School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemGenetic variation in Eucalyptus regnans F. Muell(University of Melbourne, 2010)Past climate changes and associated range contraction, expansion and introgression events are regarded as major forces shaping the evolution of the genus Eucalyptus. Previous investigations in south-eastern Australia have identified some putative refugia and recolonised areas for tall eucalypt forests during the last glacial cycle but the response of individual species are very little understood and in some regions, the evidence for migration or persistence is completely absent. Here I uncover the response of Eucalyptus regnans and two species (E. delegatensis and E. obliqua) which often occur with it and among all of which there is likely to be introgression. These results have important implications for understanding forest responses to climate change and for current gene pool management. Chloroplast variation in Eucalyptus regnans suggests that in spite of the narrow ecological tolerances of the species and the harsh environmental conditions of the Last Glacial Maximum (LGM), E. regnans was able to persist locally, in or near its current range, often in what would have been unfavourable conditions. Therefore, rather than the waves of recolonisation or long distance dispersal experienced by tree species in much of Europe or North America, E. regnans, with the exception of the Central Highlands region of Victoria in mainland Australia and the central region of Tasmania, does not appear to have migrated great distances. A comparative phylogeographic study of three south-east Australian Eucalyptus species (E. delegatensis, E. obliqua, and E. regnans) with different tolerances, in terms of cold, drought and soils revealed that, despite ecological differences, the three species have responded to past climatic changes in a similar way, by persisting in multiple refugia in similar locations. Inter-specific sharing of haplotypes was extensive, and fixation of shared, regional haplotypes, was more likely in areas postulated as treeless at the LGM. It seems likely that the process of recolonisation, in particular, results in loss of chloroplast diversity within species and interspecific haplotype sharing. A nuclear microsatellite study of range wide variation in E. regnans found a high level of diversity, and, in contrast to the findings from the study on chloroplast variation, a generally low level of geographic differentiation. The findings do not support the hypothesis of a high level of genetic differentiation in the species that was suggested by the chloroplast data and its disjunct distribution. No loss of nuclear diversity was found at locations fixed or nearly fixed for the hypothesised recolonising chloroplast haplotypes. I argue that a loss of diversity at recolonised locations has been offset by hybridisation with, and genetic displacement of a pre existing (species was already present at site), compatible species. Extensive pollen mediated gene flow both during and after recolonisation from E. regnans in refugia may have led to the displacement of a pre-existing species and the homogenisation of nuclear microsatellite allele frequencies but retained the pattern of chloroplast variation from the displaced species. This scenario would explain the maintenance of high nuclear and low chloroplast variation at recolonised locations and the low level of genetic differentiation between recolonised locations and adjacent refugia. These results suggest that E. regnans is a species with a strong phylogeographic structure but a low level of nuclear differentiation. Across the species range there is a complex mosaic of populations with different histories of colonisation, persistence and introgression. Phylogeographic patterns in this study indicate that the major biotic responses of tall eucalypt forest to climatic changes were persistence and resilience. The implications of these findings are discussed in the context of defining gene pool management strategies for E. regnans. They generally support the conservative management objectives of the current seed transfer guidelines for commercial forestry operations in both Victoria and Tasmania: seed should be sourced from the harvested coupe if possible or from nearby stands matched for environment. In the central highlands of Victoria and central Tasmania where there is low between stand differentiation longer distance transfers may be more acceptable provided the environment is matched. In other regions such as East Gippsland where long-term, in situ persistence has resulted in strong differentiation between stands, then transfer of seed over relatively small geographic distances will disrupt the established patterns of evolutionary lineages. Given the evidence of the importance of introgression in E. regnans and its relatives, the current policy of maintaining the pre-existing species mix on regeneration should also assist in preserving the collective adaptive potential of the species at a site.
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ItemCommunity dynamics in natural resource governance : building adaptive management capacity towards ecological sustainability(University of Melbourne, 2010)The aim of the research was to analyze community dynamics and collective action for sustainable natural resource governance in decentralized Indonesia. The research was an ethno-methodology research in which in-depth interview and participant observation were used for data collection. Data analysis was carried out by examining the distribution of narratives provided by the respondents, and by carrying out a thematic analysis in which emerging themes were used to produce a complex and coherent narrative of the discourse found within the case study site. The research aims to explore the various practices of natural resource governance and the complex social relations which influence collective action for the sustainable governance of natural resources. Natural resource governance in modem Indonesia is marked by the tension between the centralized policy strategy of the Suharto period and the reactive strategy of Post-Suharto decentralization. To some extent, decentralization led to devolution of power and opportunities for local resource users to make consequential decisions over the natural resources upon which they depend. However, this approach rested upon the capacity of communities to reach a consensus untainted by local politics, commercial imperatives and traditional power stmctures. Moreover, decentralization had not given the majority access to strategic and structural decision making power. Empirical findings from Tongke Tongke�s mangroves in Sinjai, South Sulawesi, suggest that social institutions and local mles came into play and the people felt honored to protect the resource on behalf of the community. These social institutions took the form of neighborly ties, collective identity, reciprocity and social and ecological responsibilities. Access to Tongke Tongke�s mangroves was not free but governed by local and informal mles to maintain its benefits for the good of the community. The community, through the elders, was determining access and making decisions about management on behalf of them all. Community members acted in a way that benefited the overall good even when they were avowing individual rights. The thesis argued that individuals evolved behavior which was commensurate with their responsibilities, leading to innovative power stmctures which were more locally sensitive and environmentally appropriate. The case study in the village of Tongke Tongke within the Regency of Sinjai suggested a rebuttal of Hardin�s Tragedy of the Commons. In line with Ostrom�s theory, the commons is governed by local and often informal mles which induce behavior that are in line with a collaborative mentality to maintain its benefits for the good of the community. Nonetheless, as suggested by Bookchin and argued in the thesis, collective natural resource governance is also about individuals who resist and accept the shaping of civic collaboration and ecological sustainability. In addition, barriers and enablers for sustainable natural resource governance need to emerge from local contexts; they could not emerge as a consequence of top down devolution alone. Moreover, no preparation of local communities could be made to assume the unintentional consequences of complex power relations. In line with Etzioni�s theory, empirical findings suggest that real power relationships in real resource management contexts can undermine the possibility of democratic and equitable consensus making. The thesis argued that social reciprocity, identity validation and symbolic capital can motivate resource users to behave in line with a collaborative mentality for mangrove protection.
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ItemMaking sense of social research in forestry : an exploration of interactions in an interdisciplinary research process(University of Melbourne, 2010)Many social scientists believe their disciplines bring a critically important perspective to environmental problems (Ewert, Baker, & Bissix, 2004; Lockie, Higgins, & Lawrence, 2001; Reser & Bentrupperbaumer, 2001; Roughley & Salt, 2005). Problems involving natural resource management, particularly competing land uses, are often thought to inherently be social problems. Despite this, social researchers have faced challenges in contributing to solving these problems. A critical challenge is lack of understanding of social science by natural scientists, policymakers and non-academic research partners, such as industry. The complex nature of these problems requires coordination between these stakeholders. Gibbons et al. (1994) have described the trend towards collaborations which involve a broader range of academic and societal stakeholders as a new �mode� of knowledge production. Inroads have been made to understanding how knowledge production occurs in the new �mode�, especially in the area of study focused on interdisciplinary collaboration. Some of this work has specifically focused on collaboration across the �great divide� of natural-social sciences in natural resource management and environmental problem settings (e.g. L�l� & Norgaard, 2005), yet it is still unclear how social scientists can, and do, contribute alongside others. The aim of this study is to understand and conceptualise the processes in which social scientists and others engage to make social research usable. This study uses a narrative ethnographic approach (B. Tedlock, 1991), taking advantage of my position as a collaborator studying collaboration between social researchers and foresters in the Cooperative Research Centre Forestry (CRC) Communities Project based in Australia. Principal methods involved participant-observation over 21 months, detailed field note-taking, interviewing members of the Communities Project, and analysis by renarrating field experiences. Studies of natural-social scientific interdisciplinarity provided the expectation that there would likely be miscommunication, misunderstandings and missed opportunities. Instead, social researchers and industry partners managed to make connections. Social researchers were able to communicate the messages they saw as important (even when these had negative implications for industry partners) while industry partners increased their understanding of the methods, findings and implications of social research. I found that this was facilitated by two interactive processes. The first, I labeled �reframing�. This involved participants engaging in questioning and clarification as well as mutually learning each others� vocabularies and concepts. I labeled a second process �stretchy narratives�, referring to participants� stretching, or expansion of their original narrative to incorporate critical features of others� narratives. These interactive processes constituted integrative practice in this interdisciplinary collaboration, adding to previously abstract conceptualization of integration (e.g. Klein, 2001b; Newell, 2001). Working with industry partners, I redefined the nature of our differences, finding that they were focused on practical measures such as clear project explanations and valuable research outcomes. This, and the lack of obvious �disciplinary� struggle, suggests that in some �interdisciplinary� collaborations, particularly those with non-academic stakeholders, philosophical differences may be less relevant than social scientists have argued (e.g. Eigenbrode et al., 2007). Given the notion that disciplinarians have somewhat fixed epistemological positions, project partners� perspectives were more fluid than anticipated. My research suggests that those working in natural-social science collaborations in environment and natural resource management problem settings can make social research usable by adopting a gradual and incremental approach to educating and learning from others, engaging opportunistically in teaching moments.
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ItemPlacing the native pest in the postcolonial city : the relocation of Melbourne's flying foxes(University of Melbourne, 2010)As long as wildlife inhabits the urban environment, humans will experience interspecies conflicts. And as long as these conflicts occur, questions will be raised about who and what belongs in city places, and what it means to put native pests �in their place�. The ways we deal with animals judged to be �out of place� have effects: not only for the species and spaces involved, but also for our very ideas about these species and spaces, and for our ideas about the place of nature in our postcolonial urban lives. Human interventions with animals matter because they are not only reflective of the socio-spatial order, but productive of it. This thesis, grounded in cultural geography, investigates the way native animals figure in the socio-spatial orderings of the contemporary Australian city. It aims to make an original contribution to animal geography by paying sustained attention to the ways wild animals are placed discursively and practically by humans, and in turn, how those wild animals place themselves. I pursued this research by following the 2003 relocation of Melbourne�s colony of native greyheaded flying-foxes from the Royal Botanic Gardens (RBG) to Yarra Bend Park. I used this case of animal transgression and human intervention to make wider claims about the paradoxical place of the native pest in the postcolonial city. I took an in-depth and interpretive approach to the research, with the aim of providing qualitative, contextualised claims. My methods included: targeted interviews with key stakeholders; participant observation activities; field site visits; news media reviews; and content analysis of key documents and websites. The thesis structure follows the chronological journey of the relocation: from the flying-fox colony�s discursive rejection from the RBG via the Save Our Gardens Campaign; to the determination of the new roosting site by the Grey-headed Flying-fox Alternative Campsite Task Force; the embodied relocation of the flying- foxes across Melbourne; and, finally, the discursive and material work undertaken to accommodate the colony in Yarra Bend Park. The thesis concludes that, while the relocation has set a precedent for dealing with native pests, its supposed success sits in tension with the actual nature of the relocation. The relocation achievement was not as tidy, successful, nor as human as many post-relocation claims suggest. The relocation was constituted by a messy, hybrid process largely shaped by the bats, and resulted in hybrid and unstable outcomes.
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ItemConflicting agendas : illicit drugs, development and security in the Wa special region of Myanmar(University of Melbourne, 2010)This thesis examines the reasons behind the persistent conflict and underachievement in global efforts to control illicit drug production in the South and argues for a new approach. This underachievement is explored through a detailed case study of a remote illicit drug producing area in Myanmar, the Wa Special Region (WSR), and through a comparative examination of the illicit drug problem in Afghanistan. Using extensive field interviews, results from existing quantitative studies and drawing on literature that examines the relationship between security and development, a comprehensive picture is painted that describes the perspectives, motivations and actions of both Northern and Southern actors over time with respect to three key inter-related themes: drug control, security and development. The conceptual framework that is used for the thesis uses security and development research and illicit drug studies to map and analyse conflict in actor policy around these three themes. The thesis makes a number of findings and recommendations. Firstly, new information on an under-researched region, its people and leaders is presented. The WSR is a poorly understood region that has been dependent on illicit opium cultivation and trade for over a hundred years and a more detailed understanding of its history, security concerns and recent actions may assist in future policy development towards the region. Secondly, the thesis argues that, at a relatively localized level, each drug growing region is context specific and the details of local economies and political complexes at this level are often not well understood. This lack of understanding can contribute to project failure or irrelevance of drug control efforts. More consistent progress on the illicit drug control issue requires that the complexity of individual production areas needs to be analysed, particularly local governance structures, the underlying economy and perceptions and actions of local leaders. The thesis also shows that drug control is characterised by conflicting perspectives and actions by local and external actors. Policies are often based on self-interest and may be single-minded in that they ignore the interdependency of drug control, security and development. A general inattention to gathering evidence through research and analysis of the underlying social, economic, political and cultural factors, compounds this conflict and actors are informed by a partial assessment of the drug control problem. Limited interaction between different actors leads to lack of coordination, coherence and opportunities for consensus-building on drug control action and policy, which may adversely impact local populations or the level of drug production. In some cases, local actors may be criminalised by external ones foreclosing opportunities for continuing cooperation and progress. This thesis argues that local actors and governance structures are paramount and must be considered in areas where illicit drug production is to be addressed. Local leaders must be respected and local achievement should be recognised and reinforced. Further, that the security concerns of all actors including local leaders need to be considered and compared as a starting point in any drug reduction programme. The thesis recommends that drug control should be underpinned by evidence-based complexity analysis of drug producing regions that incorporates both local and external actors and be overseen by a single UN body to build consensus. Finally, there must be a concomitant willingness on the part of powerful international actors to share intelligence and to pursue a more cooperative approach to drug control and less unilateralism.
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ItemQuantification and mitigation of gaseous nitrogen emissions from pasture and cropping systems(University of Melbourne, 2010)Due to the application of nitrogen (N) fertilizers and animal excreta agricultural soils emit large quantities of ammonia (NH3), nitrous oxide (N2O) and nitric oxide (NO) to the atmosphere. As well as negative environmental effects, such as contribution to acid precipitation and enhancement of the greenhouse effect, the processes that produce these gases are the main cause of the low efficiency of N fertilizers. A series of field studies were carried out in Australia and China to quantify emissions of NH3, N2O and NO to investigate how farming practices impact on the soil N dynamics responsible for their loss and to recommend strategies to reduce them. A micrometeorological method using a backward Lagrangian stochastic model (bLs) was used to determine NH3 volatilization resulting from grazing a pasture by a herd of dairy cows and from subsequent urea application. Emissions were 4.9 and 1.9 g N cow"1 d"1 in summer and autumn, respectively, with the larger losses in summer due to higher temperatures and evaporation rates. Loss of fertilizer N in summer was 1.2% of applied- N when irrigation followed fertilizer application immediately and 5.3% in autumn when irrigation took place 3 days after application. Measurements of N2O emissions were made with 100 static chambers from an approximately 1 ha area in the same pasture a few days after the sequence of grazing, fertilizer application and irrigation. The key soil physical and chemical properties from under each chamber were analyzed. The N2O emissions were extremely variable, ranging from 45-765 (average 165) ng N m"2 s"1 in the summer and 20-953 (average 138) ng N m"2 s"1 in autumn. Emissions showed spatial dependence up to 73 and 51 m in autumn and summer, respectively, and were significantly correlated with soil nitrate (r2 = 0.79) and ammonium (r2 = 0.41) through the effects of animal traffic in the field, indicating both nitrification and denitrification contributed to N2O emissions. Ammonia loss from fertilizer application to winter cereals in western Victoria was measured following application of urea, ammonium sulfate and urea-ammonium nitrate. Ammonia loss varied with location and fertilizer type and ranged from 1.3 to 23% of N applied. The variation with location seemed to be due to a combination of factors including soil texture, soil moisture when fertilizer was applied and rainfall (how soon and how much) after fertilizer application. Addition of a urease inhibitor [N-(n-butyl) thiophosphorictriamide] to a urea treatment reduced losses by more than 80%. Emissions of NOx and NH3 from a maize crop fertilized by deep-placed urea in northern China were 1.2% and 6.5% of the applied N, respectively. The loss of NOx was far greater than that reported by others, possibly because the measurements were made continuously in this study rather than as spot measurements with static chambers. Soil analyses to depth indicate that little nitrate was leached down the profile and a study using soil cores and acetylene inhibition to measure denitrifying activity suggested that the rate of denitrification was very slow in this soil. The results suggest that in this soil with a slow denitrification rate and little leaching, deep placement of the urea to limit NH3 volatilization is an effective method for decreasing N loss to the atmosphere and increasing fertilizer use efficiency. The soil N dynamics of an irrigated maize system in which stubble retention and stubble burned treatments were superimposed over treatments of varying N fertilizer rate were studied at a site near Whitton, NSW. Field measurements using 15N-labelled urea recovery from microplots with and without the nitrification inhibitor ammonium thiosulfate (ATS), showed significantly more fertilizer N was recovered in the grain from a stubble incorporated treatment than a stubble burned treatment (P < 0.05), and more fertilizer N remained in the soil in the stubble burned treatment. This indicated lower denitrification losses of fertilizer N applied to the stubble burned system. The high N recovery in grain in the stubble incorporated treatment was thought to be due to improved soil structure in the heavy texture soil. Inclusion of 5% ATS in the fertilizer formulation did not appear to have an impact on N recovery of fertilizer N. Nitrous oxide emission was strongly dependent upon fertilizer rate and there was no statistically significant effect of stubble management on N20 emission rate found using static chambers. The effects of soil fertility on emission of NO and N20 from mixed pasture converted to high clover pasture, and subsequently to a cereal crop were studied for 21 months. More NO and N20 was emitted from the high fertility than from the low fertility paddocks likely due to restriction of legume growth by phosphorus deficiency. This effect was amplified by increased N cycling due to higher stocking densities on the high fertility pasture and stubble-grazed wheat treatments. Overall, changing the land use from a mixed clover grass pasture to a wheat crop resulted in increased emissions of NO and N2O (2.03 kg as NO and 2.09 kg as N2O). Most of the N2O was emitted when the water filled pore space (WFPS) was high and most of the NO was emitted when the WFPS was low suggesting that the N2O was formed during denitrification and the NO was formed by nitrification.
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ItemEnvironmental factors influencing inflorescence differentation and development, and bunch architecture, of Vitis vinifera L.cvs. Chardonnay, Shiraz and Sauvignon Blanc(University of Melbourne, 2010)Annual yield fluctuations create problems for harvest intake scheduling, fruit ripening and matching supply to demand which results in significant cost to the industry. An understanding of the early development of yield components and the influence of environmental conditions on them is a necessary step toward better yield estimates and ultimately. the future manipulation and stabilisation of yield. The purpose of this research was to bridge the gap between observation-based science and quantitative science in the field of grapevine reproductive biology and to identify critical windows in the development of the grapevine. The factors affecting the timing of initiation and the extent of differentiation of inflorescence primordia (IP) in latent buds of Vitis vinifera L. cvs Shiraz, Chardonnay and Sauvignon Blanc, representing varied environmental zones in Australia and New Zealand were investigated using, interalia, Scanning Electron Microscopy (SEM). Subsequent morphometric analyses were carried out and novel insights into fundamental reproductive development were elucidated. Vineyards located in warmer sites promoted earlier initiation and differentiation of IP and development was more advanced at each phenological stage. Moreover, larger IP were observed where initiation and differentiation had occurred earlier in the season and where the apex diameter range was larger. The process of differentiation may be earlier and more dynamic than previously thought at warmer sites with anlagen visible in Chardonnay by October, primary branch differentiation by anthesis, secondary branch differentiation by veraison and tertiary branch formation occurring on the lower third of basal IP of Shiraz and Chardonnay by dormancy in some instances. Evidence of the timing and extent of differentiation of reproductive structures within latent compound buds has not been previously documented in Sauvignon Blanc and is minimal for Chardonnay and Shiraz. The timing of initiation and extent of primordial branching attained by dormancy may have an important role in determining yield components. Strong correlations were found between IP width and IP length (approximately 80%, P<0.001) for all cultivars at all phenological stages which provide insight into patterns of development that occur some 12-15 months prior to budburst. In climates where initiation was delayed, primordial differentiation was similarly delayed. The SEM examination of latent buds of Shiraz and Sauvignon Blanc for the stage of differentiation of their IP, revealed crystal idioblasts containing raphide bundles of calcium oxalate inside exposed primordial bract tissue. These phytolithic crystals are produced by many plant taxa and have a characteristic morphology which gives them taxonomic significance. Morphometric analysis determined raphides to be on average 35.92 � 2.47 ?m in length and no more than 1 ?m wide. Raphide length was determined by the length of the crystal idioblast housing the bundles. A higher proportion of raphide bundles were observed at apical node positions of both Shiraz and Sauvignon Blanc. The physiologic role of these structures was not determined but it is speculated that they may have a role in nutrient sequestration and regulation. The response of yield components and inflorescence morphology to incremental temperature increases at budburst and to differing vine vigour, were investigated in an integrated series of experiments in the field and in controlled environments on Chardonnay and Shiraz. These experiments revealed contrasting fruiting behaviour of these cultivars in response to environmental stresses imposed by different temperatures and or growth conditions (vigour). Shiraz exhibited opportunistic fruiting behaviour in response to increased root volume with increased internode diameter, increased bud size and increased bud fertility resulting. Chardonnay, on the other hand was more conservative showing an increase in bud fertility with minimal shoot and bud response to increasing vine vigour. The studies presented in this thesis provide valuable new insights into the fundamental developmental stages of important cultivars in response to environmental variables and the influence of these on yield components. Linking observational research and molecular biology may provide further insight into the mechanisms that drive the kinds of differences in development, morphology and yield components that were explored in this thesis. To face the challenge of global climate change, a fundamental understanding of what is likely, in terms of phenology and inflorescence morphology, is required to move toward the formulation of management strategies to maintain desirable production levels and wine quality. Of immediate importance are the grapevine morphological and physiological responses to extreme heat events such as those experienced in Australia over the 2008-2009 and 2009-2010 growing seasons, and expected to be more frequent in future hotter climates.
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ItemNew Technologies and Yam Production Efficiency in Nigeria: Potential for Improved Farm Household Wellbeing( 2018)Nigeria is an agrarian economy with over seventy percent of the population engaged in agriculture. However, the nation depends heavily on food imports. Nigerian food producers are predominantly resource-constrained poor farmers, who are the most food insecure. Nigerian agriculture is chiefly conducted to meet household food requirement but is gradually transitioning to semi-subsistence agriculture. Agriculture was once the mainstay of Nigeria. The Nigerian agricultural sector was abandoned for the oil sector in the early 1970s. This neglect has negative consequences on the country’s agriculture. Presently, Nigerian agriculture is characterized by low performance. Nigeria, once a net food exporter has become a net food importer. With a view to enhancing the performance of Nigeria farmers, improved technologies have been developed and disseminated to farmers. In spite of this, there is food insecurity and poverty intensification in the country. This raises the questions whether or not farmers are adopting these technologies and the efficacy of these technologies in enhancing farmer performance and alleviating poverty in the country. Yam is a significant crop in Nigeria. It is a highly prized crop in the country. It has sociocultural, medicinal, nutritional and economic value. It is nutritionally superior to comparable crops including sweet potato and taro. Notwithstanding, yam farmers in Nigeria are performing poorly. Yam production in Nigeria is mainly impeded by high cost, unavailability of planting material, and over reliance on labour-intensive traditional yam production methods which are expensive, encourage the use of low quality planting materials, and inhibit mechanization of yam production. Yam Minisett Technology (YMT) is an on-farm yam multiplication technique which enables development of high quality planting materials for yam production. The aim of this project is to ascertain the potential of new technology and increased farmers efficiency for wellbeing improvement with reference to yam production and YMT in Nigeria. The specific objectives of this project are to: (i) describe yam production in Nigeria; (ii) compare farm activities and yam production systems in Nigeria; (iii) examine indicators and determinants of performance of yam producers (performance indicators being technical and economic); (iv) examine the role of technology adoption on farmer performance and wellbeing; (v) assess the superiority of seed yam from YMT over other planting materials; and (vi) ascertain determinants of adoption of improved technology. A multi-stage sampling technique was adopted to elicit cross-sectional data from three hundred and sixty yam farmers (120 respondents per State) in three yam-producing States of Nigeria. The States were Benue, Enugu and Ondo. The States are located in different agro-ecological zones of Nigeria and use different methods for yam production. Data were drawn from two Local Government Areas (LGAs) in each State. The LGAs were Katsina-Ala and Buruku in Benue State, Nkanu-east and Uzo-Uwani in Enugu State, and Ose and Owo in Ondo State. Primary and secondary data were used in this investigation. Primary data were collected from the respondents by using a well-structured questionnaire, direct observation and by interviewing farmers. Secondary data were obtained from databases, websites and literature. Data collected include socioeconomic data, resource endowment and utilization data, input and output data, data on farming systems and techniques, attitudinal data, environmental data and health data. Data were analyzed with descriptive statistics, econometrics and economic models. Descriptive statistics were used to describe yam production. An econometric model (stochastic frontier analysis) was used to evaluate the indicators of performance of yam farmers. Two functional forms, the Cobb-Douglas and the Translog production and cost functions, were used to investigate the production and cost of yam. The models were compared for goodness-of-fit. The best functional form was used to determine the technical and economic efficiency and factors influencing efficiency. Metafrontier analysis was used to test the presence of environment/technology gaps between States. The impact of YMT adoption on yam farmer performance was investigated using Propensity Score Matching. Factors influencing adoption were determined with Probit model. Gross Margin (GM) analysis was used to determine the profitability of yam with and without YMT. Partial budgeting was also performed to confirm the profitability of YMT. Net return was used to compare the yam cropping systems. The stochastic frontier analysis showed that, on average, Nigerian yam farmers in those States were not fully efficient in yam production. Benue State was technically efficient in yam production. Both Benue and Enugu yam farmers were relatively economically efficient. The performance (technical and economic efficiency) of Nigerian yam farmers is influenced by farmer’s socioeconomic profile, decisions, and access to inputs and facilities. Yam production is affected by farm size, quantity of planting material, labour and capital input. Cost of yam is determined by output, capital input, rent on land, planting material, wage rate and price of fertilizer. The result of the metafrontier analysis revealed that the production environment and technology for yam differ between States in Nigeria. Benue and Ondo States have more favourable environments for yam production. Enugu yam farmers are operating in a more restrictive environment. GM analysis established that yam production is relatively profitable. Yam had a higher GM than other root and tuber crops. Yam/Maize is the most profitable cropping system in Nigeria. Embracing Yam/Maize intercrop and increased investment in yam production can contribute to improving the poverty status in Nigeria. The adoption of YMT has the potential to improve farmer performance and wellbeing in Nigeria. YMT is a viable seed yam production technique. Yam production using YMT is more profitable than the traditional yam production techniques. Adopters of YMT in Nigeria outperformed non-adopters.
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ItemMolecular and functional genomic analysis of Phytochrome Interacting Factor 4 during the floral transition of soybean( 2019)Climate change is adversely affecting global food production. Reduced crop yields and increasing food demands are presenting new challenges for developing resilient crop varieties. Legume plant soybean is an important food crop next to cereals. Soybean is a rich source of high-quality vegetable oils, protein, nutraceuticals, and it is widely cultivated across the globe for both human and animal consumption. According to the Australian oilseed federation, soybean cultivation strengthens regional economies and contributes to 2.5 billion dollars of the Australian oilseed industry. To breed better soybean crops, a study of light and temperature perception is important, as these events control the process of flowering which is the first step towards total seed production. On the molecular level, light and temperature signal control is a complex process mediated by a network of photoreceptors and transducers. One such transducer is Phytochrome Interacting Factor 4 (PIF4). It is involved in the perception of external environmental stimuli to integrate the information of daily light and temperature fluctuations with the internal physiology of plants. PIF4 has been studied in the model plant Arabidopsis thaliana, but knowledge about its counterparts in soybean is limited. To understand the function of PIF4 in soybean, an integrated genomics, molecular, and functional characterization approach was employed. The genomic analysis show that there are seven active copies of PIF4 gene in the genome of the cultivated soybean (Glycine max). The seven soybean PIF4 genes have evolved at different time points during the soybean genome duplication events, and phylogeny is suggestive of the existence of a conserved PIF4 clade (PIF4 I), which includes Arabidopsis PIF4 and a clade that groups only the PIF4s of legumes (PIF4II). To assess the gene expression patterns of soybean PIF4s during variable photoperiods and temperature conditions, quantitative RT-PCR was performed. Quantitative RT-PCR results showed that three PIF4s belonging to the PIF4I clade (i.e. GmPIF4a, GmPIF4b, and GmPIF4c) had conserved PIF4 like expression (consistent with Arabidopsis pif4) in inductive photoperiod (short day; SD), whereas two soybean PIF4s belonging to the PIF4II clade (i.e. GmPIF4f and GmPIF4g) exhibited reduced to nil sensitivity to short-days. The mRNA transcript levels of three PIF4s were elevated at 35-degree centigrade as compared to 25-degrees centigrade in short days. In non-inductive photoperiod (long day; LD), all soybean PIF4s were responsive to extended light phase suggesting their functional role in long photoperiods. Further, no significant transcript variation was observed at elevated temperatures in long days, except one PIF4, which expressed at higher levels at 30-degrees centigrade as compared to 25-degrees centigrade. Mining of previously published RNA sequencing data obtained from leaf samples of a short-day soybean cultivar (Bragg) undergoing floral transition showed that one of the PIF4s was differentially regulated with high differences in transcript read values on consecutive short days. This soybean PIF4 was designated as GmPIF4b. GmPIF4b was functionally characterized using ectopic expression in Arabidopsis, mutant complementation in Arabidopsis pif4-101 mutants and gene over-expression in the soybean cultivar, Bragg. Ectopic expression of GmPIF4b in Arabidopsis resulted in elongated hypocotyls and early flowering responses suggesting the function of GmPIF4b in hypocotyl elongation and flowering responses. Arabidopsis pif4-101 mutant contains a mutation in the exon-5 of pif4 gene. This mutant is characterized by shorter hypocotyls and a compact rosette size. Complementation of GmPIF4b in Arabidopsis pif4-101 mutant partially rescued the short hypocotyl and compact rosette phenotypes of pif4-101 mutant. The results were suggestive of both conservation and divergence of GmPIF4b. To gain insights into the function of GmPIF4b in soybean, constitutive overexpression of GmPIF4b in soybean (Bragg) was undertaken. Constitutive overexpression resulted in decreased plant height, reduced leaf surface area, decline in total number of branches per plant, and early flowering in transgenic soybean plants as compared to the wild type. Quantitative RT-PCR was performed to study the transcript levels of soybean florigens; GmFT2a and GmFT5a in the transgenic plants (over expressing GmPIF4b). The transcript levels of GmFT2a and GmFT5a were significantly elevated in transgenic lines compared to the wild type. Late maturing soybean varieties, such as Bragg, can terminate flowering in sub-optimal photoperiods. To study the effect of GmPIF4b over-expression on termination of flowering, transgenic soybean plants (over expressing GmPIF4b) grown in short days were transitioned to non-inductive photoperiod (for 10 long days) at full bloom stage. Interestingly, wild type Bragg plants terminated flowers and produced less pods. Transgenic plants did not terminate their reproductive activity and gave rise to a higher number of pods per plant. To study the dynamics of GmPIF4b protein, immunoblot analysis was undertaken. The results showed that on protein level, GmPIF4b follows a strict diurnal expression pattern under both long and short days, suggesting the involvement of biological clock in regulating GmPIF4b protein expression. Chromatin immunoprecipitation was performed to study the protein-DNA interaction of GmPIF4b protein with the promoters of soybean florigens GmFT2a and GmFT5a. The results suggested that GmPIF4b interacts with the promoters of GmFT2a in short-day treated plants, whereas it interacts with the promoter of GmFT5a in a photoperiod insensitive manner. PIF4 is shown to be involved in nitrate assimilation and phosphate acquisition pathways. Soybeans plants were treated with nitrates or orthophosphates under inductive short days to analyse the GmPIF4b gene expression by RT-PCR. The results showed that the application of nitrates and orthophosphates can affect the levels of GmPIF4b transcript and can modulate the expression pattern of soybean floral identity marker gene, GmAP1. Hence, the outcome of this study can contribute towards developing climate-resilient varieties for the future.
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ItemThe potential for flow restoration in urban streams( 2019)Flow regimes in urban waterways are degraded by urbanization and hydraulically efficient stormwater drainage systems. To return more natural flow regimes, urban stormwater management has, in recent times, increasingly focused on source-control approaches – use of Stormwater Control Measures (SCMs). However, experimental evidence of the success of such approaches at the catchment scale is limited, which is a key impediment to the widespread implementation of SCMs. The overarching aim of this Ph.D. thesis is to evaluate the effects of SCMs on flow regimes in urban waterways. This research includes literature reviews and experimental analyses. The literature reviews identified the challenges in the design and analysis of catchment-scale experiments and outlined a series of considerations to address these challenges, which provided practical guidance for future experimental studies and prepared for the methodological development for the experimental part. The experimental analyses were based on an ambitious long-term catchment-scale experiment in Melbourne, Australia, including four Impact catchments (urban with intervention), two Control catchments (urban without intervention), and three Reference catchments (forested, non-urban). Over 700 SCMs were implemented across the four Impact catchments during the study period (October 2009 – September 2017). A suite of flow metrics at different temporal scales and SCM implementation metrics integrating imperviousness and hydrological information were selected, based on literature review and statistical analysis, to facilitate the assessment. An investigation on the hydrological effects of urbanization, using a space-for-time approach, found that quickflow and variability metrics were the most affected by urbanization levels as measured by effective imperviousness (EI). Total flow and slowflow metrics were also affected by urbanization but to a lesser extent. This analysis was used to hypothesize the likely effects of SCM implementation on the flow metrics. The hydrological effects of SCMs were investigated using sophisticated statistical models, to identify to what extent have SCMs changed the flow regime over time. In general, SCMs reduced the negative effects of urbanization, by reducing quickflow, total flow, and absolute variability. However, there were negligible changes in slowflow and inconsistent changes in relative variability metrics, requiring further research. The SCMs have more impacts on short-term flow regime characteristics that better capture the immediate effects of SCMs. The differing relationships between each of the SCM implementation metrics and the flow metrics helped to identify and interpret the likely mechanisms driving SCM impacts on flows. These findings also helped prioritize future work in both practice and research. This novel study makes a significant contribution to the understanding of the effects of the catchment-wide implementation of SCMs on flow regime restoration. It revealed that the SCMs returned most aspects of the flow regime towards the natural condition, but more work is required to restore the full flow regime. This study will also serve as a model for future studies, informing the selection of metrics and statistical methods, and the requirements for future such experiments.