**2. Study area and methods**

it is as a result of pollution, development, droughts etc. is first seen in the vegetation and its

**Figure 1.** Locality of the Free State Province and the distribution of the Bloemfontein Karroid shrubland vegetation

The term biodiversity refers to the diversity and number of plant and animal species on earth. Biodiversity conservation not only refers to the protection of all species, but also habitats, ecosystems and biomes (Brower *et al.* 1990; Van As *et al.* 2012*).* The diversity of species within an ecosystem is partly a reflection of the diversity of the physical environment. The more diverse the environment the higher the species richness is expected to be due to different microhabitats available for different plant and animal species (Van As *et al.* 2012). A diverse ecosystem contains a variety of genetic material that will ensure long-term stability and survival and also are less likely to be invaded by alien or pioneer species. Biodiversity conservation is very important for the survival of humans on earth. Each and every species on earth is important and crucial in an ecosystem. The loss of one species could lead to the loss of various others that in turn will have a chain reaction of events that could cause the destruc‐

The impact of humans on the environment is widespread and a cause for concern (Botha 2003). As the human population increased over time, people started to exert a bigger influence on nature (Grime 1997). The demand for land for housing, agriculture, mining and industries are increasing and so is demand for more food and water. The depletion of our natural resources to sustain our life styles causes large scale destruction of the environment. According to Van As *et al.* (2012) and Keddy (2007) the average ecological footprint of humans has reached

species diversity and composition.

330 Biodiversity - The Dynamic Balance of the Planet

type (Gh8) in the Province.

tion of one or many ecosystems.

The Bloemfontein Karroid shrubland vegetation type (Gh8) (Mucina & Rutherford 2006) occurs as an archipelago of isolated patches on shallow dolerite outcrops within the Highveld grassland region of the Free State Province of South Africa (Figure 1). The vegetation is characterised by small-leaved dwarf karroid and succulent shrubs underlain by dolerite sheets of igneous origin (Figure 2). The soil is very shallow and gravelly with exposed rock outcrops prominent. In-between the rock crevices slightly deeper and less gravelly soil occur. A large proportion of the soil present on the rock sheets and those formed from the weathering of the rocks is washed into the adjacent lower-lying areas and depressions (Dingaan & Du Preez 2002).

The province is located within the summer rainfall area of South Africa and experiences warm to hot summers and cool to cold winters. Maximum temperatures are experienced in December and January (30.2°C) while June and July are the coldest months when the average daily temperature could drop to -1.6°C (Dingaan & Du Preez 2002). The eastern areas are prone to snowfalls especially on the higher-lying mountains while the western areas are more arid. The province receives approximately 580 mm of rain per annum with the highest rainfall between November and February.

In order to obtain a representative sample of the Bloemfontein Karroid Shrubland, a total number of 68 relevés (16 m2 ) were surveyed within randomly stratified units of this vegetation type in various parts of the province. The data obtained is representative of five different stands of this vegetation type stretching from Bloemfontein in the south-west to the Willem Pretorius Nature Reserve in the north-east. The plot data were grouped into the five groups namely the Bloemfontein stand, the Winburg stand, the Willem Pretorius Nature Reserve stand, the Skoongesig stand and the Kareefontein stand. Habitat as well as floristic data was captured using TURBOVEG (Hennekens 1996; Hennekens & Schaminee 2001) and exported to JUICE (Tichý 2002) from where a raw table (Table 1-Annexure 1) was created for basic floristic interpretation. No formal phytosociological classification was done since the purpose of this study was not to obtain a formal classification, but to compare the different groups in terms of species richness and diversity.

Many people regard species richness and diversity as similar to species diversity. Species richness however refers to the number of species within an area or community (Kent & Coker 1992; Magurran 1988; Magurran 2005; Spellerberg & Fedor 2003). For this study species richness was calculated by determining the total number of species in each stand surveyed.

Species diversity refers to the diversity that occurs within a plant community or area and incorporates both species richness and the evenness of species' abundances (McGinley 2013). Species diversity is one component of the concept of biodiversity and is influenced by the relative abundances of different plant species present within the community. Various indices exist that measure both evenness and species richness into a single measure of species diversity (Stirling & Wilsey 2001). For the purpose of this study the Simpsons Index (Simpson 1949) as well as the Shannon-Wiener Species Diversity Index (Smith & Wilson 1996) was used to determine species diversity for each stand of the Bloemfontein Karroid shrubland surveyed in this study as expressed in the following formulas:

Simpson Index:

$$D = \sum \left( \frac{n \prod\_{i} n i \cdot 1}{N \prod\_{i} n \cdot 1} \right) \tag{1}$$

**3. Results and discussion**

**3.1. Habitat and growth forms**

grassland.

Rutherford 2006)

rocky sheets are indicated on Figure 3.

In 1937, Potts and Tidmarch published an article recognizing a vegetation type near Bloem‐ fontein which has "marked affinities with the Karoo". In 1991, Du Preez and Bredenkamp (1991) named this vegetation unit the *Oropetium capense* community on rock sheets and classified it as a separate vegetation class. Dingaan and du Preez (2002) surveyed this vegeta‐ tion unit near Bloemfontein and identified three different plant communities, namely the *Eragrostis trichophora–Aristida congesta, Heliophylla carnosa–Senecio radicans* and the *Stomatium braunsii–Avonia ustulata* Communities. In Mucina and Rutherford (2006) this vegetation unit, although small in size, is recognized as a separate vegetation type and has been described as the Bloemfontein Karroid shrubland (Gh8). Due to the presence of the scattered dolerite sheets this vegetation type has an archipelago appearance that occurs mainly in the Dry Highveld

Threats of Mining and Urbanisation on a Vulnerable Ecosystem in the Free State, South Africa

http://dx.doi.org/10.5772/57589

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Dolerite is of igneous origin and forms extensive sheets which vary in thickness. During the cooling process various horizontal cracks develop (Duncan and Marsh 2006; Holmes 2012). These cracks create areas where water infiltrates the rock. This allows chemical weathering to take place which in turn allows more water infiltration. Eventually the cracks develop into crevices into which soil and organic matter accumulates. Areas with deeper soil (50mm – 250mm) accommodate deep rooted species such as shrubs, perennial grasses and geophytes. Depressions occur on the exposed dolerite sheets where soil accumulates, These areas, although very shallow (10mm – 50mm), house a few species especially succulents and annuals. The two main environmental factors that differentiate the different plant communities on these

These dolerite sheets create an unusually arid habitat in a relatively high rainfall area due to the high loss of potentially available water. The loss of rainwater is caused by the poor water retention abilities of the coarse textured soil, poor infiltration, high evaporation tempos and high runoff. This unique habitat creates physiological drought conditions (Snyman 1984). The presence of these archipelagos of dolerite sheets with their shallow soils in a "sea" of deep soil and grass covered plains create a mosaic of scattered and isolated patches of arid habitats

The physiological drought environment that is being created by the dolerite sheets and the shallow soil, is unsuitable most of the Grassland biome species but for a number of Namakaroo biome species, which can tolerate the high temperatures and arid conditions present on these dolerite sheets, it creates a suitable habitat. This habitat can therefore be regarded as unique and in a certain sence can be regarded as an azonal vegetation type, Due to the lack of water, it is deviating strongly from the typical surrounding zonal vegetation (Mucina &

The percentages of the number of plant species present per growth form recorded on these

(Figure 2) which are relatively hostile environments for typical grassland species.

dolerite outcrops are soil depth and soil moisture availability.

Shannon-Wiener Index:

$$\stackrel{\cdot}{H}\stackrel{\cdot}{=}\ \cdot\sum\_{i=1}^{S} pi \text{(ln } pi\text{)}\tag{2}$$

Species richness (S), Simpson index if diversity (-ln (D)) and the the Shannon-Wiener index of diversity (H') were calculated for each stand:

S=Richness (Number of species per community)

pi=is the proportion of individuals of a species (relative proportion)

D=Simpson's index of diversity. It represents the likelihood that two randomly chosen individuals will be different species.

A the Chi-Square Test (Welman *et al.* 2007) was performed on the data to determine whether significant associations exist between the different stands.
