Natural Woodland Vegetation and Plant Species Richness of the Urban Open Spaces in Gauteng, South Africa

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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 natural 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 habitats. 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 vegetation 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.

Introduction developments. Natural areas adjacent to urban areas are equally affected by human- Although the smallest of the nine provinces related activities such as trampling, footpaths of South Africa, covering an area of only and exotic plant invasions, including stray 16 191 km², Gauteng has a population of products from gardens. Management prac- approximately 7.3 million people making it tices such as mowing of natural grasslands the most densely populated province in and changing the natural veld fire frequency South Africa (Gauteng 2000). It is therefore also have an effect on these natural ecosys- understandable that urbanisation and its asso- tems. ciated impacts are the biggest threats to the natural areas that still persist in the Gauteng In the past, little attention was paid to the nat- urban areas. Kowarik (1990) confirms this ural environment when making decisions on by stating that human impact has been recog- development in Gauteng. By overlooking the nised as one of the most important influences natural environment in urban development on the composition of vegetation in urban planning, wasteful exploitation of the natural environments. These impacts often include resources occurred (Bredenkamp & Brown the loss of complete habitats due to the con- 1998a, 1998b). In European countries, land- struction of residential, industrial or other scape ecological mapping and evaluation

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have become an essential part of the plan- sea level, with a mean altitude of 1512 m ning process (Spellerberg 1992). Such plan- (Gauteng 2000). ning assists in restricting disturbance in areas Mean monthly temperature in the study area with sensitive habitats or species and prevent is 16.8 ºC with a mean maximum of 22.6 ºC undue fragmentation of wildlife habitat (Hel- and a mean minimum of 10.8 ºC. The mean liwell 1973). Until recently, vegetation sur- winter temperature in the study area is veys in urban areas in South Africa were 13.8 ºC and mean summer temperature, unknown. After a pioneer survey in the Dur- 25.6 ºC (Weather Bureau 2000). Mean annu- ban Municipal Area (Roberts 1993), surveys al rainfall in Gauteng is 670 mm per year were undertaken in the urban areas of (Gauteng 1997). The geology of the area Potchefstroom (Cilliers & Bredenkamp includes the rock types dolomite, chert, 1998, 1999a, 1999b, 1999c, 2000; Cilliers et. quartzite, granite, diabase, shale and al. 1998), Klerksdorp (Van Wyk et al. 1997) andesitic lava. The most important land type in the North-West Province, and Bloem- units in this study area are Ab, Bb, Ba that fontein (Dingaan 1999) in the Free State. are mainly associated with with flat or slight- The natural areas of the Gauteng Province ly undulating landscapes and the Ib land type presently support a large number of plant which is often associated with ridge areas. species. Limited vegetation studies, mostly The main soil forms found in the study area unpublished, have been done on small areas are Mispah and Glenrosa. (Land Type Sur- in the urban Gauteng (Behr & Bredenkamp vey Staff 1985, 1987a, 1987b). 1988; Ellery 1992, 1994; Bredenkamp 1991, 1992, 1997a, 1997b; Bredenkamp & Brown Acocks (1988) described the vegetation of 1998a, 1998b). Surveys of similar natural the study area as “False” Grassland of the woodland vegetation in the Gauteng Central variation of Bankenveld (Veld Type Province outside urban areas, include those 61b). Patches of woodland vegetation are of Bredenkamp & Theron (1978, 1980) and found at sheltered sites on hillslopes and Coetzee et.al. (1993a, 1993b, 1994, 1995). rocky outcrops within this veld type. Bre- denkamp & Van Rooyen (1996a) described The present study reports on a wider assess- this vegetation as the Rocky Highveld Grass- ment of the vegetation of the urban areas of land vegetation type, which covers the Gauteng, attempting to include areas of high largest part of the study area. A small patch species richness in urban areas and to con- of Moist Cool Highveld Grassland (Bre- solidate the studies previously done in the denkamp & Van Rooyen 1996b) occurs in study area. The purpose of this study was the southeastern corner of the study area. therefore to identify the plant communities The area, therefore, predominantly repre- of different types of habitat present in the sents the Grassland Biome (Rutherford & urban areas of Gauteng. This information Westfall 1986). The open and closed wood- will help to motivate conservation actions, land patches in the grassland biome resemble ensuring that nature conservation strategies the vegetation of the Waterberg Moist Moun- are incorporated into land-use planning ini- tain Bushveld (Bredenkamp & Van Rooyen tiatives within the urban environment. 1996b) also described by Acocks (1988) as Sour Bushveld (20). The woodland layer of the area is further represented by the Mixed Study area Bushveld vegetation type (Bredenkamp & Van Rooyen 1996a) representing the savanna The study area is located between 27º40'E– biome. 28º25'E and 25º40'S–26º20'S approximately in the center of the Gauteng province (Fig. 1) Currently, only 3.05 % of Mixed Bushveld and includes Pretoria, Midrand, Johannes- and 8.55 % of the Waterberg Moist Moun- burg and parts of the West Rand. Altitudes in tain Bushveld is conserved (Bredenkamp & Gauteng vary from 1081 m to 1899 m above Van Rooyen 1996a, 1996c).

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Fig. 1. Location of the study area within the Gauteng Province.

Methods Environmental data included slope inclination measured in degrees, topography including hills, slopes The open spaces within the study area were identi- and crests, aspect (north, south, west, east, and fied and delineated using 1:50 000 aerial pho- aspects in between) and disturbance factors such as tographs and were stratified into relatively homoge- exotic vegetation, trampling and erosion. Informa- neous areas within which sample plots were ran- domly allocated. A total of 73 sample plots were ran- tion on geology, land type, soil forms and clay con- domly located within the woodland vegetation to tents were obtained from Land Type Survey Staff ensure that all variations were considered and sam- (1985, 1987). Soil classification is according to pled. Plot sizes of 200 m² were used in accordance Macvicar (1991). with Bredenkamp & Theron (1978). The computer programme TURBOVEG (Hennekens Total floristic composition was noted for every sam- 1996a) and the TWINSPAN classification algorithm ple plot. Additionally, the average height and per- (Hill 1979) were used for capture, processing and centage cover of the tree, shrub and herbaceous lay- presentation of phytosociological data. Further ers were estimated and recorded. The percentage refinement was achieved with Braun Blanquet pro- cover of bare soil was also estimated and recorded. cedures by using MEGATAB (Hennekens 1996b), a The coverage of the tree layer was based on crown visual editor for phytosociological tables. cover where the canopies are vertically projected onto the ground (Werger 1974) The same technique Names and authors of taxa are in accordance with was used for the shrub and herbaceous layers. The Arnold & De Wet (1993). For the purposes of this dominant tree, shrub, and herbaceous species were study, Aloe greatheadii var. davyana and Aloe trans- noted and the cover/abundance for each species was vaalensis were lumped as one species and referred to estimated according to the Braun Blanquet cover- as Aloe greatheadii var. davyana. The classification abundance scale (Mueller-Dombois & Ellenberg of species growth forms were done according to Van 1974). Wyk & Malan (1998).

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Results ty, mostly associated with warmer and drier north-facing slopes. A mixture of tree, shrub and herbaceous species characterises the woodland areas of The classification obtained from the the entire study area. General species present TWINSPAN and refined by Braun-Blanquet in the woodlands are listed under Species procedures resulted in the following six plant Group K (Table 1). communities that can be grouped into two major communities being identified in the The vegetation of all the woodland commu- woodland areas surveyed. nities is characterised by the presence of the small trees Diospyros lycioides, Canthium gilfillanii, Zanthoxylum capensis, Rhus lep- 1. Acacia caffra – Rhus pyroides Open to todictya, Maytenus heterophylla and Roth- Closed Major Woodland Community mannia capensis together with the exotics 1.1 Hypoestes forskaolii – Acacia caffra Lantana camara and Solanum mauritianum. Closed Woodland Community 1.2 Acacia caffra – Setaria lindenber- The small shrub Asparagus suaveolens, the giana Closed Woodland Community forbs Commelina africana, Helichrysum 1.3 Acacia caffra – Themeda triandra rugulosum, the succulent Aloe greatheadii Open to Closed Woodland Communi- var. davyana, the slender twining herb Pen- ty tarrhinum insipidum, the exotic weeds 1.3.1 Acacia caffra – Themeda triandra – Tagetes minuta, Bidens pilosa, the noxious Asparagus laricinus Open to Closed parasite Cuscuta campestris and the fern Woodland Sub-community Pellaea calomelanos are often encountered. 1.3.2 Acacia caffra – Themeda triandra – Common grasses include Melinis repens, Hyparrhenia hirta Open to Closed Melinis nerviglumis, Themeda triandra, Woodland Sub-community Setaria sphacelata, Cymbopogon validus, Panicum maximum, Hyparrhenia hirta, Era- grostis curvula, Brachiaria serrata, Hetero- 2. Combretum molle–Setaria lindenbergiana pogon contortus and Digitaria eriantha. Open to Closed Major Woodland Com- These species are listed in Species Group K munity (Table 1) and will therefore not be repeated 2.1 Combretum molle – Burkea africana in the description of the various plant com- Open to Closed Woodland Communi- munities. ty 2.2 Combretum molle – Englerophytum Hills and ridges in the study area are often magalismontanum Open Woodland covered by a mosaic of open woodland on Community the warmer and drier north-facing slopes, closed woodland in more sheltered sites below rocky cliffs, and grassland patches on Discussion more exposed, high altitude areas. Closed woodland communities are also found along Floristically the Acacia caffra-Rhus pyroides rivers and streams. Cooler south-facing Open to Closed Woodland shows strong slopes may have Protea caffra woodland floristic relationships with the Sub-humid communities. Cool Temperate Mountain Bushveld of Coetzee et al. (1995), and also exhibits an Two major plant communities were identi- affinity to the Afro-montane vegetation of fied namely the Acacia caffra-Rhus pyroides the Drakensberg. The plant species composi- open to closed Major Woodland community, tion of the Combretum molle-Setaria linden- mostly found on cooler and more moist, bergiana Open to Closed Woodland relates south facing, or exposed habitats and the to the Sub-humid Warm Temperate Bushveld Combretum molle-Setaria lindenbergiana as described by Coetzee et al. (1993b), and Open to Closed Major Woodland communi- shows an affinity to the Bushveld vegetation

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of the Savanna Biome (Rutherford & West- weed Achyranthes aspera, and the annual fall 1986). Bredenkamp & Brown (1998a, weed Conyza albida. 1998b) also described vegetation to the west The species that dominate this plant commu- and north of Johannesburg indicating floristic resemblance to this vegetation unit. The nity are the trees Rhus leptodictya, Celtis vegetation of the Ruimsig Entomological africana, Acacia caffra, Canthium gilfillanii Reserve in Roodepoort, also shows a floristi- and Zanthoxylum capense, the shrub Diospy- cal resemblance to the woodland species ros lycioides and small shrub Asparagus identified in this study (Deutschländer & suaveolens, the succulent Aloe greatheadii Bredenkamp 1999). var. davyana, the common weed Tagetes minuta, the asteraceous forb Helichrysum The common species associated with the rugulosum, and the grasses Themeda trian- Rhus pyroides Forest and Canthium gilfil- dra, Hyparrhenia hirta and Setaria sphace- lanii-Aristida transvaalensis-Cymbopogon lata. marginatus Savanna communities identified by Bredenkamp & Theron (1978), and the The high occurrence of the weed Tagetes Euclea crispa-Rhoicissus tridentata Bush minuta as well as the other exotic weedy and Savanna communities as well as the Tra- species Verbena bonariensis, Conyza albida, chypogon spicatus-Themeda triandra Grass- Lantana camara, Zinnia peruviana and the land communities Bredenkamp & Theron succulent Opuntia ficus-indica in the herba- (1980) compare well with the common ceous layer together with Melia azedarach in species identified in the woodland communi- the shrub and tree layer, indicates that this ties for this study. plant community is susceptible to disturbance and generally not in a good condition in the study area. Vegetation description An average of 37 species per 200 m² was recorded in this plant community. 1. Acacia caffra – Rhus pyroides Open to In general, the species composition of this Closed Major Woodland Community community compares well with that of the Habitat Acacia caffra – Euclea crispa woodland within the Sub-humid Cool Temperate This plant community is found scattered Mountain Bushveld described by Coetzee et throughout the study area, among granite al. (1994, 1995), found on north-facing boulders, on rocky outcrops and hills. Slopes slopes, crests and upper south-facing steep varies from gradual to very steep. A total of slopes of the rocky outcrops mainly within 54 % of the sample plots were on the Bb, and the Ib Land Type in the Pretoria area. Ib land types. This plant community occurs on rocky areas with shallow soils and is This community also shows floristic resem- associated with the Glenrosa , Mispah and blance with the Acacia caffra – Setaria Wasbank soil forms, with a clay content of spacelata Closed Woodland described by 10–30 %. Coetzee et al. (1995), the Acacia caffra – Setaria sphacelata Closed Woodland in the Vegetation Roodeplaatdam Nature Reserve (Van Species group A (Table 1) characterises this Rooyen 1984), the vegetation on the Bron- community. The diagnostic species are the berg in Pretoria (Bredenkamp 1997), the trees Acacia caffra, Celtis africana, Rhus Olea europaea – Cymbopogon excavatus pyroides, Ehretia rigida, Dombeya rotundi- savanna and Olea europeae - Schistotephium folia, Ziziphus mucronata, Cussonia panicu- heptalobium bush clumps vegetation of the lata, Heteromorpha trifoliata and Euclea Rietfontein Nature Reserve (Bredenkamp crispa, the geophytes Ledebouria revoluta 1991), the Acacia robusta woodland (Ellery and Scadoxus puniceus, the exotic perennial 1994) and the Acacia caffra vegetation of the

ISSN 0075-6458 23 Koedoe 45/1 (2002) Grobler.qxd 2005/12/09 11:29 Page 24 Table 1 Table A of Gauteng phytosociological table of the woodland vegetation urban areas

Koedoe 45/1 (2002) 24 ISSN 0075-6458 Grobler.qxd 2005/12/09 11:29 Page 25 (continued) Table 1 Table

ISSN 0075-6458 25 Koedoe 45/1 (2002) Grobler.qxd 2005/12/09 11:30 Page 26 Table 1 Table (continued)

Koedoe 45/1 (2002) 26 ISSN 0075-6458 Grobler.qxd 2005/12/09 11:30 Page 27 (continued) Table 1 Table

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Fort Klapperkop Area in Pretoria (Bre- The average number of species recorded in denkamp 1997b). The Kloof communities: this plant community per 200 m² is 32. Rhus pyroides Forests, Rhus pyroides-Bud- Showing resemblance to this community is dleja salviifolia-Celtis africana Forest and the Combretum erythrophyllum - Celtis Dombeya rotundifolia-Ziziphus mucronata africana Major Community described by savanna identified by Bredenkamp & Theron Behr & Bredenkamp (1988) from the Wit- (1978) also show resemblance to this com- watersrand Botanic Garden in Roodepoort munity. Bredenkamp & Brown (1998a, and the Celtis africana – Ziziphus mucrona- 1998b) described similar vegetation to the ta community (Bredenkamp 1997b) from the west and north of Johannesburg. Fort Klapperkop area in Pretoria and the Three communities were recognised under Lonehill Nature Reserve (Bredenkamp this major woodland community: 1992). Bredenkamp (1992) conducted a more detailed assessment on the small Lone- hill Nature Reserve and described more 1.1 Hypoestes forskaolii – Acacia caffra communities. Bredenkamp & Brown (1998a, Closed Woodland Community 1998b) described vegetation to the west and Habitat north of Johannesburg indicating resemblance to this community. This woodland community is found on gradual to moderately steep slopes and a variety of aspects of hills, ridges and between gran- 1.2 Acacia caffra – Setaria lindenber- ite boulders as well as along rivers in lower giana Closed Woodland Community lying areas in the Pretoria, Midrand, Sandton Habitat and Randburg areas. A 10-15 % clay content was observed in the soils associated with this This closed woodland community has a lim- plant community. This plant community was ited distribution in the study area. It was predominantly found in the Bb Land Type. observed on steep to very steep, north and south-facing slopes of hills and ridges Vegetation throughout the study area except in the This community is characterised by the pres- Midrand-Fourways area. It is generally asso- ence of the trees Combretum erythrophyllum ciated with the Land Type Ib. and Rhamnus prinoides (along rivers), Aca- Vegetation lypha glabrata, Pavetta gardeniifolia var. gardeniifolia and Buddleja saligna, the The species group C (Table 1) is diagnostic shrub Asparagus sp. and the shrublet Aerva for this plant community. The diagnostic leucura, the herb Hypoestes forskaolii, the species are the grass Setaria lindenbergiana erect Cyperus esculentus the shrubby peren- and the climber shrub Rhoicissus tridentata. nial herb Hibiscus calyphyllus, the exotic The most prominent species in this plant climber Araujia sericifera and the grass community include the trees Acacia caffra, Setaria megaphylla (Species group B Celtis africana and Euclea crispa, the shrub Table 1) Diospyros lycioides and the bulbous geo- Prominent species in this plant community phyte Ledebouria revoluta, the noxious include the trees Rhus pyroides, Celtis weed Tagetes minuta and the succulent Aloe greatheadii var. davyana. Disturbance to this africana, Acacia caffra, Euclea crispa, Can- plant community was recorded at most of the thium gilfillanii, Rhus leptodictya, Zanthoxy- sites, with specific reference to the low lum capense, the shrub Diospyros lycioides, herbaceous cover under the trees. the small shrub Asparagus suaveolens, and the weeds Achyranthes aspera and Tagetes An average of 31 species per 200 m² was minuta. recorded for this plant community.

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This community is related to the Setaria lin- In parts of the plant community stands of denbergiana – Ehretia rigida Bush clumps Protea caffra (Species Group F) and the (Coetzee et al. 1995), the Setaria lindenber- scarcer Protea roupelliae (Species Group F) giana – Acacia caffra Woodland described are prominent, indicating an affinity with the by Coetzee (1975) from the Rustenburg Drakensberg Highveld Sourveld (Sourveld) Nature Reserve, and the Olea europaea – vegetation. Cymbopogon excavatus savanna and Olea The Olea europaea – Cymbopogon excava- europaea - Schistotephium heptalobium tus savanna and Olea europeae - Schis- bush clumps vegetation of the Rietfontein totephium heptalobium bush clumps vegeta- Nature Reserve (Bredenkamp 1991). tion of the Rietfontein Nature Reserve (Bre- denkamp 1991) also show resemblance to 1.3 Acacia caffra – Themeda triandra this community. Open to Closed Woodland Communi- Two sub-communities are recognised: ty

Habitat 1.3.1 Acacia caffra – Themeda triandra – This open to closed woodland sub-communi- Asparagus laricinus Closed Wood- ty was found distributed throughout the land Sub-community study area on a variety of aspects, on gradual Habitat to moderately steep slopes of hills and ridges. It was recorded predominantly on This sub-community is found on gradual Land Type Ib, characterised by Mispah and north and south-facing slopes predominantly Glenrosa soil forms with a clay content of in the Pretoria area, but also in Clayville, 10–20 %. Fourways and Alberton. This plant community is associated with closed woodland in Vegetation association with rocky outcrops. This plant The diagnostic species for the community community was recorded from the Ib1b land are the small tree Rhus zeyheri, the grasses types. Eragrostis chloromelas, Aristida congesta Vegetation subsp. barbicollis, the geophyte Hypoxis rigidula, the forbs Nidorella hottentotica, Species that dominate the plant community Graderia subintegra, Pearsonia sessilifolia are the trees Acacia caffra, Celtis africana subsp. sessilifolia, Justicia anagalloides, and Ehretia rigida, the shrublet Asparagus Crabbea angustifolia and Scabiosa colum- suaveolens, the grasses Themeda triandra, baria, the small shrub Lantana rugosa and Setaria sphacelata, the succulent Aloe great- the exotic shrub Solanum elaeagnifolium headii var. davyana and the asteraceous (Species group D – Table 1). Helichrysum rugulosum. Rhus pyroides is locally dominant and Panicum maximum is The woody layer is dominated by trees Rhus sometimes prominent. pyroides, Canthium gilfillanii, Rhus leptodictya, and the shrub Diospyros lycioides, Species group E (Table 1) is diagnostic for together with the shrublet Asparagus suave- this community. Diagnostic tree species olens. The succulent Aloe greatheadii var. include Acacia karroo, the shrub Asparagus davyana, the asteraceous Helichrysum rugu- laricinus that forms impenetrable thickets, losum, the weed Tagetes minuta together the slender shrub Sida dregei, the erect with the grasses Themeda triandra, Hypar- shrublets Hibiscus lunarifolius and Teucrium trifidum, the herbaceous shrublet Pavonia rhenia hirta, Brachiaria serrata and Setaria burchellii, the twining forb Clematis brachi- sphacelata are also prominent. ata, the forb Conyza podocephala and the The average number of species recorded in exotic weeds Oxalis corniculata and Conyza this plant community per 200 m² is 41. albida.

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The average number of species recorded in described vegetation to the west and north of this plant community per 200 m² is 36. Johannesburg indicating resemblance to this vegetation unit. The Acacia karroo – Lippia javanica closed woodland (Coetzee et al. 1995) shows resemblance to this community. 2. Combretum molle–Setaria lindenbergiana Open to Closed Major Woodland Com- munity 1.3.2 Acacia caffra – Themeda triandra – Hyparrhenia hirta Open to Closed Habitat Woodland Sub-community This plant community is mostly found on Habitat warmer and drier north-facing aspect on gradual to very steep slopes in kloofs, This sub-community is found throughout the between granite boulders and on rocky out- study area on a variety of aspects and on crops, drainage lines, at the foot of quartzite gradual to steep slopes of ridges and hills ridges and hills and on rocky outcrops in the and rocky outcrops. This plant community is Pretoria and Johannesburg area. This plant prominent on the higher altitude slopes and community is mainly found in the Ib and Ba crests. land types. Vegetation Vegetation Species group F (Table 1) is diagnostic for The diagnostic species of this plant commu- this vegetation. The diagnostic species are nity are the trees Combretum molle, Vangue- the trees Kiggelaria africana, Protea caffra, ria infausta, Ochna pulchra, Combretum Protea roupelliae and Rhus pyroides, the zeyheri, Nuxia congesta, Lannea discolor shrublets Athrixia elata, Pentanisia angusti- and Englerophytum magalismontanum. folia, Rhus discolor, and shrub Lippia javan- Other species include the shrub Ochna pre- ica, the forbs Chaetacanthus costatus, Ver- toriensis, the shrublet Indigofera melanade- nonia galpinii and Rhynchosia totta, and the nia, and the succulents Kalanchoe panicula- grasses Tristachya leucothrix, Eragrostis ta, Crassula swaziensis and Euphorbia racemosa, Cynodon dactylon, Elionurus schinzii, forbs such as the tufted Coleochloa muticus and Alloteropsis semialata subsp. setifera, Commelina erecta, Oldenlandia eckloniana. herbacea var. herbacea and grasses such as The plant community is dominated by the Setaria lindenbergiana and Loudetia simplex tree species Rhus leptodictya and Canthium (Species group G; Table 1). gilfillanii the shrub Diospyros lycioides, the The species that dominate this plant commu- succulent Aloe greatheadii var. davyana, the nity are the succulent Aloe greatheadii var. asteraceous Helichrysum rugulosum and the davyana, the weed Tagetes minuta, the herb grasses Setaria sphacelata, Melinis repens, Commelina africana and the scrubby Xero- Melinis nerviglumis, Themeda triandra, phyta retinervis, the fern Pellaea calome- Hyparrhenia hirta and Brachiaria serrata. lanos, and the grasses Cymbopogon validus, An average of 44 species per 200 m² was Melinis repens, Melinis nerviglumis and recorded in this plant community. Diheteropogon amplectens. This community resembles the Protea caffra An average of 38 species per 200 m² was recorded in this plant community. – Athrixia elata Open Woodland (Coetzee 1995) from the Pretoria area. The common Invasion of exotic vegetation was often species of the Tracypogon spicatus-Themeda recorded in this plant community. Invasive triandra Grassland of Bredenkamp & There- exotic species include Lantana camara, on (1980) compare well with this communi- Cereus peruviana and Jacaranda mimosifo- ty. Bredenkamp & Brown (1998a, 1998b) lia.

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In general, this community compares well var. davyana, the fern Pellaea calomelanos with the Sub-humid Warm Temperate Moun- and the grass Melinis nerviglumis. tain Bushveld found on north-facing slopes, The average number of species recorded in crests, and upper south-facing steep slopes of the rocky outcrops mainly within the Ib this plant community is 40 per 200 m². land type (Coetzee et al. 1995). Also resem- bling this community are the Burkea 2.2 Combretum molle – Englerophytum africana–Bequartiodendron magalismon- magalismontanum Open Woodland tanum Open Woodland (Coetzee 1994), Community Setaria lindenbergiana-Combretum molle community (Bezuidenhout 1993), Sporobolus Habitat pectinatus–Chaetacanthus setiger communi- This sub-community was found at high alti- ty (Coetzee 1993), Canthium gilfillanii– tudes on northern aspects with gradual to Combertum molle savanna community from very steep (55º and 50º at Bush Hill in Rand- the Witwatersrand National Botanic Garden burg and on Northcliff Hill in Northcliff) (Behr & Bredenkamp 1988), Nuxia conges- slopes, on top of ridges and hills, and in ta-Combretum molle savanna (Bezuidenhout drainage lines on ridges in the Pretoria and et al. 1988) vegetation on the Bronberg in Johannesburg areas. The plant community Pretoria (Bredenkamp 1997a), the Cryp- was recorded specifically in land types Ba tolepis oblongifolia–Englerophytum, Burkea and Ib. The soil form is mainly Mispah with africana–Combretum molle and Brachylae- a clay content of 10–20 % also indicating na rotundata–Burkea africana communities shallow soils on rock. from the Fort Klapperkop Area (Bre- denkamp 1997b). Vegetation Two sub-communities were recognised: This sub-community is characterised by Species group I (Table 1). Characteristic species associated with this plant communi- 2.1 Combretum molle – Burkea africana ty are the trees Pittosporum viridiflorum, Open to Closed Woodland Community Croton gratissimus, Osyris lanceolata and Habitat Pouzolzia mixta and the shrubs Ancylobotrys This sub-community is predominantly found capensis and Rhus magalismontana and the on shallow to moderately steep northern to sbrublet Waltheria indica. Other species north-eastern slopes of ridges and hills in the include forbs like the succulent Crassula Pretoria area. It was mainly recorded in 1b setulosa, Vernonia sutherlandii, Cyperus sp. Land Type. and Sutera caerulea and the grasses Aristida transvaalensis and Enneapogon scoparius. Vegetation Species that dominate the plant community Species group H (Table 1) is diagnostic for are the trees Combretum molle, Vangueria this sub-community. Diagnostic species infausta, Canthium gilfillanii and Diospyros include the trees Burkea africana and lycioides the grasses Cymbopogon validus, Strychnos pungens and the dwarf shrubs Melinis repens and the forb Commelina Rhynchosia nitens and Helichrysum kraussii africana. and geoxylic suffrutescent Dichapetalum cymosum. The average number of species recorded in this plant community is 36 per 200m². The most prominent species in this plant community are the trees Combretum molle Floristically the Bequartiodendron magalis- and Vangueria infuasta, the shrubs Xerophy- montanum shrub land of Ellery (1994) also ta retinervis, the succulent Aloe greatheadii compares well with this community.

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Discussion References ACOCKS, J.P.H. 1988. Veld types of South Africa, 3rd The results of this study indicate that patch- ed. Memoirs of the Botanical Survey of South es of well-preserved vegetation do occur in Africa 57: 1–146. urban Gauteng. The sites chosen were rela- ARNOLD, T.H. & B.C. DE WET. 1993. Plants of Southern Africa. Names and distribution. Mem- tively undisturbed and many could be impor- oirs of the Botanical Survey of South Africa 62: tant to conserve. Some sites are presently 1–825. utilised for agricultural purposes. In spite of BEHR, C.M. & G.J. BREDENKAMP. 1988. A phytosoci- this, weedy species, eg., Tagetes minuta and ological classification of the vegetation of the Witwatersrand National Botanical Garden. Bidens pilosa occur on a large number of South African Journal of Botany 54: 525–533. plots indicating disturbances of the herba- BEZUIDENHOUT, H. 1993. Syntaxonomy and synecol- ceous layer. ogy of western Transvaal grasslands, South Africa. Ph.D. thesis. University of Pretoria, Pre- Species group J (Table 1) indicates a floristic toria. relationship between the Acacia BEZUIDENHOUT, H., G.J. BREDENKAMP & J.H. ELSEN- caffra–Themeda triandra–Hyparrhenia BROEK. 1988. Die plantegroei van die alka- ligraniet en aangrensende kwartsiet in die Vre- hirta Open to Closed Woodland and the defortkoepel noordwes van Parys. Suid Combretum molle–Setaria lindenbergiana Afrikaanse Tydskrif vir Natuurwetenskap en Open to Closed Woodland. Both these com- Tegnologie 7: 4–9. BREDENKAMP, G.J. 1991. Die plantegroei van die munities occur on slopes of fairly high alti- Rietfontein Natuureservaat. Unpublished report, tude. Sandton Municipality. BREDENKAMP, G.J. 1992. The vegetation of the Lone- The classification procedures followed, hill Nature Reserve, Sandton. Unpublished resulted in clearly defined vegetation units report, Sandton Municipality. that can be related to the environmental fac- BREDENKAMP, G.J. 1997a. A vegetation assessment of tors observed. This classification contributes a proposed residential development on the Wil- lows 340 JR Portion 234. Pretoria: Van Riet & to the limited knowledge that presently Louw Landscape Architects. exists for the vegetation of urban open BREDENKAMP, G.J. 1997b. A vegetation assessment spaces in Gauteng. The results of this study of the Fort Klapperkop area. Pretoria: Van Riet can be used as a baseline study and future & Louw Landscape Architects. BREDENKAMP, G.J.& L.R. BROWN. 1998a. A vegeta- studies can be measured against it. The tion assessment of open spaces of the Western species richness determined per 200 m² per Metropolitan Local Council area. Report for the vegetation type could also be used to deter- Western Metropolitan Local Council. mine environmental and ecological degrada- BREDENKAMP, G.J. & L.R. BROWN. 1998b. A vegetation assessment of the northern areas of the tion and actions could be taken to manage Northern Metropolitan Local Council. Report these changes. for the Northern Metropolitan Local Council. BREDENKAMP, G.J. & G.K. THERON. 1978. A sineco- The results of this study could further be logical account of the Suikerbosrand Nature used to determine how the surrounding land- Reserve. I: The phytosiciology of the Witwater- uses have influenced the vegetation of urban srant geological system. Bothalia 12: 513–529. BREDENKAMP, G.J. & G.K. THERON. 1980. A syneco- open spaces. The results could assist in logical account of the Suikerbosrand Nature guiding development in future open spaces Reserve 11: The phytosociology of the Venters- in a constantly expanding urban environ- dorp Geological System. Bothalia 13(192): ment. 199–216. BREDENKAMP, G.J. & N. VA N ROOYEN. 1996a. Mixed bushveld. P. 26. In: LOW, A.B. & A.G. REBELO. (eds). Vegetation of South Africa, Lesotho and Acknowledgements Swaziland. Pretoria: Dept. of Environmental Affairs and Tourism. The research was funded by the Gauteng Department BREDENKAMP, G.J. & N. VA N ROOYEN. 1996b. Moist of Agriculture, Conservation and Environment. Cool Highveld Grassland. P. 43. In: LOW, A.B. &

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