedirka land systems). They are described in the next section. Breakaway land system is also described but was not studied because it was difficult to find sufficiently vegetated areas for study. 34 f! I LÆT¡ AY8TEre, EXCLOEUREE f.) At5 Sil,rDY STTES I F|tt o--{ o- ADJ¡|. 3 o lbonlold Doæ Coo¡ta o- o [colûld.. f I q, ffi f 'ni,.'F o l?.*.Try U, tr a A ¡rolom tll¡ (D )f I Fencetlne Stotlon loow|dqly o - -' - -' ox Hofì €æned rood o Stotld trock UI vqtercourse yord, (¡) ca Tqnk bore, roterho(e o ql (D Ø 0) Ploce nones tdenttFy sltes reÊerred to ln th. text o_= orìd ofìl,y roÀds to sttes Ø ore no¡ked, c o_ 9.. (D a ll ^ olEt2lan ó, l..Æ KMt 2.2 LAND SYSTEMS DESCRIBED The names of the six land systems described are taken from the Marla/Oodnadatta Soil Conservation District land systems map. Within each land system there are range types e.g. "Low woodlands" and ,,Chenopod shrublands" which are divided into the range components. Range components that occur in sufficient number and size for scientific study are described in this section and were used to determine indicators of range condition. 2.2.1 Oodnadatta land sYstem Oodnadatta land system comprises of two major range components, the first being Atríptex nummularia ssp. omissa I Atriplex vesicaría - Oodnadatta saltbush tablelands. This component consists of uniform ftat to undulating gibber tableland with gilgais normally aligned along contours and dissected by shallow creeklines which grow Acacia aneura(mulga) and Acacia cambagei(gidgee). The gibber may vary from dark red to black in different areas and range in diameter from a few centimetres (pebble size) up to 10-1Scm. Soils are saline and dispersive either deep red clays or clay loams. Gilgais vary in size from about 1 metre up to about 5 metres in diameter and support the majority of vegetation. Gilgais are the most productive component of this land system. They are able to trap water runoff from the stony impervious flats which surround the gilgais. The water is retained for extended periods because the clay soils are dispersive which reduces water infiltration (Charman and Murphy, 1991). As the gilgais retain water and soil moisture for long periods they provide an excellent growing environment for many plant species and hence are used intensively by cattle (Ratcliffe, 1936). 36 Gilgais are usually dominated by perennial plant species of which Atriplex nummularía ssp. omíssa (Oodnadatta saltbush) and/or Sclerostegia medullosa (samphire) are the dominant shrub species wilh Panicum decompositum (native millet), Astrebla pect¡nata(barley Mitchell grass) and Sporobolus actinocladus (katoora) being the dominant perennial grasses. Sporobolus caroli(fairy grass), Eragrostis setífolia (neverfail) , Abutílon halophilum (plains lantern-bush), Irpogon loliiformr's (five minute grass) and occasionalty Maireana aphylla (cottonbush) also grow in gilgais. After rain the gilgais also grow a high proportion of annual and ephemeral grasses and herbs. The most common annual grasses are Chloris pectinata (comb windmill grass), Eriochloa australiensrb (Australian cupgrass), /se/ema membranaceum (small Flinders grass) and Enneapogon spp. (bottlewashers). On the less productive gilgai tringes grow predominantly perennial plants such as Atríplex vesicaria (bladder saltbush), Sporobolus actinocladus, Eragrostis setifolia, Frankenia serpyttifotia (bristly sea-heath) and Anemocarpa podolepidium (rock everlasting). After winter rain there is also a sparse scattering of ephemeral herbs and forbs. The dense covering of gibber stones provides a protective layer which normally protects the soil from wind and water erosion (Ratcliffe, 1936). However, when erosion does occur it is usually confined to station tracks and areas directly surrounding stock watering points. Erosion at these sites is caused by repeated stock or vehicle movement which leaves the soil surface exposed to wind and water. Ratcliffe (1936) reports these tablelands are highly resilient to erosion but says soil sometimes blows in from areas of less resilience. The larger watercourses and their floodplains which are separate from the Oodnadatta saltbush tablelands and which had no piosphere studies conducted on them, are also very productive. After rain they grow a range of ephemeral and annual plants which provide excellent feed for fattening cattle. However, scattered individuals 37 of a small number of perennial plants such as Astrebla pec'tinata, Frankenia serpyllifolia, Atriptex nummularia ssp. omissa, Atríplex vesicaria and Maireana aphylla also grow' Eucalyptus coolabah (coolabah) and Eucalyptus camaldulensis (red gum) dominate the river channels. The second range component examined on this land system was lhe Atriplex vesicaria / Astrebla pec'tinataflats and run-on areas - Stony tablelands. This range component consists of flats and run-on areas dominated by Atriplex vesicariaand usually Astrebta pectinata. Atter rain annual and ephemeral plants grow but they are usually sparse. Soils are deep red clays or clay loams which are saline and dispersive with a heavy quartzite stone cover. This range component is widespread in Oodnadatta l.s. and may be heavily utilised by cattle during dry conditions. The Astrebla pectinafa component of the pasture is generally resilient to cattle grazing (Orr and Evenson, 1991) bul Atriplex vesicariais susceptible to grazing and will decline if over utilised (Fatchen, 1975, 1978). The quartzite stone cover provides a protective soil covering which is not easily removed. Thus severe erosion is rare except where stock and/or vehicle movement has been heavy. 2.2.2 Coongra land sYstem Coongra land system is dominated by lhe Atriplex vesícaria I Astrebla pectinata - Saltbush and Mitchell grass plains and plateaux range component. These undulating gilgaid stony tablelands consist of vast sandstone and shale covered slopes, plateaux and plains dominated by Atriplex vesicaria (bladder saltbush). Stones are rounded or angular and range in size from 3 to 30cm in diameter. Similarly 38 to the Oodnadatta saltbush tableland these stones form an erosion resistant layer unless the stones are disturbed by vehicle or stock movement. The slopes are treeless except for the occasional Eremophila freetingü (rock fuchsia bush) which grows on the tablelands, Acacia cambagei(gidgee) and/or sparse Acacia aneura (mulga) which grow along shallow creeklines and Eucalyptus coolabah (coolabah) which grow in larger watercourses. Atriptex vesicaria grows in association with the perennial grasses Astrebla pectinata, Panicum decompositum and Sporobolus actinocladus and the perennial sub- shrub Frankenia serpyltifolia (bristly sea-heath) and occasionally Anemocarpa podotepidium (rock everlasting). The majority of perennial plants growing here are the same as those growing on the Oodnadatta saltbush tableland. But unlike the Oodnadatta l.s. the perennial grasses here grow thinly amongst the sparse Atriplex vesiæría which dominates gilgai fringes. However, like the Oodnadatta l.s. the densest pockets of perennial grasses are confined to gilgais After rain the Coongra stony tablelands are very productive growing a wide variety of annual, ephemeral and short lived perennials palatable to cattle. The stony tablelands are therefore heavily utilised by the cattle industry, especially in dry times because of the immense perennial plant component palatable to cattle. 2.2.3 Wooldridge land sYstem This land system forms a trans¡t¡onal area between Oodnadatta and Alberga land systems and is characterised by a combination of highly calcareous flats fringed by sand dunes and stony flats and run-on areas similar to those on Oodnadatta land system. The first range component studied is the Maireana astrotricha I Atríplex vesicaria calcareous flats. 39 The open calcareous flats grow open communities of Maireana astrotricha (low bluebush) or Atríptex vesicaria (bladder saltbush) or a combination of both, neither being of much palatability to cattle except during dry periods (D. Lillecrapp, pers. comm.). lndividuals of both species are separated by areas of bare ground which grow predominantly annual grasses and herbs after rain. These annual grasses are usually dominated by Enneapogon spp. (bottlewashers) and Arístida contorta (kerosene grass). But Dssoca rpus paradoxus (cannonballs), Sclerolaena spp. (poverty bushes), Salsola kali (buck bush), Srda spp., Eremophila spp. and Senna spp. are also common in many areas The other range component studied on this land system is the Acacia aneura I Acacia ligulata (Mulga and sandhill wattle sand dunes). The dunes usually form boundaries between the open flats, and support a greater variety of perennial plants, most of which are palatable to cattle. The main overstorey vegetation is dominated by Acacia aneura (mulga), which may form thick groves. However, Acacia ligulata (sandhill wattle) is usually more frequent but does not grow to be as large as mulga. The open dune understorey usually consists of a variety of shrubs, bushes and perennial grasses which provide moderate drought fodder. However after rain a wide variety of annual and ephemeral plants also grow whích are good for fattening cattle. 2.2.4 Alberga and Pedirka land systems Alberga land system consists of alluvial plains and sand plains dominated by Acacia aneura (mulga). The mulga overstorey on the sand plains is not always randomly distributed but may grow in groves 30-40 metres long and 5-50 metreb wide, usually aligned along contours and separated by intergroves where trees are absent or sparse. 40 The alluvial plains consist of similar vegetation to the sand plains except directly adjacent to water courses where there is an abundance (following rain) of Sclerolaena spp. and annual grasses such as Enneapogon avenaceus (oat grass) and E. polyphytlus (limestone bottlewashers). However, the alluvial plains were not studied much during this Masters Degree because it was difficult to f¡nd sufficiently uniformly vegetated areas for study and most of the plant species were already being studied on the sand plains. Pedirka land system however, consists of sand dunes and interdunes dominated by Acacia aneura and A. ramulosa (horse mulga) overstorey. Mulga is usually confined to the deep red loamy sands of the interdunes, while horse mulga dominates the deep red sands of the dunes. The sand plains from Alberga land system and sand dunes from Pedirka land system have been grouped inlo Acacia aneura I Acacia ramulosa (Mulga and horse mulga on deep red sands and dunes) range component because the plant species are similar on both land surfaces. Mulga and horse mulga grow over a variety of perennial bushes and grasses and are therefore often referred to as mulga perennial grass woodlands. However, following rain annual and ephemeral plants grow but never form a very dense cover. The pasture varies seasonally in composition (more grasses after summer rain, more forbs after winter rain. ln the northern cattle rangelands the mulga perennial grass woodlands are usually only utilised for cattle grazing during dry periods. This is because the perennial plants which grow here are not nutritious enough to fatten cattle. However, perennial vegetation will sustain cattle over extended periods (D. Lillecrapp, pers. comm.). The mulga perennial grass woodlands in the northern cattle rangelands are generally in good condition except within 1.Skm of waterpoints in many cases. Most of 41 the perennial plants are fairly robust under cattle grazing but because of their low nutritional value pastoralists are less inclined to utilise them heavily. 2.2.5 Breakaway land system This land system has not been classified into range components because it rivas not studied during this Masters Degree. Nevertheless, a general description is provided. Breakaway land system consists of low h¡lls, tablelands and plains dissected by watercourses and is dominated by chenopod shrublands. The low hills comprise shallow sandy clay loams and support a sparse low shrubland of Atriptex vesicaria (bladder saltbush) and Frankenía serpyllifolia (bristly sea-heath) with isolated Acacia aneura (mulga) and Eremophila freelingii(rock fuchsia bush). After rain Tripogon loliiformis (five minute grass) and Arístída contorta (kerosene grass) may also grow. Low hills are of low pastoral value because their vegetation is grazed by stock only during periods of low rainfall when other more palatable and accessible plants are not available. The gently undulating tablelands and plains are covered by gibber or shale or a mixture of both. Soils are solonized red duplex soils with clay textures supporting a sparse low shrubland of Atríplex vesicariaor Maireana astrotricha (low bluebush) with sparse Acacia aneura, Acacia stowardii(bastard mulga), Senna spp. and Acacia catcicota (northern myall). Halosarcia spp. (samphires) may also grow in some areas 42 The tablelands and plains are predominantly grazed by cattle during dry periods when Atriptex vesicaria and Maireana astrotricha may be heavily utilised. However, after rain, however, annual grasses may grow and be sought by cattle. The alluvial soils of larger watercourses are dominated by a low woodland community of Eucatyptus coolabah and Acacia aneura over perennial bushes and grasses. Smaller watercourses are dominated by Acacia aneura, Rhagodia spinescens (thorny saltbush), Atriplex vesicaria, Enchylaena tomentosa (ruby saltbush) and Enteropogon acicularis (curly windmill grass). The larger watercourses and their floodplains are highly productive following rain when a range of ephemeral and annual plants suitable for fattening cattle grow. During dry seasons, as with the smaller watercourses, perennial grasses and bushes provide feed suitable for maintaining cattle condition. 43 SECT¡ON B: PRINCIPAL METHODS FOR DATA GATHERING CHAPTER 3 THE USE OF CONTINUO TNDICATOR PLANTS OF RANGE CONDITION 3.1 INTRODUCTION This chapter describes a study to determine indicator species of range condition, using traverses from permanent watering points through uniform range components. The aim was to reveal any trends in relatíonships between plant species frequency and distance from a water point and to reveal whether or not any such trends were significant statistically. Uniformity of vegetation was essential for this if piospheres were to be detected, as is the case in southern South Australia where the piosphere work was initiated (Lange, 1969). 3.2 MATERIALS AND METHODS The frequency of various plant species was determined along several radial traverses from four permanent water points on Todmorden, Hamilton and Billa Kalina Stations. Two distinctively different land systems predominant in the northern South Australian cattle rangelands with uniform range components (allowing changes in species frequency with distance from water to be detected against minimal environmental noise) were stud¡ed during this work: Alberga l.s. (Mulga and horse mulga on deep red sands and dunes) and Oodnadatta l.s. (Oodnadatta saltbush tableland). Two permanent watering points with distinctly different stocking historieö were chosen in each of the Mulga and horse mulga on deep red sands and dunes and 44 Oodnadatta saltbush tableland so that comparisons of the same range component under different grazing regimes could be made. 3.2.1 Selection of traverse sifes Sites were selected after reconnaissance to be uniform representations of major riange components. Sites were also chosen to allow a radial traverse to be run in a predetermined direction for at least Skm without being impeded by structures which might influence the grazing gradient i.e. fences, other watering points and variations in type of country. I judged that 5km was the minimum traverse length needed to determine significant changes to vegetation caused by cattle grazing, from my reconnaissance out from permanent watering points. This was also later confirmed when results from the traverses showed that cattle grazing impact declined dramatically beyond Skm. 3.2.2 Traverse sffes Only four uniformly vegetated sites could be found; unfortunately only two were heavity grazedbut these were the best I could find to apply the conventional piosphere approach. Oodnadatta saltbush tableland l: Hyde Dam on Hamilton Station (Fig. 3.1), 10km north of the Hamilton homestead, is representative of an Oodnadatta saltbush tableland; i.e. uniform gilgaid gibber plain on which the predominant perennials included Abutilon halophilum, Astrebla pectinata, Atríptex nummularia ssp. omrissa, Eragrostis setífolia, Panicum decomposltum and Sporobotus actinocladus. These were predominantly confined to the gitgais. Atríplexvesíæria and Frankenia serpyllifolla dominated the elevated areas surrounding the gilgais. 45 f! ç S.) Hyde Dam ot- o fence difference 3 t\ !) o=. f o 0) (D U) ao 0) Brownies Paddocl( of o o Ø Ø à o q) :l LEGEND oc) q -|- ra-ck: -.....- o o Fe¡-rce:- :t -T- oc) ra.verse: Timber Camp Bo û) - o Boundary Bore r@ 0 r ¡ ¡ . 5 5 7 s 9 ro(roñ!t,? f !)- o=. f Ø !) õ' = This dam was established approximately 25 - 28 years ago and has mainly been used to water station horses and small numbers of cattle. A census on the number of horses and cattle watered here has not been kept but it is thought that recently there have only been small numbers (maximum of twenty at any one time). However, the gilgais in the arca arc degraded, which implies higher stocking rates than present; apparently most of these were stock horses. 2: Tucker's Bore on Bilta Kalina Station (Fig. 3.2), 25km north of the Billa Kalina homestead, is representative of a light to moderately grazed uniform Oodnadatta saltbush tableland dominated by Sclerostegia medullosa and Atriplex nummularia ssp. omíssa. This bore was established in the early 1960's and has been used to provide water for about 80 cattle including calves for the past 30 years. However, in a reasonabte year 130 cattle may drink f rom this bore. The lessee regards this as being a light to moderate stocking rate. Mulga and horse mulga on deep red sands and dunes 3: Wyjundi Bore on Todmorden Station (Fig.2.1), 17.5km north of the Todmorden homestead, is representative of a lightly cattle grazed mulga perennial grass woodland. The major perennial species growing here on deep red loamy sands are Acacia aneura, Acacia tetragonophylla, Enchylaena tomentosa, Eragrostis eriopoda, Eremophíta gilesii, Eremophila latrobei, Eriachne helmsii, Maireana georgei, Monachather paradoxa, Rhagodia spinescens, Sennaspp. and Solanum ellipticum. This bore was established in 1964 and has been used only to water catt¡e during drought. For the past 28 years the stocking strategy used at this bore has been to water approximately 200 cattle for a six month period about once every 2-3 years. The paddock is then de-stocked for the rest of the time allowing the vegetation to recover. 47 Mudla Bore I I I a f I I I I t t Tuckerls Bofe I a I raverses a a I ]\T a ¿ a a a a a t , t a TON apiirfs Bore a a a I I a a a ¡a a LEGEND -r- rack: ¡¡r.'r f errcel- 5 lO kms Fig. 3.2 Location of traverses on Billa Kalina Station. 49 When this traverse was undertaken, cattle had not watered at the bore for about two months. 4: Boundary Bore on Hamilton Station (Fig. 3.1), 15km south east of the Hamilton homestead, has a heavier cattle stocking history. Boundary Bore was established at about the same time as Wyjundi Bore (1964) and simitarly is used only during dry periods. However, the number of cattle watering here has often been up to l OOO head of cattle for a six month period. When this traverse was being undertaken, there were approximately 10 cattle watering atthis bore. The vegetation around both bores is similar, bul Eriachne aristídea only occurs at Boundary Bore. However, the landscape at Boundary Bore is slightly different in that there are scattered sand dunes approximately 15m in height. 3.2.3 Sampling procedure Oodnadatta saltbush tableland At Hyde Dam a radial traverse bearing 250 degrees and 5.7km in length was used as the basis for placement of belt quadrats (Fig. 3.3). Due to the natural contouring of the landscape and hence its vegetation a 100m tape measure was divided into two 50m halves, each half placed at 45o from the traverse line (Fig. 3.3). The 50m halves were then marked into 10m x 2m sub-quadrats which were used to record all perennial plant species. The belt quadrats were placed at 100m from Hyde Dam and every 200m thereafter until at a distance of 2km it was apparent a larger distance interval between 49 2OO 100(n 204 Fig. 3.3 Traverse out from Hyde Dam. 50 belt quadrats would be adequate. Thereafter belt quadrats were placed at 500m intervals until the end of the traverse. At Tucker's Bore two radial traverses were undertaken because the first traverse on a bearing of 120o from Tucker's Bore and 7km in length sampled vegetation which was not as uniform as the initial reconnaissance suggested. Thus a second traverse én a bearing of 80" was also used. The procedure of placing belt quadrats along a traverse from Tucker's Bore was identical to that used from Hyde Dam (Fig. 3.3). lt was occasionally necessary to change the interval due to variations in the vegetation which coincided with the sample points. Only the common perennials were recorded, to allow for piosphere trends to be detected. Mulga and horse mulga on deep red sands and dunes At Wyjundi and Boundary Bores traverses 5km in length were run 10m from and para¡el to existing westerly heading station tracks. A belt quadrat was undertaken at 100m from each bore and then at 200m intervals thereafter, run at right angles from the traverse (Fig. 3.4). Ten 10m x 2m quadrats were placed on both sides of a 100m tape (20 quadrats in all) to record the occurrence of perennial grasses. Ten 10m x 10m quadrats along both sides of the tape were used to record the occurrence of all other perennial plants. Only perennial grasses and shrubs which could be positively identified were counted. perennial grasses were often difficult to identify and therefore usually needed to be ftowering for positive identification. Multi-stemmed shrubs were scored as individuals 51 (J9 fOOd 20oñ 1O0m 1.O0n to 5lñr 2Jf.i fOfr IJ'10ú Fig. 3.4 Traverse out from Wyjundi and Boundary Bores. 52 if there was a gap of greater than 3Ocm between living rooted stems or for grass butts a gap of 30cm between living rooted butts. Juvenile plants were not distinguished from adults using belt quadrats because the aim of the exercise was to determine frequency change of a species from water. However, notes were kept on plant regeneration during species counts and these are ihcluded in the results where applicable. Where a large individual occurred on the border between two quadrats the quadrat with the majority of the plant was scored. As with the Oodnadatta saltbush tableland the plants recorded were the cÐmmon perennials. 3.2.4 Statistical analysis Frequency (out of 20) was calculated as the summed presences of each plant species from twenty sub-quadrats in each belt quadrat. The binomial logistic regression model was used to analyse the data statistically. This model assumes that the probability p(¡) of finding the species at distance x ¡s described by the logistic curve, thus: 53 p1 <0 1 Species FrequencY p(x) p1 >0 0 Distance from water and was s-Plus by statistical sciences lnc' The computer software package used as follows: the printout of the results was interpreted not' then Deviance was significant' lf it was (a) I first checked whether the Residual anindependenceassumptionofthemodelwassatisfiedandthet.valueforß1 indicatedsignificanceoftheincreaser/decreasertrend.Thatis,anyt-value>2 5% of p(x) on distance from water at the would imply that there was dependence positive t indicating an increasing trend level of significance;x degrees of freedom, trend with distance' and negative t indicating a decreasing not then the independence assumption did (b) rf the Residuar Deviance was significant optimistic. lt was then necessary to hold and the t-value would have been too adiustment is called the heterogeneity make an adjustment to the test. This correction (Z). Z= t-value resid ual deviance d-f > 2 is significant at the 5% level since zis astandard Normal Deviate, then Z water' even dependence of on distance from and one can validly claim that there is PG) the model is not met' though the independence assumption of 54 3.3 RESULTS There were no species in common between the two land systems;thus the land systems are treated seParatelY. The results of statistical applications are summarised by Tables 3.1 - 3.2. or more fourteen species showed significant trend with distance from water at one bores and these are discussed in Section 3.3.1. Those species which were not significant on any traverse, (Table 3.3) were placed into two categories, as follows. (The inclusion of a species into a category is based on my observations on its abundance at each traverse site). Category A Species sufficiently frequent to support statistical analysis but which failed to register as a decreaser or an increaser species. Category B Species too scarce to enable a cattle effect to be revealed, even if one existed. 3.3.1 Spe cies which were statisttcatly signiîicant at one or more of the waterlng points. ln this section only the key features of each significant species are discussed as my final inferences and arguments are given in Chapter 11. Oodnadatta saltbush tableland Astrebla pecti nata (barley Mitchell grass) No trend was detected for Astrebla pectínata from Hyde Dam (App. 1.1). However, at Tucker's bore both traverses (App . 1.2 & 1 .3) showed that there was an increase in Astrebla pectinataaway from the bore. 55 Table 3.1 Summary of results of stat¡st¡cal analysis (Oodnadatta saltbush tableland) Specles for anatysls flResldual Devlancc (01) z lncreaso + / Decrease' wlth d¡stancr from water llyde Dam Æutilur lølophilum 43' -1.63 Astre,bleo€'cl¡neb 55' 4.62 Atidex nwmula¡b ssP. omissa 42' o.93 0.55N.S Atiplexvesianía 78' 1.47 0.64N.S Engrostls setlÍolla 17N.S -290 -L74' Franl Tucker'e Bore (Traverso 1) Astcbla pecilnata 1531 8.47 3.0r + Atþlex nmmularb ssP. omrbsa 114' 4.42 Atiplexvedæria 60' 1.63 Er4qrætß ætilolia 103' 4.37 1.92N.S ìvbirænaaphylla 30N.S 0.87 Panlcum deæmpositum 55' 2.15 1.æN.S Sdetosteg¡a medullosa I 10' 1.¿ß Sporobol u s aclinoclad us 19s' -2.06 -0.66N.S Tucker's Bors (Traverse 2) Abutilm lølophilum 59' -2.52 Ãstebla pecdnata 168' 7.07 2.49' + Atþlex nwnmulada ssp. ornissa u' 0.03 Atiplexvesiæda 71' 3.æ 1.7sN.S Eragrorsds setlfolla l04. 452 203' + 50' l.9sN.s For oxplanatlon of thê,Rqgldual Devlance'and'? (heterogenelty clrecüon) see Soctlon 3.2.4 Statlstlcal analysls. # Resldtnl flevlance - it signlficant at 5% then Z b the statistic us€d. ' Signiñcant at 5% bvel. lds - not significant at 5%. 56 Table 3.2 Summary of results of statistical analysis (Mulga and horse mulga on deep red sands and dunes). Specles for analYsls fResldual Devlance (ß1) z lncreasc + / Dec¡ease- wlth dlstance hom water Wylundl Bo¡þ Aæciaaneu¡a (wenile) 91' 0.63 Aæciaaneuø (mature) 65' 0.94 Acada tet4gonoPhYlla 10r 3.63 1.79N.S Enchylaena tomentosa 91. 6.07 3.24' + Engrostls etlopoda I 18' 425 Ercmophlla gllesll 170' s27 2.05' + Ercmqhilalatobei 94' f .69 úiaúnehelmsñ 8' {.48 't.9N.S lvbirænageorçpi 180' 4.96 l,bnaúather pa¡adoxa 69' {.97 Bhagodla splnoscêne 39N.S 22n 1.80N.S + Senne atum¡s¡o¡&s ssp. arternistbrles 18rÍl' 3.s6 1.34N.S &nna atþmisioides ssP. frliÍolia 58' 2.69 1.80N.S þlanum elllpticum 18' 7m 4.24. + Boundary Bore Aæciaanewa (wenile) 80' 3.30 1.57N.S Aaciaaneun (mature) 88' 2.86 1.3N.S Acælatebagonophylla 14N.S 1.7'i2 2.26' + Crctalariaeæmaea 73' 0.77 Enchylaena lomenb,sa 41. 5.f7 3.¿14' + fuagrostis e¡iopoda 92' 0.51 úunophila gilesü 179' 3.45 1.08N.S + Ercmophlla latrcbel 1 14' 552 219' ûtachne adsúdea 26N.S -2.07 -1.43N.S Eriacfne helmsñ 90' 2.73 1.22N.S Malreana georgel 121' 7.08 2-73' + lvbnadnther paradotca 1æ' 4.87 1.82N.S m/p.us obovetus 116' 1.12 Fhagodia splnesæns 10r 1.16 *nna atÞmisioides ssp. arfernisiodes 168' 2.61 0.86N.S &ona atþmislddes ssP. fil ilolkt &' -2.78 -1.8sN.S 81' 0.23 For.xplanatlon of thc.Resldual Devlanc¡" and'? (heterogenelty corecdon) sec S€ct¡on 32.4 Statlstlcal analysls. fl Rssldual D'ovlance - if s¡gnlñcant at 5% then Z b üì€ stalistic used. 'Signlñcant at 5% þvel. NS - not s¡gn¡ficant at 5%. 57 Table 3.3 Species which were not stat¡stically significant at any water po¡nt. 3 of Specles water Polnt 1 Pd"r"blllty Ratlng 2 category Dlslrlbutlon 4 (diverse hequencies Abutilon lølqhilun HD b A aøoss range) Abøilm lnlodtilum TBl'2 b B Aacia aneun$xenlel WEBB 2b,3 A Aacia aneu¡a(mafrÍe) WÈBB b A Atrlplex ntmmularh ssP. HD-TBI'2 3 A omissa Atriplexvesicaria HD-T812 b A Crotala¡ia etenee¿t BB A Eremqhilalatobei WB b A fuía*nehelmú WB àb B (frequendes limited almost€nlirdy tc 0, 5o/"1 (diverse frequendæ Eriactne helmsi BB bb A "cfî'Tn") Franl lvlairænagærgei WB b A lvlon adt athe r p arad o xa W&BB 1 A (mosüy abs€nt) Hiloas obovatus BB b A (diverse fiequendes Sclerosteg¡e medtllæa TB1 3 A aøoss range) WEBB 2c A (mosüy abs€nt) W&BB 2c A (moet frequencies limited b 0oÁ) BB 2c A (diverse frequmcies acfoss Tucker's Borc (traverse f or 2 WB Wylundl Borê, BB Boundary Borc 1. HD = llyde Dam, TB = ), = = Z- palatablllty retlngs for percnnlal plants recorded, basod on my obseruaüons ln tñe fleld: 'thls 's Raüng 1) sp€dæ always Palaùable to catüe. Raling 2) 'Ih's speci¡¡s varies ln palatabltty b€cause: al it b usualy only palatable whg¡ yomg or reshooling. their grorür or hane been rcmoved b¡ ¡t b rJsrJdV qrly græed rrrtrør dr€r more palatable specjæ frnish the palatablo sÞge of from the area bY grazing. cl lt ls r.sualfy rrot grazed significanüy, but may occæionally be lighüy $azed' Rating 3) This spe ¡s ¡ decroasef ol 3. Cafegory A: specles rufflclently lrcquont to support statlsücal analysls but wülch falled to toglstor lncrcasor cp€cleo. Category B: rpcctec too ¡carcc to onable a cattle efbct to bc revealed, ovon lf ono.:dsþd. 4. Dlstlbutlon of frequencles ln be¡t quadrats. 58 My observations on this species at Hyde Dam and Tucker's Bore indicated that it was normally only grazed during dry periods when heavy grazing can occur. However, I think the reason this species did not show an increase in frequency from Hyde Dam was because the grazing at th¡s site was not heavy enough to remove it from the gilgais. The only area along the traverse which showed that A. pectinatahad been heavily grazed was close to the Dam, but the numbers of individuals did not appear to have been reduced. However at Tucker's Bore A. pectinafa had declined near the bore and the plants remaining were heavily grazed. Erag ro sti s setlf o I i a (neverfai l) Eragrostis setifotiadecreased from Hyde Dam (App. 1.4). But at Tucker's Bore there was no trend along traverse 1 (App. 1.5) but an increasing trend away from Tucker's Bore along traverse 2 (App. 1.6). I had not expected E. setifoliato show a decreasing trend at either Hyde Dam or Tucker's Bore because at both of these locations I could not find any E. setifolia which had been grazed. As a result I suspected that it was unpalatable to caüle at both of these locations. However, at Hyde Dam my observations did indicate that there was a greater abundance of E setifolia closer to the dam. Panicum decomposltum (native millet) Panicum decompositum was not abundant at Hyde Dam. Reconnaissance there made me suspect that P. decompositum was in abnormally low numbers for an Oodnadatta saltbush tableland. This was later supported by this traverse (App. 1.7) which showed that although this species is usually one of the most dominant on this range component it was in fact one of the least abundant at Hyde Dam, only reaching a maximum frequency of 0.15%. I subsequently concluded this was caused by heavy horse stocking in years past. This was supported by an obvious cross fence difference 59 identified from aerial photographs taken in 1982, a contrast which was hard to see on the ground. At Hyde Dam the greatest abundance of this species was in the sacrifice area up to about 1km from the dam and then in scattered pockets till about 3.5km. Reasons for this might be: 1) the horses and cattle had not been relying on the dam for water but had instead been drinking from gilgais, because of winter rainfall earlier in the year and quite recently. This would altow the stock to graze the better vegetation further from the dam, atlowing the remaining remnant vegetation at the dam time to flower thereby possibly becoming unpatatable (see Chapter 1 1); 2) similarity to South African Panicum spp. which are responsive to nitrogen and increase around watering points where livestock dung and urine concentration. lt is possible P. decomposítum responds in similar situations (M. Friedel, CSIRO Division of Wildlife and Ecology, Alice Springs, pers. comm.); 3) stock disturbance around the dam suited the growth of P' decompositumiandlor 4) P. decompositum nalurally decreases away from Hyde Dam. At Tucker's Bore both traverses (App. 1.8 & 1.9) showed there was a decrease in the frequency ol P. decompositumto about 1.Skm but from 2km distant the frequency increased. However, this was not supported by statistical analysis. My observations at both Hyde Dam and Tucker's Bore indicated that this species was palatable to cattle. Thus the trend from Hyde Dam was counter to my own observations and the literature reports (see Chapter 11). I expected that after horse and cattle grazing this species would increase in frequency with increasing distance from Hyde Dam. Spo robol u s acti n o clad u s (katoora) Sporobotus actinoctadus w€ts absent within 3km of Hyde Dam; it first occurred at 3.5km distant and rose dramatically in abundance maintaining that level for the rest 60 of the traverse (App. 1.10). However, traverse 1 from Tucker's Bore (App. 1-11) showed there was no trend and S. actinocladus was not recorded regularly enough along Traverse 2lo warrant statistical analysis. At Hyde Dam S. actinoctadus had been grazed to ground level to about 3.5km from the dam. lnspection of gilgais at different distances from water showed that S. it was usually ac,tinoctaduswas removed from gilgais heavily utilised by cattle although abundant in lightly grazed gilgais. At Tucker's Bore this species was in quite high numbers within about 1km of water, and fluctuated throughout the traverse. Thus no trend was detected. However, Hyde I had expec{ed that because the stocking at Tucker's Bore was heavier than at Dam S. actinocladus would increase from Tucker's Bore' Mulga and horse mulga on deep red sands and dunes Acacia tetragonophylla (dead finish) Acacia tetragonophytta increased in frequency with increasing distance from Boundary Bore (App.1.'12). However, from Wyjundi Bore (App' 1'13) there was no trend for this species, probably because of the light grazing there. My observations from Boundary and Wyjundi Bores indicated this species was not palatable to cattle except occasionally when young or when growing in the immediate vicinitY of water. The reason this species is behaving as a decreaser at Boundary Bore can only be speculated. lt is possible that the juveniles close to the bore have been heavily grazed or trampled out by cattle, but this seems unlikely' 61 The raw data for A. tetragonophyttaat Boundary Bore showed that this species was detected very rarely by the traverse, while at Wyjundi Bore it was detected frequently. This indicates that an environmental factor other than cattle grazing such data as soiltype may have influenced the abundance ol A. tetragonophylla. Thus the for this species from Boundary Bore should be treated with scepticism. Ènchytaena tomenfosa (ruby saltbush) At both Wyjundi and Boundary Bore (App. 1.14 & 1.15) there was an increase in the frequency ol E. tomentosawith increased distance from the bore. I had suspected that E tomentosa was a decreaser species as it had been completely removed by grazing in the immediate vicinity of Boundary Bore and was sparse until about 2km. At Wyjundi Bore however, E. tomentosawas only sparse within 1km of the bore. Erag r o sti s eri o pod a (wool lybutt) Eragrostis eríopoda decreased in frequency with increased distance from Wyjundi Bore, until reaching zero at 5.1km which was the traverse end (App. 1 .16); but at Boundary Bore no trend between distance and frequency was detected (App. 1.17\. When recording the frequency data at Boundary Bore I noted that, unlike the sacrifice area around Wyjundi Bore, there was no sign of E. eriopoda. This suggested suppression by heavy cattle grazing. However, at about 500 metres from Boundary Bore E eríopodabecame common but showed signs of being lightly grazed. While at Wyjundi Bore my observations indicated that E. eriopodawas common throughout the traverse and as a result I do not believe the trend obtained at Wyjundi Bore was, due to cattle grazing. 62 Eremophila gilesii (green turkey-bush) (App' Eremophita gitesiiincreased in frequency with distance from Wyjundi Bore frequency 1.18), but at Boundary Bore (App. 1.19) there was no such trend between and distance it , Reasons for this can only be speculated. ll E. gitesiiwas an indicator species at is expected that under heavier grazing pressure it would either mirror its response Wyjundi Bore or, according to the literature (see Chapter 1 1), increase' At Wyjundi Bore E. gitesiiwas well-grazed within 200m of the bore but from then on was not grazed. However, at Boundary Bore it was well grazed within 1km of the bore but was rarely grazed from 2km onward. Eremophi Ia tatrobei (cri mson turkey'bush) Eremophita tatrobei increased dramatically with increased distance from Boundary Bore (App. 1.20). At Wyjundi Bore however, no relationship between frequency and distance from water was detected (App' 1'21)' grazing I conclude that when E. Iatrobeiwas subjected to light or moderate cattle this as at Wyjundi Bore there was little impact on this species. ln fact at Wyjundi Bore growing species was recruiting prolifically as indicated by large numbers of seedlings to about 150m from the bore. The adults of this species had also recovered from the for the impact of stocking which occurred about 2 months before this study, and except Bore individuals at the bore showed little sign of being grazed. However, at Boundary there was little E. tatrobeí recruitment except at a substant¡al distance from the bore E' where seedlings were not exposed to heavy grazing. Within 1km of Boundary Bore tatrobeiwas well grazed but from 2km onward it was rarely grazed. 63 Eriachne aristidea(broad-leaf wanderrie grass) The frequency of Eriachne aristidea was decreasing with increasing distance (App' 1'22J'' from Boundary Bore until it tapered off to zero at 4.9km, the traverse end This species was not encountered at Wyjundi Bore' , At Boundary Bore E aristideaoccurred in greatest abundance relatively close few individuals to the bore or on the station tracks leading to and from the bore. only a remained. showed signs of being grazedbut these had been grazed until only the butts Mai reana geo rg ei (sati ny bluebush) Maireana georgeiincreased in frequency with distance from Boundary Bore (App. 1 .23), but at wyjundi Bore (App . 1.24) no trend was detected. At Boundary Bore M. georgeiwas well grazed to 3.5km from the bore while at Wyjundi Bore it was ungrazed except in the immediate vicinity of the bore. from lightly I therefore propose from comparison of the M. georgeifrequency data grazed wyjundi Bore with the data from Boundary Bore that M. georgeiwas unaffected by light grazing but decreased at Boundary Bore when subjected to heavy stock¡ng. Rhagodia spinescens (thorny saltbush) Rhagodía spínesæns (App. 1.25) increased in frequency with increasing distance from Wyjundi Bore. However, at Boundary Bore there was no relationship between frequency and distance from the bore (App. 1.26). This was unexpected as F. grazed the spinesænswas well grazedwithin 2km of Boundary Bore but was rarely at was same distance from Wyjundi Bore. I therefore presumed that if either of the bòles to show a trend for this species it would have been Boundary Bore because of lts history of heavier stocking. et Solanum eltipticum (velvet potato bush) Solanum ettipticum increased in frequency with distance from lightly stocked Wyjundi Bore (App . 1.27), but at the more heavily stocked Boundary Bore no trend was detected (App. 1.28). Within 500m of Boundary Bore S. ellipticum was well grazed but from 1km onward it was not grazed. However, at Wyjundi Bore there was no indication that S. ellipticum had been grazed at all. I therefore suspect that the trend obtained from Wyjundi Bore is not a true reflection of this species' response to cattle grazing. However, three possible reasons there was an increasing trend are: (1) the further west one travels from Wyjundi Bore there is a change in soiltype which is more conducive to the growth ol S. ellipticum, (2') the etfect of cattle trampling may be more important than was suspected, and (3) the trend from Wyjundi Bore was a chance occurrence. 3.4 DISCUSSION This chapter has dealt with those plant species which showed significant trends in p(x) with distance. However, my observations from two of the traverses indicate that five species which do not show significant trends between p(x) and distance (Table 3'3) might nevertheless have indicator value. These species are Atriplex vesicaria decreasing from Hyde Dam and Tucker's Bore and Acacia aneura (mature), Crotalaria eremaeaand Monachather paradoxa decreasing and Sida ammophila increasing from Boundary Bore. Of the statistically significant species the majority responded in accordance w1h species information available from the literature (see Chapter 11) and from my own observations at the traverse sites. 65 ' At Hyde Dam, there was one exception: Panicum decompositum. ll responded conversely to information available on its response to grazing. The literature and my observations suggested that P. decompositum would decrease in proximity to water because it is palatable to cattle. But both traverses from Tucker's Bore showed there was no change in the frequency ol Panicum decompositum from the Bore. Suggested reasons as to why this has not occurred are discussed in section 3.3.1. From Tucker's Bore there were three significant trends all of which agreed with predictions based on literature reports and my own observations. Only one species, Eragrostis setifolra, was significant at both Hyde Dam and Tucker's Bore but at Hyde Dam it was in greatest numbers near the Dam. At Tucker's Bore contrary to expectations, it was in greatest numbers away from the Bore. Of the statistically significant plant species at Wyjundi Bore Eremophila gilesii and Solanum ettipticum both decreased with proximity to water contrary to reports in the literature and my observations (see Chapter 11) that both species are generally unpalatable to cattle. Of the plant species which were shown to be statistically significant at Wyjundi Bore onty Rhagodia spinescens responded differently at Boundary Bore where it was not statistically significant. This contradicted the literature and my observations (see Chapter 11)which showed that r9. spinescens is of moderate to high palatability to cattle and should therefore have decreased at the more heavily grazed Boundary Bore. At Boundary Bore Acacia tetragonophyllawas the only statistically significant species to respond inversely to the literature and my observations. Of those species which were not statistically significant at Boundary Bore but were significant at Wyjundi 66 Bore, Eremophita gilesii should have increased but instead it showed no response to grazng. The reason why there are discrepancies in the responses of certain species at Boundary Bore and between Wyjundi and Boundary Bores may be due to environmental factors such as soil type. Evidence for this is provided by the presence at Boundary Bore of sand dunes and Eriachne aristidea which was not recorded at Wyjundi Bore. lt is also possible that at Wyjundi Bore, as at Boundary Bore, there are environmental anomalies which could not be detected but which influence the patterning of vegetation in these range components. This might explain the decrease of Eremophita gilesiiand Solanum ellipticum at Wyjundi Bore. My observations in conjunction with the literature (Chapter 1 1) appear to have been more useful during this study for identifying indicator plant species than has the quantitative frequency data. The main reason for this may be because only one traverse was usually undertaken at each bore. Therefore, if there is a contradiction in trend between the same species at different bores, there is no way of determining whether the contradiction is caused by environmental influence or grazing impact. However, even at Tucker's Bore where two traverses were undertaken the results obtained were slightly different. This highlights the variability of vegetation from the same bore when sampled in different directions. Anderson (1971), Noy-Meir (1985) and Pickup (1985) say that vegetation change is often spatially variable even over quite small areas because of the redistribution of water and sediment. Problems have been encountered with the use of traverses. These problems include the minor environmentat variations suspected between the same and similar range components which may influence the response to grazing of the same plant species in ditferent localities. This is highlighted by the difference in response between similar species at Boundary and Wyjundi Bores and Hyde Dam and Tucker's Bore. This problem may be overcome by using a greater number of traverses at each bore 67 (probably three al 1ZO degrees) which should limit the incidence of chance results which may occur on a single traverse. This would also enable differences in results detected between traverses at the same bore to be compared without the effect of major environmental influences. Similar problems of spatial variability with point based data have been hightighted by Friedel (1990), Friedel (1991), Lamacraft et al. (1983) and Pickup (1989). Bastin et al. (1993b) and Pickup (1989) have argued the value of remote sensing on the basis of problems with point based data and claim that analytical procedures can be used to discriminate between seasonal influences and partition tandscape variability to allow the impact of grazing to be identified. Finer stratification of the landscape would have been beneficial, mutivariate analysis could have been used to distinguish site and seasonal influences from grazing impact (Austin, 1981 ; Hacker, 1983; Hacker, 1985; Foran et al., 1986; Wilson, 1 986) but a high degree of landscape stratification is required for reliable results (Wilson, 1986) which could not be achieved in this study. I also only wanted to look at one variate at a time and so the same measurements were not made over time. There was also a problem finding suitable watering points on range components with different grazing histories for statistical comparison. Measurements of more similar areas could have been undertaken using irregular sampling interuals as in Chapler 4. However, this was not possible as the landscape was stratified as much as possible. This method has proved that trends in frequency data can be achieved using traverses. However, results can be unreliable, it is not always possible to find a water point with a heavy stocking history and the method is not time efficient. lt took me one and a half days to complete a traverse Skm in length sampling every 200m. But it may take more than a day to find a watering point with suitably uniform vegetation for sampling. 68 CHAPTER 4 THE USE OF DENSITY A MEASUREMENTS TO DE CONDITION 4.1 INTRODUCTION The measurement of frequency using continuous traverses (Chapter 3) showed that trends in the abundance of species from water could be detected on uniform range components. However, the use of continuous traverses was not time efficient and they are not appropriate in the normal situation where the rangeland displays spatial heterogeneity. Thus the aims of this investigation were to determine indicators of range condition for range components too variable for the use of continuous traverses and secondly, to substantiate indicators identified using other methods. Density measurements of plants and percentage cover measurements of plants, litter and bare ground were sampled at relatively evenly spaced distances from water on three of the major land systems on Todmorden: Oodnadatta, Wooldridge and Coongra. I chose to use percentage cover and density measurements during this study for three reasons. First, because data could not be replicated (because of time and labour constraints and the insufficiency of suitable measurement areas) a method was needed for sampling stock-induced vegetation and land surface changes between sites which 69 would prov¡de detailed data but which could be implemented quickly by one person. This method meets this criterion. Second, because of time and labour constraints it was not possible to measure ground surface changes using continuous traverses (Chapter 3). ln this study the proportion of bare ground and litter were measured using percentage cover. Finally, review of the literature relevant to sampling vegetation change in central Australia and the opinion of scientists I spoke to at CSIRO and the Northern Territory Department of Primary lndustries and Fisheries in Alice Springs was that density and cûver based techniques for sampling vegetation change would be appropriate for this research. Some of the relevant literature is by Jessup (1951) who used density measurements to determine changes in shrub density in southern South Australia because correlation exists between soil type and bush density. Wilson and Tupper (1982) reported that most "attributes of range condition that are of interest centre on qualities emphasised by biomass (e.9. animal production) or cover. There is a need to record vegetation in terms of a measure that is sensitive to recent growth and utilisation". The first is to use density or frequency as the basic measure of the vegetation (Christie, 1978; Foran et al. 1978). Density or cover measurements in chenopod shrublands and perennial tussock grasslands are suitable for measuring changes to vegetation induced by stock because they are not influenced by seasonal variation or contemporary utilisation (Graetz and Ludwig, 1978). For the perennial grass component of the pasture, sampling techniques such as dry weight rank and basal cover were considered but these were rejected. Dry weight rank has been used successfully in central Australian perennial grass pastures (Friedel 70 etel., 1g88a; Friedel and Bastin, 1988) but it was rejected in this study because it was not practical to dry samples and it was not suitable for use with perennial shrubs. Basal cûver is suitable for measuring vegetation change in perennial grasslands (Christie, 1978; Foran et al., 1978) but is unsuitable for other growth forms and it may need a large sample size in arid areas where the basal cover is low (Wilson and Tupper, 1982). 4.2 METHODS 4.2.1 Traverse sifes The traverse sites described below were not used for the frequency work in Chapter 3 because of spatial heterogeneity which did not allow the use of continuous traverses. Oodnadatta saltbush tableland 1: Mt Aggie Dam on Todmorden Station (F¡9.2.1),26km south of the Todmorden homestead, was chosen because it is representative of an Oodnadatta saltbush tableland. The dam was also chosen because ¡ts stock¡ng history was known. Mt Aggie Dam was established in 1968-69 and had a maximum of 400 cattle watering from it at any time during the 1970's. But now a maximum of 150 grown cattle are watered from it at any time (D. Lillecrapp, pers. comm.). ln 1980 Mt Aggie Dam was fenced into Mt Aggie paddock but before this cattle were able to range freely. There are two other watering points located in Mt Aggie paddock, Crows Nest Bank, located 7.5km north west of Mt Aggie Dam and Durbridges Bank, located 7km south west of Mt Aggie Dam. The maximum number of cattle which may water from the three water points is 500 cattle. 71 Miztreana astrotricha I Atriplex vesicaria calcareous flats 2: Moontand Bore established in 1969 is located in Alberga paddock 31.Skm east of the Todmorden homestead (Fig. 2.1). This bore was chosen because the area within at least 9km of it is representative of the Wooldridge land system. This paddock also has an exclosure in it, which it was thought might support results obtained during this study. However, this exclosure has proved to be of limited value for my study. Moonland Bore is not continuously used but is usually used during dry periods or drought. After rain the cattle move to the Alberga river channel where there is better feed. The closest watering point to Moonland Bore is Boundary Bank which is approximately Skm away and is only used after rain. During dry periods a maximum of 100 cattle are watered at Moonland Bore. However, this bore once had a higher maximum stocking rate of 200 cattle (D. Lillecrapp, pers. comm.) which can be seen by past damage to some perennial plants such as M. astrotricha which are usually stunted close to water and have a higher proport¡on of dead stems than do bushes further from water. Saltbush and Mitchell grass plains and plateaux 3: Pyramid Tank was established in 1990 and is located 24km south west of the Todmorden homestead (Fig. 2.1). The tank has a single trough which is supplied with water from a pipe to Mother's Bore. This site was chosen for a traverse because it is representative of the Coongra land system and has a road leading from it which was used during this study as a traverse line. 72 ' At any time a maximum of 150 cattle may use this waterpoint. However, it is only used during dry periods because atter rain the cattle will move to Alberga river (D. Lillecrapp, pers. omm.). The closest watering point to Pyramid Tank is Junction Waterhole which is approximately Skm away but is only used after rain. 4.2.2 Sampling procedure At the watering points used during this investigation samples were taken at a point within 500m of the watering point as this is where cattle impact is at its highest, and then at 2km intervals where possible. The density of perennial plants was measured using ten 10m x 2m quadrats (400m2) (Fig. 4.1) which were placed on either side of a 100m tape (20 quadrats in all). Every perennial plant found growing in a quadrat was counted and recorded to give density of plants at each set distance from the dam. Multi stemmed shrubs were scored as individuals if there was a gap of greater than 30cm between living rooted stems or for grass butts a gap of 30cm between living rooted butts. Percentage cover of plants (canopy cover), bare ground and litter was measured using step pointing (pinhead of 4mm diameter inserted in the sole of the boot), 250 steps along either side of the belt quadrat (500 step points in all) (Fig. 4.1). At each step the presence of litter, bare ground or plant at the point of the step was recorded. Bare ground was defined as anything that was not derived from plant matter, and litter is defined as any dead part of a plant lying on the soil surface. 73 5 paces Step - point 2m 1 2 3 4 5 6 7 I 9 10 20 19 18 17 16 15 14 13 12 11 1 00m 5 paces Step - point Diagram not to scale Fig. 4.1 Belt quadrat and step-point transect used to measure density and percentage cover. 74 ' However, there are problems associated w¡th the measurement of percentage cover which may produce inaccurate data and I took precautions to overcome these. Percentage cover may be biased by subjective sampling by the person undertaking the step pointing i.e. looking at the ground while walking and subconsciously choosing or avoiding certain plants but I practiced to avoid this. With practice an observer learns to take regular and unbiased steps. Another problem with step pointing is the variability between observers (Friedel and Shaw, 1987). To overcome this I undertook all step pointing myself. Modifications to the sampling procedure Oodnadatta saltbush tableland It was otten not possible to take measurements at the intervals (outlined above) precisely because creeklines would otten be present which are not representative of the rest of the Oodnadatta saltbush tableland being measured. Thus samples were taken as close to the sampling interval as possible. Maireana astrotricha I Atriplex vesicaria calcareous flats At Moonland Bore spatial heterogeneity was a problem, similar to that encountered at Mt Aggie Dam except that here the traverse line was interrupted by sand dunes. The range components of M. astrotricha and A. veslcaria are usually fringed by sand dunes and the range component on the other side of the sand dune is not necessarily the same as the previous side. This creates problems when attempting to measure the same range component at set distances. For this reason a particular range component was sampled as close to the 2km interval as possible. Saltbush and Mitchell grass plains and plateaux The same system of laying belt quadrats was used at Pyramid tank, but the sampling interval was 1km instead of 2km up to a distance of 2.9km when there was 75 no sign of cattle grazing. Thus one further belt quadrat was measured at 6km to determine whether any vegetation changes could be detected from 2.9km' Data collection from Pyramid Tank was interrupted by rain and therefore field work was halted for a period of 2 weeks, until the area could be re-visited. Therefore the data for bare ground and litter has not been used, as I considered it was too unreliable for making inferences. But the data obtained for perennial plants was used, because both perennial grasses and A. vesicaria were always visible, due to earlier rain. 4.2.3 Stati sti cal analysi s The computer program Minitab release 7 by Minitab lnc. was used to apply linear regressions to the data to determine whether any trends could be revealed in relationsh¡ps between percentage cover and density with distance from water. The following symbols are used to denote levels of statistical significance: **, ***, NS, P >0.05; *, P 4.3 RESULTS The raw percentage cover and density data are summarised by Appendix 2.1' 2.6. The statistically significant scatterplots of cover and density with distance and the superimposed regressions appear in Figure 4.2-4.6 and the non-significant scatterplots are in Appendtx 2.7 -2.27 . ln addition to statistical analysis I draw on my field notes to ¡nterpret my results 76 Oodnadatta saltbush tableland 5 4 Y = -0,246xs + 0.000249.. X ¡- ã rz = 94.?t c) o C) 2 r o o) (ú c 1 c) t-o 0 ¡ c) o_ 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Distance from Waterpoint (m) Fig.4.2 Percentage canopy cover ol Sporobolus actinocladus from Mt Aggie Dam. 100 80 60 -- 40 cØ o) o 20 0 o 1,000 2,000 3,000 4,OOO 5,000 6,000 7,000 8,000 Distance from WaterPoint (m) Fig. 4.3 Density of Sporobolus actinocladus from Mt Aggie Dam. 77 100 I Y = 90.2"' - 0.00,198.. X r2 = 96.0X 80 o o O 60 o o) (ú 40 c o o o 20 o- 0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 9,000 Distance from Waterpoint (m) Fig. 4.4 Percentage cover of bare ground from Mt Aggie Dam. 78 Maireana astrotricha I Atriplex vesicaria calcareous flats 25 ¡ 20 Y = 4.00is + 0.0O¡89' X L rz = ?O.tX 0) I o 15 O o o, (ú 10 I c I I q) O E L 0) o_ 0 0 1,000 2,000 3,000 4,000 .5,000 6,000 7,000 Distance from Waterpoint (m) Fig. 4.5 Percentage canopy cover of Maireana astrotrichalrom Moonland Bore. 300 250 200 'Ø1¿ 150 c o0) 100 50 0 0 1,000 2,OOO 3,000 4,000 5,000 6,000 7,000 Distance from Waterpoint (m) Fig. 4.6 Density of Maireana astrotríchalrom Moonland Bore 79 4.5.1 Anatysis oî tinear regressions and interpretation of îield notes Oodnadatta saltbush tableland Astrebla pectinata No trend was found for the percentage cover or density ol A. pectinata lrom Mt Aggie Dam (App .2.7 & 2.8). As with the other perennial grasses recorded from Mt Aggie Dam, A. pectinata only occurred as grazed butts within 1.6km of the dam. However, at 3.3km there was a slight increase in both the density and percentage cover ol A. pectinafa which continued to 8.5km. The abundance ol A. pectinata at 5.8km should have been much higher if grazing was the only relevant factor, but for other reasons I cannot explain it was naturally low at that particular site. My observations therefore suggest the abundance ol A. pectinafa may have been increasing from Mt Aggie Dam, but because of environmental variation, linear regression failed to detect a trend. Atriplex nummularia ssp. omissa There was no trend in either percentage cover or density ol A. nummularia ssp. omr'ssa (App. 2.9 & 2.10) from Mt Aggie Dam. This accords with my observations that there was no change in either the size or abundance of this species from the dam, except within 300m of the dam where individuals were slightly smaller. Atriplex vesicaria There was no trend for either percentage cover or density oÍ A. vesicarialrom Mt Aggie Dam (App.2.11&2.12). 80 ' This agrees with my observations; A. vesicaría was not uniformly distributed throughout the Oodnadatta saltbush tableland and appeared to grow in areas of high ground or where ground salinity was higher (evidenced by whitish deposits on the soil surface). Thus, because the Oodnadatta saltbush tableland was undulating, there was a good chance this species would not always be recorded using belt quadrats. However, I believe A. vesicaria was decreasing from Mt Aggie Dam and that inferences about the distribution of this species from the Dam can be made from my observations and from the data at each measurement site. At 300m and 1.6km from Mt Aggie Dam there was evidence that A. vesicaría had once grown in numbers higher than were present during sampling. This was obvious from the remains of dead plants and from the heavy grazing on plants which still remained. At 3.3km and 5.8km from the dam the data from percentage cover and density ol A. vesicaria did not correspond. The measurement of percentage cover failed to detect the presence of A. vesicaria at these sites while density measures did. The possible reasons for this are, I speculate, 1) the low numbers of this species at those sites, 2) the belt quadrat was accidentally situated where A. vesicaría was concentrated e.g. on the edge of a gilgai, 3) the measurement of percentage cover using step-pointing is not as good a measure of vegetation as is density and finally, by chance percentage cover failed to detect the presence of A. vesicaria. At 8.5km, neither the measurement of percentage cover or density showed the presence of A. vesicaria. This had been expected as visual observations had indicated there was no A. vesicaria (living or dead) at those sites. A possible explanation for the decline ol A. vesican,a at some distance from Mt Aggie Dam would have been the presence of another water point near the 81 mêasurement s¡tes. However, the nearest water point to Mt Aggie Dam is 7km in the opposite direction to the beginning of the sampling traverse. Panicum decompositum No trend was detected for the percentage cover or density of P. decompositum from Mt Aggie Dam (App. 2.13 & 2.14). However, my observations indicated that the statistical analysis did not truly reflect the abundance of P. decompositumlrom Mt Aggie Dam, for the following reasons. (1) At 300m from the Dam P. decomposifum was recorded in higher numbers than at 1.6km. But at 300m all individuals present were dry grazed butts and therefore may not have been alive. (2) At 5.8km the number of P. decompositum was greater than for the number ol P. decompositum recorded at 8.5km. But this can be explained by an abnormally dense growth ol P. decompositum at 5.8km and an abnormally low number ol Astrebla pectinata. This I believe, was due to a natural anomaly, favouring the growth of P. decompositum. I therefore believe the abundance of P. decompositum was in reality increasing away from Mt Aggie Dam. Sporobolus actinocladus There was a significant increase in both the percentage cover and density of S. actinocladus from Mt Aggie Dam (Fig. 4.2 & 4.3). My observations agreed with this; S. actinocladus was least abundant immediately surrounding the dam and did not noticeably increase until 3.3km distant. But from 3.3km to the traverse end there was a steady increase in both the percentage cover and density of this species. 82 Bare ground, litter and gibber cover The percentage cover of bare ground decreased statistically from Mt Aggie Dam (Fig. 4.4\ although no trend was detected for the percentage cover of litter (App.2.1s). This corresponded with my observations at these sampling sites, which indicated, that on this range component, bare ground cover increased where grazing pressure is highest i.e. closer to water. Gibber cover was measured at the first site of this traverse but was not measured from then on. lt was obvious from my observations at this site and from other localities that disturbance to the gibber cover is localised round water points or in other areas of high stock concentration and so it was not necessary to measure gibber cover further. I had also known previously from Brendan Lay of the South Australian Department of the Environment and Natural Resources that disturbance of the gibber layer is otten an indication of stock impact and I also believe that the measurement of bare ground and litter is sufficient for this study. These observations also apply to the Saltbush and Mitchell grass plains and plateaux. At Mt Aggie Dam the gibber layer had been removed by trampling to about three hundred metres from Mt Aggie dam and the soil had been exposed, leaving very little vegetation cover. Beyond approximately 300m the gibber layer remained intact, although the vegetation cover remained sparse to about 1km. Maireana astrotricha I Atriplex vesicaria calcareous flats Maireana astrotricha There was an increase in the abundance ol M. astrotricha from Moonland Bore (Fig. 4.5 & 4.6). 83 ' At 100m from the bore the abundance ol M. astrotricha was at its lowest, being the sacrifice area where vegetation was severely grazed and trampled. There was an obvious increase in the abundance ol M. astrotricha from 100m, probably due to the decreasing grazing pressure because of the lower cattle density as cattle fan out. From 2.1km onward the density and percentage cover ol M. astrotricha fluctuated to a distance of 5.4km. At 7km there was a dramatic rise in both the density and percentage cover ol M. astrotricha, which was probably due to cattle not normally grazing that far from the watering point. Bare ground, litter and cryptogam crust There was no change in the percentage cover of either bare ground or litter from Moonland Bore (4pp.2.16 &2.17). This agreed with my personal observations which indicated that, except within 1OOm of the bore where bare ground was highest and inversely litter was lowest, there was no noticeable change in either of these parameters further from the bore. An exception is 1.3km distance where litter was higher than for any other site and bare ground lower. I believe this anomaly was due to the sampling site being nearer to a sand dune than were the other sites. Sand dunes tend to grow a higher proportion of ephemeral and annual plant species than the M. astrotricha flats. Another indicator of stock impact round Moonland Bore observed, was the break up of the soil crust within 200m of the bore from stock trampling. This was similar to other bores on similar range components I initialty sampled cryptogam crust from Moonland Bore but it was in too low numbers to make inferences from i.e. cover estimates were in the order of 1% and 84 cryptogam crusts were not found at all of the sampling sites. However, my observations did indicate that the crusts had been removed round the bore where stocking had been heavy. These observations also apply to the ,4. vesicaria component. Atriplex vesicaria There was no statistical change in either the percentage cover or density ol A. vesicaria from Moonland Bore (App.2.18 &2.19) but, the number of points in these regressions is probably too small to draw any definite conclusions from. Particularly if the 7km point is omitted in each case. However, the statistical result agreed with my observations; there was little change in the abundance of A. vesicaria from Moonland Bore, except within 1.6km where light grazing had occurred. At 1.6km I noted that the site was used regularly by cattle but that grazing of individual plants did not exceed 25/o, even though there were some dead plants. Similarly at 3.0km I recorded that A. vesicaria was either not grazed or was only lightly grazed and that bush death was rare. At 4.6km and 7km there was no obvious cattle grazing on A. vesicaria. It would have been beneficial to have been able to measure A. vesicaria within 500m of the bore, to determine the impact of heavy stocking pressure. But there was no A. vesicariawithin this distance. There was also no A. vesicariawithin 500m of any other bore on this land system on Todmorden. Thus I presume that A. vesicaria is susceptible to heavy cattle grazing. 85 Bare ground and litter There was no trend for either bare ground or litter from Moonland Bore on the Atriptex vesicaría range component (App. 2-20 &2-21\- The data for litter at all of the measurement sites were approximately the same. But the data for bare ground varied dramatically at 4.6km. I believe these differences can be explained by the higher number of ephemeral and annual species at 4.6km, which inftuenced the percentage cover of bare ground. When the percentage cover of ephemeral and annual plants was added to the percentage cover of bare ground for each measurement site, the totals were very similar i.e. 1.6km = 64.6/o,3km = 67"/o,4.6km = 56/" and 7km = 63/". ThUS I COnClUde, that fOr reasons which cannot be explained by me there was a higher proportion of annual and ephemeral plants at 4.6km from Moonland Bore and no trend in bare ground or litter. Sattbush and Mitchell grass plains and plateaux No statistical trend was detected for any of the plants recorded from Pyramid Tank (App. 2.22 - 2.27\. lt was my impression that the plains and plateaux from Pyramid Tank were.in good condition except within 300m of the watering trough. The density of all the perennial plants showed that atter 200m from the trough there was not a large ditference in the density of plants, except at 1.9km where plant productivity was low due to smaller gilgai size. The percentage cover for the same plants also did not show a large ditference in the abundance of plants from Pyramid Tank, except for lower numbers within 200m of the watering trough. This verified my observations at Pyramid Tank that the 86 plains and plateaux had not been heavily grazed, probably because Pyramid Tank was only established in 1990. While this information has limited value it has shown the susceptibility of Atriptex vesícaria to cattle grazing within 200m of the watering trough. lt has also shown thal Panicum decompositum which had been grazed to buüs at 200m from Pyramid Tank was more palatable to cattle than was Astrebla pect¡nata which had not been grazed at 200m. 4.4 DISCUSSION The use of density and percentage cover to measure the change in perennial plants, bare ground and litter from permanent watering points has been shown to provide fairly reliable data on the impact of cattle grazing. The results of the linear regressions usually corresponded with my observations, except when environmental variation and or the status of grazed butts influenced the data i.e. the abundance of Panicum decompositum, Atríplex vesicaría and Astrebla pectinata from Mt Aggie Dam. However, statistical results should be treated with scepticism if only a small number of sites are sampled (Greig-Smith, 1983) as was the situation with A. vesicaria from Moonland bore. The percentage cover and density measurements from the same site usually provided the same statistical result. However, as already mentioned, environmental variation and differences between sampling measures can influence trends when point based data are used as outlined in Chapter 3. Furthermore, Wilson and Tupper (1982) reported error variations of 6.3 lo 21.6/" in cover estimates recorded by 2000 step-points in Atriplex vesicaria communities. There is therefore a need for extensive notes on each sampling site, which can be referred to when analysing the data. 87 . This investigation has identified the following indicators of range condition for their respective range components: (1) Oodnadatta saltbush tableland: Atríplex vesicaia, Sporobolus actinocladus, Astrebla pectinata and Panicum decompositum may decrease following heavy stocking as may gibber cover, while the cover of bare ground may increase. (2\ Maireana astrotricha I Atriplex vesicaria calcareous flats: lollowing heavy stocking, Maireana astrotricha has been shown to decrease and I suspect Atriplex vesicaría does also, but this was not clearly demonstrated. There is also a greater proportion of bare ground, reduced litter cover and breakup of the soil crust closer to water. While cryptogam crusts were not common in the vicinity of Moonland Bore at the time of this study they do occur in similar range components. However, their presence may be reduced by heavy stocking as found by Rogers (1972) and Rogers and Lange (1971). (3) Saltbush and Mitchell grass plains and plateaux: A. vesicaria may decrease, along with Panicum decompositum and Sporobolus actinocladusil heavy grazing is prolonged. By contrasl, Astrebla pectinafa is fairly resilient and may survive heavy stocking. There may also be reduced gibber cover and erosion where stocking has been heavy. 88 CHAPTER 5 THE PALATABILITY A PLANTS 5.1 INTRODUCTION This chapter describes the use of a rapid survey method for determining the palatability and impact of cattle on plants in both uniform and heterogeneous range components. Palatability is defined by Heady (1964) as "plant characteristics or conditions which stimulate a selective response by animals". The issue of palatability is complex and is only briefly explained here. However, the interested reader is referred to Heady (1964) for a more comprehensive discussion. There are three reasons why this was needed. First, it is known that grazing selection is based on the balance of positive factors such as ease of harvesting, sweetness and organic acids, to negative factors such as unpleasant tastes and difficulty in harvesting and to the availability of alternate foods (Arnold, 1981). Hence, a hierarchy of grazing pressure develops which provides shorter or longer periods of rest from grazing for some species (Wilson and Harrington, 1984). Therefore decreaser plant species are often those most palatable to cattle and the increaser species are usually unpalatable to cattle (Heady, 1964; Wilson and Harrington, 1984). Thus, ¡f the palatability of these plants can be determined, it is further strong evidence to confirm indicator plants identified using quadrat based techniques. Traditional measures for sampling vegetation such as quadrats and other point based techniques describe at that time the plant community around water 89 which has resulted from past grazing; I needed to get an understanding of why these changes were occurring. Second, by recording the impact of cattle on plants with distance from watering points it might be possible to identify more stock induced changes to the vegetation, especially if a rapid survey technique could be developed. Finally, it is important to give both pastoralists and other interested groups quantitative data on the palatability of these plants and thus their value to the cattle industry. To meet the above aims I decided that the quickest and most etfective method would be to develop an index which would reflect the impact of cattle grazing on ditferent plant species. As cattle have preferences for particular plant species it was considered that those plants most heavily defoliated would be most palatable to cattle and those least defoliated least palatable. The advantages of such an index is that it would allow rapid survey of large areas without the need for laborious quadrating and it would overcome the problem of environmental variation. Using this index the results obtained would be relatively unbiased because a strict set of guidelines would be followed and I would get a comprehensive knowledge of the vegetation through the close observation required to survey for defoliation. Other authors have also used indexes to describe grazing selection by livestock. For instance Andrew (1986b), researching the selection of plant species by cattle grazing pastures at Katherine, N.T., used a S-point scale of defoliation similarto that used by Pechanec and Pickford (1937), Kruger and Edwards (1972) and Grunow and Rabie (1978). Chippendale (1963a) used six classes of grazing 90 impact to identify the etfects of grazing impact on topfeed in central Australia and Squires (1982) ranked severity of defoliation by cattle on an I point scale in central Australia. 5.2 METHODS The rating scale outlined below is based on that devised by Chippendale (1963a), but modified to record the percentage utilisation of perennial grasses. Sixty four sites were surveyed during late 1991 and up to the middle of 1993. Sites were randomly selected from watering points where cattle had been drinking recently. Only those sites where cattle impact was obvious were surveyed, cattle impact being evidenced from sightings of grazing cattle or the presence of their hoof marks or excreta. Data were collected from each survey site according to a scale of percentage defoliation which is shown in Table 5.1. The percentage defoliation rating for each species at each site with distance from water was averaged to produce the weighted percentage defoliation. The weighted percentage defoliation data were plotted against distance from water. 91 Tàble 5.1 Rating scale (for trees, shrubs and grasses) used when recording the percentage defoliation data. Class of grazlng Descrlpllon of plant Percentage defollallon l8llng 1: No sign of grazing can be detecbd Ungrazed CP/" Êot 2: Rarely grazed For Íees and shrubs: only a few tiPs eaÞn; often a small brandr broken but not apparenüy grazed. For grasses: sÞm and leaves grazed ol flowels eaten. 3: Lþhüygrazed Unevqr grazing of shrub or ùee causing some modification in 2@/" shape; or all soft twigs removed, or certain parE, e.g. fruit remored by grazing. For grassæ: st€m and leavês grazed. 4: Well grazed For teæ and shrubs: most of plant wenly eaten well back witì 5t/" an occasimal branch pulled down. A hedge line ¡s appar€nt on taller ü€€s rþw grazed b he exbnt of animals grazing height For grasses: sÞms grazed down half way. 5: Hævilygrazed For ùe€s and shrubs: availabþ blhge rønored back t) sÞms 8ú/" and ùunk. [Iany branches of lower üees pulled down tr form a spider like etfect. For grasses: sÞms grazed so that stubble remains. 6: Plantdead For trees and shrubs: all branches boken down, obviously 10ú/" dead. ln some cases, a single d€ad stem or tunk is all that remains. Fø grasses: dosely grazed butt is all hat remains. 92 . When sampling a site, the following criteria were observed and actions undertaken: This site was about a 300m radius. Cattte must be present or have been in the area quite recently as indicated by the presence of fresh cattle tracks and/or excreta. For a rating to be given, more than 10 individuals must conform to the rating within that area. More than one rating may be given per site ¡f >10 individuals conform to another rating. Observations must be recorded for all plant species present at the site. A photograph representative of the site was taken. The distance to the closest watering point was recorded. 5.2.1 Sfafistical analysis The computer program Minitab release 7 by Minitab lnc. was used to apply linear regressions to the data to discern trends between weighted percentage defoliation and distance from water. The following symbols are used to denote levels of statistical significance: *, **, ***, NS, P >0.05; P 5.3 RESULTS Fitty two annual and perennial plant species were recorded, but the majority were not common enough to be useful for this study, leaving 16 plant species for study. The raw weighted percentage defoliation data appear in Appendix 3: Section A, and the non-significant scatterplots of weighted percentage defoliation with distance and the superimposed regressions, appear in Appendix 3: Section B, while 93 the significant scatterplots of weighted percentage defoliation with distance and the superimposed regressions appear in Figures 5.1-5.1 1 - 5.3.1 Analysis of tinear regressions showing relationshlp between weighted percentage deîollatlon and distance from water. Only the major points arising from the regressions are provided here Detailed discussion of each species is provided in Chapter 11' Acacia aneura fiuvenile; to 2m): The weighted percentage defoliation of this species significantly decreased from water (Fig. 5.1). The highest defol¡ation i.e. 80% occurred within 1.Skm of water but fell dramatically from 2km onward, generally not rising above 2O%. This indicated that juvenile mulga was not usually palatable to cattle except within 1.Skm of water when heavy grazing can occur. Acacia aneura (mature above 2m): The weighted percentage defoliation of mature mulga decreased from water (Fig. 5.2). Within 2km of water defoliation was severe, reaching 9O/o. However, beyond 2km from water adult mulga remained palatable to cattle but was not usually defoliated more lhan 40/.. From Skm onward this plant was normally only lightly grazed by cattle, as defoliation generally did not exceed 20%. Acacia tetragonophylla: There was no significant trend from water (App. 3.1), but at the watering point it was defoliated up to 50% and further away it usually did not exceed 1O%. This indicated that A. tetragonophylla was predominantly unpalatable to cattle. However, the range (App. 3A) suggests that the 0 values have had leverage on the weighted percentage defoliation and that A. tetragonophyllais more palatable than statistical analysis suggests. 94 c 100 .Fo Y = 62,8"'- 0.0106"'X (ú r2 = 63.?f := I rt-o 80 I oc) 0) o) 60 (ú F 0)o 40 ot- o- 'rc 20 c) -c I o, l¡t 'õ 0 II = 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 Distance From Watering Point (m) Fig. 5.1 Weighted percentage defoliation of Acacía aneura (juvenile) from water. c 100 .9 I (ú ,l .t4.2... = _ o.olo9... x Þ80 cz = 72.4/, oc) o60 g(,J I 640 Ë Lo a) r I o- zo I !I lr Ëoq) 0 1,000 2,000 4, = 3,000 000 5,000 6,000 Distance From Watering Point (m) Fig. 5.2 Weighted percentage defoliation of Acacia aneura (mature) from water. 95 c 1oo o Y = ?3.¿1"'- 0.00818'X (õ T 12 = 48.2x 880 ¡ oc) o60 g()) I o640 oL o- 20 Ð 0) I Ëo 0) 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 9,000 = Distance From Watering Point (m) Fig. 5.3 Weighted percentage defoliation of Atriplex vesicaria from water c 100 o II .g I 80 t = 40.1. - O.OtO1q. õ r. X 0) = 46.?x o I I o 60 o) CÚ c 40 0) I I C) q) o- 20 I ! 0) T -c I .q) 0 o) 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 = Distance From Watering Point (m) Fig. 5.4 Weighted percentage defoliation of Enchylaena tomentosa from water. 96 c o 100 (ú := i{-o 80 oo (I) o) 60 (ú c o(¡) 40 o o- E 20 o -c o) 'õ 0 = 0 1,000 2,000 3,000 4,000 5,000 6,000 Distance From Watering Point (m) Fig. 5.5 Weighted percentage defoliation of Eragrostis eriopoda from water. 100 c o .Ë 80 Y = 18.8' - 0.00366. x õ 12 = 3¿l .0x o600) o ct) (ú I 640o o o- 20 Þ I o I -c O)^ I rrlrr I o v 2,000 3,000 4,ooo 5,000 6,000 7,000 = o 1,000 Distance From Watering Point (m) Fig. 5.6 Weighted percentage defoliation of Eremophila gilesiifrom water 97 100 a- o Y 45.6". .g 80 = - O.OoS9S. X õ rz = 32.?x oo o 60 o, I (ú +) I c 40 o o o- õ 20 o (- .9) 0 II 0) 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 = Distance From Watering Point (m) Fig. 5.7 Weighted percentage defoliation of Eremophila latrobeifrom water. 1oo co (ú õ80 oo o60 sC') 640() L o-0) -o 20 --o0) 'o) 3 0 1,000 2,000 3,000 4,000 5,000 6,000 Distance From Watering Point (m) Fig. 5.8 Weighted percentage defoliation of Maireana astrotricha from water 98 100 c o 90 (ú Y = 67.8"' - 0.0084?... X := 80 r¿ = 68.5t o oq) 70 c) 60 o) T (ú I I c 50 o o 40 t- I G) o- 30 I ic 0) 20 -c .o) 10 I 0) I 0 ..2,000 = 0 1,000 3,000 4,000 5,000 6,000 7,ooo Distance From Watering Point (m) Fig. 5.9 Weighted percentage defoliation of Rhagodia spinescens from water. c 100 .Fo .q 80 Y = 12.8" - 0.00226' x õ 12 = 34,77 oc) 0) 60 O) (ú c c) 40 O I 0) o- 20 ! c) T I 0 'õo, 0 1,000 2,000 3,000 4,000 5,000' 6,000 Distance From Watering Point (m) Fig. 5.1 0 Weighted percentage defoliation of Senna artemisioides ssp. artemisioides from water. 99 100 c '{=o .g 80 Y = 24 0.004{6"' X õ cz = 72.3/ q) o 60 c) o) (ú c 40 0) Lo c) I CL E 20 c) I I -c t .g) 0 c) 5,000 6,000 = 0 1,OOO 2,000 3,000 4,000 Distance From Watering Point (m) Fig.5.11 Weighted percentage defoliation of Solanum ellipticum from water Atriptex vesicaria: The weighted percentage defoliation of this species decreased statistically from water (Fig. 5.3), although the degree of grazing impact was highly variable, fluctuating dramatically to 8.5km. Within 2km of water grazing impact was highest, ranging from 90% at 0.5km lo 40o/" at 1.5km. Atriplex nummulana ssp. omissa: No significant trend was found for this species (App.3.2). The highest defoliation occurred at 0.5km and 1.Skm from waterwhere weighted percentage defoliation reached approximately 60%. But from 2.5km onward defoliation was low and did not exceed 2O%. Enchytaena tomentosa: Defoliation oÍ E. tomentosa significantly decreased from water (Fig. 5.a). Within half a kilometre of water this species suffered intense grazing pressure of up to 90% and it was moderately to heavily grazed up to 4.5km. But from 4.5km it was only lightly grazed (<20% defoliation). 100 .{1./ Eragrostis eriopoda: Defoliation of this species significantly (Fig. 5.5). lt was highly palatable to cattle within 3km of water but was grazedto 6km as defoliation did not exceed20%. Eremophila gilesli: There was a significant decrease in weighted percentage defoliation from water (Fig.5.6) even though E. gilesiiwas generally unpalatable to cattle. However, at watering points it was defoliated up to 45%. After 0.5km it was either not grazed or was only lightly defoliated. Eremophila latobei= There was a significant decrease in defoliation from water (Fig. 5.7). The most intense grazing occurred within 3km of water, when defoliation otten reached 35%. However, within Skm of water E. latrobeiwas well defoliated (up lo 45% at Skm). Eriachne helmsii (Mature): No trend was detected (App. 3.3), because E helmsii was unpalatable to cattle and uneaten, except right at watering points where it was defoliated up to 8O%. Maireana astrotrichar. Defoliation significantly decreased from water (Fig. 5.8). The heaviest grazing impact occurred within 2km of water where percentage defoliation ranged from between 90% at the watering point to 50% 3km from water. However, by 4km, grazing impact had dramatically declined and did not reach more than 35%. Maireana georgelz No significant trend was detected (App. 3.4) even though M. georgeíwas palatable to cattle within 6km of water, when defoliation occasionally reached 65o/". This might indicate that no trend was detected because M. georgei was consistently defoliated along the whole gradient. Monachather paradoxa: No trend was detected (App. 3.5) even though it was eaten. lt was heavily defoliated within 2.5km of water and was lightly to heavily defoliated up to 6km from water. 101 Rhagodia spinescens: Defoliation significantly decreased from water (F¡9. 5.9). The greatest grazing impact occurred within 1km of water, when the weighted percentage defoliation was up to 80%. From 1km onward the weighted percentage defoliation was about 50% to a distance of Skm. But after Skm defoliation was light and did not exceed 15%. Senna artemisioides ssp. artemisioides: There was a decrease in defoliation from water (Fig.5.10) even though this subspecies was only lightly grazed i.e. defoliation did not exceed 1C'/o, except at the watering point where weighted percentage defoliation was approximately 30%. Solanum ellipticum: There was a decrease in defoliation from water (Fig.5.11). However, the weighted percentage defoliation data showed that S. ellipticum is largely unpalatable to cattle except within 3km of water, when it was grazed up to 23%. 5.5 DISCUSSION This rapid survey method proved useful for quickly and efficiently summarising visual observations made in the field which could not be expressed using quadrat-based sampling techniques. However, there was otten much variability in the range of values recorded for each distance from water (App. 3: Section A) but when converted to weighted percentage defoliation these values in the majority of cases agreed with the literature and my observations on the general palatability of these species. The species which were palatable to cattle all the time i.e. Rhagodia spinescens, Eremophila latrobei, Eragrostis eriopoda and Enchylaena tomentosa or were only palatable during particular seasons i.e. Atríplex vesicaria, Maireana astrotricha, Acacia aneura (mature) and Solanum ellipticum alJ showed significant decreases in weighted percentage defoliation from water. However, Maireana 102 georgei and Monachather paradoxa which are also palatable to cattle, showed no trend from water. This was expected lor Monachather paradoxa and Maíreana georgeibecause they were both consistently defoliated from water. Three unpalatable species showed significant decreases in weighted percentage defoliation from water i.e. Acacia aneura (juvenile), Eremophila gilesii and Senna artemisíoides ssp. artemisíoides. This was ditferent from the other unpalatable species i.e. Acacia tetragonophylla, Atriplex nummularia ssp. omrssa and Eriachne helmsii which showed no trend. I believe these three inconsistencies were caused by the dry conditions which were experienced during collection of their percentage defoliation data. The dry conditions meant that plants normally not palatable to cattle were grazed. There are three problems associated with the use of this rapid survey method for determining the palatability of plants; (1) The preference of cattle for some plants changes with season, availability of other plants, habitat and topography (Heady, 1964; Wilson and Harrington, 1984) or for no apparent reason. Thus observations recorded on the palatability and defoliation of a particular plant at one location and season may be different at the same location during a different season i.e. Acacia aneura (juvenile). However, this spatial variation may be reduced by observing defoliation for a particular species over a range of seasons and grazing conditions. (2) lt was not always possible to find cattle grazing at distances sampled across the piosphere range. Thus there are gaps in the distances from water 103 for some plants, which could only be overcome by spending more time sampling. (3) Zero values recorded for weighted percentage defoliation may have high leverage on trends detected for some plants i.e. Acacia tetragonophylla, Eremophila gilesii, Eriachne helmsiiand Senna artemísiordes ssp. artemisioides. 104 SECTION C: SUPPLEMENTARY METHODS FOR DATA GATHERING CHAPTER 6 USE OF EXCLOSURES 6.1 ¡NTRODUCTION I erected four exclosures on Todmorden Station. These exclosures were built with the aim of documenting cattle preference for perennial plants and the recovery of these plants following rain. Exclosures provide important information on the effects of grazing which can not be obtained as effectively by any other technique. They not only provide objective data but also visual comparison of grazing impact in the adjacent grazed rangeland. Exclosures have been established in South Australia since the 1920's but until recently only one set existed in the Marla Oodnadatta soil board district of far northern South Australia. This set was built at Dalhousie Springs on Mt Dare Station (Dalhousie lease) in 1981 by Brendan Lay to monitor feral animal impact. Following eighteen months of monitoring Brendan found that feral animals were having an adverse impact on the vegetation round the springs and subsequently the Dalhousie lease was acquired by the South Australian Government and converted into Witjira National Park. A program of feral animal control was then implemented (8. Lay, pers. comm.). Whilst the aim was to have my four exclosures provide information for this study they will also be reference areas for the lessees of Todmorden Station and have a continuing role as part of the exclosure network of the South Australian Department of Environment and Natural Resources. The exclosure network was 105 established in response to section 44 of the South Australian Pastoral Land Management and Conservation Act (1989) which declares that the pastoral board may set aside specific areas of pastoral land as reference areas for evaluating the etfect of stock grazing. The network consists of a data base maintained by the South Australian Department of Environment and Natural Resources which records data relating to all monitored exclosures throughout South Australia. The network records information dating back to 1974 when Brendan Lay first built two exclosures on Cordillo Downs Station, one on Bon Bon Station and one on Parakylia Station which are st¡ll being monitored. This system of exctosures has been standardised and all future exclosures erected in South Australia will consist of two or three fifty x fifty metre plots depending on the presence of rabbits similar to those described in the exclosure layout and data collection section of this chapter. The use of exclosures to document vegetation change is highly thought of by many rangeland researchers. For example, Michalk and Norton (1980) said that the most direct way to determine the potential of a site is to compare the vegetat¡on and soil attributes with exclosures of the same site that have not been grazed. Exclosures also provide pastoralists with information on the kinds and amounts of species that can be expected when pastures are protected from grazing; conversely, exclosures demonstrate forage preferences of livestock. ln Australia, the following researchers have shown the usefulness of exclosures. Hall et al. (1964) showed that a badly ovet gtazed saltbush community at Koonamore in South Australia partially recovered with some regeneration of Atriplex and Senna species atter 36 years of exclosure. Williams (1969,1970) studied the impact of three levels of grazing pressure and exclosure on a Danthonia grassland. He was able to delineate species which benefited from exclosure and 106 those which increased under ditferent grazing levels. Foran et al. (1982) exclosed three central Australian vegetation types grazed by beef cattle for three years and found that grazing should continue at present stock¡ng levels because no deleterious effects could be found. Other authors stress the importance of exclosures for assessing range condition, for rangeland generally e.g. Buttery (1960), Cliff, (1971), Van Leeuwen & Van der Maarel (1971), Howes (1974), Leigh (1974), Lendon & Lamacraft (1976), Zeevalking & Fresco (1977), Hobbs & Grace (1981), Foran (1986), Holm et al. (1e87). ln contrast other authors have criticised the use of exclosures. Here are some of the cr¡tic¡sms. 1 Vegetation excluded from grazing may become moribound thus not representing areas subjected to disturbance by fire and grazing use (Wilson, 1984). Exclosure can also lead to lower seed production in some grasses i.e. Mitchell grass (Groves and Williams, 1981;Orr and Evenson,1991). 2. Exclosures are usually small in area and are selected to represent specific range components. However, within a specific range component there is natural variation and disturbance caused by patch grazing. Thus exclosures otten do not reflect grazing patterns as a whole (Valamanesh, 1ee4). 3. Exclosures are generally established in areas thought to be pristine or representing a climax state and hence reflect the ideal state of the vegetation before the impact of stock (Laycock, 1975). However, 107 vegetation commun¡ties are dynamic (Austin, 1981) because they are continually influenced by disturbances such as climatic change, fire, drought and insects (Noble and Slatyer, 1980). Vegetation may appear to be stable over long periods, but infrequent events such as drought or wet periods may have determined the vegetation composition (Westoby, 1979, 1980). Hence, the original un-grazed vegetation which is used as a benchmark may not be reliable for estimating changes in range condition caused by grazing. 4. Native herbivores which should be considered part of the natural grazing regime are sometimes excluded by exclosures (A. Valamanesh, University of Adelaide Ph.D. student researching the value of exclosures, pers. comm.). 6.2 EXCLOSURE SITES AND METHODS 6.2.1 Selection of exclosure sites A site selected for an exclosure had to be representative of one of the four major land systems of the region because my budget would only allow for four exclosures. However, because many of the land systems have plant species in common it was possible to build exclosures to encompass most of the key perennial plants growing on all the land systems. All the exclosures were located between 1km and 2.5km from a permanent water¡ng point, close enough to register high grazing pressure, but sufficiently distant to avoid the heavily grazed and extreme disturbance of the inner piosphere. Exclosure sites were located near bores which had known grazing histories so grazing impact observed at the exclosures could be related to stocking rates. lt was 108 also important to select water points which had cattle grazing from them at the time the exclosures were built. On the Wooldridge land system, which is seasonally grazed by rabbits, the exclosure was built near a large rabbit warren to assess the impact of rabbit grazing. At the time of buitding the exclosure, rabbit impact in the area was heavy (e.9. low grazed plant cover, ringbarking of shrubs and shearing of plant tips characteristic of rabbit grazing). 6.2.2 Exclosure sifes The location of exclosure sites on Todmorden Station is shown in Figure 2.1. Maireana astrotricha I Atriplex vesicaria calcareous flats 1: Moonland exclosure consists of a control, cattle proof and cattle and rabbit proof plot built in August 1991, 2.2km east of Moonland Bore, encompassing part of a sand dune and a low bluebush Maireana astrotricha shrubland, in an endeavour to embrace both range components. Mulga and horse mulga on deep red sands and dunes 2: Wyjundi exclosure consists of a control and cattle proof plot built in September 1991 ,2.2km west of Wyjundi Bore. This site is representative of a Mulga perennial grass woodland which dominates much of the northern half of Todmorden Station. Atrlplex vesicaria and Asfrebla pectinafa plains and plateaux 3: Pyramid Tank exclosure consists of a control and cattle proof plot built in March 1992, 1.9km south of Pyramid Tank. lt is representative of a large proportion of the Coongra land system, and also of the Oodnadatta land system due to there being perennial plant species in common. 109 North Neales flood plain 4: Adelaide Yard exclosure consists of a control and cattle proof plot built in March 1992, TOOm from Adelaide Dam. lt is representative of the North Neales flood plain on the Oodnadatta land system. The importance of this range component is that it is used extensively for cattle grazing on Todmorden and very liüle is known of the changes to the abundance of these predominantly ephemeral plant species when grazed by cattle. While the plant species growing on this flood plain are largely ephemeral and annual there are important perennial plants such as barley Mitchell grass (Astrebla pectinata\, bristly sea-heath (Frankenia serpyllifolia), Oodnadatta saltbush (Atriplex nummulana ssp. omissa), neverfail (Eragrostis setifolia), bladder saltbush (Atriplex vesicaria\ and cotto n-bush (Mai re an a aphyll a). 6.2.3 Exclosure layout and data collection The exclosures consist of two or three 50 x 50m plots (exclosure design used and recommended by the South Australian Department of Environment and Natural Resources) (Fig. 6,2), depending on the presence of rabbits. One of these plots excluded cattle, the other cattle and rabbits, and finally a control, which was not fenced. The intention was to measure the effects of rabbit impact and cattle impact separately by comparing the cattle proof plot with the cattle and rabbit proof plots. The control was a reference plot which showed the effect of normal grazing pressure by cattle, rabbits and other herbivores outside the exclosure. Each 50m plot was subdivided into 5m squares (100 in all) using permanent surveyors'pegs. Within each 5m square the height and identity of every perennial plant was recorded. Step pointing (pinhead of 4mm inserted ln the sole of the boot), 110 View from above a o Cattle & rabbit Cattle proof Control 50m proof plot plot a O 1 00m 50m .Corner marker - Fence ln each 50m plot the height and species of all perennial plants is recorded as well as the cover of plants, litter and bare ground using step - pointing. Fig. 6.2 Exclosure layout 111 ,.ing l OOO steps as recommended by the South Australian Department of the Env¡ronment and Planning was used to record the percentage cover of plants (canopy cover), bare ground and litter in each 50m plot for all of the exclosures and permanent photopoints were established to record changes in vegetation with time. An exception to the above procedure was made for the exclosure built at Adelaide Yard because there was no point in recording the location of the predominantly ephemeral plants and secondly, I believed the pegs might be washed away during flood. Therefore only step pointing was used and photopoints established. The exclosures were measured twice during this study (App. 4) at intervals of one year. The first measurement for Moonland, Wyjundi and Pyramid Tank exclosures was taken during drought and the second after drought-breaking rains. 6.3 RESULTS Results recorded from the exclosures are contained within Appendix 4 I have not appl¡ed statistical analysis to the data. Multivariate analysis was considered but rejected for reasons outlined in Chapter 3 and the period over which the measurements were made was insufficient to record significant changes. Most importantly, during this study there was no cattle grazing at three exclosures (Wyjundi, Pyramid Tank and Moonland) because the cattle were moved shortly after they had been built, as a result of drought breaking rains at the end of 1991. This meant cattle were either not fattened in paddocks where there were exclosures or that cattle drank from watercourses instead of from the bores near where exclosures were located. This situation had not changed by the beginning of writing this.thesis in September 1993. Hence the different exclosure treatments only show the response of vegetation to drought breaking rains, not the effect of cattle grazing. 112 At Moonland exclosure there has been little change in the percentage canopy cover and density of perennial plants (App. 4.1 & 4.5) except for A. vesicaria and possibly Senna spp. and Acacia aneura. ln the rabbit and cattle proof plot there was a decrease in the density of six species and an increase in three, in the control plot there was a decrease in the density of four species and an increase in five and in the cattle proof plot there was a decrease in the density of six species and an increase in three. Overall there has been a minor decrease in the total density, but this does not appear to be due to cattle or rabbit grazing but more likely due to drought. This is because the highest number of reductions of perennials occurred in the two fenced plots where there was no sign of rabbit or cattle grazing or of any other herbivore having an impact. Secondly, many of the species which showed density decreases with the exception ol A. vesicaria are unpalatable and therefore are less likely to be influenced by grazing. Those plants which increased in density are those generally referred to as short lived perennial plants i.e. Ptitotus obovatus, Crotalaria eremaea and Maireana georgeíor are perennial grasses t.e. Eragrostis dielsíi and Eriachne helmsiiwhich were not detected at the first reading but which rapidly recruited or re-grew after rain. The litter and bare ground data from Moonland exclosure for the control and rabbit proof plot both decreased from reading one. This can be explained by the increased cover of plants after rain. Litter and bare ground data in the cattle proof plot both increased. However, I can not explain this. At Wyjundi exclosure the percentage canopy cover and density of perennial ptants (App. 4.2 &4.6) has predominantly increased in abundance or has stayed the same for both the cattle proof and control plots since the first reading. The exceptions are the percentage cover of E latrobeiwhich decreased by less than 1% in the control plot and unidentified juvenile perennial grasses which decreased by 113 2.3"/" in the cattle proof plot and 2.O% in the control plot. These percentage reductions are considered minor and do not reliably indicate a decrease in these species. However, the density ol Digitaria coenicola decreased by 191 individuals in the control plot and by 6 individuals in the cattle proof plot, while Monachather paradoxa decreased by 173 individuals in the cattle proof plot. These decreases are considered majorwith the exception of D. coenicolain the cattle proof plot. lt is difficult to find an explanation for the decreases other than that the grass butts did not re-grow following rain, even in the absence of grazing. Those plant populations which showed the greatest increase are Eremophila gitesii, Eragrostis eriopoda and Maireana georgei which is shown by the density of these plants. The increase in the populations of perennial plants similar to the other exclosures I believe is not due to the absence of cattle grazing but is due to good rainfall following drought. In the cattle proof plot the percentage cover of bare ground was slightly lower than the first reading which can be explained by the increase in litter. But in the control plot litter was lower than the first reading and bare ground had increased. There is a difference between litter and bare ground between the control and cattle proof plots which cannot be explained but the differences are relatively minor. At Pyramid Tank exclosure nearly every perennial plant species population (App. 4.3 & 4.7) either increased in abundance or remained the same. The exceptions were for the percentage cover ol A. pectinafa which decreased by 0.1% in the control plot and by 0.6% in the cattle proof plot and lor A. vesicaria which decreased by 0.9% in the control plot. However, these decreases are considered too small to be conclusive. Those perennial plant species populations which showed the greatest increase were all the perennial grasses and the density of Atriptex vesicaria. But there was a decrease in litter and an increase in bare ground for both the cattle proof and control plots. The differences between recordings for 114 litter and bare ground are all higher than 15% with the exception of bare ground in the cattle proof plot. The decrease in litter is explained by the high leaf drop of plants during drought in 1991 which increased litter levels. These high litter levels were not as noticeable in 1992 atter good rains because of the increased percentage cover of new plant growth. At Adelaide Yard exclosure there was an increase in litter levels from reading one (App. 4.4). No conclusive inferences can be made about changes in the data for ephemeral plants. Different ephemeral and annual species grow in different seasons and as the two readings were conducted in different seasons these data woutd need to be compared over a longer time period when the same seasons can be compared. Reliable inferences also cannot be made from the data for perennials because the highest percentage cover recordings for these plants were in the order ol2"/" with a large proportion below 1%. There are many reasons why these exclosures failed to provide the results they were intended to achieve. lt ¡s now evident that on a cattle stat¡on the size of Todmorden (7,500 kmz) there are many factors which cannot be controlled by the researcher and are detrimental to the use of exclosures in the short term. These factors include rainfall, inability to control cattle movement and the good rotational grazing techniques practiced by the managers of Todmorden. ln hindsight the only way the use of exclosures could have met the original aims during this study would have been to build a greater number of exclosures in more paddocks. This would increase the likelihood of cattle being stocked in paddocks with exclosures. But while this is theoretically possible it was not practical to build more than four exclosures during this study because of time and budget constraints. tt5 A third reading of the exclosures was planned for 1993 but because no cattle grazing had occurred at any of the exclosures there seemed little point in recording data which would not show cattle grazing impact. Furthermore, at Moonland bore rabbit numbers were apparently substantially reduced by the drought and have subsequently not recovered (D. Lillecrapp, pers. comm.). 6.4 DISCUSSION The most important information gained from these exclosures is the seasonal dynamics of perennial vegetation. A large proportion of the perennial plants in all the exclosures were recorded as dead during drought in 1991 but these same plants were recorded as alive after rain. This is shown most dramatically by the perennial grasses which were often absent or appeared dry, giey and brittle and by Atriplex vesícaría in the Pyramid Tank exclosure which had lost the majority of leaves and the stems appeared dry and black. These symptoms for drought affected A. vesicaria were similar to those described by Osborn et al. (1932), Ratcliffe (1936), and Knowles and Condon (1951). But after rain a high proportion of these perennial grasses and shrubs re-grew with vigour. There was however, a notable loss of A. vesicaria in Moontand exclosure which has been attr¡buted to drought because of the absence of grazing. Other evidence to support A. vesicaria death during drought is provided by Osborn et al. (1932), Ratcliffe (1936), Beadle (1948), Westoby (1979- 80) and Andrew and Lange (1986b). This highlights the seasonal variability of perennial plants on these land systems and the difficulty assessors will face when assessing for range condition especially during dry periods. lf an assessment had been made of any of the exclosure sites at the initiation of this study during drought I believe many of the sites might have been assessed as being in poor range condition because of apparent high plant mortality. But after rain when the plants have re-grown the same sites would have been assessed as being in good range condition. Therefore there 116 is a need to assess sites when possible after effective rains so that a site's full productive potential is expressed (Bastin et al., 1993b; Wilson et al., 1984). For this reason the cross fence comparisons in Chapter 7 and photopoint sites in Chapter 10 were all examined and photographed following good rains. The increases and decreases in perennial plants recorded for al! four exclosures has little meaning at a management level due to the absence of grazing. The duration of data collection was too short to obtain useful information on the impact of grazing for this study. Cover estimates were also usually very low making it difficult to form reliable conclusions on changes to plant species populations for all of the exclosures using step-pointing. Problems with point based estimates have already been discussed in Chapter 3-4. However, height and age structure data collected during this study and in the future may provide valuable information on the susceptibility to grazing of particular age classes. This information can be used by land managers to determine when paddocks should be spelled and by Iand assessors to determine the condition of plant communities. 117 CHAPTER 7 CROSS FENCE COMPAR 7.1 INTRODUCTION The aim of this investigation was to make comparisons across fence lines separat¡ng paddocks with different grazing histories to discover stock induced changes to the vegetation and soil surface. These stock induced changes may be indicators of range condition. As watering points are the main foci for cattle in the arid zone it was expected those paddocks with long-established bores would be the most degraded. The comparison of paddock fencelines is a simple but effective means of discerning this grazing pressure, as recommended by Wilson et al. (1984). 7.2 METHOD Paddock plans showing the location of watering points and fences were used to determine sites where cross fence ditferences were likely to occur, the most likely locations for cross fence differences being where one side of a fence is in close proximity to a water point and the other side considerably further away from its water. Once a cross fence ditference was located by field reconnaissance a list of plant species either side of the fence was noted and any ground surface differences recorded. A photograph showing the cross fence difference was also taken and the distance from water noted. This method detected only three cross fence differences, which are discussed 118 in this chapter. 7.3 RESULTS Cross fence difference I This is an Oodnadatta saltbush tableland between Mt Lucy paddock and Nobte's paddock on Todmorden Station (Fig. 2.1). Photographs (Fig. 7.1-7.3) were taken in May 1993 atter good summer rains. The southern side of the fence (heavily grazed) is approximately 2km from Mt Lucy Bank while the northern side of the fence (lightly grazed) is approximately 7km from Dingo Hole Dam. Comparison of Figures 7.1-7.3 show that on the lightly grazed side of the fence (far from water) the perennial grasses Panicum decompositum, Astrebla pectinata and Sporobotus actinoctadus and the annual grass Eriochloa australiensis remain and are in good condition. On the heavily grazed side of the fence these grasses have all been removed by cattle grazing. Inspection of the vegetation on the heav¡ly grazed side of the fence showed there are also only a few perennial grass butts remaining and so following rain there will be very little perennial grass regeneration. The only perennial shrubs growing on the heavily grazed side of the fence are the moderately palatable Atriptex vesicaria, unpalatable Atriplex nummularia ssp. omissa and Sclerostegia medultosa which showed only light grazing of a few individuals. On the heavily grazed side of the fence the gibber surface has been disturbed and thus the soil surface has been exposed. Annual and ephemeral plants are also largely absent on the heavily grazed side of the fence compared with the lightly grazed side. 119 I ì r-eF' ?'" Fig. 7.1 Fenceline separating Mt Lucy paddock from Noble's paddock. A clear difference exists between the ungrazed vegetation on the northern side of the fence and the heavily grazed vegetation on the southern side of the fence' Fig.7.2 Northern side of the fence separating Mt Lucy paddock from Noble"s paddock. The vegetation remains intact and is in good condition. 120 Flg. 7.3 Southern side of the fence separating Mt Lucy paddock from Noble's paddock. Heavy cattie grazing has occurred and much of the vegetation has been removed. The vegetat¡on remaining is largely unpalatable to cattle. Cross fence dltference 2 This area (F¡g. 7.4) is in Wooldridge land system but has been classified as the Atríplex vesicaria / Astrebta pectinata flats and run-on areas range component described in the description for Oodnadatta tand system because the vegetation and landform are similar. The fenceline separates Reid's paddock and Mt Aggie paddock on Todmorden Station (Fig.2.1)and was photographed in May 1992 atter drought breaking rains. The northern side of the fence (heavily grazed) is within 500m of Horse Hole Bank and the southern side of the fence (lightly grazed) is approximately 1Okm from Crows Nest Bank. 121 On the heavily grazed side of the fence (Fig. 7.4) almost all plants (perennial and ephemeral) have been removed by cattle grazing. The only plants remaining on the northern side are the dead remains of Atriplex vesicaría and Sclerolaena species. On the southern side of the fence there are healthy Atriplex vesicaria and Eremophita species which are moderately palatable to cattle and Sclerolaena species and Acacia tetragonophylla which are largely unpalatable to cattle. This cross fence comparison clearly shows the susceptibility ol Atriplex vesicaría and other perennial plants to cattle grazing on this land system when heavy grazing occurs. Cross fence difference 3 This is between Brownies paddock and one of its holding paddocks on Atriptex vesicaria t Astrebla pectinata flats and run-on areas range component on Hamilton Station (Fig.3.1). The photograph (Fig.7.5) wastaken looking north with east on the right and west on the left side of the fence during October 1993 after good rain. The western side of the fence has been more heavily utilised than the eastern side of the fence because of recent grazing. The western side of the fence is approximately 2km from permanent water while the eastern side of the fence is approximately 2km from Hamilton creek and approximately 8km from Pedirka Bore. But the western side of the fence is in a holding paddock and would therefore be expected to be more heavily utilised. ln this situation the main perennial grass Eragrostis setifolia on the western side of the fence has been grazedto butts, while on the eastern side of the fence the perennial grasses had not been recently grazed. The perennial shrub Atríplex vesicaria has been removed by grazing from both sides of the fence which is 122 Fig.T.4 Fenceline separating Reid's paddock and Mt Aggie paddock on Todmorden Station Fig. 7.5 Cross fence difference between Brownies paddock and one of its holding paddocks on Hamilton Station. 123 conf¡rmed from similar areas of the same land system further from water and from remnants ol Atriplex communities in the paddock, not visible from this photograph. Figure 7.5 is useful because it highlights the resilience ol Eragrostis setifolia to heavy grazing pressure and the susceptibility of Atriplex vesicariato over grazing. 7.4 DlscussloN Cross fence differences were rarely detected during this study. Where they were detected one side of the fence was usuatly within 2km of water and the other side usually further than Skm from water. Cross fence comparisons have proved to be useful during this study in providing supplementary information on the susceptibility of certain perennial plants to cattle grazing. This investigation has shown that Atriplex vesicaria, Eragrostis setifolia, Panicum decompositum, Astrebla pectinata and Sporobolus actinocladus are susceptible to heavy cattle grazing while Atríplex nummularia ssp. omissa, Sclerostegia medutlo.sa and Acacia tetragonophylla which are not palatable to cattle usually survive even in areas of heavy grazing. The comparison of fence lines has also shown that except within 2km of watering points it is difficult to find stock induced differences across fencelines in northern South Australia. However when I visited sheep stat¡ons in southern South Australia cross fence differences were common and were readily distinguishable at distances greater than 2km. There are probably several reasons for this difference between the south and north. Firstly, the size of paddocks in northern South Australia is usually larger than in the south promoting less concentration of stock. 124 Secondly, many fencelines in northern South Australia have only recently been established. On Todmorden Station most fencelines were only established in lgBO-81 during the Tuberculosis and Brucellosis Eradication Campaign and therefore good management practices have not allowed heavy grazing to occur except around watering Points. Thirdly, it is difficult to find water¡ng points within two kilometres of a fence line on Todmorden which this study has shown is usually the maximum distance from water required to show heavy cattle grazing impact. Finalty perennial grasses which are the preferred perennial feed of cattle are highly resilient to cattle grazing and therefore usually re-grow following rain (see Chapter 6), leaving no discernible cross fence difference except where continuous heavy grazing has occurred. 125 CHAPTER 8 rACCltt¡C Pfnerurunl 8.1 INTRODUCTION Perennial grasses are important as either understorey constituents or as the dominant perennial plant species of many of the land systems on Todmorden, but after heavy grazing they are often only present as grazed butts. lt is thus important to be able to determine whether they recover following rain; accordingly I monitored some. Un-grazed grasses were also monitored to determine cattle impact on them. A small number of perennial shrubs were also monitored to determine the impact of cattle on them and whether they re-grow following grazing. 8.2 METHOD Perennial grass tussocks, both grazed and those ungrazed, were monitored during this study. Tussocks inside and outside my exclosures were in¡t¡ally chosen for monitoring so they could be easily re-located and also to help substantiate results obtained from the exclosures about the preference cattle have for particular plant species. Numbered creosoted wooden pegs were used to mark the tussocks which were then photographed using a 35mm camera to provide a permanent photographic record of each plant for future comparison. Grazed tussocks which had re-grown after rain were then re-photographed and identified while in flower (Table 8.1). At the same time the previously ungrazed tussocks, already photographed and identified, were re-photographed if they had 126 been grazed by cattle to illustrate the severity of grazing on them for future monitoring. Other perennial plants were also monitored to follow cattle impac't on them (Table 8.1). These plants were chosen if they showed previous cattle impact or it was known from the literature or local people that they were likely to be palatable to cattle. 8.3 RESULTS The details of each plant appear in Table 8.1. Table 8.1 Monitoring perennial grasses and shrubs in situ. Peg Specles lnitially grazed afler firsl Regrown Y/N Range comPonenl' No Y/N Perennial Gragseg 1 lYtonachatherParadoxa Y Y Ms 2 lvlonachatherParadoxa Y Y Me 3? Y N Ms 4? Y N Ms 5? Y N Ms 6? Y N Ms 7 Eragrostis erioPoda Y Y Ms Y Ms 8 lvbnaùather Paradoxa Y 9 Eragroslis erioPoda Y Y Ms 10? Y Y Ms 11 ? Y N Ms 12? Y N MS 13? Y N Ms P 14 Astre,ble pectinab Y N P 15 Astrebla Pectinab Y N 16 Ast¡ebla Wtinab Y N P 18 Astebla Wtinab Y N P 19? Y N c n? Y N c 21 ? Y N c 2.? Y N c æ? Y N c ? Y N c Table 8.1 continued over Page 127 Table 8.1 continued t Peg Specles lnltlally grazed afler Re-grown Y/N Rango componont No flrsl Y/N 25? Y N c 27 Asuaótarytinaa Y N P æ Astrcblerytinatr Y N P 30 AstrcblerytinaÞ N Y N 3l Aetreblaryünab N Y N 32 Astleblerylinaâ N Y N 33 Astrcblarylinaâ N Y N U Ast€'blarytinaâ N Y N 35 Astreblarytinaâ N Y P 36 Astreblarytinab- N Y P 37 Art"/blarytinab N Y P 38 Eragrostis erioPoda N Y Ms æ lvlonachatherParadoxa Y Y Ms & lvlonachatherParadoxa Y Y Ms 41 lvlonachatherParadoxa Y Y Ms 42 lvbnachatherParadoxa Y Y Ms 43? Y N c 44? Y N c ¡15 ? Y N c ¿16 lvbnachather patadoxa Y Y Ms 47 EragrostiserloPoda N Y Itls 48 lvlonachatherParadoxa N Y Ms 49 EragrostiseioPoda N 7 Ms o 51 ? Y 7 52? Y 7 o 56? Y N c 57? Y N c 58? Y N c Shrube 17 Atriplexvesiæia Y N P â Atriplexvesiøña Y N P æ Atriplexvesiaria Y N P 50 Enclrylaenatomentosa Y Y Ms 53 lvlaireana astotricha Y Y c g ì/laireanaastot¡icha Y Y c 55 l,tlaireana astot¡icha Y Y c 59 Maireana astot¡icha Y Y c ?: This plant cannot be ldentlfied Y/N: Yes or No refers to whether the Plsnt hss ro€rown slnce lt was last photographed. Rangc componentr 1: O - Oodnadatta saltbtsh tableland 2: P = Saltbush and Mitchell grass plairs and plaÞaux 3: C - Ã/lairæna astotíùa I Atiplex vesianía caløteous flaE 4: ils - Mulga and horse mulga on deep red sands and dunes 5:N =Nealesfloodplain 128 8.4 DISCUSSION Some inferences can be made. First, the perennial grasses monitored e.g. Monachalher paradoxa, Eragrostis eriopoda and Astrebla pectinata are all palatable to cattle. That they had been grazed by cattle was assumed by the presence of cattle or their excreta. Secondly, all of the perennial grasses monitored can survive at least one complete defoliation by cattle and re-grow following rain. Of the perennial shrubs monitored Atriplex vesicaría did not re-grow following severe defoliation (individual plants had lost at least 7O/" ol their leaves) during drought. Leigh and Mulham (1971) and Graetz and Wilson (198a) consider that Atriplex vesicariais susceptible to grazing during drought because the plants may be water stressed. However, Enchylaena tomentosa and Maireana astrotricha re-grew following moderate grazing (plants had been defoliated by aO%) and did not appear to have been adversely affected. The use of thís method to monitor perennial plants in the short term is limited by the number of replicates of each plant species which can be monitored and the number of times individuals are defoliated. Because this Masters Degree began near the end of a 2 year drought, perennial grass butts were often difficult to find because they had deteriorated and it was not known whether they were perennial or the remains of annuals and therefore worth monitoring. Subsequently when drought breaking rains did occur the perennial grass butts re-grew but were often not grazed again because regular rain fell throughout the rest of the study enabling cattle to gtaze the more preferred ephemeral and annual plants. As with the exclosures, paddocks which were stocked with cattle at the time this study was began were later de-stocked, which meant the perennial grasses were not re-grazed. Another problem encountered during this investigation was the removal of the wooden pegs by cattle and dingoes. While all of the plants were subsequently re- 129 located the original photograph position was not always relocated because the shape of the plant had changed since the last photograph. 130 CHAPTER 9 nsronrcnl pnoroc 9.1 INTRODUCTION The aim of this study was to detect change in range condition by relocating rangeland scenes in old photographs, and by close examination to identify indicators of these changes. As stocking rates earlier this century were higher than they are today in most cases (D. Lillecrapp, pers. comm.), there are identifiable changes to the vegetation which can likely be attributed to a change in stocking rate. 9.2 METHOD The main source of historical photographs was the Lillecrapp family who have been the Todmorden Station lessees for about thirty years. They were able to supply many photographs dating back to the early 1960's. Other sources of historical photographs included the South Australian Department of the Environment and Natural Resources, South Australian Department of Mines and Energy, and Commonwealth Scientific and lndustr¡a¡ Research Organisation. Scenes in old photographs were relocated from distinguishing land marks and man made structures. Once a scene had been relocated, the significant changes to the perennial vegetation and ground cover were recorded. lnferences were then made about their value as indicators of range condition based on my observations and the lessee's knowledge of stocking history (when known). 131 Six sites were relocated and their locations are shown by Figure 2.1. These sites are discussed below. 9.3 RESULTS AND DISCUSSION 1. Alberga floodplain (Wootdridge land system) This photograph (Fig. 9.1) of the Todmorden homestead and Alberga floodplain was included in this thesis because it highlights the response to reduced grazing of some of the indicator species common to other range components. Comparison of Fig.9.1 (1962) and Fig. 9.2 (1991) shows there has been a major re-growth of vegetation during the past thirty years. The trees directly surrounding the homestead, however, are not representative of the surrounding vegetation as they consist largely of introduced Eucalypfus spp. and Tamarix aphylla (athel pine) which were Planted. During the late 1950's to the 1960's approximately 3000 cattle were watered at the homestead bore at any time (D. Lillecrapp, pers. comm.). lt is evident from the photograph taken in 1962 that this heavy stocking suppressed vegetation growth and severely denuded the landscape. Subsequent reduced stocking over the past 30 years has allowed the vegetation to re-grow and a good vegetation layer now covers once bare ground. From my observations made on similar floodplain areas elsewhere on Todmorden, I propose most of the plant species which originally grew at this location have now re-established themselves. However, from comparison of other areas along the Alberga River it is apparent that Acacia victoriae and Acacia aneura arc now two of the most dominant perennial species growing near the Todmorden homestead and they appear to have increased in abundance. 132 Fig. 9.1 Aerial photograph of the Todmorden homestead and Alberga floodplain (1e62). Flg. 9.2 Aerial photograph of the Todmorden homestead and Alberga floodplain (1ee1 ). 133 2. Alluvial plain (Alberga land system) Appattina yards are located approximately 25km west of the Todmorden homestead (Fig. 2.1) and have been heavily grazed. This site is on an alluvial plain which occurs in Alberga land system and was included in this thesis because it has plants common to the Mulga and horse mulga on deep red sands and dunes range component. Comparison of Fig.9.3 (1962) with Fig.9.4 (1991), Fig.9.5 (1992) and Fig. 9.6 (1993) shows the variability of annual and ephemeral vegetation not only during the last 30 years but also the past 2 years. lnspection of this site in 1991 (Fig. 9.4) during severe drought showed that the palatable perennial grasses, trees and shrubs had been largely removed by grazing. There was also no sign of any annual or ephemeral vegetat¡on. Following heavy rain in 1992 (Fig. 9.5) a dense cover of predominantly unpalatable annuals such as Sísymbrium orientale (hedge mustard) and Brassica tournefortii(wild turnip) grew. However, there was no growth of the annual yellow and white flowered species shown in Fig.9.3 (1962) which could not be identified by the State Herbarium of South Australia. While there has been a decrease in palatable plant species, less palatable perennial species such as Acacia tlgutata and Acacia tetragonophylla have increased in abundance. Figure 9.G shows the same site re-photographed in 1993 and again shows the variability of annual and ephemeral vegetation at this site. The dominant grass in this photograph is Aristida contorta. 134 $ .:+ a*' ,*ùÊ,*.,...-ô, Ð--5,----ñ . --æ-.--*r- !:ti Fig. 9.3 Appattina yards (1962). Fig. 9.4 Appattina yards (1991) 135 Fig. 9.5 Appattina yards (1992). Fig. 9.6 Appattina yards (1993). r36 3. Atriplex vesicaria I Astrebla pectinataflats and run-on areas Parke's yard is located approximately 30km south west of the Todmorden homestead and has a history of heavy grazing. Comparison of Figure 9.7 (1962) with Figure 9.8 (1991) shows there has been no improvement in the condition of the land in this area over the last 30 years' However, because these photographs have been taken directly surrounding a stock yard it is expected the area would be in poor condition. Comparison of these photographs shows there is no substantial change. However, my reconnaissance of this area indicates ¡t is in poor condition, with very little re-growth of palatable plant species and an obvious stock browse line on palatabte perennial plants such as mulga. lt is likely that low shrubland species such as Atriptex vesicaria and Eremophita spp. were once common here but have subsequently been removed by grazing. This area has a heavy stocking history and has occasionally supported large numbers of feral animals such as donkeys and brumbies (D. Lillecrapp, pers. comm.). 4. Atriptex vesicaria I Astrebla pectinataflats and run'on areas Gypsum yards are located approximately 50km south of the Todmorden homestead and have a history of heavy grazing. Figures g.9 and 9.10 show that except for the increase in size of trees either side of the track there has been little change in the vegetation except for the growth of two Acacia tetragonophytlalrees in the foreground. While the stock yards shown in the photographs are no longer used there is another set of new yards and watering point about 300m away which are frequently used. This tends to indicate the unpalatability ol A. tetragonophytta and support my observations it may be an increaser species. 137 Fig. 9.7 Parke's yard (1962). Fig. 9.8 Parke's yard (1991)" 138 Flg. 9.9 Gypsum yards (1962) Flg. 9.10 Gypsum yards after rain in 1991. 139 5. Gibber plain (Wooldridge land system) Gibber plain, approximately 6km south of the Todmorden homestead. This type of gibber plain is not common on Wooldridge land system but is similar to those on Oodnadatta land system. Hence, it has been included in this thesis. Comparison of Figure 9.11 (1963) and Figure 9.12 (1991) shows there has been a minor increase in vegetation during the past 30 years. However, the plant species which have increased are largely unpalatable ephemeral plants dominated by Scterotaena spp. Thus the condition of the land can not be said to have improved. However, my own observations of areas similar to this in other localities show that little vegetation ever grows on these flat gibber plains because gilgais are absent. 6. Mulga and horse mulga on deep red sands and dunes Mulga perennial grass woodland which has been lightly grazed, midway between Alleumba water-hole and the Granite Downs Station boundary. Figures 9.13 - 9.14 show an area of Mulga perennial grass woodland which was burnt in the 1940's and saw the death of almost all perennial vegetation. Subsequentty the vegetation has re-established to its present condition (Fig. 9.15 & e.17). The exact sites where the photographs were originally taken in 1949 and 1g51 could not be found. However, the general area of the photographs is known and a subsequent photopoint site was established in 1991 . 140 Fig. 9.11 Approximately 6km south of the Todmorden homestead (1963) Fig. g.12 Approximately 6km south of the Todmorden homestead after rain in 1991. 141 Flg. 9.10 Mulga perennial grass woodland midway between Alleumba water-hole and the Granite Downs Station Boundary (1949)' I Flg. 9.14 Mulga perennial grass woodland midway between Alleumba water-hole and the Granite Downs Station Boundary (1951)' 142 Fig. 9.15 Mulga perennial grass woodland midway between Alleumba water-hole and the Granite Downs Station Boundary (1991) Fig. 9.16 Mulga perennial grass woodland midway between Alleumba water-hole and the Granite Downs Station Boundary (1992). r43 Fig. g.iZ Mulga perennial grass woodland midway between Alleumba water-hole and the Granite Downs Boundary (1993) Fig. 9.18 Mulga perennial grass woodland on Todmorden Station which has not been burnt in the Past 100 Years 144 Comparison of Figures 9.15 - 9.17 shows the dramatic changes which occur due to seasonal conditions in northern South Australia. Figure 9.15 was taken during drought and the only vegetation present is perennial but Figure 9.16 was taken after good rainfall and shows good cover of ephemeral and annual plants. Figure 9.17 shows the same site taken approximately one year later when all plants have dried off. Comparison of this site with Mulga perennial grass woodland which has not been burnt in the last 100 years (Fig. 9.18) shows that the woodland here is not as dense but my observations suggest that all of the plant species are present and regenerating. However, this is difficult to see from the photographs. This series of photographs highlights the resilience of Mulga perennial grass woodland to fire and the regeneration of the plants following fire. 9.4 CONCLUSIONS This method of identifying stock induced changes from historical photographs is a valuable tool for determining indicators of range condition. The photographs re-located during this study on Todmorden have shown the variability of ephemeral and annual vegetation influenced by change in season. They have also shown there has been very little growth of palatable perennial vegetation in the photographs (except near the Todmorden homestead) following the implementation of lower stocking rates. Possible perennial indicators of range condition identified include Acacia tetragonophylta (Oodnadatta saltbush tableland and Mulga and horse mulga on deep red sands and dunes), Acacía víctoriae, Acacia aneura (Alberga floodplain) and Acacia tigutata (Mulga and horse mulga on deep red sands and dunes) as increasers 145 and Atriplex vesicanþ and Eremophita spp. (Saltbush and Mitchell grass plains and plateaux) as decreasers. While indicators of range condition have been determined there are problems associated with this method. The first problem is locating historical photographs, as many lessees have not kept historical photographs. They have been removed with subsequent change of lessee or they often never existed. Government organisations which have conducted work in the northern rangelands do have photographs but these are usually not labelled sufficiently to allow their re-location. Second, even when old photographs of a lease are obtained it is often impossible to re-tocate the site shown, because they do not have distinguishing landmarks such as hills, water-holes or bores. Third, ¡t is usually difficult to identify the plant species shown in old photographs even when the site can be re-located because the photograph is taken from a distance or the plant otten no longer exists. Fourth, when changes to the tandscape can be identified otten the stocking history of the scene is not known and therefore the landscape changes cannot be related to stocking rate. Fifth, when scenes in photographs can be re-located they otten centre on watering points which usually show heavy stock impact and are not representative of areas further from water. Finally, because of the dramatic visual contrasts caused by seasonal changes in northern South Australia it is often not possible to relate differences shown by 146 photographs to stock impact. Nevertheless, old photographs can be useful and information should be extracted from them where possible. 147 CHAPTER 1 O pnoropolrur smes 10.1 INTRODUCTION The aim of this investigation was to establish photopoint sites in areas where it was obvious that heavy grazing had occurred in the past or might occur in the future. This study was considered to be predominantly long term and to be useful mainly to the South Australian Department of Environment and Natural Resources for monitoring these northern rangelands in the future, as cattle-induced changes to perennial vegetation mainly occur after years of cattle impact. But I also considered that photopoint sites might be useful for documenting seasonal changes to perennial, ephemeral and annual vegetation during this study. photopoints are fixed sites where a photograph is taken. A permanent marker, usually a peg, indicates from where the photograph should be re-taken in subsequent years. A photopoint site (as in this study) may also have an associated permanent belt quadrat from which density and percentage cover measurements of vegetation and ground cover are taken allowing objective comparisons to be made in the future. The first formal photopoints in South Australia were established at Koonamore vegetation reserve during 1926 and continue to be monitored. However, photopoints were notwidely used in South Australia until 1970 when Brendan Lay established 103 photopoints in South Australia's sheep rangelands. ln 1973 the State Government implemented a standardised numbering system to be used by South Australian Government Departments when establishing photopoint sites. Currently photopoints are being established by the South Australian Department of the Environment and Natural Resources in response to Objective a(b) of the South 148 Australian Pastoral Land Management Act (1989) which requires that the condition of pastoral land be monitored. Other rangetand researchers are using and have used photopoint sites to monitor stock impact on rangelands. Hastings and Turner (1965) used photopoints to document the parts played by man and climate in altering the face of the arid southwest of the United States and the arid northwest of Mexico. Currently the Northern Territory Department of Lands, Planning and Environment along with most other Australian Government Departments concerned with rangeland monitoring, is currently establishing photopoints on pastoral properties to monitor stock impact. Morrissey (1976) said short term information is required by pastoralists to assist in seasonal decisions on levels of stock use. Simple observations of fixed sites using photographs for comparison are usually enough for sensible decisions. These observations are best done opportunely in response to seasonal events; features observed may include aspects such as recruitment, plant death, degree of grazing, change in availability of annual herbage and evidence of accelerated erosion (Holm et al., 1987). 10.2 METHODS 10.2.1 Photopoint sife photopoint sites were established in three contexts: 1) where vegetation had not yet been grazed but where grazing might occur in the future, 2) where cattle grazing had already occurred and I wanted to determine whether the vegetation was recovering and 3) at all of the exclosures so that changes to the vegetation in the exctosure plots could be documented photographically. 149 A photopoint site except for those at exclosures consists, in this present study, of a 1.8m tall star dropper, hammered into the ground 50cm, marking the point and height from where the photograph should be taken using a camera with a 50mm lens. A peg 40cm long and 50 x 50mm in diameter 10m from the star dropper is usedto sightthe middle of the photograph (Fig. 10.1) and usually has agraduated height stick placed against it to provide a scale so that changes in plant height during monitoring can be visually estimated. However, height measurements were not recorded. Many photopoint sites were accompanied by a transect (belt quadrat with ten 10 x 2m sub-quadrats) (Fig. 10.1) which was used to determine the density of perennial plants (Tynan, 1990). Two hundred and fifty step points either side of the transect were used to measure the cover of vegetation (canopy cover) (the species were recorded), litter, stone, gravel, lichen or bare ground. This was the photopo¡nt layout for all photopoints except for those at exclosures where a photograph was taken using a 50mm lens from a corner post ¡n each plot. A graduated height stick was not used because it was added to the photopoint procedure after the exclosures were built. Some of the original photopoint sites such as Angle Pole water-hole discussed later in this chapter also did not have a graduated height stick for the same reason. Other information recorded also included all plant species seen at a site; an estimate was made of the crown cover of perennial species; how heavily the vegetat¡on was being grazed and how it was regenerating; the use of the site by stock, native and feral animals; evidence of fire history; and finally of the soil type. 150 o c q) E Ë (ü o VIEW FROM SIDE WHfTE IOP o c .g ( use R6bol ol õL Numbored Dlsc Polnlêd tobor locol molerlol ) a & Rþel or Peg f (l9mm long) (l/ô' hole h bot) _c 1,5 ol 2m robor f læm o U) PHOÍO . POIM SIGHIER PEG PEG ö C) L VIEW FROM ABOVE :l -l0m o ro ó Ø slEP . POIM I o ø =Ø .=(l)=Ø I o-=oo E 9 10 UP -[t 2 3 4 5 6 7 B ed î oa q) lqn. lù1 oF,gd -co-E I 3 l2 DOWN Rebor &* 1B 17. ìó l5 14 il (dõ - l9 L Dlsc I 0 êa oí $u (ú 6 (dEz SIEP . POINT I c ø õ'(Ú õE ' Ologromt nol lo ¡cole 0) ocTE o .É= lL LIJ 10.3 RESULTS AND DISCUSSION During the 2.5 years of this study 28 photopoint sites (including those at the exclosures) were established on Todmorden Station, 14 of which were accompanied by transects. The location and data sheets for all of these sites have been lodged with the south Australian Department of the Environment and Natural Resources and the data has been entered into their data base for future reference. The transects were not re-measured during this study because, after the drought broke, careful examination of these sites showed that in all cases there was no recruitment or death of perennial plants. Thus no data are presented here. However, three photopoints were re-photographed during this study because at these sites there was a noticeable change in the perennial vegetation from the first time the photograph was taken. These are shown here. 1. Wyjundi exclosure is located 2.2km west of Wyjundi Bore (Fig.2.'l\. Figure 10.2 was taken of Wyjundi exclosure during drought in 1991. The same scene (Fig. 10.3) was photographed after drought breaking rains in 1991 . These photographs highlight the response of vegetation on Alberga land system to rainfall. ln the photograph taken during drought all of the perennial plants except mulga have lost most of their leaves. However, following rain the perennial plants e.g. Eremophila latrobei and Eremophita gílesiihave re-grown their leaves and are in good condition. Other plants dominating the photograph after rain are the short lived perennials Maireana georgei and Ptilotus spp. which respond quickly to rainfall. 152 *L Fig. 10.2 View of the centre of the cattle proof plot at wyjundi exclosure during drought (1991). Fig. 10.3 View of the centre of the cattle proof plot at wyjundi exclosure atter rain (1eel). 153 2. Pyramid Tank exclosure is located 1.9km south of Pyramid Tank (Fig. 2.1\. Figures 10.4-10.5 were taken next to Pyramid tank exclosure before and after rain in 1991. These photographs hightight the dramatic response of vegetation on the Atriplex vesicaria and Astrebta pectinafa plains and plateaux to rain. Figure 10.4 shows Atriptex vesicaria with very little or no leaves and the absence of perennial grasses. However, after rain there was a flush of ephemeral and annual plants and perennial grasses such as Panicum decompositum, Sporobolus actinocladus and Astrebta pectinata. The Atriplex vesicaria has also re-grown its leaves. g. Angte Pote water-hole is located approximately 7km north west of Oodnadatta on Todmorden Station (F¡9.2.1). Figures 10.6-10.7 were taken next to Angle Pole water-hole and similarly to the other photographs highlight the response of not only ephemeral and annual plants to rainfall but also perennial plants as well. The Nitraria billardieri(nitre bush) in the foreground appears defoliated in Figure 10.6 but has suffered leaf drop due to the dry conditions, rapidly re-shooting following rain. 10.4 CONCLUSIONS The above series of photographs highlights the importance of photopoints to show seasonal changes in vegetation. Atter rain there is widespread germinat¡on of ephemeral and annual plants but also a marked improvement in the appearance of perennials. These photographs show the resilience of perennial plants to drought and their rapid growth response after rain on the Atriptex vesicaria and Astrebla pectinata 154 Fig. 10.4 A photopoint next to Pyramid Tank exclosure in drought (1991). F Fig. 10.5 A photopo¡nt nen to Pyram¡d Tank exclosure after rain (1991). 155 \ ,n^1 I T tvñ Fig. 10.6 Angle Pote water-hole before rain (1991)' Fig. 10.7 Angle Pole water-hole after rain (1991 ). 156 pla¡ns and plateaux and Mulga and horse mulga on deep red sands and dunes. Not only have the perennial grasses rapidly grown where they were not visible before but the trees and shrubs have sprouted new leaves. This series of photographs shows the problem those using the Land Condition lndex will face in assessing some of the land systems in northern South Australia. During poor seasons there is apparent low perennial plant abundance which may indicate poor range condition to those not experienced with seasons in central Australia. Many of the perennial plants lose the majority of their leaves during drought and often appear dead. Perennial grasses often deteriorate during dry periods and are difficult to find. However, following rain the perennial plants re-grow their leaves and the perennial grasses rapidly re-shoot in large numbers often in areas previously heavily grazed by cattle. 157 ' SECTION D: DERIVED INDICATORS AND CONCLUSIONS CHAPTER 1 1 l¡¡olvlount specle RANGE COMPONENTS S 11.1 EVALUATION OF INDICATOBS The main aims of this thesis were to determine indicators of range condition for use with the Land Condition lndex for assessing the condition of pastoral leases and for use by pastoralists in South Australia's northern cattle rangelands. This workwas reported in Chapters 3to 10 where results are presented and briefly discussed. ln this chapter I have drawn together all this information and I discuss the indicators of range condition, both soil surface properties and for plant species in alphabetical order, for each range component (Section 11.1.2). The more useful indicators are then used to form LCI criteria (Section 11.3). A summary of my findings on soil surface responses (Section 11.1.1) and species responses to grazing (Table 1 1 .1) is as follows: 11.1.1 Soil surtace responses fo grazing Most soil surface indicators discussed below are based on my personal observations made in the field. I had difficulty throughout this study accurately measuring soil indicators because of their non-uniformity e.g. cryptogam crusts and gibber cover. Also many soil surface indicators e.g. erosion are localised at points of heavy stock impact and are obvious anomalies in the environment which can be discerned without objective measurement. 158 ' Dur¡ng the period of field work for this Masters Degree no comprehensive information was available for soil condition assessment. However, recently a rangeland soil condition assessment manual relevant to Australia's rangetands was released but too late for me to incorporate ¡nto my field work. The assessment manual by Tongway (1994) is in part relevant to South Australia's northern rangelands and examines soil surface attributes which indicate plant productive potential without relying on obvious erosion activity. Oodnadatta saltbush tableland These tablelands are resilient to cattle grazing because of the protective gibber layer (Ratcliffe, 1936), but in areas of high cattle and or vehicle impact i.e. near water or on station tracks, the gibber may be disturbed. This exposes the soil to erosion by wind and water which can lead to infilling of the gilgais, scalding, rilling and in extreme cases gully erosion. There is also a reduction in litter cover in areas of heavy grazing but this is more difficult to determine because of the sparseness of vegetation and the influence of season. Atriplex vesicaria lAstrebla pectinata flats and run'on areas Soil surface responses are similar to those for the Oodnadatta saltbush tablelands Saltbush and Mitchell grass plains and plateaux These undulating stony tablelands, similar to the Oodnadatta saltbush tablelands, are highly resilient to cattle grazing. But where cattle grazing or vehicle traffic has been heavy the stone cover can be disturbed, which leaves the soil exposed to erosion by wind and water. ln these degraded areas scalding can occur and in more serious situations large rills and gullies may form. 159 ñ[aireana astrotricha t Atriplex vesicaria calcareous flats When the vegetation has been removed by cattle grazing the calcareous flats are exposed to erosion by wind and water. This leads to a break up of the ground crust closer to water ffongway and Friedel, 1992), which causes scalding and a build up of wind blown sand at the bases of remaining plants. ln extreme situations remaining vegetation is confined to small resilient islands surrounded by wide shallow erosional chan nels. The cryptogam crust may also be disturbed by heavy stocking which can lead to its demise. However, these crusts are not always uniformly distributed and are therefore not a reliable indicator of range condition. Mulga and sandhill wattle sand dunes When vegetation binding the loamy sands has been removed by cattle grazing the sands become susceptibte to w¡nd and water erosion (Morrisey, 1984). This susceptibility is increased by cattle treading which has the effect of churning the usually compact sand, leaving it loose and exposed. ln this exposed state the sand may drilt and scalding may be evident. Water erosion is not as great a problem being mainly confined to hard red earths where infiltration rates are lower (Jacobs, 1 e88). Mulga and horse mulga on deep red sands and dunes Soil surface responses are similar to those for Mulga and sandhill wattle sand dunes. 11 -1.2 Plant indicators A summary of plant indicators is given in Table 11.1. 160 Tabte 11.1 Summary of plant responses to cattle grazing in northern South Australia from the discussions of plant species in this chapter. Sclenüflc name Common namc to Abulilm lnlophilum plains lantern-bush No detectable response b grazing o,P Aaciaaneura (jwenile) mulga lnøæser as jwen¡le (tee b 2m); unPalatabþ i¿ls,Sd Aøcb aneun(maüÍe) mulga Decreass following heavY grazirB i/b,Sd,P Aaciaügulab sandhillwatüe lncreaser as planb are unpelatable and free seeding ]ús,Sd Aæcia tet4gonophylla dead finish lncreaser as planE are unpalatable [,ts,P Asa?/blapectinaâ badey Mitchell grass Decreases when subþcted tc prolonged heary o,P grazing Atiplexvesiæña bladder salbush Decreasss bllorving moderab tc heaw grazing o,P,c Crotalaila eretnaea loosefrowered Decreases bllowing heavy sbcJ Eragrostis eriopoda wællybutt May inilially inøease but decreases follorving i,ls,Sd polonged lnavy grazing Eragrostis ætitolia neverfail lnitial increaser hen decreases if heavy grazing is o,P prolonged Erenophila gilesä gr€€n turkey bush lnøeaser? as it is unpalaùable i/ts ûemqh¡leletobe¡ cr¡mson Urkey bush Decreaser as it is palatrabÞ to cattle tvls,Sd Eønophilamdonøllä fuchsla bush lncreaser as it b unpalatable and colonises degraded iiils s¡tes lvbirænaaphylla cotton-bush lvlay lnøease in degraded salth¡sh commun¡lies or o decræse in sandy areas where stock moúement causes erosion of the rooB lvbhæna astotr¡cha lor bluebush Usuatly only grazed during drought but decreases if c heavy sbcldng is prolonged fulonadtather patadoxa bandicoot grass Decreaser, as it is highly ælatable to cattle i/s Panicum deæmpositum native millet Decreasæ under prolonged heavy grazing o,P m/otus obovetusvat. smokeh¡sh Not a preferred speciæ of caüe but may decrease in irs,Sd obovatus heavily grazed areas Rhagodia spinesæns thorny saltbush Palatable to catüe but only deøeases following iils,Sd polorBed heavy grazing Senna aíemisioides silver cass¡a lncreases because lt is unpalatable and fire promoÞs i,ls,Sd ssp. añemisiokles Its growtr &nna artemisiok!æ punty bush lncreas€r h heavily grazed areas or where here has sd ssp. ñlifolia been fire Sldaannqhila sand sida lnøeaser as plants are genøally unPalatable iís,C Sidafrbulitea pin skla lnøeaser as plants are generally unpalatable l/s,C &lanum elliptiann velvet potab bustr Possibþ inøeaser ln lnavily grazed areas [rs,Sd S p o robol u s acti n ocl ad u s lGtoora Highly palataHe and decreases after ptolonged heavy o,P tR.rrg" componenr 1:O =Oodnadattasalth.,¡shtableland 2:P - Saltbt¡sh and Mitchell grass plains and Plabaux 3: lyls = Mulga a¡rd horse mulga on deep red sands and dunes 4: C = l,/laireana astotrícha I Atriplex vesica¡ia calæteous flals 5: Sd = Mulga and sandhill wattle sand dunes 161 The indicator value of each species is discussed below, in alphabetical order. Abutil o n hal o phi I um (plains lantern'bush) Abutilon halophilum has no value as an indicator of range condition on either the Oodnadaüa saltbush tablelands or Saltbush and Mitchell grass plains and plateaux. lt is effectively ungrazed and occurs patchily across the land-scape. Continuous traverses failed to detect a change in A. halophilum from either Hyde Dam or Tucker's Bore and my observations indicated it was only grazed during dry periods or in close proximity to water when more palatable plants were not available. However, this grazing d¡d not appear to reduce its abundance. ln contrast, Cunningham et al. (1981) regarded this plant as being moderately palatable. My observations accord with those of Cunningham et al. (1981)and Lazarides and Hince (1993) that it is avery robust plant. lts distribution is not uniform, being common in some areas but rare in others. lts abundance appears to be greatly influenced by the amount of water in gilgais; those gilgais which hold water the longest have bigger individuals and more of them. Acacia aneura fiuvenile mulga) Acacia aneura juvenile (trees to 2m) has indicator value as an increaser species in the Mulga and horse mulga on deep red sands and dunes and on the Mulga and sandhill wattle sand dunes in Wooldridge land system. However, of the methods used to detect indicators, continuous traverses showed no change in the frequency ol A. aneura (juvenile) from either Wyjundi or Boundary Bores, but historical photographs showed this species increasing along the Alberga River and palatab¡l¡ty ratings showed it was usually unpalatable to cattle except within 1.Skm of water. 162 However, I have noted that during drought or when growing in close proximity to water grazing can range from light to heavy. lt may also be heavily grazed when growing on land systems where the majority of plants are unpalatable to cattle. Pastoralists I have spoken to say that they have seen areas of juvenile mulga which have been grazed one year but have been ignored in other years. Cattle grazing does not appear to prevent the recruitment of mulga and it otten increases in abundance, except in areas of heavy grazing. Evidence to support these observations is provided by Askew and Mitchell (1978) who reported that the leaves of immature mulga are often covered in a bitter tasting resin making them relatively unpalatable to stock. Burrows (1974\, Pressland (1976) and Rathbone (1983) noted that cattle grazing does not suppress mulga re-grovtrth and it quickly attains a size where it suppresses grass growth. Muir (1992) reported that due to the increaser characteristics of mulga in western New South Wales it can often grow in dense stands and may be considered a woody weed. lt has also become a woody weed in Queensland (Hodgkinson, 1 979). Chippendale and Jephcott (1963) in central Australia and Cunningham et al. (1981) in western New South Wales reported that the palatability of mulga increased with maturity, with young plants largely being ignored by cattle. Once established, young mulga can withstand repeated defoliation (Harrington et al., 1984b). Chippendale (1963a) found juveniles 3-4ft high were usually not grazed by cattle but adults were often heavily grazed. Acacia aneura (mature mulga) Acacia aneura mature (trees over 2m) may decrease following heavy grazing in the Mulga and horse mulga on deep red sands and dunes, Mulga and sandhill wattle sand dunes on Wooldridge tand system and the Saltbush and Mitchell grass 163 pläins and plateaux. Although continuous traverses did not detect any change in the abundance of A. aneura (mature) from either Wyjundi or Boundary Bores, palatability ratings showed that on Todmorden it was palatable to cattle within Skm of water but was generally only defoliated to 40%. My observations indicate it is palatable to cattle during drought but at other times it is only lightly grazed. During drought however, cattle will often break down the lower branches so that they can gain access to the leaves. Everist (1969) and Niven (1983) reported that mulga is a very useful drought fodder because of its abundance and wide distribution. ln central Australia, Chippendale (1963a) and Cunningham et al. (1981), in western New South Wales report thal Acacia aneura is highly palatable to cattle and is regarded as one of the best fodder trees. Not only does mulga vary in palatability with age but there are also different forms of mature mulga which appear to vary in palatability. On Todmorden and Hamilton Stations mulga that has a "Christmas tree" form is less palatable than other mulga types. Askew and Mitchell (1978) and Cunningham et al. (1981) report similar findings and say the various forms of mulga have different palatabilities with some being quite unpalatable. Randell (1992) has recently undertaken work on the taxonomy of Mulga and has revised the major species. She reports that there are many different ecotypes of mulga, many of which share similar characteristics. I therefore suggest that these different ecotypes have traditionally been grouped together by rangeland researchers when they should ideally be treated separately because of their different palatabilities. Mature mulga has limited value as an indicator species on Todmorden except in areas which have been repeatedly heavily grazed and mulga death has resulted. lBt Mature mulga can be used to estimate roughly the availability of other more palatable plant species. My observat¡ons suggest mature mulga is usually only grazed heavily when more palatable plants are not available. Therefore when mature mulga is being grazed it is time to assess stocking rates and possibly reduce stock numbers. Acacia llgulata (sandhill wattle) Acacia tigutata appears to have indicator value as an increaser species in the Mulga and horse mulga on deep red sands and dunes and on the Mulga and sandhill wattle sand dunes. This was supported by the historical photograph at Appattina yards which showed that there had been an increase of this species. However, Chippendale and Jephcott (1963) and my observations from Todmorden, Billa Kalina and Hamilton Stations indicate A. ligulata is not palatable to cattle. lt is also often found growing in areas of heavy grazing and evidence to support its suspected increaser characteristics are provided by Cunningham et al. (1981) and Harrington et al. (1984b) who report it is a quick growing and free seeding plant. Acacia tetragonophylla (dead finish) Acacia tetragonophyllais an increaser species in the Mulga and horse mulga on deep red sands and dunes and Saltbush and Mitchell grass plains and plateaux because of its low palatability and ability to increase in disturbed areas i.e. around bores and stock yards. However, continuous traverses showed there was no change in the frequency ol A. tetragonophylla from Wyjundi Bore but that it was increasing away from Boundary Bore (however this trend was considered to be due to environmental variation and not cattle grazing). This was supported by palatability ratings and cross fence comparison which showed this species was usually not palatable to cattle and remained in areas of heavy grazing. 165 ' My observations on this species agree with those of Chippendale and Jephcott (1963) and Askew and Mitchell (1978) that it is not palatable to cattle except during dry periods when it may be lightly grazed or when growing around water points where heavy grazing can occur. However, while this species may occasionally be well grazed by cattle ¡t is usually only preferentially grazed when young (Chippendale, 1963a). ln contrast Everist (1969) reported it was eaten fairly readily. At Wyjundi Bore, Barney's Bore, Boiler Hole and Parke's Camp Bank on Todmorden Station there is a noticeably higher density of adult A. tetragonophylla compared with areas further away from the watering points where there is only an occasional adult but a similar number of juveniles. Astrebla pectinata (barley Mitchell grass) Astrebta pectinata has value as a decreaser species on the Oodnadatta saltbush tablelands and Saltbush and Mitchell grass plains and plateaux because it can be removed following heavy cattle grazing. This was evidenced from traverses (Chapters 3 & 4) and cross fence comparisons which showed that Asfrebla pectinafa decreased in areas heavily grazed by cattle. This information was supported by the tagging of perennial plants which showed the h¡gh palatability of this species at certain times. My observations on this species indicate it is normally only grazed during dry periods when more-palatable species are not available. ln agreement with Lazarides (1970) and Roberts and Silcock (1982) it appears to be palatable only when the leaves are green, becoming less palatable as they turn brown. My observations also indicate A. pectinata is robust under líght to moderate grazing but as grazing pressure increases density increases and tussock diameter 166 decreases (Hall and Lee, 1980; Orr, 1980) (presumably as the larger tussocks break up) and they are stunted compared with individuals growing in areas of lighter grazing (Orr, 1980). However if subjected to heavy grazing for long periods they will be removed altogether. Established plants are persistent under sheep and cattle grazing (Lazarides, 1970; Roe and Davies, 1985) but are susceptible to heavy grazing as the removal of the lower nodes prevents the plants from responding to light rains (Perry, 1970). ln northern South Australia A. pectinafa is normally confined to gilgais or depressions. This is probably because gilgais are the only sites which reta¡n enough moisture to support this species. A. pectinala reaches its best development between the 250 and 550mm annual rainfall isohyets in regions where rain mainly falls in the summer (Orr, 1975), but the annual rainfall in this region is approximately 150mm. Atriplex nummularia ssp. omissa (Oodnadatta saltbush) Atriptex nummularía ssp. omissa has no value as an indicator of range condition on any of the range components studied. Traverses (Chapters 3 & 4) and palatability ratings did not show a statistical trend for this subspecies, and cross fence compqrisons showed that it is generally unpalatable to cattle. There is no literature available on the palatability or response of this subspecies to graz¡ng. However, my observations at Mt Malua Bank, Mt Aggie and Yardinna on Todmorden Station, Tucker's Bore on Billa Kalina Station and at Hyde Dam on Hamilton Station show that adults of this subspecies are unpalatable to both horses and cattle even during periods of low rainfall. Pastoralists who live in the 167 reg¡on, and other rangeland researchers, agree this subspecies is unpalatable when adult but do not know if it is palatable when juvenile. In areas subjected to heavy stock grazing such as close to watering points this subspecies is often the only perennial plant not to have been removed by grazing and usually appears to be in good condition even though it may be lightly grazed. However, the density of plants close to a watering point may be less than in areas further away. Possible reasons for this are: first, near stock watering points there is little or no recruitment of seedlings because of intense cattle grazing and trampling. Second, the removal of the more palatable plant species from gilgais allows erosion of soil from around the roots to occur. I have observed this in gilgais close to watering points. lf erosion of the gilgai continues soil particles may become mobile and progressively fill in the gilgai (8. Lay, pers. comm). However, by the time this subspecies shows the effect of over grazing most other plant species have already been removed. Therefore this species has no value as an indicator of advancing degradation; its removal would indicate extremely poor condition. During periods of low rainfall it often loses a large proportion of its leaves and care should be taken not to interpret this as being due to stock grazing. tn contrast Condon and Knowles (1952) report that cattle will graze Atríplex nummularia (old man saltbush) heavily at any time, although Moore (1953) and Cunningham et al. (1981)say it is palatable to stockwhen otherforage is in short supply and has declined dramatically in New South Wales due to grazing by cattle and sheep. 168 Atriplex vesi cari a (bladder saltbush) Atriptex vesicaria has value as a decreaser species on the Oodnadatta saltbush tablelands, Atriplex vesicaria I Astrebla pectinata flats and run-on areas, Sattbush and Mitchell grass plains and plateaux and Maireana astrotricha I Atriplex vesicarí a calcareous flats. Traverses did not detect any trend in the abundance ol A. vesicaría lrom water. However, my observations noted during sampling of palatability ratings, cross fence comparison and tagging of plants showed this species is susceptible to cattle grazing. My observations also indicale A. vesicaria is only grazed by cattle during periods of low rainfall when more palatable plants are not available. During these dry periods stock should not be allowed to graze A. vesicaría heavily as the plants are susceptible to overgrazing (Perry, 1970; Leigh and Mulham 1971;Cunningham et al., 1g81;Stanley, 1983), often dying following severe defoliation. An example of this is evident at Parke's Camp on Todmorden Station where a large area of A. vesicaria has been killed by severe donkey grazing. Wilson and Graetz (1979), found that on the Riverine Plain when A. vesicaria is defoliated to less than 20 to 30 leaves the plant will not regrow and that regeneration is then dependent on the establishment of seedlings. However, if this species is only lightly grazed it will persist and continue to provide important fodder during dry periods. There is much titerature on the palatability and value ol A. vesicar,þ but most relates to grazing by sheep. Due to its high salt contenl A. vesicaría ts relatively unpalatable but is grazed during dry periods when more palatable plants are unavailable. But it is of little value for fattening stock and should only be used to maintain them (Ratcliffe, 1936; Knowles and Condon, 1951; Leigh and Mulham, 1965; Cunningham et al., 1981). 169 ln northern South Australia Atriplex vesicaria has varied life forms. This has also been observed by Ratcliffe (1936) who says "Atríplex vesicaríum is an exceedingly variable species; and the forms associated with different so¡l types not only differ in their resistance to drought and grazing, but have distinctive characteristics in their growth and the shape and size of their fruits and leaves". Where A. vesicanã grows on stony ground (Oodnadatta and Coongra land systems) grazing by cattle on this species has been observed to be quite severe. However, on Todmorden Station grazing is usually only observed within about 1.5km of a watering point. ln these areas there is usually high bush death and most plants have a large proportion of leaves removed. Near Moontand Bore A. vesicaria growing on calcareous flats is relatively unpalatable to cattle and communities here are generally ungrazed even within 1km of water. The plants also have a different form to those growing on stony ground. The preference cattle have for A. vesicaria can partly be attributed to water salinity. Cattle have a lower tolerance to water salinity than do sheep (Wilson and Harrington, 1984). Salinity affects the amount of water required by cattle and hence the uniformity of grazing. Therefore in areas of higher water salinity saltbushes are less likely to be selected. Where populations of this species are healthy this should be regarded as a sign that the range is in good condition. When stock begin grazing A. vesicarialhis should be regarded as an indicator that the more palatable plants are not available, and that the paddock should be de-stocked or only lightly stocked to reduce stock impact on the remaining plants. During dry periods A. vesicanã should only be used to maintain small numbers of livestock such as breeders or high plant mortality is likely. 170 Crotalaria eremaea (loose-flowered rattlepod) I suspect Crotalaria eremaea has indicator value as a decreaser species in Mulga and horse mulga on deep red sands and dunes and on the Mulga and sandhill wattle sand dunes which border lhe Maireana astrotricha I Atriplex vesícaria calcareous flats. This is because my observations showed C. eremaea was palatable to cattle and was often grazed until all the leaves had been removed and only the main stem remained. lt is often well grazed by sheep (Allen, 1949). Everist (1974) reports than in some cases sheep have been poisoned by this species. However, continuous traverses did not detect a change in the frequency of this species from water. When intense grazing ol C. eremaea occurs it is usually associated with heavy grazing of other palatable species growing in association with it as it does not appear to be preferentially sought by cattle. Thís species does however, appear to be relatively robust under cattle grazing, often re-shooting when grazed down. However, the number of times it can be defoliated and the intensity of grazing plants can withstand is not known. The most severe grazing of C. eremaea predictably occurs close to water where cattle are not as selective. However, in areas where there is an abundance of ephemerals and or annuals this species may be ignored in preference to the other more palatable plants. Enchylaena tomenfosa (ruby saltbush) Enchylaena tomenfosa has value as a decreaser species in the Mulga and horse mulga on deep red sands and dunes and on the Mulga and sandhill wattle sand dunes on Wooldridge land system. The decreaser characteristics of E tomentosa were shown by continuous traverses (which showed the frequency of E tomentosa increasing away from Wyjundi and Boundary Bores) and palatability 171 ratings (which showed it was highly palatable to cattle within 4.5km of water). However, tagging showed that this species can be moderately grazed by cattle and re-grow. Cunningham et al. (1981) regard E. tomentosa as being selectively grazed during dry periods but that it is not normally sought when forage is plentiful. My observations indicate it is heavily grazed by cattle during drought but is lightly to moderately grazed at other times. As with Rhagodia spínescens this species usually grows under mulga or other shrubs or trees where it is atforded some protection from cattle grazing. ln a Casuarina cristata community at lvanhoe, Leigh et al. (1979) reported that the absence of E. tomentosa may be a reliable indicator of heavy grazing by sheep. On the Riverine plain this plant has become uncommon in areas heavily grazed (Leigh and Mulham, 1965). I believe E. tomentosa should be regarded as a useful drought feed which needs to be managed sustainably during drought when it is most vulnerable to cattle grazing. lf heavy stocking is allowed to occur it will be severely grazed and eventually be eliminated. But if an area is de-stocked this species rapidly colonises. However, under light to moderate grazing it will persist and appears to recruit quite prolifically when allowed a period of recovery. Thus its presence should be regarded as a sign that the Mulga and horse mulga on deep red sands and dunes is in good condition. Eragro sti s eri o poda (wool lybutt) E. eriopoda remains static following light to moderate grazing but may initially increase under heavy grazing in the Mulga and horse mulga on deep red sands and dunes. However, if the heavy grazing is prolonged it will decrease. 172 Continuous traverses showed the frequency of E. eríopoda decreasing away from lightly stocked Wyjundi Bore, but this was considered to be because of environmental variation and not due to cattle grazing. However, no trend was detected from heavily stocked Boundary Bore even though it had been removed within 500m of the bore and tagging and palatability ratings showed it was palatable to cattle. My observations indicate E. eriopoda is moderately palatable when young but becomes less palatable with age. lt is however, a valuable drought feed. E. eríopoda will recruit from seed and regenerate from butts in areas of low to medium stocking. Other authors have reached similar conclusions about the pers¡stence and palatability oÍ E. eriopoda. lt is of low palatability but provides important forage during low rainfall periods (Simpson, 1992), but Lazarides (1970) and Cunningham et al. (1981) regard it as moderately palatable and report that grazing is normally restricted to new growth but disagree on its persistence following grazing. Lazarides (1970) notes that in areas of high stock concentration it is often eaten out. During dry periods in central Australia E. eriopoda is otten the basis of cattle diet (Squires, 1e81). Eragrosti s setiî olia (neverfai l) On the Oodnadatta saltbush tablelands, Eragrostis setifolia may increase following heavy stocking, but if heavy stocking is prolonged E setifoliawill eventually decrease and may be eliminated. This was evidenced from continuous traverses which showed E. setifolia increasing from Tucker's Bore but decreasing from Hyde Dam. 173 My observations and palatability ratings on this species made on Todmorden, Hamilton and Billa Kalina Stations indicate it is usually of low to moderate preference depending on the availability of more palatable species. As with Eragrostis eriopoda this species appears to become less palatable with age and I have often found it un-grazed when in flower even when growing close to some water points. However, at water points which have a history of prolonged heavy grazing this species appears to decrease. The abundance of E setifolia appears to vary little under light to moderate stocking. lt is a robust perennial grass often found in highest abundance close to water points where it survives longer than most other species of similar palatability and may even increase. E. setifolia is only moderately palatable and largely neglected during periods of abundant feed availability (Lazarides, 1970) but becomes less palatable with age (Leigh and Mulham, 1965). lt can withstand heavy grazing and may replace Astrebla spp. or Atriplex vesicaria as the dominant pasture species, if overgrazing is prolonged (Beadle, 1948b; Cunningham et al., 1981). lts abundance should therefore be heeded as a sign of possible overgrazing and of the need for the implementation of a new management strategy which involves lighter stocking. Eremophila gilesii (green turkey-bush) This study has failed to determine the indicator value ol Eremophila gilesiiin Mulga and horse mulga on deep red sands and dunes, although the literature indicates it has increaser characteristics. At heavily stocked Boundary Bore no trend was detected. However, the continuous traverse from lightly stocked Wyjundi Bore showed the frequency of E. gilesiiincreasing away from the bore. This trend from Wyjundi Bore was disregarded however, as being due to environmental influence and not caused by cattle grazing. 174 Palatability ratings and my observations on this species at Wyjundi and Barney's Bore on Todmorden, and Timber Camp and Boundary Bore on Hamilton Station indicated that E. grlesrï was usually not palatable to cattle but was occasionalty lightly grazed during periods of low rainfall. Cunningham et al. (1981) report that in N.S.W. it is regarded as a weed and is seldom eaten by stock. lt increases in response to grazing in semi-arid woodlands (Harrington et al., 1984b). In Queensland E gilesii is also increasing (Burrows, 1971). Chippendale (1963a) suggests E. gilesiiis unpalatable to cattle because it has a viscid covering on the leaves but says that in central Australia it may be grazed in depressions where plants produce more succulent growth. My observations provide little insight into the ¡ndicator value of this species except that it is relatively unpalatable and might therefore increase following cattle grazing. But this has not occurred on Hamilton or Todmorden to my knowledge. ln the southern sheep rangelands (8. Lay, Senior S.A. Rangeland Officer, pers. comm.) and other areas described by the above authors this species is regarded as an increaser species, invading heavily stocked areas. Eremophila latrobei (crimson turkey-bush) Eremophila latrobeihas indicator value as a decreaser species in the Mulga and horse mulga on deep red sands and dunes and on the Mulga and sandhill wattle sand dunes on Wooldridge land system. This was evidenced by a continuous traverse from heavity grazed Boundary Bore, which showed that E. latrobei increased with increasing distance from the bore. However, at lightly grazed Wyjundi Bore no trend was detected. Palatability ratings and my observations indicate this species is of moderate palatability in Mulga perennial grass woodland, usually only being grazed severely during periods of low rainfall or when growing in 175 ctose proxim¡ty to water. But on Wooldridge land system E. latrobei may be severely grazed at greater distance from water. Askew and Mitchell (1978) regarded this species as having moderate nutr¡t¡ve vatue and palatability to cattle but Chippendale (1963a) considered E. Iatrobeito be one of lhe Eremopfrla species preferred by cattle in central Australia. Jessup (1951) regarded it as very palatable and Cunningham et al. (1981) noted that it was often grazed severely by cattle. lf this species is to be sustained, managers should aim to stock lightly or this species may be eliminated from this type of mulga woodland. Like E. tomentosa th¡s species would normatly be one of the most frequent in this type of mulga woodland and its absence should be regarded as a sign of poor range condition. Eremophila macdonnellii (fuchsia bush) Eremophita macdonnellï has indicator value as an increaser species in the Mulga and horse mulga on deep red sands and dunes because I have seen its increase at Boundary Bore on Hamilton Station. However, it was not recorded using any of the methods described in this thesis because it only grew in the immediate vicinity of Boundary Bore. No titerature could be found on its palatability and persistence. Eriachne aristidea (broad-leaf wanderrie grass) I do not know whether E. aristidea has indicator value in the Mulga and horse mulga on deep red sands and dunes, as it was only encountered at Boundary Bore. The continuous traverse from Boundary Bore showed the abundance of E. aristidea decreasing with increasing distance from the bore. However, only a few individuals showed signs of being grazed but these had been grazed until only the butt remained. 176 E. aristidea usually grows on sand dunes and is usually distributed sparsely (Lazarides, 1970; Cunningham et al., 1981). But locally dense stands may occur in depressions or disturbed areas (Lazarides, 1970). Both authors agree on its palatability saying it is palatable when young but becomes less palatable with age. The above evidence suggests E. aristidea may increase following heavy cattle grazing because it is able to colonise disturbed sites and is only palatable when young, thereby largely escaping the impact of cattle grazing ¡f ¡t ¡s allowed to mature. Eriachne helmsii (woollybutt wanderrie) I do not believe Eriachne helmsii has any indicator value in the Mulga and horse mulga on deep red sands and dunes. Continuous traverses did not detect a trend lor E. hetmsiifrom either Boundary or Wyjundi Bore and palatability ratings and my observations and those of Cunningham et al. (1981) showed that it was unpalatable to cattle, except when young . Lazarides (1970) noted that while E. helmsii looks unpalatable, plants often show signs of grazing. Near Moonland Bore on Todmorden Station this species has been extensively grazed until only the butts remain. However, at the time of observation this area was recovering from extensive rabbit grazing and it was therefore difficult to determine whether the main damage was due to rabbits or cattle. From the evidence provided it would appear that E helmsii has little or no value as an indicator of range condition in Mulga and horse mulga on deep red sands and dunes. ln low shrubland communities however, such as near Moonland Bore it is probable this species has decreased due to rabbits and/or cattle. But until 177 rabb¡ts re-establish themselves at this site or cattle drink at Moonland Bore, the herbivore responsible for this grazing impact can not be determined. F ran ke ni a se rpyl I if olia (bristley sea'heath) Frankenia serpyllifotia has no value as an indicator of range condition on the Oodnadatta saltbush tablelands and Saltbush and Mitchell grass plains and plateaux. This was evidenced from continuous traverses which showed there was no change in the frequency of this species from water and from my observations at pyramid Tank, Mt Malua Bank, Mt Aggie and Yardinna on Todmorden Station and at Hyde Dam which showed that this species is normally not grazed by cattle. However, there is no evidence to suggest F. serpyllifoliaincreases under grazing. ln areas where this species grows or could normally be expected to grow and heavy grazing has occurred, the numbers ol F. serpyllifolia may be dramatically reduced or non-existent. Whether this is caused by grazing, trampling or natural variation is not known. However, this is not always the situation because within 300m of Mt Aggie Dam this species is recruiting prolifically and has not been grazed. The only literature which mentions the palatability of this species is Cunningham et al. (1981) who say this species is "not grazed to any extent". Mai reana aphylla (cotton bush) Maireana aphytla has little value as an indicator of range condition on the Oodnadatta saltbush tablelands and Saltbush and Mitchell grass plains and plateaux, but there is some evidence to suggest it may increase. Continuous traverses showed there was no change in the frequency ol M. aphylla from water, however, in degraded chenopod communities on Todmorden Station this species appears to be in higher numbers than elsewhere and thus I agree with Leigh and 178 Noble (1972a\ and Cunningham et al. (1981) that in degraded Atríplex vesicaria communities M. aphylla may increase. My personal observations on this species indicate it is normally not palatable to cattle but can be severely grazed when growing close to water or during dry periods which agrees with Leigh and Noble (1972a'¡, Cunningham et al. (1981) and Wilson (1979). Milthorpe (1973) reported that this species was of little forage value. ln areas with sandy soils M. aphylla may be damaged by cattle trampling but because it is highly resilient it does not normally die. Anon (1971)and Leigh and Noble (1972a) say M. aphylla can withstand total defoliation, but Leigh and Mulham (1965) say plants will die if subjected to continuous heavy grazing. Maireana astrotricha (low bluebush) Maireana astrotricha has value as a decreaser species on the Maíreana astrotrícha t Atríplex vesicaria calcareous flats. This was evidenced from density and percentage cover measurements from Moonland Bore (Chapter 4) which showed the abundance ol M. astrotr¡cha increasing away from the bore. This was also supported bythe majority of relevant literature. Jessup (1951) reported that in South Australia M. astrotricha is killed by heavy stocking; Graetz (1973) regarded M. astrotricha as a decreaser species because it was easily removed by grazing; Dalton (1988) quoted an undated paper by Wilcox and Morrissey as stating that M. astrotricha is a sensitive indicator of good range condition and Fatchen (1978) reported that M. astrotricha had decreased near Lake Frome, South Australia. The cause was thought to be due to grazing by cattle. However, Fatchen (1975) found no significant relationship between M. astrotricha abundance and distance from water when he examined a cattle piosphere in southern South Australia. 179 My observations on M. astrotricha made at Moonland Bore, Talbots Bore and Mt Alice Bore on Todmorden Station and on Billa Kalina Station indicate that M. astrotricha is usually not grazed by cattle except near watering points or in dry periods when feed is scarce. At these times this species may be heavily grazed. Besides cattte, the M. astrotricha communities are often heavily infested with rabbits. However, on Wooldridge land system they do not appear lo graze M. astrotricha or have any other impact on this species. I have often seen, like Ratcliffe (1936), very heallhy M. astrotricha growing on or near rabbit warrens. But while bluebush and saltbush may be nibbled by rabbits they are rarely if ever so heavily grazed as to be killed (Ratcliffe, 1936). Jessup (1951) asserts that while rabbits reached plague proportions in the north-west of South Australia during 1948 no areas of saltbush or bluebush suffered damage. Bastin (1982) found that in central Australia there was no strong evidence to indicate decline or of damage to M. astrotricha populations by raþbits although there was a tendency for small size classes of bluebush to be under-represented where rabbit abundance was high. He also found there was successful recruitment ol M. astrotrichain the presence of rabbits. This avoidance by rabbits is probably because of their high salt content which makes them unpalatable to rabbits (Jessup, 1951 ; Hall et al., 1964). The largest communities of M. astrotricha grow on the calcareous soils but M. astrotricha also grows in small communities on the Oodnadatta land system, where rabbit warrens are often confined beneath M. astrotricha. However, these plants are usually in fairly good condition even though grazing impact (mainly by cattle) on them is greater than for M. astrotricha growing on the calcareous soils. 180 Maireana georgei (satiny bluebush) I believe Maireana georgei may be a colonising species under moderate to heavy stocking in the Mulga and horse mulga on deep red sands and dunes and on lhe Maireana astrotricha I Atriplex vesicaria calcareous flats. The continuous traverse from Boundary Bore showed lhal M. georgei was increasing away from the bore, while at Wyjundi Bore no trend was found. Palatability ratings and my observations recorded in Mulga and horse mulga on deep red sands and dunes and low shrubland communities indicate M. georgeiis slightly to moderately palatable and may be severely grazed during drought. However, during long periods of low rainfall it naturally dies back only to re-appear after rain in high numbers. lt is often found very close to water points and in areas whlch have been heavily grazed. Many authors have written about M. georgeibut only Cunningham et al. (1981) have reported on its palatability. They describe M. georgei as being a useful forage plant which is relatively acceptable to stock. Barker (1972) reported that close to watering points M. georgei appeared to be stimulated, indicating a tolerance to heavy grazing, while Eldridge (undated) agreed but says the resilience of this species is due to its rapid growth, and rapid population turnover. He also noted lhal M. georgei colonised scalds at Sayer's Lake, New South Wales. Muirhead and Jones (1966) undertook sowing trials with this species near Hay N.S.W., they "doubted whether M. georgeiwould persist under duress as well as Atriptex vesícaria, but thought it a valuable pasture under light grazing". However, they noted that in the absence of grazing the species soon became twiggy. 181 M o n ach ather parad oxa (band icoot grass) Monachather paradoxa is an important decreaser species in the Mulga and horse mulga on deep red sands and dunes because of its high palatability and sensitivity to cattle grazing. Palatability ratings and my observations indicated that M. paradoxa is highly palatable to cattle when green but becomes less palatable as it dries otf. However, continuous traverses did not detect a trend lor M. paradoxa from either Boundary or Wyjundi Bore. Cunningham et al. (1981) say that M. paradoxa is highly palatable and can be eliminated from pasture if care is not exercised. So well regarded is this species in western New South Wales that attempts have been made by landholders to introduce it to pastures by broadcasting seed obtained from other areas. On Granite Downs Station in northern South Australia, Faithfull (1987) found that M. paradoxa is one of the more palatable perennial grasses occurring in the mulga perennial grass woodland. lt is known to decrease and its relative cover is a valuable condition indicator. Wilson and Hodgkinson (1990) reported lhal Monachather paradoxa is a preferred species of sheep making up 48"/o of forage in a semi-arid woodland. Panicum decompositum (native millet) Panicum decompositum will persist and recruit under light to moderate stocking but will decrease following prolonged heavy stocking on the Oodnadatta saltbush tablelands and Saltbush and Mitchell grass plains and plateaux. However, statistical analysis indicated there was no change in the frequency of P. 182 decompositum lrom Tucker's Bore, Mt Aggie Dam or Pyramid Tank, but that it was increasing in frequency with proximity to Hyde Dam. My observations at the traverse sites and from cross fence comparison showed that P. decompositum decreased following heavy cattle grazing. This was supported by my observations made at Mt Malua Bank and Yardinna on Todmorden Station, Tucker's Bore on Billa Kalina Station and Hyde Dam on Hamilton Station which showed that it was highly palatable to cattle. This was supported by Maiden, lBBg; Beadle, t948b; Lazarides, 1970 and Cunningham et al., 1981, although White (1935) regarded it as a useful fodder only when young and agreed with Beadle (1948b) and Lazarides (1970) that ¡t rarely survives in areas of high stock concentrations . My observations agree with those of Allen (1949) that this species becomes rank if left ungrazed in gilgais which contain water over long periods. I have also noted that when P. decompositum flowers cattle tend to avoid grazing ¡t in preference to other species. My observations also show that P. decompositum is generally robust; it is often grazedto the butt but usually re-shoots following summer rainfall. However, in areas heavily utilised by cattle P. decompositum is usually severely grazed but remains as one of the last surviving species. ln lightly to moderately grazed gilgais following summer rain this species will grow rapidly and become abundant. Ptil otu s obovatu s var. o b ovafus (smokebush) Ptilotus obovatus var. obovafus has slight indicator value as a decreaser species in the Mulga and horse mulga on deep red sands and dunes and on the Mulga and sandhill wattle sand dunes. However, continuous traverses showed no trend for this species. r83 My observations from Todmorden and Hamilton Stations indicate this species is of low to moderate palatability but may be grazed heavily in close proximity to water or during dry periods. However when I encountered this species in the Mulga and horse mulga on deep red sands and dunes on either of the above stations it was usually not grazed. Cunningham et al. (1981) reported similar observations and says that P. obovatus is grazed by stock but usually only after the more palatable plant species have been removed. They also say this species recovers well, even after fairly heavy grazing. Hhagodia spinescens (thorny saltbush) Rhagodia spinescens has value as a decreaser species in the Mulga and horse mulga on deep red sands and dunes and on the Mulga and sandhill wattle sand dunes because it is palatable to cattle. This was partly supported by the continuous traverse from lightly grazed Wyjundi Bore which showed R. spinescens increasing from the bore, while no trend was detected from heavily grazed Boundary Bore. Palatability ratings and my observations indicate this species is of moderate to high palatability to cattle but is a preferred species during dry periods. Often, plants growing within 1km of water are heavily grazed until they are only 30-60cm high and all their outer branches have been removed. However, the degree ol grazing is variable depending on rainfall and land system. Some protection from grazing is afforded lo H. spinescens as it normally grows under mulga or other bushes and trees where cattle have ditficulty grazing it. 184 However, at Birthday Bore on Todmorden Station B. spinescens grows within 100 metres of the bore and does not appear to have been grazed. These plants are bushier than normal and are growing in the open where they are not protected from grazing. I do not know why they are not grazed. Barker (1972) working with sheep in arid South Australia and Beadle (1948b) both regarded H. spinescens as palatable but do not mention to what degree. Chippendale and Jephcott (1963), however, reported that it is readily grazed by cattle and bushes are often eaten back to the main stem, while Leigh and Mulham (1965) reported that H. spinescens is good drought fodder often being heavily grazed during dry periods when alternative forage is unavailable. This agrees with Askew and Mitchell (1978) who say that following overgrazing by cattle this species may decrease or even be eliminated completely. ln conclusion, F. spinescens should only be grazed lightly to moderately if it is to persist. Scler o ste gi a medull o sa (samphi re) Sclerostegia medul/osa has no indicator value on the Oodnadatta saltbush tablelands because no evidence could be found to suggest it either increases or decreases following cattle grazing. Cross fence comparison showed that even in heavily stocked areas this species was not grazed and traverse one from Tucker's Bore did not detect a trend for S. medullosa. My observations indicate S. medullosa is unpalatable to cattle. On Todmorden and Billa Kalina Stations where range condition is poor i.e. near water, this species is one of the last to persist. I suspect this unpalatability is due to its high salt content, but I could find no literature on its palatability. 185 Senna artemisioides ssp. artemisioides (silver cassia) Senna artemisioides ssp. artemisioides has indicator value as an increaser in the Mulga and horse mulga on deep red sands and dunes (especially after fire) and on the Mulga and sandhill wattle sand dunes. However, continuous traverses did not detect a trend for it. Palatability ratings and my observations on this subspecies indicate it is rarely grazed by cattle unless growing near water when it may be severely grazed. Chippendale and Jephcott (1963) agree and say that while it contains high levels of protein and phosphorous and little fibre, it is not very palatable to cattle. lt is also generally unacceptable to goats and sheep (Harrington, 1979). On the Wooldridge land system this species has increased and become abundant where heavy grazing has occurred. But in the Mulga and horse mulga on deep red sands and dunes this subspecies is very common, otten growing in dense thickets. lt is therefore otten difficult to determine whether it is increasing or is just growing as localised thickets. Near Alleumba Waterhole on Todmorden Station a severe fire in the late 1940's destroyed the Mulga and horse mulga on deep red sands and dunes. However, Senna artemisioides ssp. artemisioides appears to have benefited from the fire, growing back at this site in large numbers. This has also been reported by Walker (1980) who says that there is apparent stimulation of germination by fire. On a tour of western New South Wales in 1992 I was shown areas where this subspecies has increased in number and it is considered a woody weed as reported by James, 1960, Hodgkinson, 1979 and Muir, 1992. This subspecies has become a problem woody weed from the Cobar area to the West Darling (Cunningham et al., 1gB1). lt has atso reached serious woody weed status in Queensland (Hodgkinson, 186 1979). According to Chippendale (1963a) Senna spp. tend to increase in open woodland when other competing shrubs are depleted. Senna artemisioides ssp. îilifolia (punty bush) This species has indicator value as an increaser species in the Mulga and horse mulga on deep red sands and dunes and on the Mulga and sandhill wattle sand dunes. However, continuous traverses failed to detect a trend for this subspecies. My observat¡ons on this species from Todmorden and Hamilton stations indicate it is unpalatable to cattle except when growing near to water. lt is generally unacceptable to goats and sheep as well (Harrington, 1979). But, Chippendale and Jephcott (1963) note that in some areas cattle graze on the leaves and pods of some varieties of this plant. On Todmorden Station this subspecies appears to be increasing on Wooldridge tand system. This is predominantly where heavy horse or caüle grazing has occurred. However, this subspecies does not appear to be increasing at Wyjundi or Boundary Bores but I know it has increased in other areas. Examples are De Rose Hill Station where this subspecies is an increaser under excessive cattle stocking (Barratt and choate, 1984), and in the northern districts of western New South Wales where overstocking has lead to its increase (Cunningham et al., 1981). Because of its invading characteristics this subspecies has been defined as a woody weed by the Western Lands Act of 1901 (Muir, 1992). lt has also reached high woody weed status in Queensland (Hodgkinson, 1979). Fire also appears to promote the increase of this subspecies. ln northern South Australia some areas of sandy country which have been burnt grow only dense punty bush while neighbouring unburnt areas have mixed stands of a variety 187 of plant spec¡es. Hodgkinson (1982) and Hodgkinson and Griffin (1982) report that fire has the effect of breaking seed dormancy and promoting germination. Sida ammophila (sand sida) Sida ammophita has indicator value as an increaser species in the Mulga and horse mulga on deep red sands and dunes and on lhe Maireana astrotricha I Atriplex vesicaria calcareous flats. However, continuous traverses did not detect a trend for this species. My observat¡ons indicate it is mildly palatable to cattle, often being nibbled but rarely severely grazed. However, Cunningham et al. (1981) reported that this species is a valuable forage in summer and cattle will avidly graze it. This species usually grows in sandy areas and is common in Mulga and horse mulga on deep red sands and dunes where sand dunes occur. My observations do however suggest this species, along with Sida fibulifera, otten increases in abundance in degraded areas such as around bores in Mulga and horse mulga on deep red sands and dunes and low shrubland communities. The increaser characteristics of Sida spp. were also reported by Squires (1981). Solanum ellipticum (velvet potato bush) Solanum ellipticum appears to increase in heavily grazed areas in the Mulga and horse mulga on deep red sands and dunes and on the Mulga and sandhill wattle sand dunes. Palatability rat¡ngs and my observations indicated this species was not normally eaten by cattle except during dry periods when it was grazed within 3km of water. This species appears to have colonising characteristics as I have often found it growing close to watering points and in other disturbed areas i.e. station tracks and stock yards. 188 However, continuous traverses showed S. ellipticum increasing away from Wyjundi Bore but showed no trend at Boundary Bore (except increasing in the immediate vicinity of the bore). Very little has been written on the persistence and palatability of this species, probably because it is not considered a useful pasture species and has been suspected of poisoning livestock (Everist, 1974). Spo robol us acti n o clad u s (katoora) Sporobotus actinocladus has value as a decreaser species on the Oodnadatta saltbush tablelands and Saltbush and Mitchell grass plains and plateaux' Continuous traverses showed S. actinocladus increasing in frequency from Hyde Dam but no trend was detected from Tucker's Bore. Percentage cover and density measurements and cross fence comparison showed it decreased in areas of heavy stocking. This was supported by my observations at Mt Malua Bank, Mt Aggie and Pyramid Tank on Todmorden Station and Tucker's Bore on Billa Kalina Station which indicated this species is highly palatable to cattle. Most authors who have studied S. actinocladus agree that it is highly palatable and nutritious, especially before flowering (Cameron, 1961a; Lazarides, 1970; Cunningham et al., 1981; Roberts and Silcock, 1982), but because of its high palatability it has declined in areas heavily grazed by cattle (Lazarides, 1970). This was supported by Williams and Roe (1975) who reported finding a substantial decrease in the density ol S. actinocladus after heavy stocking with steers. However, Barratt and Choate (1984), on De Rose Hill Station in northern South Australia disagree that S. actinocladus is palatable to cattle and say it is "low in palatability and increases in degraded bladder saltbush communities". 189 I believe that this species will regenerate from butts if rested from grazing but if continuously grazed or insutficiently rested then death will eventuate. Under light to moderate grazing regimes it is unaffected and will persist in high numbers. 11.2 APPLICATION OF THE LCI CONCEPT IN NORTHERN SOUTH AUSTRALIA The assessment of leases in southern South Australia using the Land Condition lndex is based on the concept that climax or ungrazed communities can be identified and that reliable indicators can be used to show degradation from this ungrazed state caused by livestock grazing (8. Lay, pers. comm.). This approach is based on the premise that vegetation grazed by livestock will change predictably and thus can be reliabty and objectively assessed for range condition as specified by the South Australian Pastoral Land Management and Conservation Act (1989). However, in arid northern South Australia, where rainfall is unreliable and vegetation is usually dominated by perennial grasses, climax communities are often difficult to identify. "ln arid Australian environments there is no identifiable climax vegetation but rather a series of alternative short-lived states as a consequence of the seasons when rain falls" (Friedel, 1991). Thus lhave encountered two fundamental problems with the use of range condition indicators for use in LCI criteria in northern South Australia. These are: 1. Many perennial species are hard to detect in drought e.g. perennial grass tussocks can survive even if grazed flush with the soil surface. 2.Ihe high resilience of some species of perennials to drought means that vegetation which appears severely degraded otten recovers markedly following rain. 190 Therefore any use of these species will tend to result in the calculation of the index being affected by seasonal conditions. Recently CSIRO developed a land degradation assessment system for use in rangelands which utilises remotely-sensed satellite data to separate grazing effects from natural variation (the interested reader is referred to Bastin et al., 1993a). This system was st¡ll in the development stage during field work for this Masters Degree and so I did not have an opportunity to trial it in northern South Australia. I believe that such a system may overcome the problems I have outlined with the LCl. However, if the LCt is retained in part or in full for assessing northern South Australian cattle leases I recommend three changes be made to the LClto overcome the above problems. Recommendation 1: As mentioned above the current LCI approach to assessing leases in southern South Australia is based largely on condition criteria which assumes those using the LCI know what plant species should be present and absent (indicator plants) for a particular range component. But in northern South Australia some of these indicators can not always be found. Thus a solution to this problem is to use a complementary approach which entails the use of condition criteria in conjunction with "utilisation" criteria. "Percentage utilisation" (an estimate of the percentage of the plant which has been grazed) has already been used in the LCI to assess perennial grasses. Utilisation is defined as in the glossary of terms of the Society for Range Management (1974) as "the proportion of current years'forage production that is consumed or destroyed by grazing animals". The utilisation of perennial plants is important as grazing too close and/or during improper seasons leads to plant death and a subsequent decline in range condition (Heady, 1949). 191 Utilisation criteria have advantages when used in conjunction with condition criteria. First, during drought when some plants are not visible, those indicator plants stili remaining can be assessed on the proportion of grazing which has occurred. Thus this shows the effect of grazing on the pasture as a whole. Second, from a management perspective, by knowing the amount of utilisation which causes death for particular species it is possible to remove stock before this level of utilisation is reached (McKeon et al., 1990). Finally, where climax communities have not been identified for particular range components, utilisation of known indicator species can be used as an alternative to condition assessment. This is because the same indicator species growing on ditferent land systems appear to respond similarly to cattle grazing in northern South Australia. At present these utilisation criteria can be developed for the more common plants growing in northern South Australia from literature already available and from this thesis, without the need for further field work. "Utilisation" criteria have the advantage of being easy to apply and to combine with condition criteria. They have been incorporated into the LCI for the range components investigated during this study (see Section 11.3). Recommendation 2: Those using the LCI approach need to undergo an intensive training period and familiarisation with the variations in seasonal conditions in northern South Australia and their influence on the various range components if leases are to be reliably assessed. Recommendation 3: When those using the LCI do not feel they can accurately assess a site they may have to record that site as being "non-assessable" and move to the next site. This will eliminate the problem of assessors guessing a rating for a site because of insutficient evidence. 192 OF RANGE CONDITION DERIVED INDICATORS 11.3 INCORPORATION OF THE INNoRTHERNSoUTHAUSTRALIAINToADRAFTLcIMANUAL classes of descriptions of the three condition The following is a synthesis into during this for each range component investigated the indicators of range condition condition fotows that used in the Land study. The format of these descriptions build on those Austra*a and these indicators rndex Manuar for southern south alreadypreparedbytheSouthAustralianDepartmentofEnvironmentandNatural Resources. TheindexingsystemusedintheLClManualisbasedonanumberwhich shrubrands "1") and a woodrands "2" and chenopod refers to the range type (Low letterwhichidentifiestherangecomponente.g.(l\Atriplexnummulariassp.omlssal saltbush tabl el ands' Atript ex v esicai a- Ood n adatta Asetofphotographicstandardshavealsobeenproducedforeachrange (App. s). However' a full is incruded in this thesis component but onry one example Branch of the lodged with the Pastoral Management set of photographs has been SouthAustralianDepartmentofEnvironmentandNaturalResources. ThefollowingdefinitionshavebeenusedinthedraftLandConditionlndex Manual, which follows' class 2 - degraded "lair 3 = fìêâf intact 'good condition", condition crass descriptions: crass degraded "poor condition"' condition" and class 1 - SOvêrêlY the ,'he between crowns divided by is defined as average distance crown separation Ratio (cs') averagesizeofthecrown..(McDonaldetal.,1984).Thisisestimatedusingthemeanof12 measurementswhicharegroupedintovariousclasses(Table11'2). 193 Table 11.2. Crown separation classes ùown Closed or derse Mid - dense Sparse Very spane lsolated planb lsohed dumps Separatlon Fleld crlterla Touching - tr Touching - Clearty Well separabd lsolated planB lsolabd dumps o/erþpprng slight separated separalion Oown s€paratlon ratlo RANGE TYPE: 1. CHEIIOPOD SHRUBI-ANDS Coupone¡¡t: (f) Atriplex nummularia ssp. omissa I Atriplex vesicaria Oodnadatta saltbush tablelands. Description: Uniform flat to undulating gilgaid gibber tableland with gilgais normally aligned along contours. Vegetation is predominantly confined to watercourses, gilgais and gilgai fringes. Soils: Deep red clays or clay-loams; sal¡ne and dispers¡ve. The land surface has a heavy quartz¡te stone cover. The gibber may vary from dark red to black in different areas and range from a few centimetres in diameter to 10 - 1Scm in diameter. Occurrence: This component ¡s widespread in the northern catt¡e rangelands. 194 CONDITION CLASS DESCRIPTIONS: 3. Gilgai crabholes ¡ntact (without sediment accretion), supporting intact Atriplex nummularia ssp. omissa and or Sc/erostegia medullosa. Atriplex vesicaria intact and ungrazed where present. Usually Astrebla pectinata, Panicum decompositum and Sporobolus actinocladus present but not utilised more than 50%, with some seed heads still apparent at most times except during drought. 2. Gilgai crabholes intact. 11 A. vesicana present it may be grazed but not to cause significant bush death. Perennial grasses A. pectinata, P. decompositum and S. actinocladus utilised more than 50% but less than to 90% in dry periods, but still present. 1. Crabholes intact or progressively infilled with sediment and trampling to a greater or lesser extent. Any perennial grasses utilised to 90% or greater. ,4. vesícaria grazed hard or absent. Onty unpalatable perennials remain (A. nummularia ssp. omr'ssa, Frankenia serpyllifolia and S. medullosa). lncrease in Sclerolaena spp., Atriplex holocarpa, A. lindleiand Drssocarpus paradoxus. Notes: A, vesicaría does not grow evenly throughout the tableland but appears to prefer more saline areas. Thus assessment of gilgais should be based on observation of a number of gilgais. During dry periods perennial grasses are otten difficult to detect or identify but will re-grow following rain. S. medullosa is not palatable to cattle and has no indicator value because it does not appear to increase following heavy grazing. 195 RANGE TYPE: 1. CHENOPOD SHRUBI.ANDS CONtiNUEd Cor'¡poruerur: (m) Atriplex vesicaría I Astrebla pectinata flats & run-on areas' Stony tablelands. Description: Flats and run-on areas dominated by Atriplex vesicaría and usually Astrebta pectinata. These areas usually occur on Oodnadatta saltbush tablelands and may be from about 20m to 1km wide. Soils: Deep red clays or clay-loams; saline and dispersive. The land surface has a heavy quartzite stone cover. Occurrence: This component is widespread in the northern cattle rangelands. CONDITION CLASS DESCRIPTIONS: g. Gibber surface intact supporting ¡ntact and ungrazed Atriplex vesicaria and usually Astrebla pectinata. A. pectinata it present utilised less than 5O/o. A. vesicaria has a CSR of 0.25-1. 2. Gibber surface predominantly intact, A. vesicana present and may be grazed but not sufficiently to cause significant bush death. CSR of 1-20. A. pectinata utilised more than 50% but less than 90%. 1. Gibber surface may be intact or disturbed exposing the soil surface. A. vesícariagrazed hard or absent. CSR of >20. A. pectinataabsent or utilised greater than 90%. Notes: A. pectinafa usually, but not always present in this range component. ln areas where A. pectinafa is absent, overgrazing is indicated by heavy grazing of 196 A.vesicaria. However, care must be taken as A. vesicaría may drop leaves during drought and give the appearance of being grazed. RANGE TYPE: 1. Chenopod shrublands continued Cotvlporuerut: (l) Atriplex vesicaria t Astrebla pectinata - Saltbush and Mitchell grass plains and plateaux. Description Undulating gilgaid gibber tablelands. Stones are rounded or angular and range in size from 3 to 30cm in diameter. The plains and plateaux are treeless except for the occasional Eremophila spp. The majority of perennial plants are confined to gilgais. Soils: Deep red clays or clay loams. The land surface has a sandstone and/or shale and gibber cover. Occurrence: This component ¡s widespread in the northern cattle rangelands, but rarer further south. CONDITION CLASS DESCRIPTIONS: g. Gilgais intact (without sediment accretion), supporting intact and ungrazed Atríplex vesicaría. CSR <0-1. Astrebta pectinata, Sporobotus actinocladus and Panicum decompositum (il present not utilised more than 50%, with some seed heads still apparent except during drought). 2. Gilgai crabholes intact; A. vesícaria present and may be grazed but not to cause significant bush death. CSR 1 ->20. A. pectinata, S. actínocladus and Panicum decomposifum utilised more than 50% but not more than 90%. 197 1. Crabholes intaqt or progressively infilled with sediment and trampling to a greater or lesser extent. A. vesícaría grazed hard to cause significant bush death. CSR >20. Perennial grasses utilised to 90% or greater and there may be significant removal or complete loss. Notes: During drought A. vesicaria may lose the majority of its leaves and appear dead. The perennial grasses also appear dead and may be difficult to find. However, if there is a varied age structure ol A. vesicaria and the appearance of plants has not been altered by grazing then the community is in good condition and will re-grow following rain. RANGE TYPE: 1. CHEruOPOD SHRUBLAI.IOS continuEd Corr¡ponerut: (a) Maireana astrotricha I Atriplex vesicaría calcareous flats. Description: The calcareous flats grow open communities of Maireana astrotricha and/or Atríplex vesicaria. lndividuals of both species are separated by areas of bare ground which support abundant annual grasses and herbs after significant rain. Soils: Duplex profile, strongly calcareous throughout Occurrence: Widespread throughout the northern rangelands but becoming less frequent towards the Northern Territory border. CONDITION CLASS DESCRIPTIONS: 3. Maireana astrotricha and Atriplex vesicaría may grow together or separately. M. astrotricha and A. vesicaria ungrazed to moderately grazed. Some grazing of bushes is allowed but not to the extent where bushes are totally defoliated or have been severely reduced in size. The majority of bushes are alive and about 70cm tall. CSR of <0-20. 198 2. M. astrotricha and A. veslcana completely killed or defoliated. May be an increase in Sclerolaena spp., Dissocarpus paradoxus, Salsola kaliand Srda spp. 1. M. astrotricha and A. vesicaria removed apart from isolated remnants (CSR >20) which often have a build up of sand around their bases. The soil crust is no longer stable and showing evidence of dispersion or drift. Shrubs remaining are usually old with no regeneration. Notes: A. vesicaria and M. astrotr¡cha naturally grow together or separately and thus the absence of one species does not necessarily indicate a decline in range condition. RANGE TYPE: 2. LOW WOODuANDS Cotr¡poruerut: (e) Acacia aneura t Acacia ligulata (Mutga and sandhill wattle sand dunes). Description: Sand dunes dominated by Acacia aneura and A. ligulata with a shrub and perennial grass understorey. ln some areas the native pine (Callitris columellaris) occurs also. Soils: Deep sands with loamy sands at depth Occurrence: Widespread throughout the north of the district. CONDITION CLASS DESCRIPTIONS: 3. No obvious browse line on Acacia aneuratrees. Regeneration occurring of A. aneura, Rhagodía spinescens and Eremophila latrobei. Perennial grasses present (usually Eragrostis spp.) but not grazed more than 50%. Z. May be a browse line evident on A. aneura, R. spinescens and E latrobei or branches broken within grazing reach. Reduction in perennial grasses or grazed to 199 9O%. lncreased abundance of Senna spp., Acacia ligulata, Solanum ellipticum and SrUa spp. 1. A. aneuratrees have a pronounced browse line with most foliage removed. Palatable shrubs (R. spinescens, E. latrobeiand Enchylaena tomenfosa) grazed hard or are absenl. Acacia ligulata and senna spp. dominate and the community is noticeably more open. There is also little or no recruitment of palatable species. Perennial grasses are absent or grazed greater than 90%. The sand surface may be unstable and prone to dritt. Notes: The majority of plant species growing here also grow in the Mulga and horse mulga on deep red sands and dunes (2a) and therefore the indicators of range condition are similar. RANGE TYPE: 2. LOW WOODLANDS CONtiNUEd Cotr¡poruerur: (a) Acacia aneura I A. ramulosa (Mulga and horse mulga on deep red sands and dunes). Description: Dense mulga overstorey over a variety of perennial bushes and grasses. After rain annual and ephemeral plants grow but never form a very dense cover. The land surface may be undulating, dominated by sand dunes, or may be flat. However, the perennial plant species are similar on both land surfaces. Soils: Uniform deep red fine loamy sands. Occurrence: This component is more common in the north of the district. 200 CONDITION CLASS DESCRI PTIONS: g. No obvious browse line on Acacia aneuratrees. Regeneration occurring of A. aneura añd / or A. ramulosa. Perennial grasses present in groves but not grazed more than 5O%. Palatable shrubs such as Eremophila latrobeí, Enchylaena tomentosa and Rhagodía spinescens largely ungrazed. No increase in woody weeds. 2. May be a browse line evident on mulga or branches broken within grazing reach. Regeneration occurring of A. aneura and/or A. ramulosa. Browse line evident on palatable perennial shrubs (E latrobeí, E. tomentosa, R. spinescens). Reduction in perennial grasses (Monachather paradoxa, Eragrostis eriopoda, Eragrostis spp. and Digitaria coenícota) or grazed to 90%. The woodland is noticeably more open because of the reduction in size of bushes and decrease ¡n some species. May be an increase in Senna artemisioldes ssp. artemisioides and Senna aftemisíoides ssp. filifolia. 1. A. aneuratrees have a pronounced browse line with most foliage removed. palatable shrubs removed or grazed severely. All perennial grasses absent or grazed greater than 90%. May be an increase in Eremophila macdonnellii, Senna artemisioides spp, juvenile mulga and Acacia ligulata. Juvenile mulga may also increase to be in numbers higher than for classes 3 and 2. The woodland is sparse because of the reduction in palatable species. The land surface is often exposed with some dritt or scalding evident. Notes: Perenniat grasses are naturally absent from intergroves. Therefore topfeed indicators should be used in these areas. 201 CHAPTER 12 FINAL CONCLUSIONS llr¡OlCnfOnS lru HOnl 12.1 REFLECTIONS ON THE PROCESS USED TO DERIVE INDICATORS DURING THIS STUDY Eight methods of field work were used to determine indicators of range condition during this study. ln light of this study I now know that indicators can be quickly and reliably determined using a combination of the knowledge of pastoralists, cross fence comparisons, the literature, astute field observations, and rapid field surveys of palatability ratings. These five methods of determining indicators provided more reliable information on indicators than did laborious quadrat based sampling techniques. Whilst the quadrat based sampling techniques did provide information on indicators, their usefulness was substantially restricted by the heterogeneity of vegetation and the inconsistent trends which were sometimes revealed. Furthermore, much time was needed to collect, collate and analyse the data. Photopo¡nts, exclosures and tagging of plants were also of little value for determining indicators in the short term as they were influenced by seasonal conditions; however they might be useful in the long term. Historical photographs were also of little value even though they did detect some indicators because they were hard to relocate and usually only showed areas of severe stocking impact. 202 The methodology I would use to determine indicators of range condition is: 1) familiarise myself with the more common plants in the region to be studied. This would involve reading relevant literature and making plant identifications in the field. 2) seek the opinion of local pastoral¡sts who usually have a knowledge of the preference their livestock have for the more common plants of the region. Pastoralists can also provide information on the effect of geographical and seasonal conditions on plants and historical information which is not avaitable from other sources. This information does, however, vary in its reliability between pastoralists. S) Therefore other field methods should be used to collect additional facts which can be used to verify information thus obtained. These methods include the use of palatability ratings via rapid field survey, cross fence comparisons and field observations. Another complication in a region subject to unseasonal rainfall such as in northern South Australia, is that the preference of livestock varies dramatically with seasonal conditions. Therefore information should ideally be collected and compared for rainfall events at various times of the year, before indicators are concluded. 12.2 CONCLUSIONS 1. lndicators of range condition have been determined for the more-abundant perennial species. 2. Some range components are heterogeneous and it is therefore difficult to discern the etfect of cattle grazing from natural variation using quadrat based sampling techniques. 203 3. The high resilience of some species of perennial vegetation to drought means that vegetation which appears severely degraded otten recovers markedly following rain. Any use of these species in LCI criteria will tend to result in the calculation of the index being atfected by seasonal conditions. Thus I conclude more use be made of "utilisation" as a way around these problems. 4. Cattle induced grazing gradients from water can be detected in northern South Australia when environmental parameters influenced by cattle grazing are sampled radially from water on uniformly vegetated range components. These findings are similar to those of Osborn et al. (1932), Lange (1969), Barker and Lange (1970) and Fatchen (1975). This study has shown the feasibility of using short term methods to determine indicators of range condition. However, no single method achieved this. The most reliable method appeared to be the rapid field survey of defoliation ratings recorded radially from water. This is a method which can be used on both uniform and heterogensous range components. Quadrat based techniques were used to sample grazing gradients but their application was limited in northern South Australia by the spatial heterogeneity inherent to many range components, the unreliable trends which can be obtained for no apparent reason and the time needed to find and then sample suitably uniformly- vegetated sites. Other methods used such as relocation of historical photographs and cross fence comparisons provided some information on indicators and were used during this study to supplement information acquired from quadrat based methods. 204 However, exclosures, photopoints and tagging perennial plants were of little value to this study because they were influenced by seasonal conditions and therefore provide predominantly long term information. 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CSIRO, Melbourre. wirson,Á'R;ñi.9,,liS?5'iñ?l#,î;JJ,?:îì Jn'"[,î'J3it"X'å"9'Sïî".1%Siffi3'îil3 Ñätiïã'c rãËð woirdnop Dubõo, N. s.w. e, J.C. (1988). Vege-tation attributes and t'ot Rusiraliari rangelands. /n; Vegetation management. (Ed. P.T. Tueller). Kluwer Wilson, 4.D., Tongway, D.J., Graelz, îrD.and Youn9, \l'D: (1.994)'Fl-anqe invenrory'ä;l¡*"h"_";itöñ;-¡;: MãL"g;$ent õi Àùêtràl¡a's' ransðlands. (Eds ö.Ñ- Hãíriñgtón, A.D. Wiison and M.Õ. Young). CSIRO, Melbourne. wirson,Ás,"ï3.1511".,íö,?i;011,31?¡E2i,zln"72l:it?'."åBf ricabretothe Wuerthner G. (1993). The real cost of a hamburger. Earthwatch. July/August. Zeevalking, H.J. and Frescg, L_.f.[4.(19.7!1. Rabbit grazing and species diversity in a drJne arca. Vegetatio.35: 193-196. 219 APPENDIX I DATA FOR CHAPTER 3 Species which yielded significant trends between P(X) and distance. o o € o ìo D o € o o o o o o 0 r000 2000 3000 ¿¡00 5000 o¡stance (m) App. 1.1. Frequency of Astrebla pectinata from Hyde Dam o a q o a a @ àc; G -oo rLa o q o Io 0 2000 4000 6000 Oistanco (ml App. t.2 Frequency of Astrebla pectinata from Tucker's Bore (Traverse 1) 220 @ c; q o -- a ã(! .oo a ÀT o ô, cj oI 0 2000 4000 6000 o'stance (m) App. 1.3 Frequency of Astrebla pectinata from Tucker's Bore (Traverse 2). o o o N o qo o bø € o ct o o o o 0 1000 2000 3000 .1000 5000 O¡stance (m) App. 1.4 Frequency of Eragrostis setifolia from Hyde Dam. 221 (o ct 6 ci oY = .o(! ! cì o o 0- q o ci q o 0 2000 4000 6000 Oislancs (m) a App. 1.5 Frequency of Eragrostis setifolia from Tucker's Bore (Traverse 1). (o ci --c| õ(ú ! o fL ol o q o 0 2000 4000 6000 Oistanco (m) App. 1.6 Frequency of Eragrostis setifoliafrom Tucker's Bore (Traverse 2). 222 o o o !=D @ Do o- Io o o 0 1000 20q) 3000 4000 5000 Oistance (m) App. 1.7 Frequency of Panicum decompositumfrom Hyde Dam. T o (l) o = bñ ôl ! o o f! o q o 0 2000 4000 6000 Oislsnco (m) App. 1.8 Frequency of Panicum decompositumÍrom Tucker's Bore (Traverse 1). 223 .q o a a e?o = bõ c\l a -oo o fL a a a a a o a a a Io o la a 0 2000 4000 6000 Oistanca (ml App. 1.9 Frequency of Panicum decompositum from Tucker's Bore (Traverse 2). 224 o à o a ! Ðé o c o o o a a o 1000 2000 3000 .(000 5000 Otíance (m) App. 1.10 Frequency of Sporobolus actinocladus from Hyde Dam. @ ci ('o ci a = _oñ -oo< o-o ôJ d o o a 0 2000 4000 6000 Oistar¡cÊ (ml App. 1.11 Frequency of Sporobolus actinocladus from Tucker's Bore (Traverse 1). 225 Þ lEt Probabifily T' Probabilily p 0.08 0.r0 p 0.0 0.02 0.0,t 0.06 0.0 0.1 0.2 0.3 0.4 0.5 06 rô (r) o N a ll a l1 a (D (D -o a -o c a c (D (D c)= o o I a ã o o a o À) I c) o Â) a Â) ä o ä o 6'o a o AJ ú; É (aÀi Q a q o ã o I a a ì 5 a l\' o 3 o lo b È o) \ ä \ Ë a À) Â) I o a o a a 3 3 u¡ a 8 o ã ô c å a -. f c o. f g) o q t a u¡ a o oTD (D a (D ä 3 Þ E ProbablilY T' Probeb I lY p p 0.8 0.'l 0.5 0.6 0.2 0¡l 06 o,o o.f 0.2 0'3 ô à o Ol -r1 ll a (D (D -o -o c t l- (D a (D a f f ¡ c) c) É a E o o rn a rn 5 o c) \ a \ f¡) B A) ä o o 5 o I o ß' a À) À' !) g Ê o I o I a I a a 1\' I e o ]\, o 5 g a 5 g o o I (/) U, A) !) a o o 3 3 a u¡ ã g a o g 5. c f- t f o- qf 0) a ,E oTD (D a o 6 ä Ò o 8 a a o C' a o ci þo o- o a a ( a a a a o aa a a o o a a a .. o t 0 1000 2000 3000 <000 5000 Oistance (m) App. 1.16 Frequency of Eragrostis er¡opodafrom Wyjundi Bore. q o o o > 'õ €"1 ùo sl o o o o o 1000 2000 3000 4000 5000 OêÞnce (m) App. 1.17 Frequency of Eragrostis eriopodafrom Boundary Bore. 228 a a e o a a a a a € o a D a a a Õ o t o- c; a I o a' a o o a 0 1000 æao 3000 App. 1.18 Frequency of Eremophila gilesiifrom Wyjundi Bore. t t cq o a I a o õ D o è o a N o a o a a o o a a 0 1000 2000 3000 App. 1.19 Frequency of Eremophila gilesiifrom Boundary Bore. 229 a 9 o a a o o :õ G ôo G .q o a a a o a a a 0 1000 æ00 3000 App. 1.20 Frequency ol Eremophila latrobei from Boundary Bore. o a a t I @ o I a =õ a o o @ c o a a a a a o 0 1000 2000 3000 .1000 5000 O'rstanc€ (nl App. 1.21 Frequency ol Eremophila latrobeifrom Wyjundi Bore 230 qo o ¡ c; õo a €o' a o- ù o9 t a o o a a o a a a taaa'aa a o r000 2000 3000 4000 5000 Oistanæ (m) App. 1.22Frequency of Eriachne ar¡stidea from Boundary Bore' 231 o t a @ o I rq o > õ @ ôo o- o € I a q a a a a a o o o r000 æ00 3000 4000 5000 Oistãnco (m) App. 1.23 Frequency ol Maireana georgeifrom Boundary Bore. oç o@ 5 o a Do a o- o ta a al o a a a o o o a aa a I 0 1000 2000 3000 <000 5000 Oirancs (m) App. 1.24 Frequency ol Maireana georgeifrom Wyjundi Bore. 232 o a R ö a t I o aa a õ ÐG o o- o o a o o a I I € aaa a a 0 1000 æ00 3000 <000 5000 O'lstancÉ (ml App. 1.25 Frequency of Rhagodia spinescensfrom Wyjundi Bore. a co a a a ¡ a @o a a D =G o o o I o- a a a N a o a a a o o a 0 '¡000 æo 3000 App. 1.26 Frequency ol Rhagodia spinescens from Boundary Bore. 233 ¡ o9 o o a a o a Do o G o t tt a o. a a ¡ a a a o aata I o d '5000 0 1000 æ00 3æ0 4000 Oistanca (m) App. 1.27 Frequency of Solanum ellipticum from Wyjundi Bore. oe € o õo o c o d o 1000 .2000 3000 Oistanc€ (m) App. 1.28 Frequency ol Solanum ellipticum from Boundary Bore 234 APPENDIX 2 DATA FOR CHAPTER 4 Appendix 2.1-2.6 show the raw percentage cover and density data. Appendix 2.7-2.27 show the non-significant scatterplots of cover and density with distance. Percentage cover and densitY data Oodnadatta saltbush tableland App. 2.1 The density of perennial plants recorded from Mt Aggie Dam. Denslty ol perennlal plants (number/400m'z) Distrnce from A. pectinab A. nummulariassp. A. vesicaria P. decompositum S. actinocladus waÞr(m) omissa 300 14(l 24 0 1 2sê) 1 1þ) (.) 1600 o0) 46 7 1 0 3300 æ 38 12 191 38 5800 2 68 10 æ3 ,18 8500 191 & o 22u 95 (a) These ptants were present 8t thls sltê only as a grazed butt. App. 2.2The percentage canopy cover of perennial plants recorded from Mt Aggie Dam. Percenlage canopy covel ol perennlal plants Disbnce from A. pectìnaÞ A. nummulariassp. A. vesicaría P. decompositum S. actinocladus wabr(m) omissa 300 0.48('| 5.6 0 o.s('l 0 1600 g{r) 4.O 2.2 0 0 3300 0.4 2.O 0 1.0 0.6 5800 1.21 9.0 0 12.O 1 8500 9.0 8.5 0 4.0 2 (a) These plants were pressnt at th¡s slte only as a grÊzod butt. App. 2.3 The percentage cover of bare ground and litter from Mt Aggie Dam. o/o Dlstence ftom water lmì Bare Ground 7o Llttet s00 86 2 1600 87 I 3300 72 2. 5800 61 14 85(x) 48 27 235 Maireana astrotricha I Atriplex vesicaria calcareous flats App. 2.4The density (number/400m2) and percentage cover ol Maireana astrotr¡cha (canopy cover), bare ground and litter from Moonland Bore. Dlstanco from watel Denslty of lL % Canopy cove¡ ol M. Yo Cover Bare Ground % Cover Lltter (m) ast¡ot¡Icha asl¡ot¡Icha 100 n 5 94 1 13m 54 I 56 24 2100 n 7 81 4 23q¡ 1Tt I 85 4 ¡[500 161 7 73 4 s4m 125 15 73 7 7m0 30e 20 65 7 App. 2.5 The density (number/400m2) and percentage cover ol Atríplex vesicaria (cãhopy cover), bare þround and litter from Moonland Bore. D¡stance from watol flenslty of Á. % Cenopy cover of Á. 7o Cover Bare Ground 9" Covor L¡ttor (m) veslcarla veslcarla 1600 183 7 47 28 3000 188 12 4S) 21 4600 187 19 æ 25 7000 æ2 12 57 25 Saltbush and Mitchell grass plains and plateaux App. 2.6 The density (number/400nÉ) and percentage canopy cover of perennial plants recorded from Pyramid Tank. Dlstance from water (m) L peclnab A, veslcarla P. decompositum % Caropy Denslty % Canopy Density % Canopy Denslty covef covel covef M 12.8 218 0.8 a 1.920) l9(.) f000 3.0 274 7.O s64 0 53 1900 1.0 60 2.O 114 0 10 æ00 1.0 356 4.O 603 0 54 6000 4.5 303 6.0 542 o7 58 (a) These planls were present at thls s¡te only as a grazod butt. 236 Non-significant linear regressions of percentage cover and density. 10 I I Y = -l.53xs + 0.000962Hs x 12 = 58.SX l- c) o 6 O o o) 4 o E 2 ()c) L q) È 0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Distance from Waterpoint (m) App. 2.7 Percentage canopy cover of Astrebla pectinata from Mt Aggie Dam. 200 I Y = -28.3re + 0.0189rs X 1s0 r2 = ,13,9I 100 -- cØ c) o 50 0 I I 0 1,000 2,000 3,000 4,000 5,000 6,000 7,ooo g,ooo Distance from Waterpoint (m) App. 2.8 Density oÍ Astrebla pectinata from Mt Aggie Dam. 237 10 o I I Y = 3.5lts + 0.00059lxs X 12 = 24.Ox 7 L q) 6 I o 5 O o 4 o) a CÚ c 2 G)() L 1 c) 0 o_ 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Distance from Waterpoint (m) App. 2.9 Percentage canopy cover ol Atriplex nummularia ssp. omissa from Mt Aggie Dam. 70 ! Y = 34.4xs + O.OO226¡s X 60 rz = 0.0f 50 ¡ t 40 .= U) c 30 c) o 20 10 0 o 1,000 2,000 3,000 4,000 5,ooo 6,000 7,000 8,000 Distance from WaterPoint (m) App.2.10 Densily oÍ Atriplex nummularia ssp. omissafrom Mt Aggie Dam. 238 5 4 Y = 0.895xs - 0.O00tl?xs x t- 12 = O.Ot o o o I O 2 o o) (ú C q) O t-o 0 o- o 1,000 2,000 3,000 ' 4,000 5,000 6,000 7,000 8,000 Distance from Waterpoint (m) App. 2.11 Percentage canopy cover of Atriplex vesicaria from Mt Aggie Dam 14 Y = 6.lgis - 0.000099xs x 12 12 = O.Ot 10 I I =e4 o2c) .0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Distance from Waterpoint (m) App.2.12 Densily of Atriplex vesicarialrom Mt Aggie Dam 239 14 12 L- o 10 o O I o o) 6 (ú c 4 o0) L 2 0) o- 0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,ooo g,o0o Distance from Waterpoint (m) App. 2.13 Percentage canopy cover of Panicum decompositumfrom Mt Aggie Dam. 300 Y = ?4.2Ës + 0.0239xs X 250 r2 = 33.?x I 200 t 150 .= I cQ oc) 100 50 0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 9,000 Distance from Waterpoint (m) App. 2.14 Densily oÍ Panicum decompositum from Mt Aggie Dam. 240 30 I Y = ,l .53xs + 0.00258¡s X 25 12 = 6O.44 I 0) 20 o C) o' 1 5 I Cf) (ú E 10 o)o c) 5 o_ I 0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 Distance from Waterpoint (m) App. 2.15 Percentage cover of litter from Mt Aggie Dam. 241 100 80 c) 860 o o.) (ú 40 c o o- 0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 Distance from Waterpoint (m) App. 2.16 Percentage cover of bare ground from Moonland Bore 25 20 Y = 8.33xs - 0.00032¡s X L 12 0.0X c) = 15 ()o 0) o) (ú 0 c o. C) tr lÈ I 0) II o- I 0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 Distance from Waterpoint (m) App. 2.17 Percentage cover of litter from Moonland Bore 242 25 ?o o oo 15 o o, (ú 10 C 0) Á oL o) CL 0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 Distance from WaterPoint (m) App. 2.18 Percentage canopy cover of Atriplex vesicaria from Moonland Bore 300 250 Y = 132¡s + 0.0198¡s X r2 = 61.9I 200 r I 150 Eq c oo 100 50 0 0 1,000 2,000 3,ooo 4,OOO 5,000 6,000 7,000 Distance from Waterpoint (m) App.2.19 Densily oÍ Atriplex vesicaria'from Moonland Bore. 243 60 50 t- 940o ?so I o) Y = 41.0xs + 0.00105xs X Ë20 12 = 0.0f oo) b10 o- 0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 Distance from WaterPoint (m) App. 2.20 Percentage cover of bare ground from Moonland Bore. 30 25 r L I o 20 ()o o 15 o) (g Y 25.5. 0.000196xs c 1 0 = - x o r2 = 0.0r o c) 5 o- 0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 Distance from Waterpoint (m) App. 2.21 Percentage cover of litter from Moonland Bore 244 100 Y = 25.2xs + 0.00567is X 80 12 = 9.5X 60 I I 'Ø 40 c o o 20 0 0 1,000 2,000 3,000 4,000 5,ooo 6,000 Distance from Waterpoint (m) App. 2.22Densily of Panicum decompositum from Pyramid Tank. 5 4 Y = 0.449rs - O.O000l9rs X r2 = O.Of t- o 3 o O 2 0) o) (ú I c 1 o t g o 0 I I o_ 0 1,000 2,000 3,000 4,000 5,000 6,000 Distance from Waterpoint (m) App. 2.23 Percentage canopy cover ol Panicum decompositum lrom Pyramid Tank 245 600 500 400 à Goo cØ E zoo 100 0 0 1,000 2,000 3,OOO 4,000 5,000 6,000 Distance from Waterpoint (m) App. 2.24 Densily oÍ Atriplex vesicariafrom Pyramid Tank. 1 0 I I Y = 2.65xs + 0.000545xs X r: 0.0x lÉ I = a) 7 o 6 C) (¡) 5 o) (ú 4 c 3 o) lÉo 2 o) o_ 1 0 0 1,000 2,000 3,000 4,000 5,000 6,000 Distance from Waterpoint (m) App. 2.25 Percentage canopy cover of Atriplex vesicaria from Pyramid Tank. 246 14 I 12 Y = 6.42fls - 0.0008315 x L 12 0.0f o 10 = o O I (¡) (') (ú 6 c I o 4 Lo I c) 2 o- I 0 0 1,000 2,000 3,000 4,000 5,000 6,000 Distance from Waterpoint (m) App. 2.26 Percentage canopy cover ol Astrebla pectinata from Pyramid Tank. 400 3s0 300 I 2s0 I 200 .= Ø Y = 198¡s + 0.0185is x ol- 150 r2 = 0.0I o 100 50 0 0 1,000 2,000 3,000 . 4,000 5,000 6,000 Distance from Waterpoint (m) App. 2.27 Density of Asfrebla pectinatafrom Pyramid Tank 247 APPENDIX 3 DATA FOR CHAPTER 5 Section A contains defoliation recorded, by plant species and site. Section B contains linear regressions. Section A: Defoliation recorded, by plant species and site. (Juvenlle) Acacla aneun (mature) Acacla aneun ¡ Dlstance fiom 'Range Welghted % Dlslance from Range Welghted % water (ml defollallon water (m) delollat¡on 0 50, 100 78 0 50, 100 78 500 æ,8o 60 500 50,80 70 100 1000 0,80 55 1000 0, 61 1500 80 80 1500 80,100 90 5,100 2000 0,80 19 2000 36 3000 0,50 3000 0,50 12 19 3500 0 0 3500 20,50 u 4000 0 0 4000 5,50 25 4500 0,80 æ 4500 5,80 42 5000 0,5 2 5000 0,5 3 5500 0 0 5500 0,5 2 6000 0,5 1 6000 0,50 25 5500 5 5 6500 5 5 7500 0 0 7500 0 Acacla veslcada Ac ac I a tetrag on op hyl I a t i Distance hom Range Welghted % Dlstance fiom Range Welghted % water lmì defoliation water (m) delollation 0 50, 100 82 0 20,80 50 500 80,100 90 500 0,5 3 1000 æ,100 65 1000 0,50 10 1500 s, 100 & 2000 0,50 8 2000 50,100 75 3000 0,80 I 3500 0 3000 0, 100 41 0 3500 o,20 I 4000 0,5 3 4000 5,20 13 5000 0 0 5500 50,100 64 5500 0 0 7000 æ n 6000 0 0 8500 0 0 'Range: minimum and maximum perc€ntag€ defoliation score (when available) for each site. 248 Section A continued At¡lplex nummulada ssp. omßsa Enchylaena tomentosa a -Range o/o Dlstance from Welghled % Dlstance from 'R"ng" Welghted weler fmì delollatlon water (m) defollallon 0 æ æ 0 80, 100 90 5æ 20,100 62 500 80, 100 90 1000 5 5 1000 5, 100 63 1500 20,100 57 2000 20,50 35 2500 0 0 3000 50,80 65 3000 n æ 3500 0,20 6 3500 0,5 2 4500 80 80 7000 0 0 5000 0 0 8500 0 0 5500 æ æ 6000 20,50 35 7500 0 0 E|E|grostls erlopoda Eremophlla gllesll t a Dlstanco lÌom Range Welghted % Dlstance fiom Range Welghted % water lml defollatlon water (ml defollallon 0 80, f00 95 0 20,80 45 500 0, 100 43 500 o,20 10 1000 0, 100 72 1000 0,50 13 2000 0, 100 57 2000 0 0 2500 100 100 3000 0 0 3000 0, 100 37 9500 0 0 4000 0,5 3 4000 0 0 4500 0,50 19 4500 0,5 2 5000 æ n 5000 0 0 6000 0,50 15 60æ 0,5 2 7500 0 0 Eremophlla latobel Erlachne helmsll t t Dlstance lrom Range Welghted % Dlstance from Range Welghted % water (m) delollatlon water (m) defollatlon 0 50,80 65 0 0,80 æ 500 æ,50 35 500 0 0 1000 0,80 27 1000 0 0 1500 50 50 2000 0 0 2000 0,80 u 3000 0 0 3000 0,50 17 3500 0 0 3500 0 0 4000 0 0 4000 0 0 5000 0 0 4500 20,50 ¡t5 6000 0 0 5000 0,80 40 7s00 0 0 6000 o,20 5 7500 0 0 249 Section A continued Mal¡eana astrct¡lcha Malreana georgel tR"ng" t D¡stanco from Welghled o/o Dlstance from Range Welghted % water lml defollatlon waler (m) d€follat¡on 0 80, 100 90 0 20,50 & 5æ 80 80 f000 0,80 27 1000 50,80 60 1500 5,æ 17 1500 50,80 65 2000 0,80 ¡l¡¡ 2000 50, 100 72 2500 æ æ 3000 50 50 3000 0,80 4Ít ¡1000 0,20 7 3s00 0 0 5000 æ,50 35 4500 50,80 65 5500 0,5 3 5000 0 0 6000 5,20 12 5500 0 0 6500 0 0 6000 50 50 Monachather pa¡adoxa Rhagodla splnescens t t D¡stanco from Rangc WelghÞd % Dlstance hom Range Welghled % waler lmì delollatlon wateÌ (m) defollallon 500 100 100 0 50,100 68 1000 100 100 500 80 80 2000 20,100 41 1000 50, f00 g 2500 100 57 1500 20,50 4s 3000 0,100 100 2000 0,80 51 4000 0, 100 s7 2500 20,50 3s 5000 0,50 13 3000 20,80 50 5500 æ æ 3500 0,80 I 6000 0,5 2 ¿1000 0,80 g) 6500 100 100 4500 æ,80 50 50æ 0,æ ¿lÍl 5500 o,20 6 6000 0, æ 10 *nna atlemlsloldes ssp, artemlsloldes Solanum elllptlcum I t Dlstance fiom Range Welghted % D¡stance from Range Welghted % waler (m) defolialion waler (m) deÍollatlon 0 0,80 s1 0 0,50 æ 500 0,20 6 500 0,50 æ 1000 0, 20 3 1000 0,50 21 2000 0,20 4 2000 050 æ 3000 o,20 4 3000 5 5 3500 0 0 4000 0 0 4000 o,20 I 4500 0 0 4500 0 0 5000 0 0 5000 0 0 6000 o20 6 5500 0 0 6000 0 0 6500 0 0 7500 0 0 250 Section B: Non-significant linear regressions of defoliation of plants from water 100 c o (ú 80 := o Y = 24.2. - 0.00,t61rs x (I) 12 = 27.6A o 60 o o) (ú c o 40 o o o- E 20 o I t -c I I .q) t o 0 = 0 1,000 2,000 3,000 4,000 5,000 6,000 Distance From Watering Point (m) App. 3.1 Weighted percentage defoliation of Acacia tetragonophyllalrom water 100 c o ir 80 := o c) o 60 o o) (ú c 40 oc) 0) o- E 20 0) -c 'õc') 0 2,000 3,000 4,000 5,000 6,000 7,000 8,000 = 0 1,000 Distance From Watering Point (m) App. 3.2 Weighted percentage defoliation oÍ Atriplex nummularia ssp. omrssa from water 251 100 c .9 .:(ú 80 Y = 7.6?fs - 0.001568 x o rz = ll.9f o) o 60 o o) (ú c 40 oc) l-o o- ]J 20 o -c 'õC') 0 ll III 3 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 Distance From Watering Point (m) App. 3.3 Weighted percentage defoliation of Eriachne helmsii(mature) from water. 100 c .9 Y = 31.6'- 0.00122i5 X 880 12 = 0.0t õ I o60o o o) (ú I I I 540o o I o- T E 20 I o O) rì I o U 3 0 1,000 2,000 3,000 4,000 5,000 6,000 Distance From Watering Point (m) App. 3.4 Weighted percentage defoliation of Maireana georgeífrom water. 252 c II o 100 (ú := o 80 Y = 92.0- - 0.009?rs X oo 12 = 1?.3X o o) (ú 60 c o) O o 40 I o- L)' o 20 I -c .g)o 0 = 0 1,000' 2,000 3,000 4,000 5,000 6,000 Distance From Watering Point (m) App. 3.5 Weighted percentage defoliation ol Monachather paradoxa from water 253 APPENDIX 4 EXCLOSURE DATA FOR CHAPTER 6 Appendix 4.1 - 4.4 show the percentage cover of the four exclosures atter two readings. Appendix 4.5 - 4.7 show the actual change in abundance of perennial plants at Moonland, Pyramid Tank and Wyjundi exclosures after two readings. App. 4.1 Percentage cover of plants (canopy cover), bare ground and litter recorded at Moonland exclosure. Plot Cattle Prool Control Rabblt Proof Date 17t8tr1 19t8Æ.2 17t8tr1 19/8¡92 17t8t91 19t8ß2 Percentaoe cover % % % % % % Bare ground 0 38.4 53.4 41.7 61.9 28.0 Gravd 0 0 0 0 o.2 0 Litter 1.9 20.8 27.1 1 1.1 24.5 17.9 Ephemerals s9.3 6.6 1.0 5.50 3.6 7.0 Aæciaaneura 1.9 2.5 o.4 0.6 o.2 2.1 Acacia ligulab 0 o.2 0 0 o.2 1.0 Acacia tetagonophylla 0 0 o.2 0 0 0 Atistida contorø 0.9 9.1 2.0 15.5 0 2.8 Atriplex vesiæria 't1.1 0.9 o.2 o.7 1.0 4.0 Croblariasp. 0 0 0 0 0 0.3 Dissoerpus paradoxus 0 0.6 1.0 2.7 0 0.8 Enchylaena tomentosa 3.7 0 0 0 0 0 Enneapogon avenaæus 0 0.9 0 0.1 0 2.4 E n neapog on cyl i nd ricus 2.O 6.9 0.8 5.4 0 4.1 Eragrostis dielsii 0 0.5 0 0 0 0.5 Eragrostis eriopoda 6.6 0.3 0 0 o.2 0 Eriachne helmsii 0 o.2 0 0 0 0 lvb¡rcana astotricha 3.7 1.4 0.3 0.4 2.8 2.3 Maireanageorgei 1.0 2.1 4.1 1.6 1.2 o.2 lvbireana tichopten 0.5 1.2 3.0 0 0 0.6 Portulaaoleraæa 0 0 1.0 1.8 0 0 mbtus obovatus 0 0 0 o.2 0 0 Appendix 4.1 continued over page 254 Appendix 4.1 continued PIot Cattle Proof Conlrol Rabblt P¡oof Dale 17t881 19/8¡92 1718ß1 19t8ß2 17/8¡9t 19/8/92 Percentaoe cover o[o lc ïo % % % Rhagodia spinescens 2.9 0.3 0.6 0.9 o.4 1.5 Salsola loli 0.5 2.4 2.O 5.9 0 18.s Scþrclaena divedcab 0.3 1.1 1.0 3.7 0 0 Scleroþena unifloa 0 0.9 0 0 0 0.3 *nna arÞmisioides ssp. s.7 2.O l.s 0.4 20 '1.9 a¡temisiokles Senna arbmisioides ssp. petidanb 0 0.5 0.6 18 1.8 3.6 SidafibuliÍeê 0 o2 0 0 0 o.2 100 100 100 100 100 1(þ App. 4.2 Percentage cover of plants (canopy cover), bare ground and litter recorded at Wyjundi exclosure. Plot Csttle Proof Conlrol Dato 26t981 21tsß2 26t9ß1 21t9ß2 Percenlaoe covel % %- % % Annual grass 0 1.5 0 0.3 Bare gound 73.9 62.1 68.8 70.1 Ephernerals 0.3 1.5 0 1.8 Utter 21.5 25.0 26.6 15.3 Perennial grass (Juv 2.9 0 2.O 0 unidentified) Acacia aneura 1.3 1.3 0.3 1.3 Aristida contotþ 0 o.2 0 o.2 Eragrostis eriopoda 0 1.5 0 2.2 Erenophila gllesü o.7 2.7 1.0 1.4 Eremqhilalatottei 0 0.5 1.3 1.2 Erodium Çygnorum 0 1.2 0 1.7 Maireana georgei 0 0.8 0 1.3 lvlonachather pradoxa 0 0.5 0 0.3 Portula@oleraæa 0 0.3 0 2.3 Pübus povstachyus 0 0.9 0 o.2 Salsola lcali 0 0 0 o.2 S,?a spp. 0 0 0 o.2 100 100 100 1m 255 App. 4.3 Percentage cover of plants (canopy cover), bare ground and litter recorded at Pyramid Tank exclosure. Plol Cattle Proof Control Date 4t3t92 23t4t93 4t3t92 23t4t93 Percentaqe cover % % % % Annual grass 2.6 0 0.3 0 Bare ground 63.0 66.5 41.0 64.4 Ephennrals 0 10.5 0.0 18.4 Litter 30.4 15.0 54.7 8.5 Abutilm lnlophilum 0 0 0 1.0 AsUeblaWfinab 0.4 1.0 1.3 1.2 Atriplex vesicaría 3.3 4.2 2.5 1.6 An e n oærpa pod o I e p i d i u n 0 0 o.2 0.0 Panicum deæmposiwm 0 0 0 o.2 Po¡tulaaoleraæa 03 0.6 0 o.2 Ptilotus obovatJs 0 o.2 0 '1.8 Salsola l Sporobol u s acti nocl adu s o 0.6 0 0 100 100 100 1q) 256 App. 4.4 Percentage cover of plants (canopy cover), bare ground and litter recorded at Adelaide Yard exclosure. Plot Cattle Proof Conlrol Date 4t3tg'i¿ 24t4193 413ß2 23t4ß3 Percentaoe cover % % % % Annual grass 9.7 0 3.s 0 Bare ground 46.0 48.9 37.7 27.2 Ephennrals 0 o.2 0 o.2 Litter 5.8 40.6 6.6 66.4 Astrebla pectinaâ 0.4 o.2 0 o.2 Atiplex holocarpa 2.2 0.4 1.4 0 Atiplex lindleyi 0 0.8 0 1.0 Atipl ex n u m mulari a ssg. 0 o.2 0 0 omissa Atriplex vesicaña 0 o.2 0 0 D acty I ode n i u m r ad u I an s 21.7 0 37.s 0 Eragrostis setifolia 0 0.6 0 o4 Erodium spp. 0 0.4 0 0 Fran ke n ia s e rpy I I if ol ia 1.3 o.4 0.5 0 Caodenia lasciculañs 0 o.2 0 0 Helipterum charsleyae 2.4 0 3.4 0 lseilemaspp. 0 0 3.0 0 Ix io I ae n a cl'¡l o rol eu æ 0 o.2 0 o.2 lvlaireana aphylla 0 o.2 0 o.2 M¡nur¡a &nt¡culaE 0 1.0 0 0 Portula@oleraæa 2.7 0 4.1 o.2 Cyperus rctundus o.4 0.4 0 0 Sclerolaenaspp. 7.4 4.5 2.3 3.2 S p o robolu s actinocladus 0 0 0 o.2 St e ptog I ossa I ¡atrc ¡ d e s 0 0 0 o.2 Swainsona campylanthe 0 0.6 0 o.4 100 100 100 100 257 App. 4.5 Change in the density (number/2500m2 per plot) of perennial plants after two measurements from Moonland exclosure. Total PoPn Specles Mortallty Recrultment Change ln Dale Popn il: 8ß1 8ß2 Contro! plol Acacia aneun o 0 0 10 10 Aæcialigulaâ 2 0 -2 2 0 Acac¡e tetagonophylla 0 1 +1 0 1 Atriplex vesicaria 1 l0 +9 n æ Crotalaila eremaea 0 6 {6 0 6 Eâgrostis eriopoda 1 0 -1 3 2 lvlaireana astottiche 2 I -1 11 10 Ptilotus obovatus vat. obovetus 0 I +9 0 I Rhagodia spinesæns I 1 0 19 19 Sen na atÞm isioides ssp. 1 I +8 47 55 artemisiohles &nna a¡bmisioi&s ssp. frlifolb 2 -1 I 7 Catlle proof plot Aæcia aneun I 3 -5 t3 18 Acacia ligulab 0 0 0 3 3 Atriplex vesiæria 25 7 -18 113 95 Enclrylaena tomentosa 0 2 +2 0 2 Eragrostis eriopoda 2 0 -2 4 2 Eriachne helmsü 2 0 -2 I 7 lvlairæna astotidta 6 6 0 49 49 Ptilotus obovatus vu. obovatus 0 I +1 I 2 Rhagodia spinescens 5 4 -1 15 14 Sen na atþm isioides ssp. 3 7 +4 24 æ añemisioþ!es Senna arbmisioides ssp. ñlifolh 4 0 4 16 12 Rabblt and Cattle proof plot Aøcia eneun 3 'l -2 21 19 Atriplex vesiania 25 13 -12 1g 12 Crotala¡ia ercmaee 1 27 +â 3 æ Eragrostis eriopoda 2 2 0 11 11 E¡iachne helmsü 3 0 -3 7 4 lllairæna astotricha 5 3 -2 62 60 mbfus obovetus var. obovatus 0 24 +24 0 24 Rhagodia spinesæns 2 6 A 37 41 Senna arÞmisioides ssp. I 1 -7 s7 50 a¡lemisioþles Senna a¡þmisioides frlifol¡e 3 0 -3 46 43 259 App.4.6 Change in the density (number/2500m2 per plot) of perennial plants after two measurements from wyjundi exclosure. Total poPn Spècles Mortallty Recrultment Cñange ln Dale Popn il: 8/91 8ß2 Control p¡ot Acaciaaneun Ð 32 +12 M 56 Acacia letagonophylla I 17 +9 11 æ Enchylaena tomentosa 0 æ +8 0 æ Eragrostis eriopoda 27 95 +68 266 s34 Erenophila gilesü æ 106 r€6 55 '141 Eremqhilalatottd 51 81 +3O 70 f00 Digiadaæeniæla 191 0 -191 195 4 lvbiræna georgei 0 57 +57 0 57 fubnachather paradoxa 19 45 +25 19 ¿tS Rhagodia spinesæns 1 5 +4 3 7 Ølanum ellipticum 0 5 +5 0 5 Cattle proof plot Acacia aneun 6 7 +1 æ 30 Acac¡a tetagonophyila 1 3 +2 4 6 Enclrylaena tomentosa 0 5 +5 1 6 Eragrostis eriopoda 5 30 +25 31 56 Erunophila gilesü 0 74 +74 21 95 Eremqhilalatobei 12 18 {6 ¡tS 51 Digibriaæeniæb 6 0 € 6 0 lvbirænageorçpi 0 96 +96 0 96 lvlon ach ath e r p arad o xa 199 26 -173 28S' 116 Rhagodia spinesæns I 3 +2 4 6 Senna arbm isioides ssp. 0 I +1 0 1 a¡temisiohJes Senna atþmisioides ssp. frlifolia 0 4 +4 0 4 Solanum ellipticum 0 10 +10 0 10 2s9 App. 4.7 Change in the density (number/2500m2 per plot) of perennial plants after two measurements from Pyramid Tank exclosure. Total popn Specles Mortallty Recrullmenl Change ln Date Popn tl: 8¡91 8ß2 Contro¡ plot AsteblaWtinaa 14 319 +305 241 s46 Atriplex vesiæda 103 1s8 +55 558 613 Atripl ex nu m mularia ssp. omtbsa 0 1 +l 0 1 Panicum de@mposltum 0 17 +17 0 17 Sp o robolu s acti nocladus 0 58 +58 0 58 Cattle proof plol Abutilo¡t lnlophilum 0 2 +2 0 2 Astrcbla pectinab 39 187 +148 365 513 Atiplex vesicaria 50 314 +64 1445 1 709 Frankenia serpyllifol h 0 æ +8 æ s4 An e m oørpa pod o I ep i d i u m 0 71 +71 0 71 Panicum deæmpos¡tum 0 47 +47 15 62 S p o ro bo I u s acli n ocl ad u s 0 319 +319 0 319 260 APPENDIX 5 AN EXAMPLE OF PHOTOGRAPHIC CRITERIA FOR THE LAND CONDITION INDEX PASTURE TYPE: 2. LOW WOODLANDS Component (a) Acacia aneura / A. ramulosa (Mulga and horse mulga on deep red sands and dunes). CONDITION CLASS: 3 261 CONDITION CLASS: 2 262