School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemMycorrhizal associations of Prasophyllum R.Br. (Orchidaceae) and the conservation of its threatened species(University of Melbourne, 2010)
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ItemNo Preview AvailableA review of methods used to undertake risk assessments of urban trees(University of Melbourne, 2010)
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ItemEconomic analysis of ameliorating subsoil constraints using subsoil manure in a cropping system( 2019)To date, no studies have accounted for the effects of the yield and/or price risks that will occur over a run of years on the profitability of investing in ameliorating subsoil constraints within a cropping system. While addressing subsoil constraints is likely to increase grain yield, the key economic question for a grower is whether the income from extra grain produced covers the extra costs of ameliorating the subsoil. The focus of this thesis was the likely profit and risk of investing in ameliorating subsoil constraints. Investment costs and annual activity gross margins for a set rotation were used to estimate the economic performance of subsoil amelioration. The marginal change to the gross margin as a result of subsoil amelioration was assessed using partial discounted cashflow budgets. Risk analysis was used to assess the effect of price and yield variability on the mean and variance of outcomes from an investment in ameliorating subsoil constraints in cropping. This study shows an investment in subsoil amelioration was more profitable on average than an alternative investment earning 6% (real). The size of the expected extra yield benefits and longevity of these benefits are the most important factors for a grower to consider when assessing the likely merit (return and risk) of investing in subsoil amelioration in their own situations.
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ItemTree pit stormwater control measures as a tool to improve street tree growth and mitigate the urban stream syndrome( 2018)Cities globally are embracing stormwater control measures (SCMs) to mitigate the environmental damage to urban waterways caused by impervious runoff. Concurrently, efforts are underway to increase urban forest canopy to reduce urban heat and green neighbourhoods. Tree pits are a promising SCM with potential to address both of these issues in dense urban areas. As tree pits may have a small footprint, they allow for implementation without competing for highly-valued space, and may promote tree growth, thus enhancing the benefits provided by the tree. This thesis investigates how effective tree pits may be at reducing runoff and promoting tree growth and which design characteristics drive their performance. A streetscape experiment was conducted, comparing four tree pit designs to a standard street tree planting. Tree growth and runoff retention were measured over an 18-month period and the relationship between the tree pit water regime and tree growth investigated. Tree pits substantially increased tree growth, with median growth in tree pits with an underdrain approximately double that of the standard street tree planting. For tree pits where the tree received stormwater directly at the tree root ball but did not have an underdrain, tree growth was strongly correlated with the soil exfiltration rate. Low exfiltration rates (<20 mm hr-1) resulted in poor growth or death of the tree, whereas pits with higher exfiltration rates showed equal or increased growth compared with the standard street tree planting. A tree pit water balance model was developed and calibrated using the streetscape experiment data to identify tree pit characteristics influencing runoff retention. Sensitivity analysis of the water balance model identified pit exfiltration rate and impervious catchment area as the key drivers of runoff retention. The model was then applied to possible implementation scenarios to explore circumstances where tree pits may achieve meaningful reductions in runoff. For the streetscape experiment scenario, large catchment areas and overall low exfiltration rates resulted in poor runoff retention performance (runoff volume reductions of only 5%). However, if the tree pit area to catchment area ratio was significantly increased (from 0.1% to 4.4%) through increasing tree pit density and tree pit area, and decreasing the catchment areas for each pit, the model suggests that it may be possible to achieve runoff volume reductions of 90% and reduce the frequency of runoff to 15 days per year, returning runoff flows to near pre-development conditions. In practice, achieving significant runoff reductions with tree pits will be most practicable when tree pits are implemented alongside a suite of complimentary SCMs such as rainwater tanks and permeable paving. Such an approach allows tree pits to treat the runoff fromthe public road and footpath surfaces only, requiring smaller tree pits that may integrate into the streetscape without competing for space. This study is the first fully replicated field experiment testing alternative designs for street tree pits. The findings of this thesis highlight that tree pits may increase tree growth and achieve meaningful reductions in runoff and improves understanding of the factors that should be considered in their design.
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ItemThe influence of urbanization on stream temperature regimes( 2017)Streams draining urban catchments are relatively warmer than non-urban streams. Catchment urbanization and subsequent stormwater drainage systems are likely a primary cause of this warming of urban streams, however, the extent of these causes and their relative contribution to the degradation of thermal regimes still remain unclear. Addressing this knowledge gap is important to provide guidelines for thermal regime restoration measures. Stream temperature data were collected continuously at a 15 minute time step from temperature loggers deployed across 82 sites around the city of Melbourne (population ~5 million people), in south-eastern Australia, over a 3 year period. After screening for periods with zero flow and removing logger errors, 53 sites with >80% of good quality data over a >30 month period were selected to calculate a set of temperature metrics that indicate the spatial patterns of thermal regimes (mean, mean daily maximum, mean daily minimum, mean diel change, maximum weekly average temperature, mean summer, mean winter, summer maxima and number of days exceeding threshold levels of 24, and 29C per year). To indicate temporal dynamics, the maximum amplitude of temperature surges during storm events was calculated (a surge was defined as >1 C temperature change recorded over 30 minute intervals). All temperature metrics were then linearly regressed with catchment and climatic variables to identify the main drivers of surges in temperature. The thermal regime of the study streams was also examined with reference to the thermal tolerances of native fish occurring in the region. The majority of streams in the study were unlikely to exceed tolerable temperature limits for most Australian native fish species. Spatial variation in temperature (~88%) were most plausibly predicted by models that included attenuated impervious cover (a measure of urban drainage systems), attenuated forest cover (a measure of riparian deforestation), mean annual discharge volume and mean annual air temperature. Stream temperature surges were observed most commonly after rain events and depending on the antecedent weather, the amplitude of surges was either positive or negative. Positive surges (i.e. increases in temperature) were most commonly observed in autumn, with fewer positive surges in summer than in winter. Negative surges (i.e. decreases in temperature) were most common in spring and summer, and least common in winter and autumn. The variations in the amplitude of negative surges (~74%) were explained by the attenuated imperious cover; however, the drivers of spatial variations in positive surges remained unclear. Surges are small and less common and thus, the potential degradation of stream ecosystem cannot be expected from temperature surges. Therefore, temperature surges were appeared not to be an important aspect of urban stormwater impacts on stream ecosystems in Melbourne water region. The temperature models suggest that increasing the extent of drainage systems and riparian deforestation in future climate change would have a potential to limit thermal habitats suitable for temperature-sensitive fish species. Moreover, riparian reforestation was shown not to be able to overcome the influence of drainage systems.
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ItemFormulating curcumin in a biodegradable polymeric composite material: a step towards wound healing applications( 2017)The natural process of wound healing typically consists of four distinct but overlapping phases which include, hemostasis (platelet aggregation and blood clot formation), inflammation (migration of blood cells), proliferation (angiogenesis or blood vessel formation), and remodelling (reorganisation of collagen and scar tissue formation). However, in diabetic patients, this elaborate well-programmed process becomes disrupted, and there is an urgent need for compounds and formulations that can improve wound healing in these cases. A variety of natural components, including curcumin, have been identified as wound-healing agents. Curcumin, is a yellow hydrophobic natural polyphenolic pigment derived from the rhizomes of the herb Carcuma longa, which has been identified as the active principal of turmeric. The inability to efficiently deliver curcumin in a soluble form presents a chief challenge for its clinical use. Here we characterised, and optimised different biodegradable and biocompatible formulations of curcumin encapsulated particles, in order to enhance the efficiency of curcumin wound healing effect. The size of the optimised curcumin particles ranged from 1286 to 1485 nm, with an encapsulation efficiency of 75%. The zeta potential exhibited values in the range of (-7.2) to (-7.96) with the PDI of 0.4. Physical characterisation using TEM imaging ensured the successful fabrication and encapsulation of curcumin in the polymeric matrix, which had been fabricated in rod shape. Release profile occurred in a biphasic manner including an initial burst, followed by a sustained release trend for curcumin particles. In vitro cytotoxicity assays along with microscopic imaging confirmed safety of the applied concentration of curcumin particles below 25 µg/ml. Moreover, the results of cellular uptake study validated the internalisation of curcumin particles. Overall this thesis, elucidated the developed biocompatible and biodegradable formulations for curcumin encapsulation do have the potential to be employed as a drug delivery vehicle for curcumin. Further validation of the potential of this preparation to enhance wound healing is still needed.
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ItemLivestock performance in a varied landscape and climate( 2016)The sheep and beef industries are significant contributors to Victoria’s economy. Despite competition for land and water resources and an increasingly variable climate, these industries need to continue to increase productivity to remain profitable. As major contributors of greenhouse gases, particularly methane, reducing emissions is also a challenge for these enterprises when considering alternative food and fibre sources. Financial benchmarking, modelling and emission intensity studies seldom recognise that these enterprises are often grazed on diverse landscapes and in the most variable climates, where options for alternative food production are limited. The co-production of meat and fibre from most sheep breeds is often not well recognised and consistently attributed in greenhouse gas emission allocation. This study aimed to investigate whether the relative profitability of a range of sheep and beef enterprises, change across land class and climate. It also aimed to develop measures of and to provide insight into drivers of flexibility, efficiency and profitability leading to guidance on better placed enterprise choice for environment. Four farm case studies were selected to represent climate and land class variability and modelled in GrassGro™. Each farm had one to three land classes enabling eleven ‘farms’ differing in land class over four locations to be simulated. Diversity of land class in this study represented differences in soil type, depth and fertility, slope of land and pasture species. A range of sheep and beef enterprises were tested across all farms to enable comparisons of profitability, flexibility and enteric methane emissions over a forty year period (1970-2010). Enterprise profitability was estimated as net margin per hectare, to allow for labour requirement differences between the enterprises. Flexibility was explored by considering enterprise profit variability and profit response in the top and bottom 10% of years. Strategies that reduced the effects of poor years (higher profit) and increased or did not reduce profitability in good years were considered to have greater flexibility. Enteric methane emissions were calculated in GrassGro™ and an estimation of total end-product made to address the differences in processing stages of red meat and wool, and provide a measure of emission intensity. To further consider the effects of droughts, studies were conducted to quantify commodity price changes in droughts and early warning indicators. A model using total soil water and the Southern Oscillation Index was tested to investigate the potential for predicting droughts before the onset of spring and so provide opportunity for early decision making to mitigate some of the financial impacts of droughts. Wool contributed most to enterprise profitability when pasture production was lowest, as on unimproved pastures, poor soil types and/or in low rainfall years. As pasture production increased across sites and was more reliable, live weight was a stronger driver of profit and systems that had a high proportion of immature animals, tended to perform the best. The specialist meat sheep enterprises were the most profitable when pasture production was highest, but had the highest sensitivity to climate variability. The spring calving enterprise tested in this study was consistently more profitable than the autumn calving enterprise, although the difference was less when pasture production was lowest. These results support, and help to explain, farm financial analyses that have reported enterprise profitability changes between rainfall or regional zones. Where these results did not reflect modelling studies, it was considered to be due to the range in pasture production at the sites tested in this study, as most of the differences were evident at the extremes in pasture production. Most modelling studies in Victoria use sites with high and reliable rainfall, and/or highly productive pastures. Whilst wool production provided a buffer to the susceptibility to droughts, the ability to increase meat production from the system increased flexibility and enterprise profit. For the prime lamb enterprises, a first cross or self-replacing meat enterprise suited to the climate and land class were equally profitable and able to provide options for increased flexibility by feeding and selling lambs early, joining ewes as lambs and running less ewes. Total pasture production, seasonal pasture supply curves as well as replacement ewe turn over price contributed to the most profitable and flexible strategies. The results help to explain some of the inconsistency in the literature on the contribution of strategies to enterprise profit and add to the discussion on the value of increasing reproduction rates. The method for measuring flexibility in this study provides a more quantifiable measure of the term, and addresses factors other than average profitability, of particular relevance to highly variable climates. As with profitability, relative differences in emissions between enterprises were less and/or changed at the sites with the lowest pasture production. As most modelled studies make estimations on fully improved pastures at high rainfall sites, they may overestimate the relative efficiencies of meat specialist systems over wool or dual purpose systems in poorer pasture and land class environments. Research has identified strategies that contribute to lowering emission intensity, such as increased fecundity, improving the feedbase and/or genotype and systems that have a higher proportion of immature stock associated with higher feed efficiency. Consistent with research, these strategies reduced emission intensity but were also most profitable when flexibility rather than profit maximisation was addressed. Therefore the most efficient systems that were also highly profitable tended to be those that maximised returns in good years and reduced the susceptibility to droughts, compared to those that focused on profitability alone. Strategies to do this were not always the same across sites. Analysis of feed and stock prices in recent droughts indicated that steeper price changes occurred from July onwards, compared to other years. Incorporating proportional price changes in drought years in programs like GrassGro™ would allow more realistic analyses of the potential financial implications of drought. Early warning of droughts could provide the opportunity to mitigate losses by using tactical strategies such as selling surplus stock before prices fall and through early purchasing of feed. An explorative study tested triggers of soil moisture and the Southern Oscillation Index which provided reliable indicators of low decile pasture producing springs, with limited risk of above average springs. Further studies are required to test and validate this across more sites and explore the useability for farmers to make informed decisions. The changes in relative profitability, flexibility and emission intensity across landscapes contribute insight into the variability in performance of farm enterprises, within regions and/or when measured as per unit of rainfall. Hence the ability for some farms to attain enterprise profitability achieved by the top 20% of farms based on profitability per mm of rainfall, may not be realistic or achievable. Whilst the industry is currently pushing to increase reproduction rates in sheep enterprises, this study indicates that strategies to do so may vary across enterprise and land class and may not be the most appropriate strategy or profit driver across all farms. More in depth work is needed to identify profit drivers for sheep meat production across land class and environment, particularly in the less reliable pasture production sites. With predictions of increased climate variability, some areas may need to reconsider the suitability of the enterprise for the location and land capability. Similarly, modelling studies that use only sites with high rainfall and improved pastures may not be able to confidently extrapolate results across the wider Victorian environment and may be underestimating emission efficiencies.
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ItemPhysiological and biochemical responses of wheat to combined heat stress and elevated CO2 during grain-filling( 2016)The increase in atmospheric CO2 concentration primarily drives the increase in global temperatures. While the concentration of CO2 has been stable for a long time, it is now rapidly increasing and is expected to reach ~550 ppm by the middle of this century. Concurrent to this, the global temperature is projected to have a 2ºC increase by 2050, a condition that will bring extreme weather events such as heat stress. The interaction of elevated CO2 and heat stress will have profound impacts on future global food production, particularly that of cereals. Wheat (Triticum aestivum L.) is the most important and commonly utilised cereal, and its growth and production will be potentially at risk of any climate-driven changes. CO2 is vital to plant processes and increases in concentration of CO2 have been reported to generate positive impacts in crop yield through increased biomass and improved water-use efficiency, although at the expense of nutritional quality. Heat stress, on the other hand, causes negative effects on crops through reduced phenology and yield reduction. While responses under each individual exposure are relatively well-understood, the interactions between these two climate change factors under field conditions create substantial complexity that is not currently well understood. This study on wheat was conducted at the Australian Grains Free Air CO2 Enrichment (AGFACE) facility using purpose-built heat chambers, simulating actual field condition of future high temperature and elevated CO2 in order to test whether elevated CO2 can potentially ameliorate or aggravate the effects of heat stress, and whether the responses vary within the plant and among cultivars. The first experiment looked into the remobilisation of nitrogen (N) and water-soluble carbohydrates (WSC) during pre-anthesis and grain-filling. Wheat cultivar Yitpi was used and subjected to three heat stress treatments: 5 days before anthesis (HT1), 15 days after anthesis (HT2) and 30 days after anthesis (HT3) under ambient and elevated CO2. Specific traits investigated were net assimilation rates (Anet), stomatal conductance (gs), chlorophyll content (SPAD), flag leaf N and stem WSC concentration and remobilisation, grain N and weight. The second experiment investigated the potential intraspecific differences on the response mechanisms of two wheat cultivars, Yitpi and Scout, as well as the differences between the mainstem and tiller response. Whole wheat plants were harvested and separated into mainstem and tillers; where, physiological parameters such as Anet, gs, SPAD were measured from the mainstem and biochemical analysis of total N concentration and stem WSC concentration were done on both mainstem and tillers. On a mainstem basis, elevated CO2 ameliorated the reduction caused by heat stress on Anet, present during heat stress treatment at pre-anthesis, but with decreasing stimulation after anthesis due to moisture availability. Contributing factors for amelioration effect were improved water-use efficiency and enhanced temperature tolerance of photosynthesis. Inconsistent effect was found for stomatal conductance and flag leaf N remobilisation. Stem WSC concentration was increased by elevated CO2 but decreased by heat stress under both CO2 levels; and this is associated with heat-induced reduction in net assimilation rates. On the other hand, elevated CO2 exacerbated the reduction in properties such as chlorophyll content, stem WSC remobilisation, and grain N concentration, which may lead to even lower grain nutritional quality. Intraspecific variations on the responses to combined heat stress and elevated CO2 of the two cultivars Yitpi and Scout were found in this study. Generally, prior to anthesis, Yitpi performed better than Scout in terms of higher chlorophyll content, N concentration and stem WSC concentration. Scout’s high transpiration efficiency and early vigour leading to efficient water use under heat stress, as well as its enhanced tillering capacity under eCO2, however, was more beneficial in maintaining high stem WSC under environmental variables, particularly before anthesis. After anthesis, when grain-filling is characterised by decreasing water availability, Yitpi showed higher stem WSC than Scout across all environmental conditions, potentially indicating that Scout has already remobilised most of its stem WSC into the grains. Mainstem showed more interactions of treatments as compared with tillers; but tillers also revealed potential to be a source of remobilised stem WSC for the mainstem when it acts as a sink. Interaction results for Anet substantiated the amelioration effect of elevated CO2 in the reduction caused by heat stress; while SPAD results showed further aggravation in the reduction induced by heat stress. This research study provided insights as to the potential responses of wheat crops under future climate condition.
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ItemThe economic viability of automatic milking systems in Australia's pasture-based dairy farm systems: a case study analysis( 2016)Fluctuations in prices, costs and seasonal conditions, and increasing competition will continue to place pressure on profit margins for operators of all dairy systems. Good management and decision making skills is fundamental to ensuring that introducing new technologies, such as automatic milking systems (Mcwilliams et al.), are integrated into the whole farm system to make the best use of a given set of resources and circumstances, and realise the wide array of benefits technology has to offer some people in dairy. Increasing intensity of dairy farms and rising labour costs have helped to induce wider adoption of AMS technology in Europe and other countries. Similarly, the characteristics that have led to the wide adoption of AMS technology are increasingly evident in Australia’s dairy industry. Adapting the AMS technology to Australia’s pasture-based dairy systems has in the recent past been considered a complex challenge and requiring careful implementation as information remains limited on a national and global level. However, in recent years, the knowledge around the adoption of AMS in Australia’s pasture-based dairy systems has increased markedly with the ‘practical operated experience’ of AMS farms being fine-tuned and operating competitively. The key research question to be investigated in this thesis is if AMS technology adopted in Australia’s pasture based systems with voluntary cow traffic is competitive, in terms of profit, returns to capital, risk and non-pecuniary net benefits, when compared to Australian dairy farmers using conventional milking systems. This proposition will be tested by assessing the biophysical and economic performance of two dairy farm case studies, a Gippsland farm using ‘single box AMS’ and a Tasmanian farm using the ‘automatic milking rotary’. These two dairy farm case studies were chosen because they are deemed to have successfully integrated AMS into their whole farm system and are realising the benefits that are available from AMS. The case studies represent the use of the AMS technology at a steady state. For each case study, its biophysical and economic performance for an individual year was compared with the performance of other farmers in the region using conventional milking systems in the same year, where possible, and also over a hypothetical run of years with ranges of prices and seasonal conditions. Risk and uncertainty is also investigated in detail by running scenarios that represent long term typical prices, costs and rainfall. The major finding of this investigation is that the two AMS farms studied in Gippsland and Tasmania are capable, under the current management, of operating competitively under the seasonal and economic conditions that have occurred in the past and are likely to occur in the future, when compared to farms using conventional milking systems in the same region and under the same conditions. Ultimately, the success of incorporating AMS into Australia’s pasture-based dairy systems will depend almost completely on the human element. Good managers can make almost any system work well and profitability.
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ItemThe relationship between social behaviour, feeding behaviour and stress in lambs in intensive finishing systems( 2016)The production of lamb meat is a large and important agricultural industry in Australia. Variability and seasonality of the climate and the demand for a consistent product (in terms of weight and age) have led to an increase in the use of feedlot systems for finishing lambs. An estimated 5-20% of lambs in feedlots are prone to ‘shy-feeding’ or inappetance. Factors considered to contribute to the condition of shy-feeding include: neophobia (environment and concentrated feeds), acidosis and competition around feeding; however, little is known about the individual characteristics of these animals. The aim of this thesis was to examine the relationships between social behaviour, feeding behaviour and stress in lambs in intensive finishing systems. A preliminary study examined relationships between temperament, feeding behaviour, social interactions and cortisol concentrations in lambs in the first 2 weeks in an intensive finishing system (feedlot). Lambs in two 20-lamb feedlots (with 2 m2 floor space/animal) were studied. Prior to entry to the feedlot the lambs were subjected to a temperament test (Isolation Box Test) in which activity was measured. Weight gain, general activity, lying time, time at the feeder, number of feeding bouts, displacement at the feeder and plasma cortisol concentrations in weeks 1 and 2 in the feedlot were recorded. A parsimonious general linear model was developed to relate the logarithm of cortisol concentration to all other measurements. Cortisol was most elevated if the lamb’s activity in the feedlot (number of steps) was low (P=0.000025) and also for those lambs that fed more frequently (P=0.0010). Higher levels of activity in the temperament test were associated with higher cortisol concentrations in week 1 when the lamb was not displaced from the feeder. However there was an interaction with the number of displacements (P=0.0016), leading to little effect when a displacement occurred. A linear model could not be fitted for cortisol in week 2. A second study investigated some individual characteristics associated with shy-feeding. Forty lambs in a feedlot pen were studied in 3 cohorts (120 lambs total) over 16 months. This study focused on the behaviour of lambs in the first week in the feedlot. Lambs were provided with 2 m2 floor space per animal and 4 cm trough length each. Temperament and weights were recorded before entry to the feedlot and weights were recorded again at the end of the first week. Based on total time spent feeding over a 24-h period in week 1, lambs were categorized into two distinct groups: “Shy-feeders” (<30 min feeding, n=22) and “Feeders” (>1 hour feeding, n=98). Accumulated analysis of variance was used to compare entry weights, temperament, growth (live weight change), and feeding behaviour of each group. Most of the Shy-feeders lost weight in the first week whilst most of the Feeders gained weight, however within each grouping there was no relationship between growth and time at the feed trough despite time at the feed trough varying from 1 to 5 h for Feeders. Shy-feeders were displaced less from the feed trough by other lambs than Feeders (P<0.001), but were twice as likely to visit the feed trough when there were no other lambs there (P=0.022). There was no difference between Shy-feeders and Feeders in entry weight (P=0.64) or in any of the recorded measures of temperament (P>0.50). This thesis demonstrates that relationships exist between temperament, behaviour and stress in lambs early in the feedlot. Shy-feeders could clearly be classified by the time spent feeding over a 24-h period in week 1, although measures of temperament and entry live weight were not related to the condition of shy-feeding. A better understanding of these behavioural and stress relationships early in the feedlot may identify strategies to assist vulnerable animals to adapt to feedlots.