Abstract
paper session 29: Molecular biology - forage quality. In: Proc. XVII International Grassland Congress, pp. 1105-6. Keeling and Mundy Ltd., Palmerston North, New Zealand. United States Department of Agriculture. (1980). Report and recommendations on organic farming. U.S. Government Printing Office, Washington, DC. VanTassel, L. W., Heitschmidt, R.K. and Conner, J.R. (1987). Modeling variation in range calf growth under conditions of environmental uncertainty. J. Range. Manage. 40: 310-4. Walker, B.H. (1993). Stability in rangelands: ecology and economics. In: Proc. XW International Grassland Congress, pp. 1885-90. Keeling and Mundy Ltd., Palmerston North, New Zealand. Walker, J.W. (1994). Multispecies grazing: the ecological advantage. Sheep Res. J. Special Issue: 52-64. Walker, A.B., Frizelle, J.A. and Morris, S.D. (1994). The New Zealand policy framework for sustainable agriculture and some implications for animal production research. Proc. N. Z. Soc. Anim Prod. 54: 369-72. Walker, J.W., Heitschmidt, R.K., DeMoraes, E.A., Kothmann, M.M. and Dowhower, S.L. (1989). Quality and botanical composition of cattle diets under rotational and continuous grazing treatments. J. Range Manage . 42: 239-42. Whitson, R.E., Heitschmidt, R.K., Kothmann, M.M. and Lundgren, G.K. (1982). The impact of grazing systems on the magnitude and stability of ranch income in the Rolling Plains of Texas. J. Range Manage .35: 526-32. Wight, J.R. and Hanson, C.L. (1993). Simulation models as decision aids for management of rangeland ecosystems. In: Proc. XVII International Grassland Congress, pp. 770-1. Keeling and Mundy Ltd., Palmerston North, New Zealand. Wilson, A.D., Harrington, G.N. and Beale, I.F. (1984). Grazing management. In: Management of Australia's rangelands (Eds G.N. Harrington, A.D. Wilson and M.D. Young) pp. 129-40. Commonwealth Scientific and Industrial Research Organization, Australia. Wood, W.R. and Thiessen, T.D. (Eds) (1985). Early fur trade on the Northern Plains: the narratives of John Macdonnell, David Thompson, Francois-Antoine Laraocque and Charles McKenzie. University of Oklahoma Press, Norman, Oklahoma. Manuscript received 4 April 1996, accepted 30 July 1996. Rangel. J. 18(2) 1996, 216-43 EVALUATING STOCKING RATE IMPACTS IN RANGELANDS: ANIMALS DON'T PRACTICE WHAT WE PREACH A.J. Ash1 and D.M. Stafford Smith2 'CSIRO Division of Tropical Crops and Pastures, PMB, Aitkenvale, Qld 4814 2CSIR0 Division of Wildlife and Ecology, PO Box 2111, Alice Springs, NT 0871 Abstract Stocking rate is the most important management variable affecting productivity and stability in rangelands. In this paper we examine the relevance of stocking rate research to the complex and highly variable ecosystems that make up most rangeland enterprises. We review a number of stocking rate experiments that have been conducted in both rangelands and more intensively grazed, improved pastures and demonstrate a fundamental difference in the nature of the stocking rate - animal production relationship between the two environments. Animal production in rangelands is less sensitive to increases in utilisation rate than in improved pastures, at least in the short to medium time frame of most experiments. These differences can largely be explained by factors relating to the much greater spatial and temporal variability of rangelands such as: inter-annual and seasonal fluctuations in vegetation composition and quality; long-term vegetation changes; and spatial and temporal patterns of diet selection in complex vegetation. Together, these factors limit the application of linear stocking rate models to complex rangeland environments for prediction of animal production responses. We suggest that dynamic simulation models, which incorporate the spatial and temporal variability of rangelands, may be the best way of developing simple but useful management principles for setting stocking rates that are more appropriate than simplified regression relationships.
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