An investigation of geospatial technologies in precision agriculture: a case study on a citrus orchard in the Eastern Cape
- Authors: Nish, Declan Mark
- Date: 2024-10-11
- Subjects: Geospatial technology , Agricultural innovations , Precision farming South Africa Eastern Cape , Citrus orchard , Citrus fruit industry , Drone aircraft , Remote sensing
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465080 , vital:76571
- Description: Citrus production is an input-intensive farming practice that carries a high cost of production. A multitude of both local and global factors continue to put pressure on farmers to produce enough food for local consumption as well as international exports. Despite these challenges production and exports continue to increase, fighting to meet the growing rise in global demand for citrus (Genis, 2018). Growers are continuously in search of anything that may provide them with the ‘edge’ or an advantage to overcoming some of these challenges (Jupp, 2018). One way in which these issues could be addressed is the use of precision agriculture (PA). Precision agriculture, particularly that of commercial, Unmanned Aerial Vehicle (UAV) based PA, provides growers with solutions to these issues in the form of high quality, near real-time data, and provides access and benefits from technology driven agriculture to growers at all levels (Sishodia et al. 2020). The aim of this research therefore was to investigate the potential of high resolution, multi-spectral UAV, and satellite imagery to help citrus farmers manage their inputs better, save costs and increase their yields in a sustainable manner. Supervised image classification using a support vector machine (SVM) was applied to map and classify a citrus farm in the Eastern Cape. The approach aided the identification of Phytophthora spp in the section of interest and implies that remotely sensed data can be used to detect changes in citrus health. Guidelines for applying geospatial technologies at farm level were developed to provide a framework for enabling growers to enhance data driven farm management strategies. , Thesis (MSc) -- Faculty of Science, Geography, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Nish, Declan Mark
- Date: 2024-10-11
- Subjects: Geospatial technology , Agricultural innovations , Precision farming South Africa Eastern Cape , Citrus orchard , Citrus fruit industry , Drone aircraft , Remote sensing
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465080 , vital:76571
- Description: Citrus production is an input-intensive farming practice that carries a high cost of production. A multitude of both local and global factors continue to put pressure on farmers to produce enough food for local consumption as well as international exports. Despite these challenges production and exports continue to increase, fighting to meet the growing rise in global demand for citrus (Genis, 2018). Growers are continuously in search of anything that may provide them with the ‘edge’ or an advantage to overcoming some of these challenges (Jupp, 2018). One way in which these issues could be addressed is the use of precision agriculture (PA). Precision agriculture, particularly that of commercial, Unmanned Aerial Vehicle (UAV) based PA, provides growers with solutions to these issues in the form of high quality, near real-time data, and provides access and benefits from technology driven agriculture to growers at all levels (Sishodia et al. 2020). The aim of this research therefore was to investigate the potential of high resolution, multi-spectral UAV, and satellite imagery to help citrus farmers manage their inputs better, save costs and increase their yields in a sustainable manner. Supervised image classification using a support vector machine (SVM) was applied to map and classify a citrus farm in the Eastern Cape. The approach aided the identification of Phytophthora spp in the section of interest and implies that remotely sensed data can be used to detect changes in citrus health. Guidelines for applying geospatial technologies at farm level were developed to provide a framework for enabling growers to enhance data driven farm management strategies. , Thesis (MSc) -- Faculty of Science, Geography, 2024
- Full Text:
- Date Issued: 2024-10-11
An investigation of the knowledge of and attitudes towards cervical cancer among female students at Rhodes University
- Authors: Pila, Anastacia Mosima
- Date: 2024-10-11
- Subjects: Cervix uteri Cancer , College students Attitudes , Cancer Social aspects , Communication in public health South Africa Makhanda , Knowledge and learning
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/466267 , vital:76713
- Description: South African and African studies on the knowledge of cervical cancer show that there is generally a limited understanding and knowledge of cervical cancer among women. It is for this reason that this qualitative study examines the knowledge of and attitudes towards cervical cancer among female students at Rhodes University, with the aim of determining whether or not this specific group of women (young and educated) has a better understanding and knowledge of cervical cancer. Semi-structured in-depth interviews were conducted with ten female RU students, and two members of staff at RU campus. Using thematic analysis, the study found that there is also a lack of understanding and knowledge of cervical cancer among the participants. Participants were mostly unaware of its causes, preventative methods, screening methods, and they did not know any cervical cancer-based organisations or initiatives in their communities. The two RU members of staff participants confirmed the latter as they stated that the Rhodes University First Thing’s First is the only organisation in Makhanda that deals with cervical cancer awareness and screening. , Thesis (MSocSci) -- Faculty of Humanities, Sociology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Pila, Anastacia Mosima
- Date: 2024-10-11
- Subjects: Cervix uteri Cancer , College students Attitudes , Cancer Social aspects , Communication in public health South Africa Makhanda , Knowledge and learning
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/466267 , vital:76713
- Description: South African and African studies on the knowledge of cervical cancer show that there is generally a limited understanding and knowledge of cervical cancer among women. It is for this reason that this qualitative study examines the knowledge of and attitudes towards cervical cancer among female students at Rhodes University, with the aim of determining whether or not this specific group of women (young and educated) has a better understanding and knowledge of cervical cancer. Semi-structured in-depth interviews were conducted with ten female RU students, and two members of staff at RU campus. Using thematic analysis, the study found that there is also a lack of understanding and knowledge of cervical cancer among the participants. Participants were mostly unaware of its causes, preventative methods, screening methods, and they did not know any cervical cancer-based organisations or initiatives in their communities. The two RU members of staff participants confirmed the latter as they stated that the Rhodes University First Thing’s First is the only organisation in Makhanda that deals with cervical cancer awareness and screening. , Thesis (MSocSci) -- Faculty of Humanities, Sociology, 2024
- Full Text:
- Date Issued: 2024-10-11
Analysing the equity dimensions and governance drivers of water security challenges in Hammanskraal, City of Tshwane, South Africa
- Mahlatsi, Malaika Lesego Samora
- Authors: Mahlatsi, Malaika Lesego Samora
- Date: 2024-10-11
- Subjects: Water security South Africa Hammanskraal , Water governance , Water-supply Law and legislation South Africa City of Tshwane Metropolitan Municipality , Water quality South Africa Hammanskraal , Water-supply Management , South Africa Social conditions
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465011 , vital:76565
- Description: South Africa is faced with a national water security challenge that is increasingly worsening due to a myriad of structural and governance factors. Over the past few years, several municipalities across the country have experience temporary loss of water access, while some have come dangerously close to Day Zero – a day when water levels of the major dams supplying water to residents would become critically low, resulting in households having no running water. But for the people of the township of Hammanskraal in the City of Tshwane metropolitan municipality, water insecurity has reached crisis point. Since 2005, the township has been battling with a chronic lack of access to safe drinking water. The water quality in Hammanskraal has been so dire that in 2019, the South African Human Rights Commission declared it unfit for human consumption and deemed it a violation of human rights. Despite this, the crisis has persisted. In 2023, Hammanskraal became the epicentre of a cholera outbreak that claimed a number of lives in several provinces across the country. Using a qualitative approach, this study analyses the equity dimensions and governance drivers of water security challenges in Hammanskraal. Through interviews with residents in Hammanskraal and government officials in the City of Tshwane metropolitan municipality and the Gauteng Provincial Government, the study explores the lived experiences of those affected by the water insecurity, as well as the governance drivers that inform the crisis. The study, using water justice theory and conflict theory/Marxism, contends that the water security challenges in Hammanskraal are driven by physical, economic and political factors. These factors have their roots in the geo-history of the township as well as contemporary responses to spatial development and water resource management by the post-apartheid government. The study finds that there are equity dimensions to the water security challenges in Hammanskraal. Contextually, the legacy of apartheid’s policy of separate and uneven development, coupled with contemporary failings of the implementation of the National Water Act, impact water access. In terms of water governance, while factors such as climate change and urbanisation are contributing determinants, the water security challenges in Hammanskraal are fundamentally the result of institutional failings that include lack of planning and investment as well as lack of infrastructure maintenance. The implications for South Africa in general is that failure to resolve water inequities and to strengthen water governance will result in the reproduction and persistence of structural inequalities. Key recommendations of the study include the expansion of the Temba Water Purification Plant, strengthening and coordination of institutions for water security, the setting of water allocation ceilings in Gauteng municipalities and investment in alternative water sources and tools for water conservation. The study also recommends further study into the extent to which water security challenges impact social unrest in South Africa. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mahlatsi, Malaika Lesego Samora
- Date: 2024-10-11
- Subjects: Water security South Africa Hammanskraal , Water governance , Water-supply Law and legislation South Africa City of Tshwane Metropolitan Municipality , Water quality South Africa Hammanskraal , Water-supply Management , South Africa Social conditions
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465011 , vital:76565
- Description: South Africa is faced with a national water security challenge that is increasingly worsening due to a myriad of structural and governance factors. Over the past few years, several municipalities across the country have experience temporary loss of water access, while some have come dangerously close to Day Zero – a day when water levels of the major dams supplying water to residents would become critically low, resulting in households having no running water. But for the people of the township of Hammanskraal in the City of Tshwane metropolitan municipality, water insecurity has reached crisis point. Since 2005, the township has been battling with a chronic lack of access to safe drinking water. The water quality in Hammanskraal has been so dire that in 2019, the South African Human Rights Commission declared it unfit for human consumption and deemed it a violation of human rights. Despite this, the crisis has persisted. In 2023, Hammanskraal became the epicentre of a cholera outbreak that claimed a number of lives in several provinces across the country. Using a qualitative approach, this study analyses the equity dimensions and governance drivers of water security challenges in Hammanskraal. Through interviews with residents in Hammanskraal and government officials in the City of Tshwane metropolitan municipality and the Gauteng Provincial Government, the study explores the lived experiences of those affected by the water insecurity, as well as the governance drivers that inform the crisis. The study, using water justice theory and conflict theory/Marxism, contends that the water security challenges in Hammanskraal are driven by physical, economic and political factors. These factors have their roots in the geo-history of the township as well as contemporary responses to spatial development and water resource management by the post-apartheid government. The study finds that there are equity dimensions to the water security challenges in Hammanskraal. Contextually, the legacy of apartheid’s policy of separate and uneven development, coupled with contemporary failings of the implementation of the National Water Act, impact water access. In terms of water governance, while factors such as climate change and urbanisation are contributing determinants, the water security challenges in Hammanskraal are fundamentally the result of institutional failings that include lack of planning and investment as well as lack of infrastructure maintenance. The implications for South Africa in general is that failure to resolve water inequities and to strengthen water governance will result in the reproduction and persistence of structural inequalities. Key recommendations of the study include the expansion of the Temba Water Purification Plant, strengthening and coordination of institutions for water security, the setting of water allocation ceilings in Gauteng municipalities and investment in alternative water sources and tools for water conservation. The study also recommends further study into the extent to which water security challenges impact social unrest in South Africa. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-10-11
Analysis of saprolite-hosted Rutile-Graphite deposit: a case study of Malingunde saprolite-hosted Rutile-Graphite project in Central Malawi
- Authors: Zabula, Ansel Aliko
- Date: 2024-10-11
- Subjects: Rutile , Graphite , Saprolites , Geophysical surveys Malawi , Vanadium pentoxide , Geophysical surveys Economic aspects
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464970 , vital:76562
- Description: The Malingunde graphite project, owned by Sovereign Metals Ltd (SML), has revealed significant potential for rutile and high-grade graphite in saprolite. This study addresses the complexity of mineral assemblages in the Malingunde area, emphasizing the coexistence of graphite and rutile. SML's exploration activities, including extensive drilling and soil sampling, have uncovered variations in associated minerals, such as muscovite, kyanite, garnets, and ilmenite. Rutile, initially discovered incidentally, has prompted further investigation, impacting the financial model of the project. This research aims to analyse the Malingunde deposit, focusing on understanding its mineralogy, formation, and potential for elements like vanadium. Geological surveys reveal the distribution of graphite in the Precambrian to lower Palaeozoic age basement complex, hosted in saprolite resulting from tropical weathering of graphitic gneisses. Exploration techniques, including remote sensing, and geophysics, are crucial in targeting graphite and rutile deposits. Ground electromagnetic surveys, airborne electromagnetic data, and GIS applications aid in identifying and quantifying mineralised areas. Geochemical analysis and metallurgical tests further contribute to understanding the ore body and processing methods. Results indicate an inverse relationship between graphite and rutile concentrations, influencing the economic viability of different regions within the project area. Correlation matrices and regression analyses reveal distinct geological conditions influencing the association of vanadium and graphite in Lifidzi and Malingunde. The study concludes with exploration potential outside the Malingunde project, highlighting regional prospects and potential byproducts like vanadium pentoxide. The ongoing metallurgical tests and pilot plant design signify the project's evolution toward production. Additionally, neighbouring licenses show potential, emphasizing the need for comprehensive research to define and quantify resources in the region. This research provides valuable insights for the mining industry, informing strategies for exploration, resource assessment, and potential byproduct utilization in similar geological settings. , Thesis (MSc) -- Faculty of Science, Geology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Zabula, Ansel Aliko
- Date: 2024-10-11
- Subjects: Rutile , Graphite , Saprolites , Geophysical surveys Malawi , Vanadium pentoxide , Geophysical surveys Economic aspects
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464970 , vital:76562
- Description: The Malingunde graphite project, owned by Sovereign Metals Ltd (SML), has revealed significant potential for rutile and high-grade graphite in saprolite. This study addresses the complexity of mineral assemblages in the Malingunde area, emphasizing the coexistence of graphite and rutile. SML's exploration activities, including extensive drilling and soil sampling, have uncovered variations in associated minerals, such as muscovite, kyanite, garnets, and ilmenite. Rutile, initially discovered incidentally, has prompted further investigation, impacting the financial model of the project. This research aims to analyse the Malingunde deposit, focusing on understanding its mineralogy, formation, and potential for elements like vanadium. Geological surveys reveal the distribution of graphite in the Precambrian to lower Palaeozoic age basement complex, hosted in saprolite resulting from tropical weathering of graphitic gneisses. Exploration techniques, including remote sensing, and geophysics, are crucial in targeting graphite and rutile deposits. Ground electromagnetic surveys, airborne electromagnetic data, and GIS applications aid in identifying and quantifying mineralised areas. Geochemical analysis and metallurgical tests further contribute to understanding the ore body and processing methods. Results indicate an inverse relationship between graphite and rutile concentrations, influencing the economic viability of different regions within the project area. Correlation matrices and regression analyses reveal distinct geological conditions influencing the association of vanadium and graphite in Lifidzi and Malingunde. The study concludes with exploration potential outside the Malingunde project, highlighting regional prospects and potential byproducts like vanadium pentoxide. The ongoing metallurgical tests and pilot plant design signify the project's evolution toward production. Additionally, neighbouring licenses show potential, emphasizing the need for comprehensive research to define and quantify resources in the region. This research provides valuable insights for the mining industry, informing strategies for exploration, resource assessment, and potential byproduct utilization in similar geological settings. , Thesis (MSc) -- Faculty of Science, Geology, 2024
- Full Text:
- Date Issued: 2024-10-11
Analyzing Microsporidia sp. MB from sequence to biology: comprehensive exploration of the genome, protein structures, and functions through extensive bioinformatics analysis
- Authors: Ang'ang'o, Lilian Mbaisi
- Date: 2024-10-11
- Subjects: Microsporidia , Whole genome sequencing , Proteins Structure , Symbiont , Malaria Prevention , Vector control
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466480 , vital:76734 , DOI https://doi.org/10.21504/10962/466480
- Description: Microsporidia are spore-forming intracellular organisms classified as the earliest divergent group within the Fungi kingdom. Microsporidia have been found widely affecting different hosts, including both vertebrates and invertebrates. The pathogenicity of microsporidia depends on their species and the host species they infect. Due to their obligate intracellular nature, microsporidia have extensively evolved. This is illustrated by their highly variable genome sizes and gene content. Being minimalist eukaryotes, the microsporidia genome is often associated with extreme gene reduction and compaction. However, these interesting microorganisms retain particular genes that help them acquire specific host nutrients, thereby relying heavily on their host for survival and proliferation. The mode of sexual reproduction of microsporidia has not been well-studied. Harnessing microsporidia in the laboratory is often a challenge, however, the advances in computational tools have made it cheaper and quicker to accurately predict and annotate these organisms to understand their mechanism of infection. Understanding the protein structure and function of these unique organisms is the baseline for providing insights into their biology and survival in their respective hosts. Microsporidia genomes contain a large proportion of hypothetical proteins of which their functions are not described. Vittaforma corneae ATCC 50505 was used as a model to highlight the functions and structure of these otherwise unknown proteins. A systematic annotation pipeline employing exhaustive computational tools was devised to carefully annotate the hypothetical proteins of V. corneae, aiming to characterize their structure and function.The genome of the novel microsporidian, Microsporidia sp. MB, a Plasmodium-transmission-blocking symbiont isolated from Anopheles mosquitoes in Sub-Saharan Africa, was sequenced, assembled, and annotated. The genome was found to contain over 2000 putative genes spanning its 5.9 Mb size and contained minimal repeats. Comparative phylogenomic analysis of Microsporidia sp. MB grouped this symbiont within the Enterocytozoonida (clade IV) microsporidia, clustering with its closest relative – V. corneae. Using robust computational techniques, prediction and characterization of the putative proteins of Microsporidia sp. MB was conducted. The decay of several proteins in the glycolytic pathway is one unique characteristic associated with microsporidia. The proteins retained or lost often vary across the microsporidian taxon. This study highlights the retention of most of the proteins involved in the glycolytic pathway in Microsporidia sp. MB. The available genome dataset of Microsporidia sp. MB was further used to infer its mode of sexual reproduction. The symbiont appears to have several meiotic-related gene orthologs, suggesting that it is capable of sexual reproduction. These findings describe the basic biology of Microsporidia sp. MB and provide a basis for future Next-Generation Sequencing, RNA sequencing experiments ultimately informing the application of this microorganism as a biological malaria control tool. , Thesis (PhD) -- Faculty of Science, Biochemistry, Microbiology and Bioinformatics, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Ang'ang'o, Lilian Mbaisi
- Date: 2024-10-11
- Subjects: Microsporidia , Whole genome sequencing , Proteins Structure , Symbiont , Malaria Prevention , Vector control
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466480 , vital:76734 , DOI https://doi.org/10.21504/10962/466480
- Description: Microsporidia are spore-forming intracellular organisms classified as the earliest divergent group within the Fungi kingdom. Microsporidia have been found widely affecting different hosts, including both vertebrates and invertebrates. The pathogenicity of microsporidia depends on their species and the host species they infect. Due to their obligate intracellular nature, microsporidia have extensively evolved. This is illustrated by their highly variable genome sizes and gene content. Being minimalist eukaryotes, the microsporidia genome is often associated with extreme gene reduction and compaction. However, these interesting microorganisms retain particular genes that help them acquire specific host nutrients, thereby relying heavily on their host for survival and proliferation. The mode of sexual reproduction of microsporidia has not been well-studied. Harnessing microsporidia in the laboratory is often a challenge, however, the advances in computational tools have made it cheaper and quicker to accurately predict and annotate these organisms to understand their mechanism of infection. Understanding the protein structure and function of these unique organisms is the baseline for providing insights into their biology and survival in their respective hosts. Microsporidia genomes contain a large proportion of hypothetical proteins of which their functions are not described. Vittaforma corneae ATCC 50505 was used as a model to highlight the functions and structure of these otherwise unknown proteins. A systematic annotation pipeline employing exhaustive computational tools was devised to carefully annotate the hypothetical proteins of V. corneae, aiming to characterize their structure and function.The genome of the novel microsporidian, Microsporidia sp. MB, a Plasmodium-transmission-blocking symbiont isolated from Anopheles mosquitoes in Sub-Saharan Africa, was sequenced, assembled, and annotated. The genome was found to contain over 2000 putative genes spanning its 5.9 Mb size and contained minimal repeats. Comparative phylogenomic analysis of Microsporidia sp. MB grouped this symbiont within the Enterocytozoonida (clade IV) microsporidia, clustering with its closest relative – V. corneae. Using robust computational techniques, prediction and characterization of the putative proteins of Microsporidia sp. MB was conducted. The decay of several proteins in the glycolytic pathway is one unique characteristic associated with microsporidia. The proteins retained or lost often vary across the microsporidian taxon. This study highlights the retention of most of the proteins involved in the glycolytic pathway in Microsporidia sp. MB. The available genome dataset of Microsporidia sp. MB was further used to infer its mode of sexual reproduction. The symbiont appears to have several meiotic-related gene orthologs, suggesting that it is capable of sexual reproduction. These findings describe the basic biology of Microsporidia sp. MB and provide a basis for future Next-Generation Sequencing, RNA sequencing experiments ultimately informing the application of this microorganism as a biological malaria control tool. , Thesis (PhD) -- Faculty of Science, Biochemistry, Microbiology and Bioinformatics, 2024
- Full Text:
- Date Issued: 2024-10-11
Application of SWAT+ model to assess the hydrology of irrigated agricultural catchments in Western Cape, South Africa
- Authors: Mabohlo, Sakikhaya
- Date: 2024-10-11
- Subjects: Soil and Water Assessment Tool , Agricultural hydrology , Hydrologic models , Irrigation , Reservoirs , Water-supply, Agricultural South Africa Western Cape
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464986 , vital:76563
- Description: Agricultural activities can modify hydrological processes in catchments. An in-depth investigation of the impact of agriculture on hydrological processes is thus crucial for sustainable water management and utilisation planning in agricultural catchments. Hydrological models are widely used as practical tools to estimate and understand hydrological processes at various scales in catchments. However, it is often challenging to represent hydrological processes accurately in agriculture-dominated areas due to their complexity and the structural inadequacy of models. Complexities driven by agricultural developments such as reservoirs, cultivation irrigation, and water transfers are often intricate and difficult to represent in detail. The current study applied the SWAT+ hydrological model to the agriculture-dominated Twee and Leeu catchments in the Western Cape Province of South Africa. The SWAT+ model was preferred because it is versatile in representing multiple reservoirs and irrigation from multiple sources. The model application aimed to enhance the understanding of hydrological processes and the impact of agricultural water use on catchment hydrology, explore the capabilities and performance of this relatively new version of the SWAT in a complex catchment and provide baseline hydrology input for systems models that were used to formulate a water management plan for the catchment. The SWAT+ model was able to represent the significant number of reservoirs in the catchment. In some cases, small farm dams had to be lumped together to deal with the model's structural inadequacy. The model performed well in terms of observed and simulated streamflow comparison. NSE and R2 values above the standard of 0.5 were obtained for both catchments. Moreover, an NSE of 0.7 at a daily time-step simulation was obtained for the Leeu Catchment validation period, indicating a generally impressive SWAT+ performance. The model indicated that hydrological processes in the area were largely dominated by evapotranspiration, which is expected of semi-arid regions. 55% of the total water input into the Twee quaternary catchment is lost through evapotranspiration, while 22% is converted into surface runoff. Interflow and groundwater flow account for 9% and 9% of the catchment water, respectively. The remaining 5% is distributed to soil moisture and groundwater storage. For the Leeu, the model simulated a loss of 67% of the precipitation through evapotranspiration. Interflow and surface runoff were estimated to be 25% and 24%, respectively. Groundwater contribution to the stream accounts for 7%. Therefore, evapotranspiration and surface runoff are the dominant processes from a water balance perspective, whereas groundwater flow is also significant. Agricultural activities impacted the hydrological system significantly, and this is mainly attributed to the construction of numerous reservoirs and the subsequent intensive irrigation in the dry summer periods. The model simulation revealed that the reservoir and irrigation reduced the annual average streamflow by 71% in the Twee Catchment. In the Leeu Catchment, reservoirs and irrigation resulted in an annual average streamflow reduction of 77%. Therefore, agriculture has significantly altered flow patterns in the catchment, particularly downstream areas, during drier years. In conclusion, understanding of hydrological processes, reservoir and irrigation impact on catchment flow dynamics are the key outcomes that support decision-making regarding sustainable water management and utilisation planning. The broader outcomes, including spatially distributed flows and irrigation demand for different crop types, were used as baseline inputs for systems models that explored various water management options. SWAT+ thus played a crucial role in developing a water management plan for the area. Although the model exhibited some structural deficiencies in representing some catchment complexities, it fairly represented and enhanced our understanding of the hydrological dynamics of the Twee and Leeu Catchments. Additionally, the model has proven to be a versatile tool that can be applied for practical catchment water management in the agriculture-dominated catchments of South Africa. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mabohlo, Sakikhaya
- Date: 2024-10-11
- Subjects: Soil and Water Assessment Tool , Agricultural hydrology , Hydrologic models , Irrigation , Reservoirs , Water-supply, Agricultural South Africa Western Cape
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464986 , vital:76563
- Description: Agricultural activities can modify hydrological processes in catchments. An in-depth investigation of the impact of agriculture on hydrological processes is thus crucial for sustainable water management and utilisation planning in agricultural catchments. Hydrological models are widely used as practical tools to estimate and understand hydrological processes at various scales in catchments. However, it is often challenging to represent hydrological processes accurately in agriculture-dominated areas due to their complexity and the structural inadequacy of models. Complexities driven by agricultural developments such as reservoirs, cultivation irrigation, and water transfers are often intricate and difficult to represent in detail. The current study applied the SWAT+ hydrological model to the agriculture-dominated Twee and Leeu catchments in the Western Cape Province of South Africa. The SWAT+ model was preferred because it is versatile in representing multiple reservoirs and irrigation from multiple sources. The model application aimed to enhance the understanding of hydrological processes and the impact of agricultural water use on catchment hydrology, explore the capabilities and performance of this relatively new version of the SWAT in a complex catchment and provide baseline hydrology input for systems models that were used to formulate a water management plan for the catchment. The SWAT+ model was able to represent the significant number of reservoirs in the catchment. In some cases, small farm dams had to be lumped together to deal with the model's structural inadequacy. The model performed well in terms of observed and simulated streamflow comparison. NSE and R2 values above the standard of 0.5 were obtained for both catchments. Moreover, an NSE of 0.7 at a daily time-step simulation was obtained for the Leeu Catchment validation period, indicating a generally impressive SWAT+ performance. The model indicated that hydrological processes in the area were largely dominated by evapotranspiration, which is expected of semi-arid regions. 55% of the total water input into the Twee quaternary catchment is lost through evapotranspiration, while 22% is converted into surface runoff. Interflow and groundwater flow account for 9% and 9% of the catchment water, respectively. The remaining 5% is distributed to soil moisture and groundwater storage. For the Leeu, the model simulated a loss of 67% of the precipitation through evapotranspiration. Interflow and surface runoff were estimated to be 25% and 24%, respectively. Groundwater contribution to the stream accounts for 7%. Therefore, evapotranspiration and surface runoff are the dominant processes from a water balance perspective, whereas groundwater flow is also significant. Agricultural activities impacted the hydrological system significantly, and this is mainly attributed to the construction of numerous reservoirs and the subsequent intensive irrigation in the dry summer periods. The model simulation revealed that the reservoir and irrigation reduced the annual average streamflow by 71% in the Twee Catchment. In the Leeu Catchment, reservoirs and irrigation resulted in an annual average streamflow reduction of 77%. Therefore, agriculture has significantly altered flow patterns in the catchment, particularly downstream areas, during drier years. In conclusion, understanding of hydrological processes, reservoir and irrigation impact on catchment flow dynamics are the key outcomes that support decision-making regarding sustainable water management and utilisation planning. The broader outcomes, including spatially distributed flows and irrigation demand for different crop types, were used as baseline inputs for systems models that explored various water management options. SWAT+ thus played a crucial role in developing a water management plan for the area. Although the model exhibited some structural deficiencies in representing some catchment complexities, it fairly represented and enhanced our understanding of the hydrological dynamics of the Twee and Leeu Catchments. Additionally, the model has proven to be a versatile tool that can be applied for practical catchment water management in the agriculture-dominated catchments of South Africa. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-10-11
Artificial Intelligence (AI) and blockchain technologies in advancing sustainable healthcare development in Kenya: a critique of dependency theory
- Monethi, Tlhokomelo Brigette Rethabile
- Authors: Monethi, Tlhokomelo Brigette Rethabile
- Date: 2024-10-11
- Subjects: Artificial intelligence , Blockchains (Databases) , Dependency theory , Sustainable development , Health care reform Kenya
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/466016 , vital:76677
- Description: This thesis explores the transformative potential of artificial intelligence (AI) and blockchain technologies in advancing healthcare delivery in Kenya through a critique of Dependency Theory. It investigates how these technologies contribute to improving accessibility, efficiency, and quality of care—particularly in underserved regions, while also addressing the structural dependencies that limit Kenya’s healthcare autonomy. Using a qualitative methodology, this study examines five case studies—Sophie Bot, Ilara Health, Tambua Health, AfyaRekod, and PanaBIOS—to highlight both the opportunities and challenges AI and blockchain present in reducing external reliance. Although AI-powered diagnostics and blockchain-based patient data management systems have revolutionised healthcare in Kenya, these technologies remain dependent on foreign capital and expertise for their development and maintenance. The research finds that while AI and blockchain technologies offer a path to leapfrog traditional barriers in healthcare delivery, their implementation critiques traditional notions of dependency theory. Nonetheless, the thesis identifies significant ethical considerations—including digital inequality, data privacy, and AI biases—that must be addressed to ensure equitable, self-sufficient healthcare provision. This study concludes with recommendations for fostering technological autonomy in Kenya's healthcare system, focusing on building local capacity, addressing infrastructural challenges, and aligning AI and blockchain integration with ethical and socio-cultural contexts. By doing this, this research contributes to the broader discourse on technology and healthcare in developing nations, offering pathways for reducing dependency and achieving sustainable healthcare development in Kenya. , Thesis (MA) -- Faculty of Humanities, Political and International Studies, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Monethi, Tlhokomelo Brigette Rethabile
- Date: 2024-10-11
- Subjects: Artificial intelligence , Blockchains (Databases) , Dependency theory , Sustainable development , Health care reform Kenya
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/466016 , vital:76677
- Description: This thesis explores the transformative potential of artificial intelligence (AI) and blockchain technologies in advancing healthcare delivery in Kenya through a critique of Dependency Theory. It investigates how these technologies contribute to improving accessibility, efficiency, and quality of care—particularly in underserved regions, while also addressing the structural dependencies that limit Kenya’s healthcare autonomy. Using a qualitative methodology, this study examines five case studies—Sophie Bot, Ilara Health, Tambua Health, AfyaRekod, and PanaBIOS—to highlight both the opportunities and challenges AI and blockchain present in reducing external reliance. Although AI-powered diagnostics and blockchain-based patient data management systems have revolutionised healthcare in Kenya, these technologies remain dependent on foreign capital and expertise for their development and maintenance. The research finds that while AI and blockchain technologies offer a path to leapfrog traditional barriers in healthcare delivery, their implementation critiques traditional notions of dependency theory. Nonetheless, the thesis identifies significant ethical considerations—including digital inequality, data privacy, and AI biases—that must be addressed to ensure equitable, self-sufficient healthcare provision. This study concludes with recommendations for fostering technological autonomy in Kenya's healthcare system, focusing on building local capacity, addressing infrastructural challenges, and aligning AI and blockchain integration with ethical and socio-cultural contexts. By doing this, this research contributes to the broader discourse on technology and healthcare in developing nations, offering pathways for reducing dependency and achieving sustainable healthcare development in Kenya. , Thesis (MA) -- Faculty of Humanities, Political and International Studies, 2024
- Full Text:
- Date Issued: 2024-10-11
Aspects of the sustainability of the wild honeybush industry
- Authors: McGregor, Gillian Kathleen
- Date: 2024-10-11
- Subjects: Cyclopia intermedia , Renewable natural resources South Africa , Sustainability , Local ecological knowledge , Harvesting
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464266 , vital:76493 , DOI 10.21504/10962/464266
- Description: Honeybush products are uniquely South African, derived from plants of the fynbos genus, Cyclopia. Cyclopia intermedia is the most widespread species, distributed across 11 496 km2 of the Cape Fold Mountains, and provided the bulk of supply for the industry until 2022. While the industry is small, it is a locally significant industry affecting the livelihoods of harvesters, farmers and processors in the greater Langkloof region of the Eastern and Western Cape provinces of South Africa. The industry has evolved from a cottage one, to a commercial scale, and concerns have been raised over the sustainability of the wild resource specifically, and the industry in general. The research aimed to improve our understanding of aspects of the sustainability of the wild honeybush industry. A mixed methods design was adopted, which allowed for the inclusion of data collection approaches and analysis which tell a richer story than one with a singular modus. Four objectives were identified, which entailed: (i) mapping the resource to establish the distribution range of C. intermedia; (ii) recording of local ecological knowledge (LEK) and traditional ecological knowledge (TEK) around best practice harvesting; (iii) assessing the sustainability of harvest enterprise types through analysis of yield history and harvester loads; (iv) identifying differences between harvested and unharvested C. intermedia populations. Mapping of the resource drew on a variety of existing data sources, field mapping, GIS-based analysis, species distribution modelling and expert mapping to create a comprehensive and accurate map of the species distribution. The species is estimated to occupy a distribution range of 11 496 km2, 49% of which occurs in formally protected areas. Based on local scale mapping by experts, 100km2 is estimated to be in use for wild harvesting in the production area of the Langkloof. Information on best practice harvesting was collected through in-depth interviews with harvesters, harvest managers, processors and farmers (in the field at harvest events) and through questionnaire surveys and focus group discussions at a honeybush stakeholder workshop. In combination with harvest event surveys at which harvester practice was observed and recorded, and surveys were conducted of the harvest yield and of plants in the harvested population, the information was used to produce the first formal account of best practice for sustainable harvesting of wild honeybush. To assess the sustainability of harvest enterprises and associated harvester livelihoods, harvester managers were interviewed to create profiles of typical harvesting enterprises based on their practices and harvest yield histories. Of the three harvest enterprises considered, two showed sustained yields over time, while those of a large contract type enterprise were less sustainable with declining yields on three out of six farms. From a statistical analysis of the records it was found that the most effective team size was 10 or less harvesters in terms of livelihood sustainability. They could earn a fair livelihood (ZAR67 680.00) per annum, based on a 94 kg load per daily harvest event, sold to the processor at ZAR 5.00, for nine months of the year, working a four-day week. For a team to operate sustainably, it was found that it should consist of experienced harvesters harvesting conservatively, at intervals of at least four years, and be responsive to local environmental conditions. Detailed field surveys of C. intermedia plants at 38 sites representing harvested and unharvested populations were carried out to understand the impact of harvesting on the plants. A statistical analysis of the plant's dimensions related to the physical environment, fire and harvest history using generalised linear models revealed that while unharvested plants were slightly larger, only crown diameter and stem counts were significantly so. Seedlings were noticeably scarce at all sites, including recently burnt sites. A significant finding of the research was that in a fecundity survey, unharvested plants produced significantly more pods. The impact of this is unknown, but it has implications for management and the sustainable use of wild resources in the long term. Further understanding of the impact of harvesting came from surveys of cultivated stands of C. intermedia (different ages and harvest histories, but all harvested at three-year intervals) and surveys of a wild population, which was subjected to unregulated harvesting. For the cultivated stand: after 12 years, plants declined in all measured dimensions, while in the wild population, 45% of the plants died over a seven-year period. The surveys proved that a three-year interval or frequent, unregulated harvest is unsustainable. The research was used to produce the wild harvesting guidelines, which have become the accepted standard for the industry. It has demonstrated that under the right circumstances, harvesting of the wild C. intermedia resource is broadly sustainable. However, there needs to be informed management of the use of the resource in terms of harvest team types and their protocols, particularly with regard to harvest intervals and possible interventions to improve seed production to achieve sustainable use of the resource in social, economic and ecological terms. , Thesis (PhD) -- Faculty of Science, Geography, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: McGregor, Gillian Kathleen
- Date: 2024-10-11
- Subjects: Cyclopia intermedia , Renewable natural resources South Africa , Sustainability , Local ecological knowledge , Harvesting
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464266 , vital:76493 , DOI 10.21504/10962/464266
- Description: Honeybush products are uniquely South African, derived from plants of the fynbos genus, Cyclopia. Cyclopia intermedia is the most widespread species, distributed across 11 496 km2 of the Cape Fold Mountains, and provided the bulk of supply for the industry until 2022. While the industry is small, it is a locally significant industry affecting the livelihoods of harvesters, farmers and processors in the greater Langkloof region of the Eastern and Western Cape provinces of South Africa. The industry has evolved from a cottage one, to a commercial scale, and concerns have been raised over the sustainability of the wild resource specifically, and the industry in general. The research aimed to improve our understanding of aspects of the sustainability of the wild honeybush industry. A mixed methods design was adopted, which allowed for the inclusion of data collection approaches and analysis which tell a richer story than one with a singular modus. Four objectives were identified, which entailed: (i) mapping the resource to establish the distribution range of C. intermedia; (ii) recording of local ecological knowledge (LEK) and traditional ecological knowledge (TEK) around best practice harvesting; (iii) assessing the sustainability of harvest enterprise types through analysis of yield history and harvester loads; (iv) identifying differences between harvested and unharvested C. intermedia populations. Mapping of the resource drew on a variety of existing data sources, field mapping, GIS-based analysis, species distribution modelling and expert mapping to create a comprehensive and accurate map of the species distribution. The species is estimated to occupy a distribution range of 11 496 km2, 49% of which occurs in formally protected areas. Based on local scale mapping by experts, 100km2 is estimated to be in use for wild harvesting in the production area of the Langkloof. Information on best practice harvesting was collected through in-depth interviews with harvesters, harvest managers, processors and farmers (in the field at harvest events) and through questionnaire surveys and focus group discussions at a honeybush stakeholder workshop. In combination with harvest event surveys at which harvester practice was observed and recorded, and surveys were conducted of the harvest yield and of plants in the harvested population, the information was used to produce the first formal account of best practice for sustainable harvesting of wild honeybush. To assess the sustainability of harvest enterprises and associated harvester livelihoods, harvester managers were interviewed to create profiles of typical harvesting enterprises based on their practices and harvest yield histories. Of the three harvest enterprises considered, two showed sustained yields over time, while those of a large contract type enterprise were less sustainable with declining yields on three out of six farms. From a statistical analysis of the records it was found that the most effective team size was 10 or less harvesters in terms of livelihood sustainability. They could earn a fair livelihood (ZAR67 680.00) per annum, based on a 94 kg load per daily harvest event, sold to the processor at ZAR 5.00, for nine months of the year, working a four-day week. For a team to operate sustainably, it was found that it should consist of experienced harvesters harvesting conservatively, at intervals of at least four years, and be responsive to local environmental conditions. Detailed field surveys of C. intermedia plants at 38 sites representing harvested and unharvested populations were carried out to understand the impact of harvesting on the plants. A statistical analysis of the plant's dimensions related to the physical environment, fire and harvest history using generalised linear models revealed that while unharvested plants were slightly larger, only crown diameter and stem counts were significantly so. Seedlings were noticeably scarce at all sites, including recently burnt sites. A significant finding of the research was that in a fecundity survey, unharvested plants produced significantly more pods. The impact of this is unknown, but it has implications for management and the sustainable use of wild resources in the long term. Further understanding of the impact of harvesting came from surveys of cultivated stands of C. intermedia (different ages and harvest histories, but all harvested at three-year intervals) and surveys of a wild population, which was subjected to unregulated harvesting. For the cultivated stand: after 12 years, plants declined in all measured dimensions, while in the wild population, 45% of the plants died over a seven-year period. The surveys proved that a three-year interval or frequent, unregulated harvest is unsustainable. The research was used to produce the wild harvesting guidelines, which have become the accepted standard for the industry. It has demonstrated that under the right circumstances, harvesting of the wild C. intermedia resource is broadly sustainable. However, there needs to be informed management of the use of the resource in terms of harvest team types and their protocols, particularly with regard to harvest intervals and possible interventions to improve seed production to achieve sustainable use of the resource in social, economic and ecological terms. , Thesis (PhD) -- Faculty of Science, Geography, 2024
- Full Text:
- Date Issued: 2024-10-11
Aspects of the water use of Cannabis sativa L. under dryland cultivation in the Eastern Cape
- Authors: Zenani, Kamva Trevor Songo
- Date: 2024-10-11
- Subjects: Cannabis , Water consumption , Large aperture scintillometer , Cannabis Water requirements , Dry farming South Africa Eastern Cape , Evapotranspiration
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465035 , vital:76567
- Description: Cannabis spp is one of the oldest cultivated plants, with its origin in Asia. It has two species, namely C. indica and C. sativa. This research focuses on C. sativa, which is widely cultivated locally and globally. C. sativa has a wide range of uses, including industrial, medicinal, religious, and recreational. This study will be focusing on the water use of medicinal and recreational C. sativa grown under dryland conditions. In recent years, there has been a growing interest in increasing its cultivation, but there are reports of it having high water usage. The global interest has led many governments to review the laws governing this plant as it is a controlled substance in many countries. Due to its legal status, there is a dearth of knowledge about its growth and water use. It is against this backdrop that the Water Research Commission (WRC) commissioned this study into the water use of this plant. This will provide evidence-based support for the issuing of water use licenses by the Department of Water and Sanitation. The Eastern Cape and KwaZulu Natal have many small-scale legacy farmers who have been growing C. sativa illegally for decades. The findings of this research will seek to fill some of these knowledge gaps and assist legacy farmers in the cultivation of this plant. This research had four approaches, which include 1) planting the crop in a dryland location that will mimic the conditions experienced by legacy growers, 2) the collection of plant biophysical variables in the study site in order to gain a better understanding of the plant’s health, growth, progress, and to use these variables to parameterize a mechanistic eco-physiological model, 3) the installing of a large aperture scintillometer (LAS) together with a micro-meteorological station to measure the evapotranspiration (ET) and meteorological parameters over a crop cycle, 4) to use MEDRUSH evapotranspiration model to predict the ET and compare these results against that of the LAS. The results show that water provision had a significant impact on plant biophysical variables and water use. The plants received 154 mm (2 mm day-1) of rain during the crop cycle. The large aperture scintillometer recorded a total ET of 126.8 mm (1.76 mm day-1) during the same period. The MEDRUSH model (2.5 mm day-1) overestimated the LAS ET (1.79 mm day-1), and the results from the daily ET revealed that C. sativa had higher daily ET when compared to the local grass Eragrostis plana. These results confirm that at this location in the Eastern Cape, C. sativa requires regular irrigation during the growing season to grow and secure a crop. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Zenani, Kamva Trevor Songo
- Date: 2024-10-11
- Subjects: Cannabis , Water consumption , Large aperture scintillometer , Cannabis Water requirements , Dry farming South Africa Eastern Cape , Evapotranspiration
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465035 , vital:76567
- Description: Cannabis spp is one of the oldest cultivated plants, with its origin in Asia. It has two species, namely C. indica and C. sativa. This research focuses on C. sativa, which is widely cultivated locally and globally. C. sativa has a wide range of uses, including industrial, medicinal, religious, and recreational. This study will be focusing on the water use of medicinal and recreational C. sativa grown under dryland conditions. In recent years, there has been a growing interest in increasing its cultivation, but there are reports of it having high water usage. The global interest has led many governments to review the laws governing this plant as it is a controlled substance in many countries. Due to its legal status, there is a dearth of knowledge about its growth and water use. It is against this backdrop that the Water Research Commission (WRC) commissioned this study into the water use of this plant. This will provide evidence-based support for the issuing of water use licenses by the Department of Water and Sanitation. The Eastern Cape and KwaZulu Natal have many small-scale legacy farmers who have been growing C. sativa illegally for decades. The findings of this research will seek to fill some of these knowledge gaps and assist legacy farmers in the cultivation of this plant. This research had four approaches, which include 1) planting the crop in a dryland location that will mimic the conditions experienced by legacy growers, 2) the collection of plant biophysical variables in the study site in order to gain a better understanding of the plant’s health, growth, progress, and to use these variables to parameterize a mechanistic eco-physiological model, 3) the installing of a large aperture scintillometer (LAS) together with a micro-meteorological station to measure the evapotranspiration (ET) and meteorological parameters over a crop cycle, 4) to use MEDRUSH evapotranspiration model to predict the ET and compare these results against that of the LAS. The results show that water provision had a significant impact on plant biophysical variables and water use. The plants received 154 mm (2 mm day-1) of rain during the crop cycle. The large aperture scintillometer recorded a total ET of 126.8 mm (1.76 mm day-1) during the same period. The MEDRUSH model (2.5 mm day-1) overestimated the LAS ET (1.79 mm day-1), and the results from the daily ET revealed that C. sativa had higher daily ET when compared to the local grass Eragrostis plana. These results confirm that at this location in the Eastern Cape, C. sativa requires regular irrigation during the growing season to grow and secure a crop. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-10-11
Assessing the impacts of Lantana camara and opportunities for ecological restoration after its removal: does clearing facilitate both soil and native vegetation recovery?
- Authors: Bolosha, Uviwe
- Date: 2024-10-11
- Subjects: Lantana camara , Restoration and conservation , Restoration ecology , Invasive plants , Physicochemical process , Soil seed banks , Invasion driver
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466524 , vital:76738 , DOI https://doi.org/10.21504/10962/466524
- Description: Invasive alien plants (IAPs) are one of the major contributing factors to biodiversity loss, and Lantana camara is among the top ten alien invaders worldwide. Lantana camara threatens native biodiversity and human health, prevents natural succession, and has an economic and environmental impact globally. With current climate change and future predictions, these IAPs are anticipated to continue posing huge threats to ecosystem composition, structure, and function. Even though L. camara is a widespread IAP, there is still limited knowledge in South Africa on how it influences soil physicochemical properties at the species level, vegetation communities, and soil seed banks at the community level following its invasion. There is also minimal knowledge on the management and control (i.e., clearing for restoration purposes) of L. camara in South Africa, especially in the Eastern Cape province of South Africa. To address the knowledge gap, this thesis was structured into three main aspects: understanding L. camara invasion mechanisms, evaluating invasion impacts on both the aboveground and belowground communities, and invasion management. The main objectives of this thesis were (i) to examine how L. camara invasion (at a species level) affected soil physicochemical properties across different seasons, (ii) to assess how L. camara influences natural vegetation (at a community level), (iii) to examine the effects of L. camara invasion (at the community level) on belowground soil seed banks and also assess the availability of pioneer native species and IAPs in the soil seed banks, and (iv) to evaluate soil and vegetation responses following L. camara clearing in comparison to invaded and uninvaded conditions. To answer these objectives, different studies were carried out in the Eastern Cape province, South Africa, on various farms within the Albany Thicket Biome. The results (Chapter 3) show that L. camara alters and modifies some soil physical properties, such as soil infiltration rate, repellency, and soil penetration resistance, in the communities it invades. A significant decrease in soil penetration under the L. camara canopy was observed compared to soils from the edge and out position. Moreover, significantly faster infiltration rates were observed in the canopy and edge positions than in the out position. The study also observed that these modifications in soil physical properties vary depending on the season. A seasonal comparison in soil penetration showed that soil was more compact in the dry season than the wet season, and significantly faster infiltration rates were observed in summer than in the other seasons. The soil collected under the invaded sampling positions was mostly wettable (80–100%), and not strongly, severely, or extremely repellent across all the seasons. The changes in soil properties caused by L. camara could create favourable conditions for its growth and invasion. Seasonal changes in soil properties also highlight how environmental conditions, especially temperature and rainfall patterns, can affect soil physical properties. The findings in Chapter 4 observed both the negative and positive impacts of L. camara, where the species did not have negative effects on species richness, diversity, or cover of some native species growth forms (i.e., graminoids and forbs). For all species, both species richness and Shannon-Wiener (H’) were significantly higher in the L. camara invaded condition compared to the uninvaded condition. The Simpson’s (J’) and Pielou’s evenness (D’) indices, however, showed no differences between the invasion conditions. Furthermore, the effects of L. camara on vegetation cover were growth form-dependent, with differences being noted for trees and shrubs but not for graminoids and forbs. Changes in vegetation structure and composition were also noted where L. camara created favourable conditions for some species to co-occur with it, meaning that its known trait of changing soil physicochemical properties could benefit some species. Generally, the results of this study showed that the effects of L. camara on vegetation are varied and do not have a predictable pattern, so they should not be generalised. The findings (Chapter 5) also indicate that the L. camara invasion had a negative impact on seedling abundance and composition but not species diversity and richness. This is evident through the decrease in seedling abundance of forbs and graminoids in the L. camara invaded condition. Lantana camara also acted as a refuge for some plant species, mostly native forbs and grasses, including Aptenia cordifolia, Chamaesyce prostrata, Oxalis spp., and Setaria spp., as well as alien forbs such as Bidens pilosa, Plantago lanceolata, and Taraxacum officinale, suggesting L. camara does not entirely eliminate less competitive plant species but can co-exist with them. Lantana camara also displaced some native species, and this could be associated with their displacement in the standing vegetation. Moreover, the species also displaced the seed banks of some alien species, thus showing its competitive ability. Overall, L. camara invasion negatively influenced soil seed bank seedling abundance and composition of some species, but not diversity and richness. The results in Chapter 6 indicated that clearing L. camara is an effective method for reducing its population. However, our findings suggest that clearing alone may not be enough to re-establish these communities with native species. This is because the results of this study showed varied changes in soil properties and native vegetation (species richness, species diversity, percentage cover, and composition) after L. camara clearing. For example, soil moisture and soil penetration resistance showed no significant differences among the invasion conditions; only monthly variations were observed. This is an indication that seasonality influenced these properties. Significantly lower soil infiltration rates were observed in the cleared condition compared to the other conditions and were influenced by the months and the interaction of the clearing conditions and months. The water droplet penetration time showed no significant difference among the clearing conditions over the three months, and all the soil collected from the three clearing conditions was mostly wettable. Soil chemical properties showed that the L. camara invaded and cleared conditions had significantly lower soil pH compared to the uninvaded condition, and an increase in soil pH was observed after clearing L. camara. Vegetation characteristics showed that both the Shannon-Wiener index (H') and the Simpson’s index (D') were lower in the invaded and cleared conditions compared to the uninvaded condition, and significant differences were observed. A slight increase in the H' and D' indices was also observed after clearing L. camara. The mean percentage cover for trees and shrubs was significantly higher in the invaded condition than in the cleared and uninvaded conditions. However, the mean percentage cover of forbs and graminoids was similar among the invaded, cleared, and uninvaded conditions, and no significant differences were observed. When L. camara was cleared, native species recovery was observed and was more notable in the understory species. Overall, some signs of vegetation recovery were observed, although challenges such as secondary invaders and re-invasion by L. camara were noted in the cleared areas. This chapter then concluded that active restoration interventions should be incorporated during restoration to fast-track soil and vegetation recovery. The findings of this thesis will make several significant contributions to the field of biological invasions and provide baseline information that can be used in future studies. These are discussed in the various research chapters. Overall, the thesis concludes that L. camara invasion has varied impacts on native vegetation and soil, and its clearance, should be prioritised to reduce the negative impacts. However, L. camara cleared areas (by WfW in South Africa) require follow-up and monitoring at an early stage to assess vegetation and soil restoration success. In addition, active management measures after L. camara’s removal should be considered for clearing programmes to yield positive ecosystem recovery. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Bolosha, Uviwe
- Date: 2024-10-11
- Subjects: Lantana camara , Restoration and conservation , Restoration ecology , Invasive plants , Physicochemical process , Soil seed banks , Invasion driver
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466524 , vital:76738 , DOI https://doi.org/10.21504/10962/466524
- Description: Invasive alien plants (IAPs) are one of the major contributing factors to biodiversity loss, and Lantana camara is among the top ten alien invaders worldwide. Lantana camara threatens native biodiversity and human health, prevents natural succession, and has an economic and environmental impact globally. With current climate change and future predictions, these IAPs are anticipated to continue posing huge threats to ecosystem composition, structure, and function. Even though L. camara is a widespread IAP, there is still limited knowledge in South Africa on how it influences soil physicochemical properties at the species level, vegetation communities, and soil seed banks at the community level following its invasion. There is also minimal knowledge on the management and control (i.e., clearing for restoration purposes) of L. camara in South Africa, especially in the Eastern Cape province of South Africa. To address the knowledge gap, this thesis was structured into three main aspects: understanding L. camara invasion mechanisms, evaluating invasion impacts on both the aboveground and belowground communities, and invasion management. The main objectives of this thesis were (i) to examine how L. camara invasion (at a species level) affected soil physicochemical properties across different seasons, (ii) to assess how L. camara influences natural vegetation (at a community level), (iii) to examine the effects of L. camara invasion (at the community level) on belowground soil seed banks and also assess the availability of pioneer native species and IAPs in the soil seed banks, and (iv) to evaluate soil and vegetation responses following L. camara clearing in comparison to invaded and uninvaded conditions. To answer these objectives, different studies were carried out in the Eastern Cape province, South Africa, on various farms within the Albany Thicket Biome. The results (Chapter 3) show that L. camara alters and modifies some soil physical properties, such as soil infiltration rate, repellency, and soil penetration resistance, in the communities it invades. A significant decrease in soil penetration under the L. camara canopy was observed compared to soils from the edge and out position. Moreover, significantly faster infiltration rates were observed in the canopy and edge positions than in the out position. The study also observed that these modifications in soil physical properties vary depending on the season. A seasonal comparison in soil penetration showed that soil was more compact in the dry season than the wet season, and significantly faster infiltration rates were observed in summer than in the other seasons. The soil collected under the invaded sampling positions was mostly wettable (80–100%), and not strongly, severely, or extremely repellent across all the seasons. The changes in soil properties caused by L. camara could create favourable conditions for its growth and invasion. Seasonal changes in soil properties also highlight how environmental conditions, especially temperature and rainfall patterns, can affect soil physical properties. The findings in Chapter 4 observed both the negative and positive impacts of L. camara, where the species did not have negative effects on species richness, diversity, or cover of some native species growth forms (i.e., graminoids and forbs). For all species, both species richness and Shannon-Wiener (H’) were significantly higher in the L. camara invaded condition compared to the uninvaded condition. The Simpson’s (J’) and Pielou’s evenness (D’) indices, however, showed no differences between the invasion conditions. Furthermore, the effects of L. camara on vegetation cover were growth form-dependent, with differences being noted for trees and shrubs but not for graminoids and forbs. Changes in vegetation structure and composition were also noted where L. camara created favourable conditions for some species to co-occur with it, meaning that its known trait of changing soil physicochemical properties could benefit some species. Generally, the results of this study showed that the effects of L. camara on vegetation are varied and do not have a predictable pattern, so they should not be generalised. The findings (Chapter 5) also indicate that the L. camara invasion had a negative impact on seedling abundance and composition but not species diversity and richness. This is evident through the decrease in seedling abundance of forbs and graminoids in the L. camara invaded condition. Lantana camara also acted as a refuge for some plant species, mostly native forbs and grasses, including Aptenia cordifolia, Chamaesyce prostrata, Oxalis spp., and Setaria spp., as well as alien forbs such as Bidens pilosa, Plantago lanceolata, and Taraxacum officinale, suggesting L. camara does not entirely eliminate less competitive plant species but can co-exist with them. Lantana camara also displaced some native species, and this could be associated with their displacement in the standing vegetation. Moreover, the species also displaced the seed banks of some alien species, thus showing its competitive ability. Overall, L. camara invasion negatively influenced soil seed bank seedling abundance and composition of some species, but not diversity and richness. The results in Chapter 6 indicated that clearing L. camara is an effective method for reducing its population. However, our findings suggest that clearing alone may not be enough to re-establish these communities with native species. This is because the results of this study showed varied changes in soil properties and native vegetation (species richness, species diversity, percentage cover, and composition) after L. camara clearing. For example, soil moisture and soil penetration resistance showed no significant differences among the invasion conditions; only monthly variations were observed. This is an indication that seasonality influenced these properties. Significantly lower soil infiltration rates were observed in the cleared condition compared to the other conditions and were influenced by the months and the interaction of the clearing conditions and months. The water droplet penetration time showed no significant difference among the clearing conditions over the three months, and all the soil collected from the three clearing conditions was mostly wettable. Soil chemical properties showed that the L. camara invaded and cleared conditions had significantly lower soil pH compared to the uninvaded condition, and an increase in soil pH was observed after clearing L. camara. Vegetation characteristics showed that both the Shannon-Wiener index (H') and the Simpson’s index (D') were lower in the invaded and cleared conditions compared to the uninvaded condition, and significant differences were observed. A slight increase in the H' and D' indices was also observed after clearing L. camara. The mean percentage cover for trees and shrubs was significantly higher in the invaded condition than in the cleared and uninvaded conditions. However, the mean percentage cover of forbs and graminoids was similar among the invaded, cleared, and uninvaded conditions, and no significant differences were observed. When L. camara was cleared, native species recovery was observed and was more notable in the understory species. Overall, some signs of vegetation recovery were observed, although challenges such as secondary invaders and re-invasion by L. camara were noted in the cleared areas. This chapter then concluded that active restoration interventions should be incorporated during restoration to fast-track soil and vegetation recovery. The findings of this thesis will make several significant contributions to the field of biological invasions and provide baseline information that can be used in future studies. These are discussed in the various research chapters. Overall, the thesis concludes that L. camara invasion has varied impacts on native vegetation and soil, and its clearance, should be prioritised to reduce the negative impacts. However, L. camara cleared areas (by WfW in South Africa) require follow-up and monitoring at an early stage to assess vegetation and soil restoration success. In addition, active management measures after L. camara’s removal should be considered for clearing programmes to yield positive ecosystem recovery. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2024
- Full Text:
- Date Issued: 2024-10-11
Assessing the status of the Barotse floodplain fishery and the implications of Australian redclaw crayfish Cherax quadricarinatus invasion on the fishery
- Authors: Nawa, Nawa
- Date: 2024-10-11
- Subjects: Zambezi Floodplains , Fishery resources Zambia Barotse Flood Plain , Introduced fishes Economic aspects , Cherax quadricarinatus , Fishery management
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466803 , vital:76780 , DOI https://doi.org/10.21504/10962/466803
- Description: Inland capture fisheries play an important role of supporting livelihoods of people in developing countries. Despite their significance these fisheries are often poorly monitored resulting in them being undervalued and often missing from policy and decision-making relating to food security and water use, particularly in third world countries. The Anthropocene has given rise to increased pressure on these systems, further justifying the need for monitoring activities to determine the ecosystem service provision status and the levels of existing and emerging threats to such services. This thesis focuses on the Barotse floodplain fishery of the Upper Zambezi system and the potential implications of the recent Cherax quadricarinatus invasion on the floodplain fishery. The thesis specifically assesses the current status of the fishery (Chapter 3), invasion dynamics of C. quadricarinatus (Chapter 4), economic impact of C. quadricarinatus on the fishery (Chapter 5) and fishers’ knowledge, awareness and perception of C. quadricarinatus (Chapter 6). To evaluate the current status of the fishery (Chapter 3), fisheries dependant surveys were conducted. The study revealed a multi-gear multi-species fishery with average catch rates of 5.83 kg per fisher per day and estimated annual harvest of 3123 tonnes per annum. The decline in catch rate, low mean sizes of species harvested, change in species composition, and predominant use of illegal fishing gear compared to previous surveys, suggested further overexploitation of fishery resources. The invasive C. quadricarinatus was identified as the most dominant by-catch species and more prevalent among fishers at the invasion core and in dry season. Analysis of the invasion dynamics of C. quadricarinatus (Chapter 4) involved extensive survey of the Barotse floodplain using collapsible promar traps. The study revealed significant up and down-stream spread from the 2019 range on the floodplain. Relative abundance was higher at the invasion core compared to the invasion edge while male to female sex ratio was not different between these zones, implying both sexes were acting as dispersers. Signals of environmental filtering were not detected while density dependent spatial sorting, and hydrological variation had a strong influence on C. quadricarinatus spread. To quantify economic impact C. quadricarinatus (Chapter 5) creel surveys were conducted during wet and dry season across the invasion range. The study showed that fish damage due to crayfish was limited to gillnets at the invasion core during the dry season and equated to the monetary loss of ~ US$ 21,000 per annum. In addition, gear damage and loss of time due to crayfish was experienced for various fishing gears but most prevalent at the invasion core and more so in dry season. Assessment of fishers’ awareness, knowledge and perception (Chapter 6) involved the use of social surveys administered at the invasion core. This component revealed that most of the respondents were aware of, but not knowledgeable about C. quadricarinatus. Respondents were not aware of any management information relating to C. quadricarinatus and consequently did not follow any management practices. The respondents were supportive of management interventions due to their perceived threat of C. quadricarinatus to the fishery. Age, education, and residence of respondents significantly influenced knowledge and perceptions of C. quadricarinatus. Findings from this study have important implications for the conservation of floodplain wetlands as it informs policy makers to put in place measures that address both overexploitation and aquatic invasive species dynamics to better facilitate sustainability of fisheries and conservation of biodiversity. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Nawa, Nawa
- Date: 2024-10-11
- Subjects: Zambezi Floodplains , Fishery resources Zambia Barotse Flood Plain , Introduced fishes Economic aspects , Cherax quadricarinatus , Fishery management
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466803 , vital:76780 , DOI https://doi.org/10.21504/10962/466803
- Description: Inland capture fisheries play an important role of supporting livelihoods of people in developing countries. Despite their significance these fisheries are often poorly monitored resulting in them being undervalued and often missing from policy and decision-making relating to food security and water use, particularly in third world countries. The Anthropocene has given rise to increased pressure on these systems, further justifying the need for monitoring activities to determine the ecosystem service provision status and the levels of existing and emerging threats to such services. This thesis focuses on the Barotse floodplain fishery of the Upper Zambezi system and the potential implications of the recent Cherax quadricarinatus invasion on the floodplain fishery. The thesis specifically assesses the current status of the fishery (Chapter 3), invasion dynamics of C. quadricarinatus (Chapter 4), economic impact of C. quadricarinatus on the fishery (Chapter 5) and fishers’ knowledge, awareness and perception of C. quadricarinatus (Chapter 6). To evaluate the current status of the fishery (Chapter 3), fisheries dependant surveys were conducted. The study revealed a multi-gear multi-species fishery with average catch rates of 5.83 kg per fisher per day and estimated annual harvest of 3123 tonnes per annum. The decline in catch rate, low mean sizes of species harvested, change in species composition, and predominant use of illegal fishing gear compared to previous surveys, suggested further overexploitation of fishery resources. The invasive C. quadricarinatus was identified as the most dominant by-catch species and more prevalent among fishers at the invasion core and in dry season. Analysis of the invasion dynamics of C. quadricarinatus (Chapter 4) involved extensive survey of the Barotse floodplain using collapsible promar traps. The study revealed significant up and down-stream spread from the 2019 range on the floodplain. Relative abundance was higher at the invasion core compared to the invasion edge while male to female sex ratio was not different between these zones, implying both sexes were acting as dispersers. Signals of environmental filtering were not detected while density dependent spatial sorting, and hydrological variation had a strong influence on C. quadricarinatus spread. To quantify economic impact C. quadricarinatus (Chapter 5) creel surveys were conducted during wet and dry season across the invasion range. The study showed that fish damage due to crayfish was limited to gillnets at the invasion core during the dry season and equated to the monetary loss of ~ US$ 21,000 per annum. In addition, gear damage and loss of time due to crayfish was experienced for various fishing gears but most prevalent at the invasion core and more so in dry season. Assessment of fishers’ awareness, knowledge and perception (Chapter 6) involved the use of social surveys administered at the invasion core. This component revealed that most of the respondents were aware of, but not knowledgeable about C. quadricarinatus. Respondents were not aware of any management information relating to C. quadricarinatus and consequently did not follow any management practices. The respondents were supportive of management interventions due to their perceived threat of C. quadricarinatus to the fishery. Age, education, and residence of respondents significantly influenced knowledge and perceptions of C. quadricarinatus. Findings from this study have important implications for the conservation of floodplain wetlands as it informs policy makers to put in place measures that address both overexploitation and aquatic invasive species dynamics to better facilitate sustainability of fisheries and conservation of biodiversity. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
Assessing the vulnerability of inland fisheries to human-induced perturbation in Lake Kariba fishery, Zambia
- Authors: Imikendu, Imbwae
- Date: 2024-10-11
- Subjects: Fisheries Kariba, Lake (Zambia and Zimbabwe) , Small-scale fisheries , Fishery policy , Biodiversity Kariba, Lake (Zambia and Zimbabwe) , Sustainable livelihood
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466725 , vital:76774 , DOI https://doi.org/10.21504/10962/466725
- Description: Inland fisheries play a critical role in providing nutrition, employment, and ensuring food security among vulnerable groups in Lake Kariba. However, their value is usually undermined in developmental plans, and their contribution to a broader economic development is often undervalued. Over the past two decades, inland fisheries have stagnated. Simultaneously, there have been wide reports of increased fishing effort and declining trends in commercially valuable fish species. This has resulted into a wide socio-economic and environmental problems in various fishing communities. Lake Kariba Zambia, exemplifies this sustainability challenge, where fisheries resources and livelihoods are interlinked. A systematic peer review paper on this topic was documented, published and used for analytical work, focusing on governance and how it affects the utilization of the fisheries resources for food security and biodiversity conservation. This study had four major objectives: (i) to identify threats to fisheries’ productivity in Lake Kariba; (ii) to understand the socio-economic and environmental conditions of small-scale fisheries in Lake Kariba; (iii) to determine adaptation strategies adopted by small-scale fishers in light of the changing socio-economic and environmental conditions in Lake Kariba; (iv) to determine how management of fisheries has to change in response to the wide socio-economic and environmental challenges in the region. Using Ostrom’s framework for analysing socio-ecological systems, various socioeconomic and environmental problems faced by fishing communities in Lake Kariba were examined to devise a sustainable fisheries management plan. The study employed explorative surveys, household questionnaires, key informant interviews, focus group discussions, observations, and a review of literature to elicit secondary data. A proportional quota sampling technique was used to draw a representative sample of 300 small-scale fishers and a typology was developed using a bivariate analysis. Chi-square was used to determine fishing effort over time. Using a curve fitting estimation regression test, a trend analysis in fish production for the past thirteen years (13) years was performed. Results did not show a significant decline in fish production over the past 13 years, yet experts and the fishers reported declining trends in valuable fish species. The finding of this study provides both practical and theoretical lessons that can enhance adaptive capacity and support sustainable livelihoods in the region. A fisheries sector policy is urgently required to guide governance process and coordinate a multi-sectoral perspective to fisheries management if socio-economic progression is to be attained. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Imikendu, Imbwae
- Date: 2024-10-11
- Subjects: Fisheries Kariba, Lake (Zambia and Zimbabwe) , Small-scale fisheries , Fishery policy , Biodiversity Kariba, Lake (Zambia and Zimbabwe) , Sustainable livelihood
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466725 , vital:76774 , DOI https://doi.org/10.21504/10962/466725
- Description: Inland fisheries play a critical role in providing nutrition, employment, and ensuring food security among vulnerable groups in Lake Kariba. However, their value is usually undermined in developmental plans, and their contribution to a broader economic development is often undervalued. Over the past two decades, inland fisheries have stagnated. Simultaneously, there have been wide reports of increased fishing effort and declining trends in commercially valuable fish species. This has resulted into a wide socio-economic and environmental problems in various fishing communities. Lake Kariba Zambia, exemplifies this sustainability challenge, where fisheries resources and livelihoods are interlinked. A systematic peer review paper on this topic was documented, published and used for analytical work, focusing on governance and how it affects the utilization of the fisheries resources for food security and biodiversity conservation. This study had four major objectives: (i) to identify threats to fisheries’ productivity in Lake Kariba; (ii) to understand the socio-economic and environmental conditions of small-scale fisheries in Lake Kariba; (iii) to determine adaptation strategies adopted by small-scale fishers in light of the changing socio-economic and environmental conditions in Lake Kariba; (iv) to determine how management of fisheries has to change in response to the wide socio-economic and environmental challenges in the region. Using Ostrom’s framework for analysing socio-ecological systems, various socioeconomic and environmental problems faced by fishing communities in Lake Kariba were examined to devise a sustainable fisheries management plan. The study employed explorative surveys, household questionnaires, key informant interviews, focus group discussions, observations, and a review of literature to elicit secondary data. A proportional quota sampling technique was used to draw a representative sample of 300 small-scale fishers and a typology was developed using a bivariate analysis. Chi-square was used to determine fishing effort over time. Using a curve fitting estimation regression test, a trend analysis in fish production for the past thirteen years (13) years was performed. Results did not show a significant decline in fish production over the past 13 years, yet experts and the fishers reported declining trends in valuable fish species. The finding of this study provides both practical and theoretical lessons that can enhance adaptive capacity and support sustainable livelihoods in the region. A fisheries sector policy is urgently required to guide governance process and coordinate a multi-sectoral perspective to fisheries management if socio-economic progression is to be attained. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-10-11
Assessment and mitigation of biosecurity risks associated with macroalgae inclusion in farmed abalone diets in South Africa
- Mwangudza, Petronilla Masika
- Authors: Mwangudza, Petronilla Masika
- Date: 2024-10-11
- Subjects: Biosecurity , Seaweed , Abalone culture South Africa , Abalones Feeding and feeds , Haliotis midae , High-throughput nucleotide sequencing
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466748 , vital:76775 , DOI https://doi.org/10.21504/10962/466748
- Description: The provision of biosecure diets for use in intensive aquaculture conditions requires attention, to reduce the risk of introducing potential pathogens to the farmed stock. Such introductions could lead to infections and disease outbreaks. Despite the benefits associated with macroalgae inclusion in abalone diets, several microbial hazard cases have been reported in the animal feed and human food industries. This has necessitated the application of biosecurity measures on fresh macroalgae to reduce or eliminate potential hazards and the risks of pathogen transfer to abalone stock when used as a feed or feed supplement. The present thesis assessed the efficacy of different processing treatments, including heat, ultra-violet irradiation (UVC), different pH levels, salinity concentrations, and povo-iodine on the inactivation of potential macroalgaetransmitted abalone pathogens. The effect of the processed macroalgae on the growth, health and gut microbial composition of abalone were also explored and compared with abalone fed non-processed diets. The efficacy of the different processing treatments was initially assessed on pure cultures of the test pathogens, which included a bacterium (Vibrio anguillarum), an oomycete (Halioticida noduliformans) and the bacteriophage lambda. Data from the initial assessments were then used to select the most optimal treatments for further assessment on the test pathogens inoculated in a macroalgae matrix, to simulate a more natural scenario. The viability of the three test pathogens following exposure to different processing treatments was assessed using culture methods. The results indicated that a combination of three treatments; disinfection using povo-iodine solution (5000 mg/L) for 20 min, oven drying 40 ℃ for 8.0 h and UVC treatment for 10 min rendered all the test pathogens non-culturable. Growth trials were conducted to assess the effect of the biosecure macroalgae Ecklonia maxima, Ulva lacinulata and Gracilaria gracilis on the growth performance of the abalone Haliotis midae. The macroalgae were subjected to the combination of three biosecurity processing treatments and experimental diets were then formulated to incorporate the macroalgae that had been subjected to the biosecurity processing treatments as well as macroalgae that were not. Growth parameters of the abalone after a 150-day feeding trial were compared between the biosecure and non-bioseeure macroalgae dietary treatments. Overall, the lowest growth was observed in the abalone fed with the control diet (AbfeedTM S34R) compared to all the macroalgae diets. However, no significant differences in abalone weight and shell length were recorded between the dietary treatments after the 150-day growth trial with an overall mean final weight (} standard error) of 56.55 } 0.78 g and a mean final length of 66.26 } 0.344 mm (RM-ANOVA: F(18,63) = 0.706; p = 0.792; : F(18,63) = 0.941; p = 0.535 respectively). Similarly, the biosecurity process method (biosecure vs. non-biosecure) did not have an impact on abalone weights and shell length (p > 0.05). Moreover, specific growth rate, length gain and condition factor of abalone did not differ between the biosecure and nonbiosecure dietary treatments with overall means (}standard error) of 0.27 } 0.01 % bw/d, 1.79 } 0.07 mm/month and 1.13 } 0.01, respectively (p > 0.05). Dietary macroalgae are known to contribute to the gut microflora of abalone. To determine if the biosecure process influenced this community complex, a next generation sequencing (NGS) approach was used to identify and compare the bacterial communities in abalone that were fed diets containing macroalgae that had been subjected to biosecurity treatment and those that were not. The NGS approach was also used to determine the gut microbiome profile of the abalone fed with a formulated diet supplemented with fresh U. lacinulata and G. gracilis to assess the potential modulatory effect seaweeds and their associated microbiota may have on the gut microbiome of H. midae. The bacterial alpha diversity did not differ significantly across all the diets at family, genus and species levels (p > 0.05). No significant differences in the microbiome composition were detected indicating little or no dissimilarities of the bacterial communities between the diets for all the biosecure and non-biosecure macroalgae diets. A similar core microbiome was also observed in the digestive tracts of abalone fed with the biosecure and non-biosecure diets. It was concluded that the biosecure process did not influence the natural microbiota of abalone that were fed dietary ingredients that were subjected to the process. The findings of this research have contributed to understanding the production of biosecure macroalgae formulated diets without compromising their benefits to the growth and health of farmed abalone. The combined treatment used in this study can be applied in the macroalgae and the feed industry to produce biosecure feeds. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mwangudza, Petronilla Masika
- Date: 2024-10-11
- Subjects: Biosecurity , Seaweed , Abalone culture South Africa , Abalones Feeding and feeds , Haliotis midae , High-throughput nucleotide sequencing
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466748 , vital:76775 , DOI https://doi.org/10.21504/10962/466748
- Description: The provision of biosecure diets for use in intensive aquaculture conditions requires attention, to reduce the risk of introducing potential pathogens to the farmed stock. Such introductions could lead to infections and disease outbreaks. Despite the benefits associated with macroalgae inclusion in abalone diets, several microbial hazard cases have been reported in the animal feed and human food industries. This has necessitated the application of biosecurity measures on fresh macroalgae to reduce or eliminate potential hazards and the risks of pathogen transfer to abalone stock when used as a feed or feed supplement. The present thesis assessed the efficacy of different processing treatments, including heat, ultra-violet irradiation (UVC), different pH levels, salinity concentrations, and povo-iodine on the inactivation of potential macroalgaetransmitted abalone pathogens. The effect of the processed macroalgae on the growth, health and gut microbial composition of abalone were also explored and compared with abalone fed non-processed diets. The efficacy of the different processing treatments was initially assessed on pure cultures of the test pathogens, which included a bacterium (Vibrio anguillarum), an oomycete (Halioticida noduliformans) and the bacteriophage lambda. Data from the initial assessments were then used to select the most optimal treatments for further assessment on the test pathogens inoculated in a macroalgae matrix, to simulate a more natural scenario. The viability of the three test pathogens following exposure to different processing treatments was assessed using culture methods. The results indicated that a combination of three treatments; disinfection using povo-iodine solution (5000 mg/L) for 20 min, oven drying 40 ℃ for 8.0 h and UVC treatment for 10 min rendered all the test pathogens non-culturable. Growth trials were conducted to assess the effect of the biosecure macroalgae Ecklonia maxima, Ulva lacinulata and Gracilaria gracilis on the growth performance of the abalone Haliotis midae. The macroalgae were subjected to the combination of three biosecurity processing treatments and experimental diets were then formulated to incorporate the macroalgae that had been subjected to the biosecurity processing treatments as well as macroalgae that were not. Growth parameters of the abalone after a 150-day feeding trial were compared between the biosecure and non-bioseeure macroalgae dietary treatments. Overall, the lowest growth was observed in the abalone fed with the control diet (AbfeedTM S34R) compared to all the macroalgae diets. However, no significant differences in abalone weight and shell length were recorded between the dietary treatments after the 150-day growth trial with an overall mean final weight (} standard error) of 56.55 } 0.78 g and a mean final length of 66.26 } 0.344 mm (RM-ANOVA: F(18,63) = 0.706; p = 0.792; : F(18,63) = 0.941; p = 0.535 respectively). Similarly, the biosecurity process method (biosecure vs. non-biosecure) did not have an impact on abalone weights and shell length (p > 0.05). Moreover, specific growth rate, length gain and condition factor of abalone did not differ between the biosecure and nonbiosecure dietary treatments with overall means (}standard error) of 0.27 } 0.01 % bw/d, 1.79 } 0.07 mm/month and 1.13 } 0.01, respectively (p > 0.05). Dietary macroalgae are known to contribute to the gut microflora of abalone. To determine if the biosecure process influenced this community complex, a next generation sequencing (NGS) approach was used to identify and compare the bacterial communities in abalone that were fed diets containing macroalgae that had been subjected to biosecurity treatment and those that were not. The NGS approach was also used to determine the gut microbiome profile of the abalone fed with a formulated diet supplemented with fresh U. lacinulata and G. gracilis to assess the potential modulatory effect seaweeds and their associated microbiota may have on the gut microbiome of H. midae. The bacterial alpha diversity did not differ significantly across all the diets at family, genus and species levels (p > 0.05). No significant differences in the microbiome composition were detected indicating little or no dissimilarities of the bacterial communities between the diets for all the biosecure and non-biosecure macroalgae diets. A similar core microbiome was also observed in the digestive tracts of abalone fed with the biosecure and non-biosecure diets. It was concluded that the biosecure process did not influence the natural microbiota of abalone that were fed dietary ingredients that were subjected to the process. The findings of this research have contributed to understanding the production of biosecure macroalgae formulated diets without compromising their benefits to the growth and health of farmed abalone. The combined treatment used in this study can be applied in the macroalgae and the feed industry to produce biosecure feeds. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2024
- Full Text:
- Date Issued: 2024-10-11
Becoming a [COVID] student?: assessing the impact of COVID-19 on first-year students’ experiences of higher education in the Eastern Cape, South Africa
- Authors: Nebbe, Kelsey Ann
- Date: 2024-10-11
- Subjects: Rite of passage , COVID-19 Pandemic, 2020-2023 Influence , College freshmen South Africa Eastern Cape , Liminality , Communitas
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/466295 , vital:76715
- Description: In 2020, the COVID-19 pandemic disrupted South African higher education which forced the shift to emergency distance learning to save the academic years of 2020-2022. The repercussions of this are still emerging, but current literature focuses on understanding the impact of first-year students is focused on the impact of academics caused by the emergency shift to online, the “double transition” as Nyar (2021) termed the adjustment to university and then again to the online emergency academics. There is also a niche for holistic research to be done regarding the student experience - pandemic times and elsewise. My thesis focuses on the journey of studenthood of three cohorts at a residential university in the Eastern Cape, South Africa, through the COVID-19 pandemic of 2020-2022. This research utilises ethnographic iterative mixed methods (questionnaire, interviews, focus groups and participant observation) and the theoretical lens of Rites of Passage to understand my research participant’s experiences. My findings are that due to the circumstances of an incomplete student experience of just online academics provided an continuous liminal period for first-year students of 2020-2021, with little to no opportunity for them to develop a connection to the university community. The opportunity for them to holistically become students arises at the end of the pandemic in 2022, with the restrictions lifting and the return to on-campus and in-person academic activities allowing them to have a first-year experienced that COVID-19 prohibited. , Thesis (MSocSci) -- Faculty of Humanities, Anthropology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Nebbe, Kelsey Ann
- Date: 2024-10-11
- Subjects: Rite of passage , COVID-19 Pandemic, 2020-2023 Influence , College freshmen South Africa Eastern Cape , Liminality , Communitas
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/466295 , vital:76715
- Description: In 2020, the COVID-19 pandemic disrupted South African higher education which forced the shift to emergency distance learning to save the academic years of 2020-2022. The repercussions of this are still emerging, but current literature focuses on understanding the impact of first-year students is focused on the impact of academics caused by the emergency shift to online, the “double transition” as Nyar (2021) termed the adjustment to university and then again to the online emergency academics. There is also a niche for holistic research to be done regarding the student experience - pandemic times and elsewise. My thesis focuses on the journey of studenthood of three cohorts at a residential university in the Eastern Cape, South Africa, through the COVID-19 pandemic of 2020-2022. This research utilises ethnographic iterative mixed methods (questionnaire, interviews, focus groups and participant observation) and the theoretical lens of Rites of Passage to understand my research participant’s experiences. My findings are that due to the circumstances of an incomplete student experience of just online academics provided an continuous liminal period for first-year students of 2020-2021, with little to no opportunity for them to develop a connection to the university community. The opportunity for them to holistically become students arises at the end of the pandemic in 2022, with the restrictions lifting and the return to on-campus and in-person academic activities allowing them to have a first-year experienced that COVID-19 prohibited. , Thesis (MSocSci) -- Faculty of Humanities, Anthropology, 2024
- Full Text:
- Date Issued: 2024-10-11
Bio-vectoring by honeybees and symbiosis: a combined approach to controlling Botrytis mould on strawberry
- Authors: Starbuck, Megan
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/463985 , vital:76463
- Description: Access restricted. Exxpected release in 2026. , Thesis (MSc) -- Faculty of Science, Biochemistry, Microbiology & Bioinformatics, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Starbuck, Megan
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/463985 , vital:76463
- Description: Access restricted. Exxpected release in 2026. , Thesis (MSc) -- Faculty of Science, Biochemistry, Microbiology & Bioinformatics, 2024
- Full Text:
- Date Issued: 2024-10-11
Biological control of torch cactus in South Africa: finding a suitable agent for a non-native weed with an unknown indigenous distribution
- Authors: Griffith, Tamzin Camilla
- Date: 2024-10-11
- Subjects: Trichocereus spachianus , Invasive plants Biological control , Dactylopius , Hypogeococcus , Host specificity
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466781 , vital:76778 , DOI https://doi.org/10.21504/10962/466781
- Description: Trichocereus spachianus is an invasive cactus species in South Africa and poses challenges as a target for biological control due to confusion around its taxonomy and origin. Adapted to arid environments, this cactus is of particular concern in dry savannah and Karoo biomes, where its invasion of rangelands reduces grazing capacity for both indigenous wildlife and livestock. While previous records indicate that T. spachianus is indigenous to Argentina, recent field surveys have failed to verify its presence. Determining the origin of the target weed was important in developing a biological control programme since it enables the collection of potential agents directly from native populations of the target plant. Successful biological control programmes against cactus species in South Africa have often involved utilising both new associations and oligophagous insects, made possible because of the lack of indigenous and valued cacti in the region. Lack of T. spachianus locations in the native distribution, meant direct collection of insects from the target weed was not possible. Efforts to find biological control agents were focused on new associations between closely related cacti and their oligophagous herbivores. Suitability of multiple Hypogeococcus (mealybug) entities and a cochineal species, Dactylopius confertus, were investigated for their efficacy on various South African weedy cactus species, including T. spachianus. Findings revealed that none of the Hypogeococcus entities (species or lineages) were effective biological control agents, but D. confertus demonstrated potential as a biological control agent with a relatively high fecundity and survival rate on T. spachianus. Efficacy trials indicated that D. confertus could reach population densities sufficient to cause mortality of T. spachianus plants. Limited host specificity trials revealed that D. confertus was suitably host specific for release in South Africa, provided host specificity testing was conducted on additional plants. Approval and release of D. confertus has the potential to reduce the invasiveness of this damaging cactus in a sustainable and environmentally friendly manner. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Griffith, Tamzin Camilla
- Date: 2024-10-11
- Subjects: Trichocereus spachianus , Invasive plants Biological control , Dactylopius , Hypogeococcus , Host specificity
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466781 , vital:76778 , DOI https://doi.org/10.21504/10962/466781
- Description: Trichocereus spachianus is an invasive cactus species in South Africa and poses challenges as a target for biological control due to confusion around its taxonomy and origin. Adapted to arid environments, this cactus is of particular concern in dry savannah and Karoo biomes, where its invasion of rangelands reduces grazing capacity for both indigenous wildlife and livestock. While previous records indicate that T. spachianus is indigenous to Argentina, recent field surveys have failed to verify its presence. Determining the origin of the target weed was important in developing a biological control programme since it enables the collection of potential agents directly from native populations of the target plant. Successful biological control programmes against cactus species in South Africa have often involved utilising both new associations and oligophagous insects, made possible because of the lack of indigenous and valued cacti in the region. Lack of T. spachianus locations in the native distribution, meant direct collection of insects from the target weed was not possible. Efforts to find biological control agents were focused on new associations between closely related cacti and their oligophagous herbivores. Suitability of multiple Hypogeococcus (mealybug) entities and a cochineal species, Dactylopius confertus, were investigated for their efficacy on various South African weedy cactus species, including T. spachianus. Findings revealed that none of the Hypogeococcus entities (species or lineages) were effective biological control agents, but D. confertus demonstrated potential as a biological control agent with a relatively high fecundity and survival rate on T. spachianus. Efficacy trials indicated that D. confertus could reach population densities sufficient to cause mortality of T. spachianus plants. Limited host specificity trials revealed that D. confertus was suitably host specific for release in South Africa, provided host specificity testing was conducted on additional plants. Approval and release of D. confertus has the potential to reduce the invasiveness of this damaging cactus in a sustainable and environmentally friendly manner. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
Biology and management of the fruit piercing moth Serrodes partita in citrus orchards
- Authors: Mushore, Tapiwa Gift
- Date: 2024-10-11
- Subjects: Baculoviruses , Moths Monitoring , Pests Control , Insect traps , Citrus Diseases and pests South Africa Kat River Valley , Catapult moth
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466792 , vital:76779 , DOI https://doi.org/10.21504/10962/466792
- Description: The fruit-piercing moth, Serrodes partita (Fabricius) (Lepidoptera: Erebidae), is a polyphagous, multivoltine pest of citrus. This insect has a distinct geographical separation between its larval and adult stages, each with different feeding patterns. During the larval stage, it primarily acts as a forest defoliator, feeding mostly on Jacket plum, Pappea capensis Eckl. & Zeyh. (Sapindaceae). In contrast, the adult stage of this moth feeds on both tropical and subtropical fruit, including citrus and can cause serious economic losses. The adult moth uses its sclerotised proboscis to pierce the skin of ripening or ripe fruit, from which it extracts the juice. This piercing action initiates a fermentation process within the fruit, attracting other secondary-feeding moths, commonly referred to as fruit-sucking moths. As a result of the feeding activity, the affected fruit eventually rot, drop to the ground, and become unsuitable for the market. Serrodes partita exhibits an outbreak life strategy, reoccurring every 5 to 10 years. In South Africa's Eastern Cape Province, specifically in the Upper Kat River Valley, citrus growers have expressed concerns about the impact of this moth on soft citrus (Satsumas and Clementines). This raises the possibility of a shift in the population dynamics of S. partita, where these occurrences become more frequent and less sporadic. Such a trend poses a significant threat to fruit arboriculture in the Eastern Cape region. Currently, there are limited management strategies available for managing fruit-piecing moths. The use of pesticides is not a feasible option for ripe or nearly ripe fruit, and is ineffective against the adult moth. Alternative control methods, such as orchard netting and light barriers, either come with high costs or are impractical for large-scale citrus production. Given the limited range of management options, combined with the moth's tendency for sudden outbreaks, citrus growers find themselves without effective means to manage this pest. The objective of this study was, therefore, to investigate the biology of S. partita and explore various control options to effectively manage this pest. Research focused on the biology and laboratory rearing of larval stages of S. partita. The flight behaviour, feeding patterns, and preferences of adult S. partita within citrus orchards were also explored. The aim was to elucidate key fundamental aspects, including whether the same population frequents a particular orchard, and if infestations within orchards exhibit a specific direction. Lure type and lure presentation method trials were conducted to determine the most effective lure and trap design. Seasonal monitoring of S. partita in soft citrus orchards was conducted over three years to determine its outbreak status in the Committee’s Drift area and the role of weather variables in the activity of the moth. Damage assessments were also conducted alongside monitoring to determine the level of damage inflicted by S. partita. Natural enemies associated with S. partita were explored to determine the prevalence and causes of mortality in late instars during laboratory rearing. Rearing S. partita on an artificial diet was unsuccessful despite several modifications. The moth, however, completed its entire life cycle on its natural host, P. capensis in the laboratory. The total life cycle from egg to adult took 80.7 ± 3.6 days, the larval stage lasted 52.3 ± 2.8 days, and the pupal stage lasted 25.8 ± 3.6 days at 21°C. The investigation into the biology of S. partita also brought attention to the most susceptible stages of its growth, with high mortality rates recorded among neonates and late instars. The findings of the study revealed directional patterns of moth infestations, with higher numbers observed at the orchard's periphery leading towards natural vegetation. This raises the prospect of using sacrificial rows on the edge of a citrus orchard to concentrate moth feeding damage during outbreak years. Using a mark and recapture technique, the study showed that a relatively small proportion (4.5 %) of moths tended to revisit the same orchard. The moths strongly preferred damaged fruit (85 %) over undamaged fruit. Visible damage (rotting symptoms) typically became apparent within 3 to 5 days. Satsumas had a higher number of feeding scars (2.1) than Clementines (1.08), highlighting their susceptibility. The study also established that, on average, pierced soft citrus fruit takes about four days to display symptoms of decay. Synthetic proprietary Australian lures were ineffective at attracting the moth, whereas fresh bananas proved to be a successful lure. Furthermore, the addition of both Agar and Super absorbent polymer showed promise as thickening agents to enhance the longevity of fresh bananas in traps. The effectiveness of various trap designs was compared, including the funnel trap, delta trap, bucket trap, and circular trap, in capturing fruit-feeding moths. The funnel trap performed best as it captured the most moths, followed by the delta trap, Lynfield trap and disc trap, respectively. Additionally, an electronic enhancement to the funnel trap, incorporating a zapper element, improved efficiency. However, efforts to exploit both visual and olfactory cues through the inclusion of an Ultraviolet (UV) light component did not improve its effectiveness. No extensive outbreaks were recorded during the study; however, population variations of S. partita populations were recorded. Annual trends showed two population peaks, with the first peak recorded from December to March, while the second peak was recorded from April to July. The activity of the moths also differed across different months, with the highest peaks recorded in May, while no moths were recorded from August to November. Both cultivar type and farm location did not influence the occurrence of the moth. Meanwhile cumulative weather parameters (rainfall, temperature and humidity) from the four months prior to occurrence influenced the activity of S. partita. Temperature determined the timing of the outbreak, while rainfall determined the magnitude of the outbreak. Damage assessment showed very low fruit damage by S. partita throughout the monitoring period. Varying levels of infestation by a tachinid fly, 4 % and 35 %, were recorded for 2021 and 2022, respectively. The tachinid parasitoid could not be identified at the species level. A novel baculovirus, tentatively classified as S. partita NPV (SepaNPV), was identified as the larval mortality causative agent. This study enhanced our understanding of S. partita's biology and population dynamics, providing valuable insights for developing effective management strategies against this economically impactful citrus pest. Future research should focus on refining control measures and addressing the challenges of the adult moth's elusive nature. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mushore, Tapiwa Gift
- Date: 2024-10-11
- Subjects: Baculoviruses , Moths Monitoring , Pests Control , Insect traps , Citrus Diseases and pests South Africa Kat River Valley , Catapult moth
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466792 , vital:76779 , DOI https://doi.org/10.21504/10962/466792
- Description: The fruit-piercing moth, Serrodes partita (Fabricius) (Lepidoptera: Erebidae), is a polyphagous, multivoltine pest of citrus. This insect has a distinct geographical separation between its larval and adult stages, each with different feeding patterns. During the larval stage, it primarily acts as a forest defoliator, feeding mostly on Jacket plum, Pappea capensis Eckl. & Zeyh. (Sapindaceae). In contrast, the adult stage of this moth feeds on both tropical and subtropical fruit, including citrus and can cause serious economic losses. The adult moth uses its sclerotised proboscis to pierce the skin of ripening or ripe fruit, from which it extracts the juice. This piercing action initiates a fermentation process within the fruit, attracting other secondary-feeding moths, commonly referred to as fruit-sucking moths. As a result of the feeding activity, the affected fruit eventually rot, drop to the ground, and become unsuitable for the market. Serrodes partita exhibits an outbreak life strategy, reoccurring every 5 to 10 years. In South Africa's Eastern Cape Province, specifically in the Upper Kat River Valley, citrus growers have expressed concerns about the impact of this moth on soft citrus (Satsumas and Clementines). This raises the possibility of a shift in the population dynamics of S. partita, where these occurrences become more frequent and less sporadic. Such a trend poses a significant threat to fruit arboriculture in the Eastern Cape region. Currently, there are limited management strategies available for managing fruit-piecing moths. The use of pesticides is not a feasible option for ripe or nearly ripe fruit, and is ineffective against the adult moth. Alternative control methods, such as orchard netting and light barriers, either come with high costs or are impractical for large-scale citrus production. Given the limited range of management options, combined with the moth's tendency for sudden outbreaks, citrus growers find themselves without effective means to manage this pest. The objective of this study was, therefore, to investigate the biology of S. partita and explore various control options to effectively manage this pest. Research focused on the biology and laboratory rearing of larval stages of S. partita. The flight behaviour, feeding patterns, and preferences of adult S. partita within citrus orchards were also explored. The aim was to elucidate key fundamental aspects, including whether the same population frequents a particular orchard, and if infestations within orchards exhibit a specific direction. Lure type and lure presentation method trials were conducted to determine the most effective lure and trap design. Seasonal monitoring of S. partita in soft citrus orchards was conducted over three years to determine its outbreak status in the Committee’s Drift area and the role of weather variables in the activity of the moth. Damage assessments were also conducted alongside monitoring to determine the level of damage inflicted by S. partita. Natural enemies associated with S. partita were explored to determine the prevalence and causes of mortality in late instars during laboratory rearing. Rearing S. partita on an artificial diet was unsuccessful despite several modifications. The moth, however, completed its entire life cycle on its natural host, P. capensis in the laboratory. The total life cycle from egg to adult took 80.7 ± 3.6 days, the larval stage lasted 52.3 ± 2.8 days, and the pupal stage lasted 25.8 ± 3.6 days at 21°C. The investigation into the biology of S. partita also brought attention to the most susceptible stages of its growth, with high mortality rates recorded among neonates and late instars. The findings of the study revealed directional patterns of moth infestations, with higher numbers observed at the orchard's periphery leading towards natural vegetation. This raises the prospect of using sacrificial rows on the edge of a citrus orchard to concentrate moth feeding damage during outbreak years. Using a mark and recapture technique, the study showed that a relatively small proportion (4.5 %) of moths tended to revisit the same orchard. The moths strongly preferred damaged fruit (85 %) over undamaged fruit. Visible damage (rotting symptoms) typically became apparent within 3 to 5 days. Satsumas had a higher number of feeding scars (2.1) than Clementines (1.08), highlighting their susceptibility. The study also established that, on average, pierced soft citrus fruit takes about four days to display symptoms of decay. Synthetic proprietary Australian lures were ineffective at attracting the moth, whereas fresh bananas proved to be a successful lure. Furthermore, the addition of both Agar and Super absorbent polymer showed promise as thickening agents to enhance the longevity of fresh bananas in traps. The effectiveness of various trap designs was compared, including the funnel trap, delta trap, bucket trap, and circular trap, in capturing fruit-feeding moths. The funnel trap performed best as it captured the most moths, followed by the delta trap, Lynfield trap and disc trap, respectively. Additionally, an electronic enhancement to the funnel trap, incorporating a zapper element, improved efficiency. However, efforts to exploit both visual and olfactory cues through the inclusion of an Ultraviolet (UV) light component did not improve its effectiveness. No extensive outbreaks were recorded during the study; however, population variations of S. partita populations were recorded. Annual trends showed two population peaks, with the first peak recorded from December to March, while the second peak was recorded from April to July. The activity of the moths also differed across different months, with the highest peaks recorded in May, while no moths were recorded from August to November. Both cultivar type and farm location did not influence the occurrence of the moth. Meanwhile cumulative weather parameters (rainfall, temperature and humidity) from the four months prior to occurrence influenced the activity of S. partita. Temperature determined the timing of the outbreak, while rainfall determined the magnitude of the outbreak. Damage assessment showed very low fruit damage by S. partita throughout the monitoring period. Varying levels of infestation by a tachinid fly, 4 % and 35 %, were recorded for 2021 and 2022, respectively. The tachinid parasitoid could not be identified at the species level. A novel baculovirus, tentatively classified as S. partita NPV (SepaNPV), was identified as the larval mortality causative agent. This study enhanced our understanding of S. partita's biology and population dynamics, providing valuable insights for developing effective management strategies against this economically impactful citrus pest. Future research should focus on refining control measures and addressing the challenges of the adult moth's elusive nature. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-10-11
Border crossing, collecting, gravitating: small narratives of three ordinary collectors in the Chinese diaspora in South Africa since the late 1980s
- Authors: Grobbelaar, Binjun
- Date: 2024-10-11
- Subjects: Chinese diaspora , Art Collectors and collecting South Africa , Autobiography in art , Art History , Knowledge, Sociology of , Proximity
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/467039 , vital:76809 , DOI https://doi.org/10.21504/10962/467039
- Description: Shifting away from the conventional viewpoint that confines art collecting predominantly to established structures like art institutions, markets, and exclusive collector networks, a trajectory historically influenced by Western collecting traditions and museology, this thesis takes a radical turn by delving into the small narratives of three ordinary Chinese collectors, namely Shengkai Wu, Yiyuan Yang and Shudi Li, who immigrated to South Africa since the late 1980s. The focus on Chinese collectors and migration resonates with my positionality as a recent Chinese immigrant in South Africa and aligns with Boaventura de Sousa Santos’s approach to proximity in knowledge-making, which emphasises ‘knowing with’ and ‘walking alongside’ the subjects of study. The selected immigrant collectors were chosen based on their current low-to-middle economic status in South Africa. These three individuals have decades of living and artcollecting experience in the country, having held professional backgrounds in China prior to their immigration. The number of collectors was determined through an in-depth qualitative biographical research method, taking into account the niche field of art collecting and the relatively small Chinese population within the broader South African demographic. It approaches collecting as a method of pursuing clues and explores it as a socio-cultural practice by collaging the biographies of three ordinary collectors as micro-histories. Details of these ordinary lives are entangled with the lives of objects that traverse China and South Africa. The use of non-official data, at times fragmented and partially obscured, is employed to craft a narrative that weaves together diverse and complex perspectives. The aim of this thesis is to attempt to shift from elite collecting narratives to a more diverse understanding of the global circulation and appropriation of art and cultural objects in relation to grassroots migration. This shift is explored through the unique insights derived from recovering the personal narratives of ordinary immigrant collectors and their associated objects in overlooked geographical locations and states of transformation within the context of China– Africa relations. I engage China–Africa relations within the framework Global South, seeks to address the limitations of describing the multi-dimensional interweaving of low-profile individual and objecthood, unofficial and official, historical and ephemeral relationships in the burgeoning field of China-Africa relations. The investigation unfolds through two interconnected aspects embedded in the development of each collector’s biography. Firstly, it delves into how the collecting practices of these three Chinese collectors are interwoven with their experiences in both China and South Africa. Secondly, it examines the agencies of the collectors and the relationships they establish with the objects they collect. I approach these collectors as curators of their autobiographical exhibitions in the process of preliminary data collection and subsequent thematic and object-oriented interviews. Through the analysis of collectors’ oral, visual and written narratives, as well as the biographies of objects, this PhD thesis in Art History uncovers a multilayered influx of crossways of knowledge-making by the collectors on the ground. Inspired by practical material re-ordering and personal interests, these collectors engage in configuring the border-crossing process within the Chinese diaspora in South Africa. Recurring narratives of critical socialist experiences in Maoist China are linked to their suppressed agency and subsequent recovery through emigration to South Africa. They negotiate a complex diasporic terrain marked by engaging with socialist philately materials, persistently gravitating towards China. Concurrently, they transcend conventional nation-state framework, accentuating the convergent aesthetic qualities inherent in transnational artefacts and community-based art practices. The collectors’ engagement with exported Chinese “specialised arts and crafts”, and unconventional artefacts, such as philately materials, creates a bottom-up fresh interpretation of what constitutes collecting Chinese art in the context of South Africa. Fragments of British colonial history on the Rand, Chinese semi-colonial history, and contemporary printmaking in both China and South Africa, embedded in tangible material artefacts and in intangible visual connection, become visible through their logics of collecting and affective approach from the bottom up. Highlighting the often-overlooked Chinese agency in the creation of these objects, this research illustrates how individual mobility between China and Africa can contribute to the nuanced role of aesthetics through collecting, redefining what is visible and meaningful in the context of the Chinese diaspora and art collecting in South Africa. Specifically, discourses on the border poetics of Zheng He, colonial postcards and notices on the Rand, visual connection in printmaking, and Chinese semi-colonial artefacts of a converged “Chinese–British” aesthetic and a controversial Tang blue-and-white dish are instances where ordinary Chinese collectors in the Global South strategically mobilise collecting as a means to migrate towards an alternative politics of hope, as conceptualised by Chiara Brambilla. This hope presents a “strategic Southerness,” cultivates an “alter-geopolitics of knowledge” (Simbao 2017) that, pushing against the often-dominant representation of spectacle within the structured frameworks of art institutions, markets and networks of elite collectors. I argue that these emerging themes and objects in the collectors’ narratives represent a grounded, localised knowledge-making from below, unfolding practices underpinned by the material conditions of ordinary collectors of art and material culture in the Global South, aspects that have not been given adequate attention in history. In the process of encountering, reassembling, and appropriating these material objects and associating people in South Africa, I argue that collecting becomes not only an act of diasporic agency in constructing memories of the past, but also offers insight into the complex Chinese diaspora within the dynamics of a rising Chinese presence in Africa. On the one hand, these ordinary collectors employ collecting as an act of resistance against the aftermath of political turmoil and the epistemological inequality imposed on grassroots communities. Their emergence has contributed to transforming the residual colonial culture of the “othering” in the landscape of art collecting in South Africa. On the other hand, their agency intersects with Chinese diasporic nationalism, which lingers in the tension between internalised Eurocentric exploitation and romanticised appreciation and cultural preservation, a question that awaits for further investigation. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Grobbelaar, Binjun
- Date: 2024-10-11
- Subjects: Chinese diaspora , Art Collectors and collecting South Africa , Autobiography in art , Art History , Knowledge, Sociology of , Proximity
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/467039 , vital:76809 , DOI https://doi.org/10.21504/10962/467039
- Description: Shifting away from the conventional viewpoint that confines art collecting predominantly to established structures like art institutions, markets, and exclusive collector networks, a trajectory historically influenced by Western collecting traditions and museology, this thesis takes a radical turn by delving into the small narratives of three ordinary Chinese collectors, namely Shengkai Wu, Yiyuan Yang and Shudi Li, who immigrated to South Africa since the late 1980s. The focus on Chinese collectors and migration resonates with my positionality as a recent Chinese immigrant in South Africa and aligns with Boaventura de Sousa Santos’s approach to proximity in knowledge-making, which emphasises ‘knowing with’ and ‘walking alongside’ the subjects of study. The selected immigrant collectors were chosen based on their current low-to-middle economic status in South Africa. These three individuals have decades of living and artcollecting experience in the country, having held professional backgrounds in China prior to their immigration. The number of collectors was determined through an in-depth qualitative biographical research method, taking into account the niche field of art collecting and the relatively small Chinese population within the broader South African demographic. It approaches collecting as a method of pursuing clues and explores it as a socio-cultural practice by collaging the biographies of three ordinary collectors as micro-histories. Details of these ordinary lives are entangled with the lives of objects that traverse China and South Africa. The use of non-official data, at times fragmented and partially obscured, is employed to craft a narrative that weaves together diverse and complex perspectives. The aim of this thesis is to attempt to shift from elite collecting narratives to a more diverse understanding of the global circulation and appropriation of art and cultural objects in relation to grassroots migration. This shift is explored through the unique insights derived from recovering the personal narratives of ordinary immigrant collectors and their associated objects in overlooked geographical locations and states of transformation within the context of China– Africa relations. I engage China–Africa relations within the framework Global South, seeks to address the limitations of describing the multi-dimensional interweaving of low-profile individual and objecthood, unofficial and official, historical and ephemeral relationships in the burgeoning field of China-Africa relations. The investigation unfolds through two interconnected aspects embedded in the development of each collector’s biography. Firstly, it delves into how the collecting practices of these three Chinese collectors are interwoven with their experiences in both China and South Africa. Secondly, it examines the agencies of the collectors and the relationships they establish with the objects they collect. I approach these collectors as curators of their autobiographical exhibitions in the process of preliminary data collection and subsequent thematic and object-oriented interviews. Through the analysis of collectors’ oral, visual and written narratives, as well as the biographies of objects, this PhD thesis in Art History uncovers a multilayered influx of crossways of knowledge-making by the collectors on the ground. Inspired by practical material re-ordering and personal interests, these collectors engage in configuring the border-crossing process within the Chinese diaspora in South Africa. Recurring narratives of critical socialist experiences in Maoist China are linked to their suppressed agency and subsequent recovery through emigration to South Africa. They negotiate a complex diasporic terrain marked by engaging with socialist philately materials, persistently gravitating towards China. Concurrently, they transcend conventional nation-state framework, accentuating the convergent aesthetic qualities inherent in transnational artefacts and community-based art practices. The collectors’ engagement with exported Chinese “specialised arts and crafts”, and unconventional artefacts, such as philately materials, creates a bottom-up fresh interpretation of what constitutes collecting Chinese art in the context of South Africa. Fragments of British colonial history on the Rand, Chinese semi-colonial history, and contemporary printmaking in both China and South Africa, embedded in tangible material artefacts and in intangible visual connection, become visible through their logics of collecting and affective approach from the bottom up. Highlighting the often-overlooked Chinese agency in the creation of these objects, this research illustrates how individual mobility between China and Africa can contribute to the nuanced role of aesthetics through collecting, redefining what is visible and meaningful in the context of the Chinese diaspora and art collecting in South Africa. Specifically, discourses on the border poetics of Zheng He, colonial postcards and notices on the Rand, visual connection in printmaking, and Chinese semi-colonial artefacts of a converged “Chinese–British” aesthetic and a controversial Tang blue-and-white dish are instances where ordinary Chinese collectors in the Global South strategically mobilise collecting as a means to migrate towards an alternative politics of hope, as conceptualised by Chiara Brambilla. This hope presents a “strategic Southerness,” cultivates an “alter-geopolitics of knowledge” (Simbao 2017) that, pushing against the often-dominant representation of spectacle within the structured frameworks of art institutions, markets and networks of elite collectors. I argue that these emerging themes and objects in the collectors’ narratives represent a grounded, localised knowledge-making from below, unfolding practices underpinned by the material conditions of ordinary collectors of art and material culture in the Global South, aspects that have not been given adequate attention in history. In the process of encountering, reassembling, and appropriating these material objects and associating people in South Africa, I argue that collecting becomes not only an act of diasporic agency in constructing memories of the past, but also offers insight into the complex Chinese diaspora within the dynamics of a rising Chinese presence in Africa. On the one hand, these ordinary collectors employ collecting as an act of resistance against the aftermath of political turmoil and the epistemological inequality imposed on grassroots communities. Their emergence has contributed to transforming the residual colonial culture of the “othering” in the landscape of art collecting in South Africa. On the other hand, their agency intersects with Chinese diasporic nationalism, which lingers in the tension between internalised Eurocentric exploitation and romanticised appreciation and cultural preservation, a question that awaits for further investigation. , Thesis (PhD) -- Faculty of Humanities, Fine Art, 2024
- Full Text:
- Date Issued: 2024-10-11
Burgernomics: Raw BMI vs Adjusted BMI. A comparative analysis of appropriate exchange rate valuation measures
- Gumedze, Siyanda Nakiwe Nomfundo
- Authors: Gumedze, Siyanda Nakiwe Nomfundo
- Date: 2024-10-11
- Subjects: Big Mac Index , Purchasing power parity , Foreign exchange rates , Foreign exchange market , Economic theory
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/462702 , vital:76327
- Description: The Big Mac Index was developed in 1986 by The Economist magazine as a playful take on the Purchasing Power Parity theory. Its purpose is to indicate whether a currency is overpriced or undervalued in relation to the real exchange rate and whether it can be used as a reliable indicator of exchange rate predictions. There are two versions of the Big Mac Index: the raw Big Mac Index and the adjusted Big Mac Index. If appropriate, this index might be developed into an economic theory that can be applied to corporate finance, international trade, and international finance. To determine which Big Mac Index measure is a better indicator of exchange rate valuation, a comparison analysis was conducted. This study set out to determine how well the adjusted Big Mac Index performed as a gauge for exchange rate valuation. The research then compares the two Big Mac Index measures' ability to anticipate future exchange rates in order to determine which is more accurate. Data from the South African Reserve Bank and The Economist databases covering 37 nations from 2000 to 2022 were used for the analysis. Exchange rate misalignment trends were assessed globally, and the results indicated that the adjusted BMI was a more accurate measure of purchasing power. Tests of correlation revealed that there was a positive association between the real exchange rate and the Big Mac Index. Findings from a panel ARDL Model indicated that taking into consideration country-specific GDP variations and group heterogeneity can enhance the real exchange rates' ability to predict the raw BMI. The research also focused on the South African Rand to ascertain whether the Big Mac Index validates the Purchasing Power Parity theoretical framework. Using cointegration tests and graphic analysis, it was possible to find evidence for a cointegrating relationship between the real exchange rate and the Big Mac Index measures during the last 20 years. Additionally, a positive correlation between the modified Big Mac Index and terms of trade was discovered in the results, confirming the hypothesis that the Big Mac Index satisfies current account assumptions. Finally, a VEC model demonstrated that the modified BMI outperforms the raw BMI in terms of forecasting estimates. Overall, the study found that the Big Mac Index is more than a bit of fun as per its origin. The results showed that the adjusted Big Mac Index has practical applications and the potential to be considered as an economic theory. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Gumedze, Siyanda Nakiwe Nomfundo
- Date: 2024-10-11
- Subjects: Big Mac Index , Purchasing power parity , Foreign exchange rates , Foreign exchange market , Economic theory
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/462702 , vital:76327
- Description: The Big Mac Index was developed in 1986 by The Economist magazine as a playful take on the Purchasing Power Parity theory. Its purpose is to indicate whether a currency is overpriced or undervalued in relation to the real exchange rate and whether it can be used as a reliable indicator of exchange rate predictions. There are two versions of the Big Mac Index: the raw Big Mac Index and the adjusted Big Mac Index. If appropriate, this index might be developed into an economic theory that can be applied to corporate finance, international trade, and international finance. To determine which Big Mac Index measure is a better indicator of exchange rate valuation, a comparison analysis was conducted. This study set out to determine how well the adjusted Big Mac Index performed as a gauge for exchange rate valuation. The research then compares the two Big Mac Index measures' ability to anticipate future exchange rates in order to determine which is more accurate. Data from the South African Reserve Bank and The Economist databases covering 37 nations from 2000 to 2022 were used for the analysis. Exchange rate misalignment trends were assessed globally, and the results indicated that the adjusted BMI was a more accurate measure of purchasing power. Tests of correlation revealed that there was a positive association between the real exchange rate and the Big Mac Index. Findings from a panel ARDL Model indicated that taking into consideration country-specific GDP variations and group heterogeneity can enhance the real exchange rates' ability to predict the raw BMI. The research also focused on the South African Rand to ascertain whether the Big Mac Index validates the Purchasing Power Parity theoretical framework. Using cointegration tests and graphic analysis, it was possible to find evidence for a cointegrating relationship between the real exchange rate and the Big Mac Index measures during the last 20 years. Additionally, a positive correlation between the modified Big Mac Index and terms of trade was discovered in the results, confirming the hypothesis that the Big Mac Index satisfies current account assumptions. Finally, a VEC model demonstrated that the modified BMI outperforms the raw BMI in terms of forecasting estimates. Overall, the study found that the Big Mac Index is more than a bit of fun as per its origin. The results showed that the adjusted Big Mac Index has practical applications and the potential to be considered as an economic theory. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2024
- Full Text:
- Date Issued: 2024-10-11
Carbonylation of cyclohexene with carbon dioxide (CO2) using transition metals as heterogeneous and homogeneous catalysts
- Authors: Sekaleli, Bafokeng Thabelo
- Date: 2024-10-11
- Subjects: Carbonylation , Carbon dioxide , Catalysts , Transition metals , Cyclohexene
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464565 , vital:76522
- Description: From a green chemistry perspective, carbon dioxide (CO2) emerges as an appealing C1 synthon, given its abundance in the atmosphere and cost-effectiveness. Many essential chemicals for daily life are derived from fossilized carbon sources like coal, petroleum, and natural gas. However, the by-product of these processes, CO2, poses environmental risks when excessively emitted as a greenhouse gas. Achieving a balance between carbon emissions and removal is crucial to address environmental concerns surrounding CO2. Utilizing CO2 as a C1 source in organic synthesis holds promise for mitigating this balance in the long term. Combining CO2 with other underutilized fine chemicals, such as alkanes, alkenes, and alkynes, to produce more valuable platform chemicals presents an economically viable strategy due to carbon dioxide’s abundance, low cost, and recyclability. Despite its simplicity, CO2's high thermodynamic stability and low kinetic reactivity, owing to its highly oxidized state, pose challenges to its use as a feedstock. Overcoming these hurdles requires catalysts to enhance CO2 reactivity. Our work focuses on developing and employing catalytic systems capable of activating CO2 as a C1 synthon in reactions with cyclohexene and a reducing agent to yield carboxylic acids or esters. In one approach, we have developed heterogeneous catalyst systems comprising transition metals (Au, Fe, Ni, Ru) supported on metal oxide (TiO2). Characterization techniques such as TEM, EDX, UV-Vis, BET, and XRD were used to study the properties of these materials. The catalysts were evaluated in a reaction involving cyclohexene, CO2, and H2O. In another approach, we explored the use of cyclo-tris(tetracarbonylruthenium) [Ru3(CO)12] as a homogeneous catalyst in a reaction involving cyclohexene, methanol, and CO2 in the presence of an ionic liquid, 1-Butyl-3-methylimidazolium chloride ([BMIM]+Cl-). 1H NMR and ATR-FT-IR were utilized to characterize [BMIM]+Cl-. The reaction product was characterised utilizing GC-MS. Upon seeing that Ru3(CO)12 changes color from orange to black when exposed to heat, an investigation was undertaken on the kind of transformations that the catalyst undergoes. This investigation was carried out with the hopes of finding the structures that could be resulting from Ru3(CO)12 during the reaction and their significance to it. The orange and black Ru complexes were characterized utilizing DSC, TGA, ATR-FT-IR and PXRD. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Sekaleli, Bafokeng Thabelo
- Date: 2024-10-11
- Subjects: Carbonylation , Carbon dioxide , Catalysts , Transition metals , Cyclohexene
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464565 , vital:76522
- Description: From a green chemistry perspective, carbon dioxide (CO2) emerges as an appealing C1 synthon, given its abundance in the atmosphere and cost-effectiveness. Many essential chemicals for daily life are derived from fossilized carbon sources like coal, petroleum, and natural gas. However, the by-product of these processes, CO2, poses environmental risks when excessively emitted as a greenhouse gas. Achieving a balance between carbon emissions and removal is crucial to address environmental concerns surrounding CO2. Utilizing CO2 as a C1 source in organic synthesis holds promise for mitigating this balance in the long term. Combining CO2 with other underutilized fine chemicals, such as alkanes, alkenes, and alkynes, to produce more valuable platform chemicals presents an economically viable strategy due to carbon dioxide’s abundance, low cost, and recyclability. Despite its simplicity, CO2's high thermodynamic stability and low kinetic reactivity, owing to its highly oxidized state, pose challenges to its use as a feedstock. Overcoming these hurdles requires catalysts to enhance CO2 reactivity. Our work focuses on developing and employing catalytic systems capable of activating CO2 as a C1 synthon in reactions with cyclohexene and a reducing agent to yield carboxylic acids or esters. In one approach, we have developed heterogeneous catalyst systems comprising transition metals (Au, Fe, Ni, Ru) supported on metal oxide (TiO2). Characterization techniques such as TEM, EDX, UV-Vis, BET, and XRD were used to study the properties of these materials. The catalysts were evaluated in a reaction involving cyclohexene, CO2, and H2O. In another approach, we explored the use of cyclo-tris(tetracarbonylruthenium) [Ru3(CO)12] as a homogeneous catalyst in a reaction involving cyclohexene, methanol, and CO2 in the presence of an ionic liquid, 1-Butyl-3-methylimidazolium chloride ([BMIM]+Cl-). 1H NMR and ATR-FT-IR were utilized to characterize [BMIM]+Cl-. The reaction product was characterised utilizing GC-MS. Upon seeing that Ru3(CO)12 changes color from orange to black when exposed to heat, an investigation was undertaken on the kind of transformations that the catalyst undergoes. This investigation was carried out with the hopes of finding the structures that could be resulting from Ru3(CO)12 during the reaction and their significance to it. The orange and black Ru complexes were characterized utilizing DSC, TGA, ATR-FT-IR and PXRD. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
- Full Text:
- Date Issued: 2024-10-11