Impacts of level of utilisation by grazing on an Astrebla (Mitchell grass) grassland in north-western Queensland between 1984 and 2010. 1. Herbage mass and population dynamics of Astrebla spp.
D. M. Orr A C and D. G. Phelps B
+ Author Affiliations
- Author Affiliations
A Department of Agriculture, Fisheries and Forestry, PO Box 6014, Red Hill, Rockhampton, Qld 4701, Australia.
B Department of Agriculture, Fisheries and Forestry, PO Box 519, Longreach, Qld 4730, Australia.
C Corresponding author. Email: david.orr@daff.qld.gov.au
The Rangeland Journal 35(1) 1-15 https://doi.org/10.1071/RJ11068
Submitted: 17 October 2011 Accepted: 14 February 2013 Published: 8 March 2013
Abstract
Managing large variations in herbage production, resulting from highly variable seasonal rainfall, provides a major challenge for the sustainable management of Astrebla (Mitchell grass) grasslands in Australia. A grazing study with sheep was conducted between 1984 and 2010 on an Astrebla grassland in northern Queensland to describe the effects of a range of levels of utilisation of the herbage at the end of the summer growing season (April–May in northern Australia) on the sustainability of these grasslands. In unreplicated paddocks, sheep numbers were adjusted annually to achieve 0, 10, 20, 30, 50 and 80% utilisation of the herbage mass at the end of the summer over the ensuing 12 months. Higher levels of utilisation reduced both total and Astrebla spp. herbage mass because of the effects of higher utilisation on Astrebla spp. and this effect was accentuated by drought. The tussock density of Astrebla spp. varied widely among years but with few treatment differences until 2005 when density was reduced at the 50% level of utilisation. A major change in density resulted from a large recruitment of Astrebla spp. in 1989 that influenced its density for the remainder of the study. Basal area of the tussocks fluctuated among years, with increases due to rainfall and decreases during droughts. Seasonal rainfall was more influential than level of utilisation in changes to the basal area of perennial grasses. Drought resulted in the death of Astrebla spp. tussocks and this effect was accentuated at higher levels of utilisation. A series of three grazing exclosures were used to examine the recovery of the density and basal area of Astrebla spp. after it had been reduced by 80% utilisation over the preceding 9 years. This recovery study indicated that, although grazing exclusion was useful in the recovery of Astrebla spp., above-average rainfall was the major factor driving increases in the basal area of perennial grasses. Spring values of the Southern Oscillation Index and associated rainfall probabilities were considered to have potential for understanding the dynamics of Astrebla spp. It was concluded that Astrebla grassland remained sustainable after 26 years when grazed at up to 30% utilisation, while, at 50% utilisation, they became unsustainable after 20 years. Results from this study emphasised the need to maintain the population of Astrebla spp. tussocks.
Additional keywords: Astrebla spp., ecosystem processes, pasture dynamics, utilisation.
References
Ash, A. J., McIvor, J. G., Corfield, J. P., and Ksiksi, T. (2011). Grazing management in tropical savannas: utilisation and rest strategies to manipulate rangeland condition. Rangeland Ecology and Management 64, 223–239.| Grazing management in tropical savannas: utilisation and rest strategies to manipulate rangeland condition.Crossref | GoogleScholarGoogle Scholar |
Beale, I. F., Orr, D. M., Holmes, W. E., Palmer, N., Evenson, C. J., and Bowly, P. S. (1986). The effect of forage utilisation levels on sheep production in the semi arid south west of Queensland. In: ‘Rangelands: a Resource under Siege’. (Eds P. J. Joss, P. W. Lynch and O. B. Williams.) p. 30. (Australian Academy of Science: Canberra.)
Bostock, P. D., and Holland, A. E. (2007). ‘Census of the Queensland Flora.’ (Queensland Herbarium, Environmental Protection Agency: Brisbane.)
Burrows, W. H., Orr, D. M., Hendricksen, R. E., Rutherford, M. T., Myles, D. J., Back, P. V., and Gowen, R. (2010). Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 4. Animal production. Animal Production Science 50, 284–292.
| Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 4. Animal production.Crossref | GoogleScholarGoogle Scholar |
Clewett, J. F., Clarkson, N. M., George, D. A., Ooi, S., Owens, D. T., Partridge, I. J., and Simpson, G. B. (2003). ‘Rainman StreamFlow (version 4.3): a Comprehensive Climate and Streamflow Analysis Package on CD to Assess Seasonal Forecasts and Manage Climate Risk.’ (Department of Primary Industries Queensland: Brisbane.)
Cox, D. R. (1972). Regression and life tables. Journal of the Royal Statistical Society. Series B. Methodological 34, 187–220.
Ebersohn, J. P. (1973). Environmental limitations and their role in stability of low rainfall grazing lands. A case history and viewpoint. In: ‘Proceedings III World Conference on Animal Production’. pp. 2(d): 6–8. (World Conference on Animal Production: Melbourne.)
Everist, S. L. (1964). The Mitchell grass country. Queensland Naturalist 17, 45–50.
Everist, S. L., and Webb, L. J. (1975). Two communities of urgent concern in Queensland: Mitchell grass and tropical forests. In: ‘National System of Ecological Reserves in Australia’. Report No. 19. (Ed. F. Fenner.) pp. 39–52. (Australian Academy of Science: Canberra.)
Fair, J. L., Peters, D. P., and Lauenroth, W. K. (2001). Response of individual Bouteloua gracilis (Gramineae) plants and tillers to small disturbances. American Midland Naturalist 145, 147–158.
| Response of individual Bouteloua gracilis (Gramineae) plants and tillers to small disturbances.Crossref | GoogleScholarGoogle Scholar |
Genstat (2002). ‘Genstat for Windows. Release 6.1.’ (VSN International: Oxford.)
Grubb, P. J. (1986). Problems posed by sparse and patchily distributed species in species-rich plant communities. In: ‘Community Ecology’. (Eds J. M. Diamond and T. J. Case.) pp. 207–225. (Harper and Row: New York.)
Hall, T. J., and Lee, G. R. (1980). Response of an Astrebla spp. grassland to heavy grazing by cattle and light grazing by sheep in north-west Queensland. Australian Rangeland Journal 2, 83–93.
| Response of an Astrebla spp. grassland to heavy grazing by cattle and light grazing by sheep in north-west Queensland.Crossref | GoogleScholarGoogle Scholar |
Halls, L. D., and Dell, T. R. (1966). Trials of ranked set sampling for forage yields. Forest Science 12, 22–26.
Hendrickson, J. R., and Briske, D. D. (1997). Axillary bud banks of two semi-arid perennial grasses: occurrence, longevity and contribution to population persistence. Oecologia 110, 584–591.
| Axillary bud banks of two semi-arid perennial grasses: occurrence, longevity and contribution to population persistence.Crossref | GoogleScholarGoogle Scholar |
Hunt, L. P. (2008). Safe pasture utilisation rates as a grazing management tool in extensively grazed tropical savannas of northern Australia. The Rangeland Journal 30, 305–315.
| Safe pasture utilisation rates as a grazing management tool in extensively grazed tropical savannas of northern Australia.Crossref | GoogleScholarGoogle Scholar |
Johnston, P. J., McKeon, G. M., and Day, K. A. (1996). Objective ‘safe’ carrying capacities for south-west Queensland, Australia: development of a model for individual properties. The Rangeland Journal 18, 244–258.
| Objective ‘safe’ carrying capacities for south-west Queensland, Australia: development of a model for individual properties.Crossref | GoogleScholarGoogle Scholar |
Jones, R. M., and Mott, J. J. (1980). Population dynamics in grazed pastures. Tropical Grasslands 14, 218–224.
Jones, R. M., Jones, R. J., and McDonald, C. K. (1995). Some advantages of long-term grazing trials with particular reference to changes in botanical composition. Australian Journal of Experimental Agriculture 35, 1029–1038.
| Some advantages of long-term grazing trials with particular reference to changes in botanical composition.Crossref | GoogleScholarGoogle Scholar |
Jones, P., Filet, P., and Orr, D. M. (2009). Demography of three perennial grasses in a central Queensland Eucalypt woodland. The Rangeland Journal 31, 427–437.
| Demography of three perennial grasses in a central Queensland Eucalypt woodland.Crossref | GoogleScholarGoogle Scholar |
Jozwik, F. X., Nicholls, A. O., and Perry, R. A. (1970). Studies on the Mitchell grasses (Astrebla F. Muell.). In: ‘Proceedings 11th International Grassland Congress’. Surfers Paradise, Australia. (Ed. M. J. T. Norman.) pp. 48–51. (Australian National University Press: Canberra.)
Lambert, F. J., Bower, M., Whalley, R. D. B., Andrews, A. C., and Bellotti, W. D. (1990). The effects of soil moisture and planting depth on emergence and seedling morphology of Astrebla lappacea (Lindl.) Domin. Australian Journal of Agricultural Research 41, 367–376.
| The effects of soil moisture and planting depth on emergence and seedling morphology of Astrebla lappacea (Lindl.) Domin.Crossref | GoogleScholarGoogle Scholar |
Lauenroth, W. K., and Adler, P. B. (2008). Demography of perennial grasslands plants: survival, life expectancy and life span. Journal of Ecology 96, 1023–1032.
| Demography of perennial grasslands plants: survival, life expectancy and life span.Crossref | GoogleScholarGoogle Scholar |
Lorimer, M. S. (1978). Forage selection studies 1. The botanical composition of forage selected by sheep grazing Astrebla spp. pasture in north-west Queensland. Tropical Grasslands 12, 97–108.
McIvor, J. G., Bray, S. G., Grice, A. C., and Hunt, L. (2010). ‘Grazing Management Guidelines for Northern Australia: Scientific Rationale and Justification.’ Final Report Project B.NBP.0579. (Meat and Livestock Australia: Sydney.)
McKeon, G. M., Brooke, K. D., Carter, J. O., Day, K. A., Howden, S. M., Johnston, P. W., Scanlan, J. C., and Scattini, W. J. (1994). Modelling utilisation rates in the black speargrass zone of Queensland. In: ‘Clean Country, Clean Product, Clear Profit. Working Papers. 8th Biennial Australian Rangelands Conference’. Katherine, NT. pp. 128–132. (Australian Rangeland Society: Cottesloe, WA.)
McKeon, G. M., Hall, W. B., Henry, B. K., Stone, G. S., and Watson, I. W. (2004). ‘Pasture Degradation and Recovery in Australia’s Rangelands: Learning from History.’ (Queensland Department of Natural Resources, Mines and Energy: Brisbane.)
Mott, J. J., Ludlow, M. M., Richards, J. H., and Parsons, A. D. (1992). Effects of moisture supply in the dry season and subsequent defoliation on persistence of the savanna grasses Themeda triandra, Heteropogon contortus and Panicum maximum. Australian Journal of Agricultural Research 43, 241–260.
| Effects of moisture supply in the dry season and subsequent defoliation on persistence of the savanna grasses Themeda triandra, Heteropogon contortus and Panicum maximum.Crossref | GoogleScholarGoogle Scholar |
Orr, D. M. (1975). A review of Astrebla (Mitchell grass) pastures in Australia. Tropical Grasslands 9, 21–36.
Orr, D. M. (1981). Changes in the quantitative floristics in some Astrebla spp. (Mitchell grass) communities in south-western Queensland in relation to trends in seasonal rainfall. Australian Journal of Botany 29, 533–545.
| Changes in the quantitative floristics in some Astrebla spp. (Mitchell grass) communities in south-western Queensland in relation to trends in seasonal rainfall.Crossref | GoogleScholarGoogle Scholar |
Orr, D. M. (1986). Factors affecting the vegetation dynamics of Astrebla grasslands. PhD Thesis, University of Queensland, Brisbane, Australia.
Orr, D. M. (1998). A life cycle approach to population ecology of two tropical grasses in Queensland, Australia. In: ‘Population Biology of Grasses’. (Ed. G. Cheplick.) pp. 366–389. (Cambridge University Press: New York.)
Orr, D. M., and Evenson, C. J. (1991a). Effects of sheep grazing Astrebla grasslands in central Western Queensland III. Dynamics of Astrebla spp. under grazing and exclosure between 1975 and 1986. The Rangeland Journal 13, 36–46.
| Effects of sheep grazing Astrebla grasslands in central Western Queensland III. Dynamics of Astrebla spp. under grazing and exclosure between 1975 and 1986.Crossref | GoogleScholarGoogle Scholar |
Orr, D. M., and Evenson, C. J. (1991b). Effects of a single clipping on the seed production response of Astrebla spp. The Rangeland Journal 13, 57–60.
| Effects of a single clipping on the seed production response of Astrebla spp.Crossref | GoogleScholarGoogle Scholar |
Orr, D. M., and Holmes, W. E. (1984). Mitchell grasslands. In: ‘Management of Australia’s Rangelands’. (Eds G. N, Harrington, A. D. Wilson and M. D. Young.) pp. 241–254. (CSIRO: Melbourne.)
Orr, D. M., and O’Reagain, P. J. (2011). Managing for rainfall variability: impacts of grazing strategies on perennial grass dynamics in a dry tropical savanna. The Rangeland Journal 33, 209–220.
| Managing for rainfall variability: impacts of grazing strategies on perennial grass dynamics in a dry tropical savanna.Crossref | GoogleScholarGoogle Scholar |
Orr, D. M., and Phelps, D. G. (2013). Impacts of level of utilisation by grazing on an Astrebla (Mitchell grass) grassland in north-western Queensland between 1984 and 2010. 2. Plant species richness and abundance. The Rangeland Journal 35, in press.
Orr, D. M., and Silcock, R. G. (2010). The occurrence and causes of episodic recruitment of Astrebla spp. In: ‘Rain on the Rangelands. Proceedings of the 16th Biennial Conference of the Australian Rangeland Society’. (Ed. D. J. Eldridge.) (Australian Rangeland Society: Bourke.)
Orr, D. M., Bowly, P. S., and Evenson, C. J. (1986). Effects of grazing management on the basal area of perennial grasses in Astrebla grassland. In: ‘Rangelands: a Resource under Siege’. (Eds P. J. Joss, P. W. Lynch and O. B. Williams.) pp. 56–57. (Australian Academy of Science: Canberra.)
Orr, D. M., Evenson, C. J., Jordan, D. J., Bowly, P. S., Lehane, K. J., and Cowan, D. C. (1988). Sheep productivity in an Astrebla grassland of south-west Queensland. Australian Rangeland Journal 10, 39–47.
| Sheep productivity in an Astrebla grassland of south-west Queensland.Crossref | GoogleScholarGoogle Scholar |
Orr, D. M., Evenson, C. J., Lehane, J. K., Bowly, P. S., and Cowan, D. C. (1993). Dynamics of perennial grasses with sheep grazing in Acacia aneura woodlands in south-west Queensland. Tropical Grasslands 27, 87–93.
Orr, D. M., Paton, C. J., and Reid, D. J. (2004). Dynamics of plant populations in Heteropogon contortus (black speargrass) pastures on a granite landscape in southern Queensland 1. Dynamics of H. contortus populations. Tropical Grasslands 38, 17–30.
Orr, D. M., Yee, M. C., Rutherford, M. T., and Paton, C. J. (2010a). Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 2. Population dynamics of Heteropogon contortus and Stylosanthes scabra cv. Seca. Crop & Pasture Science 61, 255–267.
| Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 2. Population dynamics of Heteropogon contortus and Stylosanthes scabra cv. Seca.Crossref | GoogleScholarGoogle Scholar |
Orr, D. M., Burrows, W. H., Hendricksen, R. E., Clem, R. L., Back, P. V., Rutherford, M. T., Myles, D. J., and Conway, M. J. (2010b). Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 1. Pasture yield and composition. Crop & Pasture Science 61, 170–181.
| Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 1. Pasture yield and composition.Crossref | GoogleScholarGoogle Scholar |
Partridge, I. J. (2001). ‘Will it Rain? The Effect of the Southern Oscillation and El Nino on Australia.’ Information Series Q101016. (Department of Primary Industries: Brisbane.)
Phelps, D. G. (2006). Controlling Aristida latifolia (Feathertop wiregrass) in Astrebla spp. Mitchell grasslands with fire and grazing. PhD Thesis, University of New England, Armidale, Australia.
Phelps, D. G., and Bosch, O. J. H. (2002). A quantitative state and transition model for the grasslands of central western Queensland. The Rangeland Journal 24, 242–267.
| A quantitative state and transition model for the grasslands of central western Queensland.Crossref | GoogleScholarGoogle Scholar |
Phelps, D. G., and Orr, D. M. (2003). A GIS approach to determining vegetation patterns in small paddocks. In: ‘Rangelands in the New Millennium. Proceedings of the VII International Rangelands Congress’. (Eds N. Allsop, A. R. Palmer, S. J. Milton, K. P. Kirkman, G. I. Kerley, C. R. Hurt, and C. J. Brown.) pp. 98–99. (International Rangeland Congress: Durban.)
Roe, R. (1987). Recruitment of Astrebla spp. in the Warrego region of south-western Queensland. Tropical Grasslands 21, 91–92.
Roe, R., and Allen, G. H. (1993). Studies on the Mitchell grass association in south-western Queensland 3. Pasture and wool production under different rates of stocking and continuous or rotational grazing. The Rangeland Journal 15, 302–319.
| Studies on the Mitchell grass association in south-western Queensland 3. Pasture and wool production under different rates of stocking and continuous or rotational grazing.Crossref | GoogleScholarGoogle Scholar |
Roe, R., and Davies, H. I. (1985). Long-term variation in the density of Astrebla spp. in the Warrego region of south-western Queensland. Tropical Grasslands 19, 87–95.
Sattler, P. S., and Williams, R. D. (1999). ‘The Conservation Status of Queensland’s Bio-regional Ecosystems.’ (Environmental Protection Agency: Brisbane.)
Scanlan, J. C. (1983). Changes in tiller and tussock characteristics of Astrebla lappacea (curly Mitchell grass) after burning. Australian Rangeland Journal 5, 13–19.
| Changes in tiller and tussock characteristics of Astrebla lappacea (curly Mitchell grass) after burning.Crossref | GoogleScholarGoogle Scholar |
Stone, G., Bruget, D., Carter, J., Hassett, R., McKeon, G. M., and Rayner, D. (2007). ‘Pasture Production and Condition Issue. The State of Environment in Queensland: Land.’ (Environmental Protection Agency, Queensland Government: Brisbane.)
Tothill, J. C., Hargreaves, J. N. G., Jones, R. M., and McDonald, C. K. (1992). ‘BOTANAL – a Comprehensive Sampling and Computing Procedure for Estimating Pasture Yield and Composition. 1. Field Sampling.’ CSIRO Australia Division of Tropical Crops and Pastures, Tropical Agronomy Technical Memorandum No. 78. (CSIRO: St Lucia.)
Turner, E. J., and McDonald, W. J. F. (1993). Land systems. In: ‘Western Arid Region Land Use Study – Part V’. Technical Bulletin No. 30. (Eds E. J. Turner, W. J. F. McDonald, C. R. Ahern and M. B. Thomas.) pp. 139–158. (Queensland Department Primary Industries, Division of Land Utilisation: Brisbane.)
Williams, O. B., and Roe, R. (1975). Management of arid grasslands for sheep: plant demography of six grasses in relation to climate and grazing. Proceedings of the Ecological Society of Australia 9, 142–156.
Wright, R. G., and Van Dyne, G. M. (1976). Environmental factors influencing semi-desert grassland perennial grass demography. The Southwestern Naturalist 21, 259–274.
| Environmental factors influencing semi-desert grassland perennial grass demography.Crossref | GoogleScholarGoogle Scholar |
