Vegetation Ecology of Sekhukhuneland, South Africa: Kirkia Wilmsii-Terminalia Prunioides Closed Mountain Bushveld

Vegetation ecology of Sekhukhuneland, South Africa: Kirkia wilmsii–Terminalia prunioides Closed Mountain Bushveld

SJ Siebert1,2*, AE van Wyk1 and GJ Bredenkamp1

1 Department of Botany, University of Pretoria, Pretoria 0002, South Africa 2 Present address: SABONET, c/o National Botanical Institute, Private Bag X101, Pretoria 0001, South Africa * Corresponding author, e-mail: [email protected]

Received 2 April 2002, accepted in revised form 16 September 2002

A hierarchical classification, description, and ecological sub-associations. Many new syntaxa are described and and floristic interpretations are presented on one of the ecologically interpreted. For each of the plant commu- six major vegetation types of the Sekhukhuneland nities the floristic richness, endemism and conservation Centre of Plant Endemism, namely the Kirkia status was determined. A selected set of environmental wilmsii–Terminalia prunioides Closed Mountain factors is provided to aid with the delimitation of plant Bushveld. Relevés were compiled in 103 stratified ran- communities. The floristic information, proposed classi- dom plots. A TWINSPAN classification, refined by fication, general description and vegetation key, can be Braun-Blanquet procedures, revealed 20 plant commu- used for the identification of conservation areas, land- nities, which are divided into five associations and 20 use planning and further research.

Introduction

Plant communities of the Kirkia wilmsii–Terminalia prunioides Combretum hereroense–Grewia vernicosa Open Mountain Closed Mountain Bushveld [CMB] (Siebert et al. 2002) are Bushveld. This was a marginal division, with both savanna described in this contribution and form part of a comprehen- vegetation types sharing the majority of their species and sive vegetation and floristic survey of the Sekhukhuneland occurring in the same terrain types on mountain/hill slopes Centre of Plant Endemism [SCPE]. This paper characteris- and in valleys of the central region of the SCPE. The division es and interprets the vegetation units and the associated of the two vegetation types is based on the significant occur- habitats of the CMB, and provides an assessment of the rence of preferential species, which are listed in Table 1 plant diversity, endemism and threatened taxa of the various together with significant non-preferential ones. plant communities. A vegetation key is presented to assist The methodology for the analyses of vegetation data and with the easy identification of the syntaxa of the CMB in the refinement of the classification follows Siebert et al. (2002b). region. Habitat data are provided to aid with future, more Floristic and habitat data of the CMB was obtained from 103 comprehensive ecological analysis. The background and stratified random sample plots. A multivariate approximation objectives of the research are provided elsewhere (Siebert (TWINSPAN) (Hill 1979) of the vegetation, based on the et al. 2002b). floristic data set, was used to distinguish several vegetation types. Braun-Blanquet procedures were used to further Study Area refine the resultant classification in the MEGATAB computer programme (Hennekens 1996). The study area comprises the central part of the SCPE (Figure 1); the Sekhukhuneland Centre is defined and dis- Results and Discussion cussed in Siebert et al. (2002a). The study area is discussed in Siebert et al. (2002b). Note that the extent of occurrence An analysis of the Kirkia wilmsii–Terminalia prunioides of the CMB differs slightly from that of the Open Mountain Closed Mountain Bushveld resulted in the identification of Bushveld [OMB]. four major vegetation units and 20 plant communities, which are grouped as five associations and 20 sub-associations Methods (Table 2). These were subsequently hierarchically classified, described and interpreted. Approximately 600 (30%) of the The final TWINSPAN division of the main table (415 relevés) SCPE’s approximately 2 000 known plant taxa were record- of Siebert et al. (2002), separated the Kirkia wilmsii– ed during the survey of the CMB, with only the most con- Terminalia prunioides Closed Mountain Bushveld from the spicuous and dominant taxa presented in Table 2. The dis- 498 Siebert, Van Wyk and Bredenkamp

UNTAINS T MO OR DRAKENSBERG DPO TRY S Olifants River Lebowakgomo Potlake Nature Reserve LIMPOPO

Olifants River Penge

E Lepellane River O

M Spekboom River O Burgersfort

U N

SOUTH AFRICA Limpopo T A

Sekhukhune I Steelpoort

N Mpumalanga S North West Gauteng Jane Furse Free KwaZulu- State Natal Spekboom River Northern Cape Steelpoort River

Eastern Cape E N Western Cape U H K

lpRiverKlip U

K Groblersdal E Lydenburg S

B Roossenekal

H T

STEENKAMPSBERG

Olifants River Steelpoort River

Stoffberg Dullstroom

= Study Area MPUMALANGA 020 200kmkm

Figure 1: Extent of occurrence of the Closed Mountain Bushveld of the Sekhukhuneland Centre of Plant Endemism in Limpopo (Northern Province) and Mpumalanga, South Africa South African Journal of Botany 2002, 68: 497–517 499

Table 1: Preferential species for each of the two Mountain Bushveld types expressed as a percentage of the total number of revelés (n) in each data set

Species OMB (n = 91) CMB (n = 103) Correlation (r) Difference Preferential species for OMB: 0.73* Vitex obovata subsp. wilmsii 73.6% 3.9% 69.7% Tinnea rhodesiana 60.4% 11.7% 48.7% Brachylaena ilicifolia 48.4% 3.9% 44.5% Themeda triandra 76.9% 34.0% 42.9% Euclea crispa 44.0% 2.9% 41.1% Berkheya insignis 34.1% 0% 34.1% Gnidia caffra 34.1% 1.0% 33.1% Diheteropogon amplectens 36.3% 3.9% 32.4% Senecio latifolius 30.8% 0% 30.8% Orthosiphon fruticosus 31.9% 2.9% 29.0% Preferential species for CMB: 0.961** Panicum maximum 26.4% 70.9% 44.5% Dichrostachys cinerea 15.4% 54.4% 39.0% Terminalia prunioides 26.4% 56.3% 29.9% Grewia flava 4.4% 33.0% 28.6% Boscia albitrunca 6.6% 35.0% 28.4% Sarcostemma viminale 4.4% 31.1% 26.7% Rhus engleri 2.2% 28.2% 26.0% Commiphora mollis 3.3% 29.1% 25.8% Euclea divinorum 2.2% 26.2% 24.0% Acacia nigrescens 3.3% 26.2% 22.9% Non-preferential species: 0.813** Corbichonia decumbens 22.0% 22.3% 0.3% Indigofera hilaris 24.2% 22.3% 1.9% Petalidium oblongifolium 23.1% 26.2% 3.1% Jasminum multipartitum 20.9% 17.5% 3.4% Heteropogon contortus 54.9% 48.5% 6.4% Psiadia punctulata 29.7% 36.9% 7.2% Aloe cryptopoda 24.2% 32.0% 7.8% Leucas capensis 20.9% 12.6% 8.3% Raphionacme galpinii 24.2% 15.5% 8.7% Pellaea calomelanos 36.3% 26.2% 10.1%

*Significant positive correlation **Highly significant positive correlation tribution of 41 Sekhukhuneland Centre endemic/near- sum sericeae endemic (Siebert 1998) and Red Data List (Hilton-Taylor 1.6 Enneapogono scoparii–Kirkietum wilmsii karomieto- 1996) taxa among various plant communities is also indicat- sum speciosae ed in Table 2. 1.7 Enneapogono scoparii–Kirkietum wilmsii nuxietosum congestae Classification II.Urochloo mosambicencis–Eucleion divinorum Plant communities of the Kirkia wilmsii–Terminalia 2.Enneapogono cenchroidis–Acacietum leiorachidis prunioides Closed Mountain Bushveld recognised for the 2.1 Enneapogono cenchroidis–Acacietum leiorachidis SCPE are classified as follows (Figure 2): rhigozetosum obovati I. Enneapogono scoparii–Kirkion wilmsii 2.2 Enneapogono cenchroidis–Acacietum leiorachidis 1.Enneapogono scoparii–Kirkietum wilmsii maeruetosum angolensis 1.1 Enneapogono scoparii–Kirkietum wilmsii cleroden- 2.3 Enneapogono cenchroidis–Acacietum leiorachidis dretosum glabri bolusanthetosum speciosae 1.2 Enneapogono scoparii–Kirkietum wilmsii solanetosum 2.4 Enneapogono cenchroidis–Acacietum leiorachidis incani gardenietosum volkensii 1.3 Enneapogono scoparii–Kirkietum wilmsii bridelieto- 3.Fingerhuthio africanae–Boscietum foetidae sum mollis 3.1 Fingerhuthio africanae–Boscietum foetidae elaeoden- 1.4 Enneapogono scoparii–Kirkietum wilmsii lanneetosum dretosum transvaalensis discoloris 3.2 Fingerhuthio africanae–Boscietum foetidae aloetosum 1.5 Enneapogono scoparii–Kirkietum wilmsii munduleto- globuligemmae 500 Siebert, Van Wyk and Bredenkamp Phytosociological table of the Closed Mountain Bushveld of the Sekhukhuneland Centre Plant Endemism of the Closed Mountain 2: Phytosociological table Table South African Journal of Botany 2002, 68: 497–517 501 Table 2 cont. Table 502 Siebert, Van Wyk and Bredenkamp Table 2 cont. Table South African Journal of Botany 2002, 68: 497–517 503 III +.+R.+...... II ...... 1+.....+...... ++..+...... ++++. + ....1+.+...R+..R+...... RRRRRR+ 1 . + +R . . + +R+ + + . . RR ++++. . .A1 ++++. +. +++++++A1++1 . 1+R1+1 . +++R. +. . 11 .....++.....++.+1.1+++.+.+..+..+....++++RR.....R...... +R+.+...... 1.1...+...+.++.....+.+...... ++... I ++++++. + ++++. . . + ...... ++.+...... +.++...... +R...R..+.+...... +R+.+ ...... 1 ...... R...... +.+.+...... R..+R...... R..+1.111+...... +..+.+1.+++.+++.+111 .....R..+.+.+11R+++++++++++..+++.+.R....R...+R..+R.+.R.+.+++R...... +R+...... R.R.+...... 1B.1B+11A.11AA1AA.++...+1+.+..1.+A.1ABB.+.+.1.1.+1.....1...+...... 1...... ++...+...R+..+....+1...... +...R.R+++....R.++R+.R...... R.+...... ++RR..+R.....+...... RR...... ++..++...... R....R.R....+...111.+....+.+A...... +++.+1.+...... +++.+.+...... ++...... R...... ++.+.+.+..+R.+...... R.R+...... R...... +1+..+....+.+R...... R...... R..R++++..R+++...... +.R..+..R+R+...... 1R.R.+.1+.+...... +R+.+R...... R+....++...R1+.R.+...... +.+R.+R...... R++1R++...... +...... R...... +.R++.+..++...... R...... 1++++...... ++R+.R...... RR.R...... ++R+...... +.R...... 1+..A+.RR1R+.+...... RR...... ++R.+...... ++.++...... +...+...... +R.+.+1+..++R...... +...... +.1++...... +..+...... R...... +....R.....+R.+..R.R.++++...... +...+.R...... +...... +.R1R..++.+.+...... R.R...+.+...... +....+....R...... +.R+..+..+.+...... R+R.R+.R1..R...... ++R..R+.+++R.R...... R...R.....+...+RR.+..+.+....+...... R..R.+11+1+...... +....+.+...... +.AA.+...... +...... +R.11...... 1R.1.++++.+.1...... RR..R...... R...... ++R..+R....+R...... R.R...... R...... +.++.+..+++...... +..+...... +...+.....+R...... +...... ++..+1+1+.R1++.+++...... +R..+R+...+.+...... R...... R...... R...... R...... R.....+...... ++++.1....R+...... +..+...... +AR+R.++1+A.1...... 1. 1.123456 71 1. 23412 1. 3 1. 412312 1. 1. 2. 2. 2. 2. 3. 3. 3. 3. 4. 4. 4. 5. 5. Melino nerviglumis–Euphorbietum tirucalli Fingerhuthio africanae–Boscietum foetidae aloetosum globuligemmae Fingerhuthio africanae–Boscietum foetidae sesamothamnetosum lugardii Fingerhuthio africanae–Boscietum foetidae euphorbietosum ingentis ) [$] t s [K;$] g g s ) [$] t f W13239 f f g g g f P4 f t f t f t f f f leiorachis f g g f [#] f f s s g f f g f t g t t f f f f (form: f f t var. s t (form: f f Table 2 cont. Table Indigofera circinnata Ammocharis coranica Erythrina lysistemon Alliance Acacia senegal Grewia flavescens Indigofera hilaris Association Sub-association Species group Q Chaetacanthus costatus Species group U Eragrostis lehmanniana Acacia luederitzii Aloe globuligemma Elephantorrhiza praetermissa Barleria saxatilis Themeda triandra Andropogon schirensis Species group R: Diagnostic species for Barleria prionitis Kleinia longiflora Acacia karroo Eragrostis pseudosclerantha Pearsonia uniflora Dicliptera fruticosa Acacia gerrardii Aloe greatheadii Schmidtia pappophoroides Hibiscus micranthus Melhania rehmannii Cadaba natalensis Species group S Albizia anthelmintica Species group V: Diagnostic species for Holubia saccata Maerua juncea Felicia mossamedensis Cleome hirta Sporobolus nitens Sesamothamnus lugardii Pogonarthria squarrosa Seddera suffruticosa Aristida rhiniochloa Blepharis saxatilis Lepidagathis scabra Dyschoriste fischeri Acacia grandicornuta Species group T: Diagnostic species for Euphorbia ingens Eleusine coracana Ptycholobium contortum Hippocratea longipetiolata Species group W: Diagnostic species for Schkuhria pinnata Senna italica Dicoma tomentosa Melinis nerviglumis Ledebouria marginata Euphorbia tirucalli 504 Siebert, Van Wyk and Bredenkamp # ! ! !" Table 2 cont. Table H ; : J 7 K < 8 8 : South African Journal of Botany 2002, 68: 497–517 505 III +R+...... +R...... +++++1A+++ +++++ ...... ++.+...R+...+.RRR.R+...... R...++.++.+R..+R...+..++.. II ...... +++.+.....+++..+..R.R.R...+.+...... R.... ++++1+.RRR. .RR. .R.R ....RRR+.....R..R+.R...R.R.R...... R ....+.R...... +R...++.+R...... R.R+RR...+.+RR.R...... RRRR +++++R. . . +R +++++. +1 . +. . . +. .R. . ++.R++++++++++. +1+. R+. +. +. . +. . +. R. R. . .R ++++.R ...... R+..+.R.R+..+RR.R.+.+.+...R.....RR.+R+...++...1.+.+...R.+R+++1.++++.++.. +++++R+. +111+++++++R1 . 1 . ++111 . . ++1++++1+111+1++ I Combreto erythrophylli–Acacietum karroo and .+R...+.+...... ++.++.++R+R.+R+.R..R+R ...... R++...... 1+1R .+...... R1+..+..++.+....++..+.R..+.++.+..1++1.+.+.+....+.++.+..+++1.+++....+.++1.R...R..R....R...... ++R...... R.RA1.R ...... +...... R+.1 ...... +R1 ...... R...... +R+ ...... R++ ...... +...... R.+.+.+..+R..R.++..R.++....+R+11...... R..1R+R+.R. .R...+.R+...R+R...... +..R.R1+R...... +...+...R..R+...R..R+++RR+1RR++.+.+.+....R..RR..+1+...... +++R....+..RR...... +....R....+++R...... RR..R.++.+R+++....+R+..RR...R.1...+.+R.R.1+1.....R.+1+1+.R++.+1..RR+++1.+R1.1111+.R+RR+1...... +++.R+.++....+..+.+.+++..R+.++...++.R...+.R..RR.++R.+..R.+.+..+.R+...+++..RR...+R++.+.++.++...... R.+.R.+.RR...++.R.+..RR..+....R+...... 11R1.1R...... A1+++11...... A+1.1+1R ...... +.+.+A1...... +R.+R+.R...+.....+.R.....RR+ ....++...R..+++.+...+++.+.+...+.R..+.....++.1++.+.....R.++....+.+1...+...RR..++.+....R++R...... RR..1+..R+..+R.11....+.R..+A1...R.11...1...R....+.+1R++R+++.R+.++.+R++.+++R1111 ...... R.R+.++.+..+....+.+.++...+1R ...... +..R..RR...+.R+.+.R.+...++++.+R...... +.+R.+RR ...... R...R...... R.RR..RR+....++.+++.+..++.+.+.++...... R.....R++.++...... +...++.....+RR..+..+11111..A.A1.R...... 11+A11+ ...... R...... +..R....+.+R+R+R..1+...... +.....+.+.+.R+ ...... R...... R.+.R+....R1R+1.1++11...... +.R+1AA1A111...... R++1..++.+R.+ .+R..R...... R+1.R.11+.+1...... RR...... R...RR...... R...+...+.RR+R.+R+.+ ...... +..+AA.+ ...... R...... R++++R...... +...... ++.+R+ ...... +...... +++++..R ...... 1+1...... +...... R...... ++++R1++AR+ ...... +R11+...... R.R...... +1R1...... R+.+..R. .R+13B.1A.1A+.11.1111+.+B1A1+1++.A+B1..+.1+.1+...+.1..++.++.+.+.1.+...++1+.++.++.+..+++..+1.+.R.+.+.+...+..+...... +R...R.R.+1.+..++..+R+ . . +++R+. . ++++++.R+. ++. +. + .11+.+.1.13R. .+.A+. .1A.R. . .+. .R.+1. .R.R.R. .AAAA1+1R. .11. . .R.R.R...... RR.+..+.1RR++R....R+...+1+R+.A.+.+.1.++.1...R....+++1..+..+.....R...... R...+..A+++R....RRR..+R...... R.R++R++R+RR1R ...... 1. 1.123456 71 1. 23412++R+1+R+++.R.R++.+.++...1.1..+...... +1+++1111+++1+1++A11+.R+1+R+A+1R+.R11.1++...++...R...+.++...... 1.+.R..R.+.RR.R...+.+..+R..R.+...... ++.1+.++...+..+1...+.R.1.+1.R111.1.11+++..1+.+....++..+..+.+...... +.+.+...R..+..+.+.R+.1+R....R+...R+R+RR+RR+.R++R....+..RR..R.RRR+.R..RR+...R.+++..+R.R..R..RR...... 3 1. 412312 1. 1. 2. 2. 2. 2. 3. 3. 3. 3. 4. 4. 4. 5. 5. 11+++1 .RR. 1 . 1 . . . 1+R++11R1++R+R+A+. ++R+R+.R +A++R. 1++++1+1A.A11B11+A.+11+1111+11+1+1+1++11+1+++.A1A11.R++1R+. 11+++1++++. ++A1R1++R+. . .R. . +. . R.R. +. 1+. 1+. +1 +R+...1..+R.....R...... R.+..R...RRR....A.1+.+...R...++11++...RR+1...... +...... R+.A3.3.+.+...... R...R. Combreto erythrophylli–Acacietum karroo acacietosum galpinii Combreto erythrophylli–Celtion africanae Combreto erythrophylli–Acacietum karroo rhoetosum pyroidis s s t f f s s t lycioides f t g s g s t g g g t t g f t g var. t t g g t f t g s g f s [#] t t f f t f s t t t s [$] t t t f s t Table 2 cont. Table Alliance Aristida canescens Association Sub-association Species group AD Dichrostachys cinerea Eragrostis curvula Kyphocarpa angustifolia Psiadia punctulata Acacia galpinii Tarchonanthus camphoratus Species group AG: Diagnostic species for Morus japonica Grewia flava Spirostachys africana Andropogon eucomus Hyparrhenia filipendula Syzygium cordatum Paspalum dilatatum Species group AH Ehretia rigida Hippobromus pauciflorus Boscia albitrunca Grewia vernicosa Waltheria indica Commiphora glandulosa Sansevieria hyacinthoides Aloe cryptopoda Carissa bispinosa Species group AE: Diagnostic species for Celtis africana Combretum erythrophyllum Pavonia burchellii Melia azedarach Aristida adscensionis Maytenus heterophylla Sporobolus fimbriatus Species group AI Cardiospermum corindum Panicum deustum Ficus sur Acacia karroo Schotia brachypetala Achyranthes aspera Peltophorum africanum Diospyros lycioides Lippia javanica Olea europaea t Species group AF: Diagnostic species for Rhus pyroides Zanthoxylum thorncroftii Cymbopogon validus Species group AJ Panicum maximum Acacia ataxacantha Sida spinosa Barleria obtusa Kirkia wilmsii Aloe castanea Acacia nigrescens Ziziphus mucronata Heteropogon contortus Croton gratissimus Terminalia prunioides 506 Siebert, Van Wyk and Bredenkamp

Kirkia wilmsii–Terminalia prunioides Closed Mountain Bushveld

I. Enneapogono scoparii– II. Urochloo mosambicencis– III. Combreto erythrophylli– Kirkion wilmsii Eucleion divinorum Celtion africanae

1. Enneapogono scoparii– 2. Enneapogono cenchroidis– 4. Melino nerviglumis– 5. Combreto erythrophylli– Kirkietum wilmsii Acacietum leiorachidis Euphorbietum tirucalli Acacietum karroo

3. Fingerhuthio africanae– Boscietum foetidae

Figure 2: Dendrogram depicting the classification of the plant communities belonging to the Closed Mountain Bushveld of the Sekhukhuneland Centre of Plant Endemism

3.3 Fingerhuthio africanae–Boscietum foetidae euphorbi- of this savanna type is the fact that it constitutes a unique etosum ingentis vegetation type that differs substantially from the surround- 3.4 Fingerhuthio africanae–Boscietum foetidae sesamoth- ing bushveld types of southern Africa (Siebert et al. 2002). amnetosum lugardii The five major vegetation units of the CMB are ecologi- 4.Melino nerviglumis–Euphorbietum tirucalli cally interpreted on the basis of the terrain type, namely 4.1 Melino nerviglumis–Euphorbietum tirucalli emilieto- slopes, plains, riverbanks and anthropogenic-altered areas. sum transvaalensis Slopes are defined as the scarps, midslopes and upper foot- 4.2 Melino nerviglumis–Euphorbietum tirucalli vangueri- slopes of mainly undulating hills and mountains. Plains are etosum cyanescentis defined as the low-lying valley bottoms and lower footslopes 4.3 Melino nerviglumis–Euphorbietum tirucalli flaverieto- between hills and mountains. Riverbanks are defined as the sum bidentis high-lying areas adjacent to or in the vicinity of perennial rivers. Anthropogenic-altered areas are defined as old fields, III.Combreto erythrophylli–Celtion africanae heavily grazed savanna, over-harvested woodlands, utilised 5.Combreto erythrophylli–Acacietum karroo mine properties and mine dumps. Within these five major 5.1 Combreto erythrophylli–Acacietum karroo rhoetosum units, plant communities are distinctive and easily distin- pyroidis guishable in the field, causing a distinct distribution pattern 5.2 Combreto erythrophylli–Acacietum karroo acacieto- of habitats and associated vegetation. This is determined by sum galpinii an extremely heterogeneous environment, which relates to soil properties and depth, rockiness, terrain type, aspect, A vegetation key is presented to facilitate plant communi- slope, moisture availability and human activities. A summa- ty identification (Table 3) according to the procedure fol- ry of selected community attributes is supplied in Table 2. lowed in Siebert et al. (2002). I. Enneapogono scoparii–Kirkion wilmsii all. nova hoc Description loco Nomenclatural type: Enneapogono scoparii–Kirkietum wilm- The Kirkia wilmsii–Terminalia prunioides Closed Mountain sii (holotypus), Association 1 described in this paper. Bushveld is predominantly restricted to the warm slopes and The alliance is floristically related to the Kirkia wilmsii valleys of undulating ultramafic hills and mountains of Dolomite Vegetation (Van der Meulen 1979) and the Kirkia Sekhukhuneland. Surface rocks are predominant and abun- wilmsii Mountain Woodland (Brown et al. 1997). dant in various habitats, with average rock size varying Habitat. This alliance is typical of mountain slopes and between 0.1m and 1m (10–70% surface cover) on the scarps in Sekhukhuneland on moderate to steep slopes slopes of hills and between 0.05m and 2m (5–65% surface (5–15°). Soils are shallow and predominantly constitute the cover) in the valleys. Plant communities were described as rocky Glenrosa form. The soil surface is covered by 30–70% part of either broad-leaved mountain woodlands or micro- of rock with an average diameter of 0.3–1.5m. Table 2 sum- phyllous valley thickets/woodlands. An outstanding feature marises selected habitat attributes for the alliance. It differs South African Journal of Botany 2002, 68: 497–517 507 Wetland Vegetation Wetland Rock Outcrop Vegetation Open Mountain Bushveld Open Mountain Cool Moist Grasslands Closed Mountain Bushveld Closed Mountain Arid Northern Bushveld Enneapogono cenchroidis–Acacietum leiorachidis gardenietosum volkensii Enneapogono cenchroidis–Acacietum leiorachidis rhigozetosum obovati Combreto erythrophylli–Acacietum karroo rhoetosum pyroidis Enneapogono scoparii–Kirkietum wilmsii lanneetosum discoloris Enneapogono scoparii–Kirkietum Melino nerviglumis–Euphorbietum tirucalli vanguerietosum cyanescentis Enneapogono scoparii–Kirkietum wilmsii bridelietosum mollis Enneapogono scoparii–Kirkietum Fingerhuthio africanae–Boscietum foetidae sesamothamnetosum lugardii Melino nerviglumis–Euphorbietum tirucalli emilietosum transvaalensis Enneapogono scoparii–Kirkietum wilmsii munduletosum sericeae Enneapogono scoparii–Kirkietum Fingerhuthio africanae–Boscietum foetidae euphorbietosum ingenti Enneapogono scoparii–Kirkietum wilmsii clerodendretosum glabri Enneapogono scoparii–Kirkietum Enneapogono scoparii–Kirkietum wilmsii nuxietosum congestae Enneapogono scoparii–Kirkietum Melino nerviglumis–Euphorbietum tirucalli flaverietosum bidentis Fingerhuthio africanae–Boscietum foetidae aloetosum globuligemmae Enneapogono scoparii–Kirkietum wilmsii karomietosum speciosae Enneapogono scoparii–Kirkietum Fingerhuthio africanae–Boscietum foetidae elaeodendretosumtransvaalensis Enneapogono cenchroidis–Acacietum leiorachidis bolusanthetosum spciosae Combreto erythrophylli–Acacietum karroo acacietosum galpinii wilmsii solanetosum incani Enneapogono scoparii–Kirkietum Enneapogono cenchroidis–Acacietum leiorachidis maeruetosum angolensis Kirkia wilmsii–Terminalia prunioides Kirkia wilmsii–Terminalia 2.4 2.1 10 11 5.1 1.4 4.2 9 15 1.3 16 17 18 3.4 4.1 8 1.5 3.3 4 6 7 1.1 1.7 13 4.3 3.2 2 3 5 14 1.6 3.1 19 Combretum hereroense–Grewia vernicosa 12 2.3 iii. cinerea Acacia tortilis–Dichrostachys v. tridentata Hippobromus pauciflorus–Rhoicissus 1 Go to/syntaxon ii. Fuirena pubescens–Schoenoplectus corymbosus iv. Themeda triandra–Senecio microglossus 5.2 1.2 2.2 ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) Chaetacanthus costatus Chaetacanthus ) & ) Combretum hereroense Sporobolus fimbriatus ) & Albizia anthelmintica & Acacia senegal Kirkia wilmsii Sanseviera hyacinthoides Ehretia rigida & ) & Kirkia wilmsii & Pouzolzia mixta & Barleria saxatilis & Abutilon guineense Sporobolus fimbriatus ) & Eragrostis curvula Schotia brachypetala & Triaspis glaucophylla Triaspis & & ) Ficus sur ) Hippobromus pauciflorus & & & & ) Sclerocarya birrea ) & & ) Acacia excuvialis Croton gratissimus & Heteropogon contortus & ) & Grewia vernicosa ) & Petalidium oblongifolium Petalidium ) & Jasminum multipartitum Acacia nigrescens ) & & Digitaria eriantha Digitaria Sesamothamnus lugardii Acacia tortilis Nuxia congesta Nuxia congesta Karomia speciosa Euphorbia ingens Aloe globuligemma & ) Bridelia mollis Maerua angolensis Geigeria ornativa Flaveria bidentis Bolusanthus speciosus Acacia galpinii Rhus pyroides Grewia monticola Mundulea sericea Panicum maximum Eragrostis lehmanniana Enneapogon scoparius Enneapogon scoparius Elaeodendrum transvaalensis Pappea capensis Ziziphus mucronata Acacia tortilis & Boscia foetida Commiphora mollis Enneapogon cenchroides Combretum erythrophyllum Emilia transvaalensis Aloe castanea Rhigozum obovatum Gardenia volkensii A Bushveld of the Sekhukhuneland Centre Plant Endemism of the Closed Mountain key to the syntaxa b Lithosol ( b Mean tree height >7m ( b Mean rock size 0.4m ( Boscia albitrunca b Pyroxenite ( Lannea discolor Vangueria cyanescens b Slope 3-5° ( Vangueria b Mean tree height >5m ( b Pyroxenite ( Themeda triandra b Mean rock size >400mm ( b Northern aspects ( b Northern aspects b Mean rock cover >45% ( b Mean grass cover >10% ( b Midslopes only ( b Riverbanks ( b Mainly alluvium ( b Mean rock size >750mm ( b Ferrogabbro/alluvium ( b Moderate slopes 1–5° ( b Predominantly open woodlands b Ultramafic rock ( Grewia vernicosa b Mean rock cover <15% ( b Microphyllous thornveld b Large rock size (>2m diameter) b Seasonally waterlogged soils tree cover (mean <5%) b Sparse 17 a Mean rock cover >30% ( 7 a Mean tree height <7m ( 13 a Magnetite ( 16 a Pedosol ( 6 a Mean rock size 1m ( Melinis nerviglumis 12 a Granophyre/ferrogabbro ( 14 a Mean rock size <400mm ( 15 a Slope 5-7° ( 5 a Mean tree height <5m ( 4 ( Clerodendrum glabrum All aspects a 10 a No alluvium ( 2 ( a Midslopes/scarps 3 ( a Plains/footslopes 11 a Mean rock cover <30% ( 19 a Mean grass cover <10% ( 1 slopes 5–12° ( a Steep 9 a Mean rock size <750mm ( 18 a Pyroxenite/alluvium ( Table 3: Table ii. a Broad-leaved savanna iv. a Small rock size (<2m diameter) v. a Predominantly closed woodlands Leads/description i. soils a Well-drained iii. a Dense tree cover (mean >5%) 8 a Shale ( Solanum incanum 508 Siebert, Van Wyk and Bredenkamp from the Urochloo mosambicencis–Eucleion divinorum and ous forbs, but total forb cover is relatively low (5%). Combreto erythrophylli–Celtion africanae (described in this Floristic diversity. This savanna association is common in paper), in that it is characterised by shallow soils, rocky ter- the SCPE and a floristic affinity exists with the other CMB rain and an undulating topography. communities of the Centre in various species groups, espe- Vegetation structure. The vegetation of the alliance repre- cially the transitional Enneapogono cenchroidis–Acacietum sents broad-leaved savanna. Diagnostic species are pre- leiorachidis (Table 2). Conservation priorities and diversity sented in species group A (Table 2) and include drought tol- statistics are the same as for the alliance (Tables 2 and 4). erant trees and shrubs such as Aloe marlothii, Commiphora africana, C. mollis and Sterculia rogersii. Enneapogon sco- 1.1 Enneapogono scoparii–Kirkietum wilmsii clerodendreto- parius is the only diagnostic grass, and is a dominant sum glabri subass. nova hoc loco species in Kirkia wilmsii plant communities. Granite and Nomenclatural type: Relevé 119 (holotypus), Table 2 dolomite hills are characterised by Kirkia wilmsii throughout The vegetation of the sub-association is tall, dense wood- the central bushveld of South Africa (Van der Meulen 1979) land on relatively shallow soils of south facing midslopes and this diagnostic species, in combination with the charac- (Table 2) along the northern escarp of the Schurinksberg. teristic diagnostic grass Enneapogon scoparius, supports This sub-association is associated with exposed shale for- the proposal of this plant community as an alliance of the mations and is not a typical SCPE syntaxon, for the relevés proposed Mountain Bushveld Order (Siebert et al. 2002). form part of the control data set that was sampled on sub- Floristic diversity. Floristic links with the other alliances are strates of a sedimentary origin and not the ultramafic rocks of visible in species groups O, Q, AD and AJ (Table 2). Strong the Rustenburg Layered Suite. Diagnostic species are given floristic links exist with the Urochloo mosambicencis in species group B (Table 2). Clerodendrum glabrum, –Eucleion divinorum. The average number of species Dombeya rotundifolia, Elephantorrhiza goetzei and encountered per sample plot for this alliance is 37, with the Ormocarpum kirkii are the diagnostic woody species of this total number of plant species being a minimum of 222 taxa syntaxon and make up most of the 12% tree and shrub cover. (33 relevés) (Table 2). There are 20 plant taxa of conserva- Diagnostic herbaceous species include Buttonia superba tion value, nine are SCPE endemics and 10 are SCPE near- and Plectranthus xerophilus. Enneapogon scoparius and endemics, with two species listed as Red Data List taxa Panicum maximum are the most prominent grasses, howev- (Table 2). Six taxa of conservation value are restricted to this er, grass cover was sparse as a result of a dry spell. This sub- alliance in the study area (Table 4). association shows a strong floristic link with the other sub- associations in species groups F and O (Table 2), namely the 1. Enneapogono scoparii–Kirkietum wilmsii ass. nova northern slopes of Thaba Sekhukhune and Dwars River hoc loco Pass. Two taxa with conservation status are restricted to the Nomenclatural type: Relevé 191 (holotypus), Table 2 association (Table 4), of which one is a SCPE near-endemic Habitat. The habitat of the association is extremely hetero- and the other the rare SCPE endemic, Rhus batophylla. geneous with no two sample plots exhibiting the same set of environmental factors (Table 2). It is restricted to the mid- 1.2 Enneapogono scoparii–Kirkietum wilmsii solanetosum slopes and scarps of the mountains and hills of the incani subass. nova hoc loco Steelpoort-Burgersfort region. The association is mainly Nomenclatural type: Relevé 116 (holotypus), Table 2 found on relatively steep sloped northern aspects, as the ori- The vegetation of the sub-association is tall, closed wood- entation of hills and mountains in the study area are general- land on north-facing midslopes of the Schurinksberg. It is ly east-west, thus providing ample northern slopes facing into mainly associated with exposed shale formations and is the the Steelpoort River Valley (Table 2). Soil surfaces are rocky. second community of the control data set. The sub-associa- The dominant soil type is the Glenrosa form, defined as an tion is found on relatively steep slopes and rocky surfaces orthic A-horizon over a lithocutanic B-horizon (Table 2). (Table 2). Diagnostic species of the association are present- Vegetation structure. The vegetation representing this ed in species group C (Table 2). Woody species diagnostic association is relatively dense tall, dry woodland. Diagnostic of the association include Commiphora glandulosa and the species are presented in species group A (Table 2). The semi-scandent Rhoicissus tridentata. Tree cover is high association is characterised by small trees/shrubs, namely (11%). Diagnostic herbaceous taxa include the geophyte Acacia exuvialis, Combretum apiculatum, Grewia monticola Boophane disticha and forb Solanum incanum. The diag- and Triaspis glaucophylla. Other dominant woody species nostic grasses are Eustachys paspaloides and Setaria lin- include Acacia nigrescens, A. senegal var. leiorachis, denbergiana, and together with the frequently occurring Dichrostachys cinerea, Kirkia wilmsii and Sclerocarya birrea. Digitaria eriantha, Enneapogon scoparius and Heteropogon The tree cover is 10%, with some trees reaching heights of contortus, they contribute to the highest grass cover record- up to 7m. Due to a low shrub cover (3%), a typical African ed for the CMB (33%). The total vegetation cover of this sub- savanna structure is evident. Enneapogon scoparius, association is the highest for CMB (50%). Four plant taxa of Heteropogon contortus and Panicum maximum are the most conservation value occur in the sub-association, including abundant grasses and contribute substantially to the grass two of the taxa restricted to the association (Table 4). cover of 15%. High grass cover on dry northern aspects is dependent on good rainy seasons and due to semi-arid con- 1.3 Enneapogono scoparii–Kirkietum wilmsii bridelietosum ditions in Sekhukhuneland, annual fires are uncommon. In mollis subass. nova hoc loco addition, many trees and forbs are succulent. Asparagus Nomenclatural type: Relevé 304 (holotypus), Table 2 buchananii and Commelina africana are the most conspicu- This sub-association represents tall (6m), dry woodland South African Journal of Botany 2002, 68: 497–517 509 that forms bush clumps on mountain slopes running into the CMB. The typical African savanna structure allows for a well- Steelpoort River Valley, from Roossenekal in the south to developed and tall grass layer (17% cover; 1m high). Forbs Steelpoort in the north. The habitat is characterised by the are relatively tall for the CMB (average 1.1m) and have a igneous rocks of ferrogabbro and granophyre. These rocks cover of 6%. This plant community is the first sub-associa- are related, but do not form part of the Rustenburg Layered tion of nine that make up the peculiar floristic affinity in Suite, which results in different environmental (edaphic) con- species group Q (Table 2), which cuts across parts of three ditions. It occurs on relatively steep, rocky slopes of north- associations (1.4 to 3.1) and is determined by the presence eastern aspects. Species group D contains the diagnostic of ultramafic rocks. The sub-association has the highest species for the sub-association (Table 2). Prominent species average number of species encountered per sample plot of the sub-association include the trees Combretum apicula- and therefore has the highest species richness per unit area tum, Commiphora africana, Grewia monticola, Kirkia wilmsii in the CMB (Table 2). Of its 10 taxa of conservation value and Pappea capensis, forbs such as Barleria lancifolia and (Table 2), three are taxa restricted to the association (Table 4). Clerodendrum ternatum, and the grass Enneapogon scoparius. Percentage cover for the different growth forms is 1.5 Enneapogono scoparii–Kirkietum wilmsii munduletosum typical for the association. sericeae subass. nova hoc loco Nomenclatural type: Relevé 241 (holotypus), Table 2 1.4 Enneapogono scoparii–Kirkietum wilmsii lanneetosum This sub-association represents short, closed woodland discoloris subass. nova hoc loco interspersed with patches of open shrubland and a well- Nomenclatural type: Relevé 220 (holotypus), Table 2 developed grass layer. The habitat is mostly restricted to This sub-association represent tall woodlands of the northern aspects of large hills of gabbro, norite and peripheral hills running adjacent and between the norite anorthosite, and sometimes on ferrogabbro. It occurs on massive of the SCPE and the shales of the Schurinksberg. steep, rocky midslopes and scarps. Diagnostic species of It is a typical community of the SCPE Mountain Bushveld, for this sub-association are given in species group G (Table 2). it is underlain by pure pyroxenite. It is associated with steep, It is characterised by the presence of the diagnostic shrub, rocky midslopes on northern aspects (Table 2). Diagnostic Mundulea sericea, and various associated diagnostic forbs. species are presented in species group E (Table 2). Lannea Dominant grasses are Heteropogon contortus, Panicum discolor is the only diagnostic tree and Cymbopogon excava- maximum and Themeda triandra. Prominent woody taxa tus the only diagnostic grass. The sub-association is dominat- include the shrubs Elephantorrhiza praetermissa, Grewia ed by large trees/shrubs (14% cover) of which Commiphora vernicosa and Jasminum multipartitum. A notable floristic africana, Combretum apiculatum, Elephantorrhiza praeter- link exists with the Enneapogono scoparii–Kirkietum wilmsii missa, Grewia monticola, Kirkia wilmsii, Pappea capensis, lanneetosum discoloris in species group H (Table 2). Three Sterculia rogersii and Ziziphus mucronata are the most fre- of the SCPE plant taxa of conservation value that are quent. Trees of this sub-association reach average heights restricted to the association were recorded for this sub-asso- of 6.5m and constitute some of the tallest woodlands of the ciation (Table 4).

Table 4: Rare and endangered species restricted to specific plant communities of the Sekhukhuneland Centre of Plant Endemism

Species Family Plant communities 1.1 1.2 1.4 1.5 1.6 1.7 2.1 2.2 2.4 3.2 3.3 3.4 4.1 4.2 5.1 5.2 Acacia sp. (P4) FABA...... $$..... Albuca sp. (S856) LILI ...... $.... Bauhinia tomentosa [form] (S444) FABA...... $$...... Combretum petrophilum COMB ...... R#.. Cyphia transvaalensis LOBE .....#...... Euphorbia sp. (W13194) EUPH ...... $.... Gnidia caffra [form] (W12975) TILI ...... $...... Gymnosporia sp. (S458) CELA ...... $$ Hibiscus barnardii MALV...... R$R$.. Jatropha latifolia var. latifolia EUPH . . ####...... Ledebouria dolomiticola LAMI ...... $...... Mosdenia leptostachys POAC ...... K.. Orthosiphon tubiformis LAMI ...... #.. Pachypodium saundersii APOC ...... N.... Plectranthus venterii LAMI ...... $.. Plectranthus xerophilus LAMI # # ...... Premna mooiensis [form] (W13004) VERB ...... $$.. Rhus batophylla ANAC R$ ...... Stylochaeton sp. (S1332) ARAC . . $$$$...... Xerophyta retinervis [form] (W13208) VELL . $$$$......

$ = endemic; # = near-endemic; R = Rare; K = Insufficiently Known; N = threatened elsewhere S = Siebert; W = Van Wyk 510 Siebert, Van Wyk and Bredenkamp

1.6 Enneapogono scoparii–Kirkietum wilmsii karomietosum described in this paper), in that it is characterised by deep speciosae subass. nova hoc loco sandy or clay soils, rocky terrain and a level topography. Nomenclatural type: Relevé 191 (holotypus), Table 2 Vegetation structure. The vegetation of the alliance is pre- This sub-association covers large parts of the SCPE and dominantly microphyllous thornveld. Diagnostic species are was well sampled during the survey (10 relevés). It repre- presented in species group AC (Table 2) and include sents tall (6m), closed (14%) woodlands of hill slopes in the drought tolerant trees and shrubs of brackish soils, namely Steelpoort River Valley where it is found on moderate to Acacia nilotica, A. tortilis, Boscia foetida, Combretum steep rocky midslopes and scarps of norite, pyroxenite and hereroense, Euclea divinorum, Grewia bicolor, Rhus engleri anorthosite hills. It occurs on lithosols of the Mispah and and Ximenia americana. Three succulent forbs and three Glenrosa forms (Table 2). Diagnostic species are represent- grass species that are usually associated with calcareous ed by species group I (Table 2). The diagnostic woody or brackish soils are diagnostic for the alliance. Petalidium species are Karomia speciosa, Ochna inermis and Pavetta oblongifolium, a non-succulent forb of calcareous areas, is inandensis, and Eragrostis rigidior is the diagnostic grass. also diagnostic. Kirkia wilmsii, Grewia vernicosa and Conspicuous woody species include Acacia nigrescens, A. Terminalia prunioides are dominant tree species of the senegal var. leiorachis, Combretum apiculatum, Commiphora alliance, and in combination with the characteristic grass mollis, Kirkia wilmsii and Terminalia prunioides. Dominant species for the SCPE Mountain Bushveld, Heteropogon grasses include Heteropogon contortus, Panicum maximum contortus and Panicum maximum, the baseline floristic and Themeda triandra. Of the ten taxa of conservation value composition supports the proposal of this plant community recorded for this sub-association, three are restricted to the as an alliance of the proposed Mountain Bushveld Order association (Table 4). (Siebert et al. 2002). Floristic diversity. Floristic links with the other alliances are 1.7 Enneapogono scoparii–Kirkietum wilmsii nuxietosum visible in species groups O, Q, AD and AH (Table 2). Strong congestae subass. nova hoc loco floristic links exist with the Enneapogono scoparii–Kirkion Nomenclatural type: Relevé 197 (holotypus), Table 2 wilmsii. The mean number of species encountered per sam- This vegetation type is tall, closed woodland with patches ple plot for this alliance is 37, with the total number of plant of grassland. The sub-association can be found on moder- species being a minimum of 197 taxa (62 relevés) (Table 2). ately sloped scarps of exposed norite, pyroxenite and There are 35 plant taxa of conservation value, 18 are SCPE anorthosite hills in the Steelpoort and Dwars River Valleys. endemics and 15 are SCPE near-endemics, with six species The sub-association occurs on Mispah soils, namely an orth- listed as Red Data List taxa (Table 2). Twenty-one taxa of ic A-horizon over solid rock (Table 2). The habitat is charac- conservation value are restricted to this alliance in the study terised by rock cover of up to 70% and rocks more than 1m area (Tables 2 and 4). Restricted taxa not listed in Table 4 in diameter. Although the community was undersampled, are Brachylaena ilicifolia (form), Catha transvaalensis, diagnostic species for this sub-association were easily Dicliptera fruticosa, Euclea linearis (form), Kleinia longiflora obtained and are listed in species group J (Table 2). (form), Kleinia stapeliiformis, Leucas capensis (form) and Diagnostic woody species comprise the shrubs Nuxia con- Orthosiphon fruticosus. gesta and Pouzolzia mixta. Diagnostic semi-woody taxa include Hibiscus calyphyllus, Ruttya ovata and Tetradenia 2. Enneapogono cenchroidis–Acacietum leiorachidis brevispicata. Hermannia floribunda is the only diagnostic ass. nova hoc loco forb. Andropogon schirensis, Enneapogon scoparius and Nomenclatural type: Relevé 155 (holotypus), Table 2 Themeda triandra dominate the sparse grass layer (7% The association is definitely related to the lower ranks of grass cover). Nine plant taxa with conservation value are part the Acacia tortilis–Carissa bispinosa Woodland of Van der of the sub-association, and include a SCPE near-endemic Meulen (1979). However, it is a unique system restricted to which is restricted to it (Table 4). Two Red Data List taxa the Steelpoort-Burgersfort region of the eastern Rustenburg assessed as Insufficiently Known were recorded (Table 2). Layered Suite. Habitat. This association occurs on deep soils of upper II. Urochloo mosambicencis–Eucleion divinorum footslopes of mountains and hills in the Steelpoort River Nomenclatural type: Fingerhuthio africanae–Boscietum Valley. It is associated with most geological substrates of the foetidae (holotypus), Association 3 described in this paper. valley. It occurs on all aspects of hills and mountains. The The alliance is floristically related to the Colophospermum habitat is sloped gently (3–5°), levelling out towards the mopane–Euclea divinorum Tree Savanna (Van Rooyen et Steelpoort River. Soils are diverse and dependent on the al. 1981) and the Acacia tortilis–Carissa bispinosa mother material. Typical soils include red sand or loam of the Woodland (Van der Meulen 1979). Bonheim, Hutton and Shortlands forms. Rock size ranges Habitat. This alliance is typical of footslopes and valleys in from 0.2–1m in diameter and covers 10–50% of the soil sur- Sekhukhuneland, on level to moderate slopes (1–5°). Soils face (Table 2). are deep and predominantly constitute the Hutton (red Vegetation structure. The association is not characterised apedale B), Bonheim (pedocutanic B) and Shortlands (red by diagnostic taxa. Preferential species are presented in structured B) soil forms. The soil surface is covered by species group O (Table 2). No species are shared exclu- 20–60% of rock with an average diameter of 0.2–1.0m. sively between any of the sub-associations of the associa- Table 2 summarises selected habitat attributes for the tion. Dominant taxa of this typical woodland (mean height of alliance. It differs from the Enneapogono scoparii–Kirkion 4.5m) include the trees/shrubs Acacia nigrescens, A. sene- wilmsii and Combreto erythrophylli–Celtion africanae (both gal var. leiorachis, A. tortilis, Dichrostachys cinerea, Kirkia South African Journal of Botany 2002, 68: 497–517 511 wilmsii, Sclerocarya birrea and Terminalia prunioides. rocky, with rocks reaching large mean diameters of up to 1m Shrubs are tall (2m) and sparse (4%), which allows sufficient (Table 2). Diagnostic species are presented in species group resources for the grass layer to develop. Abundant, charac- L (Table 2). Diagnostic herbaceous taxa include species teristic grasses include Andropogon schirensis, Aristida such as Ledebouria dolomiticola and Orthosiphon fruticosus canescens, Enneapogon cenchroides, Eragrostis curvula that are also found on dolomites. Maerua angolensis, is the and Themeda triandra. The grass cover is 16%, which only diagnostic tree species and Enteropogon makes this the association with the best-developed grass macrostachys, the only diagnostic grass. Other dominant layer in the CMB. Conspicuous and frequent occurring forbs taxa include small trees/shrubs such as Acacia senegal var. are Asparagus buchananii, Barleria saxatilis, Commelina leiorachis, Dichrostachys cinerea, Grewia bicolor and africana and Indigofera lydenburgensis. Terminalia prunioides. Grass cover is 11% and dominated Floristic diversity. This association is floristically related to, by Aristida canescens, Enneapogon cenchroides and and forms the ecotone on the footslopes between, associa- Themeda triandra. Barleria saxatilis, Kyphocarpha angusti- tions 1 and 3 in species groups O, Q and AH (Table 2). Of folia and Sanseviera hyacinthoides are the most dominant the high number of 21 plant taxa of conservation value forbs. In species group AH (Table 2), this sub-association is recorded for this association (Table 2), 11 are SCPE the first syntaxon of a series (2.2 to 3.3) that shows an affin- endemics (the highests number recorded for any of the ity with association 5 of riverbanks. The sub-association also associations in this paper) and ten are SCPE near- shows a slight relationship with the Enteropogono endemics, of which one is a Red Data List taxon. Three plant macrostachyo–Sclerocaryetum birrea asparagetosum taxa are restricted to the association (Table 4). The total sekukuniensis of ferrogabbro slopes of the Leolo Mountains number of species recorded for the association is 178 (23 (Siebert et al. 2002b). There are 13 taxa of conservation relevés) and the average number of plant species recorded value recorded for the sub-association, of which seven are per relevé is 35 (Table 2). SCPE endemics (in both cases the second highest numbers recorded for the CMB) (Table 2). One endemic is a Red Data 2.1 Enneapogono cenchroidis–Acacietum leiorachidis List taxon and one near-endemic is restricted to the sub- rhigozetosum obovati subass. nova hoc loco association (Table 4). Nomenclatural type: Relevé 155 (holotypus), Table 2 This woodland has a well-developed shrub layer and 2.3 Enneapogono cenchroidis–Acacietum leiorachidis bolu- occurs frequently on midslopes and footslopes of ultramafic santhetosum speciosae subass. nova hoc loco hills. It occurs on any aspect on red loam soils of predomi- Nomenclatural type: Relevé 299 (holotypus), Table 2 nantly the Bonheim form (melanic A-horizon and underlain by In the SCPE this sub-association represents tall, closed a pedocutanic B). The soil surface is not particularly rocky woodland on red sandy-loam soils. The habitat is found along (Table 2). Diagnostic species are presented in species group mountain footslopes with a granophyre base. It occurs on all K (Table 2). The community is characterised by the diagnos- aspects. Rock cover percentage is sparse and rock size is rel- tic grasses Cenchrus ciliaris and Sporobolus stapfianus. An atively small (100–150mm diameter) (Table 2). Species group interesting combination of diagnostic woody species occurs M (Table 2) contains the diagnostic species for this sub-asso- for the sub-association and includes Bauhinia tomentosa ciation, with herbaceous taxa such as the grass Diheteropogon (form), Croton menyhartii, Rhigozum obovatum and Tinnea amplectens, and numerous low growing forbs (0.45m). rhodesiana. The shrubs of this sub-association are the tallest Bolusanthus speciosus is the only diagnostic tree. Prominent in the CMB (2.5m). Monechma divaricatum is the diagnostic taxa include the grasses Enneapogon cenchroides, forb. Dominant tree species are Acacia senegal var. leio- Heteropogon contortus and Themeda triandra. The sub-asso- rachis, Boscia albitrunca and Terminalia prunioides. ciation is dominated by grasses (30% cover), with very few Enneapogon cenchroides, Eragrostis curvula and prominent herbs (3% cover). Dominant trees include Acacia Heteropogon contortus are the most dominant grasses. senegal var. leiorachis, Combretum hereroense, Conspicuous taxa of a relatively well-developed forb layer Dichrostachys cinerea, Euclea divinorum and Grewia verni- (6% cover) include Asparagus laricinus, Barleria saxatilis, cosa. Total vegetation cover for this sub-association is 44%, Indigofera hilaris, Petalidium oblongifolium and Psiadia punc- the second most vegetated plant community of the CMB. The tulata. The sub-association shows a slight relationship with sub-association has a relationship with the Loudetio simpli- the Enteropogono macrostachyos–Sclerocaryetum birreae cis–Eucleetum linearis of alluvium soils on a norite/pyroxenite rhigozetosum obovati of norite/pyroxenite foothills of the Leolo base (Siebert et al. 2002b). Nine taxa with conservation value Mountains (Siebert et al. 2002b). Of the 12 recorded plant occur in this sub-association (Table 2), which include seven taxa of conservation value, one is a Red Data List taxon and SCPE near-endemics (the second highest number recorded one is a taxon restricted to the association (Tables 2 and 4). for the CMB). One Red Data List taxon was also recorded.

2.2 Enneapogono cenchroidis–Acacietum leiorachidis 2.4 Enneapogono cenchroidis–Acacietum leiorachidis gar- maeruetosum angolensis subass. nova hoc loco denietosum volkensii subass. nova hoc loco Nomenclatural type: Relevé 212 (holotypus), Table 2 Nomenclatural type: Relevé 117 (holotypus), Table 2 This sub-association represents tall (5m), closed wood- In the SCPE this sub-association is tall, closed woodland lands on the footslopes of pyroxenite and ferrogabbro hills. with a well-developed shrub layer (6% cover). The habitat is It usually occurs on red loam soils of the Hutton (orthic A- characterised by alternative bands of deep (>300mm) or horizon on a red apedale B) and Shortlands (orthic A-hori- shallow (<300mm) soils (sometimes associated with cal- zon on a red structured B) forms. The habitat is relatively crete or magnetite outcrops) of the Glenrosa or Shortlands 512 Siebert, Van Wyk and Bredenkamp forms. Species group N contains the diagnostic species for pyroxenite and/or derived alluvium. It occurs on level foot- this sub-association, which are characterised by the tree slopes of hills and mountains, predominantly on westerly Mystroxylon aethiopicum and shrub Gardenia volkensii aspects. It prefers red loam soils of the Bonheim, Hutton and (Table 2). Diagnostic herbaceous taxa comprise four forbs. Shortlands forms. The soil surface is sparsely covered with Other prominent species of the sub-association include the small rocks (Table 2). Diagnostic species are presented in small trees/shrubs Acacia tortilis, Dichrostachys cinerea and species group P (Table 2). The community is characterised Terminalia prunioides. The succulent Aloe castanea is a fre- by diagnostic forbs and a diagnostic grass, Eragrostis quently occurring and conspicuous species. Prominent capensis. Catha transvaalensis and Elaeodendron trans- grasses include Enneapogon cenchroides, Panicum maxi- vaalensis are the diagnostic tree species. Tree cover is 11% mum and Sporobolus ioclados. One taxon with conservation and includes dominant woody species such as Albizia value is restricted to the sub-association (Table 4). anthelmintica, Acacia tortilis, Croton gratissimus, Euclea divinorum, Rhus engleri and Terminalia prunioides. Aristida 3. Fingerhuthio africanae–Boscietum foetidae ass. nova adscensionis, A. canescens, Eragrostis curvula, hoc loco Fingerhuthia africana, Panicum maximum and Themeda Nomenclatural type: Relevé 143 (holotypus), Table 2 triandra are the most important conspicuous grasses of a The association is definitely related to the Acacia sparse grass layer (10%). The association has a strong link erubescens Woodland on Ferrogabbro of the western with associations 1 and 2 in species group Q (ultramafic Rustenburg Layered Suite (Van der Meulen 1979). However, dominated mother material) and is the last of the crosscut- Acacia erubescens is not as common in the vegetation of ting floristic affinity (Table 2). It can be seen as an ecotone the eastern Rustenburg Layered Suite. between footslope and valley vegetation. This sub-associa- Habitat. This is an association of dry and warm areas of tion is related to the Eragrostio lehmannianae–ippobrome- gently sloping footslopes and broad valleys. The mother tum pauciflori rhoetosum batophyllae of erosion gulleys in material can be ferrogabbro, norite and pyroxenite covered the Steelpoort River Valley (Siebert et al. 2002b). Of the 12 by alluvium. Subsequently, relatively deep soils of the taxa of conservation value recorded for the sub-association, Bonheim, Hutton, Shortlands and Valsrivier forms are domi- eight were SCPE near-endemics, the highest number nant, but are interspersed with Glenrosa lithosols (Table 2). recorded for the CMB. Rock cover on the surface is sparse, and rocks have a small size (mean diameter of 250mm) (Table 2). 3.2 Fingerhuthio africanae–Boscietum foetidae aloetosum Vegetation structure. Preferential species for these tall globuligemmae subass. nova hoc loco woodlands are presented in species group AC (Table 2). Nomenclatural type: Relevé 143 (holotypus), Table 2 Prominent herbaceous taxa include succulent forbs, namely The sub-association is low, dense woodland, with a well- Aloe burgersfortensis, Kalanchoe paniculata and developed forb layer (11% cover). It is associated with deep Sarcostemma viminale. Forb cover is high (7%) and nearly (>1m) soils in valleys, especially the northern areas of the of the same level as the grass cover (10%) and is probably Steelpoort River Valley. Aspect is usually east or west due to as a result of heavy grazing. Tree and shrub cover is 13% and the general southwest-northeast flow of the river. Soils are the association is dominated by Acacia erubescens, A. tortilis, characteristically a red loam with a pedocutanic B-horizon, A. nilotica, Boscia albitrunca, B. foetida, Dichrostachys such as the Bonheim (melanic A-horizon) and Valsrivier cinerea and Euclea divinorum. Common grasses of the (orthic A-horizon) forms. Rock cover is sparse (Table 2). association are Aristida adscensionis, A. canescens, Diagnostic species of the sub-association are presented in Eragrostis curvula, Fingerhuthia africana, Sporobolus fim- species group R (Table 2). Acacia luederitzii, Cadaba aphyl- briatus and Panicum maximum. Total vegetation cover is the la and Cadaba natalensis are the diagnostic woody species lowest for the CMB (30% cover) probably due to overgraz- of the sub-association. Eragrostis pseudosclerantha is the ing and it is suggested that its favourable terrain type is diagnostic grass. The vegetation type is characterised by responsible for its extensive utilisation. three forbs and the succulent Aloe globuligemma. Important Floristic diversity. This association cannot stand alone and trees/shrubs are the same as that for the association, but has various strong links with associations 1 and 2 in species also includes Acacia gerrardii and A. grandicornuta and group Q (ultramafic substrates), associations 2 and 4 in Terminalia prunioides. Prominent herbaceous taxa of its species group AC (brackish/calcareous soils), associations well-developed forb layer include the succulents Aloe burg- 1, 2 and 4 in species group AD (Mixed Bushveld compo- ersfortensis, Kleinia longiflora and Sanseviera nents), and associations 2 and 5 in species group AH (thick- hyacinthoides, and the non-succulent Petalidium oblongifoli- et forming species) (Table 2). Altogether 20 plant taxa of um. Abundant grasses of this sparse layer are Eragrostis conservation value occur in this association and include two curvula, E. lehmanniana, Fingerhuthia africana, Sporobolus Red Data List taxa (Table 2). Four taxa of conservation value fimbriatus and S. nitens. The sub-association shows a are restricted to the association (Table 4). The average num- strong floristic relationship with both sub-associations 3.1 ber of species encountered per sample plot is 36, with a total and 3.3 in species groups S and U respectively (Table 2). number of 197 plant taxa (25 relevés) (Table 2). The sub-association has a high mean number of plant species per sample plot (43) and the highest total number of 3.1 Fingerhuthio africanae–Boscietum foetidae elaeoden- plant species per sub-association of the CMB (131 taxa for dretosum transvaalensis subass. nova hoc loco 8 relevés) (Table 2). One of the restricted taxa of conserva- Nomenclatural type: Relevé 229 (holotypus), Table 2 tion value, Acacia karroo (form), is restricted to sub-associ- This sub-association is tall (5m), closed woodland on ations 3.2 and 3.3 (Table 4). South African Journal of Botany 2002, 68: 497–517 513

3.3 Fingerhuthio africanae–Boscietum foetidae euphorbieto- Red Data List taxa were recorded, namely Asparagus sum ingentis subass. nova hoc loco clareae (Insufficiently Known) and Pachypodium saundersii Nomenclatural type: Relevé 306 (holotypus), Table 2 (Insufficiently Known for Swaziland). This vegetation type is tall (5.5m), closed woodland of predominantly dry northern, but also east and west aspects 4. Melino nerviglumis–Euphorbietum tirucalli ass. nova of mountain footslopes and valleys. The community is found hoc loco from Roossenekal to Steelpoort and is restricted to ferro- Nomenclatural type: Relevé 411 (holotypus), Table 2 gabbro footslopes and alluvium in valleys. The soils are of Habitat. This is an association of short, dense shrubland the Bonheim, Valsrivier and Glenrosa forms. Rock cover is on alluvium, norite and anorthosite. It is restricted to over- relatively low (Table 2). Diagnostic species are presented in grazed and over-harvested areas of gentle to moderately species group T (Table 2). Only one grass species, Eleusine sloped footslopes and valleys between Burgersfort and coracana, is diagnostic for the sub-association. There are Mecklenburg. Soils are of the Glenrosa, Mispah and three diagnostic forbs. Erythrina lysistemon and Euphorbia Steendal (melanic A-horizon over a soft carbonate B) forms, ingens are the diagnostic trees. Prominent trees of the sub- which are interspersed with black turf. Approximately 45% of association are Acacia tortilis, Boscia foetida and Ehretia the soil surface is covered by rocks with a relatively large rigida. Conspicuous herbaceous taxa include the succulent diameter up to 2m (Table 2). Aloe greatheadii and the geophyte Urginea epigea. The Vegetation structure. Diagnostic species are presented in grasses Fingerhuthia africana, Panicum maximum, species group W (Table 2). The vegetation unit is dominated Sporobolus fimbriatus and S. ioclados are abundant and by diagnostic forbs (8% cover), and includes Dicoma tomen- contribute substantially towards the high grass cover of tosa, Ledebouria marginata, Senna italica, and the natu- 17%. This sub-association also exhibits the typical African ralised alien, Schkuhria pinnata. Diagnostic woody species savanna structure with tall, but distributed trees, with a well- are the scandent shrub Hippocratea longipetiolata and the developed grass layer. The association has a strong link succulent shrub Euphorbia tirucalli. The shrub cover is 8%, with sub-association 3.2 in species group U (iron-rich soils) the highest for CMB, and includes prominent taxa such as and is the last community of the crosscutting floristic affinity Aloe castanea, Diospyros lycioides subsp. lycioides, Grewia with association 5 in species group AH (Table 2). bicolor and G. vernicosa. Although disturbed, the total vegetation cover is the highest for an association in the CMB (34%). 3.4 Fingerhuthio africanae–Boscietum foetidae sesamoth- As a consequence of the continuous grazing and harvesting amnetosum lugardii subass. nova hoc loco of the system, the grass layer is dominated by species such Nomenclatural type: Relevé 311 (holotypus), Table 2 as Chloris virgata, Eragrostis viscosa and especially Aristida The sub-association is related to the Sesamothamnus adscensionis, Melinis nerviglumis and Heteropogon contor- lugardii-Catophractes alexandri Low Open Woodland tus. Naturalised alien succulent trees such as Cereus peru- described for an area north of the Soutpansberg (Visser et vianus and Opuntia ficus-indica occur frequently. al. 1996). Floristic diversity. A strong floristic affinity exists with the This sub-association represents sparse woodland of other associations of the Urochloo mosambicencis–Eucleion undulating norite landscapes on mostly sandy Hutton soils divinorum in species groups AG and AL (Table 2). However, interspersed with calcareous Glenrosa soils in the the intense harvesting of firewood in this vegetation type is Burgersfort region. Slope of the habitat is gentle and rock evident in species groups X to AB, where the absence of cover and diameter is the highest for the association (Table woody species is distinct. This association has 18 plant taxa 2). The diagnostic species for the sub-association are pre- with conservation value. Of these, a high number of four plant sented in species group V (Table 2). The diagnostic species species are Red Data List taxa (Table 2). It also has a taxon include the woody shrub Maerua juncea and the succulent with a biogeographically noteworthy distribution and rarity in small tree, Sesamothamnus lugardii. Aristida rhiniochloa nature, Eulophia leachii. Six plant taxa with a conservation and Pogonarthria squarrosa are the diagnostic grasses. value are restricted to the association (Tables 2 and 4); Prominent species of the sparse tree/shrub layer (6%) together with association 1 the most for the CMB. The aver- include Boscia albitrunca, Cadaba termitaria, Grewia bicolor age number of species encountered per sample plot is 40, and G. vernicosa. Dominant herbaceous taxa of the sub- which is the highest average recorded for any of the associ- association are Indigofera heterotricha, Justicia protracta ations of the CMB. The total number of plant species record- and Kyphocarpha angustifolia, and the succulent Aloe burg- ed is a minimum of 187 taxa (14 relevés) (Table 2). ersfortensis. The sparse grass layer (6%) is characterised by Aristida canescens, Fingerhuthia africana, Panicum max- 4.1 Melino nerviglumis–Euphorbietum tirucalli emilietosum imum and Urochloa mosambicensis. Future research can transvaalensis subass. nova hoc loco probably upgrade this plant community to the level of asso- Nomenclatural type: Relevé 395 (holotypus), Table 2 ciation. It does not show any specific relationships with other The habitat is a scattered shrubland on moderately sloped sub-associations. Of the community’s seven taxa of conser- footslopes of heavily grazed hills to the east of the Leolo vation value, three are restricted to it (Table 4). Several taxa Mountains. It is found predominantly on shallow Mispah soils are of biogeographic significance due to their disjunct distri- overlying anorthosite and norite. Rock cover is average, but bution, namely Polygala krumanina (Karoo disjunct) and the relative size is large (Table 2). Diagnostic species are three Limpopo River Valley disjuncts: the small succulent presented in species group X (Table 2). The diagnostic trees Sesamothamnus lugardii and Commiphora tenuipetio- herbaceous species include indigenous forbs and natu- lata, and the herbaceous climber Decorsea schlechteri. Two ralised alien weeds. Two grasses are diagnostic, namely 514 Siebert, Van Wyk and Bredenkamp

Brachiaria brizantha and Schizachyrium sanguineum. Shrub this sub-association are presented in species group AA cover is higher than that of the trees and Grewia vernicosa (Table 2) and includes the alien species Agave sisalana, is the most abundant woody species. Prominent forbs Flaveria bidentis and Xanthium strumarium. Combretum include Geigeria ornativa, Schkuhria pinnata and Waltheria imberbe is a large diagnostic tree. Large stands of the diag- indica (9% cover; 0.4m high) (Table 2). Aristida adscension- nostic grasses Bothriochloa insculpta and Ischaemum fasci- is, Eragrostis viscosa, Melinis nerviglumis and especially culatum occur (17% cover). Prominent trees include large Heteropogon contortus, are the most abundant grasses specimens of Acacia karroo, Boscia foetida, Schotia brachy- (12% cover; 0.5m high). A specific link exists with sub-asso- petala and Ziziphus mucronata, which are interspersed with ciation 4.2 in species group Z (Table 2). The mean number the weedy shrubs Gossypium herbaceum (indigenous) and of plant species encountered per sample plot in this associ- Senna didymobotrya (alien). Conspicuous forbs not listed in ation is 45; together with sub-association 1.4 the highest Table 2 include Commicarpus plumbagineus, Corchorus tri- average for the CMB. One taxon of conservation value in the dens, Dyschoriste rogersii and Sida cordifolia. Aristida sub-association is an endemic Red Data List taxon, Hibiscus adscensionis, Brachiaria eruciformis, Cynodon dactylon, barnardii (Table 2). Two taxa of conservation value restrict- Eragrostis cilianensis and Urochloa oligotricha are the most ed to the association are recorded for this sub-association abundant grasses. A strong floristic relationship exists with (Table 4). association 5 in species group AI (Table 2), possibly indicat- ing that it is an altered form of the Combretum erythrophyl- 4.2 Melino nerviglumis–Euphorbietum tirucalli vanguerieto- lum–Celtis africana Forest (Van der Meulen 1979) on alluvi- sum cyanescentis subass. nova hoc loco um near rivers. Nomenclatural type: Relevé 411 (holotypus), Table 2 This is low, closed shrubland of footslopes usually associ- III. Combreto erythrophylli–Celtion africanae ated with small kloofs. It lies on gentle slopes. The geologi- Nomenclatural type: Combreto erythrophylli–Acacietum kar- cal substrate is ultramafic and soils are predominantly of the roo (holotypus), Association 5 described in this paper. Glenrosa form. A large proportion of the soil surface is cov- The alliance is floristically related to the Combretum ery- ered by large rocks (Table 2). Diagnostic species are pre- throphyllum–Celtis africana Forest Alliance (Van der Meulen sented in species group Y (Table 2). Obetia tenax (small 1979). tree) and Vangueria cyanescens (shrub) are diagnostic for Habitat. This alliance is typical of well-treed riverbanks in this community. Four diagnostic forbs occur and the diag- Sekhukhuneland. It is associated with level to moderate nostic grass Aristida transvaalensis. Shrub cover percent- sloped (1–5°) deep alluvium soils of the Oakleaf form (orthic age is the highest for the CMB (11%), with forb cover out- A-horizon over a neocutanic B). The soil surface is covered competing grass cover by 1%. Tree cover is low and mean by 5–40% of rock with a mean diameter of 0.5–3m. Table 2 tree height is only 3m. Unique taxa recorded for the sub- summarises selected habitat attributes for the alliance. It dif- association are the grasses Mosdenia leptostachys and fers from the Enneapogono scoparii–Kirkion wilmsii and Urochloa panicoides, the forbs Leucas martinicensis and Urochloo mosambicencis–Eucleion divinorum (both Thunbergia neglecta and the shrubs Combretum described in this paper), in that it is characterised by deep petrophilum and Tecomaria capensis. This sub-association loam soils, tall woodlands (>6m) and proximity to rivers. shares plant species with sub-associations 4.1 and 4.3 in Vegetation structure. The vegetation of the alliance is pre- species groups Z and AB respectively (Table 2) and might dominantly gallery forest. Diagnostic species are presented represent an intermediate stage between footslopes and in species group AE (Table 2) and include trees and shrubs plains of the association. The total number of plant species of moist soils, namely Celtis africana, Combretum erythro- recorded for the sub-association is 130 taxa, the highest for phyllum, Ficus sur, Lippia javanica, Melia azedarach and a community in the CMB (Table 2). Strangely, this disturbed Olea europaea. Pavonia burchellii, a forb of shady areas, is sub-association also has the highest number of plant taxa also diagnostic. Acacia karroo, Kirkia wilmsii, Peltophorum with conservation value in this particular CMB vegetation africanum, Schotia brachypetala and Ziziphus mucronata type. These 15 taxa include nine SCPE endemics (the high- are common tree species of the alliance, and as character- est number for the CMB) (Table 2). There are three Red Data istic species for the SCPE Mountain Bushveld provide the List taxa recorded and four species of conservation value are baseline floristic composition to support the proposal of this resticted to the sub-association only (Tables 2 and 4). plant community as an alliance of the proposed Mountain Bushveld Order (Siebert et al. 2002). 4.3 Melino nerviglumis–Euphorbietum tirucalli flaverietosum Floristic diversity. Limited floristic links with the other bidentis subass. nova hoc loco alliances are visible in species groups AH and AI (Table 2), Nomenclatural type: Relevé 386 (holotypus), Table 2 which indicates that it is intermediate between the vegeta- In the SCPE this sub-association represents areas for tion of CMB and that of rocky outcrops. The mean number grazing between fields, characterised by single large trees of species encountered per sample plot for this alliance is (>10m) that are remnants of former closed woodlands of the 30, with the total number of plant species being a minimum floodplain. It is common on all aspects of footslopes and val- of 115 taxa (8 relevés) (Table 2). There are two plant taxa of leys. Mean rock diameter is below average for the study conservation value, one a SCPE endemic and one a SCPE area and covers a low percentage of the soil surface (Table near-endemic, with one taxon of conservation value restrict- 2). Soil types are characterised by black clays and turfs, pre- ed to this alliance in the study area (Tables 2 and 4). dominantly the Steendal form. The diagnostic species for South African Journal of Botany 2002, 68: 497–517 515

5. Combreto erythrophylli–Acacietum karroo ass. nova the communities discussed in this paper. It occurs on a gen- hoc loco tle slope and is predominantly encountered on deep alluviam Nomenclatural type: Relevé 184 (holotypus), Table 2 soils. Rock cover is average with a relatively small mean This association is related to the Acacio diameter (Table 2). Diagnostic species are presented in ataxacanthae–Celtidetum africanae of Dolomite Outcrops species group AG (Table 2). Diagnostic grasses are common (Matthews et al. 1992), Combretum erythrophyllum–Acacia and include Andropogon eucomis, Hyparrhenia filipendula karroo Gallery Forest (Van der Meulen 1979) and Diospyros and the alien, Paspalum dilatatum. Trees of the sub-associa- whyteana–Celtis africana Forest (Coetzee 1975). tion grow tall (mean of 7.5m) and include the diagnostic Habitat. This association occurs on riverbanks along larg- species Acacia galpinii, Spirostachys africana, Syzygium cor- er rivers such as the Steelpoort and Olifants and includes an datum and the alien, Morus japonica. Tree/shrub cover is alien plant species component. It is a vegetation unit on pre- 20% and dominates the community. A typical forest structure dominantly red loam Oakleaf soils. The slope is more or less is evident with frequently occurring canopy trees such as level (1–5°), a characteristic of these broad, alluvium filled Celtis africana, Combretum erythrophyllum, Ficus sur and valleys. Rock cover percentage is relatively low and varies Olea europea subsp. africana. Forb cover is low and includes from 5–40%, and average rock diameter is 50–300mm the conspicuous species Acalypha villicaulis, Achyranthes (Table 2). aspera, Kleinia fulgens and Pavonia burchellii. Vegetation structure. Diagnostic species for the tall, closed woodlands of this association is given in species group AE Conservation (Table 2). Diagnostic species are the same as for the alliance. Tree and shrub cover is the highest for CMB (19% Throughout the SCPE the remaining populations of plants cover and mean height of 7m). Abundant woody species and animals are under considerable pressure from exploita- include Acacia karroo, Diospyros lycioides subsp. lycioides, tive land uses (Siebert et al. 2002a). Conservation of many Flueggea virosa and Hippobromus pauciflorus. Prominent localities of the same plant community (ecosystems) could forbs include Achyranthes aspera, Cardiospermum corindum be the most effective approach for the protection and sur- and Hypoestes aristata and the climber Secamone filiformis vival of endemics of fractal landscapes such as ultramafic (3% forb cover). Prominent grasses in the association, typi- substrates (Witkowski and Liston 1997, With and King 1998, cal of shady and/or moist areas, are Panicum deustum, P. Harrison 1999). Certain SCPE plant endemics and threat- maximum and Sporobolus fimbriatus. ened taxa of the CMB are restricted to specific plant com- Floristic diversity. A floristic link exists with associations 2 munities. In the light of rapid development of the region, and 3 in species group AH, possibly ascribed to thicket-form- these vegetation units or areas need immediate attention ing situations, and a link with association 4 in species group and should be considered for conservation purposes. AI, possibly because sub-association 4.3 is floodplain vege- Important communities of conservation value, which are tation (Table 2). Conservation priorities and diversity statis- restricted to the SCPE, are in associations 1 to 4 (more tics are the same as the alliance (Tables 2 and 4). specifically sub-associations 1.4, 1.6, 2.1, 2.2, 3.1, 3.2 and 4.2). Special attention should be given to the conservation of 5.1 Combreto erythrophylli–Acacietum karroo rhoetosum associations 2 and 3, as ecotones contain the maximum pyroidis subass. nova hoc loco amount of adaptive variation of a species (Smith et al. 2001). Nomenclatural type: Relevé 177 (holotypus), Table 2 Sub-associations 3.4, 4.1 and 5.2 should also be considered This vegetation type is closed, scattered woodland along for they harbour very unique plant communities. If protected, the Steelpoort River. The habitat is predominantly broad, threatened communities should be monitored by conserva- slightly sloped banks underlain by deep alluvial soils. Soil tion biologists, as alien plant invasions in rare habitats and surface rock cover is low for the CMB, with a small diameter distinctive plant communities pose a significant challenge (Table 2). Species group AF (Table 2) represents the diag- (Chiarucci and De Dominicis 1995, Stohlgren et al. 1999). nostic species, with the woody species Acacia ataxacantha, Furthermore, some species in plant communities of con- Rhus pyroides, Tarchonanthus camphoratus and servation value, show disjunct distributions with other Zanthoxylum thorncroftii diagnostic for the sub-association. regions in South Africa. A floristic link exists with the Tree/shrub cover is high (18%), and subsequently forb cover Northern Cape and North West Province (arid part of is only 2%. Grass cover (10%) is surprisingly high, but Savanna Biome), with species shared including Acacia eri- occurs on the woodland edges, and includes the diagnostic oloba, Gnidia polycephala, Jamesbrittenia atropurpurea, grass Cymbopogon validus. Barleria obtusa and Sida spin- Nuxia gracilis, Polygala krumanina, Pterothrix spinescens, osa are the diagnostic forbs. Mean tree height is 6.5m which Rhigozum obovatum and Stipagrostis hirtugluma subsp. provides a forest-like structure with a canopy. Very few patula. Another floristic link, with the Lowveld, probably species with conservation value was recorded. developed when species reached Sekhukhuneland via the Olifants River Valley and include taxa such as Balanites 5.2 Combreto erythrophylli–Acacietum karroo acacietosum maughamii, Diospyros mespiliformis, Lonchocarpus capas- galpinii subass.nova hoc loco sa and Ptaeroxylon obliquum. In addition, many other floris- Nomenclatural type: Relevé 184 (holotypus), Table 2 tic links exist with other areas in South Africa, for instance, The vegetation is tall, closed woodland on the banks of Schotia latifolia and Asparagus intricatus with the Eastern rivers in the SCPE. Hence, the vegetation unit is restricted to Cape, and Sesamothamnus lugardii and Commiphora valleys. The community is usually encountered as meander- tenuipetiolata with the areas north of the Soutpansberg. It is, ing vegetation (gallery woodland) on riverbanks amidst any of therefore, clear that although the SCPE falls predominantly 516 Siebert, Van Wyk and Bredenkamp in Mixed Bushveld (Van Rooyen and Bredenkamp 1996), its types in the region. However, floristically it is related to the vegetation is extremely diverse and contains floristic ele- Kirkia wilmsii Dolomite Vegetation Types (Van der Meulen ments from various other regions in South Africa. 1979) and the Kirkia wilmsii Mountain Woodland (Brown et Several rare, but widespread, species were recorded dur- al. 1997). ing the vegetation survey, but were not listed in the phytoso- • Urochloo mosambicencis–Eucleion divinorum is floristical- ciological table due to their rarity in habitat (recorded in one ly related to the Colophospermum mopane–Euclea divino- relevé of a species group). These taxa are the endemics rum Tree Savanna (Van Rooyen et al. 1981) and the Cyphostemma sp. (Siebert 1383), Leucas capensis (form: Acacia tortilis–Carissa bispinosa Woodland (Van der Van Wyk 13007), Phyllanthus sp. (Siebert 470), Rhoicissus Meulen 1979). These links indicate that soils can induce sekhukhuniensis, and the near endemics Asparagus clareae similar vegetation types across the borders of two different (Insufficiently Known Red Data List taxon), Brachylaena ilici- vegetation classes. folia (form: Siebert 613), Euclea linearis (form: Siebert 937), • Enneapogono cenchroidis–Acacietum leiorachidis con- Kleinia stapeliiformis and Vitex obovata subsp. wilmsii. tains associations that represent a transition between savannas of mountains/hills (Enneapogono scoparii– Discussion Kirkion wilmsii) and savannas of plains/valleys (Fingerhuthio africanae–Boscietum foetidae). This indi- Ultramafic areas should not always be seen as open grass- cates the presence of clear-cut, classifiable ecotones on land areas (Wild 1965), as woodlands are common on these footslopes of mountains/hills. soils (Jaffrè 1980). Guy (1975) and Chiarucci (1994) have • Combreto erythrophylli–Celtion africanae is floristically reported on woody communities that grow almost exclusive- related to the Combretum erythrophyllum–Celtis africana ly in sites with special pedo-morphological characters and Forest Alliance proposed by Van der Meulen (1979). The do not show the extremely stunted woody species and occurrence of this alliance along riverbanks throughout grassland dominated communities typical of ultramafic sub- the central savannas of South Africa was first recognised strates. On a local scale, the CMB is characterised by rela- 25 years ago and was never described formally. tively dense woodlands, which is quite distinctive from the • Anthropogenic plant communities are common in former OMB’s typical stunted, sparse structure and low diversity of homelands (Smits et al. 1999) and therefore human pres- small trees/shrubs (Siebert et al. 2002b). The structure of sure cannot be ignored as a factor that influences the dis- CMB is similar to that of Mixed Bushveld (Van Rooyen and tribution of Melino nerviglumis–Euphorbietum tirucalli veg- Bredenkamp 1996). etation in the SCPE. Disturbed communities infested by It is speculated that an extremely heterogeneous set of alien species are usually ignored during surveys and not large-scale environmental factors determines the plant com- documented properly. munities within the CMB. A combination of many factors such as terrain type (slope or aspect), soil depth (lithosols or Concluding remarks alluvium), soil moisture (riverbanks or open plains), soil type (sand or clay) or anthropogenically altered areas (fields or The classification obtained from TWINSPAN and refined by over-grazed/harvested areas), affects the species composi- Braun-Blanquet procedures resulted in 20 vegetation units tion of these plant communities. Future work should focus (plant communities) and associated habitat conditions. on the extensive habitat data available for the SCPE to These vegetation units should be considered as ecological- determine which dynamic environmental gradients con- ly interpretable communities for the area concerned. Seven tribute significantly towards the vegetation patterns of the plant communities have been identified as of high conserva- CMB, because grass-tree coexistence in savannas is driven tion priority. by the limited opportunities for tree saplings to escape both It is hoped that the descriptions of the different vegetation drought and the flame zone into the adult stage (Thrash units will make a significant contribution towards the under- 1998, Higgins et al. 2000), and hence is influenced by a standing of the associations between plant communities and complex network of local and large-scaled factors, notably ultramafic substrates in the SCPE and southern Africa as a water availability, herbivory, fire, soil texture, nutrients and whole. Such an understanding is important as it contributes anthropogenic interference (Cole 1986, Skarpe 1992, towards proper land-use management and will ensure the Breshears et al. 1998, Briske and Henderson 1998, Jeltsch protection of the rare ecosystems of an ultramafic region et al. 1998, Lock 1998, Bjornstad et al. 1999, Higgins et al. that contains the largest known economically viable 1999). resources of platinum, chromium and vanadium on earth Vegetation patterns of the savanna of the SCPE should be (Viljoen and Schurmann 1998). seen as similar, but not synonymous, to the Mixed Bushveld The floristic and environmental data supplied in this paper defined by Van Rooyen and Bredenkamp (1996). Siebert et can be meaningfully applied in management and conserva- al. (2002) defined a unique type of Mountain Bushveld on tion of these semi-arid, but valuable rangelands in the the ultramafics of Sekhukhuneland, which is a useful contri- SCPE. The manner in which natural resources are used and bution towards the work that remains to be done on the clas- managed will have a direct relation to its future productive sification of the central savannas of South Africa. Interesting capacity (Aucamp et al. 1992). Proper and sound future observations were made during the classification process: assessment of the region’s vegetation should include • Enneapogono scoparii–Kirkion wilmsii is poorly studied in aspects such as species rarity, habitat preference and veg- the northern provinces of South Africa. It proved extreme- etation dynamics. These aspects are important as they con- ly difficult to link this alliance to any other major vegetation tribute to accurate identification and selection of conserva- South African Journal of Botany 2002, 68: 497–517 517 tion areas to protect rare and threatened species within a Jaffre T (1980) Etude Ecologique du Peuplement Végétal des Sols Centre of Endemism with a vast economic potential. 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