Grobler.qxd Natural woodland vegetation and plant species richness of the urban open spaces in Gauteng, South Africa C.H. GROBLER, G.J. BREDENKAMP and L.R. BROWN Grobler, C.H., G.J. Bredenkamp and L.R. Brown. 2002. Natural woodland vegetation and plant species richness of the urban open spaces in Gauteng, South Africa. Koedoe 45(1): 19–34. Pretoria. ISSN 0075-6458. It is estimated that approximately 60 % of the world’s population will be living in urban areas by 2025. In Gauteng, the most densely populated province in South Africa, the nat- ural open spaces are continually under threat from development. Vegetation is the most physical representation of the environment on which all animals are ultimately depen- dent. In order to evaluate an areas potential for development or conservation it is nec- essary to make a thorough inventory of the plant communities and their associated habi- tats. A survey of the natural woodlands was undertaken as part of a project describing the vegetation of the natural open spaces within the Gauteng region. Relevés were com- piled in 73 stratified random sample plots in selected open spaces within the study area. A TWINSPAN classification, refined by Braun-Blanquet procedures, indicated six woodland communities that can be grouped into two major woodland communities. A classification and description of these communities as well as their species richness are presented. The results indicate that there are still patches of well-preserved natural veg- etation within the study area and contribute to the limited knowledge that presently exists for the vegetation of the area. Key words: Braun Blanquet analysis, classification, plant communities, urban open space, TWINSPAN. C.H. Grobler and G.J. Bredenkamp, Department of Botany, University of Pretoria, Pre- toria, 0002 South Africa; L.R. Brown , Applied Natural Sciences, Technikon SA, Pri- vate Bag X6, Florida, 1710 South Africa. ISSN 0075-6458 19 Koedoe 45/1 (2002) Introduction Although the smallest of the nine provinces of South Africa, covering an area of only 16 191 km², Gauteng has a population of approximately 7.3 million people making it the most densely populated province in South Africa (Gauteng 2000). It is therefore understandable that urbanisation and its asso- ciated impacts are the biggest threats to the natural areas that still persist in the Gauteng urban areas. Kowarik (1990) confirms this by stating that human impact has been recog- nised as one of the most important influences on the composition of vegetation in urban environments. These impacts often include the loss of complete habitats due to the con- struction of residential, industrial or other developments. Natural areas adjacent to urban areas are equally affected by human- related activities such as trampling, footpaths and exotic plant invasions, including stray products from gardens. Management prac- tices such as mowing of natural grasslands and changing the natural veld fire frequency also have an effect on these natural ecosys- tems. In the past, little attention was paid to the nat- ural environment when making decisions on development in Gauteng. By overlooking the natural environment in urban development planning, wasteful exploitation of the natural resources occurred (Bredenkamp & Brown 1998a, 1998b). In European countries, land- scape ecological mapping and evaluation Grobler.qxd 2005/12/09 11:29 Page 19 have become an essential part of the plan- ning process (Spellerberg 1992). Such plan- ning assists in restricting disturbance in areas with sensitive habitats or species and prevent undue fragmentation of wildlife habitat (Hel- liwell 1973). Until recently, vegetation sur- veys in urban areas in South Africa were unknown. After a pioneer survey in the Dur- ban Municipal Area (Roberts 1993), surveys were undertaken in the urban areas of Potchefstroom (Cilliers & Bredenkamp 1998, 1999a, 1999b, 1999c, 2000; Cilliers et. al. 1998), Klerksdorp (Van Wyk et al. 1997) in the North-West Province, and Bloem- fontein (Dingaan 1999) in the Free State. The natural areas of the Gauteng Province presently support a large number of plant species. Limited vegetation studies, mostly unpublished, have been done on small areas in the urban Gauteng (Behr & Bredenkamp 1988; Ellery 1992, 1994; Bredenkamp 1991, 1992, 1997a, 1997b; Bredenkamp & Brown 1998a, 1998b). Surveys of similar natural woodland vegetation in the Gauteng Province outside urban areas, include those of Bredenkamp & Theron (1978, 1980) and Coetzee et.al. (1993a, 1993b, 1994, 1995). The present study reports on a wider assess- ment of the vegetation of the urban areas of Gauteng, attempting to include areas of high species richness in urban areas and to con- solidate the studies previously done in the study area. The purpose of this study was therefore to identify the plant communities of different types of habitat present in the urban areas of Gauteng. This information will help to motivate conservation actions, ensuring that nature conservation strategies are incorporated into land-use planning ini- tiatives within the urban environment. Study area The study area is located between 27º40'E– 28º25'E and 25º40'S–26º20'S approximately in the center of the Gauteng province (Fig. 1) and includes Pretoria, Midrand, Johannes- burg and parts of the West Rand. Altitudes in Gauteng vary from 1081 m to 1899 m above sea level, with a mean altitude of 1512 m (Gauteng 2000). 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 in the study area is 13.8 ºC and mean summer temperature, 25.6 ºC (Weather Bureau 2000). Mean annu- al rainfall in Gauteng is 670 mm per year (Gauteng 1997). The geology of the area includes the rock types dolomite, chert, quartzite, granite, diabase, shale and andesitic lava. The most important land type units in this study area are Ab, Bb, Ba that are mainly associated with with flat or slight- ly undulating landscapes and the Ib land type which is often associated with ridge areas. The main soil forms found in the study area are Mispah and Glenrosa. (Land Type Sur- vey Staff 1985, 1987a, 1987b). Acocks (1988) described the vegetation of the study area as “False” Grassland of the Central variation of Bankenveld (Veld Type 61b). Patches of woodland vegetation are found at sheltered sites on hillslopes and rocky outcrops within this veld type. Bre- denkamp & Van Rooyen (1996a) described this vegetation as the Rocky Highveld Grass- land vegetation type, which covers the largest part of the study area. A small patch of Moist Cool Highveld Grassland (Bre- denkamp & Van Rooyen 1996b) occurs in the southeastern corner of the study area. The area, therefore, predominantly repre- sents the Grassland Biome (Rutherford & Westfall 1986). The open and closed wood- land patches in the grassland biome resemble the vegetation of the Waterberg Moist Moun- tain Bushveld (Bredenkamp & Van Rooyen 1996b) also described by Acocks (1988) as Sour Bushveld (20). The woodland layer of the area is further represented by the Mixed Bushveld vegetation type (Bredenkamp & Van Rooyen 1996a) representing the savanna biome. Currently, only 3.05 % of Mixed Bushveld and 8.55 % of the Waterberg Moist Moun- tain Bushveld is conserved (Bredenkamp & Van Rooyen 1996a, 1996c). Koedoe 45/1 (2002) 20 ISSN 0075-6458 Grobler.qxd 2005/12/09 11:29 Page 20 Methods The open spaces within the study area were identi- fied and delineated using 1:50 000 aerial pho- tographs and were stratified into relatively homoge- neous areas within which sample plots were ran- domly allocated. A total of 73 sample plots were ran- domly located within the woodland vegetation to ensure that all variations were considered and sam- pled. Plot sizes of 200 m² were used in accordance with Bredenkamp & Theron (1978). Total floristic composition was noted for every sam- ple plot. Additionally, the average height and per- centage cover of the tree, shrub and herbaceous lay- ers were estimated and recorded. The percentage cover of bare soil was also estimated and recorded. The coverage of the tree layer was based on crown cover where the canopies are vertically projected onto the ground (Werger 1974) The same technique was used for the shrub and herbaceous layers. The dominant tree, shrub, and herbaceous species were noted and the cover/abundance for each species was estimated according to the Braun Blanquet cover- abundance scale (Mueller-Dombois & Ellenberg 1974). Environmental data included slope inclination mea- sured in degrees, topography including hills, slopes and crests, aspect (north, south, west, east, and aspects in between) and disturbance factors such as exotic vegetation, trampling and erosion. Informa- tion on geology, land type, soil forms and clay con- tents were obtained from Land Type Survey Staff (1985, 1987). Soil classification is according to Macvicar (1991). The computer programme TURBOVEG (Hennekens 1996a) and the TWINSPAN classification algorithm (Hill 1979) were used for capture, processing and presentation of phytosociological data. Further refinement was achieved with Braun Blanquet pro- cedures by using MEGATAB (Hennekens 1996b), a visual editor for phytosociological tables. Names and authors of taxa are in accordance with Arnold & De Wet (1993). For the purposes of this study, Aloe greatheadii var. davyana and Aloe trans- vaalensis were lumped as one species and referred to as Aloe greatheadii var. davyana. The classification of species growth forms were done according to Van Wyk & Malan (1998). ISSN 0075-6458 21 Koedoe 45/1 (2002) Fig. 1. Location of the study area within the Gauteng Province. Grobler.qxd 2005/12/09 11:29 Page 21 Results A mixture of tree, shrub and herbaceous species characterises the woodland areas of the entire study area. General species present in the woodlands are listed under Species Group K (Table 1). The vegetation of all the woodland commu- nities is characterised by the presence of the small trees Diospyros lycioides, Canthium gilfillanii, Zanthoxylum capensis, Rhus lep- todictya, Maytenus heterophylla and Roth- mannia capensis together with the exotics Lantana camara and Solanum mauritianum. The small shrub Asparagus suaveolens, the forbs Commelina africana, Helichrysum rugulosum, the succulent Aloe greatheadii var. davyana, the slender twining herb Pen- tarrhinum insipidum, the exotic weeds Tagetes minuta, Bidens pilosa, the noxious parasite Cuscuta campestris and the fern Pellaea calomelanos are often encountered. Common grasses include Melinis repens, Melinis nerviglumis, Themeda triandra, Setaria sphacelata, Cymbopogon validus, Panicum maximum, Hyparrhenia hirta, Era- grostis curvula, Brachiaria serrata, Hetero- pogon contortus and Digitaria eriantha. These species are listed in Species Group K (Table 1) and will therefore not be repeated in the description of the various plant com- munities. Hills and ridges in the study area are often covered by a mosaic of open woodland on the warmer and drier north-facing slopes, closed woodland in more sheltered sites below rocky cliffs, and grassland patches on more exposed, high altitude areas. Closed woodland communities are also found along rivers and streams. Cooler south-facing slopes may have Protea caffra woodland communities. Two major plant communities were identi- fied namely the Acacia caffra-Rhus pyroides open to closed Major Woodland community, mostly found on cooler and more moist, south facing, or exposed habitats and the Combretum molle-Setaria lindenbergiana Open to Closed Major Woodland communi- ty, mostly associated with warmer and drier north-facing slopes. The classification obtained from the TWINSPAN and refined by Braun-Blanquet procedures resulted in the following six plant communities that can be grouped into two major communities being identified in the woodland areas surveyed. 1. Acacia caffra – Rhus pyroides Open to Closed Major Woodland Community 1.1 Hypoestes forskaolii – Acacia caffra Closed Woodland Community 1.2 Acacia caffra – Setaria lindenber- giana Closed Woodland Community 1.3 Acacia caffra – Themeda triandra Open to Closed Woodland Communi- ty 1.3.1 Acacia caffra – Themeda triandra – Asparagus laricinus Open to Closed Woodland Sub-community 1.3.2 Acacia caffra – Themeda triandra – Hyparrhenia hirta Open to Closed Woodland Sub-community 2. Combretum molle–Setaria lindenbergiana Open to Closed Major Woodland Com- munity 2.1 Combretum molle – Burkea africana Open to Closed Woodland Communi- ty 2.2 Combretum molle – Englerophytum magalismontanum Open Woodland Community Discussion Floristically the Acacia caffra-Rhus pyroides Open to Closed Woodland shows strong floristic relationships with the Sub-humid Cool Temperate Mountain Bushveld of Coetzee et al. (1995), and also exhibits an affinity to the Afro-montane vegetation of the Drakensberg. The plant species composi- tion of the Combretum molle-Setaria linden- bergiana Open to Closed Woodland relates to the Sub-humid Warm Temperate Bushveld as described by Coetzee et al. (1993b), and shows an affinity to the Bushveld vegetation Koedoe 45/1 (2002) 22 ISSN 0075-6458 Grobler.qxd 2005/12/09 11:29 Page 22 of the Savanna Biome (Rutherford & West- fall 1986). Bredenkamp & Brown (1998a, 1998b) also described vegetation to the west and north of Johannesburg indicating floris- tic resemblance to this vegetation unit. The vegetation of the Ruimsig Entomological Reserve in Roodepoort, also shows a floristi- cal resemblance to the woodland species identified in this study (Deutschländer & Bredenkamp 1999). The common species associated with the Rhus pyroides Forest and Canthium gilfil- lanii-Aristida transvaalensis-Cymbopogon marginatus Savanna communities identified by Bredenkamp & Theron (1978), and the Euclea crispa-Rhoicissus tridentata Bush and Savanna communities as well as the Tra- chypogon spicatus-Themeda triandra Grass- land communities Bredenkamp & Theron (1980) compare well with the common species identified in the woodland communi- ties for this study. Vegetation description 1. Acacia caffra – Rhus pyroides Open to Closed Major Woodland Community Habitat This plant community is found scattered throughout the study area, among granite boulders, on rocky outcrops and hills. Slopes varies from gradual to very steep. A total of 54 % of the sample plots were on the Bb, and Ib land types. This plant community occurs on rocky areas with shallow soils and is associated with the Glenrosa , Mispah and Wasbank soil forms, with a clay content of 10–30 %. Vegetation Species group A (Table 1) characterises this community. The diagnostic species are the trees Acacia caffra, Celtis africana, Rhus pyroides, Ehretia rigida, Dombeya rotundi- folia, Ziziphus mucronata, Cussonia panicu- lata, Heteromorpha trifoliata and Euclea crispa, the geophytes Ledebouria revoluta and Scadoxus puniceus, the exotic perennial weed Achyranthes aspera, and the annual weed Conyza albida. The species that dominate this plant commu- nity are the trees Rhus leptodictya, Celtis africana, Acacia caffra, Canthium gilfillanii and Zanthoxylum capense, the shrub Diospy- ros lycioides and small shrub Asparagus suaveolens, the succulent Aloe greatheadii var. davyana, the common weed Tagetes minuta, the asteraceous forb Helichrysum rugulosum, and the grasses Themeda trian- dra, Hyparrhenia hirta and Setaria sphace- lata. The high occurrence of the weed Tagetes minuta as well as the other exotic weedy species Verbena bonariensis, Conyza albida, Lantana camara, Zinnia peruviana and the succulent Opuntia ficus-indica in the herba- ceous layer together with Melia azedarach in the shrub and tree layer, indicates that this plant community is susceptible to distur- bance and generally not in a good condition in the study area. An average of 37 species per 200 m² was recorded in this plant community. In general, the species composition of this community compares well with that of the Acacia caffra – Euclea crispa woodland within the Sub-humid Cool Temperate Mountain Bushveld described by Coetzee et al. (1994, 1995), found on north-facing slopes, crests and upper south-facing steep slopes of the rocky outcrops mainly within the Ib Land Type in the Pretoria area. This community also shows floristic resem- blance with the Acacia caffra – Setaria spacelata Closed Woodland described by Coetzee et al. (1995), the Acacia caffra – Setaria sphacelata Closed Woodland in the Roodeplaatdam Nature Reserve (Van Rooyen 1984), the vegetation on the Bron- berg in Pretoria (Bredenkamp 1997), the Olea europaea – Cymbopogon excavatus savanna and Olea europeae - Schistotephium heptalobium bush clumps vegetation of the Rietfontein Nature Reserve (Bredenkamp 1991), the Acacia robusta woodland (Ellery 1994) and the Acacia caffra vegetation of the ISSN 0075-6458 23 Koedoe 45/1 (2002) Grobler.qxd 2005/12/09 11:29 Page 23 Koedoe 45/1 (2002) 24 ISSN 0075-6458 Ta bl e 1 A ph yt os oc io lo gi ca l t ab le o f t he w oo dl an d ve ge ta tio n of th e ur ba n ar ea s of G au te ng Grobler.qxd 2005/12/09 11:29 Page 24 ISSN 0075-6458 25 Koedoe 45/1 (2002) Ta bl e 1 (c on tin ue d) Grobler.qxd 2005/12/09 11:29 Page 25 Koedoe 45/1 (2002) 26 ISSN 0075-6458 Ta bl e 1 (c on tin ue d) Grobler.qxd 2005/12/09 11:30 Page 26 ISSN 0075-6458 27 Koedoe 45/1 (2002) Ta bl e 1 (c on tin ue d) Grobler.qxd 2005/12/09 11:30 Page 27 Fort Klapperkop Area in Pretoria (Bre- denkamp 1997b). The Kloof communities: Rhus pyroides Forests, Rhus pyroides-Bud- dleja salviifolia-Celtis africana Forest and Dombeya rotundifolia-Ziziphus mucronata savanna identified by Bredenkamp & Theron (1978) also show resemblance to this com- munity. Bredenkamp & Brown (1998a, 1998b) described similar vegetation to the west and north of Johannesburg. Three communities were recognised under this major woodland community: 1.1 Hypoestes forskaolii – Acacia caffra Closed Woodland Community Habitat This woodland community is found on grad- ual to moderately steep slopes and a variety of aspects of hills, ridges and between gran- ite boulders as well as along rivers in lower lying areas in the Pretoria, Midrand, Sandton and Randburg areas. A 10-15 % clay content was observed in the soils associated with this plant community. This plant community was predominantly found in the Bb Land Type. Vegetation This community is characterised by the pres- ence of the trees Combretum erythrophyllum and Rhamnus prinoides (along rivers), Aca- lypha glabrata, Pavetta gardeniifolia var. gardeniifolia and Buddleja saligna, the shrub Asparagus sp. and the shrublet Aerva leucura, the herb Hypoestes forskaolii, the erect Cyperus esculentus the shrubby peren- nial herb Hibiscus calyphyllus, the exotic climber Araujia sericifera and the grass Setaria megaphylla (Species group B Table 1) Prominent species in this plant community include the trees Rhus pyroides, Celtis africana, Acacia caffra, Euclea crispa, Can- thium gilfillanii, Rhus leptodictya, Zanthoxy- lum capense, the shrub Diospyros lycioides, the small shrub Asparagus suaveolens, and the weeds Achyranthes aspera and Tagetes minuta. The average number of species recorded in this plant community per 200 m² is 32. Showing resemblance to this community is the Combretum erythrophyllum - Celtis africana Major Community described by Behr & Bredenkamp (1988) from the Wit- watersrand Botanic Garden in Roodepoort and the Celtis africana – Ziziphus mucrona- ta community (Bredenkamp 1997b) from the Fort Klapperkop area in Pretoria and the Lonehill Nature Reserve (Bredenkamp 1992). Bredenkamp (1992) conducted a more detailed assessment on the small Lone- hill Nature Reserve and described more communities. Bredenkamp & Brown (1998a, 1998b) described vegetation to the west and north of Johannesburg indicating resem- blance to this community. 1.2 Acacia caffra – Setaria lindenber- giana Closed Woodland Community Habitat This closed woodland community has a lim- ited distribution in the study area. It was observed on steep to very steep, north and south-facing slopes of hills and ridges throughout the study area except in the Midrand-Fourways area. It is generally asso- ciated with the Land Type Ib. Vegetation The species group C (Table 1) is diagnostic for this plant community. The diagnostic species are the grass Setaria lindenbergiana and the climber shrub Rhoicissus tridentata. The most prominent species in this plant community include the trees Acacia caffra, Celtis africana and Euclea crispa, the shrub Diospyros lycioides and the bulbous geo- phyte Ledebouria revoluta, the noxious weed Tagetes minuta and the succulent Aloe greatheadii var. davyana. Disturbance to this plant community was recorded at most of the sites, with specific reference to the low herbaceous cover under the trees. An average of 31 species per 200 m² was recorded for this plant community. Koedoe 45/1 (2002) 28 ISSN 0075-6458 Grobler.qxd 2005/12/09 11:30 Page 28 This community is related to the Setaria lin- denbergiana – Ehretia rigida Bush clumps (Coetzee et al. 1995), the Setaria lindenber- giana – Acacia caffra Woodland described by Coetzee (1975) from the Rustenburg Nature Reserve, and the Olea europaea – Cymbopogon excavatus savanna and Olea europaea - Schistotephium heptalobium bush clumps vegetation of the Rietfontein Nature Reserve (Bredenkamp 1991). 1.3 Acacia caffra – Themeda triandra Open to Closed Woodland Communi- ty Habitat This open to closed woodland sub-communi- ty was found distributed throughout the study area on a variety of aspects, on gradual to moderately steep slopes of hills and ridges. It was recorded predominantly on Land Type Ib, characterised by Mispah and Glenrosa soil forms with a clay content of 10–20 %. Vegetation The diagnostic species for the community are the small tree Rhus zeyheri, the grasses Eragrostis chloromelas, Aristida congesta subsp. barbicollis, the geophyte Hypoxis rigidula, the forbs Nidorella hottentotica, Graderia subintegra, Pearsonia sessilifolia subsp. sessilifolia, Justicia anagalloides, Crabbea angustifolia and Scabiosa colum- baria, the small shrub Lantana rugosa and the exotic shrub Solanum elaeagnifolium (Species group D – Table 1). The woody layer is dominated by trees Rhus pyroides, Canthium gilfillanii, Rhus leptod- ictya, and the shrub Diospyros lycioides, together with the shrublet Asparagus suave- olens. The succulent Aloe greatheadii var. davyana, the asteraceous Helichrysum rugu- losum, the weed Tagetes minuta together with the grasses Themeda triandra, Hypar- rhenia hirta, Brachiaria serrata and Setaria sphacelata are also prominent. The average number of species recorded in this plant community per 200 m² is 41. In parts of the plant community stands of Protea caffra (Species Group F) and the scarcer Protea roupelliae (Species Group F) are prominent, indicating an affinity with the Drakensberg Highveld Sourveld (Sourveld) vegetation. The Olea europaea – Cymbopogon excava- tus savanna and Olea europeae - Schis- totephium heptalobium bush clumps vegeta- tion of the Rietfontein Nature Reserve (Bre- denkamp 1991) also show resemblance to this community. Two sub-communities are recognised: 1.3.1 Acacia caffra – Themeda triandra – Asparagus laricinus Closed Wood- land Sub-community Habitat This sub-community is found on gradual north and south-facing slopes predominantly in the Pretoria area, but also in Clayville, Fourways and Alberton. This plant commu- nity is associated with closed woodland in association with rocky outcrops. This plant community was recorded from the Ib1b land types. Vegetation Species that dominate the plant community are the trees Acacia caffra, Celtis africana and Ehretia rigida, the shrublet Asparagus suaveolens, the grasses Themeda triandra, Setaria sphacelata, the succulent Aloe great- headii var. davyana and the asteraceous Helichrysum rugulosum. Rhus pyroides is locally dominant and Panicum maximum is sometimes prominent. Species group E (Table 1) is diagnostic for this community. Diagnostic tree species include Acacia karroo, the shrub Asparagus laricinus that forms impenetrable thickets, the slender shrub Sida dregei, the erect shrublets Hibiscus lunarifolius and Teucrium trifidum, the herbaceous shrublet Pavonia burchellii, the twining forb Clematis brachi- ata, the forb Conyza podocephala and the exotic weeds Oxalis corniculata and Conyza albida. ISSN 0075-6458 29 Koedoe 45/1 (2002) Grobler.qxd 2005/12/09 11:30 Page 29 The average number of species recorded in this plant community per 200 m² is 36. The Acacia karroo – Lippia javanica closed woodland (Coetzee et al. 1995) shows resemblance to this community. 1.3.2 Acacia caffra – Themeda triandra – Hyparrhenia hirta Open to Closed Woodland Sub-community Habitat This sub-community is found throughout the study area on a variety of aspects and on gradual to steep slopes of ridges and hills and rocky outcrops. This plant community is prominent on the higher altitude slopes and crests. Vegetation Species group F (Table 1) is diagnostic for this vegetation. The diagnostic species are the trees Kiggelaria africana, Protea caffra, Protea roupelliae and Rhus pyroides, the shrublets Athrixia elata, Pentanisia angusti- folia, Rhus discolor, and shrub Lippia javan- ica, the forbs Chaetacanthus costatus, Ver- nonia galpinii and Rhynchosia totta, and the grasses Tristachya leucothrix, Eragrostis racemosa, Cynodon dactylon, Elionurus muticus and Alloteropsis semialata subsp. eckloniana. The plant community is dominated by the tree species Rhus leptodictya and Canthium gilfillanii the shrub Diospyros lycioides, the succulent Aloe greatheadii var. davyana, the asteraceous Helichrysum rugulosum and the grasses Setaria sphacelata, Melinis repens, Melinis nerviglumis, Themeda triandra, Hyparrhenia hirta and Brachiaria serrata. An average of 44 species per 200 m² was recorded in this plant community. This community resembles the Protea caffra – Athrixia elata Open Woodland (Coetzee 1995) from the Pretoria area. The common species of the Tracypogon spicatus-Themeda triandra Grassland of Bredenkamp & There- on (1980) compare well with this communi- ty. Bredenkamp & Brown (1998a, 1998b) described vegetation to the west and north of Johannesburg indicating resemblance to this vegetation unit. 2. Combretum molle–Setaria lindenbergiana Open to Closed Major Woodland Com- munity Habitat This plant community is mostly found on warmer and drier north-facing aspect on gradual to very steep slopes in kloofs, between granite boulders and on rocky out- crops, drainage lines, at the foot of quartzite ridges and hills and on rocky outcrops in the Pretoria and Johannesburg area. This plant community is mainly found in the Ib and Ba land types. Vegetation The diagnostic species of this plant commu- nity are the trees Combretum molle, Vangue- ria infausta, Ochna pulchra, Combretum zeyheri, Nuxia congesta, Lannea discolor and Englerophytum magalismontanum. Other species include the shrub Ochna pre- toriensis, the shrublet Indigofera melanade- nia, and the succulents Kalanchoe panicula- ta, Crassula swaziensis and Euphorbia schinzii, forbs such as the tufted Coleochloa setifera, Commelina erecta, Oldenlandia herbacea var. herbacea and grasses such as Setaria lindenbergiana and Loudetia simplex (Species group G; Table 1). The species that dominate this plant commu- nity are the succulent Aloe greatheadii var. davyana, the weed Tagetes minuta, the herb Commelina africana and the scrubby Xero- phyta retinervis, the fern Pellaea calome- lanos, and the grasses Cymbopogon validus, Melinis repens, Melinis nerviglumis and Diheteropogon amplectens. An average of 38 species per 200 m² was recorded in this plant community. Invasion of exotic vegetation was often recorded in this plant community. Invasive exotic species include Lantana camara, Cereus peruviana and Jacaranda mimosifo- lia. Koedoe 45/1 (2002) 30 ISSN 0075-6458 Grobler.qxd 2005/12/09 11:30 Page 30 In general, this community compares well with the Sub-humid Warm Temperate Moun- tain Bushveld found on north-facing slopes, crests, and upper south-facing steep slopes of the rocky outcrops mainly within the Ib land type (Coetzee et al. 1995). Also resem- bling this community are the Burkea africana–Bequartiodendron magalismon- tanum Open Woodland (Coetzee 1994), Setaria lindenbergiana-Combretum molle community (Bezuidenhout 1993), Sporobolus pectinatus–Chaetacanthus setiger communi- ty (Coetzee 1993), Canthium gilfillanii– Combertum molle savanna community from the Witwatersrand National Botanic Garden (Behr & Bredenkamp 1988), Nuxia conges- ta-Combretum molle savanna (Bezuidenhout et al. 1988) vegetation on the Bronberg in Pretoria (Bredenkamp 1997a), the Cryp- tolepis oblongifolia–Englerophytum, Burkea africana–Combretum molle and Brachylae- na rotundata–Burkea africana communities from the Fort Klapperkop Area (Bre- denkamp 1997b). Two sub-communities were recognised: 2.1 Combretum molle – Burkea africana Open to Closed Woodland Community Habitat This sub-community is predominantly found on shallow to moderately steep northern to north-eastern slopes of ridges and hills in the Pretoria area. It was mainly recorded in 1b Land Type. Vegetation Species group H (Table 1) is diagnostic for this sub-community. Diagnostic species include the trees Burkea africana and Strychnos pungens and the dwarf shrubs Rhynchosia nitens and Helichrysum kraussii and geoxylic suffrutescent Dichapetalum cymosum. The most prominent species in this plant community are the trees Combretum molle and Vangueria infuasta, the shrubs Xerophy- ta retinervis, the succulent Aloe greatheadii var. davyana, the fern Pellaea calomelanos and the grass Melinis nerviglumis. The average number of species recorded in this plant community is 40 per 200 m². 2.2 Combretum molle – Englerophytum magalismontanum Open Woodland Community Habitat This sub-community was found at high alti- tudes on northern aspects with gradual to very steep (55º and 50º at Bush Hill in Rand- burg and on Northcliff Hill in Northcliff) slopes, on top of ridges and hills, and in drainage lines on ridges in the Pretoria and Johannesburg areas. The plant community was recorded specifically in land types Ba and Ib. The soil form is mainly Mispah with a clay content of 10–20 % also indicating shallow soils on rock. Vegetation This sub-community is characterised by Species group I (Table 1). Characteristic species associated with this plant communi- ty are the trees Pittosporum viridiflorum, Croton gratissimus, Osyris lanceolata and Pouzolzia mixta and the shrubs Ancylobotrys capensis and Rhus magalismontana and the sbrublet Waltheria indica. Other species include forbs like the succulent Crassula setulosa, Vernonia sutherlandii, Cyperus sp. and Sutera caerulea and the grasses Aristida transvaalensis and Enneapogon scoparius. Species that dominate the plant community are the trees Combretum molle, Vangueria infausta, Canthium gilfillanii and Diospyros lycioides the grasses Cymbopogon validus, Melinis repens and the forb Commelina africana. The average number of species recorded in this plant community is 36 per 200m². Floristically the Bequartiodendron magalis- montanum shrub land of Ellery (1994) also compares well with this community. ISSN 0075-6458 31 Koedoe 45/1 (2002) Grobler.qxd 2005/12/09 11:30 Page 31 Discussion The results of this study indicate that patch- es of well-preserved vegetation do occur in urban Gauteng. The sites chosen were rela- tively undisturbed and many could be impor- tant to conserve. Some sites are presently utilised for agricultural purposes. In spite of this, weedy species, eg., Tagetes minuta and Bidens pilosa occur on a large number of plots indicating disturbances of the herba- ceous layer. Species group J (Table 1) indicates a floristic relationship between the Acacia caffra–Themeda triandra–Hyparrhenia hirta Open to Closed Woodland and the Combretum molle–Setaria lindenbergiana Open to Closed Woodland. Both these com- munities occur on slopes of fairly high alti- tude. The classification procedures followed, resulted in clearly defined vegetation units that can be related to the environmental fac- tors observed. This classification contributes to the limited knowledge that presently exists for the vegetation of urban open spaces in Gauteng. The results of this study can be used as a baseline study and future studies can be measured against it. The species richness determined per 200 m² per vegetation type could also be used to deter- mine environmental and ecological degrada- tion and actions could be taken to manage these changes. The results of this study could further be used to determine how the surrounding land- uses have influenced the vegetation of urban open spaces. The results could assist in guiding development in future open spaces in a constantly expanding urban environ- ment. Acknowledgements The research was funded by the Gauteng Department of Agriculture, Conservation and Environment. References ACOCKS, J.P.H. 1988. 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