School of Agriculture, Food and Ecosystem Sciences - Theses

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    Predicting redistribution of species and communities under environmental change: Improving the reliability of predictions across time
    Uribe Rivera, David Eduardo ( 2023-04)
    Ecological models used to forecast range change (range change models; RCM) have recently diversified to account for a greater number of ecological and observational processes in pursuit of more accurate and realistic predictions. Theory suggests that process-explicit RCMs should generate more robust forecasts, particularly under novel environmental conditions. RCMs accounting for processes are generally more complex and data-hungry, and so, require extra effort to build. Thus, it is necessary to understand when the effort of building a more realistic model is likely to generate more reliable forecasts. During my thesis, I investigated how explicitly accounting for processes improves the temporal predictive performance and transferability of RCMs. I first identified key knowledge gaps, and the challenges of evaluating temporal predictive performance and transferability. One of the main challenges is the lack of robust metrics to assess predictive performance and transferability. To address this I implemented and tested the use of new emerging tools to enable fair comparisons of predictive performance across samples with varying degrees of imbalance (e.g. species with low and high observed prevalence). I then tested a couple of hypotheses related to whether modelling observational processes explicitly results in better forecasts. In particular, I evaluated under what circumstances the benefits of explicitly accounting for imperfect detection and allowing information sharing across multiple species are retained when the models are extrapolated to generate predictions beyond the training temporal window. The findings should shed light on how to address remaining knowledge gaps, and how to generate more reliable forecasts on species’ responses to global change scenarios.
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    Trees Need Closure Too: Unveiling The Molecular Control Of Wound-Induced Secondary Vascular Tissue Regeneration In Trees
    Karunarathne, Sachinthani Isurika ( 2023-09)
    Trees play a pivotal role in terrestrial ecosystems and are an important natural resource. These attributes are primarily associated with the capacity of trees to continuously produce woody tissue from the vascular cambium, a ring of meristem cells located just beneath the bark between phloem and xylem tissue layers. Long-lived trees are exposed to a myriad of biological and environmental stresses that may result in wounding, leading to a loss of bark and the underlying vascular cambium. This affects both wood formation and the quality of timber arising from the tree. In addition, the exposed wound site is a potential entry point for pathogens that cause disease and may even lead to the death of the whole plant. In response to wounding, trees have the capacity to regenerate lost or damaged tissues at a wound site. Investigating gene expression changes associated with different stages of wound healing reveals complex and dynamic changes in the activity of transcription factors, signalling pathways and hormone responses. This thesis investigated molecular regulators of wound-induced secondary vascular tissue (SVT) regeneration. It summarises current literature on primary and secondary vascular tissues and bark wounds and related revascularisation processes, specifically on genes and hormones. Using this information, eight genes from Eucalyptus, including WUSCHEL RELATED HOMEOBOX 4 (EgrWOX4), Arabidopsis thaliana HOMEOBOX GENE 8 (EgrATHB8), CORONA (EgrCNA), PHABULOSA/PHAVOLUTA (EgrPHX), REVOLUTA (EgrREV), AUXIN RESPONSE FACTOR 5 (EgrARF5), PIN-FORMED 1 and 3 (EgrPIN1 and EgrPIN3) were chosen for subsequent experiments on wound-induced SVT regeneration. During these in-planta experiments, Induced Somatic Sector Analysis (ISSA) was used as a molecular tool to assess promoter activity and gene function of these candidate genes in wild-type stems and those where auxin transport was chemically inhibited. Endogenous auxin (IAA) concentrations were quantified using LC-MS to understand how varying auxin concentrations might be required for proper vascular tissue patterning during various stages of regeneration. Results show that the remaining xylem tissues on the wound surface regenerate all lost tissues in a four-step process. EgrPIN1/3 are expressed in all tissue types, EgrWOX4, EgrARF5 and EgrREV predominantly in cambium tissues and EgrATHB8, EgrCNA and EgrPHX in cambium and xylem tissues. Overexpressing micro-RNA-resistant REV leads to faster regeneration rates, while over-expressing miR166 and chemical inhibition of polar auxin transport leads to slower regeneration rates. Samples from overexpression experiments and auxin inhibition also lead to defects in cell anatomies, arrangement, and organisation. Quantification of IAA levels suggests alternating high and low auxin signalling during different stages of regeneration. Together, this thesis provides novel insights into spatial-temporal expression patterns of the selected molecular regulators and discusses how they relate to our current understanding of vascular cambium formation and xylem differentiation during secondary growth. Based on the findings, I propose a model for wound healing that provides the conceptual foundations for future studies aiming at understanding this intriguing process.
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    The ecology and functionality of spontaneous vegetation on green roofs
    Schrieke, Dean ( 2023-11)
    Green roofs can provide social and ecological benefits in urban areas that lack open space, but their success relies on good vegetation cover. Ensuring sufficient plant coverage on green roofs is often difficult, especially in arid climates, where drought conditions reduce plant survival. Additionally, the high costs associated with constructing and maintaining green roofs often limit their application to wealthier areas, and in less affluent communities their implementation can exacerbate inequalities by driving up property and housing costs. A cost-effective solution is needed to encourage plant cover and make green roof benefits more accessible. Over time and without routine maintenance, the vegetation on green roofs changes as spontaneous plants, commonly viewed as ‘weeds’, colonise and become established. Although this shift might be perceived as a departure from the green roof’s original design intent, these spontaneous species, when forming good cover, could offer benefits such as rainfall retention, habitat provision, and building cooling. Green roofs intercept and retain rainfall in substrates before it is evapotranspired or enters the urban stormwater drainage system. This reduces stormwater volumes and delays and reduces peak flow rates. Rainfall retention is significantly influenced by the type and cover of vegetation. Yet, the specific influence of spontaneous species on green roof rainfall retention are not well understood. Ideally, plants selected for rainfall retention should have high transpiration rates as this will help replenish the substrate's capacity to store water after rainfall. This is often linked to 'fast' traits like rapid growth or large leaf areas. However, 'slow' traits, such as slower growth or lower biomass, are beneficial for plant survival in dry conditions. Since spontaneous plant species can establish and survive on green roofs, they might play a role in rainfall retention. In addition to understanding the contribution of spontaneous plants to rainfall retention, understanding how their traits relate to their drought and water use strategies could also inform better plant selection for non-weedy species on green roofs. Sedum species are commonly used on shallow 'extensive' green roofs and in drier climates may require irrigation during summer to sustain their cover. Yet, the interaction between spontaneous vegetation, Sedum cover, and water availability remains poorly understood. Clarifying this relationship could help reduce maintenance efforts, preserve Sedum cover, or maximise the diversity of spontaneously colonising species. Finally, gaining a deeper understanding of the factors that shape spontaneous plant communities on green roofs globally is crucial due to the significant role vegetation cover and composition play in green roof functionality. These insights can inform better decisions in designing and maintaining green roofs to meet specific ecological or aesthetic goals. This thesis consists of a general introduction (Chapter 1), a literature review (Chapter 2), four experimental data chapters (Chapters 3-6) and a concluding synthesis chapter (Chapter 7) that address the following questions: 1. Can spontaneous vegetation cover help expand green roofs into areas that are funding or space limited, or does the inherent ‘weediness’ of this vegetation type make it an unwelcome addition to urban landscapes? 2. What are the water use and drought resistance strategies of spontaneous green roof plants? Are their traits, such as relative growth rate and leaf size, correlated with their drought tolerance and water consumption, and is there a trade-off between water use efficiency and drought survival? 3. What impact does the presence of existing vegetation cover (Sedum mexicanum) and water availability (irrigation) on a green roof have on the growth, abundance, traits, and diversity of spontaneous plant species on extensive green roofs? 4. Can spontaneous vegetation cover contribute to rainfall retention on green roofs, and how do substrate depth and rainfall patterns affect rainfall retention and spontaneous plant community diversity and composition? 5. How do factors such as roof design, accessibility, maintenance, irrigation, vegetation cover in the surrounding landscape, season, and local climate shape the species richness and functional traits of spontaneous vegetation on green roofs worldwide? In Chapter 2, I reviewed existing research to understand how spontaneous vegetation impacts the social and ecological aspects of green roofs. While some people may view spontaneous plants as undesirable 'weeds’, studies indicate that these plants become more accepted as their coverage on green roofs increases. Spontaneous species, which can grow without needing irrigation or fertilisers, could also lower the costs of green roofs. This would be particularly beneficial in areas with lower socio-economic demographics or without an established green roof industry. Additionally, in hot and dry climates where deeper substrate layers or irrigation are needed for plant survival, spontaneous species can be advantageous as they can grow in thinner soils and regenerate from their seeds. Using spontaneous vegetation based on social and ecological needs could make green roofs more affordable and prevent them from contributing to increased property values and housing costs, thereby helping urban communities become more resilient. In Chapter 3, I conducted an eight-week glasshouse experiment to determine the water use and drought response of nine spontaneous green roof species under well-watered (WW) and water-deficit (WD) conditions. Under WW conditions, higher transpiration was associated with 'fast' traits such as increased biomass, leaf area, and growth rate. A clear trade-off emerged between water use under WW conditions and drought resistance under WD. 'Fast' species, while reducing transpiration by 57-72% and biomass by up to 50% under WD, failed to maintain adequate leaf water content (leaf RWC <90%) to avoid drought stress. Conversely, 'slow' species, with their smaller biomass, used less water in both WW and WD conditions, successfully maintaining their leaf water status and showing greater drought resistance. This diversity in water-use and drought responses among the spontaneous species mirrors the variable conditions on green roofs, suggesting different strategies may be advantageous at different times. Spontaneous species are likely to offer rainfall retention comparable to planted species, particularly where good plant coverage is achieved. In Chapter 4, I conducted a 10-month study to investigate the interaction between planted vegetation cover (Sedum mexicanum) with increasing coverage (0%, 25%, 50%, 75% and 100% cover) subjected to two irrigation treatments (well-watered; WW, or water-deficit; WD). The microcosms were seeded with a mix of 14 species typically found as spontaneous vegetation on green roofs. I measured the abundance, community biomass, and functional traits like specific leaf area (SLA), leaf dry matter content, and relative growth rate, and assessed species and functional richness of the spontaneous vegetation communities. Increasing S. mexicanum cover inversely affected the abundance and richness of spontaneous species but did not significantly impact community biomass or functional richness. The interaction between S. mexicanum cover and irrigation treatment played a key role in determining species richness, with the highest richness observed in WW microcosms devoid of S. mexicanum cover. The biomass of spontaneous plants was greater in WW than WD modules. The SLA of spontaneous communities was significantly higher in WW conditions where S. mexicanum cover was less than 100%. These results suggest that maximising Sedum cover while restricting water availability would likely reduce the abundance, biomass, and diversity of spontaneous vegetation on green roofs. In contrast, green roofs that embrace spontaneous species could benefit from increased water availability via occasional irrigation, leading to a richer and more diverse community. In Chapter 5, I conducted a 100-day rainfall simulation study with green roof modules planted with 14 spontaneous plant species typically found on green roofs in Mediterranean-type climates to determine their rainfall retention. For this study, green roof modules were prepared with either 7 cm (shallow) or 14 cm (deep) substrate layers. These were either left bare or planted with a community of spontaneous species, which achieved approximately 100% coverage before commencement of the experiment. The rainfall simulation consisted of two phases – a 'dry' phase replicating the driest period on record, and a 'wet' phase with rainfall depths based on the highest recorded rainfall percentiles (90th, 95th, and 99th) in Melbourne, Australia. Across 17 rainfall events, I measured rainfall retention, evapotranspiration, runoff initiation time, and soil water content. Additionally, I assessed the spontaneous vegetation cover, and species and functional diversity at the end of each rainfall phase, and biomass at the conclusion of the wet phase. Results showed that during the dry phase, modules with spontaneous vegetation retained 88% of the applied rainfall, irrespective of substrate depth, outperforming bare substrates by 6%. In the wet phase, modules with deep substrates and spontaneous vegetation achieved 30% greater rainfall retention compared to other combinations. By the end of the wet phase, spontaneous vegetation in deeper substrates had 42% higher biomass, 19% greater coverage, and over twice the functional richness than in the shallower substrates. These findings indicate that spontaneous vegetation significantly enhances rainfall retention on green roofs compared to bare substrates and performs similarly to designed plant communities. However, rainfall retention by spontaneous vegetation is contingent upon factors critical for rainfall retention, such as substrate depth and rainfall patterns, and will likely differ in other climates. Finally, in Chapter 6, I gathered data from presence/absence surveys of spontaneous vegetation for 192 green roofs around the world to investigate how green roof design characteristics (including age, surface area, substrate depth, and elevation), pre-existing vegetation, accessibility, maintenance, irrigation, landscape vegetation cover and local climate, shape spontaneous plant communities. Using regression analyses, I evaluated the impact of these variables on species richness. Additionally, I applied a Hierarchical Modelling of Species Communities (HMSC) approach to determine how these factors influence the dispersal and establishment of spontaneous species, focusing on their specific traits. The results indicate that seasonal variation affects the composition of spontaneous communities due to its effects on both dispersal and establishment of spontaneous plant species. Dispersal traits of spontaneous vegetation on green roofs were predominantly influenced by the vegetation cover in the surrounding landscape. Conversely, the establishment of spontaneous plant species was primarily determined by climatic conditions, though green roof design features (such as roof height, accessibility, and maintenance intensity) also shaped spontaneous plant communities. Spontaneous species richness was higher during spring and winter, and in both deeper green roof substrates and older roofs. These findings can help inform the design and maintenance of green roofs to achieve specific ecological goals or aesthetic preferences. This study also highlights the interplay between green roof design choices, maintenance practices, landscape and climate context, and the development of spontaneous vegetation communities. By examining the ecology and functionality of spontaneous vegetation on green roofs this thesis revealed several key findings: 1. Spontaneous species display diverse water use and drought response strategies, with fast growing species using more water but exhibiting greater drought stress under water deficit. 2. The composition and richness of spontaneous green roof vegetation are significantly influenced by vegetation cover (Sedum mexicanum) and water availability (irrigation). 3. Spontaneous species can enhance rainfall retention, performing comparably to traditional green roof plantings. 4. Globally, spontaneous plant communities on green roofs are shaped by a multitude of factors, including roof design, local climate conditions, and the surrounding landscape. Overall, this research suggests that spontaneous vegetation could contribute substantial benefits to green roofs due to their ability to establish on shallow substrates and provide functionality in terms of rainfall retention, habitat provisioning, and building cooling. The insights drawn from this research can be used to guide green roof design to support spontaneous plant communities or apply more appropriate maintenance and irrigation regimes to designed plant communities on green roofs. Embracing spontaneous vegetation cover on green roofs could offer a cost-effective solution, potentially making the benefits of green roofs more accessible and equitable across different urban settings.
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    The role of green roofs as native bee habitat and their potential to provide three-dimensional habitat connectivity in urban landscapes
    Schiller, Julia ( 2023-09)
    With ongoing urbanisation, cities around the world experience a continuing loss of biodiversity habitat. Green roofs have the potential to add crucial habitat on vertical built structures in neighbourhoods where ground-level habitat is lacking. Green roofs are also known to provide additional ecosystem services related to urban heat island mitigation, stormwater capture, and human health and wellbeing benefits. For these reasons, green roof uptake is encouraged in many urban areas and this thesis sets out to understand to what extent green roofs currently function to support biodiversity in the context of Australian cities, such as Melbourne. Despite more than a decade of incentives for installing green roofs in Australian cities, their current extent is largely unknown. However, if cities aim to include green roofs into their biodiversity targets, their abundance, distribution, and typology needs to be understood. Since native bees are essential ecosystem service providers and bees in general are known to be experiencing a global decline, it is of high importance to understand how native bees perceive green roofs as habitat, and to what extent green roofs can help improve functional connectivity for bees in urban landscapes. The three research questions addressed in this thesis are: 1) what is the current distribution, abundance and typology of green roofs in Melbourne and how has this changed over last 20 years; 2) which bee species utilise green roofs in Melbourne, and what are the characteristics of the green roof and surrounding landscape that influence their abundance and richness; and 3) how can we model functional connectivity in a way that captures the 3-D arrangement of green roofs, and what do these models reveal about the role that green roofs play in supporting native bees in dense urban landscapes in Australia? To address the first question, I applied a remote sensing approach to identify and map the location and characteristics of green roofs across 17 of the 30 municipalities in the Melbourne metropolitan area. By 2020, there were 224 green roofs in Melbourne, 56% of which were constructed after 2014, and 65% were located within 5 km of the Central Business District. While these green roofs were recorded across most of the municipalities and included large public green roofs on commercial buildings, or smaller, non-accessible biodiversity green roofs at family houses, 65% formed a distinct green roof typology that is typical of many green roofs in temperate Australian cities. These typical green roofs in Melbourne are located on mid- to high-rise apartment buildings, offer passive recreation for the building residents, and contain approximately 30% vegetation cover mostly comprising of lawn. This is a distinctly different typology of green roof to those that have historically been constructed in cities across Europe and North America and reinforces previous studies which have highlighted that the climatic conditions in south-eastern Australia have an important influence on the types of green roof plantings that can be successfully maintained. Given that the typical green roof in Melbourne is quite distinctive and differs from the types of green roofs that have been studied internationally, my second question sought to understand whether green roofs in Melbourne were utilised by native bees, and how the design and spatial location influenced their composition and abundance. I used the database developed in the previous question to identify 20 green roofs which were surveyed for native bees using a combination of passive and active sampling techniques. During the survey, I recorded a total of 114 individuals belonging to 18 native bee species and 186 individuals belonging to 2 exotic bee species. Using Generalised Linear Models (GLM) and Hierarchical Modelling of Species Communities (HMSC) revealed that the abundance and species richness of bees were positively affected by increasing species richness of flowering plants, the proportion of native flowering plants and the overall floral availability on the green roof. The proportion of impervious groundcover in the surrounding 500 m and the increasing height of a green roof, on the other hand, had a negative effect on bee abundance and richness. Bee surveyed on green roofs were all polylectic, mostly ground-nesting but varied in their body size. Although, native bees were all generalist foragers, most were observed foraging from native plants only. These findings highlight that green roofs do offer valuable habitat, indeed may even play an important role in supporting ground-nesting bees in urban areas as the green roof substrates may remain more open and less compacted than exposed soil at ground level. Having determined that native bees do utilise green roofs as habitat, the final component of my thesis investigated the role that green roofs play in the functional connectivity of 3-D urban landscapes. To address this question, the first step was to develop a 3-D functional connectivity model that represents the reality that green roofs may be isolated from other greenspaces vertically as well as horizontally. This was achieved by combining a habitat suitability model with a combination of least-cost path and graph theory modelling. Partial dependence plots from the habitat suitability model revealed a stepped negative relationship between height of green roof and the probability of occurrence for native bees. This is the first time a non-linear relationship has been recorded and it offers a useful framework to inform the placement of green roofs where biodiversity gain is an intended goal. The 3-D functional connectivity analysis revealed that ground-level greenspaces are highly isolated within the inner city of Melbourne (Scenario 1) but the presence of existing green roofs (Scenario 2) increases the number of patches functionally connected for native bees with short (101 m), medium (205 m) and long (586 m) dispersal ranges. Hypothetically maximising the green roof area across the landscape (Scenario 3) led to an increase in overall connectivity, however, it mostly improved the inter-connectedness between green roofs rather than improving the connectivity of ground-level greenspaces. However, for all the scenarios and native bee dispersal distances modelled, the most important role that green roofs played in connectivity was as additional patches of habitat (dPCintra values of 56 – 92%), followed by local connected networks (dPCflux values of 8 – 44%), but their role as critical stepping stones (dPCconnector) were consistently less than 0.1%. This suggests that while green roofs should continue to be added to support biodiversity of native bees, we need to reframe their role in urban landscapes as they are most likely to be used as a habitat patch, rather than as stepping stones. The findings of this thesis highlight the existence of a distinct typology of green roofs in Melbourne, Australia, provide evidence that green roofs can be important habitat for Australian native bees if offering sufficient floral resources and being located at an adequate height, and that green roofs have higher value in providing habitat than improving connectivity. This new knowledge and the novel 3-D functional connectivity approach can help inform local policies and stakeholders on how to design and where to prioritise new green roof installations if the goal is to create a more biodiversity-friendly urban landscapes.
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    Some critical determinants of goat meat quality
    Ravindranathan, Archana Payyanakkal ( 2023-11)
    Goat meat serves as a major source of meat in developing countries while it is less popular in western countries. Nevertheless, the perceptions about goat meat are changing due to the health benefits of consuming lean meat with reduced fat and cholesterol content. Australia is the largest exporter of goat meat globally. Although there is increasing demand for goats domestically the supply chain is highly inconsistent. There is a significant knowledge gap in understanding the factors influencing goat meat quality and these factors that need to be explored to ensure consistent and better quality goat meat. Therefore, this PhD project was designed to investigate some of the critical factors affecting goat meat quality such as slaughter age, post-mortem ageing, retail storage, muscle type, cooking temperature and electrical stimulation. This PhD thesis consists of three animal experiments and one meta-analysis study. The first experiment compared two age groups (Adult goats, n=12, 2 years of age; Young goats, n=12, 6-9 months of age) of farmed Boer goats. This was a preliminary study to understand the meat quality of goats slaughtered in a commercial plant in Australia. This chapter demonstrated that post-mortem ageing for 14 days could reduce the toughness of goat meat in two age groups of goats. The retail color stability was also assessed from 0 to 10 days on the retail shelf, which was validated using Thiobarbituric acid reactive substances (TBARS) analysis. The second study was a meta-analysis research on the effect of electrical stimulation (ES) on small ruminant meat quality, including sheep, lamb, and goat. The meta-analysis provided statistical evidence of the positive impact of electrical stimulation (ES) on the meat quality of small ruminants. This was evident in terms of ultimate pH, tenderness, increased proteolysis, and elevated colorimetric values. It was observed that pH24 and WBSF showed a decrease in electrically stimulated goat carcasses, compared to non-stimulated carcasses through the forest plots. Overall, the research indicates that ensuring the optimum quality meat in Boer goats involves managing factors from the farm to the abattoir and incorporating considerations such as the ideal age of the animal, post-mortem ageing, and specific cooking methods or temperatures specific to the muscle, should be developed and implemented. The third experiment compared meat quality of three muscles namely, longissimus thoracis et. lumborum, semimembranosus and psoas major, representing different muscle fiber types, to understand the association between fiber type and goat meat quality. The variations observed in the muscle fiber composition and cross-sectional areas (CSA) of type I, IIA, and IIB muscle fibers are reflected in the meat quality of Boer goats. A higher percentage of type I fibers and a lower CSA of all three fibers contribute to reduced toughness in goat meat. This experiment also elucidated the effect of cooking end -point temperature on goat meat quality. Furthermore, the underlying mechanism associating fiber type and cooking temperature has been explained by the protein denaturation at different temperatures in the three muscles using differential scanning calorimetry (DSC). The cooking end-point temperature is a critical factor influencing the quality of cooked goat meat. As the cooking temperature rises, parameters such as WBSF, cooking loss, and volume shrinkage increase, leading to tougher meat. The fourth experiment explored how certain crucial factors, such as intramuscular fat, collagen content, and muscle fiber characteristics, influence the meat quality attributes in two distinct age categories of Boer goats (Adult, n=10, 24 months of age; Young, n=10, 6 months of age). For this study, four muscles, namely longissimus thoracis et lumborum (LTL), semimembranosus (SM), cutaneous trunci (CT) and biceps femoris (BF) were harvested from 20 Boer wether goats. The muscle data obtained will enable well-informed decision-making to improve muscle-specific marketing approaches, aiming to enhance the consumer acceptability of goat meat. Overall, adult goats had a higher type I fiber percentage, but a lower type IIB percentage compared to young goats, and animal age increased the CSA of the fibers in different muscles. Higher type IIB fiber number % and higher CSA were correlated with increased toughness.
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    The Logic of Innovation: How Institutional Logics Shape Innovation in Australian Agriculture
    Kenny, Sean Nicholas ( 2023-12)
    This research aimed to improve how institutional dimensions of innovation in agriculture are described and enhance the understanding of their impact on innovation. By exploring systems perspectives on innovation within industrial and agricultural contexts, I explain how institutions are predominantly defined as functional and structural elements of innovation systems (IS). This demonstrates how innovation has been rendered technical in agriculture, and I argue for an institutional turn to rebalance IS towards the social and political. By applying a new institutionalist lens, I expand on the current view of institutions to define them as socially constructed, recursive, material, symbolic and political. I use this expanded definition to highlight the lack of approaches for institutional analysis in agricultural innovation systems (AIS) and introduce the institutional logics (IL) perspective as a basis for my research design. This research is a case study of the influence IL have on managing nutrient pollution in agriculture. It draws data from two contexts that have grappled with this issue for decades, namely the Australian sugarcane industry and agriculture in the Netherlands. My analysis centred on the discourse surrounding each context, drawing on data from unstructured interviews with 22 innovation actors, 119 submissions to an Australian senate inquiry, and 59 documents. Interviews covered actors in the policy, program management, intermediary and farming practices, while documents included those addressing the cases technical, policy and strategy dimensions. My analytical framework draws on the foundational elements of IL and seeks to describe the interrelationship between problem framing, chosen theories of action and justifications used to legitimise action. This was used to develop an initial position on IL observed in the case. I then used qualitative content analysis of data from two discursive hotspots to explore how IL impact innovation activity and performance. Through this process, I describe a dominant discourse within the Australian context anchored in what I label a scientific logic. While this logic dominates the discourse, another competing logic drives an alternate discourse. This I label the experiential logic, which is characterised by a contrasting relativism that questions every aspect of the scientific logic. This resulted in a polarised problem domain leading to diminished action to address the problem and limited progress towards nutrient pollution targets. In the Netherlands, the discourse revealed a dominant societal logic that frames the problem legally and justifies action on the grounds of human and ecosystem health. This precipitates an instrumental theory of action that continually layers expectations for actors in agriculture around compliance with various standards and limits. Sitting behind this instrumental facade was a social process built over centuries and focused on a pragmatic approach to building consensus. This resulted in a fusion of the instrumental approach to defining what must change with a social process of settling on how to achieve this. The polarisation observed in the Australian case was absent in the Netherlands; however, questions exist as to whether the consensus based approach to decision making can withstand the various social, political and functional pressures facing Dutch society. Synthesis of my findings showed how limited awareness of institutional processes, epistemological divergence and weak legal frameworks contribute to poor innovation performance in the Australian context. These insights demonstrate a divergence from the dominant technical and economic interpretations of innovation performance in agriculture and challenge the functional and structural black box approach to representing institutions within AIS. This has implications for the relative emphasis placed upon institutional analysis within AIS. Subsequently, this highlights the need for innovation actors to engage with the institutional dimensions of innovation if progress is to be made in complex problem domains. I propose an enhanced role for innovation brokers to facilitate this process and a representation of AIS that better captures this institutional turn.
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    Nutritional strategies to alleviate heat stress in pigs
    Le, Huu Hieu ( 2023-07)
    Heat stress is a both current and increasing issue for pig production during summer in tropical and sub-tropical regions. Heat stress compromises pig production by increasing the energy cost for maintenance instead of utilising the energy for growth and reproduction. Moreover, HS increases pig’s health issues by causing oxidative stress, blood acid-base disturbance and compromises the physiological function of multiple organs. Various strategies are used to combat HS in pig production, but the use of nutritional strategies are cost-effective and once developed able to be easily incorporated into a variety of production systems. In Chapter 3, the effects of different HS duration (0, 1, 3, and 7 d) on voluntary feed intake, physiological parameters, haematological properties and gut barrier physiology were determined. The Evans blue dye (EBD) technique was also used to quantify plasma volume and tissue damage characterized by increased EBD extravasation in multiple organs. The results of Chapter 3 showed that HS resulted in respiratory alkalosis over 7 days of HS. Unlike some previous studies, HS did not compromise gastrointestinal barrier function, as evidenced by no change in intestinal integrity coupled with no differences in EBD extravasation. Plasma volume was reduced by approximately 10% on d3 and remained at this level until the end of the experiment. The reduced plasma volume, together with unchanged blood haematocrit and haemoglobin, suggest a dehydrated state of the experimental pigs despite ad libitum access to water. Increased concentrations of EBD in kidneys and pancreas may indicate extravasation in these tissues, indicating increased vascular damage and compromised function. Chapter 4 investigated the effects of betaine and isoquinoline alkaloids on the thermoregulatory response and intestinal barrier function of heat-stressed pigs. The findings from Chapter 4 demonstrated that supplementation with betaine and isoquinoline alkaloids reduced the respiration rate and rectal temperature of pigs exposed to HS, indicating improved thermoregulation. Additionally, isoquinoline alkaloids decreased the colonic permeability of pigs under HS conditions. These results suggest that betaine and isoquinoline alkaloids can mitigate the increased physiological responses and intestinal hyperpermeability induced by HS. Chapter 5 investigated the effects of recombinant superoxide dismutase (rSOD) on oxidative stress, inflammation, and intestinal barrier integrity. The results obtained from the experiment conducted in Chapter 5 demonstrated that HS triggered oxidative stress and inflammation. The administration of rSOD ameliorated the consequences of heat stress by reducing oxidative stress and inflammation. However, neither heat stress nor rSOD impacted intestinal barrier function. The findings of Chapter 5 suggest that heat stress-induced oxidative stress and inflammation can be alleviated by recombinant superoxide dismutase. Chapter 6 investigated the effects of chromium and organic acid supplementation on the blood acid-base balance and gastrointestinal integrity of heat-stressed pigs. The results of Chapter 6 indicated that heat stress increased physiological responses and triggered respiratory alkalosis, and compromised intestinal barrier function, as evidenced by reduced transepithelial electrical resistance (TER) and increased permeability. However, neither chromium nor organic acids had any beneficial effects on thermoregulation, blood acid-base balance, or intestinal barrier integrity. Hot weather in summer increases the risk of heat stress (HS) and is associated with compromised growth performance, meat quality, and economic loss in pig production. Chapter 7 investigated the effects of supranutritional levels of antioxidants (Se and VitE) and organic acids on growth performance and meat quality of finishing pigs in late summer to early autumn. The weather data indicated that the pigs were under thermoneutral conditions for most of the experimental periods and had a low risk of HS. No benefits were observed from antioxidant and organic acid supplementation on the growth performance and meat quality of the pigs, except protein oxidation was reduced with high levels of Se and VitE. These results may be attributed to the cool weather during the experiments. In summary, this thesis has shown that nutritional supplements such as betaine, isoquinoline alkaloids and recombinant superoxide dismutase can alleviate the negative impacts of HS in pigs.
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    Irrigating urban green space as a cooling strategy – impacts on surface energy balance and microclimate
    Cheung, Pui Kwan ( 2023-08)
    Urban green spaces are an important space for physical and social activities in cites. However, people’s willingness to stay in urban green spaces will decrease with increasing air temperature in summer. It is necessary to find strategies to reduce air temperature in urban green spaces. Irrigating vegetation in urban green spaces is a promising cooling strategy. Irrigation can be a sustainable cooling strategy when non-potable water is collected for irrigation through stormwater harvesting and wastewater treatment. Yet, there is a lack of experimental evidence for the cooling effects of irrigating vegetation in urban green spaces. Also, little is known about how much environmental and management factors can influence the cooling effects of irrigation. This thesis identified and quantified the impacts of four environmental and management factors (background climate, daily irrigation amount, irrigation scheduling and weather) that influence the cooling effects of irrigation using field experiments and a computer model. A meta-analysis of the literature and a stepwise multiple linear regression was used to identify the background climate variables that significantly influenced the cooling effects of irrigation. The final regression model suggested that the cooling effect of irrigating vegetation in summer strengthened with increasing background air temperature and weakened with increasing rainfall. A field experiment was conducted in Melbourne, Australia to measure the impacts of irrigating turfgrass with three different irrigation amounts (2, 4 and 7 mm d–1) on the surface energy balance and microclimate of a small green space (36 m2). The differences in the impacts of the three different irrigation amounts were small because a large rainfall brought the soil moisture contents to the same level. Irrigation significantly reduced daytime air temperature and turf surface temperature, but it did not reduce human heat stress. The measured impacts of irrigation on the surface energy balance were small. Another field experiment was conducted in Melbourne, Australia to measure the impacts of three different irrigation schedules (single night-time, single daytime, and multiple daytime irrigation) on microclimate using the same amount of water (4 mm d–1) in a small green space (36 m2). The afternoon mean cooling effects of the multiple daytime irrigation on air temperature and turf surface temperature were significantly stronger than the single night-time and single daytime irrigation. The afternoon cooling effects were measured to strengthen with increasing air temperature, vapour pressure deficit and incoming shortwave radiation. Moreover, the data from this field experiment were used to assess the performance of an urban ecohydrological model, UT&C, in predicting the microclimate of unirrigated and irrigated turfgrass. UT&C was then used to predict the impacts of different daily irrigation amounts (2–30 mm d–1) on the cooling effect of irrigation on air temperature. The cooling effect only strengthened significantly as irrigation amount increased from 2 to 4 mm d–1. This thesis demonstrated that irrigating urban green spaces is an effective strategy to reduce daytime air temperature and turf surface temperature in summer. However, more cooling strategies, e.g., shading, are necessary to reduce human heat stress in urban green spaces in summer.
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    Linking fire, climate, connectivity and animal conservation
    Smith, Amy ( 2023-05)
    Australia’s forests and woodlands have been severely fragmented by agriculture, urbanisation and forestry, resulting in loss of habitat for native species. Habitat loss and fragmentation affect landscape structure, defined as the composition and configuration of land cover types. Species persistence in modified landscapes depends on the landscape structure and the availability of resources, which may be altered through management practices, such as prescribed fire. Fire can be used in the ecological management of many terrestrial ecosystems, where its application or suppression alter habitat structure and the availability and configuration of key resources. Current approaches to ecological fire management do not consider the influence of the surrounding landscape or the effect of fire on animal movement (connectivity) within or among habitat patches. The implications of current fire regimes for long-term population persistence are also overlooked. Connectivity is linked to persistence because it maintains dispersal, gene flow and genetic diversity, helping species combat environmental change and avoid extinction. Incorporating connectivity into fire management will help conserve biodiversity in fragmented landscapes. In my research program I investigated how 1) species richness and mammal community composition and 2) individual species respond to habitat, fire and landscape structure using data from remote-sensing cameras collected in south-eastern Australia. Additionally, I combine fire simulation modelling and connectivity analyses using genetic data to 3) compare future connectivity for two small mammals, yellow-footed antechinus (Antechinus flavipes) and heath mouse (Pseudomys shortridgei) under alternative fire regimes and predicted climate scenarios. These findings will inform an understanding of how fire, habitat and climate influence mammal communities, and species’ distributions, connectivity, and persistence. In Chapter 2, my first data chapter, I evaluate the relative influence of fire (time since fire and fire frequency), vegetation type, land use diversity and annual rainfall on ground-dwelling mammal community composition and species richness. Findings suggest that vegetation type and rainfall have the greatest influence on the mammal community and the vegetation type treeless heath is of great importance to critical weight range mammals. In Chapter 3, I focus on 1) the influence of vegetation structure, fire, and annual rainfall on the occurrence of 18 mammal species in two vegetation types (heathy woodland and treeless heath) at the local and landscape scale and 2) if species’ life history traits influence their responses to local and landscape scale predictors. At the local scale understory complexity influenced the occurrence of nine species in both vegetation types. In the woodland species occurrences were also influenced by annual rainfall and basal area while in treeless heath time since fire and fire frequency were important drivers. At the landscape scale, the extent of mature vegetation was most influential in the treeless heath while fire age-class diversity and the extent of native vegetation was most influential in the woodland. All tested species life history traits (size, diet, nest requirement, mean annual offspring and native status) were found to influence species responses at the site scale while only one trait (mean annual offspring) was found to predict species responses at the landscape scale. In Chapter 4, I combine fire simulations and connectivity analyses to compare future connectivity under four alternative fire regimes (0%, 1%, 2% and 4% of total available area burnt per year) and predicted future climate, for two small mammals, heath mouse (Pseudomys shortridgei) and yellow-footed antechinus (Antechinus flavipes). Genetic modelling found that heath mouse and yellow-footed antechinus considered the early post-fire age class low resistance (high connectivity) and pastural farmland to be high resistance (low connectivity). The results of the simulations suggest that the composition of the future landscape will shift towards more recently burnt vegetation, increasing connectivity for the heath mouse and yellow-footed antechinus. Overall, my research has provided new insights into how vegetation type and structure, fire and landscape structure influence mammal species distributions and contributed new information towards an important knowledge gap; how fire regimes influence animal movement and connectivity. Collectively, the findings will inform how fire regimes may influence species distributions and connectivity for long-term persistence in fire-prone landscapes.
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    Evaluation of Australian industrial hemp hurd (Cannabis sativa L.) as substitute lignocellulosic raw material for ultra-low-density particulate composites
    Fehrmann, Johannes ( 2023-08)
    The growing global demand for wood-based panel products faces significant challenges due to increasing scarcity and disruptions in the supply chains of traditional raw materials. In response to this problem, researchers are investigating the feasibility of agricultural by-products as an alternative source for lignocellulosic fibres. Australia's endorsement of hemp seeds for human consumption in 2017 has sparked a keen interest in hemp cultivation, resulting in a by-product known as 'hemp hurd', which is the xylemic inner core of the plant stem. Due to its low specific gravity and chemical similarities to timber, hemp hurd is an appealing option as a core layer constituent in engineered lightweight composite panels. These panels may be used for ready-to- assemble furniture, cabinetry, and decorative or acoustic wall and ceiling panels in both residential and commercial settings. Additionally, hemp hurd composite panels may be incorporated into prefabricated modular construction systems in response to fire or flood emergencies. However, it was unclear whether the hurd would be compatible with adhesives commonly utilised for engineered wood products and how the hurd would react to a natural modifying agent that had previously been effective in creating environmentally friendly lignocellulosic composites. All ultra-low-density hemp hurd particleboard (ULHPB) was fabricated as single-layer panels with densities ranging from 213 to 309 kg/m3. Decorticated hemp hurd chips (“Frog 1”) from Gippsland, VIC served as the raw material. Three synthetic adhesives were used as binders: bio-epoxy (EPX; Change Climate, SA), phenol-resorcinol- formaldehyde (PRF; Jowat Adhesives, NSW), and emulsifiable methylene-diphenyl- diisocyanate (MDI; Huntsman Polyurethane, VIC), respectively. The fourth panel type was an 'eco-friendly' ULHPB (320 - 338 kg/m3), primarily dependent on auto-adhesion and citric acid, which is free from formaldehyde or petrochemicals. The study aimed to determine the impact of hemp hurd particle dimensions on the physico-mechanical panel performance and identify optimal panel compositions in terms of particle and adhesive contents resulting in ULHPB with satisfactory performance characteristics. Furthermore, a subset of MDI-bonded panels was laminated with sheets of aluminium, Masonite hardboard, and Kraft liner, respectively, to explore the effects of surface reinforcement on the flexural properties. Specimen preparation and assessments of all ULHPB followed AS/NZS 4266.1 (2017) for Reconstituted wood-based panels - Methods of testing. The main assessments included internal bond strength, bending strength and stiffness, screw withdrawal resistance, water absorption, thickness swelling, thickness variability, compression ratio, and panel density. Where applicable, the results were evaluated for compliance with AS/NZS 1859.1 (2017) for Reconstituted wood-based panels - Specifications. Additionally, thermo-chemical analyses were conducted on both the untreated raw hemp hurd and the eco-friendly ULHPB to comprehensively study the characteristics of the raw material and understand the citric acid binding mechanisms. The techniques employed were pyrolysis-gas chromatography-mass spectrometry, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The results demonstrated that certain ULHPB configurations performed very well, considering their homogeneous structure, lack of surface densification, and an exceptionally low-density range. MDI-ULHPB exhibited remarkable dimensional stability, with all configurations passing the AS/NZS 1859.1 thickness swelling limit of 15% after 24h water immersion for moisture-resistant particleboard. Similarly, all MDI- ULHPB configurations with high particle loading and adhesive content surpassed the 0.30 MPa minimum internal bond strength threshold for standard particleboard, irrespective of particle size. The findings also highlighted a significant impact of particle dimensions on various physical and mechanical properties. Moreover, the binder application method and pressing temperature were identified as key factors influencing the overall performance of the produced panels. Nevertheless, the findings showed that the efficiency of raw material utilisation could be enhanced by addressing the adverse effects of smaller particles through the optimisation of processing parameters. The thermo-chemical analyses conducted on both retted and unretted hemp hurd revealed notable structural differences between the raw materials. The analyses also provided evidence of ester linkages in the eco-friendly panels, confirming the bonding mechanism described in previous studies. Additionally, all laminated substrates significantly improved the flexural capacities of the MDI-bonded panels, suggesting that ULHPB using Australian industrial hemp could be a suitable core layer in lightweight sandwich composites. The integration of agricultural by-products, specifically hemp hurd, into engineered building materials presents a promising opportunity to mitigate the depletion of finite timber resources and aligns well with circular economy principles. Moreover, this approach may bolster the cultivation of industrial hemp in Australia, further advancing the environmental and economic sustainability of novel building materials.