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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ItemPhysiological basis of genotypic variation in plant response to elevated CO2( 2013)The CO2 concentration [CO2] in the atmosphere is increasing and is predicted to double by the end of the 21st century which is likely to have a profound effect on plant growth and yield, especially for C3 plants. Rising [CO2] has direct effect on photosynthesis (A), thus its potential stimulation drives the plant growth and development. However, these responses varied among species but, little is known about the underlying mechanism of genotypic variation in plant response to elevated [CO2]. In this study, wheat (Triticum aestivum L.) was used to test the hypotheses genotypic variation in response to elevated [CO2] exists within the wheat germplasm and if genotypic variability exists, whether it is related to leaf level A and related other traits. Based on above hypotheses, one experiment under glass house and two experiments under Australian Grains Free Air CO2 Enrichment (AGFACE) condition were conducted in the year 2010 and 2011. In experiment 1, seven wheat genotypes were grown at either ambient [CO2] (~384 µmol mol–1) or elevated [CO2] (700 µmol mol–1) in temperature controlled glass houses. Grain yield increased under elevated [CO2] by an average of 38% across all seven genotypes, and this was correlated with increases in both spike number (r = 0.868) and above ground biomass (AGB)(r = 0.942). Across all the genotypes, flag leaf A increased by an average of 57% at elevated [CO2]. The response of A to elevated [CO2] ranged from 31% (in H45) to 75% (in Silverstar). Only H45 showed A acclimation to elevated [CO2] which was characterised by lower leaf maximum RuBisCO carboxylation efficiency (Vc.max), maximum electron transport rate (Jmax) and leaf nitrogen (N) concentration. Leaf level traits responsible for plant growth, such as leaf mass per unit area (LMA), carbon (C), N concentration on dry mass basis (NFLAG LEAF), N content on an area basis (NLA) and the C:N increased at elevated [CO2]. LMA stimulation ranged from 0% to 85% and was clearly associated with increased NLA. Both of these traits were positively correlated with grain yield, suggesting that differences in LMA play an important role in determining the grain yield response to elevated [CO2]. Thus increased LMA can be used as new trait to select genotypes for a future [CO2]-rich atmosphere. In the second experiment, leaf blade elongation rate (LER) and leaf C and N dynamics in expanding leaf blade (ELB, sink) and A, C and N status in the last fully expanded leaf blade (LFELB, source) were determined using two wheat genotypes, Yitpi and H45. Plants were grown at either ambient [CO2] (~384 µmol mol–1) or elevated [CO2] (~550 µmol mol–1) within the AGFACE facility. Elevated [CO2] increased the leaf area and plant total above ground dry mass by 42% and 53% respectively for Yitpi compared to 2% and 13% for H45. Both genotypes showed increased LER at elevated [CO2] which was 36% for Yitpi compared to 5% for H45. In contrast, A increased by 99% for Yitpi at elevated [CO2] whereas H45 showed no change. For both genotypes, a strong correlation (r=0.807) was observed between LER of ELB and soluble carbohydrate concentration in LFELB over diurnal cycle. In ELB, the highest spatial N concentration was observed in the cell division zone, where N concentration was 67.3 and 60.6 mg g-1 for Yitpi compared to 51.1 and 39.2 mg g-1 for H45 at ambient and elevated [CO2] respectively. In contrast, C concentration in the cell division and cell expansion zone of the ELB increased only in Yitpi suggesting that C supply from the LFELB is genotypes dependent and well associated with LER, leaf area expansion and whole plant growth response to elevated [CO2]. In the third experiment, variation in A acclimation to elevated [CO2] at different leaf ontogeny was investigated. Seven wheat genotypes with contrasting growth and yield response to elevated [CO2], Janz, Yitpi, Silverstar, H45, Drysdale, Hartog, and Zebu were grown under rain fed condition at either ambient [CO2] (~384 µmol mol–1) or elevated [CO2] (~550 µmol mol–1) in the AGFACE facility. Leaf gas exchange measurements were conducted at two stages of flag leaf blade development: pre and post-anthesis. Immediately after the gas exchange measurements, flag leaf blade was sampled for biochemical analysis. Vc.max was calculated from gas exchange data to estimate the A acclimation to elevated [CO2]. Genetic variation in A acclimation to elevated [CO2] was observed. H45 showed strong acclimation to elevated [CO2] where Silverstar showed no acclimation. A acclimation to elevated [CO2] was observed only at post-anthesis, which was characterized by both reductions of Vc.max and Jmax. In both stages of the flag leaf, soluble protein concentration was significantly decreased at elevated [CO2]. Nevertheless, association of A acclimation and soluble protein concentration was not significant. In particular, Silverstar showed a large reduction in soluble protein concentration at elevated [CO2] at post-anthesis, but still showed no significant A acclimation (no reduction in Vc.max) to elevated [CO2]. The reductions in total soluble protein content at elevated [CO2] were not similar either between growth stages or genotypes. These findings suggest that A acclimation to elevated [CO2] varied between wheat genotypes but it is not fully associated with changes in soluble protein concentration. In summary, elevated [CO2] stimulated A, growth and grain yield and found large genetic variability of CO2 response. Variation in growth and yield response to elevated [CO2] was closely associated with leaf level traits such as LMA, leaf N and A capacity suggesting that plasticity of leaf level A related traits play a key role in response to elevated [CO2]. Particularly, genotypes showed higher A response to elevated [CO2], also showed increase LER which later translate to biomass and greater grain yield under elevated [CO2].
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ItemThe feasibility of adopting 1-year-old lambing systems in commercial Merino flocks of south eastern Australia( 2013)This study tested the hypothesis that under ‘best-practice’ management, lambing Merino ewes as 1-year-olds can be more profitable than maiden lambing as 2-year-olds. The study comprised 3 major research components: 1. The use of production system modelling to investigate additional inputs required in 1-year-old lambing systems; 2. An economic analysis of 1-year-old lambing system adoption and risk analysis based on modelled outputs; and 3. Commercial trials of 1-year-old lambing systems to assess reproductive performance as 1-year-olds and impacts on performance at subsequent joining. The modelling tool GrassGro® was used to predict additional supplementary feeding requirements of 1-year-old lambing systems when managed according to ‘best-practice’ live weight profiles. Model simulations included 3 production locations in south eastern Australia and additional simulation variables at each location including: 2 pastures types (Typical and Lucerne-based); and 3 stocking rates (‘low’, ‘moderate’ and ‘high’). All production systems were modelled over 40 years based on historical climatic records at each location. Across the 18 equivalent production systems modelled, mean supplementary feed requirements were between 24 and 116 kg greater per replacement ewe in 1-year-old lambing systems compared with conventional 2-year-old lambing systems. The greater supplement requirements were also associated with larger variation in annual quantities indicating higher production risk in 1-year-old lambing systems. Annual Marginal Rates of Return (MRR) were calculated for 1-year-old lambing system adoption based on the simulated outputs of modelled systems. A broad range of production/price scenarios were investigated including: supplementary feed price ($150, $250 and $350/t as-fed); weaner lamb value ($40, $60 and $80/head net); and 1-year-old ewe weaning rates (0.3, 0.5 and 0.7 lambs per ewe joined). Across equivalent production systems, annual MRR from 1-year-old lambing system adoption ranged from -80 to >1000% for the various production/price scenarios tested. To assess the risk of system adoption, the proportion of years that investment in 1-year-old lambing exceeded Target Rates of Return (TRR) of 16% and 50% was determined. Probability of achieving 16 and 50% TRR was highly sensitive to altered production/price scenarios, although between production systems there were large differences in their capacity to maintain high levels of probability. Probability of achieving TRR in Hamilton production systems were generally more resilient to increases in supplementary feed price and reductions in weaner lamb value and weaning rate. Low stocking rate Lucerne pastures had consistently higher probability of achieving TRR, while high stocking rate Lucerne pastures generally generated the lowest probabilities compared with other production systems at each location. Commercial trials of 1-year-old Merino lambing systems were undertaken to evaluate ewe reproductive capacity at first and subsequent joining when managed to ‘best-practice’ guidelines. Reproductive performance of commercial Merino ewes at first joining (8-9 months of age) included lamb marking rates of 72 and 75%. Pregnancy scanning rates following subsequent joining (19-20 months of age) were 131 and 132%. At one trial site pregnancy scanning results were higher in previously pregnant ewes compared with previously non-pregnant ewes (138 v. 118%), while at the other site they were lower (129 v 144%). Interviews with trial site producers were also conducted to gain first-hand insight into management issues with 1-year-old lambing systems, perceived benefits, costs and business risks. Modelling of 1 and 2-year-old lambing systems in this study suggests that given the right combinations of lamb value, supplementary feed price and reproductive performance, adoption of 1-year-old lambing systems has a high probability of generating increased annual profits across a range of production locations in south eastern Australia. The analysis also suggests that pasture type and stocking rate prior to 1-year-old lambing system adoption will have a strong bearing on the likelihood of improved profits. Commercial trials of 1-year-old lambing systems provide evidence that weaning rates in excess of 70% are possible in Merino ewes joined at 8-months-of-age in natural breeding programs. There were conflicting results on the effects of pregnancy on reproductive performance at subsequent mating which may be attributable to live weight differences between ewe groups at each site. On the balance this study supports the view that lifetime productivity of ewes should not be compromised by lambing as 1-year-olds provided ewes achieve appropriate body weights by subsequent joining.
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ItemEffects of ultrasonic interventions on lipid oxidation in whey( 2013)The main objective of this study was to investigate the effect of ultrasonication on lipid oxidation in whey and its shelf stability. Influence of frequencies (20-2000 kHz), specific energies (8-300 kJ/kg) and ultrasound (US) processing times (10 and 30 minutes) was studied in detail. Trials were carried out using a single transducer configuration in a 1 litter acoustic chamber. Treatments were performed at 20, 400, 1000 and 2000 kHz for 10 and 30 minutes at 37 ºC. Depending on the power delivered to the transducers and treatment times, specific energy uptake ranged between 8-390 kJ/kg. Headspace analysis, free fatty acid (FFA) determination, polar lipid quantification and free radical formation were key analytical measurements performed to characterise whey lipid composition and assess the oxidative damage. Generation of free radicals in purified water matrix media (Milli-Q grade) as a result of ultrasonication was highest between 400 and 1000 kHz. Oxidative volatile compounds were initially detected at low concentrations in raw liquid whey samples prior to pasteurisation/sonication treatment. Thermal processing resulted in a significant increase in the concentration of ketone and aldehyde volatiles (P<0.05). This trend was carried on irrespective of whether samples were sonicated for extended period of time or not. Regardless of the concentration of free radicals developed in the system (0.34-110 μM); ultrasound treatment time did not generate additional oxidative odorant compounds. Concentration of all oxidative volatiles except for Hexanal and 2-E-Hexanal during treatments remained considerably below threshold values for human detection (P>0.05). Thermal and ultrasonic treatments applied did not significantly (P>0.05) affect the abundance of polar lipid (Posphatidyle ethanolamine, serine, inositol, choline and sphingomyelin species). Free fatty acids concentration in raw whey samples was initially low but increased significantly after thermal treatment and incubation for 10 and 30 minutes (P<0.05). This could be due to enzymatic hydrolysis of triglycerides and phospholipids. Sonication at various conditions did not significantly (P>0.05) affect FFA concentration in comparison to control samples. A secondary objective of this work was to evaluate the potential of high frequency ultrasound to separate fat from whey. Fresh whey was treated at 400 and 1000 kHz at different power input and durations (50%-100%, 5-30 minutes) to evaluate US potential for fat separation and extending whey shelf life. US treatment at 1000 kHz was more efficient to enhance fat separation. The volatile compound concentration was significantly reduced after the ultrasound separation of fat. The current study suggested that ultrasonication at selected frequencies and selected specific energies did not enhance oxidative reactions in whey more than interventions caused by conventional thermal processing. In addition, high frequency ultrasound demonstrated to enhance fat separation from whey without having an impact on whey composition and stability.
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ItemTactical choices of medium and high input dairy systems( 2013)In the last decade dairy farms in northern Victoria were exposed to increased volatility of input and output prices as well as variable climate conditions that include a big dry period. Two representative case study pasture based dairy farms of ‘medium’ and ‘high’ input were selected to examine the production and financial outcomes that arise from a multi-year sequence of tactical farm management decisions. The approach of the research had several key aspects; case studies were selected as the method of investigation, on-farm interviews of the case study farmers were carried out and their financial and physical history was collected. A stochastic multiyear whole-farm biophysical and economic spreadsheet model was developed to analyse the physical and economical performance of the case study farms. The study found that both farming systems had different optimum choices available year to year to increase profitability. In many of the scenarios tested, the decision option with the highest growth in equity compared to other options tested did not always result in the highest net cash flow. The decision maker would need to evaluate the net cash flow implications of their decisions to determine if they are worthwhile choices. For both farms, in years with greater upside, there was a greater range of outcomes between decisions compared to years with poor financial outcomes. This suggests farm managers cannot get too relaxed and complacent in the good years and need to ensure they are gaining the benefits of the good year as well as minimizing losses in the poor years.
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ItemImproving dairying in Chile: a comparative study with dairying in Australia( 2012)The Chilean Dairy Sector is currently experiencing a period of productive growth which enables it to take advantage of a market opportunity from increasing demand from developed economies. Consequently, most members of the Chilean dairy value chain are searching for production improvements in order to transform the sector and create productive and economically efficient industrial conditions to meet global demand. Nevertheless, expectations about the potential competitiveness of the Chilean dairy industry in global markets are divergent, not only because it is an industry in an early stage of development but also because of some key characteristics of the domestic market and the structure of the economy. The Chilean Dairy Sector is currently experiencing a period of productive growth which enables it to take advantage of a market opportunity from increasing demand from developed economies. Consequently, most members of the Chilean dairy value chain are searching for production improvements in order to transform the sector and create productive and economically efficient industrial conditions to meet global demand. Nevertheless, expectations about the potential competitiveness of the Chilean dairy industry in global markets are divergent, not only because it is an industry in an early stage of development but also because of some key characteristics of the domestic market and the structure of the economy. Based on the diagnosis of the Australian dairy industry this investigation leads to a group of recommendations for the Chilean Dairy Industry oriented to boost production systems, reduce costs of production, improve information flows and contemplate environmental aspects. This is also a broad, mixed research inquiry because it attempts to integrate some macroeconomic and social variables impacting on industry development.
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ItemUse of near infrared spectroscopy to detect non-recoverable collapse caused by tension wood in Eucalyptus globulus( 2012)Eucalyptus globulus is widely planted around the world. The wood is mainly used for fibreboard, paper and firewood. Use for sawn and engineered wood products can be limited because of the development of non-recoverable collapse caused by tension wood, which can severely distort wood surfaces and affect sawing and drying performance, leading to increased processing costs, lower yield (recovery) and thus reduced product value. In tension wood, cellulose content, microfibril angle (MFA), density, and stiffness (MOE) are altered compared to normal wood. The study investigated the calibration and application of near infrared (NIR) spectroscopy to measure these wood properties and detect non-recoverable collapse. Radial, bark to pith, wood cores were sampled from 175 trees in a 20 year old E. globulus silvicultural trial at Tostaree, Victoria, Australia. NIR spectra were measured at 1 mm intervals along the cores after drying to 12% estimated moisture content (EMC). Tangential shrinkage of the cores was measured at 8 points across each core after reconditioning to 12% MC. Spectra were measured on an additional 20 cores that were also analysed using SilviScan-3 to measure MFA, density and MOE, and NIR Partial Least Squares (PLS) Regression calibrations were developed. The calibrations were used to predict wood properties in the 175 cores, which were then related to the measured tangential shrinkage and non-recoverable collapse. NIR-predicted wood properties at points of non-recoverable collapse were consistent with the presence of tension wood (i.e. high cellulose, low MFA, high density and high MOE). Cellulose content and MOE were the best multiple regression predictors of tangential shrinkage. An NIR calibration developed to directly predict tangential shrinkage qualitatively identified zones of high shrinkage, but tended to under-predict measured shrinkage values. Tangential shrinkage, or the incidence of high tangential shrinkage, was not or only weakly correlated with tree size, height to diameter ratio, or lean. Silvicultural treatments (thinning intensity, fertilizer application) did not affect tangential shrinkage or tension wood formation. Generally, the incidence of non-recoverable collapse was greater in the wood grown since age 10 years. The study demonstrated that NIR predicted wood properties can be used to detect non-recoverable collapse caused by tension wood. The methodology has potential use in plantation and log assessment, wood processing, and tree breeding.
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ItemBiosorption of heavy metal cations from water solution using microwave-modified barks of Eucalyptus globulus Labill and Pinus radiata D.Don( 2011)The utilization of bark from Eucalyptus globulus Labill and Pinus radiata D.Don as adsorbents for Cu(II) and Zn(II) in solution was investigated in this study. Analysis of the chemical composition of the two bark species enabled a determination of their potential end use application for heavy metal removal. The higher lignin (49.4%) and extractive (20.5%) content of pine bark as well as the higher hemicellulose (35.7%) content of eucalypt facilitated the use of these barks as suitable adsorbents for heavy metal cations. The release of water soluble extractives (phenolic compounds), however, may impede the use of the barks as metal chelating agents because the leachates may under some circumstances be detrimental to aquatic ecosystems. In order to fix the extractives within the bark and prevent them from leaching, the eucalypt and pine barks were ground, air dried and then heated for 60 seconds using three different microwave power levels to obtain three determined bark temperatures (100, 150 and 200°C). UV spectroscopy showed that the absorbance value of untreated bark at 280 nm was not significantly different from that of the corresponding bark treated with microwave. This was observed for both bark species. This indicates that microwave heating for 1 minute using the three microwave energies examined did not result in any fixation of phenolic compounds within the bark. FTIR spectroscopy, however, indicated the occurrence of chemical bond transformations in various functional groups in bark hemicelluloses and lignin as a result of microwaving. Eucalypt and pine barks were evaluated in a Cu(II) and Zn(II) adsorption study with the following initial treatments: (1) Microwaving to various pre-determined temperatures (100, 150 and 200°C), (2) extracting with water (to remove leachable compounds) and (3) combined processing, incorporating both microwaving and extraction with water. Pressure steamed pine bark, ground pine wood and cotton were examined for comparison. All the samples were analyzed using UV spectroscopy to measure the absorbance value at 280 nm in order to elucidate the leachability of phenolic compounds from the absorbents. Batches of each sample were then soaked in heavy metals solutions (10, 20, 40 mg/L of a single metal element - Cu(II) and Zn(II)). After an hour of shaking, the adsorbent was filtered from the suspension and the solute was analyzed for residual copper using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) to determine the efficiency of each material in binding the metal cations from the solution. The results showed that pressure steamed pine bark and water extracted eucalypt bark exhibited the highest adsorption capacity for Cu(II) and Zn(II) at lower concentrations (10, 20 and 40 mg/L). As observed for eucalypt and pine bark, microwave treated bark generally showed lower uptake capacity compared to the corresponding untreated bark due to their lower reactivity. Microwave treated bark also removed lower amounts of Cu(II) and Zn(II) than those exposed to the combined treatment. Cotton adsorbed the lowest amounts of Cu(II) and Zn(II). This performance was also observed for the bark when in contact with a mixed Cu(II)-Zn(II) solution. At higher Cu(II) concentration (3000 mg/L), there was a change in the performance of the absorbents examined. Untreated eucalypt bark exhibited the highest Cu(II) adsorption (11.1 mg/g), followed by pressure steamed pine bark (10.4 mg/g) and water extracted eucalypt bark (9.2 mg/g). Microwave treated eucalypt bark chelated more Cu(II) compared to the bark subjected to the combined treatment of microwave and water extraction, but this was not observed for microwave treated pine bark. Adsorption equilibrium parameters were generated using the graphical interpretation of the equations of the Freundlich and Langmuir models. On the basis of these models, Cu(II) and Zn(II) adsorption by both bark species were monolayer. The Freundlich isotherm model provided a better fit to the experimental data in describing both Cu(II) and Zn(II) adsorption by both eucalypt and pine barks. The type of metal species did not significantly affect the metal adsorption in the single cation solutions, but in a binary-metal solution, Cu(II) was adsorbed more than Zn(II). Initial concentration of the metal cations in solution influenced adsorption ability of the absorbent examined, in either single or multi metal solutions. Increasing metal concentration in solution increased the uptake capacity and decreased the uptake efficiency of adsorbents. In relation to bark species, eucalypt bark had a higher adsorption capacity than pine bark. Adsorbent particle size did not appear to affect the adsorption process, while adsorbent dosage did. An hour of reaction time was sufficient to reach adsorption equilibrium between the adsorbents and the metal solution. Pressure steam treatment on bark may have resulted in the insolubilisation of leachable compounds of the material, potentially rendering the bark to be more reactive with metal cations. Another possible reason for the improved capture of cations is the absence of leachable extractives. A proportion of leachable extractives had been removed during pressure steaming. The removal of soluble extractives may increase the number of adsorption sites available to heavy metals. Alternatively, steaming may result in the swelling of the bark material, leaving more accessible adsorption sites, thereby improving the adsorption ability of the bark. Water extraction treatment of bark is found to be beneficial for metal adsorption. In addition to the generation of an effective adsorbent for metal cations, water soluble extracts can be isolated for a range of purposes, including tannin adsorbents for heavy metals, proteins and oils, natural additives and a chemical source. This study has shown that eucalypt and pine bark have potential for binding heavy metals. The plentiful availability of eucalypt and pine bark in Australia allows their viable utilization for enhancing water quality in a variety of applications.
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ItemIntegrating traditional ecological knowledge and scientific knowledge to improve conservation planning of gibbons (Hylobatidae) in Lao PDR( 2011)Biodiversity conservation planning and management requires the use of knowledge from a wide range of sources. It also requires an understanding of the beliefs and attitudes towards target species among local people in order to integrate them effectively in planning and management activities. Gibbons (Hylobatidae) are an important species for conservation in Laos. Laos is also generally important for conservation of biodiversity and is part of the Indo-Burma biodiversity hotspot (Myers et al. 2000). For gibbons, Laos holds a significant proportion of the global biological diversity of the family. There is also more intact habitat in Laos than in neighboring range states making Laos a priority for gibbon conservation. This research was conducted to investigate the nature and status of traditional ecological knowledge (TEK) of gibbons in the Nam Kading National Protected Area in central Laos and demonstrate a methodology that would allow the combination of Traditional Ecological Knowledge (TEK) and scientific ecological knowledge (SEK) for improved conservation planning. The research used a broad-definition of TEK and used focus group interviews and comparative case study methodology to investigate TEK in two contrasting villages. Using factors identified from this study and subsequent analysis the research then investigated the utility of Bayesian Belief Networks (BBN) linked to a GIS to incorporate differing knowledge types to build a spatial model and predict gibbon occurrence across the Nam Kading landscape. Results indicated that there was a range of traditional knowledge of gibbons in the region, with more detailed knowledge of specific aspects of gibbon habitat preferences and behavior in the more remote village (Khontao) that had been less subject to outside influence. Knowledge was stronger among males, particularly hunters who had more direct interaction with gibbons. Knowledge in the more accessible village of Kengbit was more anecdotal and less informed on specific aspects of gibbon ecology. Specific knowledge of gibbons and traditional taboos appears to be degrading under new social pressures, but communal knowledge and understanding of gibbons appears more resilient. A comparison of SEK and TEK in a BBN modeling framework indicated that both forms of knowledge share many pieces of common information about the factors affecting gibbon occurrence across the landscape. Models developed using BBN to integrate the two forms of knowledge did not produce sufficiently accurate models of occurrence for conservation planning, however, the BBN approach does have significant benefits in incorporating different data sets, incorporating traditional knowledge, involving local people and promoting a shared understanding of the target conservation species between different stakeholders. It is recommended that this type of modeling be included in adaptive management framework for gibbon conservation in the Nam Kading landscape and more widely in conservation planning and management.