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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Seasonal pharmacological and phytochemical properties of medicinal bulbs.

Ncube, Bhekumthetho. January 2010 (has links)
Medicinal bulbs form part of the diversified flora in South Africa. The plants are used extensively in South African traditional medicine in the treatment of various ailments. Due to the ever-increasing demand and the unrestricted collection of medicinal plants from the wild, many of these slow growing bulbous plant species are driven into over-exploitation and extinction. The main parts collected for use are the underground bulbs, leading to the destructive harvesting of the whole plant. This form of plant harvesting poses threats to the long term sustainability of these plant resources from their natural habitats. Sustainable harvesting of these plants should be within the limits of their capacity for self-renewal. However, this seldom occurs with the often inconsiderate medicinal plant gatherers. Conservation of these plants is therefore necessary. A strategy that would take into consideration the sustainable harvesting and perhaps simultaneously provide similar medicinal benefits, would be the substitution of bulbs with leaves of the same plant. This study was aimed at evaluating the seasonal pharmacological and phytochemical properties in bulbs/corms and leaves of medicinal bulbs with a view of promoting the substitution of bulbs with leaves in traditional medicinal use. Four medicinal bulbous plants, Tulbaghia violacea, Hypoxis hemerocallidea, Drimia robusta and Merwilla plumbea were evaluated for the pharmacological and phytochemical properties in their bulbs/corms and leaves in spring, summer, autumn and winter seasons, with a view of promoting the use of leaves as a conservation strategy. Dried plant materials were sequentially extracted with petroleum ether (PE), dichloromethane (DCM), 80% ethanol (EtOH) and water in each season. The extracts were tested for activities against Gram-positive (Bacillus subtilis and Staphylococcus aureus), Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacteria and the fungus Candida albicans using the in vitro microdilution assays to obtain minimum inhibitory concentrations (MIC) and minimum fungicidal concentrations (MFC). The four plant species were also evaluated for their ability to inhibit cyclooxygenase (COX-1 and COX-2) enzymes. Spectrophotometric methods were used to evaluate saponin and phenolic contents of samples from the four plant species in each season. Antibacterial activity was fairly comparable between bulbs/corms and leaves of H. hemerocallidea, T. violacea, and M. plumbea, with at least one extract showing some good activity (MIC < 1 mg/ml) in most of the seasons. Bulb extracts of D. robusta did not show good antibacterial activity while the leaf extracts showed good activity (0.78 mg/ml) against B. subtilis in spring, summer, and autumn and S. aureus (0.78 mg/ml) in autumn. The best antibacterial activity was recorded in winter, with MIC values as low as 0.195 mg/ml from the DCM bulb extracts of T. violacea against K. pneumoniae and S. aureus and PE corm extracts of H. hemerocallidea (0.195 mg/ml) against B. subtilis. Good antibacterial activity from water extracts were only recorded from corm extracts of H. hemerocallidea in summer, autumn and winter, H. hemerocallidea leaf extracts in autumn and winter, and M. plumbea bulb extracts in autumn. The leaf extracts of all the screened plant species demonstrated good fungicidal activity in autumn, with H. hemerocallidea corm water extracts recording an MFC value as low as 0.39 mg/ml. The leaf extracts of H. hemerocallidea (water), D. robusta (DCM) and M. plumbea (DCM) had good MFC values of 0.78 mg/ml each, in spring. The DCM leaf extracts of T. violacea also showed good fungicidal activity (0.78 mg/ml) in summer, while corm water extracts of H. hemerocallidea had an MFC value of 0.39 mg/ml in winter. There were no fungicidal activities recorded from all the bulb extracts in all the seasons. All the PE and DCM extracts in all the tested plant samples recorded between moderate (40-70%) and high (> 70%) COX-1 and COX-2 inhibition levels across all seasons. The EtOH corm extracts of H. hemerocallidea also demonstrated moderate to high inhibitory activity against COX-1 enzyme across all seasons. Bulb and leaf extracts of T. violacea showed selective inhibitory activity for COX-2 enzyme in all the seasons. The highest COX inhibitory levels were recorded in COX-2 from the PE leaf (spring) and bulb (autumn) extracts of T. violacea, with both recording 100% inhibitory activity. Phytochemical analysis revealed higher total phenolic compounds in bulbs/corms and leaves of all the analysed plant species, to be either higher in spring or winter. Plant material collected in autumn had the least levels of total phenolics. An almost similar trend to that of total phenolics was observed for flavonoids, gallotannins and condensed tannins in most plant samples, with higher levels either in spring or winter. Total saponins were consistently higher in winter than in the other seasons in all the screened plant species. There were in some cases, relationships between the peaks in the levels of some phytochemical compounds and the observed levels of bioactivity in different assays. The results obtained from this study demonstrate that the leaves of the screened plant species may substitute or complement bulbs in the treatment of certain ailments in traditional medicine. Thus, plant part substitution can be sustainably utilised in the conservation of these plant species while retaining the same medicinal benefits. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.
102

Critical path method as a project modelling technique in coal refurbishment projects

29 June 2015 (has links)
M.Ing. (Engineering Management) / South African power demand has been increasing over the past years due to increase in energy consumption from industrial, commercial and residential sectors. In order to meet the growing power demand Eskom Holdings Limited SOC (Eskom) has implemented a number of initiatives such as the energy efficiency programme, power generating capacity increase and refurbishment of the operational coal fired power stations. Energy efficiency initiatives have been designed to encourage residential, commercial and industrial customers to use energy efficient technologies which consume less energy compare to conventional technologies. Power generating capacity increase programme includes construction of new base and peaking generating power plants (such as Medupi, Kusile and Ingula) and return to service of the old generating plants (such as Camden, Komati and Grootvlei). The refurbishment programme or coal refurbishment involves upgrading of operational coal fired power stations with the objective of extending their life expectancy, improve performance and to ensure compliance to latest safety standards...
103

Defending an icon: the Matsulu Centre for Rhino Defense

Bosman, Ruan January 2017 (has links)
Thesis is submitted in partial fulfilment for the degree of Master of Architecture (Professional) to the Faculty of Engineering and the Built Environment, School of Architecture and Planning at the University of the Witwatersrand, Johannesburg, 2017 / In light of an increasing scientific and social focus on unsustainable human practices, mankind’s dominant relationship with the natural world is now being challenged. Few phenomena demonstrate this destructive relationship better than the growing number of animals being driven to extinction through human actions. The most notable of these, within the South African context, is the devastation of rhinoceros populations caused by illegal poaching, particularly in the Kruger National Park. In dealing with this issue, we have a unique opportunity to embody and catalyse a sustainable paradigm shift. Such a shift would seek to transition mankind into a symbiotic rather than parasitic relationship with the natural world. It would promote the use of cutting edge technologies for the benefit both human and non-human actors, breaking down the separation between man and nature. The resultant hybridised ecosystem would stand as an exemplary manifestation of the long theorised ‘cyborg’ entity, not as individual, but as a new form of habitat and, ultimately, societal organisation. Contextualising such a ‘Cyborgian Nexus’ as a solution to the scourge of rhino poaching is the chief subject of this research report. The Matsulu Centre for Rhino Defense is proposed as a Connected Conservation Centre in the disadvantaged Matsulu community, bordering the Kruger National Park. Its aim is to be the heart of a sophisticated system of cutting edge technologies which allow park rangers to overcome the poaching threat. Through its program as well as its architecture, the project aims to become a recognizable icon of a new relationship between man and nature. One in which human innovation allows for the natural world and the human world to coexist sustainably to the mutual benefit of both. / GR2017
104

The design of a wildlife medical centre at the National Zoological Gardens.

Lloyd-Lister, Nadia. January 2014 (has links)
M. Tech. Architecture (Professional) / The National Research Foundation has recognized the zoo as a critical player towards the conservation of animal heritage in southern Africa. Yet, as we have seen, tantamount to having outstanding research methods, is having the needed facilities to deploy them effectively. In order for this to come to bare, the zoo requires a careful assessment of architectural concerns. This thesis presents exactly those. The wildlife medical centre here proposed precipitates out of a comprehensive study engaging the following issues of concern; zoo healthcare and rehabilitation, sub-nature and animal architecture. The proposed site location currently supports the out-dated hospital (built in 1969), which is on the zoo's south-eastern corner along Boom Street. Its facilities include a veterinary hospital, research laboratories, a bio-bank, temporary wards, and rehabilitation wards whose design derives not only from traditional matters of architectural concern but also the informed, first-hand knowledge of the animals' needs and preferences as understood by the zoo's staff. Additionally, the proposed design exposes and showcases the zoo's research facilities along its public interface in order to better serve its educational efforts. Thus, this proposal presents the means for promoting conservation awareness and, at the same time, empowers its dedicated staff.
105

Lion (Panthera leo) social organisation in a human affected landscape.

Snyman, Andrei. January 2010 (has links)
Thesis (MTech. degree in Game Range Management.)--Tshwane University of Technology, 2010. / Lion (Panthera leo) social organisation in the Northern Tuli Game Reserve, Botswana, and the Venetia Limpopo Nature Reserve, South Africa, was investigated. Situated 20 km apart, the Northern Tuli Game Reserve is predominantly unfenced with unrestricted animal movements, as opposed to the Venetia Limpopo Nature Reserve which is completely fenced. Historically both lion populations have faced various but similar pressures such as safari hunting, snaring, poisoning and killing due to perceived conflict with livestock farmers.
106

Micropropagation of Brunsvigia undulata F.M. Leight.

Rice, Laura Jane. January 2009 (has links)
Many South African medicinal plants face the threat of over-collection for use in traditional medicines. Many bulbous plants suffer as the whole plant is removed from the wild so that the bulb may be used for medicine. Micropropagation is a technique which can be used as an alternative to conventional propagation methods. Micropropagation produces many plantlets in a relatively short period of time. Different plant parts of Brunsvigia undulata F.M. Leight, a rare South African species of medicinal value, were used in an attempt to produce in vitro plantlets using micropropagation techniques. Although leaf and floral explants were successfully formed from seedling explants and twin-scales. Seeds germinated quickly in culture. Seedlings which grew from seeds were cut into sections and used to initiate bulblets. Seedling explants formed bulblets, shoots and callus best when the explants included a meristematic region. Callus from seedling explants formed shoot clusters readily when placed on hormone-free MURASHIGE and SKOOG (1962) (MS) medium. Shoots from shoot clusters formed bulblets and rooted on medium supplemented with IBA. The greatest rooting response was achieved by bulblets on 1 mgl-1 IBA. The callus which was left after shoot clusters were separated was placed back onto hormone-free MS medium. Callus explants continued to form shoot clusters. Twin-scales, cut from large parent bulbs, were cultured on 25 hormone treatments. Bulblets formed on twin-scales even in the absence of plant growth hormones. Bulblets formed by twin-scales were used to determine the effects of both medium constituents and environmental factors on bulblet multiplication. Bulblet multiplication was greatest when bulblets were split in half and cultured as half-bulblets. Optimal multiplication was achieved on hormone-free MS, with 4% sucrose, kept at high temperatures in the dark. Bulblets were successfully initiated and multiplied from both seedlings and twin-scales. Bulblets which were produced via both protocols were acclimatized relatively easily. Both explant types could be used to mass propagate Brunsvigia undulata. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.
107

Conservation of the great white pelican (Pelecanus onocrotalus) and the pink-backed pelican (P. rufescens) in south eastern Africa.

January 2006 (has links)
Of the seven pelican species found world wide, only the Great White Pelican (Pelecanus onocrotalus) and the Pink-backed Pelican (P. rufescens) are found in Africa. The KwaZulu-Natal province of South Africa supports only one breeding site for each of these species, and both sites represent the southern most breeding colonies for the two species in the eastern region of Africa. These nesting sites fall within the Greater St Lucia Wetland Park, and are afforded a degree of protection, but the same is not true for their foraging and dispersal ranges, and this is a cause for concern. Considerable amounts of data have been collected relating to the status, distribution and breeding efforts of these two species in north eastern KwaZulu-Natal. These data have been collected in a variety of ways by a large number of people. Part of this work represents an attempt to collate and summarise these data to produce an estimation of the status, distribution and breeding success of these species, and to evaluate any trends in their demography. For this south eastern region of Africa I estimated the population for the Great White Pelican to range between 6000 and 9000 individuals, and the Pink-backed Pelican to range between 600 and 900 individuals. Pelicans are highly mobile birds, and this allows them to move considerable distances when they forage, disperse or migrate. They are also long-lived birds with few natural predators. The two pelican species in south eastern Africa have been poorly studied and little is known about their movements, population dynamics and causes of mortality. Habitat change poses a potential threat to pelicans in north eastern KwaZulu-Natal, and habitat loss could drive these species out this region to areas north of South Africa. Much of this north eastern region of KwaZulu-Natal is under threat, mainly through the actions of man. Many areas are naturally unsuitable for pelican foraging, while others are vital to the survival of both species. This study includes an attempt to assess the movements of these two species in south eastern Africa, and to assess the relative importance and condition of the potential pelican habitat in the north eastern KwaZulu-Natal region, focusing particularly on Lake St Lucia and the Pongolo River floodplain. All this is necessary to produce a baseline from which long term predictions of potential pelican species survival can be made. In the absence of documented life tables and environmental variability data, a range of parameters was modelled to generate population viability analyses to simulate possible scenarios. These extinction models show the outcomes of both the deterministic and the stochastic processes. An attempt was also made to identify the factors that impact most severely on the persistence of these two species. The models were most sensitive to variation in survivorship in the first year of life and to the frequency of catastrophes. Changes in these parameters had the greatest effect on extinction risk. In January 2004 Lake St Lucia was reduced to a fraction of its normal capacity as a result of a severe drought in this region of KwaZulu-Natal. After rains in the area the lake level rose and then fluctuated considerably over the next 24 months. During this time the mouth of the estuary into the sea was closed. Great White Pelican numbers and lake levels were monitored throughout this period. This part of the study relates the changes in population numbers to the lake conditions, and highlights the importance of the lake to this avian species. It uses lake levels as a proxy for the conditions of wetlands in the Lake St Lucia region. It also addresses the implications of these relationships to the management strategy of the lake and the conservation of some avifauna. To identify conservation concerns for the Great White and Pink-backed Pelicans it was necessary to generate these baseline estimations. Although much of this information is uncertain for these two species, an attempt has been made here to predict the persistence of these species in north eastern KwaZulu-Natal and to highlight the conservation issues related to their future. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006
108

Wildlife rehabilitation in South Africa.

January 2009 (has links)
Wildlife rehabilitation, defined as “providing temporary care to injured, ill and orphaned wild animals with the goal of releasing them back into their natural habitat”, developed in response to the increase in human population and urbanisation. Widllife rehabilitation centres developed to deal with casualties from man-made hazards; and because rehabilitation involves human emotions of empathy and compassion, the activity has not tended to be the domain of wildlife specialists, but of concerned members of the public. This has caused concerns for wildlife specialists over the welfare of animals being rehabilitated, because making decisions based on emotions may result in an animal being kept alive under unethical conditions, instead of being euthansed. Furthermore, there may be negative impacts on conservation, as it could divert money away from habitat protection and may place wild populations at risk from disease and genetic pollution. This dichotomy in opinion is most often seen between rehabilitators, who focus on the individual animal, and government wildlife officials, who grant them permits, and who focus on the security of entire communities. Although the value of wildlife rehabilitation cannot be underestimated, in terms of its service to wildlife and the public, there is a need to evaluate whether wildlife rehabilitation may result in more rather than less animal suffering and have a detrimental impact on the existing wild populations. I thus set out to determine the efficacy of wildlife rehabilitation, particularly in South Africa. In the first assessment of rehabilitation centres in South Africa, 65% known centres (n = 63) from all nine provinces returned questionnaires. Several thousand injured, diseased and orphaned animals pass through these centres each year, clearly showing the need for rehabilitation centres in South Africa. However, due to lack of scientific research on the efficacy of rehabilitation methods of care and release, and minimal post-release monitoring, I found that experience and intuition drove most rehabilitation practices. Additionally, because personnel from most centres cited lack of finance as a main impediment to the goal of rehabilitation, the result of rehabilitation may include negative affects on individual animal welfare and survival, as well as on conservation efforts for wildlife communities. Thus, I suggested wildlife rehabilitation be centralised to a provincial or national government. Furthermore, I suggested that guidelines of minimum standards should be developed in consultation with experienced rehabilitators, veterinarians and conservation scientists; to be enforced by trained and dedicated conservation officials. To gain further insight into the need for wildlife rehabilitation in a community in South Africa, I decided to examine four-years of intake records from a large rehabilitation centre in the KwaZulu-Natal Province for trends. Animal intake rate was high (2701 ± 94 per annum). Most of the intake (90%) was birds, with few mammals (8%) and reptiles (2%), and most of these were of locally common species (eg doves, pigeons). This reflects the findings of other studies, namely that species living in close association with humans are the most frequently admitted to rehabilitation centres. In total, most of the animals admitted (43%) were juveniles, which were assumed to be abandoned or orphaned. The implications of then rehabilitating these juveniles, which were largely uninjured, is whether humans should be interfering with nature if the cause was not human-related; can each juvenile (especially in these large numbers) be adequately prepared to survive and thrive when released into the wild; and is there space in the environment for them, without causing harm to others already in the environment. I suggest that the large numbers of animals currently being admitted to the centre may be reduced, possibly through increased public education particularly to leave uninjured juveniles in the wild. Furthermore, improvements in the centre’s recording system may allow for use in funding requests and for various research opportunities. There is a general lack of post-release monitoring in wildlife rehabilitation, and the IUCN advises that confiscated and orphaned animals should be euthanased or placed in life-time captivity. I thus decided to document the post-release fate of rehabilitated vervet monkeys and leopard tortoises, two species commonly admitted to a rehabilitation centre, and rock hyrax (Procavia capensis), as a further case study, even though individuals were not from a rehabilitation centre. Success of releasing rehabilitated animals cannot be judged on whether it results in a self-sustaining population, as in reintroductions, as it is to improve the welfare of that particular animal, independent of its species’ status. Survival is thus the most basic indicator of a successful rehabilitation release. Other aspects, such as behaving similarly to a wild animal, are additional success factors, as they likely influence survival. Although after one year post-release, the two troops (T1 = 35, T2 = 24) of vervet monkeys (including an infant) survived, were independent of human food provision and companionship, had established in an area, and had births in the breeding season following release; low known survival (T1 = 11%, T2 = 50%) make it difficult to designate these releases as successful. However, it was clear that the two groups of rock hyrax released were not successful. The group of rock hyrax that had previously been in captivity for 16 months (n = 17) did not have site fidelity after release, and after three months could not be found. All wild rock hyrax (n = 9), except one whose fate is unknown, were found dead, mostly predated, within 18 days. The release likely failed due to predation. For both vervet monkeys and rock hyrax, a lack of social cohesion was suggested as causing the group to dissolve or split upon release, which in turn would increase their vulnerability to predation. Recommendations are provided for considerations in future releases of captive vervet monkeys and rock hyrax. Movements of two groups of tortoises (ten and seven individuals) released at two different sites were monitored over a year, using radio-telemetry. In total, one tortoise was returned to captivity because of disease, four were killed intentionally or accidentally by humans, three others died due to a combination of disease, starvation and/or dehydration, and the fate of six were unknown. Since only two out of seven tortoises survived 13 months after release and only one out of ten tortoises were known to have survived 25 months after release, rehabilitated leopard tortoises were not successfully released into the wild. Recommendations to improve the success of future releases are provided. The occurrence of disease in the tortoise release was a worrying result, and must be addressed before any further releases are allowed. To summarise, there is a dichotomy between wildlife rehabilitation and conservation throughout the world, but this study highlighted the situation in South Africa. The IUCN guidelines for the reintroduction, introduction and supplementation of animals make it clear that there are many threats to the individual animal, to the release environment and to the conservation of species when transporting and releasing animals, especially if they had been in captivity. I believe that I have presented enough evidence in the thesis to suggest that wildlife rehabilitation may result in negative consequences to the welfare of the individual being rehabilitated and to the wild conspecifics or to other species in the release site. I suggest that wildlife rehabilitation needs to move away from being an emotional-based “animal-rights” organisation, to being objectively managed, such that no harm is caused to conservation by these efforts. This may require them to change their constitution so they are aligned with the IUCN guidelines, where more consideration is given to the possible risks involved in releasing animals. However, the applicability of the IUCN guidelines will vary slightly according to the species and situation, and they require input from the local conservation authorities (as was the case in the studies documented in this thesis). I suggest that the public be educated as to the risks that wildlife rehabilitated animals can pose to the safety of the environment as a whole, and that rehabilitated animals do not necessarily survive or thrive in the wild when released, and thus they have to understand that rehabilitation centres will sometimes have to prioritise casualties for treatment, and euthanase exotic species. In conclusion, implementing further research in ensuring long-term post-release survival of rehabilitated animals; developing and enforcing practical guidelines/minimum standards by dedicated and qualified governmental wildlife conservation officials; and having examinations in order to qualify as a wildlife rehabilitator, will ensure humans are “making amends” instead of having an additional negative impact on conservation and animal welfare. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009
109

The effect of land use on the species composition of amphibians in North Eastern KwaZulu-Natal.

Russell, Charlene. January 2010 (has links)
Global declines in amphibian species have directed research towards investigating why this is happening. One of the major causes of these declines is the fragmentation and loss of habitat. This study examined the effect of land use on the species composition of frogs within North Eastern KwaZulu-Natal, and the use of buffer zones to facilitate the protection of these species. Three land use types were investigated: sugar cane (Saccharum officinarum), gum (Eucalyptus sp.) plantations and conservation areas. The average number of frog species differed between areas: conservation 13.2 ± 6.6; plantations 3.8 ± 1.3; and sugar cane 2.8 ± 1.4. Sugar and gum plantation were found to be lacking the wetland and grassland/woodland habitats. In addition to this, the frog species that were not present on these land use types were those that are totally dependent on water as well as those that are not dependent on a water source. Two species were highlighted as possible indicator species of land use: Amietophrynus gutturalis and Hyperolius marmoratus. To mitigate the effect of these land use types, the use of buffer zones was explored in a desktop study. A range of buffer zones were applied to wetlands in a sample study area, using a range of distances including the distances of 290 m and 159 m recommended by Semlitsch and Bodie (2003), and the recommended distances for wetlands in South Africa of 10-20 m. The application of a 290 m and 159 m buffer zone on a conglomerate of wetlands connected by a 100m buffer was the most feasible as it incorporated a percentage of the total study (6.4% and 4.3%) area similar to the percentage occupied by the recommended 20m buffer zone (5.5%) around all wetlands, and still incorporated the range under protection put forward by Semlitsch and Bodie (2003). Management implications of these findings are discussed. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.
110

A modelling approach for determining the freshwater requirements of estuarine macrophytes.

Wortmann, Joanne. January 1998 (has links)
Increased abstraction of water in the catchment results in a reduced or altered pattern of river flow and this holds serious consequences for the downstream estuarine ecosystem. In South Africa this is a serious concern because freshwater is in limited supply and the demand for freshwater can be expected to increase in the future. A large multi-disciplinary consortium of South African scientists are working on projects to determine the freshwater requirements of estuarine ecosystems. As part of this, this thesis reports on research undertaken to develop mathematical models to determine the freshwater requirements of estuarine macrophytes. Three key macrophytes are selected. The macrophytes are Zostera capensis Setchell, Ruppia cirrhosa Grande, and Phragmites australis. They are common macrophytes in South African estuaries. Zostera and Ruppia are submerged macrophytes and Phragmites is an emergent macrophyte. They have different freshwater environments and therefore respond differently to alterations in freshwater flow. A first order differential equation model is used to determine the effect of different combinations of open and closed mouth conditions of the estuary on Zostera and Ruppia. The scenarios are selected to determine whether achieving a switch in states from a Zostera-dominated estuary to a Ruppia-dominated estuary is possible. To predict encroachment rates and colonisation patterns, a cellular automaton of the vegetative spread of existing Zostera beds is developed. After analysing various scenarios accounting for both an increase and a decrease in freshwater supply, the cellular automaton is extended to include interactions between Ruppia and Phragmites. The multi-species model is applied to the Kromme estuary, South Africa and the Great Brak estuary, South Africa. Various freshwater scenarios are examined from the natural runoff condition to the situation of no freshwater inflow. A sensitivity analysis of the spatial model with Zostera, Ruppia and Phragmites is conducted. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1998.

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