Masters Degrees (Plant Sciences)
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Browsing Masters Degrees (Plant Sciences) by Advisor "Du Preez, P. J."
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Item Open Access The invasion potential of selected Berberis species in South Africa(University of the Free State, 2015-01) Keet, Jan-Hendrik; Du Preez, P. J.; Visser, B.; Cindi, D.English: Invasive alien species are a serious threat to global biodiversity. They have considerable negative effects on the economy and the environment, using up valuable natural and monetary resources. Every year new species are introduced into South Africa and with that the list of potentially new invasive species grows. These emergent invasive species should receive a very high priority in terms of assessing their invasion potential and possible impacts. No formal study has been conducted regarding the invasion potential of any species in the genus Berberis within South Africa, even though it has been a popular horticultural genus for many decades and is known to have invasive species. The current study focussed on four key points, namely: 1) the elucidation of all Berberis spp. that have been historically and are currently cultivated within South Africa, 2) assessing the size, extent and reproductive age of any naturalized/invasive Berberis populations, 3) determining potential habitable areas of naturalized/invasive Berberis species and 4) determining whether any Berberis species should be officially listed under the National EnvironmentalManagement Biodiversity Act. A total of 30 Berberis species/cultivars/hybrids were found to have been cultivated in South Africa in the past and present (11 species, 11 cultivars, 8 hybrids). Three of these species are widespread invasives in other parts of the world, namely B. darwinii, B. thunbergii and B. vulgaris. The KwaZulu-Natal Province has the highest diversity of species/cultivars/hybrids stocked by nurseries/private/wholesale growers, while B. thunbergii and B. thunbergii var. atropurpurea were found to be the most widely stocked species. Two invasive Berberis populations were found. The first population was from the species Berberis aristata and occurs in the Woodbush State Forest (Limpopo Province; 23.8192°S 29.9608°E). This population has an extent of occurrence of 115 ha and an area of occupancy of 1.58 ha. A total of 5 725 individuals were geotagged and the population was found to be highly reproductively active, with more than 40% of the population able to flower and set seed. The second population was from the species B. julianae and occurs at the Glen Reenen rest camp in the Golden Gate Highlands National Park (Free State Province; 28.5049°S 28.6187°E). This population has an extent of occurrence of 0.42 ha and an area of occupancy of 0.02 ha. It was also found to be highly reproductively active with 38% of the population able to flower and set seed. A few minor occurrences of this species were found at the Alma Ranger Station, also in the Golden Gate Highlands National Park. A total of 473 individuals of this species were geotagged. Bioclimatic modelling revealed that substantial parts of South Africa are suitable for both Berberis aristata and B. julianae. The former species was found to be more suitable to the mountainous regions while the latter has a higher suitability to the central parts of the country. The situation regarding future climate scenarios (2020) was the same, although a range contraction was found for both species. Weed risk assessments revealed that both B. aristata and B. julianae would have failed a pre-border screening (score of 27 and 22, respectively, according to the Australian Weed Risk Assessment system), indicating that both species pose an environmental risk. Herbicide trial clearing revealed that three chemicals can be used for the successful control of Berberis spp., namely metsulfuron-methyl, triclopyr and glyphosate. The final outcome of the study is the following recommendations: Berberis aristata should be listed as a category 1a invasive species in the National Environmental Management Biodiversity Act, while B. julianae should be listed as category 1b in non-urban areas and not listed in urban areas.Item Open Access An investigation into the possible causes of decline in the Acacia Erioloba population of the Kathu area(University of the Free State, 2001) Van der Merwe, Karien; Du Preez, P. J.; Potgieter, G. P.English: Concerned residents have been reporting a decline in the A. erioloba population of the Kathu area to the Northern Cape Nature Conservation Service (NCNCS) since the early 1980's. This is the third study on this subject initiated by the NCNCS, and aims to elucidate the possible causes of decline in the A. erioloba population of the Kathu area. Five investigation sites were identified: the Khai-Apple Nature Reserve (KANR); the farms Lylyveld and Dernaneng, both situated down-wind with regard to the Sishen lscor Iron Ore Mine (SllOM); the Sishen Golf Course; and the farms Swarthaak and Knapdaar, both situated upwind with regard to the SllOM. The Sandveld Nature Reserve on the Free State side of the Bloemhof Dam, served as control site. In order to identify potential problem areas regarding the A. erioloba population of the Kathu area, the A. erioloba population structure of the study and control areas were compared. Irregularities in the structure of the study area indicated that some factor(s) is either a) preventing individuals from reaching middle height classes, or b) kill ing trees in these classes. To eliminate one of these options, another structure study was conducted, comprising dead individuals only. Results indicated that both factors (a+ b) play a role. By means of questionnares that were distributed th roughout the region, three major factors, potentially harmful to the A. eriofoba population, were identified. They are the mining activities of the SllOM, management strategies and natural phenomena. Two aspects of the SllOM were postulated to be potentially harmful to the A. erioloba population: the mine dust formed as a by-product of mining activities; and the lowering of ground water levels. Scanning electron microscopy confirmed that A. erioloba leaves are indeed damaged by mine dust. Through further investigations the effect of mine dust on the transpiration rate, chlorophyll a and b content and protein content of A. erioloba leaves were determined. The results of this study indicated that mine dust has no marked effect on any ofthese variables. The effect of mine dust on the germination of A. erioloba seeds and the growth potential of its embryos were also determined. No inhibitive effect was detected on either of these processes - in fact, mine dust seemed to stimulate both. No trials regarding the effect of the lowering of ground water levels by the SllOM on A. erioloba were conducted, due to its impracticality. Instead, with the aid and insight of geohydrologists it was concluded that the lowering of ground water levels does not affect A. erioloba. The aquifer underneath the mining area is seperated from the other two aquifers in the area (situated under Kathu and the KANR) by a dolorite dyke, which is impermeable to water. This was confirmed in the present study by comparing the water pumping rates of the SllOM to bore hole levels throughout the region. Three management strategies applied in the Kathu area were identified as being potentially harmful to A. erioloba: the overstocking of browsers and mixed feeders in the KANR; pod removal; and the uninformed use of chemicals. The current stocking rate of the KANR compared to its current browsing capacity, revealed that the reserve is grossly overstocked. This results in the suboptimal regeneration of A. erioloba, as seedlings cannot reach the stage where browsing doen not prove to be fatal anymore. Pod removal also inhibits optimal reg eneration, as no A. erioloba soil seed bank was found. This implies that no genetic variation in the A. erioloba pululation is built up over time, which may prove to be fatal in the event of future changes in environmental conditions. The uninformed use of non-specific chemicals in an attempt to eradicate A. mellifera on farms is furthermore also eradicating A. erioloba. One natural phenomenon was hypothesised to be inhibiting to the regeneration of A. erioloba, namely seed predation by Bruchidae. Germination trials revealed that bruchid seed predation inhibits the regeneration of A. erioloba. It is, however, compensated for by producing a relatively large seed yield per tree in an attempt to over-saturate predators. Management recommendations on the effective management of A. erioloba in the Kathu area were made. Recommendations included correct stocking rates, increasing community involvement in conservation, veld monitoring and the correct use of chemicalsItem Open Access Phytosociological study of the riparian and associated wetland vegetation along the Vet River, Free State Province, South Africa(University of the Free State) Van Aardt, Andri Corne; Du Preez, P. J.; Sieben, E. J. J.English: The aim of this study was to assess, classify and describe the natural vegetation along the Vet River. The study was restricted to the vegetation of the islands, banks as well as the floodplains. The Vet River is situated in the Free State Province, South Africa. The study area covers approximately 8 928 hectares including the surface area of the Erfenis Dam, which is situated downstream of the confluence of the Groot Vet and Klein Vet Rivers. There are several towns in the catchment of the Vet River which include: Exelcior, Winburg, Theunissen and Hoopstad. The area around the river also has a provincial nature reserves namely: Willem Pretorius Game Reserve along the Sand River, a tributary of the Vet River, the Erfenis Dam Nature Reserve near Theunissen and the Sandveld Nature Reserve downstream of Hoopstad. The area is mostly situated in the Highveld climatic region with cold and dry conditions due to the high elevation and the inland continental aspects of the area. Furthermore the area is characterised by warm summers with strong summer rainfall patterns and mild winters with drought. The rainfall received is mostly in the form of regular showers and thunderstorms during the months of October to March. The geology of the area is dominated by the Karoo Supergroup which was deposited during the period of 310 to 182 million years ago. Only the Ecca, Beaufort and Stormberg Groups occur in the study area. In the area, two biomes are present. These biomes are the Grassland biome (which occur between sea level to 2 850m above sea level) which mainly represent the high central plateau of South Africa and the Savanna biome (occur at altitudes below 1 500m above sea level) which mostly occur in areas with a strongly seasonal rainfall and a distinct dry season which usually occur in winter. The Vet River cuts through seven vegetation types. Various kinds of wetlands occur along the Vet River. All of them falls within the RAMSAR definition of a wetland namely: “wetlands are areas of marsh, fen (peat-accumulating wetland that receives some drainage from surrounding mineral soil and usually supports marshlike vegetation), peatland (generic term of any wetland that accumulates partially decayed plant matter) or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres”. The presence of wetlands in the study area lead to the search for a proper definition for these unique systems as they also perform certain functions and can be seen as valuable ecological laboratories because of their habitat and species diversity. Riparian areas is seen as the interface between aquatic and terrestrial ecosystems, however these areas can also be defined as frequenting, growing on, or living on the banks of streams or rivers. These areas are usually narrow and linear and can be regarded as corridors for migrating species. During the study 240 sample plots were placed within various homogenous vegetation types along the Vet River. The Braun Blanquet cover-abundance scale was applied in this study. The vegetation analysis led to the classification and identification of 14 plant communities, 21 sub-communities and 11 variants which were discussed phytosociologically: The communities can be divided into those communities that occur in the mountains, those communities that occur in the riverine areas on plains and the communities that occur in the floodplains or pans along the Vet River.Item Open Access Plantsosiologie van die Bloemfontein-Wes-Distrik(University of the Free State, 1992-11) Malan, Pieter Willem; Venter, H. J. T.; Du Preez, P. J.English: The aim of this study was to identify, characterize and interpret, ecologically, by using hahitat properties, the major vegetation units and their variations. The study area covers approximately 350 000 hectares. Most of the area is intensively utilized for farming practice. The western parts of Bloemfontein are, geologically underlied by the Ecca group. The hilly appearance of this area is caused mainly by dolerite intrusions. Bloemfontein is situated in a semiarid region, having dry, cold winters with frost and warm summers accompanied by a low, irregular rainfall. The mean annual rainfall is 564 mm, but it varies greatly. As far as the biotic environmental factors are concerned, man, especially, plays a great part by affecting the composition of the vegetation and the condition of the habitat. A total of 254 sample plots were used to survey the area. A combination of classification techniques was used to interpret the vegetation, ecologically, and to identify and classify plant communities. The study area was stratified according to land types. The number of sample plots was chosen subjectively and pro rata according to the size of each land type within each land type. Five separate plant sociological tables were compiled, and the results of each of these are discussed separately. Because the Bloemfontein area was previously studied by different authors no survey was made in the Ea-land type. Thirty five plant communities were identified and described. These communities are summarized in a synoptic table for the entire study area. In the synoptic table four vegetation units could be identified. These units are: (1) Communities of the other Rhoetalia ciliato-erosae (2) Communities of the lowland areas (3) and (4) Disturbed communities of the lowland areas The most important tree species are Acacia karroo, Buddleja saligna, Celtis africana, Cussonia paniculata, Ehretia rigida, Grewia occidentalis, Heteromorpha trifoliata, Olea europaea subsp. africana, Rhus lancea and Ziziphus mucronata. The dominant shrubs include: Euclea crispa, Euphorbia mauri tanica, Rhigozum obovatum, Rhus burchellii, R. ciliata en R. erosa. The dominant grass species are Aristida congesta, A. diffusa, Chloris virgata, Digitaria eriantha, Eragrostis curvula, E. lehmanniana, E. obtusa, E. superba, Heteropogon contortus, Themeda triandra and Triraphis andropogonoides. Among the dwarf shrubs and herbs Asclepias fruticosa, Berkheya onopordifolia, B. pinnatifida, Chenopodium album, Felicia filifolia, Lactuca dregeana, Chrysocoma ciliata, Cirsium vulgare, Hermannia bryoniifolia, Hertia pallens, Lantana rugosa, Melolobium candicans, Nenax microphylla, Nidorella resedifolia, Protasparagus laricinus, P. striatus, P. suaveolens, Rumex crispus, R. lanceolatus, Salsola kali, Salvia stenophylla, S. verbenaca, Solanum coccineum, S. incanum, Stachys rugosa, Tagetes minuta en Walafrida saxatilis are the most important. The stratification of the study area into land types and the compilation of a separate plant sociological table for each land type resulted in the successful identification of ecologically sound plant communities.Item Open Access Vegetation classification of the University of the Free State campus, Bloemfontein(University of the Free State, 2007-05) Nthejane, Maboee; Du Preez, P. J.; Venter, H. J. T.English: The aims of this study were to survey, classify, describe and ecologically interpret the natural plant communities of the University of the Free State campus in Bloemfontein. A further aim was to apply the urban biotope mapping technique to the campus so that ecological information may be availed to decision makers at the University in an easily accessible format. The phytosociological study was based on Braun-Blanquet procedures. A total of 222 reléves were classified using TURBOVEG, TWINSPAN and MEGATAB. Ordination using the DECORANA ordination algorithm was also applied to the floristic data in order to determine the relationship between the vegetation units and environmental variables. The vegetation was classified into 5 Major Grassland Communities and 2 Major Wetland Communities. All the vegetation units and sub-units were ecologically interpreted and described. Biotope mapping was conducted on the campus using a German technique that has been used in the city of Potchefstroom after being customized to South African conditions. The resultant biotope map showed that most of the space on the campus is taken up by 3 biotope types, namely the built-up area with its intensively managed lawns and gardens and planted trees mainly on the eastern side of the campus, the extensively managed open spaces (natural grassland) mainly in the middle and to the west and the intensively managed sports fields. This study also contributes to the building up of scientific knowledge about the Grassland Biome. Recommendations are made as to how the vegetation on the campus and in other increasingly urbanizing areas of the Grassland Biome may be managed in a manner that is ecologically sound and that meets amenity needs as well.Item Open Access Vegetation ecology of Soetdoring Nature Reserve: pan, grassland and karroid communities(University of the Free State, 2002-09) Janecke, Beanelri Benene; Du Preez, P. J.; Venter, H. J. T.English: The main aim of this study was to identify, classify, describe and ecologically interpret the plant communities and their variations for the pans, grassland and karroid grassland of Soetdoring Nature Reserve and to compare it to other similar units where possible. A further aim of the study was to provide the Department of Environmental Affairs & Tourism of a baseline study of the grassland and pan vegetation and to provide results which could serve as an ecological basis for future management, conservation and research. Soetdoring Nature Reserve is situated in the Free State Province, about 35 kilometres north-west of Bloemfontein and covers approximately 6 000 ha. The Modder River divides the reserve in two and the Krugersdrif Dam is also included in the reserve‟s boundaries. The main aim was achieved by undertaking a phytosociological investigation by means of the Braun-Blanquet method. The total data set consists of 229 relevés and 171 species. After refinement, the Braun-Blanquet procedures yielded 17 plant communities. Phytosociological tables were compiled for each of the pan, grassland and karroid grassland, and a synoptic table for the total data set, in order to determine the communities and their variants. An ordination algorithm (DECORANA) (Hill 1979b) was also used to indicate the floristic relationships among the vegetation units. The pan unit was classified into five communities and eleven subcommunities. Two pans are present in the reserve, on the southern and northern side of the Modder River respectively. The northern pan was classified as a Grass Pan and characterised by Cynodon transvaalensis, Panicum schinzii and Echinochloa holubii. The southern pan was classified as a Diplachne Pan and is dominated by Diplachne fusca and Eragrostis bicolor. Two permanent earth dams and a hot spring are also present inside the southern pan basin. Earth Dam A is dominated by Eleusine coracana and Phyla nodiflora, while Earth Dam B is characterised by Cyperus bellus and Eragrostis biflora. The vegetation of the hot spring consists of a dominant zone of Phragmites australis, surrounded by a dense zone of Juncus rigidus. The grassland unit was divided into grassland and karroid communities, due to the state of degradation thereof. The classification resulted in five grassland communities and seven karroid communities. The grassland communities are characterised by climax grasses, with the dominant species being Themeda triandra and Digitaria eriantha. The karroid communities are dominated by dwarf karroid shrubs, like Salsola glabrescens, Rosenia humilis and Felicia muricata, as well as subclimax and pioneer grasses, like Eragrostis obtusa, Chloris virgata and Aristida adscensionis. This study provides important information on especially the pans in the reserve, since little information is available for the vegetation of pans in the Free State. The chapters on pans serve to bring all the available information together and to apply the information to the reserve‟s pans. This study is further of importance in indicating the degree of disturbance in the grassland unit. The impact of the animals and the importance of these mentioned areas for the game in the reserve, were taken into consideration for each vegetation type.