School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemOn assessing some of the net effects of IPM(Australian Agricultural and Resource Economics Society, 1996)The potential costs and benefits, private and external, of a shift to Integrated Pest Management (IPM) are considered. A method is developed to estimate the private net returns of IPM in particular farm situations. This method is then applied to compare the financial characteristics of IPM and conventional systems in apple and grain legume production in Victoria. A key finding is that in a 'typical year' of a 'typical operation' the annual net returns of a shift to IPM, in both crops, could be positive. Externalities associated with IPM may be positive or negative depending on the circumstances.
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ItemAn economic evaluation of alternative pest management strategies in Northern Victorian peach orchards(Australian Agricultural Economics Society, 1994)
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ItemThe tax Australia has to have(Australian Agricultural Economics Society, 1994)
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ItemThe decision to invest in lime for acid soils(Australian Agricultural Economics Society, 1994)This study is about how to make long-term farm management decisions effectively when the amount of information available is extremely limited. Long-term decisions rely on judgements of input responses and outcomes which are uncertain or unknown. This is the reality of farm management decision-making. Complex decisions have to be based, in part, on some very ‘soft’ data. Therefore, good decision-making relies on good judgement. Judgement derives from lessons from experience (old information), and from the assimilation of new information generated by analysis of all the available information. In this study, information about liming acid soils in north-eastern Victoria is used, along with farm management information, to generate further information, and thus facilitate the making of some judgements about the economic merit of investing in lime on a particular farm. Soil acidity is a physical phenomenon which has the potential to lower agricultural production and reduce farm profitability. The potential of soil acidity to lower agricultural production has led to it being described as a serious problem for agricultural activities in south-eastern Australia (Coventry 1985; Coventry et. al. 1987a; Cregan 1980; Ellington 1984b; Evans 1991; Helyar et. al. 1990; Reeves and Ellington 1985; and Williams 1980). Making long-term farm management decisions with the limited information which is available requires finding a way to analyse and assimilate the available and new information, and then presenting it in such a way that sound judgements can be made about the likelihood of the possible outcomes actually eventuating. In this study, the standard farm management investment technique discounted cash flow analysis is used. To facilitate making sound judgements about the likelihood of outcomes, a break-even method is developed and applied to the major unknown parameter. The break-even level of the critical factor in the investment provides the decision-maker, who is looking ahead in a world of very uncertain input responses and outcomes, with something concrete on which to focus. Judgements can be formed about the likelihood of this critical level of the critical variable being achieved. The analysis of liming as an investment provides information on the yields required for an investment in lime on the case study farm to break-even, that is, to cover all costs, including the opportunity cost of capital. The judgement made as to whether such yields are achievable will determine whether liming is a worthwhile investment on the case study farm and, implicitly, whether soil acidity is a problem requiring action by the case study farmer at this stage.
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ItemTowards a systems approach for river basin management-Lessons from Australia's largest river(WILEY, 2019-06)Abstract Globally, large river systems have been extensively modified and are increasingly managed for a range of purposes including ecosystem services and ecological values. Key to managing rivers effectively are developing approaches that deal with uncertainty, are adaptive in nature, and can incorporate multiple stakeholders with dynamic feedbacks. Australia's largest river system, the Murray–Darling Basin (MDB), has been extensively developed for shipping passage, irrigation, hydroelectric development, and water supply. Water development in the MDB over the last century resulted in overallocation of water resources and large‐scale environmental degradation throughout the Basin. Under the pressure of a significant drought, there was insufficient water to supply critical human, environmental, and agricultural needs. In response, a massive programme of water reform was enacted that resulted in considerable institutional, social, and economic change. The underlying policy was required to be enacted in an absence of certainty around the scientific basis, with an adaptive management focus to incorporate new knowledge. The resulting institutional arrangements were challenged by a need to generate new governance arrangements within the constraints of existing state and national structures. The ongoing reform and management of the MDB continues to challenge all parties to achieve optimization for multiple outcomes, and to communicate that effectively. As large‐scale water reform gains pace globally, the MDB provides a window of insight into the types of systems that may emerge and the challenges in working within them. Most particularly, it illustrates the need for much more sophisticated systems thinking that runs counter to the much more linear approaches often adopted in government.
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ItemAssessment of environmental flow scenarios using state-and-transition models(WILEY, 2018-08)Abstract Numerous methods have been developed to support the assessment of environmental flow requirements for rivers. Most methods are based around models of hydrologic time series rather than models of the ecological endpoints of interest. Important limitations that arise from this include (1) an inability to represent the state dependency of response to future conditions (i.e. the effects of current ecosystem condition on future condition), (2) the inability to predict ecological states through time under alternative flow regimes and (3) limited sensitivity to compare the differences between flow regimes with similar return intervals of ecologically important events, but different sequencing of those events. Here we outline a simple state‐and‐transition modelling approach to assess differences in ecological responses to alternative sequences of floodplain inundation events in a lowland river system. Our approach explicitly incorporates the state dependency of biotic response to flooding, thereby representing the influences of both antecedent conditions and current condition (in this case population state; good > medium > poor > critical). Our approach thus captures the influence of the entire historical sequence of flow events via a first‐order Markov chain process. We use prior data and expert opinion to determine state transitions for a broad suite of ecological indicators. Despite being implemented with deterministic transitions, and drawing heavily on expert opinion, this approach greatly improves on existing methods used in environmental flows planning, particularly when comparing scenarios with the different sequencing of ecologically relevant flow events. The outputs from these models are testable, and the approach is readily extensible to incorporate probabilistic state transitions and uncertainty, mechanistic links (via increased model complexity) and quantitative measures of population state (e.g. measures of abundance or tree condition). Most importantly, the adoption of such a framework represents a fundamental shift to modelling ecological endpoints rather than relying on just quantifying hydrologic surrogates to compare environmental flow scenarios.
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ItemNo Preview AvailableUsing local knowledge to identify drivers of historic native vegetation change(Modelling and Simulation Society of Australia and New Zealand Inc, 2009-07-17)Research underway with three Catchment Management Authorities in Victoria (Goulburn Broken, North Central and North East) is examining the impacts these bodies have had, and could potentially have, on native vegetation extent and quality (condition) on private land. This paper outlines how local knowledge together with spatial data and ecological information is being used to develop Bayesian Networks (BNs) that show historic changes in native vegetation quality and extent in three regions of northern Victoria since the 1880's. The research is being focused on three case study areas, one located in each partner CMA (Figure 1). Comparison of aerial photography from 1946/7 with contemporary modelled tree canopy cover identified that native vegetation extent has increased or decreased to varying degrees over time and space in each case study areas. Local knowledge elicited from the regional workshops has identified the catalysts of change over time as including episodic events, the viability of the farming industry, demand for 'lifestyle' properties, rabbit control, NRM and Landcare initiatives and policy instruments. Changes in extent and quality of native vegetation varied spatially and temporally across the landscape depending on the presence of remnant native vegetation, land tenure, agronomic potential of the land, historic events (e.g. bushfires), characteristics of the local population and targeted policy instruments. Expansion and intensification of farming between the mid-1950s and the late 1970s was matched by a general decline in the extent of woody native vegetation on private land. A decline in farm profitability from the 1980s to 2006 was associated with declines in farm employment, the number of farmers, population, and businesses and services in small rural towns dependent on agriculture and increases in 'lifestyle' farming around rural towns and regional centres. A general increase in the extent of woody native vegetation on private land was noted over this period by workshop participants. BNs are being used to integrate local knowledge on historic land cover and vegetation change, and its drivers, with analysis of spatial data to capture changes in condition over time (60+ years). The regional workshops have been crucial in developing conceptual understanding of the relationships between external drivers (e.g. climate, market forces), actions (e.g. land clearing, de-stocking, revegetation) and outcomes (e.g. vegetation change). The knowledge and understanding of changes in land use and management and their drivers that was gained from the workshops have been used to refine the influence diagram for the historic vegetation extent and quality BNs, define the details of each variable (e.g. states, key assumptions) and identify key decades to represent in the models.
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ItemCopy number variation in the horse genome.(Public Library of Science (PLoS), 2014-10)We constructed a 400K WG tiling oligoarray for the horse and applied it for the discovery of copy number variations (CNVs) in 38 normal horses of 16 diverse breeds, and the Przewalski horse. Probes on the array represented 18,763 autosomal and X-linked genes, and intergenic, sub-telomeric and chrY sequences. We identified 258 CNV regions (CNVRs) across all autosomes, chrX and chrUn, but not in chrY. CNVs comprised 1.3% of the horse genome with chr12 being most enriched. American Miniature horses had the highest and American Quarter Horses the lowest number of CNVs in relation to Thoroughbred reference. The Przewalski horse was similar to native ponies and draft breeds. The majority of CNVRs involved genes, while 20% were located in intergenic regions. Similar to previous studies in horses and other mammals, molecular functions of CNV-associated genes were predominantly in sensory perception, immunity and reproduction. The findings were integrated with previous studies to generate a composite genome-wide dataset of 1476 CNVRs. Of these, 301 CNVRs were shared between studies, while 1174 were novel and require further validation. Integrated data revealed that to date, 41 out of over 400 breeds of the domestic horse have been analyzed for CNVs, of which 11 new breeds were added in this study. Finally, the composite CNV dataset was applied in a pilot study for the discovery of CNVs in 6 horses with XY disorders of sexual development. A homozygous deletion involving AKR1C gene cluster in chr29 in two affected horses was considered possibly causative because of the known role of AKR1C genes in testicular androgen synthesis and sexual development. While the findings improve and integrate the knowledge of CNVs in horses, they also show that for effective discovery of variants of biomedical importance, more breeds and individuals need to be analyzed using comparable methodological approaches.
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ItemNo Preview AvailableRiparian tree water use by eucalyptus coolabah in the Lake Eyre Basin(Conference Organising Committee, 2006)The Lake Eyre Basin (LEB) is characterised by enormous stream flow variability, low rainfall, saline groundwater and at times saline surface water; conditions that demand flexible tree water use strategies in the riparian zone. In the lower reaches of the Diamantina River, the water sources and extraction patterns of Eucalyptus coolabah were examined using isotope data from xylem, soil water, groundwater and surface water. Additionally, soil chloride and matric potential data were used to infer zones of water availability for root uptake. It was found that despite their elevated salinity, groundwater and soil water formed a large proportion of the transpiration flux, with little contribution from standing pools of surface water. At two sites located on the dry floodplain, the data indicated E. coolabah relied substantially on groundwater with a salinity exceeding 30,000 mgL-1Cl. However, some dilution with fresher soil water was evident at most sites, highlighting the importance of flooding in replenishing soil water. Water extraction primarily occurred in the unsaturated zone where a compromise between salinity and source reliability was required. However, E. coolabah was found to have higher salinity tolerances than previously reported for Eucalyptus species.
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ItemShort-term heat stress and vitamin E supplementation affect carcass weight, mucle omega-6 fatty acid and meat quality in lambs(Elsevier, 2016)The effect of short term-heat stress and -vitamin E supplementation on carcass traits and muscle quality – vitamin E, nutritional value and retail colour of lambs was investigated. Forty-eight lambs (crossbred; 42 ± 2 kg body weight, 7 mo age) were randomly allocated by body weight to one of three groups (n = 16) and fed 3 different doses of Vitamin E and Se. The doses of Vitamin E and Se for control (CON), moderate (MOD), and supranutritional (SUP) diets were 28, 130, 228 mg/kg DM as α-tocopherol acetate and 0.16, 0.66, 1.16 mg Se as SelPlex™ kg/DM, respectively. Lambs were fed for 4 weeks followed by a week of exposure to heat treatment. After 4 weeks feeding in individual pens, including 1 week of adaptation, lambs were moved to metabolism cages for 1 week and allocated to one of 2 heat regimes (8 per feeding group): thermoneutral (TN) (18–21◦C and 40–50% relative humidity) or heat stress (HS) (28–40◦C and 30–40% relative humidity) conditions. Final body weight (P = 0.05, 44.1 vs 46.6 kg) and hot carcass weight (P = 0.01, 21.1 vs 22.5 kg) were significantly affected by diet such that lambs supplemented with SUP levels of antioxidants had a higher FBW and HCW as compared with lambs fed MOD and CON antioxidant diets, respectively. Vitamin E concentration in the longissimus lumborum (LL) muscle tended to be higher in lambs fed moderate or supranutritional levels of antioxidants compared with control lambs and values from all treatments were below the threshold (3.2 mg/kg muscle) for optimal maintenance of retail colour. Vitamin E supplementation also reduced lipid oxidation of aged meat, as assessed by thiobarbituric acid reactive substances (TBARS) formation after 72 h of display. One week of heat stress to lambs significantly increased muscle linoleic acid concentration, which in turn increased total n-6 concentration compared with the control group. Results demonstrate that 4 weeks of vitamin E supplementation or 1 week heat stress might not have been adequate to make significant changes in muscle vitamin E concentration and fatty acid composition, which in turn can influence retail colour stability of meat.