The phytosociology of the Villiers – Grootvlei area, South Africa. 3. The plant communities of the Ib Land Type

S.AfrJ.Bot., 1993, 59(2): 227 - 234

227

The phytosociology of the Villiers - Grootvlei area, South Africa. 3. The plant communities of the Ib Land Type P.J.J Breytenbach,*t W.J. Myburgh,t G.K. Theron and G.J. Bredenkamp Department of Botany, University of Pretoria, Pretoria, 0002 Republic of South Africa tpresent address: Roodeplaat Grassland Institute, Private Bag XOS, Lynn East, 0039 Republic of South Africa Received 15 May 1992; revised 24 November 1992

The vegetation of the Ib Land Type in the Vil/iers - Grootvlei area was classified by means of the BraunBlanquet method. A total of 41 releves in this land type were used. Six main plant communities were identified, with one of the communities divided into two sub-communities. The plant communities were related to specific environmental conditions that were confirmed by the ordination (DECORANA) of the data. Die plantegroei van die Ib-Iandtipe in die Vil/iers - Grootvlei omgewing is deur middel van die Braun-Blanquet metode geklassifiseer. 'n Totaal van 41 rei eves is in die landtipe uitgeplaas. Ses hoofplantgemeenskappe is onderskei, waarvan een verder in twee sub-gemeenskappe verdeel is. Die plantgemeenskappe is gekoppel aan spesifieke omgewingstoestande wat deur 'n ordening (DECORANA) bevestig is. Keywords:

Braun-Blanquet, classification, ordination, plant communities.

"To whom correspondence should be addressed.

Introduction The recovery, sound utilization and conservation of the veld as a natural resource ought to receive careful attention, not just from a research point of view, but also in terms of agricultural extension (Department of Agriculture and Water Affairs 1986). The White Paper on Agricultural Policy refers to the decline of the natural pasturage and warns that indiscriminate land-use practices and the over-exploitation of the natural resources may lead to a decrease in the living standards of the human population. The veld type description of Acocks (1988) is the only classification that is available for this part of the Highveld region. This classification is of a rather generalized nature (1: 1 5()() ()()() scale) and therefore a more detailed mapping of the Highveld Region according to the association of vegetation with distinct environmental conditions (especially soil-climate combinations), is a necessity (Department of Agriculture and Water Affairs 1986). The aim of the study was to describe and classify the vegetation of the Grootvlei district, southern Transvaal, and to study the vegetation and its interactions with the environment (Edwards 1972, 1979). This specific study area was chosen by the Department of Agriculture and Development as a key area, the results of which could be extrapolated to the surrounding areas. It is also situated between western and eastern Transvaal grasslands, thus providing an ideal study area to link phytosociological information from eastern parts (Turner 1989) and western parts (Bezuidenhout 1988; Bredenkamp et al. 1989. The classification of the Bb Land Type (Breytenbach et al. 1992) and the Ba Land Type (Breytenbach et al. 1993) were presented separately, and in this report, we present a classification and description of the plant communities of the Ib Land Type.

(Republic) 1978] . The study area is situated between latitudes 26°45'S and 27°()()'S and between longitudes 28°30'E and 28°45'E. It occupies an area of approximately 7()() km 2 (70 000 ha) in the vicinity of Grootvlei, southern Transvaal, and a small area adjacent to Villiers in the northern Orange Free State (Figure 1). A detailed description of the physical environment of the study area was given by Breytenbach et al. (1992).

Methods In the study the Ziirich-Montpellier phytosociological approach (Braun-Blanquet 1932; Werger 1974) was used to define and describe the different plant communities, as it is

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Figure 1 The location of the study area, based on the 2628 DC GRoafVLEI 1:50000 topocadastral map [South Africa (Republic) Pretoria 1978] .

228

the most popular and acceptable approach in use in South Africa (Bredenkamp 1975; Van Rooyen 1978). The Rangeland Ecology Section of the Roodeplaat Grassland Institute advocates the Ztirich-Montpellier approach, and the fact that other studies in the Grassland Biome (Bredenkamp 1975; DealI 1985; Bezuidenhout 1988; Turner 1989; Bloem 1988; Kooij 1990) were done with this approach contributed to its selection. The vegetation was sampled with the use of stratified random sample points (releves). Experiments during the reconnaissance phase of the study area showed that more infotmation was obtained with the sub-quadrat method, in terms of time and energy spent, than with a single-square quadrat. A stratified random method was used for the placement of sub-quadrats. The sub-quadrats were rectangular with the sides in the proportion of one to two, since this was more effective than square quadrats (Oosting 1956; Cain & Castro 1959). The sub-quadrats that were used were 3 m in length and 1.5 m in width (Turner 1989). Sub-quadrats were placed until there was a less than 10% increase in new species. A minimum of three sub-quadrats per releve was maintained (a minimum area of 13.5 m2) (Turner 1989). The releves were placed by using random co-ordinates generated by computer. The crown cover of the vegetation of the Bankenveld (Veld Type 61) (Acocks 1988), and the basal cover of the vegetation of the other veld types of Acocks (1988) were measured using a cover meter (Westfall & Panagos 1984). Myburgh et al. (1992) studied the vegetation of the Bankenveld in the Grootvlei area and his data were incorporated in this study. The PHYTOTAB computer program (Westfall et al. 1982) was used to process the floristic data set and to produce phytosociological tables. The taxa names used in this study are in accordance with Breytenbach (1991) and Gibbs Russell et al. (1985, 1987).

Results and Discussion The area of the Ib Land Type represents 9 800 ha (Figure 2). The dominant soils of the Ib Land Type are of the Avalon, Hutton, ShortIands and Bonheim forms (MacVicar et al. 1977). The predominant rock types of the Ib Land Type are Ventersdorp lava, breccia and tuff (Department of Mineral and Energy Affairs 1986). The dominant terrain units of the area are terrain unit 3 (40% of the area) within the slope class 12 - 50%, terrain unit 1 (30% of the area) within the slope class 0 - 12% and terrain unit 4 (20% of the area) within the slope class 6 - 12% (Land Type Survey Staff 1984). The long-term average annual rainfall of the Ib Land Type is 689.2 mm (Land Type Survey Staff 1984). The size of the Ib Land Type determined the number of releves (41) compiled in stratified random sample plots. Classification The vegetation of the Ib Land Type can be divided into three main vegetation types, namely, a high-lying grassland (11 % of the area), a high-lying shrubland (54% of the area) and a lower-lying grassland (35% of the area) (Figures 3 and 4). The high-lying grassland, characterized by species group A (Table 1), occurs on shallow (50 mm) rocky soils, and the lower grassland, characterized by species groups K and L (Table 1), on deep (975 mm) clayey soils. The two

S.-Afr.Tydskr.Plantk., 1993.59(2)

.

Bakenkop

Barnardskop

I N

l1li" c,"' " .. Skm

Figure 2 The location of the Ib Land Type in the study area (Land Type Survey Staff 1984).

grassland communities are characterized by the absence of shrubs and trees. The high-lying shrubland, characterized by species group I (Table 1), occurs on shallow soils and has a high above-ground rock cover (60%) on steep slopes (25,. Species group N (Table 1) depicts the general species of this land type and on average 30 species per releve were recorded. The vegetation of the Ib Land Type was grouped into six communities and two sub-communities, namely (Figure 3; Table 1): 1.1 The Loudetia simp/ex - Eragrostis curvu/a Grassland 1.2 The Euclea crispa - Aloe davyana Shrubland 1.3 The Diospyros lycioides - Heteromorpha trijoliata Shrubland 1.4 The Diospyros lycioides - Leonotis microphylla Shrubland 1.5 The Diospyros lycioides - Trachypogon spicatus Shrubland 1.6 The Eragrostis plana - Eragrostis curvula Grassland 1.6.1 The Eragrostis plana - Cynodon dactylon Grassland 1.6.2 The Eragrostis plana - Jndigofera species Grassland.

1.1 The Loudetia simplex - Eragrostiscurvula Grassland The Loudetia simp/ex - Eragrostis curvu/a Grassland is situated mainly on soils of the Mispah Form (MacVicar et al. 1977) with a clay content of 15 - 25% and an average soil depth of 50 mm (Figure 3). The parent material is undifferentiated Witwatersrand quartzite and shale with sandstone (Department of Mineral and Energy Affairs 1986). The community is situated at an altitude of 1580 1640 m above sea-level on slopes with an inclination of 1 3° on terrain unit 3 (Figures 3 and 4). The above-ground rock cover in the community varies between 16 and 30% (Figure 3). On average, 23 species per sample plot were recorded.

S.Afr.I.Bot.,1993,59(2)

The community is characterized by the diagnostic grass species Loudetia simplex, Diheteropogon filifolius and Harpochloa falx, the semi-woody forbes Euryops transvaalensis and Solanum panduriforme, the succulent Khadia acutipetala and the forb Gazania krebsiana (species group A, Table 1). Dominant grasses are Aristida junciformis (species group C, Table 1), Aristida congesta, Tristachya leucothrix, Eragrostis curvula, E. racemosa, Brachiaria serrata, Heteropogon contortus, Themeda triandra and Elionurus muticus (species group N, Table 1). The pioneer grasses Aristida junciformis, A. congesta. Cynodon dactylon and the dwarf shrub Stoebe vulgaris are prominent on disturbed and trampled areas. The abundance of Loudetia simplex, the dominant grass in the community, causes this vegetation to be less palatable for grazing animals. Diheteropogon filifolius, Khadia acutipetala and Euryops transvaalensis are characteristic species of the rocky hills of the Ib Land Type. No shrubs or trees occur in the community. The mean crown cover of the herbaceous layer was 55%.

1.2 The Euclea crispa - Aloe davyana Shrubland The Euclea crispa - Aloe davyana Shrubland is situated mainly on shallow «300 mm) rocky soils of the Mispah Form (Mac Vicar et al. 1977) with dolerite as the parent material (Figure 3) (Department of Mineral and Energy Affairs 1986). Basaltic lava, agglomerate and tuff also occur in the community (Department of Mineral and Energy Affairs 1986). The community is situated at an altitude of 1620 - 1660 m above sea-level mainly on north-facing slopes with an inclination of 11 - 20° on terrain unit 3 (Figures 3 and 4). The above-ground rock cover in the plant community varied between 31 and 60% (Figure 3). On average, 33 species per sample plot were recorded. The community is characterized by species group B (Table 1). The diagnostic species include the succulent Aloe davyana, the geophytes Hypoxis argentea, H. obtusa and Ledebouria ovatifolia, the scandent creepers Ipomoea obscura and Rhynchosia totta, the geoxylophyte Elephantorrhiza elephantina and the forbes Barleria obtusa and Pavonia transvaalensis. Aristida junciformis (species group C, Table 1) is a mutual species of the Loudetia simplex Eragrostis curvula Grassland and the Euclea crispa - Aloe davyana Shrubland. The species of species groups E, I, M and N (Table 1) occur generally in the community. The dominant grasses are Aristida junciformis, Eragrostis curvula, Heteropogon contortus, Elionurus muticus, Themeda triandra and Brachiaria serrata. Dominant shrubs are Euclea crispa, Diospyros lycioides and Rhus rigida . Canthium gilfillanii, Ehretia rigida, May tenus heterophylla and Diospyros whyteana are the dominant trees. Aristida june iformis is present where trampling and overgrazing have occurred. The mean crown cover for the community was 44%.

229

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1.3 The Diospyros lycioides - H eteromorpha trifoliata Shrubland The Diospyros lycioides - Heteromorpha trifoliata Shrubland occurs on shallow «300 mm) soils of the Mispah Form (MacVicar et al. 1977) with basaltic lava, agglomerate, tuff and diabase as the parent material (Figure 3) (Department of

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230

S.-Afr.Tydskr.Plantk.,1993,59(2)

Mineral and Energy Affairs 1986). The community is situated at an altitude of 1640 - 1760 m above sea-level on slopes with an inclination of 1 - 25° on terrain units 1 and 3 (Figures 3 and 4). The above-ground rock cover in the plant

community varies between 16 and 60% (Figure 3). On average, 33 species per sample plot were recorded. The community is characterized by the diagnostic woody tree species Heteromorpha trifoliata and Zanthoxylum

1.3

COMMUNITIES

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Figure 4 The location of the communities in the Ib Land Type on terrain units (see text for community names).

Table 1 Phytosociological table of the Ib Land Type in the Villiers - Grootvlei area, South Africa COMMUNITY NUMBER

1.1

1.2

1.3

1.'1

1.6

1.5

1. 6.1

RELEVE NUMBER

1. 6 . 2

2201 2222 2222222202 222 22222 00000202100 0011 1122 2225 432331439'1 1,,4 114211 72775 1171139 3401 76'14 7680 8805635911 994 32358 75567744736 4316

SPECIES GROUP A Loudetia simplex Euryops tr,7nsvaalensis Solanum panduriformo Oihetoropogon ri I irol ius lIarpochloa ralx Khadia acutipetala Gc1zania krabsfana

131121 1++2+1 1+++ I 132 I 111 I 1+1 I 1++ I

I I 1+ I I I I

+

I I I I 11 I I + I

of"

+ + R

Species group B

Aloe davyana lIypoxis argentea Ipomoea obscura Rhynchosia totta Eleph,7ntorrhiza elephantina Ledebouria ovatirolia 8,1rleria obtus,1 lIypoxis obtusa PlIvonia transvc1alensis

1332+1+ 11+1 I 111 +1+ 1+ ++1 1+1 I 111 I I 2 11 + 2 1+ + I 1+ 1 I

I I I I I I + I I I

+

I 11 RIR I I I I +IR I I I I I I I I I I

I I I + 1+ I I I I I

+

Species group C

Aristida juncirormis

1 I

1112 1322 I

Species group 0

12+ 11 12 I ++ I +I+R I 1+1+ 1 I I 1 +1 11 11 1+ I R I 12 + I +1 I 1 121 I I

lIeteromorpha triroliata Schlwhria pinn,1ta Teucrlum trifidum Ehrhart('! erecta

Zanthoxylum c,'pense Lippia seabberima Cluti,1 hirsueB

I I R I I I I I

++

Species group E

1222+1113+1+ I 32+1+1 R3 I ++ 1+ + RR R IR + IR

Aloe trnnsvnalensis

Ehretia rigid;] ·lIaemanthus humi Ius Kalanchoe thyrsirlora

1 11 I +1 I

1+ I I I

IR I I I

r

I I I

Species group F AsclcpiclS fruticosa Leonotis microphyll,7

R

I I 11

f!iheceropogon amplectans

I+R+I 11111 12 +1

Species croup G

Trachypogon spicatus lIelichrysum rugulosum Acalypha eaperonioidos D i coma llnOfllc1/ ,1

Gladiolus species 1101 iehrysum nudirol ium Athrixia e l ata Rhus zeyheri IInploearpha senposa LactuC8 species Sehistostephium crataegirolium

11 I I I ++ I I I I I I I

2 I I R I I I I I I I I I

+

1+121 13++1 1+++11 +++1 111 1+1++ I 11 RI ++ I I ++1 2+ I 1+ I + ++1 R +1 21 4+R I 11 R 11R +1 . I Rl I + I IR 1+ + I I + 1++ I

+ 2 ++ R

I I I I I I I I I I I + I I I I I 1+ I I I I I

S.Afr.l.Bot.,1993,59(2)

231

Table 1 Continued COHHUIII TY NUHBER

1.1

1.2

1.3

1. "

1.6

1.5

1. 6 . 1 RELEVE NUHBER

1.6.2

2201 2222 2222222202 222 22222 00000202100 0011 1122 2225 ,,32331,,39" 1114 ,,4211 72775 " 71139 3401 76 1 ,1, 7660 8605635911 994 32358 75567744736 4316

Species group H Rhus pyroides Rhus discolor lIyp"rrheni a hi rta

Plectracanthus madag8scariensis Berl
Setaria nigriroscris Z iz iphus mucrofwta Conyza podoccphala I nd igof'crc1 obscura C,1ru I aum /-Iood i i

l1yrsina africana Celtis c7fric,1na T,'gctus minuta Argyro I ob i um ve I uti num Procnspc1ragus setc1ceus Cusson/a pan/cu/e?en

Chef Janthes ecklonic1na felicia filifolia Oigitaria eriantha

I I I I I I+R I I 1++ I I I IR I I I I I I

1+1 2 +++ I +113 +11 I +1111+ 113+ 111 I + I + 11+21 1 12211 +21 I I 1 I +++ 1 +1 1 I +1++1 I + ++ 121+1++21 I I + 1 I +4111 111 I + I 1321 11 I 1+11 I +1 1++ 2 ++1 ++11 + I I R + I RI+R+++I I R I + + +11 11+ 1121 I I I + ++2 I I +12 RRI RI I R I R+ R+R I 1 13 +I+R + 1 +1 ++1 I I + +1 + I+++R I 1+ R I + RR I + I R++I I R I RI+l Rl I R+I+ I I 1++ +1 I I + + + 21 + I I I 1 1 1 +1 + I +1 +1 I I 1+ I

1 I I I I I I I IR 1++ I I I I I I

1211 I 2221212+ 112211 +111 1111+I+R+R+ 1 +2IR+ IR R++I I +R11111R + ++ 1+1+I+R+ RI 1111 12 ++++ 111 +++ I ++ I 1+ ++1+ ++1 1 +21 + I+R++11 I 11+122 1+RR 41 1111 R+I 112 21211412 +111 +IR 11 I 313131 R11411RI +12 +1 I +++11R++3 11 +1 + 1+ +1 1+++ 1+ +++ 1+1++ I ++1 2++ +21 2 121+1+1 I ++1 1++11+1++ 11 + 11 + I I R I 12121 +RI +11 +1 I 11 241 + 1 I 112 1 I + I 1 I I + 11 R+ I I ++ IR +1 I +1

.+ 11 1 R

+ +

I I 11 I + I + 1 I I I R R I 1+ I I I I I I I I I

Species group I Oiospyros Iycioides Pellaea en/omena/os Rhus rigida R1wnchelytrum repens Cheilanthes hirta May tenus heterophylla

Rhoicissus cridentata Euclea crispa Bidens pilosa Commel ina c1fricana Cymbopogon excavatus Ipomoea crassipcs Oiospyros /ihyteana Canthium gilfillanii Lfppia rehm,1nnii Ch,1etacanthus costatus

2 + +

+ R+ + 2 1

I I I I I I I I I I I 1+ I I I I

Specios group J 1+ + I

+

+ I

+ I 31+ 1121+21+1 11

Species group K 1+

Cynodon d"ctylon Borkhaya pinnc1tifld., Trichoneur" gr,1ndiglumis Chamaesyce inoquilaCer c1

.1

1 2

1+3+1 12+111 1++ + + I 11 +1 + I 1+ R+ I 11 R I

+1

lIel ic:IIf'Y SlIlII .1Ul'cun, (:ens

++ +

Crassu/(1 /c1nceo/,1tc1

l1icrochloa carrrc1 Cyanocis spec/osa Er,'grostis capen~is Stoebe vUlg"ris' Chloris virgc1tll Dianthus basutlcus

I 11 I I + I I I

+

I Rl + + 11 1 I + + + I R+ I + I + R I

Species group L

Indigoferll species Convolvulus s,'gittlltus

IRR1 IRn

Spec i os group H Crabbe" ac,1U1 is Vernonii1 oligoccphala Hermnnnia depressn Setarln sphacelata Trifolium africanum

I I I I + I

1+ ++1++ 11++ IR I ++ I + I ++ I+ 1+ +

I

+++ I ++ 11 ++++ 1+ ++ +++ + I + I + I 1+ ++ I 1 R 1+ + I + I ++1++ + 11Rl++1R+ +1 I 1 I + 1 11+ I + 11 1 + + I 111 +11 R + R I ++1+ +11 1+1

Spec i es group II lIetcropogon contortus Eragrostis curvula E I ionurus mut Icus T hemed.1 tr i <1ndra OrachlCJrlc1 serr.1tCJ AristidCJ congest .1 Eragrostis racamosa rristtlchya leucothrix

III 121111+112+1 12111111211 11 1 1111 + I 1 I 121+ 1122112211+1211212+111 ++111122+12 121122+ I 11 1+1221 111 1 11+11 +11111 211 1121+1 1+1 I 111112 2 +2 211111131+1111 112221321113231 11 +11+11+1+ 1+ + 1 111111 + 11 1111+11 111 I 2111 +11 ++111 I 11 11112 111 12 I 111+111+ + 1+11+1+11+11 +1+11 111111 1 I 111231 1 +111 1 1 R I

Species group 0 Berkhcya onopordifol ia Evolvulus alsinoides lferm.1nn i a I anc ira II ,1 Lactuca capensis Ledebouric' species Gnidi" burchell i i Z i z i phus zeyher ian" Salvlc' repens Oigitllria diagonalis Vernoni a c c'pens Is l1onsonia anguseiroli/f Ber/
+ ++

I I R I I I I 1+ I 1 I 1 I 1

++ + + R

R

R1 I I 1 1 IR I I + IR I +2 I 1 1 nl

1+ I I 1+ I I 1+ 11 I I I 1

1 RR I I R R I R I ++R I R I + 1 I + 1 R+I IR I + 1+ I 2 I 1 I I I 1 I + 1 1+1 I 1

232

capense, the shrub Clutia hirsuta, the forbes Schkuhria pinnata. Teucrium trifidum and Lippia scaberrima, and the graminoid Ehrharta erecta (species group D, Table 1). Species of species groups E, H, I, M and N are also common in this vegetation. The dominant trees are Ehretia rigida. Rhus pyroides. Ziziphus mucronata. Cussonia paniculata. May tenus heterophylla and Diospyros whyteana (Table 1). Dominant shrubs are Diospyros Iycioides. Felicia filifolia. Rhus discolor. R. rigida and Euclea crispa. The dominant grasses are Hyparrhenia hirta. Digitaria eriantha. Melinis repens. Cymbopogon excavatus. Heteropogon contortus. Eragrostis curvula. Themeda triandra. Elionurus muticus. Brachiaria serrata and Aristida congesta. Prominent forbs are Garuleum woodii and Ipomoea crassipes, and the xerophytic ferns Cheilanthes eckloniana. C. hirta and Pellaea calomelanos. Dense stands of the annual weeds Bidens pilosa and Tagetus minuta occur in areas of severe disturbance. Single specimens of the exotic succulent Opuntia sp. also occur in this community. All the releves in this plant community had bare soil patches with very little or no vegetation cover, possibly due to heavy grazing. In some of the releves the detrimental effect of rock rabbit (Pro cavia capensis) and porcupine (Hystrix africaeaustralis) activities on the vegetation was evident. The mean crown cover of the plant community was 58%. 1.4 The Diospyros lycioides - Leonotis microphylla Shrubland The Diospyros Iycioides - Leonotis microphylla Shrubland occurs on shallow «300 mm) soils of the Mispah Form · (MacVicar et al. 1977) with basaltic lava, agglomerate, tuff and diabase as the parent material (Figure 3) (Department of Mineral and Energy Affairs 1986). The community is situated at an altitude of 1600 - 1740 m above sea-level on slopes with an inclination of 2 - 7° on terrain units 1 and 3 (Figures 3 and 4). The above-ground rock cover in the community varied between 31 and 60% (Figure 3). On average, 43 species per sample plot were recorded. The community is characterized by species group F (Table 1) which includes the diagnostic grass species Diheteropogon amplectens and the forbes Leonotis microphylla and Asclepias fruticosa. Species of species groups G - I and M are common in this community (Table 1). The dominant trees in the community are Rhus pyroides. Celtis africana. May tenus heterophylla and Canthium gilfillanii. Dominant shrubs are Diospyros lycioides. Rhus discolor and Rhus rigida and dominant grasses include Trachypogon spicatus. Hyparrhenia hirta. Setaria nigrirostris. Eragrostis curvula. Heteropogon contortus. Themeda triandra. Elionurus muticus and Brachiaria serrata. Prominent forbs in the community are Acalypha caperonioides. Berkheya setifera and Ipomoea crassipes. The mean crown cover of the community was 69%. 1.5 The Diospyros lycioides - Trachypogon spicatus Shrubland The Diospyros lycioides - Trachypogon spicatus Shrubland occurs mainly on shallow «300 mm) soils of the Mispah Form (Mac Vicar et al. 1977) with basaltic lava, agglomerate and tuff as the parent material (Figure 3) (Department of

S.-Afr.Tydskr.Plantk.• 1993,59(2)

Mineral and Energy Affairs 1986). The community is situated at an altitude of 1640 - 1680 m above sea-level, mainly on southern and south-western slopes with an inclination of 8 - lr, on terrain unit 3 (Figures 3 and 4). The aboveground rock cover varied between 16 and 45%. On average, 40 species per sample plot were recorded. This plant community is not characterized by a specific diagnostic species group but rather by the presence of the species in species group G (Table 1) and the absence of the species in species group F (Table 1). Species of species groups H, I, M and N (Table 1) occur frequently in the community. Dominant grasses in the community are Trachypogon spicatus. Cymbopogon excavatus. Themeda triandra. Tristachya leucothrix. Elionurus muticus and Heteropogon contortus (Table 1). Prominent forbs are He/ichrysum rugulosum. Athrixia elata. Berkheya setifera. Crabbea acaulis and Cheilanthes hirta. Dominant shrubs are Diospyros Iycioides. Rhus discolor. R. rigida. Myrsine africana and Euclea crispa. Rhus zeyheri. Diospyros whyteana and Canthium gilfillanii are scattered trees in the community (Table 1). The mean crown cover of the community was 70%. 1.6 The Eragrostis plana - Eragrostis curvula Grassland The Eragrostis plana - Eragrostis curvula Grassland occurs mainly on yellow and red loam and clayey soils of the Hutton, Bainsvley. Westleigh and Pinedene forms and sometimes also on the dark vertic clayey soils of the Arcadia and Rensburg forms (MacVicar et al. 1977) (Figure 3). The parent material of the soils is undifferentiated Witwatersrand quartzite, shale, sandstone and diabase (Figure 3), while basaltic lava, agglomerate, tuff and dolerite may also occur in the community. The community is situated at an altitude of 1580 - 1680 m above sea-level on slopes with an inclination of 0 - 3° on terrain units 1, 3, 4 and 5 (Figures 3 and 4). The above-ground rock cover in the community varied from 0 to 20%. On average, 20 species per sample plot were recorded. Eragrostis plana (species group J, Table 1) with a high cover value is the only diagnostic species for the community. Species from species groups K - N (Table 1) also occur in this community. The mean basal cover of the plant community is 9%. The Eragrostis plana - Eragrostis curvula Grassland is divided into two sub-communities, namely: 1.6.1, the Eragrostis plana - Cynodon dactylon Grassland on terrain units 1, 3 and 4 with undifferentiated Witwatersrand quartzite, shale, and sandstone as the dominant geology (Department of Mineral and Energy Affairs 1986); and 1.6.2, the Eragrostis plana - Indigofera species Grassland on terrain units 4 and 5 with diabase as the dominant geology (Department of Mineral and Energy Affairs 1986). 1.6.1 The Eragrostis plana - Cynodon dactylon Grassland The Eragrostis plana - Cynodon dactylon Grassland occurs mainly on yellow and red loam and clayey soils of the Hutton and Bainsvley forms (Mac Vicar et al. 1977) (Figure 3). In the community there are single occurrences of soils that are of the Avalon. Westleigh, Pinedene, Mispah and

S.AfrJ.Bot., 1993, 59(2)

233

Arcadia forms (Mac Vicar et al. 1977). The parent material of the soils is mainly undifferentiated Witwatersrand quartzite, shale and sandstone with single occurrences of basaltic lava, agglomerate, tuff and dolerite (Figure 3). The mean soil depth in the community is 360 mm with an above-ground rock cover that varied between 0 and 20% (Figure 3). The community is situated at an altitude of 1580 - 1680 m above sea-level on slopes with an inclination of 1 - 3° on terrain units 1, 3 and 4 (Figures 3 and 4). The average number of species recorded per sample plot was 20. The community is characterized by the diagnostic pioneer grass species Cynodon dactylon, Triclwneura grandiglumis. Microchloa caffra. Eragrostis capensis and Chloris virgata and the forbs Berkheya pinnatifida. Chamaesyce inaequilatera. Helichrysum aureonitens. Crassula lanceolata. Cyanotis speciosa and Dianthus basuticus (species group K, Table 1). Species of species groups M and N (Table 1) are also present in the community. Dominant grasses are Eragrostis plana. E. racemosa. Themeda triandra. Heteropogon contortus and Aristida congesta. Prominent forbs are Hermannia depressa. Crabbea acaulis and Trifolium africanum. Scattered in the community are single occurrences of shrubs and trees such as Diospyros lycioides. Rhus rigida and Canthium gilfillanii. Localized disturbed areas are characterized by the occurrences of pioneer species such as Aristida congesta. Stoebe vulgaris. Cynodon dactylon and Chloris virgata. The mean basal cover of the community was 9%.

the parent material. The mean soil depth in the community is 975 mm with an above-ground rock cover that varied between 0 and 10% (Figure 3). The community is situated at an altitude of 1580 - 1620 m above sea-level on slopes with an inclination of 0 - 2° on terrain units 4 and 5 (Figures 3 and 4). On average, 19 species per sample plot were recorded. The community is characterized by the diagnostic scandent herbaceous creeper Convolvulus sagittatus and a forb Indigofera species (species group L, Table 1). The dominant grasses in the community are Eragrostis plana. E. curvula. Themeda triandra. Setaria sphacelata and Elionurus muticus (Table 1). Prominent forbs are Vernonia oligocephala and Trifolium africanum. No trees and shrubs are present in the community. The mean basal cover of the community is 8%. Ordination The floristic data was ordinated by using Detrended Correspondence Analysis (DEcORANA) (Hill 1979). The first and second axes of the ordination were used to illustrate the plant community--environment interactions. The first axis explains 68.1 % and the second axis 62.0% of the variation in the data set. The scatter diagram (Figure 5) shows a distinct separation between different communities. The Euclea crispa - Aloe davyana Shrubland (B), Diospyros lycioides - Heteromorpha trifoliata Shrubland (C) and Diospyros lycioides - Leonotis microphylla Shrubland (D) on the left side of the diagram occur on high-lying steep slopes with high above-ground rock cover. The Loudetia simplex - Eragrostis curvula Grassland (A), Diospyros lycioides - Trachypogon spicatus Shrubland (E) and Eragrostis plana - Eragrostis curvula Grassland (F) on the right side of the diagram occur on low-lying less steep slopes with low above-ground rock cover (Figure 5). No environmental variable could be associated with the distribution of the releves or plant communities along the second

1.6.2 The Eragrostis plana - Indigofera species Grassland The Eragrostis plana - Indigofera species Grassland occurs on black vertic clayey soils (>55% clay) of the Arcadia and Rensburg forms (Mac Vicar et al. 1977) with dolerite and diabase as the parent material (Figure 3) (Department of Mineral and Energy Affairs 1986). In the community there are single occurrences of soils of the Avalon Form (MacVicar et al. 1977) with basaltic lava, agglomerate and tuff as 500~----------------------------

________________________________

Steep slopes High lying ........ ~----------------------~---l.~ . High surface-rock cover

--"

--

c F

400

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Fi /

F

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200

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Figure 5 A DECORANA ordination of the vegetation of the Ib Land Type in the Villiers - Grootvlei area, South Africa. A, Loudetia simplex - Eragrostis curvula Grassland; B, Euclea crispa - Aloe davyana Shrubland; C, Diospyros lycioides - Heterorrwrpha trifoliata Shrubland; D, Diospyros lycioides - Leonotis microphylla Shrubland; E, Diospyros lycioides - Trachypogon spicatus Shrubland; F, Eragrostis plana -Indigo/era species Grassland.

234

axis. The environmental gradients associated with the variation in plant community distribution are altitude, slope and above-ground rock cover.

Concluding remarks The plant communities identified in this study are considered as ecologically sound units as they can be related to specific environmental conditions. These ecological units are clearly recognized in the field and should be used to delimit field management units on the farm scale. Optimal production of livestock, coupled with efficient conservation of the natural resources can only be attained when veld management strategies are based on ecologically defined management units. The classification provided by this study could also contribute to the syntaxonomy of the entire Grassland Biome, if the data could be incorporated in the syntaxonomical synthesis presently being done by the Department of Botany, University of Pretoria.

Acknowledgements Mr. H. Bezuidenhout is thanked for valuable help with the phytosociological table. The Department of Agricultural Development is thanked for financial support.

References ACOCKS, J.P.H. 1988. Veld Types of South Africa, 3rd ed., Mem. bot. Surv. S. Afr. 57: 1 - 146. BEZUIDENHOUT, H. 1988. 'n Plantsosiologiese studie van die Mooirivieropvanggebied, Transvaal. M.Sc. thesis, Potchefstroom University for Christian Higher Education, Potchefstroom. BLOEM, KJ. 1988. 'n Plantsosiologiese studie van die Verlorenvalei-natuurreservaat, Transvaal. M.Sc. thesis, University of Pretoria, Pretoria. BRAUN-BLANQUET, J. 1932. Plant sociology: The study of plant communities (translated and edited by G.D. Fuller & H.S. . Conrad). McGraw-Hill, New York. BREDENKAMP, G.J. 1975. Plantsosiologiese studie van die Suikerbosrand-Natuurreservaat. UnpUblished M.Sc. thesis, University of Pretoria, Pretoria. BREDENKAMP, G.J., JOUBERT, A.F. & BEZUIDENHOUT, H. 1989. A reconnaissance survey of the vegetation of the plains in the Potchefstroom - Fochville - Parys area. S. Afr. 1. Bot. 55: 199 - 206. BREITENBACH, P.J.J. 1991. Die fitososiologie van die Villiers - Grootvlei-omgewing. MSc thesis, University of Pretoria, Pretoria. BREITENBACH, PJJ., MYBURGH, WJ., THERON, G.K. & BREDENKAMP, GJ. 1992. The phytosociology of the Villiers - Grootvlei area, South Africa. 1. Physical environment and the plant communities of the Bb Land Type. S. Afr. 1. Bot. 58: 239 - 249. BREITENBACH, P.J.J., MYBURGH, W.J., THERON, G.K. & BREDENKAMP, GJ. 1993. The phytosociology of the Villiers - Grootvlei area, South Africa 2. The plant communities of the Ba Land Type. S. Afr. 1 . Bot. 59: 218 - 226.

S.-Afr.Tydskr.Plantk.,1993,59(2) CAIN, S.A. & CASTRO, G.M.deO. 1959. Manual of vegetation analysis . Harper & Brothers, New York. DEALL, G.B. 1985. A plant-ecological study of the Eastern Transvaal escarpment in the Sabie area, Vols. 1 and 2. M.Sc. thesis, University of Pretoria, Pretoria. DEPARTMENT OF AGRICULTURE AND WATER AFFAIRS. 1986. Landbou-ontwikkelingsprogram: Hoeveldstreek. Directorate Agricultural Information. Government Printer, Pretoria. DEPARTMENT OF MINERAL AND ENERGY AFFAIRS. 1986. 1:250000 2628 EAST RAND Geological map. Geological Survey, Pretoria. EDWARDS, D. 1972. Botanical survey and agriculture. Proc. Grassld. Soc. sth. Afr. 7: 15 - 19. EDWARDS, D. 1979. The role of plant ecology in the development of South Africa. Bothalia 12: 748 - 751. GmBS RUSSELL, G.E., REID, C., VAN ROOYEN, J. & SMOOK, L. 1985. List of species of southern African plants, 2nd ed., Part 1. Mem. bot. Surv. S. Afr. 51: 1 - 152. GmBS RUSSELL, G.E., WELMAN, W.G., RETIEF, E., IMMELMAN, K.L., GERMISHUIZEN, G., PIENAAR, BJ., VAN WYK, M., NICHOLAS, A., DE WET, C., MOGFORD, J.C. & MULVENNA, J. 1987. List of species of southern African plants, 2nd ed., Part 2. Mem. bot. Surv. S. Afr. 56: 1 - 270. HILL, M.O. 1979. DECORANA - A FORTRAN Program for Detrended Correspondence Analysis and Reciprocal Averaging. Cornell University, Ithaca, N.Y. KOOD, M.S. 1990. A phytosociological survey of the vegetation of the north western Orange Free State. M.Sc. thesis, University of Pretoria, Pretoria. LAND TYPE SURVEY STAFF. 1984. Land Types of the maps 2628 East Rand, 2630 Mbabane. Mem. agric. nat. Resour. S. Afr. No.5. MACVICAR, C.N., DE VILLIERS, J.M., LOXTON, R.F., VERSTER, E., LAMBRECHTS, J.J.N., MERRYWEATHER, F.R., LE ROUX, J., VAN ROOYEN, T.H. & HARMSE, H.J.vonM. 1977. Soil classification: A binomial system for South Africa. Department of Agricultural Technical Services, Pretoria. MYBURGH, WJ., BREITENBACH, P.J.J., THERON, G.K. & BREDENKAMP, G.J. 1992. Die fitososiologie van die Bankenveld in die Grootvlei-omgewing, Suid-Transvaal. Bothalia 22: 245 - 254. OOSTING, H.J. 1956. The study of plant communities. W.H. Freeman & Co., San Francisco. SOUTH AFRICA (REPUBLIC). 1978. 1:50000 Topographical Series. 2628 GROOTVLEI. Government Printer, Pretoria. TURNER, BJ. 1989. A phytosociological study of the southeastern Transvaal Highveld grasslands. M.Sc. thesis, University of Pretoria, Pretoria. VAN ROOYEN, N. 1978. 'n Ekologiese studie van die plantgemeenskappe van die Punda Malia - Pafuri - Wambiyagebied in die Nasionale Krugerwildtuin. M.Sc. thesis, University of Pretoria, Pretoria. WERGER, MJ.A. 1974. On concepts and techniques applied in the Ziirich-Montpellier method of vegetation survey. Bothalia 11: 309 - 323. WESTFALL, R.H., DEDNAM, G., VAN ROOYEN, N., THERON, G.K. 1982. PHYWrAB - A program package for Braun-Blanquet tables . Vegetatio 49: 35 - 37. WESTFALL, R.H. & PANAGOS, M.D. 1984. A cover meter for canopy and basal cover estimations. Bothalia 15: 241 - 244.