ISSN 0075-6458 59 Koedoe 49/2 (2006) Introduction The Egoli Granite Grassland is a type of grassland and a mapping unit (Gm10) clas- sified under the Mesic Highveld Grassland Bioregion according to the new Vegetation Map of South Africa, Lesotho and Swazi- land (Mucina et al. 2005). This grassland was mapped as Bankenveld (veld type 61) by Acocks (1988), and Rocky Highveld Grassland (Vegetation Type 34) by Breden- kamp & Van Rooyen (1996). Acocks (1988) describes the Bankenveld as a False Grass- veld Type. The climax vegetation of this veld type should be, according to Acocks, an open savanna, that is a bushveld vegetation, but it has been changed to, and maintained as grassveld by regular veld fires. How- ever, Bredenkamp & Brown (2003) consider Bankenveld vegetation as a mosaic of grass- land and woodland communities controlled by (micro-)climatic conditions that exist in the topographically heterogeneous landscape in the transition zone between the Grassland and Savanna biomes. From a conservation planning or urban devel- opment viewpoint, the range of structural and floristic variation is considered too large to define Bankenveld as a single unit, even on the reconnaissance level of vegetation investigation. Bredenkamp & Brown (2003) recognised 16 major vegetation types within Bankenveld. The Egoli Granite Grassland is considered as mainly belonging to the Hyparrhenia hirta Anthropogenic Grassland (Bredenkamp & Brown 2003). Egoli Granite Grassland is restricted to the Gauteng Province of South Africa and is located north of the Roodepoort / Krugers- dorp ridge complex and stretches over a distance of approximately 35 km to Centu- rion in the north. This grassland stretches over a distance of approximately 50 km in a westerly direction from the R21 highway in the east. The 28º longitude and 26º latitudi- Conservation value of the Egoli Granite Grassland, an endemic grass- land in Gauteng, South Africa G.J. Bredenkamp, L.r. Brown and m.F. pFaB Bredenkamp, G.J., L.R. Brown and M.F. Pfab. 2006. Conservation value of the Egoli Granite Grassland, an endemic grassland in Gauteng, South Africa. Koedoe 49(2): 59–66. Pretoria. ISSN 0075-6458. Gauteng is the most densely populated province in South Africa. Its remaining natural areas are constantly under threat from urban development and the associated impacts. Presently, the natural areas of Gauteng support a large diversity of ecosystems. One such ecosystem is the Egoli Granite Grassland, endemic to the province, poorly conserved and therefore highly threatened. This paper describes the original Egoli Granite Grassland and the anthropogenic Hyparrhenia hirta dominated grassland that has replaced it in many of the remnant areas. Human impacts on this sensitive ecosystem have resulted in an altered species composition, loss of many species, and a change from a species-rich grassland with high conservation value to a species-poor grassland with low conser- vation value. The conservation of the last remaining relicts of original Egoli Granite Grassland is essential. Keywords: Egoli Granite Grassland; conservation value; Hyparrhenia hirta, Gauteng. G.J. Bredenkamp, African Vegetation and Plant Diversity Research Centre, University of Pretoria; L.R. Brown, Applied Behavioural Ecology and Ecosystem Research Unit, University of South Africa; M.F. Pfab, Bioregional Planning, Gauteng Department of Agriculture, Conservation and Environment, Johannesburg, 2001 South Africa. bredenkamp.indd 59 2006/10/15 10:51:01 PM Koedoe 49/2 (2006) 60 ISSN 0075-6458 nal lines cross in the centre of this grassland (Fig. 1). Due to high demand for developable land in Gauteng, and especially the Johannesburg / Pretoria corridor, the Egoli Granite Grassland is under extreme pressure. Large areas are already developed for residential, industrial and commercial purposes. This has led to the destruction of vast tracts of this grassland. At least 61 % of Egoli Granite Grassland has been permanently transformed: 27 % by urban development (Fig. 2); 17 % by smallholdings; 12 % by agriculture (cultivated lands); and 5 % by other impacts such as exotic plan- tations, mining and planted pastures. An estimated additional 17 % of Egoli Granite Grassland is degraded due to overgrazing and the influence of edge effects associated with a highly fragmented landscape (Fahrig 2003). Other effects, such as trampling, increased pollutants and the infestation of weeds and alien species also contribute to degradation of this grassland. It is therefore highly likely that the national target for conservation of this grassland type, i.e., 25 % of the total extent, will never be realised. Egoli Granite Grassland is extremely poorly conserved, with only 0.02 % (26 ha) of the vegetation type currently protected, includ- ing 3 ha in Glen Austin Bird Sanctuary, 3 ha in Melville Koppies Nature Reserve, 9 ha in Ruimsig Nature Reserve, and 11 ha in the Walter Sisulu Botanical Gardens (Fig. 2). The current protection status of Egoli Granite Grassland is therefore completely inadequate, with only 0.1 % of the national target actually achieved. In order to meet South Africa’s international obligations, it is imperative that the Gauteng provincial government put in place measures to improve the conservation status of Egoli Granite Grassland. Any viable remnant patch of original Egoli Granite Grassland must therefore be pro- tected from transforming land uses. In order to assess whether a valuable remnant patch will be affected by a proposed develop- ment, environmental consultants involved in vegetation impact assessments are required by the Gauteng Department of Agriculture, Conservation and Environment (GDACE) to assess the presence and condition of Egoli Granite Grassland on any site proposed for development. As this grassland was only recently defined with the development of the new Vegetation Map of South Africa, Lesotho and Swaziland (Mucina et al. 2005), very little information on its floristic composition, condition, the 60 0 60 120 Km JHB PTA Fig. 1. Locality map of the Egoli Granite Grassland. Grey areas indicate urbanisation 10 0 10 20 Kilometers N Fig. 2. Dark gray represents remnant areas of poten- tially original Egoli Granite Grassland; perennial rivers shown. bredenkamp.indd 60 2006/10/15 10:51:02 PM ISSN 0075-6458 61 Koedoe 49/2 (2006) extent of the grassland, and the manage- ment thereof exists, causing some confusion among nature conservationists, environmen- tal consultants and local authorities. The aim of this paper is therefore to provide an eco- logical overview of this grassland. Physical Environment This area is generally characterised by rocky undulating plains representing crests, slopes and valley bottoms with shallow, nutrient- poor soils. Shallow drainage lines and vlei- like wetland areas occur in the valley bot- toms. Rockiness of the soil surface is a fur- ther common characteristic shared by most Bankenveld areas. Mean monthly temperature in the study area is 16.8 ºC with a mean maximum of 22.6 ºC and a mean minimum of 10.8 ºC. The mean winter temperature is 13.8 ºC and mean sum- mer temperature, 25.6 ºC (Weather Bureau 2000; Grobler et al. 2002). Mean annual rain- fall in Gauteng is 670 mm (Gauteng 1997). Old granitic and gneissic rocks at least 2 400 million years old (Kerfoot 1987) are exposed in the Egoli Granite Grassland area. The Half- way House Granites (Fig. 3) of the Johannes- burg Dome are intensively weathered with deep drainage lines resulting in a gently rolling topography, with shallow, coarse, nutrient-poor, well-drained soils. The granite areas are mostly covered by grassland vege- tation though patches of woodland vegetation are found at sheltered sites on hillslopes and rocky outcrops within this veld type (Grobler 2000; Grobler et al. 2002, 2006). The Bb land type predominates over the entire region (Land Type Survey Staff 1984, 1985, 1987) (Fig. 3). The residual granitic soils are very shallow and poorly drained. The A horizon is often sandy and light in colour with little organic matter and with an increase in clay content with depth. The soils are invariably acid and very rich in silica (Kerfoot 1987). Vegetation Current vegetation This tall grassland occurs over vast areas, usually on shallow, leached soils on the Johannesburg Granite Dome. Disturbed grassland or other disturbed areas such as road reserves or old fields, not cultivated for some years, are also usually Hyparrhenia species-dominated and low in species rich- ness. Although some of these tall grasslands appear to be quite natural, they are mostly associated with an anthropogenic influence from recent or even iron-age times. These grasslands are characterised by the tall-growing dominant grass Hyparrhenia hirta and the invader dwarf shrub Seriphium plumosum (=Stoebe vulgaris), indicating its low successional status or degraded condi- tion. Dense Hyparrhenia species-dominated grass- land mostly has low species richness, with only a few other species able to establish or survive in the shade of the dense sward of tall grass. Most of these species are relict pioneers or early seral species. The most prominent species include the grasses Cyno- don dactylon, Eragrostis chloromelas, E. racemosa, E. curvula and Aristida congesta. Forbs are rarely encountered, though a few individuals of species such as Anthospermum hispidulum, Pseudognaphalium luteo-album, Conyza albida, C. podocephala, Crabbea angustifolia, Helichrysum nudifolium and H. rugulosum are often present. The woody layer, which has a very low cover, consists of small clumps of indigenous trees and shrubs widely scattered within this grassland. The scanty woody species include the trees Rhus pyroides and Ziziphus mucronata, together with the scandent shrub Ziziphus zeyheri- ana. Declared alien invasive species such as Melia azedarach, Eucalyptus species, Pinus species and planted ornamentals are often present. Typical species found in anthropogenic Hyparrhenia hirta-dominated Egoli Granite Grassland are indicated below: bredenkamp.indd 61 2006/10/15 10:51:02 PM Koedoe 49/2 (2006) 62 ISSN 0075-6458 - Trees and Shrubs Acacia caffra (Thunb.) Willd. *Eucalyptus species Gymnosporia buxifolia L. Szysyal *Melia azedarach L. Olea europaea L. ssp. africana (Mill.) P.S.Green *Pinus species Rhus lancea L.f. Rhus leptodictya Diels Rhus pyroides Burch. Ziziphus mucronata Willd. Ziziphus zeyheriana Sond. - Grasses Aristida bipartita (Nees) Trin. & Rupr. Aristida canescens Henrard Aristida congesta Roem. & Schult. ssp. barbicollis (Trin. & Rupr.) De Winter Aristida congesta Roem. & Schult. ssp. congesta Cynodon dactylon (L.) Pers. Diheteropogon amplectens (Nees) Clayton Elionurus muticus (Spreng.) Kunth Eragrostis chloromelas Steud. Eragrostis curvula (Schrad.) Nees Eragrostis gummiflua Nees Eragrostis plana Nees Eragrostis racemosa (Thunb.) Steud. Eragrostis rigidior Pilg. Heteropogon contortus (L.) Roem. & Schult. Hyparrhenia filipendula (Hochst.) Stapf Hyparrhenia hirta (L.) Stapf Melinis repens (Willd.) Zizka Pogonarthria squarrosa (Roem. & Schult.) Pilg. Sporobolus africanus (Poir.) Robyns & Tournay Trichoneura grandiglumis (Nees) Ekman - Forbs Acalypha angustata Sond. Anthospermum hispidulum E.Mey. ex Sond. Asparagus laricinus Burch. Asparagus suaveolens Burch. Bidens formosa (Bonato) Sch.Bip. Bidens pilosa L. Chamaecrista mimosoides (L.) Greene Cirsium vulgare (Savi) Ten. Commelina africana L. Conyza albida Spreng. Cucumis zeyheri Sond. Cyperus species Elephantorrhiza elephantina (Burch.) Skeels Felicia muricata (Thunb.) Nees Gazania krebsiana Less. Geigeria burkei Harv. Gomphocarpus fruticosus (L.) Aiton f. Helichrysum nudifolium (L.) Less. Helichrysum rugulosum Less. Hermannia depressa N.E.Br. Hibiscus aethiopicus Hypoxis rigidula Lactuca species Ledebouria marginata (Baker) Jessop Nidorella hottentotica DC. Pseudognaphalium luteo-album (L.) Hilliard & B.L.Burtt Schkuhria pinnata (Lam.) Cabrera Seriphium plumosum L. Tagetes minuta L. Verbena bonariensis L. Verbena brasiliensis Vell. Vernonia oligocephala (DC.) Sch.Bip. ex Walp. Walafrida densiflora (Rolfe) Rolfe Zinnia peruviana (L.) L. Original vegetation The original vegetation is thought to be typical Bankenveld (Acocks 1988) or Rocky Highveld Grassland (Bredenkamp & Van Rooyen 1996). Bredenkamp & Brown (1998) found a few relict sites which indicate that the original vegetation on the shallow gra- nitic soils of the Johannesburg Granite Dome could have been a variant of the Monocym- bium ceressiforme-Loudetia simplex Grass- land (Bredenkamp & Brown 2003). This vegetation is found in areas where little or no disturbance is evident. The herbaceous layer covers approximately 80 % and is dominated by the grasses Loude- tia simplex, Trachypogon spicatus, Schiza- chyrium sanguineum, Monocymbium cer- esiiforme, Digitaria monodactyla, Eragrostis racemosa, Andropogon shirensis, Brachiaria serrata, Alloteropsis semialata, Bewsia biflo- ra and Themeda triandra. The woody layer consists mainly of a few scattered individuals of the trees Rhus pyroides, R. leptodictya, Ziziphus mucro- nata, the dwarf shrubs Protea welwitschii, Lopholaenia coriifolia, and the geoxylophyte Parinari capensis that are locally prominent. The grasses Panicum natalense, Urelytrum agropyroides, Tristachya leucothrix, Cym- bopogon excavatus and Elionurus muticus are also abundant together with the forbs Cyanotis speciosa, Bulbostylis burchellii, Crabbea acaulis, Anthospermum hispidulum and Senecio venosus. The grass Hyparrhenia hirta is often present and may become more prominent at disturbed sites. This grassland is characterised by a high species richness with a patchy dominance of bredenkamp.indd 62 2006/10/15 10:51:03 PM ISSN 0075-6458 63 Koedoe 49/2 (2006) # HALFWAY HOUSE GRANITE # BLACK REEF # MALMANI # MALMANI # HOSPITAL HILL #GOVERNMENT # TIMEBALL HILL # WITWATERSRAND #MULDERSDRIF # CENTRAL RAND # TURFFONTEIN # JEPPESTOWN # KLIPRIVIERSBERG # KLIPRIVIERSBERG # TIMEBALL HILL # HEKPOORT 30 0 30 60 Km Ab12 Fa18 Ab2 Ab11 Bb1 Bb2 Ab6 Ab1 Ba9 Ba7 Ba8 Ib4 Ba35 Ab7 Ab7 Bb3 Ba1 Ba36 Fa12 Ba44 Ab4 Fa17 Ib4 Ib41 Ib43 Ib4 Ib7 Ib6 Ib6 Bb3 Fb14 N N Fig. 3. Land Types (above) and Geology (bottom) within the Egoli Granite Grassland various grass species and a large variety of forbs (Louw 1970), representing a climax or close to climax condition. Grazing by cattle is often found in this vegetation type, but the dominance of sour grass species often results in a low nutrient status of the grass during winter (Kerfoot 1987; Bredenkamp & Van Rooyen 1996). Typical species found in the original Egoli Granite Grassland are indicated below: - Trees and shrubs Acacia caffra (Thunb.) Willd. Celtis africana Burm.f. Elephantorrhiza elephantina (Burch.) Skeels Gymnosporia buxifolia L. Szysyal Olea europaea L. ssp. africana (Mill.) P.S.Green Rhus lancea L.f. Rhus leptodictya Diels Rhus pyroides Burch. Ziziphus mucronata Willd. Ziziphus zeyheriana Sond. - Grasses Andropogon schirensis A.Rich. Aristida adscensionis L. Aristida canescens Henrard Aristida congesta Roem. & Schult. ssp. congesta Brachiaria serrata (Thunb.) Stapf Cymbopogon excavatus (Hochst.) Stapf ex Burtt Davy Cymbopogon pospischilli (K.Schum.) C.E. Hubb Cynodon dactylon (L.) Pers. Digitaria brazzae (Franch.) Stapf Diheteropogon amplectens (Nees) Clayton Elionurus muticus (Spreng.) Kunth Eragrostis chloromelas Steud. Eragrostis curvula (Schrad.) Nees Eragrostis racemosa (Thunb.) Steud. Harpochloa falx (L.f.) Kuntze Heteropogon contortus (L.) Roem. & Schult. Hyparrhenia hirta (L.) Stapf Melinis repens (Willd.) Zizka Monocymbium ceresiiforme (Nees) Stapf Panicum natalense Hochst. Schizachyrium sanguineum (Retz.) Alston Sporobolus pectinatus Hack. Themeda triandra Forssk. Trachypogon spicatus (L.f.) Kuntze Trichoneura grandiglumis (Nees) Ekman Tristachya leucothrix Nees Tristachya rehmannii Hack - Forbs Acalypha angustata Sond. Aloe transvaalensis Kuntze Aloe greatheadii Schönland Anthericum species Anthospermum hispidulum E.Mey. ex Sond. Asparagus suaveolens Burch. Aster bakeranus Burtt Davy ex C.A.Sm. Babiana hypogea Burch. Becium obovatum (E.Mey. ex Benth.) N.E.Br. Blepharis subvolubilis C.B.Clarke Boophane disticha (L.f.) Herb. Bulbostylis hispidula (Vahl) R.W.Haines Chascanum hederaceum (Sond.) Moldenke var. hederaceum Chaetacanthus burchellii Nees Chlorophytum fasciculatum (Baker) Kativu Crabbea acaulis N.E.Br. Crabbea angustifolia Nees Crassula capitella Thunb. ssp. capitella Crinum bulbispermum (Burm.f.) Milne-Redh. & Schweick. bredenkamp.indd 63 2006/10/15 10:51:03 PM Koedoe 49/2 (2006) 64 ISSN 0075-6458 Cucumis zeyheri Sond. Dicoma anomala Sond. Eriosema cordatum E.Mey. Eulophia species Felicia muricata (Thunb.) Nees Gladiolus crassifolius Baker Gnidia capitata L.f. Haplocarpha scaposa Harv. Helichrysum aureonitens Sch.Bip. Helichrysum miconiifolia Hilliard Helichrysum nudifolium (L.) Less. Hermannia depressa N.E.Br. Hypericum aethiopicum (Bret.) N.K.B. Hypericum lalandii Choisy Hypoxis hemerocallidea Fisch. & Mey. Hypoxis multiceps Buchinger ex Baker Hypoxis rigidula Baker Ipomoea obscura (L.) Ker Gawl. Ipomoea ommaneyi Rendle Justicia anagalloides (Nees) T.Anderson Kohautia amatymbica Eckl. & Zeyh. Ledebouria ovatifolia (Baker) Jessop Ledebouria marginata (Baker) Jessop Lotononis foliosa Bolus Mariscus congestus (Vahl) C.B.Clarke Neorautanenia ficifolius (Benth.) C.A.Sm. Pentanisia angustifolia (Hochst.) Hochst. Pentanisia prunelloides Klotzsch ex Eckl. & Zeyh.) Walp. Raphionacme hirsuta (E.Mey.) R.A.Dyer ex E.Phillips Scabiosa columbaria L. Schistostephium crataegifolium (DC.) Fenzl ex Harv. Senecio venosus Harv. Tephrosia capensis (Jacq.) Pers. Triumfetta sonderi Ficalho & Hiern Tulbaghia acutiloba Harv. Turbina oblongata (E.Mey. ex Choisy) A.Meeuse Ursinia nana DC. Vernonia natalensis Sch.Bip. ex Walp. Vernonia oligocephala (DC.) Sch.Bip. ex Walp. Origin of the current vegetation The shallow, nutrient-poor soils provide a habitat suited to the climax vegetation as dis- cussed previously. Some nutrients are avail- able in the topsoil, supplemented from fallen leaf litter and decomposition, and also from ashes of burned herbaceous layer (if there was a fire). Nutrients are quickly utilised by plants and are furthermore also quickly leached from the very coarse sandy soils. Nutrient cycling is therefore very rapid. The system is quite stable and fairly predict- able without much change caused by normal droughts or grazing. However, if overgrazed or disturbed to such an extent that degradation proceeds beyond a threshold, then recovery is very slow, due to reduced nutrient cycling and decreased nutrient availability and the vegetation may change to another domain of attraction (Bosch 1989), different from the original climax vegetation, representing a plagioclimax (Fig. 4). A change back to the original domain of attraction is unlikely if not impossible in the short and medium term. Due to the granitically derived shallow nutrient poor soils these systems are sensi- tive and intolerant to frequent impacts such as heavy grazing, ploughing, trampling and general domestic activities. Thus degradation occurs easily resulting in a change from the climax (high species richness) vegetation to an anthropogenic Hyparrhenia hirta (low species richness) dominated vegetation type. Very often Hyparrhenia species-dominated grasslands occur on ancient lands in the Central Variation of the Bankenveld (Acocks 1988) and in the surroundings of archaeo- logical sites (Bredenkamp & Brown 2003), where the inhabitants had a mosaic of cul- tivated lands and grazing of domestic stock. The more recent European settlers also had a profound effect on the natural vegetation as they developed the cities of Johannesburg and Pretoria following the discovery of gold more than a century ago. It seems that the degraded sites developed into Hyparrhenia species-dominated grasslands, which tend to be stable for a very long time. Moll (1965) and Smits et al. (1999) also indicated that Hyparrhenia species-dominated tall grass- lands are anthropogenic in origin. Importance The substrate of the Johannesburg Granite Dome (Halfway House Granites, Fig. 3) is suitable for development. The area is well situated between Johannesburg, the economic powerhouse of South Africa, and Pretoria the administrative capital of the country. There is an enormous demand for develop- able land in this area, which has resulted in the loss of large tracts of the original Egoli Granite Grassland. Due to general distur- bance, ploughing and degradation, an esti- bredenkamp.indd 64 2006/10/15 10:51:04 PM ISSN 0075-6458 65 Koedoe 49/2 (2006) mated 60 % of the remaining original Egoli Granite Grassland has been transformed to Hyparrhenia hirta dominated grassland. Only relatively small scattered pockets of the original grassland are still intact and these are considered rare and highly threat- ened. Due to its high species richness and restricted occurrence, this endemic grassland has a high conservation value. Furthermore, the bottomland areas and wet- lands within the Egoli Granite Grassland provide suitable habitat for various sensitive fauna species such as the Grass Owl Tyto capensis (Red Listed), Marsh Sylph Metisel- la meninx (Vulnerable), and the Giant Bull- frog Pyxicephalus adspersus (Near Threat- ened). Pioneer Original Egoli Granite Grassland Sere Sere Plagioclimax Domain of attraction II Domain of attraction I Hyparrhenia dominated grassland Threshold = Degradation = Succession Conclusion Egoli Granite Grassland is a poorly con- served, severely transformed, highly frag- mented and degraded vegetation type. It is estimated that only 22 % of the original extent of Egoli Granite Grassland remains in its original state. Many of these remnant areas are likely to be destroyed in the near future due to previously authorised develop- ments (e.g. Cosmo City to the north-west of Johannesburg) or illegal activities. It is therefore essential that any viable remnant patch of original Egoli Granite Grassland is conserved. Areas associated with transformed grassland, where Hyparrhenia hirta is dominant and species richness is low, have a low value with respect to achieving the national conserva- tion target for Egoli Granite Grassland. It should be noted however, that Hyparrhenia hirta dominated grassland may be valuable for the conservation of sensitive fauna, e.g. Grass Owl (Tyto capensis) and Giant Bull- frog (Pyxicephalus adspersus). A mixture of various grasses and high forb diversity renders the original Egoli Granite Grassland with a high conservation value and conservation of remnant areas is especially important since it is unlikely that the trans- formed anthropogenic grassland will return to the original climax vegetation. Since Egoli Granite Grassland is endemic to Gauteng, its protection is both a provincial and national priority. 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