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.