ETD Collection

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2016 - 20182

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    Assessment of the invasive potential of Foeniculum vulgare (fennel) in the Sarah Baartman District and Nelson Mandela Bay Municipalities in South Africa`s Eastern Cape Province
    (2018) Magagula, Thokozane Innocent Pappa
    Foeniculum vulgare (Fennel) is native and widely distributed in many Mediterranean countries in Europe. Nowadays the species' distribution extends globally due to its cultivation as a food crop and its use as an herb. Fennel has been reported as invasive in Australia, New Zealand and California and reported as a naturalised garden escapee in South Africa. Because of similarities between the climates of the Western Cape Province in South Africa and Mediterranean countries the likelihood of the species becoming invasive in South Africa is high. In this report, the Sarah Baartman District and Nelson Mandela Bay Municipalities in the Eastern Cape Province, South Africa, were used as study areas to assess the invasive potential of Fennel. To this end, information from different sources was used to draw conclusions on the species' invasiveness in South Africa. These included using ArcGIS maps to estimate the current distribution of fennel in the study area and South Africa with the use of survey records, Herbarium data and SAPIA information; CLIMEX modelling to estimate the future potential distribution of the species based on climatic suitability; an assessment of major vegetation types where the species mostly occur; seed germination and reproductive output; and a risk assessment. A comparison of current distributional data with predicted future distribution of the species found that South Africa has a suitable climate for fennel and therefore the likelihood of the species establishing in many regions is high. Anthropogenic activities are anticipated to increase the potential of the species to become invasive. This conclusion is based on the observation that where vegetation has been degraded as a result of human influence, naturalised populations of the species were observed. High seed production capacity and high germination rates of Fennel also increase the likelihood of the species spreading now and in the future. The species also obtained high weed risk assessment score in South Africa, and swift action is required to control the species while populations are still manageable in size and before the species has a significant environmental impacts. Delayed action v will result in the continued spread of this invasive species, making it more difficult to successfully curb the spread thereof in the future
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    Germination and predation of Acacia karroo seeds on acid mine drainage polluted soils
    (2016) Lagerwall, Dawn
    The study aims to assess the impacts of Acid Mine Drainage (AMD) polluted soils on Acacia karroo seed germination and viability, seed dry mass and predation, in comparison with trees from the same provenance growing on non-polluted soils. The study was undertaken within the Vaal River Operations mining rights area. This area is bisected by the Vaal River which separates the polluted area from the non-polluted area. Contamination of soils on the northern section of the Vaal River is a result of mining operations, historical tailings spillage as well as an existing pollution plume which has resulted in AMD polluted soils. The rehabilitation of disturbed land is often hindered due to low seedling establishment. The success of germination is one of the most important first steps for seedling establishment and growth and hence towards establishing a self-sustaining vegetation cover over disturbed areas. Dry seed mass was slightly higher from trees in non-polluted (0.051±0.009g) compared to the polluted areas (0.046±0.009g), however no significant difference was found. Seeds collected from the non-polluted area had highest proportion of seeds in the seed mass class 0.0455-0.0904g, compared to the seeds from the polluted areas which were highest in the smaller seed mass class 0.0155-0.454g. At the tree level, the Coefficient of Variation (CV) for dry seed mass was higher for seeds collected from the polluted area (20.5%) compared to the non-polluted area (17.9%), however, no significant difference was found. However, percentage seed predation was significantly lower in the polluted (35±15.76%) relative to the non-polluted areas (48±14.69%). Percentage seed germination was significantly higher in the non-polluted (92±9.35%) compared to the polluted areas (81±20.42%), with a significantly more rapid germination rate of 4.2±0.19 days compared to 4.7±0.45 days, respectively. In conclusion, despite their lower dry seed mass, seeds collected from AMD polluted soils still had high percentage germination, while exhibiting a lower percentage of seed predation compared to those growing on unpolluted soils. Due to A. karroo’s apparent tolerance to the poor conditions on the AMD polluted soils and its regeneration capabilities, it is likely to be a good species for rehabilitation of AMD polluted sites. Further studies should aim to determine seedling performance from those seeds collected from polluted areas in terms of seedling establishment, rates of growth and survival over time when established in AMD polluted soils as well as non-polluted soils, to determine their likely success.