A research report submitted to the Faculty of Science, University of the Witwatersrand,
in partial fulfilment of the requirements for the Degree of Master of Science by Coursework and Research Report. Johannesburg, March 2016. / A vegetation survey was carried out in July 2014 on the substrates of 5 tailings dams by
selecting 10 sampling sites which were previously used as sampling plots during the 1996/97
survey of Weiersbye et al. (2006). At each sampling site a 100m transect horizontally across the
substrate and covering all levels of the tailings dam from the flat top to the toe paddock was
established. Each transect was surveyed for the frequency of the species occurring and these were
categorized based on their mode of colonization (natural, intentionally introduced and persisting)
while tailings were collected by digging approximately 20cm into the ground for soil sample
collection per substrate. The recorded species were then divided using Raunkier’s classification
categories into growth forms and a comparison was done between the two surveys (2014 versus
1996/7) to identify the species that were lost, those that were still persisting and the new ones that
had colonized over time. A total of 51 species (over 15ha) in 36 genera within 14 families were
recorded on the tailings dams, compared to 168 species (over 765ha), 98 genera and 59 families
found in the previous study. Families with the most species in 2014 were similar to those of the
1996/97 survey, following the dominance order of Poaceae >Asteraceae >Fabaceae
>Anacardiaceae, with the percentage frequency of grasses (Poaceae) noted to have almost
doubled over this period. Compared to 6 species common across the substrates in the previous
study, the later survey recorded 12 common species (6 of the species occurring on all substrates)
but overall both studies found vegetation cover to be high (above 65%) on flat tops and berms
with species richness being high on the toe paddock>slopes>tops and berms and substrates
susceptible to low nutritional (N,P,K,C) value. Indigenous plant species (54.9%) were dominating
the tailing dams and were mostly perennials (82.3%) that were naturally colonizing and persisting
(72.5%) on the tailings dams (similar to the 1996/97 survey), while alien (45.1%) plant species
comprised annuals/biennials (17.7%) that were intentionally introduced (27.5%) prior to the
1996/97 survey by contractors. The ceased ameliorative initiatives since the first survey are
believed to have significantly contributed to a decrease in herbaceous species richness, which
formed the majority of the introduced species in the former survey (58.8% compared to 29.4%) as
they depended on the supplementary additions of fertilizers and lime. Approximately 117 species,
62 genera and 45 families (including Chenopodiaceae, which was dominant) were lost over the
17 years period, the majority of these were introduced prior to the 1996/97 vegetation survey,
while only Ficus sp. was the only new species colonizing apart from the increase noted in alien
species (some invasive in nature). The decrease in species richness has encouraged woody and
semi-woody (35.3%) and grasses (35.3%) to dominate the slimes reaffirming their potential as
temporal and long term rehabilitation species that have developed physiological tolerance to
acidic conditions, salinity and heavy metal pollution. In conclusion, this study has identified the
species that can be used for phytoremediation to provide long terms solutions for dust, air and
water pollution and soil erosion suppression for rehabilitation of these contaminated lands
(Appendix 8). The survey also helps to identify species that are able to naturally colonize and
persist on the tailings dams without supplements, making them ideal economic species to use for
rehabilitation. Results also highlight the negative impacts of the lack of ameliorative
supplementations, which in turn affects the floristic composition and structure on these tailings
dams over time.
Keywords: Aerial cover, Macronutrients, Tailings dams, Species richness, Tailings Storage Facilities
(TSFs) and Vegetation survey / LG2017
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/21737 |
| Date | January 2016 |
| Creators | Maguranyanga, Mike |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (52 pages), application/pdf |
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