An evaluation of the effectiveness of area-based conservation intervention in avoiding biodiversity loss in South Africa
- Authors: Van Straten, Maurice Oswald
- Date: 2023-04
- Subjects: Soil conservation -- South Africa , Livestock farms – South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61132 , vital:69765
- Description: Habitat degradation, livestock farming, crop cultivation, rangeland overutilization and veld mismanagement are among the factors causing biodiversity loss worldwide. Rangelands in arid and semi-arid environments are no exception, as they are under stress from conversion into cropland and pressure from livestock farming. In these arid areas, rainfall is unpredictable and plant recruitment levels low, resulting in veld rehabilitation being a potentially expensive and time-consuming undertaking for landowners. Landowners implement different rehabilitation methods to increase overall vegetation cover and prevent further soil and vegetation degradation. These rehabilitation methods may include the creation of micro-catchments, mulching, brushpacking, ripping, geotextiles, stone cobbling and erosion control fences, individually or in combination with the addition of reseeding, replanting, and use of manure or fertilizer to supplement land rehabilitation. This study investigated the significance of three rehabilitation methods (hollows, brush packing and a combination of these two methods) on water infiltration rates, soil moisture content, and vegetation canopy cover with associated growth form canopy cover over a period of 17 months (March 2021 to August 2022). This study showed that rehabilitation methods implemented had no significant impact on water infiltration rates and vegetation canopy cover. However, rehabilitation methods had a significant impact on soil moisture content. The use of a hollows is recommended when attempting to increase the soil moisture content percentage when performing rehabilitation. Overall vegetation canopy cover is influenced more by seasonal changes than by the rehabilitation methods implemented. This study indicated that the creation of micro-catchments is an effective rehabilitation method to use in an arid area, as it promotes vegetation establishment and growth. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management , 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Van Straten, Maurice Oswald
- Date: 2023-04
- Subjects: Soil conservation -- South Africa , Livestock farms – South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61132 , vital:69765
- Description: Habitat degradation, livestock farming, crop cultivation, rangeland overutilization and veld mismanagement are among the factors causing biodiversity loss worldwide. Rangelands in arid and semi-arid environments are no exception, as they are under stress from conversion into cropland and pressure from livestock farming. In these arid areas, rainfall is unpredictable and plant recruitment levels low, resulting in veld rehabilitation being a potentially expensive and time-consuming undertaking for landowners. Landowners implement different rehabilitation methods to increase overall vegetation cover and prevent further soil and vegetation degradation. These rehabilitation methods may include the creation of micro-catchments, mulching, brushpacking, ripping, geotextiles, stone cobbling and erosion control fences, individually or in combination with the addition of reseeding, replanting, and use of manure or fertilizer to supplement land rehabilitation. This study investigated the significance of three rehabilitation methods (hollows, brush packing and a combination of these two methods) on water infiltration rates, soil moisture content, and vegetation canopy cover with associated growth form canopy cover over a period of 17 months (March 2021 to August 2022). This study showed that rehabilitation methods implemented had no significant impact on water infiltration rates and vegetation canopy cover. However, rehabilitation methods had a significant impact on soil moisture content. The use of a hollows is recommended when attempting to increase the soil moisture content percentage when performing rehabilitation. Overall vegetation canopy cover is influenced more by seasonal changes than by the rehabilitation methods implemented. This study indicated that the creation of micro-catchments is an effective rehabilitation method to use in an arid area, as it promotes vegetation establishment and growth. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management , 2023
- Full Text:
- Date Issued: 2023-04
An investigation of alternative separation strategies for common chemical mixtures by means of host-guest chemistry protocols with host compounds N,N′- bis(5-phenyl-5-dibenzo[a,d]cycloheptenyl)ethylenediamine and N,N’-bis(5-phenyl-10,11- dihydro-5-dibenzo[a,d]cycloheptenyl)ethylenediamine
- Authors: Barton, Danica Brione
- Date: 2023-04
- Subjects: Ethylenediaminetetraacetic acid -- South Africa , Enzymes –Analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61176 , vital:69791
- Description: In this work, the selectivity behaviour of two host compounds, namely N,N’-bis(5-phenyl-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H1) and N,N’-bis(5-phenyl-10,11-dihydro-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H2), was assessed in mixtures of difficult-toseparate compounds, including the xylenes and ethylbenzene, pyridine and methylpyridines, and anisole and methylanisoles. These host compounds were synthesized using Grignard addition reactions with phenylmagnesium bromide on dibenzo[a,d]cyclohepten-5-one and 10,11- dihydrodibenzo[a,d]cyclohepten-5-one, respectively. The resultant alcohols were treated with perchloric acid to form the corresponding perchlorate salts, which were then reacted with ethylenediamine to afford the required H1 and H2 host compounds. Yields were 95 ad 52% for this final step in each case. An investigation of the conformations, both from experiment (using single crystal X-ray diffractometry (SCXRD) on the apohost compound) and computational calculations was undertaken. Unfortunately, H1 always crystallized out as a powder unless this host compound formed a complex with a guest species, and so could not be subjected to SCXRD analysis as apohost alone. However, a single crystal structure for apohost H2 was successfully obtained and compared with computational data from a previous investigation. It was observed that the conformation of apohost H2 compared favourably with that of the lowest energy conformer from that work. In single solvent recrystallization experiments with o-, m-, p-xylene (o-Xy, m-Xy, p-Xy) and ethylbenzene (EB), both H1 and H2 formed complexes with only one of the four guest species, namely p-Xy and o-Xy, respectively. The host:guest (H:G) ratios were 1:1 for both of these complexes. In the equimolar guest/guest competition experiments, inclusion complexes only formed when p-Xy or o-Xy, respectively, were present in the mixtures; if p-Xy (for experiments with H1) or o-Xy (H2) was absent from these mixtures, only apohost was recovered from the glass vessels. Three selectivity profiles were constructed for each of these host compounds, in which each one was recrystallized from binary mixed guests in various proportions. These demonstrated an overwhelming preference of H1 for p-Xy and H2 for o-Xy, which concurred with the results from the equimolar experiments. Thermal analysis using H1∙p-Xy revealed that this complex was unstable at ambient conditions, while SCXRD explained this observation: this complex may be defined as a true clathrate since no host‧‧‧guest interactions were identified at all, and the guest was retained in the complex by means of steric factors alone. Furthermore, the guest molecules resided in wide open channels that may have facilitated the guest release process. H2∙o-Xy, on the other hand, was stable at room temperature, and the guest release event only commenced at 69.7 °C (Ton). This too was explained by SCXRD analyses in that interactions between host and guest species were observed in this case. Additionally, the guest molecules were housed in discrete cages, which made their escape more challenging compared with p-Xy in H1∙p-Xy. It was concluded that, in this guest series, both of the host compounds would be effective as separatory tools employing host-guest chemistry protocols due to their remarkable selectivities for p-Xy (H1) and o-Xy (H2). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Barton, Danica Brione
- Date: 2023-04
- Subjects: Ethylenediaminetetraacetic acid -- South Africa , Enzymes –Analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61176 , vital:69791
- Description: In this work, the selectivity behaviour of two host compounds, namely N,N’-bis(5-phenyl-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H1) and N,N’-bis(5-phenyl-10,11-dihydro-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H2), was assessed in mixtures of difficult-toseparate compounds, including the xylenes and ethylbenzene, pyridine and methylpyridines, and anisole and methylanisoles. These host compounds were synthesized using Grignard addition reactions with phenylmagnesium bromide on dibenzo[a,d]cyclohepten-5-one and 10,11- dihydrodibenzo[a,d]cyclohepten-5-one, respectively. The resultant alcohols were treated with perchloric acid to form the corresponding perchlorate salts, which were then reacted with ethylenediamine to afford the required H1 and H2 host compounds. Yields were 95 ad 52% for this final step in each case. An investigation of the conformations, both from experiment (using single crystal X-ray diffractometry (SCXRD) on the apohost compound) and computational calculations was undertaken. Unfortunately, H1 always crystallized out as a powder unless this host compound formed a complex with a guest species, and so could not be subjected to SCXRD analysis as apohost alone. However, a single crystal structure for apohost H2 was successfully obtained and compared with computational data from a previous investigation. It was observed that the conformation of apohost H2 compared favourably with that of the lowest energy conformer from that work. In single solvent recrystallization experiments with o-, m-, p-xylene (o-Xy, m-Xy, p-Xy) and ethylbenzene (EB), both H1 and H2 formed complexes with only one of the four guest species, namely p-Xy and o-Xy, respectively. The host:guest (H:G) ratios were 1:1 for both of these complexes. In the equimolar guest/guest competition experiments, inclusion complexes only formed when p-Xy or o-Xy, respectively, were present in the mixtures; if p-Xy (for experiments with H1) or o-Xy (H2) was absent from these mixtures, only apohost was recovered from the glass vessels. Three selectivity profiles were constructed for each of these host compounds, in which each one was recrystallized from binary mixed guests in various proportions. These demonstrated an overwhelming preference of H1 for p-Xy and H2 for o-Xy, which concurred with the results from the equimolar experiments. Thermal analysis using H1∙p-Xy revealed that this complex was unstable at ambient conditions, while SCXRD explained this observation: this complex may be defined as a true clathrate since no host‧‧‧guest interactions were identified at all, and the guest was retained in the complex by means of steric factors alone. Furthermore, the guest molecules resided in wide open channels that may have facilitated the guest release process. H2∙o-Xy, on the other hand, was stable at room temperature, and the guest release event only commenced at 69.7 °C (Ton). This too was explained by SCXRD analyses in that interactions between host and guest species were observed in this case. Additionally, the guest molecules were housed in discrete cages, which made their escape more challenging compared with p-Xy in H1∙p-Xy. It was concluded that, in this guest series, both of the host compounds would be effective as separatory tools employing host-guest chemistry protocols due to their remarkable selectivities for p-Xy (H1) and o-Xy (H2). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Assessing diatom community composition and structure in palaeosediments of a southern Cape coastal wetland
- Authors: Sepato, Tshiamo Tsholofelo
- Date: 2023-04
- Subjects: Diatoms --South Africa – Southern Cape , Paleoecology , Marine algae --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61258 , vital:69847
- Description: Palaeoenvironmental studies are important as they aid in reconstructing histories of past landscapes and provide key long-term information for the conservation and management of ecosystems. The southern Cape coast is a focus area for palaeoenvironmental research due to its high botanical and climatic importance. A three-metre sediment core was retrieved from Whale Rock wetland (Plettenberg Bay, southern Cape Coast) and spanned ~8000 years – a large proportion of the Holocene epoch. Diatom data preserved in palaeosediments of the Whale Rock wetland are presented within this study. A total of 48 diatom species was identified. Based on the multivariate statistical analysis, the diatom assemblages were divided into three zones: Zone WR-1-A (~7200 – 6450 cal yr BP); Zone WR-1- B (~6450 – 6250 cal yr BP) and Zone WR-1-C (~250 cal yr BP – to present). Two diatom preservation hiatus periods were observed at ~8000 – 7200 cal yr BP and ~6400 – 230 cal yr BP. The results indicated that benthic diatom species were significantly dominant throughout the Whale Rock record. The diatom evidence revealed that the Whale Rock wetland system freshened over time as diatom species identified in Zone WR-1-A and Zone WR-1- B indicated marine influences whereas Zone WR-1-C displayed a dominance of species that thrive in freshwater conditions. A transitional phase occurred at ~6400 cal yr BP where abrupt changes began prior to the significant ~6400 – 230 cal yr BP diatom preservation hiatus period. Principal Component Analysis showed that salinity was the main environmental driver of change impacting the species abundance and diversity of diatom communities within the wetland system throughout the Holocene. When compared with regional palaeoenvironmental and palaeolimnological data, it is evident that several other wetland systems moved from a marine/brackish favoured system to a freshwater system with the transitional phase occurring at different periods within the Holocene. This study indicated that diatoms are powerful biological proxies of environmental change. It is recommended that the site be revisited to investigate further the hiatus phases to further explore the lack of diatom preservation for these periods and to also contribute more palaeoenvironmental proxy evidence as well as modern hydrological information. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2023-04
- Authors: Sepato, Tshiamo Tsholofelo
- Date: 2023-04
- Subjects: Diatoms --South Africa – Southern Cape , Paleoecology , Marine algae --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61258 , vital:69847
- Description: Palaeoenvironmental studies are important as they aid in reconstructing histories of past landscapes and provide key long-term information for the conservation and management of ecosystems. The southern Cape coast is a focus area for palaeoenvironmental research due to its high botanical and climatic importance. A three-metre sediment core was retrieved from Whale Rock wetland (Plettenberg Bay, southern Cape Coast) and spanned ~8000 years – a large proportion of the Holocene epoch. Diatom data preserved in palaeosediments of the Whale Rock wetland are presented within this study. A total of 48 diatom species was identified. Based on the multivariate statistical analysis, the diatom assemblages were divided into three zones: Zone WR-1-A (~7200 – 6450 cal yr BP); Zone WR-1- B (~6450 – 6250 cal yr BP) and Zone WR-1-C (~250 cal yr BP – to present). Two diatom preservation hiatus periods were observed at ~8000 – 7200 cal yr BP and ~6400 – 230 cal yr BP. The results indicated that benthic diatom species were significantly dominant throughout the Whale Rock record. The diatom evidence revealed that the Whale Rock wetland system freshened over time as diatom species identified in Zone WR-1-A and Zone WR-1- B indicated marine influences whereas Zone WR-1-C displayed a dominance of species that thrive in freshwater conditions. A transitional phase occurred at ~6400 cal yr BP where abrupt changes began prior to the significant ~6400 – 230 cal yr BP diatom preservation hiatus period. Principal Component Analysis showed that salinity was the main environmental driver of change impacting the species abundance and diversity of diatom communities within the wetland system throughout the Holocene. When compared with regional palaeoenvironmental and palaeolimnological data, it is evident that several other wetland systems moved from a marine/brackish favoured system to a freshwater system with the transitional phase occurring at different periods within the Holocene. This study indicated that diatoms are powerful biological proxies of environmental change. It is recommended that the site be revisited to investigate further the hiatus phases to further explore the lack of diatom preservation for these periods and to also contribute more palaeoenvironmental proxy evidence as well as modern hydrological information. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2023-04
Assessing the Role of Women on Small-Scale Agribusiness at Wincanton Estate in Kariega, South Africa
- Authors: Zalwango, Joanita
- Date: 2023-04
- Subjects: Leadership in women , Women in agriculture --Eastern Cape – Kariega , Climate change -- Kariega
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61054 , vital:69690
- Description: Agricultural development is a prerequisite for most economies to grow. Agricultural activities are key to food security and sustaining livelihoods globally. Within the African continent, more women are employed in agriculture and agribusiness activities than other sectors. As main contributors to the labour force in the agricultural sector, women get involved in many agricultural and agribusiness activities to sustain their families. With over 60% of women in Sub–Saharan Africa involved in agriculture, there is need to explore and assess the role they play in promoting agribusiness with special focus on Kariega, in South Africa. The identified participants in the study, as self-employed farmers, participate in agribusiness, thereby creating employment opportunities whilst generating personal incomes. Several benefits to female involvement in agribusiness were identified, including the ability to sustain families, stable cash flow, and empowerment. Several challenges were identified, including adequate capital, inaccessibility to private land, droughts, water scarcity, climate change effects and stigmatisation. Through a feminist qualitative methodology, the study utilised semi- structured interviews to collect data from 10 women involved in agribusiness around Kariega, Nelson Mandela Bay. Themes from the findings are analysed to highlight the important role played by women toward agribusiness, their achievements, government and private sector role and the hinderances still faced by these women in agricultural cooperatives. Discussion from the analysis included a framework of recommendations, for policy makers, development practitioners and future researchers. The study found that all stakeholders involved in the agricultural sector should work together for sustainable agricultural development and sustainable development goals to be achieved. Sustainability among women farmers can be achieved by (a) Increasing government intervention and support (b) Climate smart agriculture practices (c) Overcoming stigmatisation (d) Encouraging and involving the youth (e) Diversification and integration of farm businesses and (f) Using contract farming. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text: false
- Date Issued: 2023-04
Assessing the Role of Women on Small-Scale Agribusiness at Wincanton Estate in Kariega, South Africa
- Authors: Zalwango, Joanita
- Date: 2023-04
- Subjects: Leadership in women , Women in agriculture --Eastern Cape – Kariega , Climate change -- Kariega
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61054 , vital:69690
- Description: Agricultural development is a prerequisite for most economies to grow. Agricultural activities are key to food security and sustaining livelihoods globally. Within the African continent, more women are employed in agriculture and agribusiness activities than other sectors. As main contributors to the labour force in the agricultural sector, women get involved in many agricultural and agribusiness activities to sustain their families. With over 60% of women in Sub–Saharan Africa involved in agriculture, there is need to explore and assess the role they play in promoting agribusiness with special focus on Kariega, in South Africa. The identified participants in the study, as self-employed farmers, participate in agribusiness, thereby creating employment opportunities whilst generating personal incomes. Several benefits to female involvement in agribusiness were identified, including the ability to sustain families, stable cash flow, and empowerment. Several challenges were identified, including adequate capital, inaccessibility to private land, droughts, water scarcity, climate change effects and stigmatisation. Through a feminist qualitative methodology, the study utilised semi- structured interviews to collect data from 10 women involved in agribusiness around Kariega, Nelson Mandela Bay. Themes from the findings are analysed to highlight the important role played by women toward agribusiness, their achievements, government and private sector role and the hinderances still faced by these women in agricultural cooperatives. Discussion from the analysis included a framework of recommendations, for policy makers, development practitioners and future researchers. The study found that all stakeholders involved in the agricultural sector should work together for sustainable agricultural development and sustainable development goals to be achieved. Sustainability among women farmers can be achieved by (a) Increasing government intervention and support (b) Climate smart agriculture practices (c) Overcoming stigmatisation (d) Encouraging and involving the youth (e) Diversification and integration of farm businesses and (f) Using contract farming. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text: false
- Date Issued: 2023-04
Continuous flow synthesis of a key intermediate towards the antidiabetic drug repaglinide
- Authors: Williams, Arushan
- Date: 2023-04
- Subjects: Diabetes -- Miscellanea -- South Africa , Diabetes –Treatment
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61064 , vital:69715
- Description: Across the world, diabetes is one of the leading causes of deaths attributed to noncommunicable diseases (NCDs). In Africa, a huge proportion of African countries’ annual healthcare budgets are consumed by diabetes (7 %) with many already experiencing healthcare budget deficits. The prevalence of diabetes is rapidly growing and threatens the economic productivity and livelihood of many families within the region. The world leaders have invested heavily in reducing the pandemic by focusing on increasing the availability of affordable essential medicines in developing countries. The majority of diabetes cases are due to type 2 diabetes (90 %) and may be treated using oral hypoglycaemic drugs (OHDs). Repaglinide (REP) is a non-sulfonylurea insulin secretagogue (meglitinide) with greater HbA1c reduction than metformin in newly onset type 2 diabetic patients, however due to the high price of REP outside Asia, cheaper and less effective OHDs are prescribed to patients. Many of the reported synthetic routes towards REP utilize a key intermediate, 2-(3-ethoxy-4- iethoxycarbonyl)phenyl)acetic acid. The key intermediate contributes significantly to the price of REP as many of the intermediate’s synthetic routes suffer from long reaction times, low yields and industrial complex approaches. Therefore, this has prompted us to investigate an efficient process towards the synthesis of 2-(3-ethoxy-4-(ethoxycarbonyl)phenyl)acetic acid using multiple continuous flow systems. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Williams, Arushan
- Date: 2023-04
- Subjects: Diabetes -- Miscellanea -- South Africa , Diabetes –Treatment
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61064 , vital:69715
- Description: Across the world, diabetes is one of the leading causes of deaths attributed to noncommunicable diseases (NCDs). In Africa, a huge proportion of African countries’ annual healthcare budgets are consumed by diabetes (7 %) with many already experiencing healthcare budget deficits. The prevalence of diabetes is rapidly growing and threatens the economic productivity and livelihood of many families within the region. The world leaders have invested heavily in reducing the pandemic by focusing on increasing the availability of affordable essential medicines in developing countries. The majority of diabetes cases are due to type 2 diabetes (90 %) and may be treated using oral hypoglycaemic drugs (OHDs). Repaglinide (REP) is a non-sulfonylurea insulin secretagogue (meglitinide) with greater HbA1c reduction than metformin in newly onset type 2 diabetic patients, however due to the high price of REP outside Asia, cheaper and less effective OHDs are prescribed to patients. Many of the reported synthetic routes towards REP utilize a key intermediate, 2-(3-ethoxy-4- iethoxycarbonyl)phenyl)acetic acid. The key intermediate contributes significantly to the price of REP as many of the intermediate’s synthetic routes suffer from long reaction times, low yields and industrial complex approaches. Therefore, this has prompted us to investigate an efficient process towards the synthesis of 2-(3-ethoxy-4-(ethoxycarbonyl)phenyl)acetic acid using multiple continuous flow systems. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Costs and consequences at the population-environment-development interface in St Francis Bay: exploring the linkages of a complex system
- Authors: Pringle, Geena
- Date: 2023-04
- Subjects: Population -- Environmental aspects , Population --Statistics , Loliginidae -- South Africa -- st francis bay
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61294 , vital:70065
- Description: Coastal zones the world over are particularly attractive for the development of human settlements. Naturally, this trend frequently results in human induced disturbances of sensitive ecosystems, often resulting in dramatic and unintended consequences. The South African coastline is no stranger to this phenomenon. Dynamics at the population-environment-development interface in the coastal zone often presents affected communities and institutions with complex challenges. An infamous case along the South African coastline is the settlement of St Francis Bay, the focus of this dissertation. St Francis Bay was established as a holiday village around sixty years ago and its economy is today firmly dependent on the fragile bond and reciprocal relationship between the tourist trade and the integrity of sandy beaches. The dissertation, against this background and drawing from complex systems theory, explores the links between human activity and the biophysical environment and the ominous costs and consequences that are produced at the local population-environment-development interface. Domains that are considered within the nexus of relevant aspects include the wind-driven sediment bypass system across the local headland; climate change; the local economy; social wellbeing, inequality and social justice; as well urban planning and political governance. The desktop study applied to St Francis Bay made use of Geographic Information Systems and statistical information to form the basis of the methodological approach in this dissertation. The Population-Environment-Development nexus was formed as a result. The results illustrate how critical levels of beach erosion are connected amidst an intricate reciprocal nexus to these and other aspects. It demonstrates that the sustainability of the settlement hinges on the understanding of such linkages and underscores the relevance of the methodological approach that is applied. The sustainability of the environment and the resulting impact on the quality of life of the human population remains a challenge for future generations as well as governance systems. By acknowledging and understanding the complexity that exists in coastal zones allows for future research on the topic to be explored and enable key role players to proactively intervene to benefit the population and the environment. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Pringle, Geena
- Date: 2023-04
- Subjects: Population -- Environmental aspects , Population --Statistics , Loliginidae -- South Africa -- st francis bay
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61294 , vital:70065
- Description: Coastal zones the world over are particularly attractive for the development of human settlements. Naturally, this trend frequently results in human induced disturbances of sensitive ecosystems, often resulting in dramatic and unintended consequences. The South African coastline is no stranger to this phenomenon. Dynamics at the population-environment-development interface in the coastal zone often presents affected communities and institutions with complex challenges. An infamous case along the South African coastline is the settlement of St Francis Bay, the focus of this dissertation. St Francis Bay was established as a holiday village around sixty years ago and its economy is today firmly dependent on the fragile bond and reciprocal relationship between the tourist trade and the integrity of sandy beaches. The dissertation, against this background and drawing from complex systems theory, explores the links between human activity and the biophysical environment and the ominous costs and consequences that are produced at the local population-environment-development interface. Domains that are considered within the nexus of relevant aspects include the wind-driven sediment bypass system across the local headland; climate change; the local economy; social wellbeing, inequality and social justice; as well urban planning and political governance. The desktop study applied to St Francis Bay made use of Geographic Information Systems and statistical information to form the basis of the methodological approach in this dissertation. The Population-Environment-Development nexus was formed as a result. The results illustrate how critical levels of beach erosion are connected amidst an intricate reciprocal nexus to these and other aspects. It demonstrates that the sustainability of the settlement hinges on the understanding of such linkages and underscores the relevance of the methodological approach that is applied. The sustainability of the environment and the resulting impact on the quality of life of the human population remains a challenge for future generations as well as governance systems. By acknowledging and understanding the complexity that exists in coastal zones allows for future research on the topic to be explored and enable key role players to proactively intervene to benefit the population and the environment. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Distinguishing elephant induced thicket degradation and climate related factors in Addo Elephant National Park, Eastern Cape, South Africa
- Authors: Mapheto, Tlhologelo James
- Date: 2023-04
- Subjects: Elephant – Behaviour -- South Africa -- Addo Elephant National Park , Wildlife conservation -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60753 , vital:66741
- Description: The Addo Elephant National Park (AENP) is an ecologically sensitive environment where the increase in elephant population, especially in a changing climate is a recipe for landscape degradation and biodiversity loss. The Park is situated in the drought prone Eastern Cape Province, however, the effects of drought on thicket vegetation is less understood. This study aimed to distinguish elephant-induced thicket degradation from the effects of climatic factors, using remote sensing, GIS, and statistical techniques. To characterise and map vegetation conditions of the reserve temporal series Landsat imagery (n = 22) from 1998 to 2018 were analysed. Vegetation states were determined using Normalised Difference Vegetation Index (NDVI) derived from the growing season of the study period. Using supervised per-pixel image classification technique, the NDVI values characterized into distinct land cover classes viz (1) Intact Thicket, (2) Transformed Thicket, (3) Degraded Thicket, (4) Bare Ground and (6) Water Bodies. Post-classification change detection and landscape fragmentation analysis was performed. Climatic data were obtained from existing weather stations and raster surface of accumulated rainfall and mean maximum temperature were developed using the Inverse Distance Weighting (IDW). Time series analysis was implemented on the NDVI and climatic condition data by plotting annual measures to indicate variable trends. Temporal trend analysis was performed on the NDVI data using the nonparametric Mann-Kendall trend analysis test to indicate thicket vegetation condition improvement and general degradation. The Residual Trend (RESTREND) approach was employed to remove the effect of rainfall on vegetation productivity. This involved using the Ordinary Least Square regression functionality in ArcMap to compute the relationship between ∑NDVI and accumulated rainfall for every pixel for the study period. The products of the regression were assessed using Pearson’s Correlation (r) at a significance level of 90% (p-value ≤ 0.1) to distinguish strong relationships. Overlay analysis was performed, using the NDVI trend slope and the correlation coefficient (r) raster surfaces, to model vegetation dynamics influenced by elephant activities. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Mapheto, Tlhologelo James
- Date: 2023-04
- Subjects: Elephant – Behaviour -- South Africa -- Addo Elephant National Park , Wildlife conservation -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60753 , vital:66741
- Description: The Addo Elephant National Park (AENP) is an ecologically sensitive environment where the increase in elephant population, especially in a changing climate is a recipe for landscape degradation and biodiversity loss. The Park is situated in the drought prone Eastern Cape Province, however, the effects of drought on thicket vegetation is less understood. This study aimed to distinguish elephant-induced thicket degradation from the effects of climatic factors, using remote sensing, GIS, and statistical techniques. To characterise and map vegetation conditions of the reserve temporal series Landsat imagery (n = 22) from 1998 to 2018 were analysed. Vegetation states were determined using Normalised Difference Vegetation Index (NDVI) derived from the growing season of the study period. Using supervised per-pixel image classification technique, the NDVI values characterized into distinct land cover classes viz (1) Intact Thicket, (2) Transformed Thicket, (3) Degraded Thicket, (4) Bare Ground and (6) Water Bodies. Post-classification change detection and landscape fragmentation analysis was performed. Climatic data were obtained from existing weather stations and raster surface of accumulated rainfall and mean maximum temperature were developed using the Inverse Distance Weighting (IDW). Time series analysis was implemented on the NDVI and climatic condition data by plotting annual measures to indicate variable trends. Temporal trend analysis was performed on the NDVI data using the nonparametric Mann-Kendall trend analysis test to indicate thicket vegetation condition improvement and general degradation. The Residual Trend (RESTREND) approach was employed to remove the effect of rainfall on vegetation productivity. This involved using the Ordinary Least Square regression functionality in ArcMap to compute the relationship between ∑NDVI and accumulated rainfall for every pixel for the study period. The products of the regression were assessed using Pearson’s Correlation (r) at a significance level of 90% (p-value ≤ 0.1) to distinguish strong relationships. Overlay analysis was performed, using the NDVI trend slope and the correlation coefficient (r) raster surfaces, to model vegetation dynamics influenced by elephant activities. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Effect of livestock management and services to ecosystems on rangeland health and resilience in the NamaKaroo
- Authors: Boshoff, Mishak
- Date: 2023-04
- Subjects: Livestock – Management --South Africa—Karoo , Range ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60611 , vital:66017
- Description: Rangelands offer great opportunities for mutualisms between nature conservation and economic productivity if positive feedback loops can be identified and described. The effects of different livestock management practices are controversial. This research examined the effect of different grazing intensities on soil health using springtails (Collembola) and ants (Formicidae) as bioindicators, combined with soil and vegetation variables. The relationship between rangeland managers and rangeland ecosystems, particularly with regard to feedback loops between land care and economic production, was also investigated. Bioindicator samples were collected at different treatments of livestock grazing intensity and a questionnaire was submitted to 65 rangeland managers in the semi-arid Nama-Karoo biome of South Africa. In most cases we found no significant relationship between grazing intensity and Collembola and ant community composition, vegetation variables, and soil variables. The few significant relationships we found were contradictory in their implications for the effect of high intensity grazing on soil health. The results suggested that differences in livestock management are relatively unimportant for soil health, at least in semi-arid systems under conditions immediately following a drought. The questionnaire yielded results on outline of management practices, basis of management decisions, consequences of monitoring veld to inform management decisions, and indicators of successful management. Respondents characterized by higher ecological fluency focused on livestock production when making management decisions, stocked at higher densities, and monitored the rangeland ecosystem to inform their decisions. For monitoring the ecosystem, they used bioindicators such as diversity of biota, successional stage, and ecologically important functional groups. We concluded that the development of ecological knowledge in rangeland managers enables the establishment of feedback loops between ecosystem services and services to ecosystems, which are desirable for economic productivity and nature conservation. Development of relevant ecological knowledge and management techniques should be based on forums and dialogue among rangeland managers, developing distributed cognition and resilience in the community of rangeland managers. , Thesis (MSc) -- Faculty of Science, School Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Boshoff, Mishak
- Date: 2023-04
- Subjects: Livestock – Management --South Africa—Karoo , Range ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60611 , vital:66017
- Description: Rangelands offer great opportunities for mutualisms between nature conservation and economic productivity if positive feedback loops can be identified and described. The effects of different livestock management practices are controversial. This research examined the effect of different grazing intensities on soil health using springtails (Collembola) and ants (Formicidae) as bioindicators, combined with soil and vegetation variables. The relationship between rangeland managers and rangeland ecosystems, particularly with regard to feedback loops between land care and economic production, was also investigated. Bioindicator samples were collected at different treatments of livestock grazing intensity and a questionnaire was submitted to 65 rangeland managers in the semi-arid Nama-Karoo biome of South Africa. In most cases we found no significant relationship between grazing intensity and Collembola and ant community composition, vegetation variables, and soil variables. The few significant relationships we found were contradictory in their implications for the effect of high intensity grazing on soil health. The results suggested that differences in livestock management are relatively unimportant for soil health, at least in semi-arid systems under conditions immediately following a drought. The questionnaire yielded results on outline of management practices, basis of management decisions, consequences of monitoring veld to inform management decisions, and indicators of successful management. Respondents characterized by higher ecological fluency focused on livestock production when making management decisions, stocked at higher densities, and monitored the rangeland ecosystem to inform their decisions. For monitoring the ecosystem, they used bioindicators such as diversity of biota, successional stage, and ecologically important functional groups. We concluded that the development of ecological knowledge in rangeland managers enables the establishment of feedback loops between ecosystem services and services to ecosystems, which are desirable for economic productivity and nature conservation. Development of relevant ecological knowledge and management techniques should be based on forums and dialogue among rangeland managers, developing distributed cognition and resilience in the community of rangeland managers. , Thesis (MSc) -- Faculty of Science, School Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
Factors affecting pinniped skull morphology
- Authors: Penaluna, Julia Elizabeth
- Date: 2023-04
- Subjects: hybridisation -- South Africa , Sexual dimorphism (Animals) , Craniology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61306 , vital:70077
- Description: Morphologies have evolved due to trade-offs between competing selective pressures. This is especially true for the skull. Not only does it contain the brain and the organs that are responsible for sensory function, but it is also contains components that play important roles in feeding, breathing, balance, defence, aggression and communication. The pinnipeds, a group of species that has evolved from terrestrial origins and became adapted to the marine environment, are under numerous selective pressures within the marine environment. These species have had to evolve in order to capture and process food underwater, and to dive. In addition, they are also characterised by substantial sexual size dimorphism in some species. Pinnipeds also make use of numerous marine and haul-out habitats with varying characteristics and complexity. Hybridisation has been recorded among pinnipeds, resulting in the production of hybrid offspring with characteristics that are different to their parent species. The aim of the study was to investigate the effect of these life history characteristics on skull and mandible morphology of pinniped species using three dimensional geometric morphometrics. To achieve this, 43 skull and 15 mandible 3D landmarks were collected using a Microscribe G2X digitizer with 0.2mm accuracy, on the skull and mandibles of 17 species of pinnipeds across three families, and one hybrid species. In total, 96 specimens across these species were examined. Data on the different life history characteristics of each species were collected from the literature. These data were plotted onto the PCA results in order to create and visually compare minimum convex polygons for each life history category. The results found that phylogeny, feeding strategy and sexual dimorphism were the most important factors in explaining differences in pinniped skull and mandible shape and size. may have resulted in these changes. Similarly, the inclusion of more species, covering a broader range of life histories may be beneficial. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Penaluna, Julia Elizabeth
- Date: 2023-04
- Subjects: hybridisation -- South Africa , Sexual dimorphism (Animals) , Craniology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61306 , vital:70077
- Description: Morphologies have evolved due to trade-offs between competing selective pressures. This is especially true for the skull. Not only does it contain the brain and the organs that are responsible for sensory function, but it is also contains components that play important roles in feeding, breathing, balance, defence, aggression and communication. The pinnipeds, a group of species that has evolved from terrestrial origins and became adapted to the marine environment, are under numerous selective pressures within the marine environment. These species have had to evolve in order to capture and process food underwater, and to dive. In addition, they are also characterised by substantial sexual size dimorphism in some species. Pinnipeds also make use of numerous marine and haul-out habitats with varying characteristics and complexity. Hybridisation has been recorded among pinnipeds, resulting in the production of hybrid offspring with characteristics that are different to their parent species. The aim of the study was to investigate the effect of these life history characteristics on skull and mandible morphology of pinniped species using three dimensional geometric morphometrics. To achieve this, 43 skull and 15 mandible 3D landmarks were collected using a Microscribe G2X digitizer with 0.2mm accuracy, on the skull and mandibles of 17 species of pinnipeds across three families, and one hybrid species. In total, 96 specimens across these species were examined. Data on the different life history characteristics of each species were collected from the literature. These data were plotted onto the PCA results in order to create and visually compare minimum convex polygons for each life history category. The results found that phylogeny, feeding strategy and sexual dimorphism were the most important factors in explaining differences in pinniped skull and mandible shape and size. may have resulted in these changes. Similarly, the inclusion of more species, covering a broader range of life histories may be beneficial. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Interactive visualisation of electricity usage in smart environments
- Ngwenya, Moreblessing Tafadzwa
- Authors: Ngwenya, Moreblessing Tafadzwa
- Date: 2023-04
- Subjects: Smart environment -- south Africa , Application software -- Development , Intelligent buildings
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61477 , vital:70687
- Description: Saving electricity is a trending topic due to the electricity challenges that are being faced globally. Smart environments are environments that are equipped with physical objects, which include computers, sensors, actuators, smartphones, and wearable devices interconnected together through the Internet of Things. The Internet of Things provides a network to achieve communication, and computation abilities to provide individuals with smart services anytime, and anywhere. Rapid developments in information technology have increased the number of smart appliances being used, leading to increased electricity usage. Devices and appliances in Smart Environments continue to consume electricity even when not in use, because of the standby function. The problems arise as the electricity consumption of the standby function accumulates to large amounts. Effective communication through visualisation of the electricity consumption in a Smart Environment provides a viable solution to reducing the consumption of electricity. This research aimed to design and developed a visualisation system that successfully communicates electricity consumption to the user using a variety of visualisation techniques. The Design Science Research Methodology was used to address the research questions and was used to iteratively design and develop an energy usage visualisation system. The visualisation system was created for the Smart Lab at the Nelson Mandela University's Department of Computing Sciences. A usability study was conducted to assess the usability and efficacy of the system. The system was found to be usable and effective in communicating power usage to potential customers, since the participants were able to complete the tasks in a short amount of time. The positive results show that visualisation can aid in communicating electricity usage to customers, resulting in a possible reduction in electricity consumption and improved decision-making. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Ngwenya, Moreblessing Tafadzwa
- Date: 2023-04
- Subjects: Smart environment -- south Africa , Application software -- Development , Intelligent buildings
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61477 , vital:70687
- Description: Saving electricity is a trending topic due to the electricity challenges that are being faced globally. Smart environments are environments that are equipped with physical objects, which include computers, sensors, actuators, smartphones, and wearable devices interconnected together through the Internet of Things. The Internet of Things provides a network to achieve communication, and computation abilities to provide individuals with smart services anytime, and anywhere. Rapid developments in information technology have increased the number of smart appliances being used, leading to increased electricity usage. Devices and appliances in Smart Environments continue to consume electricity even when not in use, because of the standby function. The problems arise as the electricity consumption of the standby function accumulates to large amounts. Effective communication through visualisation of the electricity consumption in a Smart Environment provides a viable solution to reducing the consumption of electricity. This research aimed to design and developed a visualisation system that successfully communicates electricity consumption to the user using a variety of visualisation techniques. The Design Science Research Methodology was used to address the research questions and was used to iteratively design and develop an energy usage visualisation system. The visualisation system was created for the Smart Lab at the Nelson Mandela University's Department of Computing Sciences. A usability study was conducted to assess the usability and efficacy of the system. The system was found to be usable and effective in communicating power usage to potential customers, since the participants were able to complete the tasks in a short amount of time. The positive results show that visualisation can aid in communicating electricity usage to customers, resulting in a possible reduction in electricity consumption and improved decision-making. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2023
- Full Text:
- Date Issued: 2023-04
Investigating the role of UAVs and convolutional neural networks in the identification of invasive plant species in the Albany Thicket
- Authors: Wesson, Frank Cameron
- Date: 2023-04
- Subjects: Drone aircraft -- Control systems , Drone -- South Africa , Albany Thicket -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61097 , vital:69755
- Description: The study aimed to determine whether plant species could be classified by using high resolution aerial imagery and a convolutional neural network (CNN). The full capabilities of a CNN were examined including testing whether the platform could be used for land cover and the evaluation of land change over time. A drone or unmanned aerial vehicle (UAV) was used to collect the aerial data of the study area, and 45 subplots were used for the image analysis. The CNN was coded and operated in RStudio, and digitised data from the input imagery were used as training and validation data by the programme to learn features. Four classifications were performed using various quantities of input data to access the performance of the neural network. In addition, tests were performed to understand whether the CNN could be used as a land cover and land change detection tool. Accuracy assessments were done on the results to test reliability and accuracy. The best-performing classification achieved an average user and producer accuracy of above 90%, while the overall accuracy was 93%, and the kappa coefficient score was 0.86. The CNN was also able to predict the land coverage area of Opuntia to be within 4% of the ground truthing data area. A change in land cover over time was detected by the programme after the manual clearing of the invasive plant had been undertaken. This research has determined that the use of a CNN in remote sensing is a very powerful tool for supervised image classifications and that it can be used for monitoring land cover by accurately estimating the spatial distribution of plant species and by monitoring the species' growth or decline over time. A CNN could also be used as a tool for landowners to prove that they are making efforts to clear invasive species from their land. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Wesson, Frank Cameron
- Date: 2023-04
- Subjects: Drone aircraft -- Control systems , Drone -- South Africa , Albany Thicket -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61097 , vital:69755
- Description: The study aimed to determine whether plant species could be classified by using high resolution aerial imagery and a convolutional neural network (CNN). The full capabilities of a CNN were examined including testing whether the platform could be used for land cover and the evaluation of land change over time. A drone or unmanned aerial vehicle (UAV) was used to collect the aerial data of the study area, and 45 subplots were used for the image analysis. The CNN was coded and operated in RStudio, and digitised data from the input imagery were used as training and validation data by the programme to learn features. Four classifications were performed using various quantities of input data to access the performance of the neural network. In addition, tests were performed to understand whether the CNN could be used as a land cover and land change detection tool. Accuracy assessments were done on the results to test reliability and accuracy. The best-performing classification achieved an average user and producer accuracy of above 90%, while the overall accuracy was 93%, and the kappa coefficient score was 0.86. The CNN was also able to predict the land coverage area of Opuntia to be within 4% of the ground truthing data area. A change in land cover over time was detected by the programme after the manual clearing of the invasive plant had been undertaken. This research has determined that the use of a CNN in remote sensing is a very powerful tool for supervised image classifications and that it can be used for monitoring land cover by accurately estimating the spatial distribution of plant species and by monitoring the species' growth or decline over time. A CNN could also be used as a tool for landowners to prove that they are making efforts to clear invasive species from their land. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Investigating thermoregulatory responses of rhabdomys pumilio at high wet-bulb temperatures
- Authors: Hartley, Oliver
- Date: 2023-04
- Subjects: Heat stress physiology , Small mammal thermoregulation -- South Africa , Climate change - Wet-bulb temperature
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60873 , vital:68916
- Description: As the Anthropocene continues to be characterised by ever rising temperature highs, increasingly sporadic and extreme climatic events, and their accompanying mass mortality events, climate scientists now warn that the continued climate destabilisation may for the first time in recorded history prevent terrestrial homeothermic endotherms from being able to thermoregulate. Having evolved to maintain body temperatures (Tbs) well above their ambient (Ta) conditions, these endotherms have evolved a suite of adaptations to a colder environment to allow for homeothermic thermoregulation to occur. However, by the same vein, having evolved in a colder climate to stay warm also has led to a reduced capacity to prevent heat stress when temperature conditions are elevated. In absence of behavioural counter measures, the only physiological means available to thermoregulation to prevent such heat stress is that of evaporative water loss (EWL). If still inefficient, the endotherm will risk becoming hyperthermic. Literature has established that excessive heat exposure or reduced evaporative cooling capacities strain or retard thermoregulatory processes. If an endotherm experiences severe heat exposure, the rate at which passive heating is experienced will increase. Should an endotherm be in a humid environment, evaporative cooling efficiency is reduced. As a result, these two abiotic factors are therefore known to contribute towards heat storage, and therefore thermal stress. However, should both factors occur in the same environment, the heat stress effects are compounded, creating an environment dangerous for thermoregulating endotherms. For this reason, authors have emphasised that future wet-bulb (Tw) conditions may pose a penultimate threat to thermoregulating endotherms. Being a measure of coldest temperature attainable as a result of evaporative cooling, Tw has been proposed to represent a lower temperature thermal limit to endothermic thermoregulation. Once reaching a 2°C differential below an endotherms Tb (Tb – Tw = 2˚C), Tw is believed to impede the evaporative cooling process and, consequentially, commit endotherms to becoming hyperthermic. Considering that most mammals defend constant Tbs within the range of predicted Tw maxima increases that future Tw conditions may pose a significant threat to mammalian thermoregulation. However, to date, despite being well supported in the literature, ii empirical investigations into how extreme Tw conditions will affect endothermic thermoregulation are scant. Therefore, understanding of the proposed inhibitory nature of extreme Tw conditions is lacking. Considering that such conditions are to have a profound effect of endothermic survival, this dearth in understanding could prove fatal. As such, this thesis sought to provide evidence on how extreme Tw conditions may affect thermoregulatory processes in homeothermic endotherms. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Hartley, Oliver
- Date: 2023-04
- Subjects: Heat stress physiology , Small mammal thermoregulation -- South Africa , Climate change - Wet-bulb temperature
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60873 , vital:68916
- Description: As the Anthropocene continues to be characterised by ever rising temperature highs, increasingly sporadic and extreme climatic events, and their accompanying mass mortality events, climate scientists now warn that the continued climate destabilisation may for the first time in recorded history prevent terrestrial homeothermic endotherms from being able to thermoregulate. Having evolved to maintain body temperatures (Tbs) well above their ambient (Ta) conditions, these endotherms have evolved a suite of adaptations to a colder environment to allow for homeothermic thermoregulation to occur. However, by the same vein, having evolved in a colder climate to stay warm also has led to a reduced capacity to prevent heat stress when temperature conditions are elevated. In absence of behavioural counter measures, the only physiological means available to thermoregulation to prevent such heat stress is that of evaporative water loss (EWL). If still inefficient, the endotherm will risk becoming hyperthermic. Literature has established that excessive heat exposure or reduced evaporative cooling capacities strain or retard thermoregulatory processes. If an endotherm experiences severe heat exposure, the rate at which passive heating is experienced will increase. Should an endotherm be in a humid environment, evaporative cooling efficiency is reduced. As a result, these two abiotic factors are therefore known to contribute towards heat storage, and therefore thermal stress. However, should both factors occur in the same environment, the heat stress effects are compounded, creating an environment dangerous for thermoregulating endotherms. For this reason, authors have emphasised that future wet-bulb (Tw) conditions may pose a penultimate threat to thermoregulating endotherms. Being a measure of coldest temperature attainable as a result of evaporative cooling, Tw has been proposed to represent a lower temperature thermal limit to endothermic thermoregulation. Once reaching a 2°C differential below an endotherms Tb (Tb – Tw = 2˚C), Tw is believed to impede the evaporative cooling process and, consequentially, commit endotherms to becoming hyperthermic. Considering that most mammals defend constant Tbs within the range of predicted Tw maxima increases that future Tw conditions may pose a significant threat to mammalian thermoregulation. However, to date, despite being well supported in the literature, ii empirical investigations into how extreme Tw conditions will affect endothermic thermoregulation are scant. Therefore, understanding of the proposed inhibitory nature of extreme Tw conditions is lacking. Considering that such conditions are to have a profound effect of endothermic survival, this dearth in understanding could prove fatal. As such, this thesis sought to provide evidence on how extreme Tw conditions may affect thermoregulatory processes in homeothermic endotherms. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Isolation, characterization and functionalization of cellulose fibres derived from the waste pineapple leaf fibres by hydrolysis to produce cellulose acetate
- Authors: Seyisi, Thulethu
- Date: 2023-04
- Subjects: Nonwoven fabrics -- Technological innovations , Pineapple fiber -- South Africa , Fibrous composites
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61248 , vital:69844
- Description: This thesis forms part of the Nelson Mandela University biomass and nanotechnology project, which aims at using agricultural waste for many applications, including biomedical applications, water treatment, and agricultural films. Pineapple leaf fiber (PALF) is one of the natural fibers with the highest cellulose content (about 80%), and they produce about 2.5–3.3% of the weight of green leaves. However, the other parts of the pineapple fruit, such as the leaves and crown, are still treated as waste due to a lack of understanding of the benefits and risks of these parts of the pineapple fruit. The transformation of PALF as a renewable and abundantly available natural residue into cellulose fibers (CFs) will reduce the waste accumulated in the atmosphere, and it will add value to the cultivation of pineapple. In the biomedical industry, CF is very promising in terms of drug delivery. Cellulose acetate is a remarkable biomaterial extensively used in biomedical applications due to its properties such as being non-toxic, non-irritant, biodegradable, heat resistant, and less hygroscopic. In this research, the isolation, functionalization, and characterization of cellulose from PALFs were conducted. The PALFs were dried and ground into small particles before being alkali treated with sodium hydroxide to remove the non-cellulosic components. Moreover, the remaining lignin in the residue was removed using sodium chlorite and acetic acid; this process is known as the bleaching process. The bleaching process resulted in white CFs, which was an indication of the successful removal of the non-cellulosic material. The obtained CFs were further functionalized using acetic acid, acetic anhydride, and sulfuric acid, and this reaction is known as the acetylation reaction. Subsequently, both treated, untreated, and functionalized CFs were characterised using the following instruments: FTIR, SEM, SPM, TGA, XRD, and XPS. In the FTIR data of raw PALFs, the following functional groups were more pronounced: C-O, C=C-O, and C=O, whereas peak C-O-C disappeared and peak CH2, C-O, were less pronounced. These FTIR results confirmed the successful removal of non-cellulosic components. The SEM and SPM images visually suggested the partial removal of hemicellulose and lignin from the raw PALFs after the chemical treatment, which are the cementing materials around the fiber bundles. The TGA studies revealed good thermal stability for the isolated CFs from PALFs. The XRD diffractograms of the PALFs showed a cellulose I crystal pattern where the peaks were located at angular positions (2θ) of around 18°, 26°, and 41°. Lastly, after the functionalization of CFs, the cellulose structure remained intact (not damaged); instead, the newly ix introduced functional groups (the acetyl group) were attached at the ends of the cellulose structure. These results are therefore confirmation of the successful removal of non-cellulose material from the PALFs after the chemical treatment. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Seyisi, Thulethu
- Date: 2023-04
- Subjects: Nonwoven fabrics -- Technological innovations , Pineapple fiber -- South Africa , Fibrous composites
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61248 , vital:69844
- Description: This thesis forms part of the Nelson Mandela University biomass and nanotechnology project, which aims at using agricultural waste for many applications, including biomedical applications, water treatment, and agricultural films. Pineapple leaf fiber (PALF) is one of the natural fibers with the highest cellulose content (about 80%), and they produce about 2.5–3.3% of the weight of green leaves. However, the other parts of the pineapple fruit, such as the leaves and crown, are still treated as waste due to a lack of understanding of the benefits and risks of these parts of the pineapple fruit. The transformation of PALF as a renewable and abundantly available natural residue into cellulose fibers (CFs) will reduce the waste accumulated in the atmosphere, and it will add value to the cultivation of pineapple. In the biomedical industry, CF is very promising in terms of drug delivery. Cellulose acetate is a remarkable biomaterial extensively used in biomedical applications due to its properties such as being non-toxic, non-irritant, biodegradable, heat resistant, and less hygroscopic. In this research, the isolation, functionalization, and characterization of cellulose from PALFs were conducted. The PALFs were dried and ground into small particles before being alkali treated with sodium hydroxide to remove the non-cellulosic components. Moreover, the remaining lignin in the residue was removed using sodium chlorite and acetic acid; this process is known as the bleaching process. The bleaching process resulted in white CFs, which was an indication of the successful removal of the non-cellulosic material. The obtained CFs were further functionalized using acetic acid, acetic anhydride, and sulfuric acid, and this reaction is known as the acetylation reaction. Subsequently, both treated, untreated, and functionalized CFs were characterised using the following instruments: FTIR, SEM, SPM, TGA, XRD, and XPS. In the FTIR data of raw PALFs, the following functional groups were more pronounced: C-O, C=C-O, and C=O, whereas peak C-O-C disappeared and peak CH2, C-O, were less pronounced. These FTIR results confirmed the successful removal of non-cellulosic components. The SEM and SPM images visually suggested the partial removal of hemicellulose and lignin from the raw PALFs after the chemical treatment, which are the cementing materials around the fiber bundles. The TGA studies revealed good thermal stability for the isolated CFs from PALFs. The XRD diffractograms of the PALFs showed a cellulose I crystal pattern where the peaks were located at angular positions (2θ) of around 18°, 26°, and 41°. Lastly, after the functionalization of CFs, the cellulose structure remained intact (not damaged); instead, the newly ix introduced functional groups (the acetyl group) were attached at the ends of the cellulose structure. These results are therefore confirmation of the successful removal of non-cellulose material from the PALFs after the chemical treatment. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
Modelling the dynamics of Breast Cancer disease with hormone therapy and surgery controls
- Ngalo, Akhona Sunshine, Mbava,Willard
- Authors: Ngalo, Akhona Sunshine , Mbava,Willard
- Date: 2023-04
- Subjects: Cancer -- Molecular aspects , Breast cancer -- South Africa , Hormone therapy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61487 , vital:70688
- Description: In this study, we discussed a mathematical model that incorporates important interactions between normal cells, tumor cells, immune cells, and estrogen. The mathematical model was revised to include two control measures; namely surgery and hormone therapy to minimize the number of tumor cells. The model was mathematically analyzed with the premise that the two control measures are positive constants. Locally and globally analyses were performed using a variety of analytical methods to investigate the stability of the breast cancer model. Furthermore, an optimal control problem was formulated and used to determine the best strategy for reducing the number of tumor cells by incorporating hormone therapy and surgery, based on the well-known Pontryagin’s Maximum Principle. The numerical results indicates combining both optimal control measures (surgery and hormone therapy) simultaneously is more efficacious than using single control measure separately in decreasing the number of tumor cells. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Ngalo, Akhona Sunshine , Mbava,Willard
- Date: 2023-04
- Subjects: Cancer -- Molecular aspects , Breast cancer -- South Africa , Hormone therapy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61487 , vital:70688
- Description: In this study, we discussed a mathematical model that incorporates important interactions between normal cells, tumor cells, immune cells, and estrogen. The mathematical model was revised to include two control measures; namely surgery and hormone therapy to minimize the number of tumor cells. The model was mathematically analyzed with the premise that the two control measures are positive constants. Locally and globally analyses were performed using a variety of analytical methods to investigate the stability of the breast cancer model. Furthermore, an optimal control problem was formulated and used to determine the best strategy for reducing the number of tumor cells by incorporating hormone therapy and surgery, based on the well-known Pontryagin’s Maximum Principle. The numerical results indicates combining both optimal control measures (surgery and hormone therapy) simultaneously is more efficacious than using single control measure separately in decreasing the number of tumor cells. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2023
- Full Text:
- Date Issued: 2023-04
South African plantation forest nursery pesticide -use: current status, pesticide identification for management, and screening of fungicides for pathogen control
- Authors: Opperman, Ilke
- Date: 2023-04
- Subjects: Forest insects –Control – South Africa , Pesticides -- Environmental aspects , Pest management
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61370 , vital:70618
- Description: Forest nurseries are exposed to many challenges during the production of plant material, with pests and pathogens two of the most important. Management of pests and diseases require the use of multiple methods, including cultural, biological, and chemical control strategies in an integrated nursery pest management plan (IPM). In most nurseries, where hygiene practices and biological controls do not prevent the presence of pests and pathogens, they are managed through the use of pesticides. Forestry companies are regulated by both Government and Forestry Certification bodies. These include South African legislation pertaining to pesticides regulated by the Registrar Act 36 of 1947, the Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification (PEFC). A limited number of pesticides, with an even more limited range of active ingredients, and not targeting all known plantation forestry pests/pathogens, are currently registered for use against pests and pathogens in plantation forestry in South Africa. Many of these have been in use for more than a decade, posing a serious risk in terms of resistance build-up. There is a major need for the identification and testing of additional/alternative products (biological natural or synthetic) for use against the range of pests and pathogens that occur on the various plantation tree species and hybrid combinations that are raised in nurseries. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science & Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Opperman, Ilke
- Date: 2023-04
- Subjects: Forest insects –Control – South Africa , Pesticides -- Environmental aspects , Pest management
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61370 , vital:70618
- Description: Forest nurseries are exposed to many challenges during the production of plant material, with pests and pathogens two of the most important. Management of pests and diseases require the use of multiple methods, including cultural, biological, and chemical control strategies in an integrated nursery pest management plan (IPM). In most nurseries, where hygiene practices and biological controls do not prevent the presence of pests and pathogens, they are managed through the use of pesticides. Forestry companies are regulated by both Government and Forestry Certification bodies. These include South African legislation pertaining to pesticides regulated by the Registrar Act 36 of 1947, the Forest Stewardship Council (FSC) and the Programme for the Endorsement of Forest Certification (PEFC). A limited number of pesticides, with an even more limited range of active ingredients, and not targeting all known plantation forestry pests/pathogens, are currently registered for use against pests and pathogens in plantation forestry in South Africa. Many of these have been in use for more than a decade, posing a serious risk in terms of resistance build-up. There is a major need for the identification and testing of additional/alternative products (biological natural or synthetic) for use against the range of pests and pathogens that occur on the various plantation tree species and hybrid combinations that are raised in nurseries. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science & Management, 2023
- Full Text:
- Date Issued: 2023-04
The design and synthesis of novel fluorescent coumarin-based derivatives as chemosensory for the application of toxic metal ion detection
- Authors: Schoeman,Stiaan
- Date: 2023-04
- Subjects: Fluorescent polymers -- South Africa , Polymerization , Chemosensory
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61270 , vital:69851
- Description: The rise of humankind has caused pollution, increasing damage to the environment. The actions of humans over hundreds of years have led to an increase in the release of heavy metal cations in concentrations that are toxic to plants, animals and humans. These toxic metals can find their way into humans’ diets through water sources or bioaccumulation in plants and animals such as fish. Heavy metals such as lead and mercury are known to cause serious health issues when consumed, affecting the functioning of the circulatory and nervous systems and causing developmental disorders. Other metal cations, such as iron and copper, can be found in the human body. However, detrimental health issues can occur when normal concentrations are disturbed (either too high or too low). Iron, for example, can be toxic if in excess in the human body, causing damage to the liver and heart and can cause neuroinflammation and Alzheimer’s disease. Many methods have been employed to detect and measure the concentrations of toxic metal cations. However, these methods are performed in a laboratory and need skilled operators using expensive equipment. This results in long and tedious sample collection, long feedback time and costly analysis. Chemosensors have been researched and proposed as a cost-effective, on-site, real-time alternative for use as metal detectors. Chemosensory can selectively detect specific metal cations and can be sensitive up to the nanomolar range. Various chemosensors have been synthesised and screened for their colourimetric and fluorometric abilities. Colourimetric chemosensors can be used to visually detect cationic and anionic analytes, whereas fluorometric chemosensors are used to detect anions using their emission properties which handheld devices can measure. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Schoeman,Stiaan
- Date: 2023-04
- Subjects: Fluorescent polymers -- South Africa , Polymerization , Chemosensory
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61270 , vital:69851
- Description: The rise of humankind has caused pollution, increasing damage to the environment. The actions of humans over hundreds of years have led to an increase in the release of heavy metal cations in concentrations that are toxic to plants, animals and humans. These toxic metals can find their way into humans’ diets through water sources or bioaccumulation in plants and animals such as fish. Heavy metals such as lead and mercury are known to cause serious health issues when consumed, affecting the functioning of the circulatory and nervous systems and causing developmental disorders. Other metal cations, such as iron and copper, can be found in the human body. However, detrimental health issues can occur when normal concentrations are disturbed (either too high or too low). Iron, for example, can be toxic if in excess in the human body, causing damage to the liver and heart and can cause neuroinflammation and Alzheimer’s disease. Many methods have been employed to detect and measure the concentrations of toxic metal cations. However, these methods are performed in a laboratory and need skilled operators using expensive equipment. This results in long and tedious sample collection, long feedback time and costly analysis. Chemosensors have been researched and proposed as a cost-effective, on-site, real-time alternative for use as metal detectors. Chemosensory can selectively detect specific metal cations and can be sensitive up to the nanomolar range. Various chemosensors have been synthesised and screened for their colourimetric and fluorometric abilities. Colourimetric chemosensors can be used to visually detect cationic and anionic analytes, whereas fluorometric chemosensors are used to detect anions using their emission properties which handheld devices can measure. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
The influence of site characteristics on growth and wood properties of Pinus radiata and Pinus elliottii in the Southern and Eastern Cape forestry regions of South Africa
- Authors: Sigcau, Chulumanco
- Date: 2023-04
- Subjects: Forests and forestry -- Environmental aspects , Pine – Growth -- South Africa , Pinus radiata
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61234 , vital:69828
- Description: The intensive nature of plantation forestry in South Africa requires efficiency and financial viability in production systems, amidst a complex growing environment subjected to changing macro-climatic patterns. The success of plantation forestry operations depends, amongst others, on our understanding of tree growth and wood formation patterns in response to variable growing conditions in both space and time. This study was conducted on the two most commonly used species in the southern and Eastern Cape forestry regions, i.e., Pinus radiata and P. elliottii. The region is regarded as highly suitable for plantation forestry in terms of climatic conditions, but soil characteristics pose several challenges due to nutritional disorders and poor drainage. The study focused on investigating the influence of both soil and climatic conditions on the growth and Wood Density properties of the two species, and to establish functional relationships where possible. The two species showed comparable growth rates at the reference age of 13 years on the range of sites sampled in the study area. An analysis of variance showed greater differences in Site Index between than within sample plots, pointing towards the possible influence of site on growth variation. Correlations between climatic variables and the growth of both species were generally weak and contradictory. Possible reasons for this phenomenon are discussed. It is proposed that the general favourable climatic profile of the region and hydromorphic nature of soils reduce the chances of significant correlations between variables influencing moisture availability and tree growth. The analysis of correlations between soil parameters and tree growth revealed some influence of soil organic C and Na on the growth of P. elliottii. This is discussed in terms of our understanding of the influence of soil parent material and soil ecology. The absence of any correlations between soil chemical parameters and the growth of P. radiata was conspicuous. This is in contradiction with earlier studies on the species in the region and can possibly be explained in terms of the site-specific fertilizing policy of the industry, as well as the less diverse range of sites sampled than in the past, which can mask or reduce nutrient limitations for tree growth. However, P. radiata did show a high level of sensitivity towards effective soil depth. Site-quality prediction models are proposed for the two species, but with variable application value due to the limited options of significant control variables that can be considered for inclusion in the models. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Sigcau, Chulumanco
- Date: 2023-04
- Subjects: Forests and forestry -- Environmental aspects , Pine – Growth -- South Africa , Pinus radiata
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61234 , vital:69828
- Description: The intensive nature of plantation forestry in South Africa requires efficiency and financial viability in production systems, amidst a complex growing environment subjected to changing macro-climatic patterns. The success of plantation forestry operations depends, amongst others, on our understanding of tree growth and wood formation patterns in response to variable growing conditions in both space and time. This study was conducted on the two most commonly used species in the southern and Eastern Cape forestry regions, i.e., Pinus radiata and P. elliottii. The region is regarded as highly suitable for plantation forestry in terms of climatic conditions, but soil characteristics pose several challenges due to nutritional disorders and poor drainage. The study focused on investigating the influence of both soil and climatic conditions on the growth and Wood Density properties of the two species, and to establish functional relationships where possible. The two species showed comparable growth rates at the reference age of 13 years on the range of sites sampled in the study area. An analysis of variance showed greater differences in Site Index between than within sample plots, pointing towards the possible influence of site on growth variation. Correlations between climatic variables and the growth of both species were generally weak and contradictory. Possible reasons for this phenomenon are discussed. It is proposed that the general favourable climatic profile of the region and hydromorphic nature of soils reduce the chances of significant correlations between variables influencing moisture availability and tree growth. The analysis of correlations between soil parameters and tree growth revealed some influence of soil organic C and Na on the growth of P. elliottii. This is discussed in terms of our understanding of the influence of soil parent material and soil ecology. The absence of any correlations between soil chemical parameters and the growth of P. radiata was conspicuous. This is in contradiction with earlier studies on the species in the region and can possibly be explained in terms of the site-specific fertilizing policy of the industry, as well as the less diverse range of sites sampled than in the past, which can mask or reduce nutrient limitations for tree growth. However, P. radiata did show a high level of sensitivity towards effective soil depth. Site-quality prediction models are proposed for the two species, but with variable application value due to the limited options of significant control variables that can be considered for inclusion in the models. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
The quantification of Pinus patula recovery and productivity of manually orientated biomass collection in post mechanised full tree and semi mechanised tree length harvesting operations
- Authors: Ncongwane, Thandekile Hazel
- Date: 2023-04
- Subjects: Pinus patula – south Africa , Forest ecology , Biomass energy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61511 , vital:70692
- Description: The use of biomass as an alternate source of energy has grown in popularity. Different types of biomass are obtained from a variety of sources including natural forests, forestry plantations and agriculture residues. However, forestry residues have been identified as the most promising source, due to the wide variety of plant products including leaves, twigs, branches, merchantable stem, stumps and roots. The main sources of plantation forest biomass are residues from thinning, clearfell and conventional products such as pulpwood and sawn timber operations. These residues can accumulate between 4.3 to 9.4 billion tonnes annually around the world. The biomass availability in plantation forests has led to the development of different harvesting systems to help collect the products from infield to sawmill. Biomass harvesting has mainly been achieved through mechanised systems because of their high yields. However, the use of manual systems has been neglected due to technical limitations and financial viability. Thus, in South Africa, there is no scientific research looking at manual systems of collecting biomass from plantations. Because of this, different forestry stakeholders, including small growers and contractors using manual systems for biomass harvesting have limited knowledge regarding what to expect in terms of recoverable amounts, productivity and cost. This research examines the productivity of the manual biomass collection and the quantification of recovered and unrecovered residues after mechanised full tree (FT) and semi mechanised tree length (TL) harvesting operations in Pinus patula compartments. A total number of 8 plots with +/-200 standing trees were marked in each system. The diameter and height of all marked trees were measured to determine tree volume. Moreover, the quantification of recoverable woody biomass was determined, where after, a residues assessment method using plots and line transects was used to determine the amount of unrecovered residues. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Ncongwane, Thandekile Hazel
- Date: 2023-04
- Subjects: Pinus patula – south Africa , Forest ecology , Biomass energy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61511 , vital:70692
- Description: The use of biomass as an alternate source of energy has grown in popularity. Different types of biomass are obtained from a variety of sources including natural forests, forestry plantations and agriculture residues. However, forestry residues have been identified as the most promising source, due to the wide variety of plant products including leaves, twigs, branches, merchantable stem, stumps and roots. The main sources of plantation forest biomass are residues from thinning, clearfell and conventional products such as pulpwood and sawn timber operations. These residues can accumulate between 4.3 to 9.4 billion tonnes annually around the world. The biomass availability in plantation forests has led to the development of different harvesting systems to help collect the products from infield to sawmill. Biomass harvesting has mainly been achieved through mechanised systems because of their high yields. However, the use of manual systems has been neglected due to technical limitations and financial viability. Thus, in South Africa, there is no scientific research looking at manual systems of collecting biomass from plantations. Because of this, different forestry stakeholders, including small growers and contractors using manual systems for biomass harvesting have limited knowledge regarding what to expect in terms of recoverable amounts, productivity and cost. This research examines the productivity of the manual biomass collection and the quantification of recovered and unrecovered residues after mechanised full tree (FT) and semi mechanised tree length (TL) harvesting operations in Pinus patula compartments. A total number of 8 plots with +/-200 standing trees were marked in each system. The diameter and height of all marked trees were measured to determine tree volume. Moreover, the quantification of recoverable woody biomass was determined, where after, a residues assessment method using plots and line transects was used to determine the amount of unrecovered residues. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Top-down control by grapsoid crabs in South African estuarine salt marshes
- Authors: Smith, Leigh-Ann
- Date: 2023-04
- Subjects: Salt marsh ecology – South Africa , Crabs --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61223 , vital:69807
- Description: Salt marshes are one of the most productive ecosystems globally. These ‘blue carbon’ habitats are in many respects resilient to climate change effects, able to track sea level rise and act as carbon sinks. Since salt marshes are economically and ecologically essential habitats (for example providing foraging grounds for invertebrates, fish, birds and humans), understanding the processes that control their structure is crucial to best maintain ecosystem services provided by these habitats. For decades the importance of top-down forces, such as grazing, has not been recognised as being important in controlling salt marsh plant productivity. Rather, bottom-up forces, such as the availability of oxygen, was thought to be the main constraint to primary production. Therefore, a better understanding of salt marsh ecosystem dynamics and whether grazer control exists is needed. Although grazer top-down control has been demonstrated in salt marshes in locations such as the United States, this has not been investigated in South Africa. This is a crucial knowledge gap locally considering the importance of salt marsh ecosystems. The aim of this study was therefore to determine what role consumers play in structuring South Africa’s estuarine salt marsh vegetation, thereby also contextualising this process internationally. In order to achieve this, the abundance of grapsoid crabs was estimated and related to key salt marsh features, such as Spartina maritima stem height and stem density, which was quantified from observational surveys. Sampling took place at the beginning and end of the early-spring and late-summer growth period (September 2021 and April 2022) in the Knysna, Kromme and Swartkops estuaries. If a correlation was observed between crab density and salt marsh features, it was important to determine whether they consume the salt marsh vegetation or if the effect was due to their burrowing activities. Hence, the diet of grapsoid crabs was investigated using stable isotope and gut content analysis. To examine the importance of crab grazing in controlling the growth of salt marsh vegetation, crab abundance was manipulated in situ by means of exclusion cages. This experiment ran for five months in the Kromme Estuary, from November 2021 to March 2022 over the salt marsh growing season. An ex situ feeding experiment was also conducted on 30 crab specimens collected from the Kromme Estuary, during May 2022. These crabs were starved for 48 hours and thereafter fed different components of Spartina (growing and dead blades, and roots and rhizomes). The food consumed was quantified as the change in plant length and dry weight after 48 hours, which gave a maximum grazing rate for the different food sources. It was found that crabs are having a minimal impact on the salt marsh vegetation structure. Spartina maritima does form an important component of the diet of grapsoid crabs, however, this is not their only source of food, and possibly not their preferred source of food. They are however contributing to sediment properties through their burrowing activities. The iii ex situ feeding experiment showed that grapsoid crabs can consume all vegetative components of Spartina, with a significantly greater amount of roots and rhizomes consumed. There was no consistent effect in terms of the exclusion of grazers, indicating that other mitigating factors could be reducing the impacts of grapsoid exclusion in situ. Together, these findings contribute knowledge that can be used to inform conservation by quantifying what the salt marsh risks losing in the absence or overabundance of crabs, as has occurred elsewhere globally. These results influence how salt marshes are managed, and highlight how not recognising the importance of consumers, such as crabs, could misalign management objectives. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2023-04
- Authors: Smith, Leigh-Ann
- Date: 2023-04
- Subjects: Salt marsh ecology – South Africa , Crabs --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61223 , vital:69807
- Description: Salt marshes are one of the most productive ecosystems globally. These ‘blue carbon’ habitats are in many respects resilient to climate change effects, able to track sea level rise and act as carbon sinks. Since salt marshes are economically and ecologically essential habitats (for example providing foraging grounds for invertebrates, fish, birds and humans), understanding the processes that control their structure is crucial to best maintain ecosystem services provided by these habitats. For decades the importance of top-down forces, such as grazing, has not been recognised as being important in controlling salt marsh plant productivity. Rather, bottom-up forces, such as the availability of oxygen, was thought to be the main constraint to primary production. Therefore, a better understanding of salt marsh ecosystem dynamics and whether grazer control exists is needed. Although grazer top-down control has been demonstrated in salt marshes in locations such as the United States, this has not been investigated in South Africa. This is a crucial knowledge gap locally considering the importance of salt marsh ecosystems. The aim of this study was therefore to determine what role consumers play in structuring South Africa’s estuarine salt marsh vegetation, thereby also contextualising this process internationally. In order to achieve this, the abundance of grapsoid crabs was estimated and related to key salt marsh features, such as Spartina maritima stem height and stem density, which was quantified from observational surveys. Sampling took place at the beginning and end of the early-spring and late-summer growth period (September 2021 and April 2022) in the Knysna, Kromme and Swartkops estuaries. If a correlation was observed between crab density and salt marsh features, it was important to determine whether they consume the salt marsh vegetation or if the effect was due to their burrowing activities. Hence, the diet of grapsoid crabs was investigated using stable isotope and gut content analysis. To examine the importance of crab grazing in controlling the growth of salt marsh vegetation, crab abundance was manipulated in situ by means of exclusion cages. This experiment ran for five months in the Kromme Estuary, from November 2021 to March 2022 over the salt marsh growing season. An ex situ feeding experiment was also conducted on 30 crab specimens collected from the Kromme Estuary, during May 2022. These crabs were starved for 48 hours and thereafter fed different components of Spartina (growing and dead blades, and roots and rhizomes). The food consumed was quantified as the change in plant length and dry weight after 48 hours, which gave a maximum grazing rate for the different food sources. It was found that crabs are having a minimal impact on the salt marsh vegetation structure. Spartina maritima does form an important component of the diet of grapsoid crabs, however, this is not their only source of food, and possibly not their preferred source of food. They are however contributing to sediment properties through their burrowing activities. The iii ex situ feeding experiment showed that grapsoid crabs can consume all vegetative components of Spartina, with a significantly greater amount of roots and rhizomes consumed. There was no consistent effect in terms of the exclusion of grazers, indicating that other mitigating factors could be reducing the impacts of grapsoid exclusion in situ. Together, these findings contribute knowledge that can be used to inform conservation by quantifying what the salt marsh risks losing in the absence or overabundance of crabs, as has occurred elsewhere globally. These results influence how salt marshes are managed, and highlight how not recognising the importance of consumers, such as crabs, could misalign management objectives. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2023-04
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