Biochemical responses of insects to environmental challenges: implications for gas exchange and pest control
| Leigh Boardman (lboardman@sun.ac.za) |
Broadly, my project is aimed at integrating insect physiology and biochemistry to gain a further understanding into the mechanisms of insect thermal tolerance under modified atmospheres. The results of this study will have direct applications for post-harvest control of insect pests in the citrus and deciduous fruit industries.
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Ecology of the false codling moth (Thaumatotibia leucotreta) (Meyrick) in deciduous fruit orchards and vineyards
| Zoe de Jager (zoe@sun.ac.za) |
False codling moth (FCM) is a major pest on deciduous fruit, grapes and citrus. The pest has been studied in many capacities over the last few decades, although much of the research was focussed on citrus as host and the control of FCM. Its ability to utilize a wide range of hosts, planted and non-planted, is threatening the fruit industry. In light of recent developments in the fruit industry with regard to incidence of what is assumed to be high false codling moth-induced fruit damage, it is apparent that research is required on the taxonomy, biology and ecology of false codling moth on deciduous fruit. There is an extreme lack of published information on this very important pest, which has hampered management practices severely. The aim of this project is to collect relevant field-based data on the occurrence of fruit damage, host selection and associated biology. The first objective of this study is to do a life table study in the laboratory, determining parameters such as upper, lower and optimal developmental temperatures for different life stages; and fecundity, adult longevity and egg development at five different temperatures. The second objective is to determine diapause in FCM. Can it go into diapause? Can the conditions conducive to diapause be created under lab conditions, also setting up a lab protocol to initiate diapause. The last objective would be to study the field flight ability of FCM males, using a mark- recapture method. Flight distances and temperature patterns will be analysed. This information can be incorporated into the current Sterile Insect Technique programme, in order to improve efficacy of the release method.
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Assessing the effects of invasive alien plants on the livelihoods of rural land users on the Agulhas Plain, Western Cape, South Africa
| Samantha de la Fontaine (samdlf@sun.ac.za) |
I completed my bachelors in Conservation Ecology at Stellenbosch University in 2010. I am currently busy conducting my master’s research at the Department of Conservation Ecology & Entomology. My MSc research is titled “Assessing the effects of invasive alien plants on the livelihoods of rural land users on the Agulhas Plain, South Africa” and is funded by the DST-NRF Centre of Excellence for Invasion Biology (C.I.B). The research primarily focuses on the impacts (both negative and positive) of IAPs on the livelihoods and well-being of local communities, as the use of these plants by rural communities is not well understood and rarely incorporated into control programmes. The project is aimed at investigating the spread and impacts of IAPs in the rural parts of the Agulhas Plain as well as the perceptions, uses, costs and benefits associated with IAPs and the importance of these plants to the livelihoods of the local communities.
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Holistic Management: Considering “wholes within wholes” in rangelands
| Ancois Carien De Villiers (ancois@sun.ac.za) |
The modern world faces a multitude of dire challenges with an increasing environmental crisis disrupting human societies. One of the main causes for this degradation is the poor management of natural resources.
Conventional management and research is characteristically reductionist in nature. The reductionist approach is based on the observation that “the system is equal to the sum of its parts”. It is linear, rigid and allows us to comprehend, quantify and predict complicated systems. This approach has been fundamental to major advancements in technology, but appears to be failing when applied to complex systems such as rangeland ecosystems which are are notoriously unpredictable with dynamic multiple non-linear relationships.
Recently there has been a marked shift away from reductionism to holism. Holism is based on the concept that “a system is greater than the sum of its parts”. This approach views systems as “wholes” functioning within greater “wholes”.
Holistic Management (HM) is a decision-making framework built on the philosophy of holism. According to Allan Savory, the Zimbabwean founder of HM, land managers must introduce holistic principles to their decisions to ensure that they simultaneously consider ecological, social and economic implications on different temporal and spatial scales. Despite its potential, past research on HM has been limited, controversial and mostly reductionist in nature.
The proposed study aims to determine if there is scientific evidence for the beneficial claims of HM by using a more holistic approach than in the past. The objective will be to establish if HM practitioners are more resilient and adaptable than non-HM practitioner. Data will be collected through interviews and field surveys. The study can contribute insights on how to manage complex systems more sustainably.
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Morphology and ecology of the Carob moth Ectomyelois ceratoniae (Lepidopters:Pyralidae)
| Petrus Paulus Heinrich de Wet (pphdewet@sun.ac.za) |
Aims: To determine the morphology of local populations, biology and pest status of the Carob moth and other fruit boring moth pest, in particular false codling moth in citrus
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An assessment of the potential of irradiation as a postharvest control treatment against the banded fruit weevil, Phlyctinus callosus (Coleoptera: Curculionidae): effects on adult weevils and host crop, ‘Flavor Fall’ plums.
| Andries Johannes Duvenhage (andriesduv@sun.ac.za) |
The banded fruit weevil (Phlyctinus callosus) is a major pest of pome and stone fruit in South Africa. Due to a very limited geographical distribution, it is a pest with huge phytosanitary risk for many countries importing South African fruit. Postharvest control technologies such as irradiation treatments are becoming increasingly accepted as alternatives to previously used chemical treatments. The aim of this project is to investigate the effect of irradiation on the reproductive capacity of banded fruit weevils, as well as the effect of such a treatment on the quality of a host plant species affected by weevils. Results indicate that sterility of the banded fruit weevil can be achieved at doses as low as 80 Gy, and even at doses as high as 1400 Gy, the quality of the fruit is still above the minimum standards for the export markets. Thus, irradiation has good potential to be developed as a postharvest control treatment against P. callosus, as dosages that will control weevils will not adversely affect host fruit quality
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Development of a habitat management plan for vineyards, with focus on biological control of the vine mealybug
| Sariana Faure (sariana@sun.ac.za) |
Planococcus ficus is a major pest of grapes in South Africa. It is a carrier of the grapevine leafroll virus and is difficult to control due to its cryptic nature. Currently, biological control using Coccidoxenoides perminutus is being used in augmentative release efforts. However, the combined use of C. perminutus with another major mealybug parasitoid, Anagyrus sp. near pseudococci should be investigated. These two parasitoids differ in their biology, preference of P. ficus instars and optimal development temperature, which means overlapping but different times of occurrence during the season. However, many of these studies were not done in South Africa and none were done to compare these two parasitoids in the laboratory on P. ficus. The aim of this study is to investigate the possible interspecific host discrimination and the competitive relationship between the two parasitoids and as a result determine the viability of using a multi-species release in vineyards. The overall outcome of this study will shed more light on how competition might affect P. ficus populations in biological control efforts and what can be expected if both parasitoids are commercially released. Research has also found that parasitoids are found in greater abundance on vineyard weeds than planted cover crops, which would indicate that they prefer a more diverse habitat of flowering plants. Plant species that were shown to be useful for improving parasitoid longevity, fecundity and parasitism ability include Jasminum spp., Borago spp., Agapanthus spp., Phycelia spp., Alpinia spp. and Fagopyrum spp. We aim to find suitable indigenous species related to these, if available, to determine which plants are suitable alternative plant resources in a vineyard habitat management plan for the improvement of biological control of P. ficus.
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Fynbos riparian zones: investigating the effects of invasive plants on denitrification in invaded and cleared areas under field and laboratory conditions and implications for riparian functioning.
| Marthinus (Marno) Jacobus Fourie (marnof@sun.ac.za) |
Fynbos riparian zones are heavily invaded by invasive alien woody plants such as Acacia mearnsii. Invasive Acacias are nitrogen-fixers that influence the ability of riparian zones to provide ecosystem services such as nutrient cycling by increasing nitrogen input to the system (Jovanovic et al., 2008). They may also change the functioning of riparian zones as a sink (e.g. retaining NO3- - N through denitrification in the soil) to a source of nitrogen (e.g. releasing NO3- - N to the soil or groundwater or N2O and/or N2 to the atmosphere). There is uncertainty of what actually happens to the added nitrogen in these invaded systems; Is organic nitrogen actually converted to N2O and/or N2 or is it deposited into the river or groundwater in the form of NO3- - N from the soil profile or litter fall? It is therefore important to investigate the effects of invasion by non-native species, because they are one of the major drivers responsible for global change (Evans et al., 2001).
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Ranging pattern, habitat use and feeding preference of reintroduced Southern white rhinos, Ceratotherium simum simum, in Moremi Game Reserve, Botswana
| Pearl Galebotswe (15274225@sun.ac.za) |
The primary aim of the Botswana rhino reintroduction programme is to establish a genetically viable breeding nucleus of both white and black rhinoceros in a historically ranging area from which the species have been absent for a number of decades. Should the programme be successful the generated offspring will be relocated to other suitable areas.
The second aim of the reintroduction programme is to promote the conservation of these rare and endangered species by promoting ecotourism and by involving local communities in the areas neighbouring Moremi Game Reserve. From a management perspective, it is essential to understand the ecology of the species including: habitat use, feeding preference, and home range and territory establishment. This project aims to fill these knowledge gaps.
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The use of expert knowledge in conservation planning
| Craig James Galloway (galloway@sun.ac.za) |
| Supervisor: Dr Andrew Knight |
Systematic conservation planning is an ever evolving field of study. It is the basis for all land use management and conservation decision making processes in South Africa. Therefore it is important to understand and know the best possible way to collect data in order to most effectively prioritize areas for conservation of biodiversity, which will lead to practical implementation. Historically conservation planning has followed a very systematic and strategic approach. A problem arises when the research takes too long for an effective and practical conservation plan to be produced. Expert knowledge provides a more accessible and cheaper way to collect data. Expert knowledge and opinion is used extensively in conservation planning, but has not been properly studied or tested. I plan to test how reliable expert knowledge is and how to go about best capturing this knowledge. A literature review, expert workshop and a comparison of expert gathered data with systematically gathered data will be carried out. This will provide an understanding of the usefulness, limitations and best practise of gathering expert knowledge for systematic conservation planning. The outputs from this study will be the development of a framework for determining when, where and how expert knowledge is best gathered and applied and a framework for integrating systematically collected data and expert knowledge for spatial prioritization.
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The recovery of insect – plant interactions after removal of pine plantations with a focus on insect pollinators.
| Muhammed Nizaar Gardee (mngardee@sun.ac.za) |
Pine trees are sometimes conceived as a “softer” form of disturbance to natural areas particularly as forestry companies are trying to decrease the impacts of silviculture practices with FSC certification as “environmentally sensitive forestry” and with restoration projects. With these practices in mind, how does forestation impact on the indigenous insect and plant populations in the Cape Floristic Region (CFR) - an area in which pine trees are an alien introduced species?
The CFR is one of the world’s top 24 biodiversity “hotspots”. I am researching a previously pine afforested site now restored to fynbos (the major vegetation biome of the CFR) to uncover the revival of plant insect interactions, with a focus on insect pollinators.
My study comprises a sampling of insect pollinators using both a sweep net and a pan/flight intercept combination trap. These catches will be correlated to a vegetation analysis of the area over which the insects were caught.
Failing a recovery of normal pollinator diversity, there may still be a significant level of visitation as more robust “generalist” insects are known to be the more likely visitors on many rare plants.
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Oxygen-water trade-offs in discontinuous gas exchange in Orthoptera
| Berlizė Groenewald (berg@sun.ac.za) |
This study will aim to link the mechanisms controlling insect gas exchange patterns, particularly DGE variation, with environmental variation. The major question that will be addressed is whether trade-offs between water regulation and oxidative damage influence gas exchange patterns and DGE variation.
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Controlled atmosphere temperature treatment systems (CATTS) as a postharvest treatment for phytosanitary pests of deciduous fruit
| Gustav Groenewald (gustavg@sun.ac.za) |
My project is aimed at developing an environmentally friendly postharvest treatment using the combination of temperature and atmospheric gasses to control a variety of phytosanitary pests.
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Nematode community structures as bio-indicators of agricultural soil health under local conditions
| Caro Kapp (ckapp@sun.ac.za) |
Soil is a fundamental, non-renewable resource in any ecosystem. It is imperative to develop ways in which to ensure the continued biological productivity of agricultural soils for sustainable food production, necessary for an increasing human global population. This has prompted the search for appropriate biological indicators for measuring soil health. Nematodes are one of the most abundant Metazoa in all soils and form an integral part of the soil food web. They respond rapidly to changes within their environment, can be easily extracted from the soil, identified and characterized into functional guilds. Indices that have been derived through the analysis of the nematode faunal profile, can impart information as to the condition of the soil or disturbances which might have occurred. This gives nematodes the ability to act as bio-indicators of soil health. As of yet, little research has been done to determine the nematode community structures in agricultural soils, especially deciduous fruit orchards. The main objective of this study is to determine whether nematodes can be used as bio-indicators of soil health in orchards. This will be investigated by (1) determining the frequency and diversity of nematode families in populations; (2) differences between nematode communities in commercially and organically managed orchards; (3) sampling of natural habitat types such as Fynbos and (4) using the different functional and trophic groups in a nematode faunal profile model for interpretation of the data. The results gained from this work will indicate whether a nematode faunal profile model can be routinely used as a measure of soil health for local soils.
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Population genetics of the Mediterranean fruit fly Ceratitis capitata in South Africa at different spatial scales
| Minette Karsten (minettek@sun.ac.za) |
Ceratitis capitata Wiedemann, the Mediterranean fruit fly (Medfly), is a highly invasive species throughout the world and considered as one of the most successful agricultural and economical pests. The increase of global trade in fruit and human travel combined with the biology of Medfly has allowed the species to spread from its origin in Kenya, East Africa, to a number of locations throughout the world. South Africa has been implementing different methods to control fruit fly populations, including the Sterile Insect Technique (SIT). An SIT program requires some knowledge of the population structure and the degree of connectedness between pest-occupied sites. The identification of sites from which re-invasion is most likely to occur and knowledge regarding the primary routes through which pests are likely to re-establish are critical questions. This project aims to use genetic markers as tools to determine dispersal in Medfly at local and regional scales in South Africa.
Climate change and tsetse flies: physiology and distribution modeling
| Elsje Kleynhans (elk@sun.ac.za) |
Climate change will alter both temperature and moisture availability in the future and therefore is likely to affect vector borne disease (VBD) prevalence. However, cause-and-effect links between climate change, vector population responses, and changes in risk of disease transmission are poorly established for most VBDs. Here we use a major African disease vector, Glossina pallidipes, as a case-study to demonstrate the use of a biophysical mechanistic model to address these issues.
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Post-fire regeneration of mountain fynbos: Exploring the “persistence niche”
| Karen Edith Marais (bkrj@sun.ac.za) |
Fire is a natural occurrence in Mediterranean type climate regions. The plant species that naturally inhabit these regions have traits that facilitate their persistence under a given fire regime; however, fire regimes are changing due to climate change, invasive species, and anthropogenic ignitions. Thus, understanding how native vegetation responds to fire will become increasingly important. The relationships between post-fire resprout success, life history type, and plant functional traits were examined in the southwestern Cape as part of a larger study examining post-fire recovery in sprouting plants in the Mediterranean type climate regions of California and South Africa. Shrubs of two different life histories were examined: Obligate sprouters, which have to resprout to persist because their seeds are killed by fire, and facultative resprouters, which both recruit seedlings and resprout after fire. The aim of this study is to find predictors of resprout success and to see if there are significant differences between obligate and facultative resprouters. Results on mortality and survivorship from post-fire fynbos data show that there was a significant difference in post-fire resprout success between obligate sprouters and facultative sprouters, with a near 100% resprout success of the obligate sprouters, compared to 65% for facultative sprouters. Individuals from obligate sprouter species all sprouted within the first four months post fire, while some individuals from facultative sprouting species were still sprouting a year after the fire. Obligate sprouters had greater relative growth rates than the facultative sprouters, reaching half of their maximum growth over two years in only 184 days compared to 277 days for obligate sprouters. Facultative sprouters were more water stress resistant (measured as xylem cavitation resistance) than obligate sprouters, suggesting a tradeoff between water stress resistance and resprout success.
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Fynbos riparian biogeochemistry and invasive alien Acacias
| Minette Naudé (mnaude@sun.ac.za) |
Riparian ecotones, transitional areas between upland terrestrial communities and aquatic ecosystems are well known for their distinctive and intrinsic ecological properties and functions relating to biodiversity, productivity and biogeochemistry. Displacement of woody and understory vegetation by woody invasive alien plants is hypothesized to change plant-soil interactions. Since riparian ecosystems play a vital role in maintaining ecosystem services and function, understanding the level of invasion and degradation and associated changes in ecosystem structure and function is essential for successful restoration. The general objective of this study was to identify and elucidate the relationships between soil properties, soil biogeochemical processes and plant functional diversity in natural, invaded and cleared riparian ecotones and associated upland terrestrial fynbos. Within the south-western Cape of South Africa, fieldwork was performed in the mountain stream and foothill sections of six different perennial river systems where sites with dense invasion, cleared, and reference sites may be found. Four of the sites are natural, four have been invaded by mostly nitrogen-fixing Acacia mearnsii (also A. longifolia), and three are sites that have been cleared of Acacia species (predominantly A. mearnsii) more than five years ago. At each site, 4-5 replicate plots were selected for each zone (wet bank, dry bank, and terrestrial zones). Soil samples were collected on a seasonal basis and analyzed for selected parameters. Ground Cover and Canopy Cover were used in this study for defining the level of influence of the different growth form classes. Highly significant correlations were found between variables (EC, texture, available nitrogen, acid phosphatase, total- nitrogen and carbon). Invasion affects soil physical and chemical properties (EC, and particle size distribution), increases nutrient concentrations (Total- nitrogen and carbon, available- nitrogen and phosphorus), alters nutrient cycling processes (acid phosphatase), and changes vegetation structural complexity. Soil properties in riparian dry bank zones do not differ from terrestrial zones.
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The hydrological effects of alien invasion and subsequent restoration: a case study of the Kromme River System, South Africa
| Alanna Rebelo (arebelo@sun.ac.za) |
The coastal city of Port Elizabeth in the Eastern Cape of South Africa is in the midst of a water crisis and is searching for ways to augment its water supply, and achieve water security. Port Elizabeth currently obtains roughly forty percent of its water from the Kromme River Catchment. Farmers have occupied the Kromme River Catchment since the eighteenth century. However it was not until after the 1940’s, driven by growing economic pressures, that unsustainable farming practices increased. Activities altering the catchment included over-grazing, alteration of flood plains for crop production, planting of alien trees (mainly Acacia mearnsii), canalization of the river, straightening of the river, building infrastructure through and alongside the river, mechanical damage to the wetlands (ploughing) and the removal of palmiet (Prionium serratum). In 1996, Working for Water commenced restoration in the Kromme River Catchment. Since then restoration has comprised two approaches; firstly the construction of gabions to prevent further erosion from headcuts, and secondly the clearing of A. mearnsii from the river bed and flood plains. If it can be shown that the continuing land degradation in the Kromme River Catchment is reducing the quantity and quality of water that could be available for human consumption, the municipality may focus more efforts on restoring the catchment. This study aims to investigate the impact of restoration on several ecosystem services, including provisioning (water flow) and regulating (water purification, assurance of supply, erosion control, flood attenuation) services. This will be done using the Agricultural Catchments Research Unit (ACRU) Model. The ACRU Model is a physical-conceptual model that requires detailed data input on a daily time-step. The central hypothesis is that the restoration of natural capital in the Kromme River Catchment has and will improve river flow, yield, water quality, erosion control and flood attenuation.
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Morphology and Taxonomy of Tortricid moth pest attacking deciduous fruit and citrus
| Monique Rentel (mrentel@sun.ac.za) |
The largest family of the micro-lepidoptera is the Tortricidae, also known as the leafroller or twister family, and contains some of the most important agricultural pest species worldwide Seven major economically important tortricid species can be found in South Africa, with great impact on the local fruit industry. These seven species are Cydia pomonella (Linnaeus, 1758) (Codling moth), Thaumatotibia (Cryptophlebia) leucotreta (Meyrick, 1913) (False codling moth), Grapholita molesta (Oriental fruit moth) (Busck, 1916), Cryptophlebia peltasitica (Meyrick, 1921) (Litchi moth), Thaumatotibia batrachopa (Meyrick, 1908) (Macadamia nut borer), Epichoristodes acerbella (Walker, 1864) (Pear leaf roller/carnation worms), and Tortrix capensana (Walker, 1881) (Apple leaf roller). The larvae of all these species feed on a range of cultivated crops causing extensive damage and losses to the fruit industry.
Currently no proper taxonomic key is available to identify the particular individual species and life stages to enable correct identification for scientific and applied workers. Thus the aim of the thesis is to establish an easy referencing system for Tortricid moth pests of fruit, including the construction of taxonomic keys of all life stages and associated morphological and biological information. Focus will be given to the False codling moth as it is currently regarded as the most economically important tortricid due to its extensive range of host plants and quarantine issues relating to fruit exports.
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Sustainability Indicator Development for UNESCO Biosphere Reserves
| Colin Micheal Tucker (colt@sun.ac.za) |
Biosphere reserves consist of areas of both terrestrial and coastal/marine ecosystems. These reserves are internationally recognised through UNESCO’s Man and the Biosphere programme, forming the so-called World Network of Biosphere Reserves. One of the main goals of Biosphere Reserves is to act as both theatres and laboratories of sustainable development, thus encompassing environmental, social and economic values. Sustainability indicators are thus needed in order to implement a framework for monitoring and evaluation within biosphere reserves.
Through a literature review of sustainability indicators and their development, as well as a series of participatory, multi-stakeholder workshops, surveys, interviews and focus groups, this project aims to develop sustainability indicators for the Kogelberg and Cape West Coast Biosphere Reserves in the Western Cape, South Africa. Ultimately, a national standard for monitoring across South Africa’s six biosphere reserves will be established. The final results of this study will be integrated into a draft framework plan which will be used by the reserves as a tool for monitoring and evaluation.
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In vivo production of Heterorhabditis zealandica and Heterorhabditis bacteriophora
| Carolien van Zyl (lien@sun.ac.za) |
Worldwide, more emphasis is placed on adapting environmentally friendly agricultural practices to conserve arable land, whilst efficiently producing crops for the ever-increasing global population. As a component of an Integrated Pest Management (IPM) Programme for crop production, entomopathogenic nematodes (EPNs) have been identified as promising biological control agents against key insect pests. EPNs are commercialized in some countries, but are not yet available on the South African market as formulated biological pest control products. The approach of this project is to develop an in vivo nematode production process, using two endemic nematode strains, H. zealandica (SF41) and H. bacteriophora (SF351), whose host range include pests like codling moth, false codling moth, maize stalk borer, sugarcane borer, mealy bugs and weevils. Means are explored to enhance and streamline existing production practices. This should contribute to the creation of an effective, cost-efficient and practical recipe that could be implemented by research laboratories, niche markets, grower cooperatives and other commercial areas where lack of capital and infrastructure do not justify large investment in in vitro (large-scale) nematode production.
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Assessing the impacts of invasive alien plants on grazing provision and livestock production
| Thozamile Yapi (16937023@sun.ac.za) |
Invasive alien plant species are a serious ecological problem in South Africa, and considerable work has been done to improve our understanding and in turn inform their effective management. Much of South Africa is under livestock production, and this important industry sustains many rural economies. In arid regions of South Africa species like Prosopis sp, Acacia sp., have invaded extensively and are a particular concern to the agricultural industry. The impact of invasive alien plants on this industry as received limited attention.
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About CAKE (Conversations About Knowledge and Ecology)
CAKE is an informal research forum for postgraduate students in the Department of Conservation Ecology & Entomology. The monthly meetings allow students to share ideas and experience, learn about each other’s research and discuss current issues in research, conservation and ecology in an informal and stimulating environment. The CAKE forum is run by the postgrads, for the postgrads and anyone is free to propose topics for discussion, ask advice, present their own work for review by their peers, or start a debate on current hot topics in science, the environment and conservation. Outside speakers are also invited to share their practical knowledge and experience. Ultimately CAKE aims to produce better researchers though interaction and exposure to the ideas and experience of peers and experts in the fields of conservation ecology and entomology. Oh, did we mention that there will also be cake…
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