**3. Results**

116 Biodiversity Loss in a Changing Planet

A map showing continental wide African sites of high biodiversity using both the taxonbased approach and the geographical or inventory-based approach are presented by Mutke et al., (2001). This Global Information System (GIS) approach to map African phytodiversity shows good correlation with climatic, edaphic and biotic parameters for African phytodiversity for the Drakensburg/Natal Area – analogous to White's *Afromontane* archipelago-like regional centre of endemism. This study has improved on White's broad scale map, but being a desktop study still does not provide detailed information of species

Regional mapping of the biodiversity by Van Wyk and Smith (2001) and Mucina & Rutherford (2006) provides a more detailed pattern of plant diversity, which correlates well with the geological map of the African land surface (White 1983; Hillard & Burtt 1987). The South African Drakensberg is shown within this archipelago-like regional endemic centre, which Hillard & Burtt (1987) called the *Eastern Mountain Region* (EMR), first used by Phillips

The use of the EMR has not been followed as it shows a broader, topographically less welldifferentiated area and is a loose correlation with the more precise geographical/ topographical designation of the Drakensberg Alpine Centre (DAC) (Van Wyk & Smith 2001). However, what Hillard & Burtt (1987) where alluding to, in using the term 'EMR', was to differentiate the Drakensberg and surrounding high altitude areas from the rest of the continental wide *Afromontane* region due to its unique and rich floristic composition. Biogeographically, the DAC and Platberg also show relatively strong floristic affinities with the Cape Floristic Region (Linder 2003; Carbutt & Edwards 2004, 2006) or the Fynbos Biome as defined by Mucina & Rutherford (2006). Other biogeographical links are shared with Nama-Karoo Biome found in the drier interior of the sub-continent and further north the sub tropical African and Eurasian flora (Mutke et al., 2001). It is within this broader Afromontane biogeographical context, including being one of an 'island-like' archipelago of

The field-derived data was analysed using phytosociological principles. The statistical analysis of vegetation and environmental data, which underpins phytosociology, provides a measure for biodiversity that is incorporated in the concepts of species richness and evenness or relative abundance. A total of 393 relevés where analysed for the entire Platberg. The scope of the study was to sample vegetation plots above the 1 800 m contour in order to work within the limits set by Killick (1978a) who regarded the region in the Drakensberg above the 1 800 m as a distinct floristic region - the Afroalpine Region. The topography of the plain in which Platberg is situated, is relatively flat, rising abruptly at the 1 900 m contour, this being the start of the footslopes, which was used as the lower limit set

Additionally, the PRECIS (National Herbarium Pretoria [**PRE**] **C**omputer **I**nformation **S**ystem) data from the South African National Biodiversity Institute (SANBI), Pretoria, was used to compare species with the Platberg data. The PRECIS list is compiled from field collections and plotted on a grid square frame with each grid covering 30 x 30 km². Even though the PRECIS data covers the same grid square as Platberg, it is mostly flatland under 1 800 m lower than the footslopes of Platberg which start at 1 900 m. The comparison was done to reveal correlations and connections, which exist with Platberg and the vegetation of

richness on the local community scale.

in 1917 (Carbutt & Edwards 2004).

**2. Methods** 

for sampling.

inselbergs that Platberg's biological diversity is considered.

The vegetation on Platberg is dominated by grasses and shows an intergrade of floristic associations and habitat features in common with several other major vegetation types of the Grassland, Fynbos, Afrotemperate Forest and Nana-Karoo Biomes. Fynbos as well as succulents, particularly Mesembryanthemaceae from the Nama-Karoo Biome grow on Platberg. These floristic elements also extend to the DAC. Woody shrubs and forest remnants grow in the specalised ecological niches in sheltered gullies, boulder beds and rocky terrain. Numerous wetlands occur, forming distinct hygrophilous communities. Geophytes and forbs add significantly to the biodiversity of all vegetation types and grow in all habitats. Only two Gymnosperms occur, the indigenous, forest emergent tree *Podocarpus latifolius*, and the exotic *Pinus patula*, established in timber plantations at lower altitudes, which have now invaded and are replacing the indigenous vegetation on the cool southern slopes. Pterdophyte diversity is relatively low, comprising a total of 16 species, 10 genera and 8 families. Ferns are widespread and occur throughout all habitats, on all aspects – hot northern, cool southern and at all altitudes. Three of the ferns, *Dryopteris dracomontana, Mohria rigida* and *Polystichum dracomontanum* are endemic to the DAC. All but one species (*Pellaea calomelanos*) occur at altitude throughout the Afromontane region. The exotic bracken, *Pteridium aquilinum* occurs on the lower footslopes with *Searsia pyroides* subsp *gracilis*. The prostrate fern, *Selaginella caffrorum* is a mat forming species, which forms unique communities that contribute to inselberg vegetation structure. *Selaginella* communities are found on open, sheet rock on Platberg, Korannaberg, Thaba Nchu and other inselbergs as well in the DAC. *Afrotrilepis pilosa* mats occurring on granite inselbergs of west Africa are physiognomic equivalents.

Of the 974 species, in the PRECIS database, collected in the 2828AC Harrismith grid, about 670 (68.8%) species occur on Platberg above 1 900m. The rest (31.2%) occur on the surrounding lowlands. The 670 species found on Platberg were correlated with DAC species lists of Van Zinderen Bakker (1973), Killick (1963, 1978a, 1979b), Hill (1996), Low & Rebelo (1996), Carbutt & Edwards (2004, 2006), Hoare & Bredenkamp (2001), (Moffett 2001), Smith & Van Wyk (2001) and Mucina & Rutherford (2006). A strong genus level correlation of over 80% was found between Platberg and the DAC, which includes exotic angiosperm taxa such as *Pinus, Acacia,* Bidens, Tagetes, etc. (Carbutt & Edwards 2004).

Of the 670 species recorded on Platberg, several species are new records for the Free State and represent range extensions, or have only been collected once before (Brand et al., 2010). One of these species *Struthiola angustiloba*, a rare KwaZulu-Natal species was collected on Platberg. Two Asteraceae species also collected on Platberg, *Helichrysum harveyanum* and *H. truncatum* are Northwest/Gauteng and Mpumalanga endemics, giving new range extensions of 400-500 km south to Platberg. These new range extensions are not totally unexpected, given that mountain chains act as routes of migration (Körner 2003) and with similar altitude and ecological conditions, distance is not a critical factor (400-500 km), but similarity in live zones determines speciation, rarity and endemism (Körner 2003).

Of the 670 vascular plants recorded on Platberg, there are 305 genera in 96 families (Table 1). Of these 27 are endemic or near-endemic species also found in the Drakensberg Alpine Centre

Biogeography of Platberg, Eastern Free State, South Africa:

Afromontane Fynbos (Mucina & Rutherford 2006).

the DAC (Brand et al., 2010).

CAM pathways (Table 2).

**pathways** 

Links with Afromontane Regions and South African Biomes 119

(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 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

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

C4 and Crassulacean Acid Metabolism (CAM) are from Brand et al., (2010).

Table 2. Platberg vegetation using C3, C4 or 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,

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

**Plant Family Pathway Gen. No. Gen % Spp. No Species (%)**  Asteraceae most C4/ C3 40 13.1 126 18.8 Poaceae mixed C4 C3 39 12.8 73 10.9 Cyperaceae C4 18 5.9 39 5.8 Crassulaceae CAM 3 1.0 13 1.9 Caryophyllaceae C4 9 1.2 4 1.3 Euphorbiaceae C4 3 1.0 8 1.2 Brassicaceae C4 4 1.3 4 0.6 Amaranthaceae C4 2 0,7 5 0.7 Mesembryanthe-maceae CAM 2 0.7 4 0.6 Chenopodiaceae C4 1 0.3 1 0.1 Restionaceae C4 1 0.3 1 0.1 **Totals 122 44.6% 278 42%** 


(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.

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