**4. Affinities with other regions**

Platberg shares many climatic, edaphic and biotic similarities with the Drakensburg Alpine Centre (DAC). Biogeographically and chorologically it falls within the DAC and shares many of the same plant species and endemic taxa (Brand et al., 2010). Biogeographical and botanically the DAC is seen as a transition zone, a migratory pathway and repository for taxa of diverse regions and biomes (Killick 1963, 1978a, 1978b, Hillard & Burtt 1987, Carbutt & Edwards 2004, Mucina & Rutherford 2006). The DAC has some 2800 species of vascular plants of which 929 are endemic or near-endemic angiosperms in an area of 40 000 km² (Carbutt & Edwards 2004, 2006). The Global Information System (GIS) approach of Mutke et al. (2001) correlates well with these figures, showing a plant species richness > 3000 species per 10 000 km².

The two largest plant families on Platberg are Asteraceae (40 genera, 126 species, comprising 18.8% of the flora), and Poaceae (39 genera, 73 species, 10.9% of the flora). This pattern of high diversity of Asteraceae is common to the DAC where it is represented by 65 genera and 430 species and 17% of the total flora (Carbutt & Edwards 2004). The pattern is the same for Poaceae where, in the DAC it is represented by 86 genera and 267 species and contributes 11% to the total species flora (Carbutt & Edwards 2004). The Grassland Biome with the DAC, Platberg in its centre, has provided idea habitat for the rapid spread of Asteraceae, as well as the development and radiation of grasses (Carbutt & Edwards 2004).

Floristic composition for Platberg and the DAC shows Asteraceae as the largest family (Brand et al., 2010). This trend is the same for the Cape flora, with significant correlation within the top 12–20 families (Goldblatt & Manning 2000). The second most specious family on Platberg is Poaceae (39 genera, 73 species, 10.9% of the flora) followed by Cyperaceae (18 genera, 39 species, 5.8% of total flora), which reflects a similar floral composition to the DAC (Carbutt & Edwards 2004, 2006; Mucina & Rutherford 2006). This trend with the same ranking for the top 3-10 families plus rations of floristic compositions is also found with the more grassy regions to the arid western interior and higher altitude, wetter northern areas of South Africa (Kooij et al., 1990; Du Preez & Bredenkamp 1991; Fuls 1993; Eckhardt et al. 1993, 1995; Malan 1998).

The ranking of Poaceae and Cyperaceae as the second and third richest families on Platberg and the DAC, which is in contrast to the Cape flora, where Poaceae and Cyperaceae are poorly represented with Restionaceae filling the environmental and floristic position of the Poaceae (Goldblatt & Manning 2000; Brand et al., 2010). For the Cape fynbos Fabaceae is the second largest family followed by Iridaceae, Aizoaceae, Ericaceae and Scrophulariaceae

(DAC). Only 22 alien plants occur of which most are annual Dicotyledons (Brand et al., 2010), which is a good indicator of limited human influence on the vegetation of the Platberg plateau.

Platberg shares many climatic, edaphic and biotic similarities with the Drakensburg Alpine Centre (DAC). Biogeographically and chorologically it falls within the DAC and shares many of the same plant species and endemic taxa (Brand et al., 2010). Biogeographical and botanically the DAC is seen as a transition zone, a migratory pathway and repository for taxa of diverse regions and biomes (Killick 1963, 1978a, 1978b, Hillard & Burtt 1987, Carbutt & Edwards 2004, Mucina & Rutherford 2006). The DAC has some 2800 species of vascular plants of which 929 are endemic or near-endemic angiosperms in an area of 40 000 km² (Carbutt & Edwards 2004, 2006). The Global Information System (GIS) approach of Mutke et al. (2001) correlates well with these figures, showing a plant species richness > 3000 species

The two largest plant families on Platberg are Asteraceae (40 genera, 126 species, comprising 18.8% of the flora), and Poaceae (39 genera, 73 species, 10.9% of the flora). This pattern of high diversity of Asteraceae is common to the DAC where it is represented by 65 genera and 430 species and 17% of the total flora (Carbutt & Edwards 2004). The pattern is the same for Poaceae where, in the DAC it is represented by 86 genera and 267 species and contributes 11% to the total species flora (Carbutt & Edwards 2004). The Grassland Biome with the DAC, Platberg in its centre, has provided idea habitat for the rapid spread of Asteraceae, as

Floristic composition for Platberg and the DAC shows Asteraceae as the largest family (Brand et al., 2010). This trend is the same for the Cape flora, with significant correlation within the top 12–20 families (Goldblatt & Manning 2000). The second most specious family on Platberg is Poaceae (39 genera, 73 species, 10.9% of the flora) followed by Cyperaceae (18 genera, 39 species, 5.8% of total flora), which reflects a similar floral composition to the DAC (Carbutt & Edwards 2004, 2006; Mucina & Rutherford 2006). This trend with the same ranking for the top 3-10 families plus rations of floristic compositions is also found with the more grassy regions to the arid western interior and higher altitude, wetter northern areas of South Africa (Kooij et al., 1990; Du Preez & Bredenkamp 1991; Fuls 1993; Eckhardt et al. 1993, 1995; Malan 1998). The ranking of Poaceae and Cyperaceae as the second and third richest families on Platberg and the DAC, which is in contrast to the Cape flora, where Poaceae and Cyperaceae are poorly represented with Restionaceae filling the environmental and floristic position of the Poaceae (Goldblatt & Manning 2000; Brand et al., 2010). For the Cape fynbos Fabaceae is the second largest family followed by Iridaceae, Aizoaceae, Ericaceae and Scrophulariaceae

well as the development and radiation of grasses (Carbutt & Edwards 2004).

Pteridophytes 8 10 16 Gymnosperms 2 2 2 Angiosperms 86 293 652 (Monocotyledons) (23) (104) (214) (Dicotyledons) (63) (189) (438) **Totals 96 305 670** 

Table 1. Floristic composition for Platberg (Brand et al., 2010)

**4. Affinities with other regions** 

per 10 000 km².

**Families Genera Species** 

(Goldblatt & Manning 2000). With the exception of Ericaceae, these families for significant floral structure and species composition represented in the top 7 families for Platberg and the DAC (Brand et al., 2010).

The fynbos vegetation elements found on Platberg and the DAC show close affinities with similar fynbos of the Cape Floral Region (CFR). These fynbos elements are characterised by *Passerina*, *Cliffortia, Metalasia* and *Muraltia* species which all exhibit narrow, but extensive ranges, located on depaupered soils of the Clarens Sandstone Formation. There are two distinct fynbos vegetation types found on Platberg and the DAC. They are described as the Gd 9 Drakensberg–Amathole Afromontane Fynbos, and the Gm 24 Northern Escarpment Afromontane Fynbos (Mucina & Rutherford 2006).

## **4.1 Vegetation composition and structure: Grasses and forbs using C3, C4 and CAM pathways**

To understand how rising CO2 levels with increased temperatures may affect plant species composition and vegetation structure, an analysis of plant communities using CAM, C4 and C3 metabolic pathways was done. At high temperatures C4 outcompete C3 plants (Retallack 2001), it would be predicted that high altitude vegetation using the C3 pathway would show a reduction of range, an upward shift in distribution and a loss of species. Most of the grasses comprising the Grassland Biome occur at altitudes below 1 200 m and consequently use the C4 pathway, while most montane grasses, trees and shrubs use the C3 pathway. Asteraceae, also use the C3 pathway while Wetland plants, ferns, Gymnosperms and succulents use Crassulacean Acid Metabolism (CAM). The analysis of the plant families on Platberg using C3, C4 and Crassulacean Acid Metabolism (CAM) are from Brand et al., (2010).

The phytosociological analysis for Platberg found 39 distinct plant communities (Brand et al., 2008, 2009, 2010) all of which contain a combination of Asteraceae Poaceae, and Cyperaceae. Only 7 plant communities are dominated by woody/shrubs and exclusively use the C3 pathway. The remaining 32 that plant communities are structure by species using C4 pathways, CAM or high altitude grasses which use the C3 pathway. Excluding the woody/shrub communities 82% of the formally classified plant communities use C3, C4 or CAM pathways (Table 2).


Table 2. Platberg vegetation using C3, C4 or CAM pathways

Biogeography of Platberg, Eastern Free State, South Africa:

main Drakensberg at Qwa-Qwa to the south (Figure 5).

(von Maltitz 2003; Mucina & Rutherford 2006).

Links with Afromontane Regions and South African Biomes 121

Van Reenen's Pass 60km east of Platberg, Royal Natal National Park to the west and the

The highest altitude Afrotemperate *Podocarpus* forest in South Africa grows on Nelsons Kop at 2 230 m (Von Maltitz 2003), an inselberg about 20 km northeast of Platberg, and as with the forest patch on Platberg, it is located on the cool south-eastern side, below the basalt on the Clarens Formation sandstones. Other Northern Afrotemperate Forest affinities are found to the south, in the Fynbos Biome, and the Savanna Biome mountains to the north

Fig. 5. *Podocarpus* forest patches below the Clarens Formation sandstone confined to fire

Fynbos on Platberg occurs in 13 different communities, which can be grouped into two communities (Brand 2008). The sclerophyllous vegetation is characterised by *Passerina montana*, a fynbos taxa endemic to the Cape (Figure 6). These fynbos communities have a species richness varying between 14 – 54 species per 30 m², with an average of 28.34 species per 30 m². This is lower compared with the grassland vegetation, which has 11 – 54 per 30 m² with an average of 32 per 30 m², which gives a moderate species diversity index. A minimum 16 fynbos genera comprising 22 species occur on Platberg. The fynbos is located in two distinct habitats: the lower altitude zone at 2000 m growing on the mineral poor soils of the Cave Sandstone of the Clarens Formation, and the higher altitude zone at 2200 m on the rocky, basaltic, mineral rich rim of the plateau just below the exposed summit grassland

Fynbos and the Gm 24 Northern Escarpment Afromontane Fynbos (Mucina & Rutherford 2006). This afromontane fynbos community is found on most of inselbergs including the Floristically, and structurally, the *Passerina montana* fynbos-like shrubland elements found on Platberg conform with the Gd 6 Drakensberg-Amathole Afromontane Korannaberg 200km west, and a similar altitude of 2000-2200 m in the Drakensberg. For Mucina & Rutherford (2006) it is structurally and floristically different from the other Afromontane fynbos species rich community found at higher altitudes and embedded in the Gd 8 Lesotho

protected gullies of the Drakensberg and Great Escarpment.

**5.2 Fynbos Biome affinities** 

(Brand et al., 2008).

Highveld Basalt Grassland.

On a species level, succulent families using CAM pathways total 278 species and 122 genera **(Table 1).** This accounts for 44.6% of the total genera and 42% of the total species found on Platberg.
