The effect of phosphorus fertilizer application on growth, biomass and nutritive value of Pigeon pea (Cajanus cajan (L.) Millsp.) varieties in Alice, South Africa
- Authors: Mpabanga, Nkosi
- Date: 2017
- Subjects: Phosphatic fertilizers Soil fertility Plants -- Effect of phosphorus on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6180 , vital:29501
- Description: Low soil fertility has been identified to be among the major causes of low pasture quantity and quality. Scarcity of high quality forage mainly during the dry season threatens animal productivity in some areas of South Africa, thus the need for identifying livestock feed alternatives. Pigeon pea is a woody legume that has continually been an important shrub in agroforestry and can provide protein-rich livestock feed during times of shortage. Soil fertility to support the production of pigeon pea can be enhanced by application of fertilisers. Therefore, this study was carried out firstly, to determine the effect of phosphorus fertiliser on the growth performance and biomass production of three pigeon pea varieties, and secondly, to investigate the influence of phosphorus application on the nutrient and anti-nutrient content of three pigeon pea varieties. The field experiment was done at the University of Fort Hare research farm in Alice, South Africa. The factors investigated were three pigeon pea varieties namely Chitedze 1, Chitedze 2 and CIMMYT 1 and three phosphorus fertiliser application rates of 0, 40 and 60 kg P/ha. The study was a 3× 3 factorial experiment set up in a randomised complete block design and was replicated three times. The growth performance attributes evaluated in this study include the number of branches, plant height and root collar diameter. Root collar diameter was not significantly (p>0.05) different among the pigeon pea varieties and phosphorus levels. Likewise, the application of phosphorus was not significant (p>0.05) on plant height and the number of branches of all the varieties. However, when P level was varied, there were significant differences among the varieties, and so were the interaction (p<0.05) between variety and phosphorus on plant height and the number of branches. There was no significant (p>0.05) difference among the phosphorus levels on the fresh leaf yield of Chitedze 1 and Chitedze 2, but phosphorus application at 40 kg P/ha increased the fresh leaf yield of CIMMYT 1. Phosphorus application at 60 kg P/ha increased (p<0.05) the dry matter content of Chitedze 1 and Chitedze 2. Furthermore, the results of the trial show that the application of 40 kg P/ha and 60 kg P/ha increased (p<0.05) the dry matter yield of the varieties CIMMYT 1 and Chitedze 2, respectively. The effects of phosphorus application on the nutrient composition of the three pigeon pea varieties varied. The composition of hemicellulose of all the varieties was significantly (p<0.05) increased by the application of 40 kg P/ha. Conversely, the concentration of crude protein, phosphorus, copper and iron, and the calcium to phosphorus ratio of all the pigeon pea varieties was not significantly (p>0.05) affected by phosphorus application and there was no interactive effect of variety and phosphorus. The proximate compositions of fat, total non-structural carbohydrates, ash, neutral detergent fibre, acid detergent fibre, cellulose, neutral detergent insoluble nitrogen, acid detergent insoluble nitrogen of the pigeon pea varieties varied significantly (p<0.05) at different phosphorus application levels. There was an interactive (p<0.05) effect of variety and the level of phosphorus on the concentration of calcium (Ca), potassium (K), magnesium (Mg), sodium, zinc, manganese, and the K/(Ca+Mg) ratio. The digestible dry matter, dry matter intake and the relative feed value were significantly (p<0.05) different among the pigeon pea varieties at varying phosphorus levels. The anti-nutrient composition of Chitedze 2 was not significantly (p>0.05) affected by phosphorus application but the concentration of phenols and saponins of Chitedze 1 was significantly (p<0.05) increased when 60 kg P/ha was applied, but these anti-nutrients were reduced (p<0.05) for CIMMYT 1 at 60 kg P/ha. It can be concluded that phosphorus application influences the biomass production and chemical composition while the optimum phosphorus level vary among the pigeon pea varieties.
- Full Text:
- Date Issued: 2017
- Authors: Mpabanga, Nkosi
- Date: 2017
- Subjects: Phosphatic fertilizers Soil fertility Plants -- Effect of phosphorus on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6180 , vital:29501
- Description: Low soil fertility has been identified to be among the major causes of low pasture quantity and quality. Scarcity of high quality forage mainly during the dry season threatens animal productivity in some areas of South Africa, thus the need for identifying livestock feed alternatives. Pigeon pea is a woody legume that has continually been an important shrub in agroforestry and can provide protein-rich livestock feed during times of shortage. Soil fertility to support the production of pigeon pea can be enhanced by application of fertilisers. Therefore, this study was carried out firstly, to determine the effect of phosphorus fertiliser on the growth performance and biomass production of three pigeon pea varieties, and secondly, to investigate the influence of phosphorus application on the nutrient and anti-nutrient content of three pigeon pea varieties. The field experiment was done at the University of Fort Hare research farm in Alice, South Africa. The factors investigated were three pigeon pea varieties namely Chitedze 1, Chitedze 2 and CIMMYT 1 and three phosphorus fertiliser application rates of 0, 40 and 60 kg P/ha. The study was a 3× 3 factorial experiment set up in a randomised complete block design and was replicated three times. The growth performance attributes evaluated in this study include the number of branches, plant height and root collar diameter. Root collar diameter was not significantly (p>0.05) different among the pigeon pea varieties and phosphorus levels. Likewise, the application of phosphorus was not significant (p>0.05) on plant height and the number of branches of all the varieties. However, when P level was varied, there were significant differences among the varieties, and so were the interaction (p<0.05) between variety and phosphorus on plant height and the number of branches. There was no significant (p>0.05) difference among the phosphorus levels on the fresh leaf yield of Chitedze 1 and Chitedze 2, but phosphorus application at 40 kg P/ha increased the fresh leaf yield of CIMMYT 1. Phosphorus application at 60 kg P/ha increased (p<0.05) the dry matter content of Chitedze 1 and Chitedze 2. Furthermore, the results of the trial show that the application of 40 kg P/ha and 60 kg P/ha increased (p<0.05) the dry matter yield of the varieties CIMMYT 1 and Chitedze 2, respectively. The effects of phosphorus application on the nutrient composition of the three pigeon pea varieties varied. The composition of hemicellulose of all the varieties was significantly (p<0.05) increased by the application of 40 kg P/ha. Conversely, the concentration of crude protein, phosphorus, copper and iron, and the calcium to phosphorus ratio of all the pigeon pea varieties was not significantly (p>0.05) affected by phosphorus application and there was no interactive effect of variety and phosphorus. The proximate compositions of fat, total non-structural carbohydrates, ash, neutral detergent fibre, acid detergent fibre, cellulose, neutral detergent insoluble nitrogen, acid detergent insoluble nitrogen of the pigeon pea varieties varied significantly (p<0.05) at different phosphorus application levels. There was an interactive (p<0.05) effect of variety and the level of phosphorus on the concentration of calcium (Ca), potassium (K), magnesium (Mg), sodium, zinc, manganese, and the K/(Ca+Mg) ratio. The digestible dry matter, dry matter intake and the relative feed value were significantly (p<0.05) different among the pigeon pea varieties at varying phosphorus levels. The anti-nutrient composition of Chitedze 2 was not significantly (p>0.05) affected by phosphorus application but the concentration of phenols and saponins of Chitedze 1 was significantly (p<0.05) increased when 60 kg P/ha was applied, but these anti-nutrients were reduced (p<0.05) for CIMMYT 1 at 60 kg P/ha. It can be concluded that phosphorus application influences the biomass production and chemical composition while the optimum phosphorus level vary among the pigeon pea varieties.
- Full Text:
- Date Issued: 2017
The effect of quantitative feed restriction on growth performance, carcass characteristics and selected meat quality parameters in broiler chickens
- Authors: Velele, Siphelo
- Date: 2017
- Subjects: Broilers (Chickens) Poultry -- Breeding Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8888 , vital:33907
- Description: The study investigated the effects of quantitative feed restriction on growth performance, carcass characteristics, internal organs, breast muscle pH and meat colour in broiler chickens. A total of 90, un-sexed, day-old broiler chicks were procured from an accredited supplier and were used for the current trial. For the first 14 days, all birds were brooded in one house and subjected to a uniform day-to-day management. Water was supplied throughout the trial, whereas, feed was only supplied ad libitum between days 1-14 and 29-35 days in feed restricted birds. Feed phases included starter (1-14 days), grower (15-28) and finisher (29-35), respectively. On day 15, birds were randomly allocated to three treatments; each treatment was replicated three times with 10 birds per replicate. The first treatment (T1) group, which acted as control group, was ad libitum feeding for the whole trial duration (1-35 days). For treatments 2 (T2) and 3(T3), 85 percent and 70 percent of the Cobb 500 broiler feed intake standards were applied for a period of 14 days (days 15-28), respectively. Average daily feed intake (ADFI) was determined daily and then average body weight (ABW) was determined weekly. Feed conversion ratio and average daily weight gain was thus computed for each experimental unit (replicate). On day 35, broiler birds were electrically stunned and slaughtered by a sharp knife and then hung for complete bleeding. Data collected included slaughter, carcass, breast, thigh, wing, drumstick, feet, head, spleen, heart, gizzard, intestines (small & large) and liver weights. Breast muscle was further used for the determination of colour (L*, b* and a*), initial (pHi) and ultimate breast pH (pHu) measurements. Although, quantitative feed restriction (T2 & T3) significantly affected growth performance in weeks 3 and 4, birds submitted to T2 performed similar (P>0.05) to control in the final stage, whilst birds in T3 was the poorest (P<0.05). Furthermore, birds subjected to T2 showed no differences of edible carcass portions to the control, however, T3 group showed lower (P<0.05) slaughter and wing weights. Breast ultimate pH values of birds under T2 were similar to control, but birds in T3 had significantly higher (P<0.05) values. Birds under T2 had less (P<0.05) reddish breast meat colour than control at 45 minutes. At 24 hours post-mortem, birds in T3 had lower (P<0.05) lightness values and birds submitted to T2 had higher (P<0.05) yellowness values. Liver weight was significantly lower in birds under T3 and higher (P<0.05) gizzard weights were found in birds subjected to T2. Birds under T2 performed similar to control and were able to compensate for the weight loss when high plane of feed was re-introduced. It can be concluded from the results that restricting 15 percent of feed from Cobb 500 standard feed intake had moderately affected broiler performance. Moreover, restricting 15percent of feed significantly reduced feed intake in broiler chicken.
- Full Text:
- Date Issued: 2017
- Authors: Velele, Siphelo
- Date: 2017
- Subjects: Broilers (Chickens) Poultry -- Breeding Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8888 , vital:33907
- Description: The study investigated the effects of quantitative feed restriction on growth performance, carcass characteristics, internal organs, breast muscle pH and meat colour in broiler chickens. A total of 90, un-sexed, day-old broiler chicks were procured from an accredited supplier and were used for the current trial. For the first 14 days, all birds were brooded in one house and subjected to a uniform day-to-day management. Water was supplied throughout the trial, whereas, feed was only supplied ad libitum between days 1-14 and 29-35 days in feed restricted birds. Feed phases included starter (1-14 days), grower (15-28) and finisher (29-35), respectively. On day 15, birds were randomly allocated to three treatments; each treatment was replicated three times with 10 birds per replicate. The first treatment (T1) group, which acted as control group, was ad libitum feeding for the whole trial duration (1-35 days). For treatments 2 (T2) and 3(T3), 85 percent and 70 percent of the Cobb 500 broiler feed intake standards were applied for a period of 14 days (days 15-28), respectively. Average daily feed intake (ADFI) was determined daily and then average body weight (ABW) was determined weekly. Feed conversion ratio and average daily weight gain was thus computed for each experimental unit (replicate). On day 35, broiler birds were electrically stunned and slaughtered by a sharp knife and then hung for complete bleeding. Data collected included slaughter, carcass, breast, thigh, wing, drumstick, feet, head, spleen, heart, gizzard, intestines (small & large) and liver weights. Breast muscle was further used for the determination of colour (L*, b* and a*), initial (pHi) and ultimate breast pH (pHu) measurements. Although, quantitative feed restriction (T2 & T3) significantly affected growth performance in weeks 3 and 4, birds submitted to T2 performed similar (P>0.05) to control in the final stage, whilst birds in T3 was the poorest (P<0.05). Furthermore, birds subjected to T2 showed no differences of edible carcass portions to the control, however, T3 group showed lower (P<0.05) slaughter and wing weights. Breast ultimate pH values of birds under T2 were similar to control, but birds in T3 had significantly higher (P<0.05) values. Birds under T2 had less (P<0.05) reddish breast meat colour than control at 45 minutes. At 24 hours post-mortem, birds in T3 had lower (P<0.05) lightness values and birds submitted to T2 had higher (P<0.05) yellowness values. Liver weight was significantly lower in birds under T3 and higher (P<0.05) gizzard weights were found in birds subjected to T2. Birds under T2 performed similar to control and were able to compensate for the weight loss when high plane of feed was re-introduced. It can be concluded from the results that restricting 15 percent of feed from Cobb 500 standard feed intake had moderately affected broiler performance. Moreover, restricting 15percent of feed significantly reduced feed intake in broiler chicken.
- Full Text:
- Date Issued: 2017
The effect of shade on the biological control of Salvinia molesta D.S. Mitchell [Salviniaceae] by the weevil, Cyrtobagous salviniae Calder and Sands [Curculionidae]
- Authors: Maseko, Zolile
- Date: 2017
- Subjects: Salvinia molesta , Aquatic weeds -- Biological control , Beetles , Insects as biological pest control agents
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4808 , vital:20726
- Description: Salvinia molesta, a floating aquatic weed, is a global menace in many water bodies and waterways. The weed disrupts the ecological balance wherever it invades and also has wide ranging economic and health impacts. Its impact has resulted in the need to control it, and while chemical and mechanical control are often ineffective, biological control by the weevil Cyrtobagous salviniae is largely successful. However, in many parts of the world, including South Africa, biological control of S. molesta has been less effective where the weed grows as an understory species. Shallow and shaded waters characteristically found at the margins of water bodies provide a refuge for S. molesta. Therefore, the aim of the study was to determine the effect of shade on the efficacy of biological control of S. molesta. Investigations into the problems associated with control in the shade were carried out in a greenhouse and in the field. In controlled greenhouse experiments, plants were grown at high and low nutrient levels in individual mesocosms, at three varying levels of shade, where half the mesocosms were inoculated with C. salviniae. Plants in high nutrient conditions were significantly more productive in terms of biomass accumulation, compared to those grown at low nutrient levels, in both the absence and presence of herbivory at all levels of shade tested. Plants grown in the shade and in high nutrient conditions had significantly higher quality compared to the ones exposed to full sun. Higher plant quality in the shade consequently resulted in accelerated fecundity for C. salviniae resulting in significantly higher weevil populations. Furthermore, less damage was recorded on plants in the shade, possibly due to the high nitrogen concentrations which may have deterred grazing by C. salviniae. However, in the absence of shading, plants were of lower quality and consequently sustained more damage from herbivores despite lower weevil populations. In contrast to the greenhouse, there were no differences in biomass recorded in the field at two nutrient levels and in the presence of herbivory for both shade and open sites. Nutrients added to high nutrient treatment quadrats diffused evenly across the water body resulting in uniform nutrient distribution, hence uniform plant biomass and carbon-nitrogen ratio. Despite the lack of statistical differences, more weevils were found in the full sun plots, while modest populations were recorded in the shade. Higher weevil populations consequently led to more damage in the sun, a situation that has been observed in most field sites in South Africa. The results therefore suggest that nutrients were pivotal in plant growth compared to light regimes (amount of PAR). Plant quality significantly influenced weevil populations and plant damage in both studies, demonstrating that plant nitrogen plays a crucial role in the plant- herbivore system. Furthermore, in both the greenhouse and field, despite lack of statistical differences, plants exposed to full sunlight suffered more damage than shade plants, pointing towards better control in the sun compared to the shade, suggesting that there is greater preference of sun-exposed plants for grazing by the weevils. The results from this study add to the growing body of literature that plant quality is a major factor in determining the success of aquatic weed biological control programmes.
- Full Text:
- Date Issued: 2017
- Authors: Maseko, Zolile
- Date: 2017
- Subjects: Salvinia molesta , Aquatic weeds -- Biological control , Beetles , Insects as biological pest control agents
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4808 , vital:20726
- Description: Salvinia molesta, a floating aquatic weed, is a global menace in many water bodies and waterways. The weed disrupts the ecological balance wherever it invades and also has wide ranging economic and health impacts. Its impact has resulted in the need to control it, and while chemical and mechanical control are often ineffective, biological control by the weevil Cyrtobagous salviniae is largely successful. However, in many parts of the world, including South Africa, biological control of S. molesta has been less effective where the weed grows as an understory species. Shallow and shaded waters characteristically found at the margins of water bodies provide a refuge for S. molesta. Therefore, the aim of the study was to determine the effect of shade on the efficacy of biological control of S. molesta. Investigations into the problems associated with control in the shade were carried out in a greenhouse and in the field. In controlled greenhouse experiments, plants were grown at high and low nutrient levels in individual mesocosms, at three varying levels of shade, where half the mesocosms were inoculated with C. salviniae. Plants in high nutrient conditions were significantly more productive in terms of biomass accumulation, compared to those grown at low nutrient levels, in both the absence and presence of herbivory at all levels of shade tested. Plants grown in the shade and in high nutrient conditions had significantly higher quality compared to the ones exposed to full sun. Higher plant quality in the shade consequently resulted in accelerated fecundity for C. salviniae resulting in significantly higher weevil populations. Furthermore, less damage was recorded on plants in the shade, possibly due to the high nitrogen concentrations which may have deterred grazing by C. salviniae. However, in the absence of shading, plants were of lower quality and consequently sustained more damage from herbivores despite lower weevil populations. In contrast to the greenhouse, there were no differences in biomass recorded in the field at two nutrient levels and in the presence of herbivory for both shade and open sites. Nutrients added to high nutrient treatment quadrats diffused evenly across the water body resulting in uniform nutrient distribution, hence uniform plant biomass and carbon-nitrogen ratio. Despite the lack of statistical differences, more weevils were found in the full sun plots, while modest populations were recorded in the shade. Higher weevil populations consequently led to more damage in the sun, a situation that has been observed in most field sites in South Africa. The results therefore suggest that nutrients were pivotal in plant growth compared to light regimes (amount of PAR). Plant quality significantly influenced weevil populations and plant damage in both studies, demonstrating that plant nitrogen plays a crucial role in the plant- herbivore system. Furthermore, in both the greenhouse and field, despite lack of statistical differences, plants exposed to full sunlight suffered more damage than shade plants, pointing towards better control in the sun compared to the shade, suggesting that there is greater preference of sun-exposed plants for grazing by the weevils. The results from this study add to the growing body of literature that plant quality is a major factor in determining the success of aquatic weed biological control programmes.
- Full Text:
- Date Issued: 2017
The effect of submersion in water and breathing modality (assisted breathing and apnea) on different stages of the information processing chain
- Authors: Goodenough, Luke Brian
- Date: 2017
- Subjects: Deep diving -- Physiological aspects , Scuba diving -- Physiological aspects , Apnea , Cognition -- Testing , Neurophysiology , Underwater breathing apparatus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7448 , vital:21261
- Description: Limited research has explored the impact of working underwater on the cognitive functioning of divers and even less has focused on the effect of breathing modality (assisted breathing and apnea) underwater. Research on the effect of submersion in water and apnea on cognitive performance is also very limited. As a result, the purpose of this study was to determine the effect of submersion in water and breathing modality on different stages of the information processing chain. This was achieved by testing participants in a laboratory setting under three conditions; on land, underwater with assisted breathing and underwater in apnea. Five different tests were used to determine which aspects of cognitive functioning were impaired in which condition. The recognition task result in the assisted breathing condition was significantly faster (p=0.04) but less accurate (p=0.01) than on land. The memory task was significantly (p=0.042) worse in terms of speed in the apnea condition compared to land, however accuracy was not affected. Performance in the visual detection task was impacted on in both underwater conditions compared to land with speed and accuracy being significantly worse (p<0.01) in the underwater conditions. These results indicate that simple tasks, (reaction time and tracking task) are not affected by condition whereas more complex tasks are. For tasks where an effect was found for only one condition, the effect was attributed to a specific aspect of that condition; either the breath hold or assisted breathing component of the condition. For tasks that were found to be affected in both underwater conditions, the effect was attributed to the actual submersion in water. The effect of the different conditions and the nature of the task they impact on should be considered for underwater work places as the general equipment used may impact on the quality of observations that are made.
- Full Text:
- Date Issued: 2017
- Authors: Goodenough, Luke Brian
- Date: 2017
- Subjects: Deep diving -- Physiological aspects , Scuba diving -- Physiological aspects , Apnea , Cognition -- Testing , Neurophysiology , Underwater breathing apparatus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7448 , vital:21261
- Description: Limited research has explored the impact of working underwater on the cognitive functioning of divers and even less has focused on the effect of breathing modality (assisted breathing and apnea) underwater. Research on the effect of submersion in water and apnea on cognitive performance is also very limited. As a result, the purpose of this study was to determine the effect of submersion in water and breathing modality on different stages of the information processing chain. This was achieved by testing participants in a laboratory setting under three conditions; on land, underwater with assisted breathing and underwater in apnea. Five different tests were used to determine which aspects of cognitive functioning were impaired in which condition. The recognition task result in the assisted breathing condition was significantly faster (p=0.04) but less accurate (p=0.01) than on land. The memory task was significantly (p=0.042) worse in terms of speed in the apnea condition compared to land, however accuracy was not affected. Performance in the visual detection task was impacted on in both underwater conditions compared to land with speed and accuracy being significantly worse (p<0.01) in the underwater conditions. These results indicate that simple tasks, (reaction time and tracking task) are not affected by condition whereas more complex tasks are. For tasks where an effect was found for only one condition, the effect was attributed to a specific aspect of that condition; either the breath hold or assisted breathing component of the condition. For tasks that were found to be affected in both underwater conditions, the effect was attributed to the actual submersion in water. The effect of the different conditions and the nature of the task they impact on should be considered for underwater work places as the general equipment used may impact on the quality of observations that are made.
- Full Text:
- Date Issued: 2017
The effect of total standing duration during sit-stand regimes on cognitive performance, rating of perceived exertion and heart rate frequency
- Authors: Berndt, Ethan
- Date: 2017
- Subjects: Standing position , Sedentary behavior , Work environment , Employee health promotion , Office furniture -- Design , Industrial hygiene , Employees -- Health risk assessment , Human engineering
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7433 , vital:21260
- Description: Although there may be numerous health benefits of sit-stand workstations, the effects of sedentary or non-sedentary work configurations on cognitive performance and executive function remain unclear (Bantoft et al., 2016). It is essential to determine any performance effects of these different work configurations; as improvements in the workplace, working posture and discomfort need to be justified in terms of improvements (or no deterioration) in work performance (Liao and Drury, 2000). The aim of the current research was to investigate the effect of two sit-stand regimes differing in total standing duration, on cognitive task performance, physiological responses and subjective ratings of perceived exertion. This laboratory based investigation incorporated a repeated measures design, where a test battery was utilized. Three experimental conditions were tested during three separate testing sessions by 30 participants. Condition 2 (15 minutes standing, followed by 45 minutes seated) and Condition 3 (15 minutes seated, followed by 15 minutes standing, followed by 15 minutes seated, followed by 15 minutes standing) were compared to each other and Condition 1 (60 minutes seated). The findings of this study show that even though the two different sit-stand regimes did not result in a significant impact on cognitive task performance, an immediate postural effect for psychomotor response time and a delayed postural effect for working memory were found. The participants perceived Condition 3 as the most physically exerting condition. Heart rate frequency was not significantly different between the conditions, but the immediate seated posture had a significantly lower heart rate frequency compared to the standing posture; indicating that being seated elicited lower energy expenditure compared to standing. Heart rate frequency while standing had a greater degree of variation compared to being seated. Taking the findings of this study into account, it is recommended that: one should be seated while performing this type of working memory task; that one should be standing while performing this type of psychomotor task; that the recommendation that implementing standing at work can be used as a blanket strategy to increase energy expenditure in all individuals needs to be explored further and that individual differences may impact energy expenditure.
- Full Text:
- Date Issued: 2017
- Authors: Berndt, Ethan
- Date: 2017
- Subjects: Standing position , Sedentary behavior , Work environment , Employee health promotion , Office furniture -- Design , Industrial hygiene , Employees -- Health risk assessment , Human engineering
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7433 , vital:21260
- Description: Although there may be numerous health benefits of sit-stand workstations, the effects of sedentary or non-sedentary work configurations on cognitive performance and executive function remain unclear (Bantoft et al., 2016). It is essential to determine any performance effects of these different work configurations; as improvements in the workplace, working posture and discomfort need to be justified in terms of improvements (or no deterioration) in work performance (Liao and Drury, 2000). The aim of the current research was to investigate the effect of two sit-stand regimes differing in total standing duration, on cognitive task performance, physiological responses and subjective ratings of perceived exertion. This laboratory based investigation incorporated a repeated measures design, where a test battery was utilized. Three experimental conditions were tested during three separate testing sessions by 30 participants. Condition 2 (15 minutes standing, followed by 45 minutes seated) and Condition 3 (15 minutes seated, followed by 15 minutes standing, followed by 15 minutes seated, followed by 15 minutes standing) were compared to each other and Condition 1 (60 minutes seated). The findings of this study show that even though the two different sit-stand regimes did not result in a significant impact on cognitive task performance, an immediate postural effect for psychomotor response time and a delayed postural effect for working memory were found. The participants perceived Condition 3 as the most physically exerting condition. Heart rate frequency was not significantly different between the conditions, but the immediate seated posture had a significantly lower heart rate frequency compared to the standing posture; indicating that being seated elicited lower energy expenditure compared to standing. Heart rate frequency while standing had a greater degree of variation compared to being seated. Taking the findings of this study into account, it is recommended that: one should be seated while performing this type of working memory task; that one should be standing while performing this type of psychomotor task; that the recommendation that implementing standing at work can be used as a blanket strategy to increase energy expenditure in all individuals needs to be explored further and that individual differences may impact energy expenditure.
- Full Text:
- Date Issued: 2017
The effectiveness of health and safety service providers' relative to construction
- Authors: Ayesu-Koranteng, Emma
- Date: 2017
- Subjects: Construction industry -- Health aspects -- South Africa Industrial safety -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/15149 , vital:28151
- Description: The construction industry (CI) is well known to be one of the most dangerous industries in South Africa (SA) due to the complex nature of construction activities, advancement in technologies and an aging workforce, emphasising the need for training. Over the past two decades, the industry has come under the spotlight regarding Health and Safety (H&S). The Occupational Health and Safety (OH&S) Act 85 of 1993 and Construction Regulations (CR) 2014 as amended are the statutes that govern the H&S in the construction workplace. These statutes aim to provide minimum guidelines by which all operating in the industry should abide by in order to ensure the safety of all persons at work. A fundamental aspect of the OH&S Act and CR is for construction employers to assess occupational hazards and conduct risk assessments with remedies to mitigate or prevent such risks. Furthermore, employers are compelled by law to ensure that employees are made aware of the risks at the induction stage, in addition to preventative measures associated with their work activities. Therefore, training forms the structure by which H&S in the workplace can be improved. Training in itself is not enough if it is not based on the employees’ needs as assessed. Training needs to be relevant and effective if it is to have a significant effect in the prevention and possible reduction in the number of occupational injuries and fatalities in the CI. A question that led to the basis of this research was why there were such poor H&S practices in the CI when the statutes clearly require the importance of training. This research is aimed at establishing the effectiveness of service providers relative to construction. Service providers offer services such as training, auditing, SHEQ management, and other H&S related matters. Of fundamental importance is that training has a direct or indirect influence on the health and safety (H&S) of employees in the workplace. Thus, this research aims to determine the effectiveness of training offered by these service providers relative to construction. The researcher utilised the quantitative data collection method to collect primary data from a sample surveyed through a questionnaire, whilst collecting secondary data from books, the Internet, professional journals, and articles. The sampled population consisted of service providers, health and safety practitioners, construction managers, supervisors, and workers, all from the Nelson Mandela Bay Municipal Area. The data was analysed quantitatively using the Statistical Package for Social Sciences (SPSS), ANOVA and the one-sample t-test. The literature reviewed and findings of this quantitative research amongst construction personal such as top, senior, middle management (TSMM), and general workers and labourers (GWL) in the Nelson Mandela Bay Municipal area formed the basis of this study. The study reveals that training offered by service providers was indirectly unrelated to construction. Furthermore, the study also showed that management concurred that there was a strong belief that language did not influence their ability to understand the contents of the training, which is mainly provided in English. The group believed that training from service providers were at the correct level. Alternatively, GWL were of the belief that language influenced their ability to understand the training received. The study also indicated that procurement of these service providers were not based on their skills, knowledge and background in construction. This may be attributed to the fact that management are more advanced in terms of education than GWL. Lastly, the study revealed that a significant number of Safety, Health and Environment (SHE) officers are in the process of registering with the South African Council for the Project and Construction Management Professions (SACPCMP), the professional body responsible for the registration of Construction Health and Safety (CH&S) professions. This study will conclude with findings, conclusions, and recommendations that will be valuable to construction companies relative to the services of service providers.
- Full Text:
- Date Issued: 2017
- Authors: Ayesu-Koranteng, Emma
- Date: 2017
- Subjects: Construction industry -- Health aspects -- South Africa Industrial safety -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/15149 , vital:28151
- Description: The construction industry (CI) is well known to be one of the most dangerous industries in South Africa (SA) due to the complex nature of construction activities, advancement in technologies and an aging workforce, emphasising the need for training. Over the past two decades, the industry has come under the spotlight regarding Health and Safety (H&S). The Occupational Health and Safety (OH&S) Act 85 of 1993 and Construction Regulations (CR) 2014 as amended are the statutes that govern the H&S in the construction workplace. These statutes aim to provide minimum guidelines by which all operating in the industry should abide by in order to ensure the safety of all persons at work. A fundamental aspect of the OH&S Act and CR is for construction employers to assess occupational hazards and conduct risk assessments with remedies to mitigate or prevent such risks. Furthermore, employers are compelled by law to ensure that employees are made aware of the risks at the induction stage, in addition to preventative measures associated with their work activities. Therefore, training forms the structure by which H&S in the workplace can be improved. Training in itself is not enough if it is not based on the employees’ needs as assessed. Training needs to be relevant and effective if it is to have a significant effect in the prevention and possible reduction in the number of occupational injuries and fatalities in the CI. A question that led to the basis of this research was why there were such poor H&S practices in the CI when the statutes clearly require the importance of training. This research is aimed at establishing the effectiveness of service providers relative to construction. Service providers offer services such as training, auditing, SHEQ management, and other H&S related matters. Of fundamental importance is that training has a direct or indirect influence on the health and safety (H&S) of employees in the workplace. Thus, this research aims to determine the effectiveness of training offered by these service providers relative to construction. The researcher utilised the quantitative data collection method to collect primary data from a sample surveyed through a questionnaire, whilst collecting secondary data from books, the Internet, professional journals, and articles. The sampled population consisted of service providers, health and safety practitioners, construction managers, supervisors, and workers, all from the Nelson Mandela Bay Municipal Area. The data was analysed quantitatively using the Statistical Package for Social Sciences (SPSS), ANOVA and the one-sample t-test. The literature reviewed and findings of this quantitative research amongst construction personal such as top, senior, middle management (TSMM), and general workers and labourers (GWL) in the Nelson Mandela Bay Municipal area formed the basis of this study. The study reveals that training offered by service providers was indirectly unrelated to construction. Furthermore, the study also showed that management concurred that there was a strong belief that language did not influence their ability to understand the contents of the training, which is mainly provided in English. The group believed that training from service providers were at the correct level. Alternatively, GWL were of the belief that language influenced their ability to understand the training received. The study also indicated that procurement of these service providers were not based on their skills, knowledge and background in construction. This may be attributed to the fact that management are more advanced in terms of education than GWL. Lastly, the study revealed that a significant number of Safety, Health and Environment (SHE) officers are in the process of registering with the South African Council for the Project and Construction Management Professions (SACPCMP), the professional body responsible for the registration of Construction Health and Safety (CH&S) professions. This study will conclude with findings, conclusions, and recommendations that will be valuable to construction companies relative to the services of service providers.
- Full Text:
- Date Issued: 2017
The effects of a lion (Panthera Leo) re-introduction on a resident cheetah (Acinonyx Jubatus) population In Mountain Zebra National Park, Eastern Cape, South Africa
- Authors: Van de Vyver, Daniel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7420 , vital:21259
- Description: The global decline of large (> 10 kg) carnivores has resulted in a variety of conservation measures being put into practice to prevent extinctions. The establishment of predator-proof fences around protected areas has been a successful tool for reducing human-predator conflict. Furthermore, the re-introduction of large carnivores into small (< 1 000 km²), enclosed reserves has aided in the conservation of many species. Cheetahs (Acinonyx jubatus) and lions (Panthera leo) have benefitted from such re-introductions. The re-introduction of cheetahs before lions into the Mountain Zebra National Park (MZNP) in the Eastern Cape Province of South Africa provided a unique opportunity to study the effects of lions on an already established cheetah population. Spatial data were downloaded remotely from GPS collared individuals (n=4) and cheetah kill data were collected using the GPS cluster method before (2012-2013) and after (2013-2014) the lion (n=3) re-introduction. The same methods were used for lion kill data collection once they had been re-introduced. In general, cheetah home range size did not change after the lion re-introduction. Cheetahs selected areas with a combination of open and closed vegetation covers, while lions selected either open or closed areas of vegetation covers. In addition, as vegetation cover became thicker, the presence of cheetahs decreased. The cheetahs preyed upon seven species before and 11 species after the lion re-introduction. Medium sized prey comprised the bulk of the cheetah diet with kudu (Tragelaphus strepsiceros) and springbok (Antidorcas marsupialis) being the preferred species both before and after the lion re-introduction. The lion diets consisted of medium to large sized prey, with the male lions selecting eland (Tragelaphus oryx) and buffalo (Syncerus caffer) and the lioness selecting red hartebeest (Alcelaphus buselaphus). The cheetahs had no significant dietary overlap with the lions and there was only one record of kleptoparasitism. The results of my study indicate that cheetahs are able to co-exist with lions when lions are at low densities in an enclosed reserve. The cheetahs did not experience landscape-level displacement because they made fine-scale adjustments to avoid lions within their environment. This adaptability may have important management implications for future re-introductions of cheetahs into enclosed game reserves.
- Full Text:
- Date Issued: 2017
- Authors: Van de Vyver, Daniel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7420 , vital:21259
- Description: The global decline of large (> 10 kg) carnivores has resulted in a variety of conservation measures being put into practice to prevent extinctions. The establishment of predator-proof fences around protected areas has been a successful tool for reducing human-predator conflict. Furthermore, the re-introduction of large carnivores into small (< 1 000 km²), enclosed reserves has aided in the conservation of many species. Cheetahs (Acinonyx jubatus) and lions (Panthera leo) have benefitted from such re-introductions. The re-introduction of cheetahs before lions into the Mountain Zebra National Park (MZNP) in the Eastern Cape Province of South Africa provided a unique opportunity to study the effects of lions on an already established cheetah population. Spatial data were downloaded remotely from GPS collared individuals (n=4) and cheetah kill data were collected using the GPS cluster method before (2012-2013) and after (2013-2014) the lion (n=3) re-introduction. The same methods were used for lion kill data collection once they had been re-introduced. In general, cheetah home range size did not change after the lion re-introduction. Cheetahs selected areas with a combination of open and closed vegetation covers, while lions selected either open or closed areas of vegetation covers. In addition, as vegetation cover became thicker, the presence of cheetahs decreased. The cheetahs preyed upon seven species before and 11 species after the lion re-introduction. Medium sized prey comprised the bulk of the cheetah diet with kudu (Tragelaphus strepsiceros) and springbok (Antidorcas marsupialis) being the preferred species both before and after the lion re-introduction. The lion diets consisted of medium to large sized prey, with the male lions selecting eland (Tragelaphus oryx) and buffalo (Syncerus caffer) and the lioness selecting red hartebeest (Alcelaphus buselaphus). The cheetahs had no significant dietary overlap with the lions and there was only one record of kleptoparasitism. The results of my study indicate that cheetahs are able to co-exist with lions when lions are at low densities in an enclosed reserve. The cheetahs did not experience landscape-level displacement because they made fine-scale adjustments to avoid lions within their environment. This adaptability may have important management implications for future re-introductions of cheetahs into enclosed game reserves.
- Full Text:
- Date Issued: 2017
The effects of the type of rest breaks on return-to-task performance in semi-automated tasks with varying complexities
- Authors: Hoyi, Zandile
- Date: 2017
- Subjects: Rest periods , Rest periods -- Physiological effect , Human-robot interaction , Aeronautics -- Human factors , Human engineering , Drowsiness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44490 , vital:25412
- Description: Automation in the aviation industry is acknowledged as a useful tool in reducing pilot workload (Hoh, Smith & Hinton, 1987; Beringer & Harris Jr., 1999). Typically, the role of the pilot (operator) shifts from active participation in a process to a task of monitoring the system with the resumption of control should the automation ‘fail’ (Byrne & Parasuraman, 1996). Unfortunately, the skills necessary to do so would likely degrade from non-use, during this process (Landry, 2012). This project investigates the “attentional demands” for the human operator during interaction with semi-automated operations of the flight. According to Dr Abbott (1996), FAA human factors specialist, one of the problems causing disharmony between crews and their automated systems is the incorrect upset recovery, owing to the human being out-of-the-loop (OOTL) from the system. Recovery, or rather return to task, is the ability of the pilot to loop back into control, once situational awareness has been decreased due to lack of alertness and a decrease in arousal. Different types of rest tasks are commonly prescribed fatigue countermeasures in the industrial setting and have been showed to elicit beneficial effects on prolonged human performance. Understanding the effects of different rest break activity and time out-of-the-loop during semi-automated flying on return to task performance has been adequately studied, thus highlighting its importance in the context of flight safety. The present study requested participants to perform a tracking task in a laboratory where they changed from activity (30 minutes) to a break (2 vs. 30 minutes) and back to the activity (20 minutes). The task varied in the complexity of the activity (pure tracking vs. tracking plus memory plus rule-based decision making), the type of break (passive rest vs. actively supervising) and the duration of the break (2 minutes vs. 30 minutes). Performance was measured as effective response time in the tracking task and number of correct responses to secondary cognitive tasks. Physiological measures included heart rate (HR), heart rate variability (HRV- time and frequency-domain), eye blink frequency and duration. The Karolinska Sleepiness Scale was used as a subjective measure. With regards to the most appropriate rest break tasks, the study concluded that active, administrative tasks, which allowed the operator to maintain some form of situational awareness by monitoring the automated system, achieved favourable effects of being more alert than the passive rest break of being disengaged from the system. In terms of the most appropriate rest break durations, the shorter duration of being out-of-the-loop from controlling the system proved to be more advantageous than the longer out-of-the-loop duration. In looking at the workload levels of arousal, the results suggest that the higher workload level is better at maintaining the alertness of operators. This study functions as a foundational framework for future investigations around the topic of human-automation interaction, looking specifically at return-to-task performance.
- Full Text:
- Date Issued: 2017
- Authors: Hoyi, Zandile
- Date: 2017
- Subjects: Rest periods , Rest periods -- Physiological effect , Human-robot interaction , Aeronautics -- Human factors , Human engineering , Drowsiness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44490 , vital:25412
- Description: Automation in the aviation industry is acknowledged as a useful tool in reducing pilot workload (Hoh, Smith & Hinton, 1987; Beringer & Harris Jr., 1999). Typically, the role of the pilot (operator) shifts from active participation in a process to a task of monitoring the system with the resumption of control should the automation ‘fail’ (Byrne & Parasuraman, 1996). Unfortunately, the skills necessary to do so would likely degrade from non-use, during this process (Landry, 2012). This project investigates the “attentional demands” for the human operator during interaction with semi-automated operations of the flight. According to Dr Abbott (1996), FAA human factors specialist, one of the problems causing disharmony between crews and their automated systems is the incorrect upset recovery, owing to the human being out-of-the-loop (OOTL) from the system. Recovery, or rather return to task, is the ability of the pilot to loop back into control, once situational awareness has been decreased due to lack of alertness and a decrease in arousal. Different types of rest tasks are commonly prescribed fatigue countermeasures in the industrial setting and have been showed to elicit beneficial effects on prolonged human performance. Understanding the effects of different rest break activity and time out-of-the-loop during semi-automated flying on return to task performance has been adequately studied, thus highlighting its importance in the context of flight safety. The present study requested participants to perform a tracking task in a laboratory where they changed from activity (30 minutes) to a break (2 vs. 30 minutes) and back to the activity (20 minutes). The task varied in the complexity of the activity (pure tracking vs. tracking plus memory plus rule-based decision making), the type of break (passive rest vs. actively supervising) and the duration of the break (2 minutes vs. 30 minutes). Performance was measured as effective response time in the tracking task and number of correct responses to secondary cognitive tasks. Physiological measures included heart rate (HR), heart rate variability (HRV- time and frequency-domain), eye blink frequency and duration. The Karolinska Sleepiness Scale was used as a subjective measure. With regards to the most appropriate rest break tasks, the study concluded that active, administrative tasks, which allowed the operator to maintain some form of situational awareness by monitoring the automated system, achieved favourable effects of being more alert than the passive rest break of being disengaged from the system. In terms of the most appropriate rest break durations, the shorter duration of being out-of-the-loop from controlling the system proved to be more advantageous than the longer out-of-the-loop duration. In looking at the workload levels of arousal, the results suggest that the higher workload level is better at maintaining the alertness of operators. This study functions as a foundational framework for future investigations around the topic of human-automation interaction, looking specifically at return-to-task performance.
- Full Text:
- Date Issued: 2017
The growth and recovery of mangroves at three South African study sites
- Authors: Mbense, Sinegugu
- Date: 2017
- Subjects: Mangrove forests -- South Africa Mangrove ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11931 , vital:27008
- Description: Mangroves in South Africa are prone to anthropogenic pressures such as browsing and trampling by livestock and by natural disturbances such as drought and floods. These mangroves exist at one of the most southerly limits in the world providing a unique opportunity to study recovery and resilience to change. This study used long term data at three South African study sites located in the subtropical (St Lucia Estuary) and warm temperate regions (Nxaxo and Kobonqaba estuaries) to compare mangrove growth rate, population structure and responses to disturbance. The first objective was investigated at St Lucia Estuary where site specific or microhabitat differences were measured to assess the influence of these on mangrove growth and population structure. It was suggested that site - specific variability would ensure mangrove survival and analysis showed that seedlings were present at different sites in different years. There was always some recruitment but often little survival to the next size class. Over time seedling numbers were quite variable and self – thinning of adults was evident. The second objective was to identify the environmental factors influencing population density and growth. Results showed that sediment moisture and salinity influenced seedling and adult density due to fluctuations in estuary water level. Mangrove growth rates for Avicennia marina in terms of height was faster (40 – 75 cm yr-1 ) at Site 1 where conditions were waterlogged and moderately saline and slower (5 – 25 cm yr1 ) in dry and hypersaline conditions at Site 4. Overall mangroves at St Lucia have shown persistence through drought and fluctuations in environmental conditions however resilience may be hindered at sites that are subjected to partially flooding and prolonged waterlogging. The second site was Nxaxo Estuary in the Eastern Cape where cattle exclusion plots (nonbrowsed) and control plots (browsed) were used to assess the recovery of A. marina trees from cattle browsing. Trees in the browsed plots showed no vertical growth while trees in the non-browsed plots grew significantly faster (5.4 ± 0.5 cm yr-1). When cattle were prevented from entering the mangrove area, the trees recovered fairly quickly and within 3 years growth was similar in both the non – browsed (17.9 ± 3.2 cm yr -1) and browsed plots (18 ± 1.6 cm yr -1). Lastly, mangrove recovery was investigated at Kobonqaba Estuary where long-term closure of the mouth to the sea resulted in high water levels, inundation of pneumatophores and die-back of the majority of the mangroves. This study measured the recovery of the mangroves by assessing changes in vegetation cover and sediment characteristics along transects. High initial porewater nutrient concentrations promoted salt marsh growth and plants increased average cover from 0% in 2011 to 18.9% (2013) and 50% in 2015. The total number of A. marina individuals increased from only seven to 27 individuals over four years. Salt marsh competition and facilitation will likely influence mangrove recovery in the future. Overall it was concluded that when a short term pressure (cattle browsing) is alleviated, mangrove forests even at warm temperate sites are able to recovery rapidly by increasing growth and seedling establishment. However, mangroves in the subtropical sites show more resilience and recovery potential to long term pressures such as fluctuating environmental conditions because of faster growth rates.
- Full Text:
- Date Issued: 2017
- Authors: Mbense, Sinegugu
- Date: 2017
- Subjects: Mangrove forests -- South Africa Mangrove ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/11931 , vital:27008
- Description: Mangroves in South Africa are prone to anthropogenic pressures such as browsing and trampling by livestock and by natural disturbances such as drought and floods. These mangroves exist at one of the most southerly limits in the world providing a unique opportunity to study recovery and resilience to change. This study used long term data at three South African study sites located in the subtropical (St Lucia Estuary) and warm temperate regions (Nxaxo and Kobonqaba estuaries) to compare mangrove growth rate, population structure and responses to disturbance. The first objective was investigated at St Lucia Estuary where site specific or microhabitat differences were measured to assess the influence of these on mangrove growth and population structure. It was suggested that site - specific variability would ensure mangrove survival and analysis showed that seedlings were present at different sites in different years. There was always some recruitment but often little survival to the next size class. Over time seedling numbers were quite variable and self – thinning of adults was evident. The second objective was to identify the environmental factors influencing population density and growth. Results showed that sediment moisture and salinity influenced seedling and adult density due to fluctuations in estuary water level. Mangrove growth rates for Avicennia marina in terms of height was faster (40 – 75 cm yr-1 ) at Site 1 where conditions were waterlogged and moderately saline and slower (5 – 25 cm yr1 ) in dry and hypersaline conditions at Site 4. Overall mangroves at St Lucia have shown persistence through drought and fluctuations in environmental conditions however resilience may be hindered at sites that are subjected to partially flooding and prolonged waterlogging. The second site was Nxaxo Estuary in the Eastern Cape where cattle exclusion plots (nonbrowsed) and control plots (browsed) were used to assess the recovery of A. marina trees from cattle browsing. Trees in the browsed plots showed no vertical growth while trees in the non-browsed plots grew significantly faster (5.4 ± 0.5 cm yr-1). When cattle were prevented from entering the mangrove area, the trees recovered fairly quickly and within 3 years growth was similar in both the non – browsed (17.9 ± 3.2 cm yr -1) and browsed plots (18 ± 1.6 cm yr -1). Lastly, mangrove recovery was investigated at Kobonqaba Estuary where long-term closure of the mouth to the sea resulted in high water levels, inundation of pneumatophores and die-back of the majority of the mangroves. This study measured the recovery of the mangroves by assessing changes in vegetation cover and sediment characteristics along transects. High initial porewater nutrient concentrations promoted salt marsh growth and plants increased average cover from 0% in 2011 to 18.9% (2013) and 50% in 2015. The total number of A. marina individuals increased from only seven to 27 individuals over four years. Salt marsh competition and facilitation will likely influence mangrove recovery in the future. Overall it was concluded that when a short term pressure (cattle browsing) is alleviated, mangrove forests even at warm temperate sites are able to recovery rapidly by increasing growth and seedling establishment. However, mangroves in the subtropical sites show more resilience and recovery potential to long term pressures such as fluctuating environmental conditions because of faster growth rates.
- Full Text:
- Date Issued: 2017
The identification of key vulnerability components within Solomon Islands coastal communities
- Authors: Malherbe, Willem Stefanus
- Date: 2017
- Subjects: Solomon Islands -- Environmental conditions , Coastal ecology -- Solomon Islands , Island ecology -- Solomon Islands , Climatic changes -- Solomon Islands , Sociology, Urban -- Solomon Islands , Sociology, Rural -- Solomon Islands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21184 , http://hdl.handle.net/10962/6827
- Description: The impacts of climate change are disproportionally felt across the planet, with small island developing states some of the countries most at risk. Furthermore, climate change may compound existing problems such as over harvested resources, leading to knock-on effects on national economies. Both direct and indirect stressors may impact communities differently based on their level of exposure to stressors, their intrinsic sensitivity to these stressors, and their ability to adapt to stressors. This study aims to answer the primary research question: Why are some communities more vulnerable than others? A vulnerability assessment is used to identify both vulnerable and non-vulnerable attributes of Solomon Islands’ communities. Surveys comprised a comprehensive questionnaire to draw inference on each vulnerability category; sensitivity, exposure and adaptive capacity, along with their various components and subcomponents. An analysis of household and community livelihood strategies was conducted to compliment vulnerability scores and provide a deeper understanding of livelihood practises. As is expected of small island states, exposure presents the biggest threat to coastal communities. Within this category, environmental changes and personal exposure from shoreline erosion and safety at sea provide evidence of high vulnerability. Within the sensitivity category, the cultural importance of fishing, as well as attachment to place and fishing, renders communities more vulnerable. Simultaneously, local ecological knowledge and economic dependence on resources other than fishing proved to be resilient attributes by decreasing vulnerability. Low vulnerability scores for the adaptive capacity category were achieved by communities where physical capital, such as community infrastructure, was evident. A lack of both institutional support and bridging of social capital were attributes which contributed to community vulnerability. This study has identified key attributes that have both positive and negative effects on the vulnerability of Solomon Islands communities. Having done this, I have also attempted to determine the drivers that render some attributes more vulnerable than others. It is acknowledged that the drivers of all key attributes of vulnerability is required to determine areas where adaptation plans will be most effective. Importantly, drivers of high vulnerability should not be considered as the primary focus of adaptation planning, but also the drivers of low vulnerability, such as community cohesion, which provide resilience within communities.
- Full Text:
- Date Issued: 2017
- Authors: Malherbe, Willem Stefanus
- Date: 2017
- Subjects: Solomon Islands -- Environmental conditions , Coastal ecology -- Solomon Islands , Island ecology -- Solomon Islands , Climatic changes -- Solomon Islands , Sociology, Urban -- Solomon Islands , Sociology, Rural -- Solomon Islands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21184 , http://hdl.handle.net/10962/6827
- Description: The impacts of climate change are disproportionally felt across the planet, with small island developing states some of the countries most at risk. Furthermore, climate change may compound existing problems such as over harvested resources, leading to knock-on effects on national economies. Both direct and indirect stressors may impact communities differently based on their level of exposure to stressors, their intrinsic sensitivity to these stressors, and their ability to adapt to stressors. This study aims to answer the primary research question: Why are some communities more vulnerable than others? A vulnerability assessment is used to identify both vulnerable and non-vulnerable attributes of Solomon Islands’ communities. Surveys comprised a comprehensive questionnaire to draw inference on each vulnerability category; sensitivity, exposure and adaptive capacity, along with their various components and subcomponents. An analysis of household and community livelihood strategies was conducted to compliment vulnerability scores and provide a deeper understanding of livelihood practises. As is expected of small island states, exposure presents the biggest threat to coastal communities. Within this category, environmental changes and personal exposure from shoreline erosion and safety at sea provide evidence of high vulnerability. Within the sensitivity category, the cultural importance of fishing, as well as attachment to place and fishing, renders communities more vulnerable. Simultaneously, local ecological knowledge and economic dependence on resources other than fishing proved to be resilient attributes by decreasing vulnerability. Low vulnerability scores for the adaptive capacity category were achieved by communities where physical capital, such as community infrastructure, was evident. A lack of both institutional support and bridging of social capital were attributes which contributed to community vulnerability. This study has identified key attributes that have both positive and negative effects on the vulnerability of Solomon Islands communities. Having done this, I have also attempted to determine the drivers that render some attributes more vulnerable than others. It is acknowledged that the drivers of all key attributes of vulnerability is required to determine areas where adaptation plans will be most effective. Importantly, drivers of high vulnerability should not be considered as the primary focus of adaptation planning, but also the drivers of low vulnerability, such as community cohesion, which provide resilience within communities.
- Full Text:
- Date Issued: 2017
The impact of open-plan office design on the productivity of City of Cape Town employees
- Authors: Nghona, Ziyanda
- Date: 2017
- Subjects: Labor productivity -- South Africa -- Cape Town , Performance -- Measurement Interior architecture Space (Architecture)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48080 , vital:40469
- Description: Comprehensive research studies on identifying the positive and negative impact of open-plan office designs on employees’ work productivity were long initiated and still continually debated in developed nations such as USA, Canada and UK. As a result, the researcher decided to undertake research in order to determine whether the salient negative and positive factors, identified in international literature about open-plan office designs, are applicable in the South African context. The aim was not to reduce the accrued positive and negative factors, emanating from open-plan offices, but rather to identify and determine how they impact employees work productivity. The study had the following objectives, namely: (1) to investigate the employees satisfaction level with the physical environment as a result of working within the open-plan office design layout; (2) to determine the employees' stress levels as a result of working within the open-plan office design layout; (3) to determine the team members or co-workers satisfaction level as a result of working within the open-plan office design layout; and lastly, (4) to determine the positive and negative impact of the open-plan office design layout on employees work productivity. The data gathering approaches included survey self-administered questionnaires to the Built Environment related employees working within the open-plan offices of the City of Cape Town Municipality within the CBD area. The sample consisted the following departments: Facilities Management; Sports & Recreation; Human Settlement and Solid Waste. A purposeful random sampling method was followed to identify participants for the study. Concerning the first objective, it was clear from the analysis that employees are unsatisfied with the physical environment of the open-plan office design layout. Their dissatisfaction pointed to several issues such as less control or flexibility to rearrange or reorganise their office furniture to meet their work needs; limited or no available quiet and undisturbed time. As a result, it was not surprising that employees in open-plan office experience high job-related stress levels. However, in a positive light, concerning the team members or co-workers relations on working within open-plan offices, it was reported that employees are satisfied reporting high exchange of job related information and thus learning from each other. Lastly and more importantly, in terms of the overall aim of this study, the study revealed that the employees’ work productivity is affected negatively as a result of the open-plan office design in the City of Cape Town. Initially identification of how open-plan offices impact employees work productivity is the critical first-step in an attempt to reduce the negative and increase the positive impact and this constitutes the contribution of this study. However, this study was limited in that it only requested respondents to agree or disagree with the relationships among measurable variables that already exist in previous studies done in developed countries. The study survey was also limited by the selected sample within the City of Cape Town Municipality public offices. As a result, the study only sampled five Built Environment related openplan offices and thus the generalisability of the findings is limited. Further studies with large and wider survey can thus benefit this study topic in developing economies like South Africa.
- Full Text:
- Date Issued: 2017
- Authors: Nghona, Ziyanda
- Date: 2017
- Subjects: Labor productivity -- South Africa -- Cape Town , Performance -- Measurement Interior architecture Space (Architecture)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/48080 , vital:40469
- Description: Comprehensive research studies on identifying the positive and negative impact of open-plan office designs on employees’ work productivity were long initiated and still continually debated in developed nations such as USA, Canada and UK. As a result, the researcher decided to undertake research in order to determine whether the salient negative and positive factors, identified in international literature about open-plan office designs, are applicable in the South African context. The aim was not to reduce the accrued positive and negative factors, emanating from open-plan offices, but rather to identify and determine how they impact employees work productivity. The study had the following objectives, namely: (1) to investigate the employees satisfaction level with the physical environment as a result of working within the open-plan office design layout; (2) to determine the employees' stress levels as a result of working within the open-plan office design layout; (3) to determine the team members or co-workers satisfaction level as a result of working within the open-plan office design layout; and lastly, (4) to determine the positive and negative impact of the open-plan office design layout on employees work productivity. The data gathering approaches included survey self-administered questionnaires to the Built Environment related employees working within the open-plan offices of the City of Cape Town Municipality within the CBD area. The sample consisted the following departments: Facilities Management; Sports & Recreation; Human Settlement and Solid Waste. A purposeful random sampling method was followed to identify participants for the study. Concerning the first objective, it was clear from the analysis that employees are unsatisfied with the physical environment of the open-plan office design layout. Their dissatisfaction pointed to several issues such as less control or flexibility to rearrange or reorganise their office furniture to meet their work needs; limited or no available quiet and undisturbed time. As a result, it was not surprising that employees in open-plan office experience high job-related stress levels. However, in a positive light, concerning the team members or co-workers relations on working within open-plan offices, it was reported that employees are satisfied reporting high exchange of job related information and thus learning from each other. Lastly and more importantly, in terms of the overall aim of this study, the study revealed that the employees’ work productivity is affected negatively as a result of the open-plan office design in the City of Cape Town. Initially identification of how open-plan offices impact employees work productivity is the critical first-step in an attempt to reduce the negative and increase the positive impact and this constitutes the contribution of this study. However, this study was limited in that it only requested respondents to agree or disagree with the relationships among measurable variables that already exist in previous studies done in developed countries. The study survey was also limited by the selected sample within the City of Cape Town Municipality public offices. As a result, the study only sampled five Built Environment related openplan offices and thus the generalisability of the findings is limited. Further studies with large and wider survey can thus benefit this study topic in developing economies like South Africa.
- Full Text:
- Date Issued: 2017
The impact of rangeland degradation on vegetation cover and soil quality in semi-arid communal rangelands of the Eastern Cape province, South Africa
- Authors: Maziko, Yonela
- Date: 2017
- Subjects: Communal rangelands -- South Africa -- Eastern Cape Land degradation -- South Africa -- Eastern Cape Vegetation management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/15056 , vital:40159
- Description: This study was conducted to investigate the influence of degradation on vegetation and soil quality in two semi-arid rangelands in the Eastern Cape Province of South Africa. The study was undertaken in Kwezana and Esigingqini communal areas that showed signs id degradation. The assessment incorporated the soil and grass layer in different degradation levels, namely nondegraded, slightly degraded, moderately and severely degraded. The non-degraded has a sufficient amount of vegetation cover and species composition. The slightly degraded site consists of a few visible bare patches. The moderately degraded areas showed signs of active sheet erosion such as pedestals and a higher percentage of bare areas and the severely degraded area is characterized by dongas and gullies, with vast areas that have no ground cover or top fertile soil layer. Using a step point method, herbaceous species composition was determined within three transects from three plots 100 m x 40 m in each degradation level. The aboveground phytomass production was determined by harvesting herbaceous species within four randomly placed 0.25 m2 quadrats in each transect. Bare ground was determined by counting and recording the distance between tufts within each quadrat. Litter cover was determined by visual observation and rated on a scale of 1 to 5. A number of physical and chemical soil properties were used to quantify the effects of degradation on soil quality. To determine soil chemical properties, three soil samples were collected at a depth of 20 cm, in each plot and analyzed for pH, soil macro (N, C, K, P, Ca, Mg) and micro (Zn, Fe, Mn and Cu) nutrients. Soil compaction was determined using a soil pocket penetrometer. Readings were taken at 5 mm from 30 points placed at 1 m intervals and distributed in a randomly established straight line in each plot. Soil loss was determined using a rainfall simulator. Splash cups were filled with soil and placed under the rainfall simulator for 8 minutes per rainstorm at 360 mm-1 intensity. Results showed that at Esigingqini a total of 20 herbaceous species were identified, 17 of which were grasses. About 60percent of the identified grasses were Increaser II species, 15percent were Increaser II and 25percent Decreasers. In terms of palatability, 50percent of the grass species had poor palatability and the remaining had either average or high palatability. At Kwezana, 18 herbaceous species were identified of which 28percent were Decreasers and 61percent were Increaser II species. Half of the species had low palatability and only 28percent had high palatability. In both communal areas, litter cover was highest (P < 0.05) in the non-degraded areas followed by the slightly degraded sites and this was to be expected. Similarly, in both communal areas, there was a shift in species composition of decreasers and perennial grasses being replaced by annual species of poor quality and low palatability as the degradation levels increased. Results on soil chemical properties showed that the non-degraded areas had higher (P < 0.05) pH levels (8.5) than the severely degraded soils (5). A similar trend following a degradation gradient was observed for some soil nutrients such as N, P or Mg. Both the macro and micro nutrient concentrations were relatively higher (P < 0.05) in summer than in winter in both communal areas. Results on physical properties showed that soil loss and compaction were relatively lower (P <0.05) in the slightly degraded and non-degraded sites and increased with severity of degradation. In both communal areas, the severely degraded areas lost soil up to 1.1 t ha-1 due to degradation and the non-degraded areas had a soil loss of less than 0.8 t ha-1. The rate of soil loss between the severely and non-degraded areas is significantly different. The differences may be attributed to the differences in the vegetation cover which influences the rate of erosion on the various degradation gradients. These results suggest that both the grass layer and soil quality is negatively affected by degradation. Therefore, there is a need for land use practices that promote the sustainable use of rangeland resources. Such practices may include rotational grazing, reseeding, veld resting and fire. Measures to control the consequences of degradation and rehabilitate these deteriorated rangelands must be a priority.
- Full Text:
- Date Issued: 2017
- Authors: Maziko, Yonela
- Date: 2017
- Subjects: Communal rangelands -- South Africa -- Eastern Cape Land degradation -- South Africa -- Eastern Cape Vegetation management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/15056 , vital:40159
- Description: This study was conducted to investigate the influence of degradation on vegetation and soil quality in two semi-arid rangelands in the Eastern Cape Province of South Africa. The study was undertaken in Kwezana and Esigingqini communal areas that showed signs id degradation. The assessment incorporated the soil and grass layer in different degradation levels, namely nondegraded, slightly degraded, moderately and severely degraded. The non-degraded has a sufficient amount of vegetation cover and species composition. The slightly degraded site consists of a few visible bare patches. The moderately degraded areas showed signs of active sheet erosion such as pedestals and a higher percentage of bare areas and the severely degraded area is characterized by dongas and gullies, with vast areas that have no ground cover or top fertile soil layer. Using a step point method, herbaceous species composition was determined within three transects from three plots 100 m x 40 m in each degradation level. The aboveground phytomass production was determined by harvesting herbaceous species within four randomly placed 0.25 m2 quadrats in each transect. Bare ground was determined by counting and recording the distance between tufts within each quadrat. Litter cover was determined by visual observation and rated on a scale of 1 to 5. A number of physical and chemical soil properties were used to quantify the effects of degradation on soil quality. To determine soil chemical properties, three soil samples were collected at a depth of 20 cm, in each plot and analyzed for pH, soil macro (N, C, K, P, Ca, Mg) and micro (Zn, Fe, Mn and Cu) nutrients. Soil compaction was determined using a soil pocket penetrometer. Readings were taken at 5 mm from 30 points placed at 1 m intervals and distributed in a randomly established straight line in each plot. Soil loss was determined using a rainfall simulator. Splash cups were filled with soil and placed under the rainfall simulator for 8 minutes per rainstorm at 360 mm-1 intensity. Results showed that at Esigingqini a total of 20 herbaceous species were identified, 17 of which were grasses. About 60percent of the identified grasses were Increaser II species, 15percent were Increaser II and 25percent Decreasers. In terms of palatability, 50percent of the grass species had poor palatability and the remaining had either average or high palatability. At Kwezana, 18 herbaceous species were identified of which 28percent were Decreasers and 61percent were Increaser II species. Half of the species had low palatability and only 28percent had high palatability. In both communal areas, litter cover was highest (P < 0.05) in the non-degraded areas followed by the slightly degraded sites and this was to be expected. Similarly, in both communal areas, there was a shift in species composition of decreasers and perennial grasses being replaced by annual species of poor quality and low palatability as the degradation levels increased. Results on soil chemical properties showed that the non-degraded areas had higher (P < 0.05) pH levels (8.5) than the severely degraded soils (5). A similar trend following a degradation gradient was observed for some soil nutrients such as N, P or Mg. Both the macro and micro nutrient concentrations were relatively higher (P < 0.05) in summer than in winter in both communal areas. Results on physical properties showed that soil loss and compaction were relatively lower (P <0.05) in the slightly degraded and non-degraded sites and increased with severity of degradation. In both communal areas, the severely degraded areas lost soil up to 1.1 t ha-1 due to degradation and the non-degraded areas had a soil loss of less than 0.8 t ha-1. The rate of soil loss between the severely and non-degraded areas is significantly different. The differences may be attributed to the differences in the vegetation cover which influences the rate of erosion on the various degradation gradients. These results suggest that both the grass layer and soil quality is negatively affected by degradation. Therefore, there is a need for land use practices that promote the sustainable use of rangeland resources. Such practices may include rotational grazing, reseeding, veld resting and fire. Measures to control the consequences of degradation and rehabilitate these deteriorated rangelands must be a priority.
- Full Text:
- Date Issued: 2017
The impact of the farmer field school approach on small-scale vegetable farmers' knowledge, agency and production in Alice, Eastern Cape
- Authors: Apleni, Asanda
- Date: 2017
- Subjects: Agricultural extension work -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8187 , vital:31873
- Description: This study investigates the impact of the Farmer Field School approach on the knowledge, agency and production of small-scale farmers. Farmer Field Schools were devised in the 1980s by the Food and Agriculture Organization as a form of adult education in agriculture. It is a group-based approach in which a facilitator meets with farmers on a regular basis and sets in motion a process by which farmers ‘learn how to learn’, both from themselves and from one another. However, it remains an open question whether the Farmer Field School approach could be a solution to South Africa’s abiding problem of weak agricultural extension. Early in 2015, the University of Fort Hare and the Nkonkobe Farmers’ Association initiated a number of study groups in the Alice area, based largely on Farmer Field School principles. The main objective of the study was to assess the impact of the Farmer Field School approach on small-scale farmers’ knowledge, agency and production, focusing on home gardeners. The study was conducted in the Raymond Mhlaba Local Municipality in Alice of the Eastern Cape Province of South Africa. The research consisted of a survey of all the study group participants involved with home gardens, including some who joined the groups in 2015 but left in 2016. Both cross-sectional and longitudinal designs were used. Findings from this study have shown how participation in the study groups modelled on the FFS approach can improve the knowledge and skills of home gardeners, while also enabling them to produce significantly larger quantities of vegetables, and even a marketable surplus, albeit from a small base. In order to make more people to join, more incentives should be made available. Such incentives should be made available only to “kick start” the FFS study groups and take heed in prevention of dependence.
- Full Text:
- Date Issued: 2017
- Authors: Apleni, Asanda
- Date: 2017
- Subjects: Agricultural extension work -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8187 , vital:31873
- Description: This study investigates the impact of the Farmer Field School approach on the knowledge, agency and production of small-scale farmers. Farmer Field Schools were devised in the 1980s by the Food and Agriculture Organization as a form of adult education in agriculture. It is a group-based approach in which a facilitator meets with farmers on a regular basis and sets in motion a process by which farmers ‘learn how to learn’, both from themselves and from one another. However, it remains an open question whether the Farmer Field School approach could be a solution to South Africa’s abiding problem of weak agricultural extension. Early in 2015, the University of Fort Hare and the Nkonkobe Farmers’ Association initiated a number of study groups in the Alice area, based largely on Farmer Field School principles. The main objective of the study was to assess the impact of the Farmer Field School approach on small-scale farmers’ knowledge, agency and production, focusing on home gardeners. The study was conducted in the Raymond Mhlaba Local Municipality in Alice of the Eastern Cape Province of South Africa. The research consisted of a survey of all the study group participants involved with home gardens, including some who joined the groups in 2015 but left in 2016. Both cross-sectional and longitudinal designs were used. Findings from this study have shown how participation in the study groups modelled on the FFS approach can improve the knowledge and skills of home gardeners, while also enabling them to produce significantly larger quantities of vegetables, and even a marketable surplus, albeit from a small base. In order to make more people to join, more incentives should be made available. Such incentives should be made available only to “kick start” the FFS study groups and take heed in prevention of dependence.
- Full Text:
- Date Issued: 2017
The influence of environmental variability on the catch of chokka, Loligo reynaudii, off the coast of South Africa
- Authors: Joyner, Jessica Mary
- Date: 2017
- Subjects: Loligo reynaudii , Loligo fisheries -- South Africa , Squid fisheries -- South Africa , Loligo fisheries -- Environmental aspects -- South Africa , Squid fisheries -- Environmental aspects - South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/32130 , vital:24013
- Description: Globally, cephalopod fisheries are being relied on more heavily due to the depletion of longer-lived teleost species. The South African chokka squid (Loligo reynaudii) fishery is a case in point. Although previously numerous squid were often caught as bycatch, the fishery has officially been in place since 1985. Since the inception of the chokka fishery in South Africa, several studies have investigated the relationship between environmental drivers and annual chokka squid catch, with varying degrees of success. Recently, in 2013, chokka squid catches hit a record low, prompting resurgence in the topic of the squid environment-catch relationship. This study was initiated in an attempt to provide a quantitative relationship between the chokka squid catch and environmental variability, and to build a predictive model that could be used in fisheries management strategies. Historical data were obtained from various sources and included the mean and standard deviation in ocean bottom temperature; the mean and standard deviation in sea surface temperature; the maximum and minimum as well as the variation in wind speed; the mean, predominant and standard deviation in wind direction; the mean and standard deviation in atmospheric pressure; the mean chlorophyll concentration; the number of upwelling events; the hours of easterly winds blowing per day; and two large variation-in-climate indices, namely, the oceanic Nino index and the Antarctic Oscillation index. The monthly catch data were also provided. These data were initially analysed for inter-annual and intra-annual cyclic trends and followed by analysis of the delay in response of catch to the environmental variables, anticipating some impact on the different stages of the chokka life cycle. These lagged data were incorporated into a negative binomial generalised linear model, as well as a generalised additive model, which revealed a strong relationship (r²=0.707) between the catch and environmental variability. The inclusion of all the parameters was necessary; however, the mean bottom temperature and the standard deviation in sea surface temperature were the only parameters that had a significant effect on the catch. These results were used to build a predictive model that indicated that, although the relationship was strong, the ability of the model to predict catch was weak, particularly from the year 2005 onwards.
- Full Text:
- Date Issued: 2017
- Authors: Joyner, Jessica Mary
- Date: 2017
- Subjects: Loligo reynaudii , Loligo fisheries -- South Africa , Squid fisheries -- South Africa , Loligo fisheries -- Environmental aspects -- South Africa , Squid fisheries -- Environmental aspects - South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/32130 , vital:24013
- Description: Globally, cephalopod fisheries are being relied on more heavily due to the depletion of longer-lived teleost species. The South African chokka squid (Loligo reynaudii) fishery is a case in point. Although previously numerous squid were often caught as bycatch, the fishery has officially been in place since 1985. Since the inception of the chokka fishery in South Africa, several studies have investigated the relationship between environmental drivers and annual chokka squid catch, with varying degrees of success. Recently, in 2013, chokka squid catches hit a record low, prompting resurgence in the topic of the squid environment-catch relationship. This study was initiated in an attempt to provide a quantitative relationship between the chokka squid catch and environmental variability, and to build a predictive model that could be used in fisheries management strategies. Historical data were obtained from various sources and included the mean and standard deviation in ocean bottom temperature; the mean and standard deviation in sea surface temperature; the maximum and minimum as well as the variation in wind speed; the mean, predominant and standard deviation in wind direction; the mean and standard deviation in atmospheric pressure; the mean chlorophyll concentration; the number of upwelling events; the hours of easterly winds blowing per day; and two large variation-in-climate indices, namely, the oceanic Nino index and the Antarctic Oscillation index. The monthly catch data were also provided. These data were initially analysed for inter-annual and intra-annual cyclic trends and followed by analysis of the delay in response of catch to the environmental variables, anticipating some impact on the different stages of the chokka life cycle. These lagged data were incorporated into a negative binomial generalised linear model, as well as a generalised additive model, which revealed a strong relationship (r²=0.707) between the catch and environmental variability. The inclusion of all the parameters was necessary; however, the mean bottom temperature and the standard deviation in sea surface temperature were the only parameters that had a significant effect on the catch. These results were used to build a predictive model that indicated that, although the relationship was strong, the ability of the model to predict catch was weak, particularly from the year 2005 onwards.
- Full Text:
- Date Issued: 2017
The influence of extraction techniques on the chemical composition of essential oils from Pelargonium cv.rose in the Eastern Cape
- Authors: Ngcangatha-Maqhude, Bulelwa
- Date: 2017
- Subjects: Essences and essential oils Pelargoniums Rose geranium oil
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8111 , vital:31524
- Description: Rose geranium is a world known essential oil plant priced for its high grade essential oil mostly utilized in the perfumery industry. However, South Africa has just joined the geranium oil production industry and still battling with the variations in oil yield and composition. Volatile components from Rose geranium were respectively extracted by three methods including hydro-distillation, steam distillation and solvent free microwave. The composition was characterized by GC-FID and GC-MS .No significant differences were found in the oil constituents, colour of the oil was the same in hydro-distillation and steam distillation (light green) but in solvent free microwave extraction the oil was clear because in the receiving flask there was hexane and the quantity of the oil was not the same. The difference was the time taken to extract the oil: Hydro-distillation took 3 hours, steam distillation took 1 hour, 30 minutes and solvent free microwave took only 30 minutes. The main constituents of the essential oil of rose geranium (steam distillation) are Dohne: Citronellol (20.61percent), geraniol (14.79percent), linalool (1.98percent), citronellyl formate (14.25percent), geranyl formate (10.25percent) and guaiadiene 6, 9 (7.22percent). Kieskammahoek: Citronellol (20.36percent), geraniol (9.81percent), linalool (1.54percent), citronellyl formate (16.09percent), geranyl formate F (8.96percent) and guaiadiene 6, 9 (8. 22percent).University of FortHare: Citronellol (21.55percent), geraniol (9.41percent), linalool (1.40percent), citronellyl formate (16.37percent), geranyl formate (8.10percent) and guaiadiene 6, 9 7.92percent). For hydro-distillation, Dohne: Citronellol (24.68percent), geraniol (11.68percent), linalool (11.74percent), citronellyl formate (14.97percent), geranyl formate (5.95percent) and guaiadiene 6, 9 (4.63percent). Kieskammahoek: Citronellol (25.25percent), geraniol (13.44percent), linalool (3.35percent), citronellyl formate (15.62percent), geranyl formate (5.40percent) and guaiadiene 6, 9(4.96percent).University of FortHare: Citronellol (24.73percent), geraniol (8.35percent), linalool (9.76percent), citronellyl formate (16.54percent), geranyl formate (4.42percent) and guaiadiene 6, 9(9.76percent). The solvent free microwave extraction , Dohne: Citronellol (20.87), geraniol (17.85percent), linalool (1.21percent), citronellyl formate (13.44percent), geranyl formate (10.26percent) and guaiadiene 6, 9 (4.59percent).Kieskammahoek: Citronellol (20.13percent), geraniol (5.40percent), linalool (0.28percent), citronellyl formate (14.22percent), geranyl formate (6.04percent) and guaiadiene 6, 9(8.63percent).University of FortHare: Citronellol (21.15percent), geraniol (22.36percent), linalool (1.37percent), citronellyl formate (12.13percent), geranyl formate (8.91percent) and guaiadiene 6, 9 (5.82percent).The percentage of oil composition in hydro-distillation and Solvent Free Microwave Extraction was higher than steam distillation.
- Full Text:
- Date Issued: 2017
- Authors: Ngcangatha-Maqhude, Bulelwa
- Date: 2017
- Subjects: Essences and essential oils Pelargoniums Rose geranium oil
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8111 , vital:31524
- Description: Rose geranium is a world known essential oil plant priced for its high grade essential oil mostly utilized in the perfumery industry. However, South Africa has just joined the geranium oil production industry and still battling with the variations in oil yield and composition. Volatile components from Rose geranium were respectively extracted by three methods including hydro-distillation, steam distillation and solvent free microwave. The composition was characterized by GC-FID and GC-MS .No significant differences were found in the oil constituents, colour of the oil was the same in hydro-distillation and steam distillation (light green) but in solvent free microwave extraction the oil was clear because in the receiving flask there was hexane and the quantity of the oil was not the same. The difference was the time taken to extract the oil: Hydro-distillation took 3 hours, steam distillation took 1 hour, 30 minutes and solvent free microwave took only 30 minutes. The main constituents of the essential oil of rose geranium (steam distillation) are Dohne: Citronellol (20.61percent), geraniol (14.79percent), linalool (1.98percent), citronellyl formate (14.25percent), geranyl formate (10.25percent) and guaiadiene 6, 9 (7.22percent). Kieskammahoek: Citronellol (20.36percent), geraniol (9.81percent), linalool (1.54percent), citronellyl formate (16.09percent), geranyl formate F (8.96percent) and guaiadiene 6, 9 (8. 22percent).University of FortHare: Citronellol (21.55percent), geraniol (9.41percent), linalool (1.40percent), citronellyl formate (16.37percent), geranyl formate (8.10percent) and guaiadiene 6, 9 7.92percent). For hydro-distillation, Dohne: Citronellol (24.68percent), geraniol (11.68percent), linalool (11.74percent), citronellyl formate (14.97percent), geranyl formate (5.95percent) and guaiadiene 6, 9 (4.63percent). Kieskammahoek: Citronellol (25.25percent), geraniol (13.44percent), linalool (3.35percent), citronellyl formate (15.62percent), geranyl formate (5.40percent) and guaiadiene 6, 9(4.96percent).University of FortHare: Citronellol (24.73percent), geraniol (8.35percent), linalool (9.76percent), citronellyl formate (16.54percent), geranyl formate (4.42percent) and guaiadiene 6, 9(9.76percent). The solvent free microwave extraction , Dohne: Citronellol (20.87), geraniol (17.85percent), linalool (1.21percent), citronellyl formate (13.44percent), geranyl formate (10.26percent) and guaiadiene 6, 9 (4.59percent).Kieskammahoek: Citronellol (20.13percent), geraniol (5.40percent), linalool (0.28percent), citronellyl formate (14.22percent), geranyl formate (6.04percent) and guaiadiene 6, 9(8.63percent).University of FortHare: Citronellol (21.15percent), geraniol (22.36percent), linalool (1.37percent), citronellyl formate (12.13percent), geranyl formate (8.91percent) and guaiadiene 6, 9 (5.82percent).The percentage of oil composition in hydro-distillation and Solvent Free Microwave Extraction was higher than steam distillation.
- Full Text:
- Date Issued: 2017
The interaction of selected bacteria with tailored electrospun fibres: towards future applications in bioremediation, bacterial inactivation and electricity generation
- Authors: Mfuku, Aphiwe
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65123 , vital:28693
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
- Authors: Mfuku, Aphiwe
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65123 , vital:28693
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
The investigation of the role and the efficacy of learning technologies towards community skill development
- Authors: Masikisiki, Baphumelele
- Date: 2017
- Subjects: Web-based instruction Computer-assisted instruction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5972 , vital:29460
- Description: Research has revealed that during systems design and development of e-learning technologies there is a tendency of neglecting the needs of end users and focus on the design process and the technology factors, and this has traditionally been the reason for poor usability of otherwise well conceptualized systems, as a result a number of IT-based learning tools ended up not being usable and not being utilized effectively. This study aims to investigate the impact of e-learning technologies, how people perceive the usage of e-learning technologies towards community skill development. An evaluation of four different e-learning technologies was conducted to investigate the role and efficacy of e-learning technologies within the surrounding communities. Data was analyzed as nominal data using IBM Statistical Package for Social Sciences (SPSS) software 24. Descriptive analysis, frequency, reliability and correctional analysis and also measures of central tendency were computed. Reliability was evaluated for assessing the internal consistency of the items using Cronbach’s alpha. To analyze the relationship between variables matrices of Pearson’s correlation was used. Pearson’s correlation can only be accepted when the significant effect (P>.05), this indicates that there is a positive or a negative relationship between two variables, if these conditions are not met then the proposed correlation or hypothesis can be rejected. Results indicate a poor perception and poor acceptance of e-learning technologies due to a number of factors, these factors include lack of computer-self efficacy which leads to computer anxiety, affordability of internet connectivity which leads to inaccessible of e-learning technologies. The findings also indicated that LAMS was found to be less useable and less useful by a number of students. However, students who enjoy working in groups found LAMS to be useable because it was supporting their preferred learning style, whereas individualistic students preferred Moodle and Dokeos because it was supporting their personal preferences and assessment styles. Having understood all the characteristics of learning tools, relevant learning technologies that are suitable for students can then be recommended.
- Full Text:
- Date Issued: 2017
- Authors: Masikisiki, Baphumelele
- Date: 2017
- Subjects: Web-based instruction Computer-assisted instruction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/5972 , vital:29460
- Description: Research has revealed that during systems design and development of e-learning technologies there is a tendency of neglecting the needs of end users and focus on the design process and the technology factors, and this has traditionally been the reason for poor usability of otherwise well conceptualized systems, as a result a number of IT-based learning tools ended up not being usable and not being utilized effectively. This study aims to investigate the impact of e-learning technologies, how people perceive the usage of e-learning technologies towards community skill development. An evaluation of four different e-learning technologies was conducted to investigate the role and efficacy of e-learning technologies within the surrounding communities. Data was analyzed as nominal data using IBM Statistical Package for Social Sciences (SPSS) software 24. Descriptive analysis, frequency, reliability and correctional analysis and also measures of central tendency were computed. Reliability was evaluated for assessing the internal consistency of the items using Cronbach’s alpha. To analyze the relationship between variables matrices of Pearson’s correlation was used. Pearson’s correlation can only be accepted when the significant effect (P>.05), this indicates that there is a positive or a negative relationship between two variables, if these conditions are not met then the proposed correlation or hypothesis can be rejected. Results indicate a poor perception and poor acceptance of e-learning technologies due to a number of factors, these factors include lack of computer-self efficacy which leads to computer anxiety, affordability of internet connectivity which leads to inaccessible of e-learning technologies. The findings also indicated that LAMS was found to be less useable and less useful by a number of students. However, students who enjoy working in groups found LAMS to be useable because it was supporting their preferred learning style, whereas individualistic students preferred Moodle and Dokeos because it was supporting their personal preferences and assessment styles. Having understood all the characteristics of learning tools, relevant learning technologies that are suitable for students can then be recommended.
- Full Text:
- Date Issued: 2017
The pest status and integrated management programme of carob moth, Ectomyelois ceratoniae Zeller, attacking citrus in South Africa
- Authors: Thackeray, Sean Robin
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7758 , vital:21293
- Description: The carob moth, Ectomyelois ceratoniae Zeller, is a pest of agricultural commodities and stored products around the world. Carob moth is known to infest citrus in the Mediterranean region and in southern Africa. In grapefruit cultivars, carob moth infestations are associated with high levels of mealybug. However, although this relationship has been observed in other citrus types such as Navel oranges, this has never been quantified. A recent survey of infested fruit from various production areas in South Africa indicated that the pest status of carob moth on Navel oranges may have been underestimated. As a result of the incidental pest status of carob moth on citrus in South Africa in the past, a species specific integrated pest management (IPM) programme does not exist. Therefore, the overriding aim of this theses was to evaluate the pest status of carob moth in citrus and establish a species specific IPM programme by determine the autecology of carob moth in citrus. Reliable methods for monitoring carob moth in citrus orchards both for producers and for research purposes were developed. A user-friendly monitoring method for determining weekly carob moth infestation through dropped fruit was suitable for producers. A timed scouting method was also developed; although the accuracy of this method varied with the experience of the scout. The pest status of carob moth was highest in the Loskop Valley, Nelspruit and the Vaalharts production areas and economic injury to growers ranged from R512.35 to R3 719.80 per hectare as a direct result of infestation. No infestation was recorded in the Sundays River Valley and Citrusdal production areas over both the 2014-15 and 201516 growing seasons. A laboratory study showed the survival of carob moth larvae infesting citrus is less than 10% in the absence of mealybug. However, this increases to almost 40% in the presence of mealybug residues and sooty mould. There was a significant relationship between carob infestation at harvest and mealybug infestation in the middle months of the growing season. The relationship between carob moth and mealybug indicates that current production guidelines for the management of mealybug in citrus may need to be amended. Consequently, it is proposed that an orchard with a history of carob moth infestation and a high mealybug infestation in the previous season should be subjected to an early season preventative application of a registered control product. Also, if mealybug infestation in December is higher than a 5% of fruit per tree, then a corrective application of a registered product is recommended. The application of 2,4-D at petal drop reduced the size of the navel-end opening, decreasing the proportion of mealybug found in the navel-end, subsequently reducing carob moth infestation, resulting in a direct benefit for producers. Products registered for the control of false codling moth (FCM), Thaumatotibia leucotreta Meyrick, were effective in reducing carob moth infestation. In a spray trial conducted over two seasons, Delegate® and Runner® reduced infestation significantly in the 2014-15 season (over 80%), while only Delegate® was effective in the 2015-16 season (over 80%). If a late season corrective chemical application is targeted at both FCM and carob moth, this application should take place between 6-7 weeks prior to harvest. The mating disruption product, SPLAT® EC, reduced carob moth infestation by 70% compared to the untreated control. A laboratory culture was established and head-capsule size categories were determined for all five carob moth instars. A parasitoid survey indicated that parasitism of carob moth larvae is generally less than 5% in citrus orchards and a new species of Braconidae was described as Phanterotoma carobivora van Achterberg and Thackeray. Carob moth fifth instar were found to be the most cold-tolerant larval stage, and were shown to be more cold susceptible than the most cold-tolerant FCM instars at -0.55ºC for eighteen days. This cold treatment resulted in a mortality of 94.6% fifth instar carob moth compared to a combined fourth and fifth instar mortality of 87.8% for FCM after eighteen days. These results indicate that post-harvest cold treatments targeting FCM will be as, if not more, effective against carob moth, suggesting that current phytosanitary legislation for carob moth should be amended to incorporate this study’s findings.
- Full Text:
- Date Issued: 2017
- Authors: Thackeray, Sean Robin
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7758 , vital:21293
- Description: The carob moth, Ectomyelois ceratoniae Zeller, is a pest of agricultural commodities and stored products around the world. Carob moth is known to infest citrus in the Mediterranean region and in southern Africa. In grapefruit cultivars, carob moth infestations are associated with high levels of mealybug. However, although this relationship has been observed in other citrus types such as Navel oranges, this has never been quantified. A recent survey of infested fruit from various production areas in South Africa indicated that the pest status of carob moth on Navel oranges may have been underestimated. As a result of the incidental pest status of carob moth on citrus in South Africa in the past, a species specific integrated pest management (IPM) programme does not exist. Therefore, the overriding aim of this theses was to evaluate the pest status of carob moth in citrus and establish a species specific IPM programme by determine the autecology of carob moth in citrus. Reliable methods for monitoring carob moth in citrus orchards both for producers and for research purposes were developed. A user-friendly monitoring method for determining weekly carob moth infestation through dropped fruit was suitable for producers. A timed scouting method was also developed; although the accuracy of this method varied with the experience of the scout. The pest status of carob moth was highest in the Loskop Valley, Nelspruit and the Vaalharts production areas and economic injury to growers ranged from R512.35 to R3 719.80 per hectare as a direct result of infestation. No infestation was recorded in the Sundays River Valley and Citrusdal production areas over both the 2014-15 and 201516 growing seasons. A laboratory study showed the survival of carob moth larvae infesting citrus is less than 10% in the absence of mealybug. However, this increases to almost 40% in the presence of mealybug residues and sooty mould. There was a significant relationship between carob infestation at harvest and mealybug infestation in the middle months of the growing season. The relationship between carob moth and mealybug indicates that current production guidelines for the management of mealybug in citrus may need to be amended. Consequently, it is proposed that an orchard with a history of carob moth infestation and a high mealybug infestation in the previous season should be subjected to an early season preventative application of a registered control product. Also, if mealybug infestation in December is higher than a 5% of fruit per tree, then a corrective application of a registered product is recommended. The application of 2,4-D at petal drop reduced the size of the navel-end opening, decreasing the proportion of mealybug found in the navel-end, subsequently reducing carob moth infestation, resulting in a direct benefit for producers. Products registered for the control of false codling moth (FCM), Thaumatotibia leucotreta Meyrick, were effective in reducing carob moth infestation. In a spray trial conducted over two seasons, Delegate® and Runner® reduced infestation significantly in the 2014-15 season (over 80%), while only Delegate® was effective in the 2015-16 season (over 80%). If a late season corrective chemical application is targeted at both FCM and carob moth, this application should take place between 6-7 weeks prior to harvest. The mating disruption product, SPLAT® EC, reduced carob moth infestation by 70% compared to the untreated control. A laboratory culture was established and head-capsule size categories were determined for all five carob moth instars. A parasitoid survey indicated that parasitism of carob moth larvae is generally less than 5% in citrus orchards and a new species of Braconidae was described as Phanterotoma carobivora van Achterberg and Thackeray. Carob moth fifth instar were found to be the most cold-tolerant larval stage, and were shown to be more cold susceptible than the most cold-tolerant FCM instars at -0.55ºC for eighteen days. This cold treatment resulted in a mortality of 94.6% fifth instar carob moth compared to a combined fourth and fifth instar mortality of 87.8% for FCM after eighteen days. These results indicate that post-harvest cold treatments targeting FCM will be as, if not more, effective against carob moth, suggesting that current phytosanitary legislation for carob moth should be amended to incorporate this study’s findings.
- Full Text:
- Date Issued: 2017
The potential of Elephantorrhiza elephantina as an anthelmintic of goats in the Eastern Cape province, South Africa
- Authors: Mazhangara, Irene Rumbidza
- Date: 2017
- Subjects: Bioactive compounds -- South Africa -- Eastern Cape Medicinal plants -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/15068 , vital:40160
- Description: The main objective of the study was to investigate the potential of Elephantorrhiza elephantina in the control of gastro-intestinal worms in goats in the Eastern Cape Province, South Africa. The ethanolic, methanolic and aqueous phytochemical composition of E. elephantina root bark extracts were determined. The phytochemical analysis revealed a high concentration of alkaloids, condensed tannins, flavonoids, phenols and saponins in E. elephantina root extracts. Quantitative phytochemical analysis of alkaloids in water extract was 932.44 ± 1.23 mg. Condensed tannins, phenols and saponins in ethanol extract were 450.52 ± 4.56 mg CE/g, 476.11 ± 0.03 mg GAE/g and 832.85 ± 1.45 mg respectively. Flavonoids was 803.93 ± 0.02 mg QE/g in methanol extract as the highest recordings. In vitro screening of ethanol, methanol and water extracts of E. elephantina for potential anthelminthic activity against adult Paramphistomum cervi worm motility showed time and dose-dependent significant effects after 12 hours of treatment. Ethanolic extracts showed a highly significant (P < 0.05) inhibition of motility (86.67 and 96.67 percent) at concentrations 7.5 and 15 mg/ml, respectively. Methanolic and aqueous extracts exhibited a significant (P < 0.05) motility inhibition (96.67 and 66.67 percent, respectively) at concentration of 15 mg/ml 16 hours post-exposure. In vitro assessment of structural changes to adult gastro-intestinal worms following exposure to E. elephantina extracts was done using scanning electron microscopy (SEM). The SEM observations revealed structural changes in the worms after contact with E. elephantina extracts in comparison with the control worms kept in Phosphate-buffered saline (PBS). The major alterations were around the cuticle, posterior and anterior areas. These changes included longitudinal and transversal folds and thicker cuticula ridges, material aggregates around the posterior and anterior areas. The study showed that ethanol, methanol and water extracts of E. elephantina root contained significant amounts of alkaloids, condensed tannins, flavanoids, phenols and saponins. Validation studies showed that extracts of E. elephantina possess anthelminthic activities. The structural changes found in the worms exposed to extracts of E. elephantina root extracts affected their motility and nutrition, resulting in mortality.
- Full Text:
- Date Issued: 2017
- Authors: Mazhangara, Irene Rumbidza
- Date: 2017
- Subjects: Bioactive compounds -- South Africa -- Eastern Cape Medicinal plants -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/15068 , vital:40160
- Description: The main objective of the study was to investigate the potential of Elephantorrhiza elephantina in the control of gastro-intestinal worms in goats in the Eastern Cape Province, South Africa. The ethanolic, methanolic and aqueous phytochemical composition of E. elephantina root bark extracts were determined. The phytochemical analysis revealed a high concentration of alkaloids, condensed tannins, flavonoids, phenols and saponins in E. elephantina root extracts. Quantitative phytochemical analysis of alkaloids in water extract was 932.44 ± 1.23 mg. Condensed tannins, phenols and saponins in ethanol extract were 450.52 ± 4.56 mg CE/g, 476.11 ± 0.03 mg GAE/g and 832.85 ± 1.45 mg respectively. Flavonoids was 803.93 ± 0.02 mg QE/g in methanol extract as the highest recordings. In vitro screening of ethanol, methanol and water extracts of E. elephantina for potential anthelminthic activity against adult Paramphistomum cervi worm motility showed time and dose-dependent significant effects after 12 hours of treatment. Ethanolic extracts showed a highly significant (P < 0.05) inhibition of motility (86.67 and 96.67 percent) at concentrations 7.5 and 15 mg/ml, respectively. Methanolic and aqueous extracts exhibited a significant (P < 0.05) motility inhibition (96.67 and 66.67 percent, respectively) at concentration of 15 mg/ml 16 hours post-exposure. In vitro assessment of structural changes to adult gastro-intestinal worms following exposure to E. elephantina extracts was done using scanning electron microscopy (SEM). The SEM observations revealed structural changes in the worms after contact with E. elephantina extracts in comparison with the control worms kept in Phosphate-buffered saline (PBS). The major alterations were around the cuticle, posterior and anterior areas. These changes included longitudinal and transversal folds and thicker cuticula ridges, material aggregates around the posterior and anterior areas. The study showed that ethanol, methanol and water extracts of E. elephantina root contained significant amounts of alkaloids, condensed tannins, flavanoids, phenols and saponins. Validation studies showed that extracts of E. elephantina possess anthelminthic activities. The structural changes found in the worms exposed to extracts of E. elephantina root extracts affected their motility and nutrition, resulting in mortality.
- Full Text:
- Date Issued: 2017
The potential of hydrellia egeriae rodrigues (diptera: ephydridae) as a biocontrol agent for egeria densa planch. (hydrocharitaceae) in South Africa
- Authors: Smith, Rosali
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53733 , vital:26314
- Description: The integrity of South Africa’s valuable freshwater ecosystems has been threatened by aquatic invasive plants since the 1900s. Floating aquatic weeds, such as Eichhornia crassipes (C. Mart) Solms (Pondederiaceae), Pistia stratiotes L. (Araceae), Salvinia molesta D.S. Mitchell (Salviniaceae), Azolla filiculoides Lam. (Azollaceae), and the emergent weed, Myriophyllum aquaticum Verdc. (Haloragaceae) benefited from open, nutrient-rich water bodies. Due to the limitations of mechanical and chemical control in aquatic environments, classical biological control has been a huge asset in managing these weeds; consequently bringing them under complete or substantial control. However, submerged aquatic weeds are widely distributed through the aquarium trade in South Africa; facilitating their invasion into new habitats. The removal of surface mats following the successful management of floating weeds has enhanced the growth and competitive ability of submerged aquatic weeds, such as Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), Myriophyllum spicatum L. (Haloragaceae) and Egeria densa Planch. (Hydrocharitaceae) in South Africa. Of these species, E. densa has become the most widely distributed, invading numerous systems across South Africa. Compared to other exotic submerged aquatic plants, E. densa is the only species capable of inhabiting freshwater systems in every province and therefore, it is vital to manage existing populations and prevent its further distribution and invasion. Hydrellia spp. (Diptera: Ephydridae) biological control agents have been used extensively in the management of submerged aquatic weeds elsewhere, particularly those in the Hydrocharitaceae (Balciunas and Burrows 1996; Wheeler and Center 2001. Hydrellia egeriae Rodrigues (Diptera: Ephydridae) has been identified as a promising candidate for E. densa and was imported into quarantine at Rhodes University, Grahamstown in 2014. The aims of this study were to conduct a pre-release assessment of the potential of H. egeriae as a biological control agent for E. densa in South Africa. The first objective of this study was to establish the life history of the agent under controlled conditions on E. densa found in South Africa, as well as its population growth parameters to predict its invasion success in the field. Secondly, laboratory host-specificity testing was conducted to validate the host range of the agent, in view of published native range host-specificity testing, and to establish potential risks to non-target species, should it be released. Finally, a biological control agent should also effectively reduce the fitness of its host plant, and therefore, impact studies were conducted. Laboratory impact studies have been limited in the past, in that they only investigate agent damage for short ecological periods, thus underestimating the damage capacity of the agent under investigation. Therefore, the damage capacity of H. egeriae was investigated over three consecutive generations in multi-generational impact trials. In a controlled environment of 22 ± 2°C, H. egeriae exhibited the ability to rapidly increase in population size within a short period of time, which will enhance agent establishment and build-up in the field. Host-specificity trials indicated that H. egeriae has a host range restricted to the Hydrocharitaceae, with exploratory feeding and development on Lagarosiphon major Ridley, L. muscoides Harvey and Vallisneria spiralis L. However, only L. major supported agent development during paired larval choice tests, and continuation trials showed that the test species was not physiologically capable of supporting viable agent populations. Risk analysis illustrated that the feeding and reproductive risks that H. egeriae pose to non-target species are very low and therefore, H. egeriae should be safe for release in South Africa. Additionally, significant damage to vital plant structures (shoot growth and side shoot length) was only recorded under high (five larvae) agent abundances. Encouragingly, the number of leaves mined at the end of the experiment was similar for both intermediate (three) and high (five) larval abundances, suggesting that cumulative leaf-mining under intermediate larval abundances has the potential to reduce the fitness of E. densa, given sufficient time. Results from pre-release assessments provide a robust understanding of the specialization of the potential biological control agent to its host plant. Nevertheless, the absolute success of a biological control programme depends on the many factors after prerelease assessments that determine agent establishment, persistence and target weed suppression, e.g. mass-rearing, release protocols and a/biotic factors within the recipient community. Considering these factors, the best mass-rearing and release protocols are proposed here and future research priorities are identified. Finally, the long term success for managing E. densa in South Africa will require a holistic approach to address the underlying factors, such as eutrophication and human-mediated distribution that drive submerged aquatic plant invasions.
- Full Text:
- Date Issued: 2017
- Authors: Smith, Rosali
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53733 , vital:26314
- Description: The integrity of South Africa’s valuable freshwater ecosystems has been threatened by aquatic invasive plants since the 1900s. Floating aquatic weeds, such as Eichhornia crassipes (C. Mart) Solms (Pondederiaceae), Pistia stratiotes L. (Araceae), Salvinia molesta D.S. Mitchell (Salviniaceae), Azolla filiculoides Lam. (Azollaceae), and the emergent weed, Myriophyllum aquaticum Verdc. (Haloragaceae) benefited from open, nutrient-rich water bodies. Due to the limitations of mechanical and chemical control in aquatic environments, classical biological control has been a huge asset in managing these weeds; consequently bringing them under complete or substantial control. However, submerged aquatic weeds are widely distributed through the aquarium trade in South Africa; facilitating their invasion into new habitats. The removal of surface mats following the successful management of floating weeds has enhanced the growth and competitive ability of submerged aquatic weeds, such as Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), Myriophyllum spicatum L. (Haloragaceae) and Egeria densa Planch. (Hydrocharitaceae) in South Africa. Of these species, E. densa has become the most widely distributed, invading numerous systems across South Africa. Compared to other exotic submerged aquatic plants, E. densa is the only species capable of inhabiting freshwater systems in every province and therefore, it is vital to manage existing populations and prevent its further distribution and invasion. Hydrellia spp. (Diptera: Ephydridae) biological control agents have been used extensively in the management of submerged aquatic weeds elsewhere, particularly those in the Hydrocharitaceae (Balciunas and Burrows 1996; Wheeler and Center 2001. Hydrellia egeriae Rodrigues (Diptera: Ephydridae) has been identified as a promising candidate for E. densa and was imported into quarantine at Rhodes University, Grahamstown in 2014. The aims of this study were to conduct a pre-release assessment of the potential of H. egeriae as a biological control agent for E. densa in South Africa. The first objective of this study was to establish the life history of the agent under controlled conditions on E. densa found in South Africa, as well as its population growth parameters to predict its invasion success in the field. Secondly, laboratory host-specificity testing was conducted to validate the host range of the agent, in view of published native range host-specificity testing, and to establish potential risks to non-target species, should it be released. Finally, a biological control agent should also effectively reduce the fitness of its host plant, and therefore, impact studies were conducted. Laboratory impact studies have been limited in the past, in that they only investigate agent damage for short ecological periods, thus underestimating the damage capacity of the agent under investigation. Therefore, the damage capacity of H. egeriae was investigated over three consecutive generations in multi-generational impact trials. In a controlled environment of 22 ± 2°C, H. egeriae exhibited the ability to rapidly increase in population size within a short period of time, which will enhance agent establishment and build-up in the field. Host-specificity trials indicated that H. egeriae has a host range restricted to the Hydrocharitaceae, with exploratory feeding and development on Lagarosiphon major Ridley, L. muscoides Harvey and Vallisneria spiralis L. However, only L. major supported agent development during paired larval choice tests, and continuation trials showed that the test species was not physiologically capable of supporting viable agent populations. Risk analysis illustrated that the feeding and reproductive risks that H. egeriae pose to non-target species are very low and therefore, H. egeriae should be safe for release in South Africa. Additionally, significant damage to vital plant structures (shoot growth and side shoot length) was only recorded under high (five larvae) agent abundances. Encouragingly, the number of leaves mined at the end of the experiment was similar for both intermediate (three) and high (five) larval abundances, suggesting that cumulative leaf-mining under intermediate larval abundances has the potential to reduce the fitness of E. densa, given sufficient time. Results from pre-release assessments provide a robust understanding of the specialization of the potential biological control agent to its host plant. Nevertheless, the absolute success of a biological control programme depends on the many factors after prerelease assessments that determine agent establishment, persistence and target weed suppression, e.g. mass-rearing, release protocols and a/biotic factors within the recipient community. Considering these factors, the best mass-rearing and release protocols are proposed here and future research priorities are identified. Finally, the long term success for managing E. densa in South Africa will require a holistic approach to address the underlying factors, such as eutrophication and human-mediated distribution that drive submerged aquatic plant invasions.
- Full Text:
- Date Issued: 2017