The Plant Communities of the Undulating Grassland of the Vredefort - Kroonstad - Lindley - Heilbron Area, Northern Orange Free State

224 S.Afr.l.Bot., 1992, 58(4): 224 - 230 The plant communities of the undulating grassland of the Vredefort - Kroonstad - Lindley - Heilbron area, northern Orange Free State

E.R. Fuls, G.J. Bredenkamp and N. van Rooyen Department of Botany, University of Pretoria, Pretoria, 0002 Republic of South Africa

Received 23 October 1991; revised 31 March 1992

An analysis of the plant communities of the undulating grasslands of the northern Orange Free State is presented. Releves were compiled in 107 stratified random sample plots. Care was taken to avoid sampling of severely degraded areas. A TWINSPAN classification, refined by Braun-Blanquet procedures, revealed six distinct plant communities. A hierarchical classification, description and ecological interpretation of the plant communities are presented.

'n Analise van die plantgemeenskappe van die golwende grasveld van die noordelike Oranje-Vrystaat word gegee. Releves is in 107 gestratifiseerde ewekansig gekose monsterpersele saamgestel. Erg versteurde gebiede is deurgaans vermy. 'n TWINSPAN-klassifikasie, verfyn deur Braun-Blanquet-prosedures, toon ses duidelik onderskeibare plantgemeenskappe. 'n Hierargiese klassifikasie, beskrywing en ekologiese inter pretasie van hierdie plantgemeenskappeword aangebied.

Keywords: Braun-Blanquet classification, grassland biome, synecology, TWINSPAN.

Introduction ing on, the study area are Kroonstad, Heilbron, Vredefort, The northern part of the Orange Free State is one of the Lindley and Koppies. The area covers approximately most important agricultural regions of southern Africa, both 750 000 ha. The study area forms part of the Highveld in terms of intensive crop production and extensive stock inland plateau and consists predominantly of smoothly farming (Schecpers 1975; Mentis & Huntley 1982). The plained or gently rolling land surfaces of the miocene age widespread ploughing of arable land concomitant with livestock grazing pressure resulted in the destruction of large portions of pristine vegetation in the area. Further more, since the broad vegetation classification and mapping 2~E 2nO'E 2BOE presented by Acocks in 1953 (A cocks 1953, 1988), very ,ps -1------::7"7/"777777:77"::"77777"7"".,-'-'---,-27'5 little advance has been made towards a more detailed classification and description of the vegetation of the area. In view of the predicament of the natural vegetation of the study area, it is imperative that future land-use planning, management and conservation strategies are based on sound plant ecological principles. To facilitate optimal resource utilization in general, and to assess the conservation status 2]030'$ 27l30'S of the vegetation in particular, a detailed identification, classification and mapping of the vegetation of the region has been undertaken. The physical environment and major plant communities and the vegetation of the rocky outcrops of the study area are described by Fuls et al. (1992a) and Fuls et al. (1992b), respectively. In this paper, the plant communities and asso ciated habitats of the undulating grassland of the Vrcdefort - Kroonstad - Lindley - Heilbron area of the northern Orange Free State are described. This study forms an integral part of the ultimate goal to compile a comprehensive syntaxonomi 21"5 ~ 15"S. . 23' 2 J10 \\I\Aomm:S~E1 21 OS Namibia cal synthesis of the grasslands of southern Africa (see also Transvaal I Bredenkamp et al. 1989; Kooij et al. 1990). 25" ~ ~ I 25' i U/ -. swo< " o~ t I ~L __ -';_~- ~ /Orangef. /' Natal Study area N : Free~h o 29" \ South Africa \~~a~:V_'. 29" The study area comprises the eastern part of the 2726 \ Kroonstad map (1 :250000) (Land Type Survey Staff 1984), Cape Province within the climatic climax grassland biome of southern 33°S ~ 33°S 19' 23' 35'E Africa (Mentis & Huntley 1982). The area is situated between 27°11' and 28°10' E longitude and 27°00' and Figure 1 The study area (hatched) in which the plant commun 28°00' S latitude (Figure 1). Towns situated in, or border- ities of the undulating grassland were analysed. S.AfrJ.Bot., 1992,58(4) 225

(Mentis & Huntley 1982) and is situated between l300 m 1979) was applied to the floristic data set in order to derive and 1700 m above sea-level. The topography comprises a a first approximation of the vegetation types of the area. Re mosaic of flat, slightly undulating and undulating terrain finement of this classification was done by means of Braun (Land Type Survey Staff 1984). Isolated hills and ridges are Blanquet procedures (see also Bredenkamp et al. 1989; encountered occasionally. The area covered by the undula Kooij et al. 1990). ting grassland comprises more than 90% of the total study area. Surface rocks are generally absent in the undulating Results grassland. A diagrammatic presentation of the hierarchical classifica tion and associated environmental interpretation of the six Methods plant communities is presented in Figure 2. The vegetation Releves were compiled in 107 stratified random sample of the undulating grassland (Table 1) can be broadly classi plots. However, care was taken to restrict sample plots to fied as a Themeda triandra - Eragrostis curvula Grassland. undisturbed vegetation whenever possible. Severely de Other graminoids with a high constancy in all communities graded areas were avoided, but as the vegetation is widely include Cymbopogon plurinodis, Panicum coloratum. Cyno utilized for livestock production, the condition of the stands don dactylon, Digitaria eriantha and Eragrostis obtusa differed. Stratification was based on topographical position (species group K - Table 1). These graminoids have charac or terrain unit [where terrain unit 1 comprises crests of teristically wide ecological amplitudes and therefore occur undulating terrain; terrain unit 3 comprises slopes between widespread. The small karroid shrubs Felicia muricata and crests and bottomland; and terrain unit 4 comprises bottom Pentzia globosa are often encountered, even in relatively land but excludes watercourses (Land Type Survey Staff undisturbed grassland. The widespread occurrence of these 1984)] as well as soil form and geology. Plot sizes were hardy karroid shrubs is indicative of the expansion of the fixed at 100 m2 (Scheepers 1975). In each sample plot all Karoo biome at the expense of the adjacent grassland biome species were recorded, using the Braun-Blanquet cover (Acocks 1988). The Karoo biome expansion can be ascribed abundance values (Mueller-Dombois & Ellenberg 1974). to adverse micro-climatic conditions engendered by mis Taxa names conform to those of Gibbs Russell et al. (1985, management of the grass layer (Fuls 1992), which favours 1987). Environmental data recorded includes geology, topo the drought resistant karroid shrubs. The numerous forb graphical position, soil type and depth, soil texture, aspect, species often encountered in the grassland may also be the slope, rockiness of the soil surface, erosion, soil crusting! result of disturbance. Forb species which are commonly compaction and utilization by herbivores. encountered include Conyza podocephala. Geigeria aspera, Two-way indicator species analysis (TWINSPAN) (Hill Berkheya pinnatifida, Ifelichrysum rugulosum. Berkheya

Undulating I grassland I - Dry -Moist - Terrain units - Terrain unit 4 1 & 3 - Mostly disturbed - Pristine or and degraded slightly - >35% clay in r-- degraded - r B-horizon

-Sandy and - Deep soils -Mostly - Duplex soils shallow soils - >25% clay in clayey -Increase or - <25% clay in soil profile A-horizons invasion of soil profile - Relatively dry -Moist woody species -Dry I well to moist I - Mostly drier drained intermediately - Disturbed I drained J L degraded

-Slightly -More -Slightly -Moist drier moist drier -Lower - Higher -Lower - Higher lying lying lying lying -More - Degraded degraded

~,.. ~,.. ". ~,.. ~,.. ,.. 1.1.1 1.1.2(a) 1.1.2(b) 1.2.1(a) 1.2.1 (b) 1.2.2 Figure 2 The hierarchical classification and associated environmental characteristics of the six plant communities. Numbers of plant communities correspond with numbers and descriptions of communities in the text. f:l Table 1 Phytosociological table of the vegetation of the undulating grassland of the northern Orange Free State 0\

Corrrnunity number 1.1 1.2

1. 1.1 1 • 1 • 2 1.2.1 1. 2 . 2

A B A B 10010101010001000111110011 10000000010010110010 1000001010001111100000000 00000010000 100000100010101 1110011101 Re I eve numbe r 19216321430120236062341913 45966851856803049359 0121042614343012447055080 80012913740 261194178864035 7882223475 90240841091337905263531486 00624270016619352401 8658912724894454232738384 15826501122 585497687976578 5201700872 ------Spec ies Group A Trichoneura grandiglumis I+R++RRRRR1RR++R + RRR+ I R Helichrysum dregeanum 1++ RR+ + 1 R11R++++R IR R + R Sporobolus discosporus IR+R R++ R1 + ++ RR+ 1 + R Lippia scaberrima IR RRR R RRRR R R 1 R R R oseeospermum scariosum IRR R +R+ R + R 1 R+ RI R R R Commel ina af'ricana 1 RR R + R R ++RI I + Eragrostis gummif'lua 1 + RR R RR RRI 1 R Triraphis andropogonoides 1 R RR + R RI I Bulbine abyssinica 1 RRR R R R 1 R R I R Ariseida canescens I + R A R + I 1 Brachiaria serraea 1 +R R R 1 I Ariseida dif'f'usa I R R R 1 1 R

Species Group B Argyrolobium humile I IR R R + R RR R 1 R R 1 Hermannia coccocarpa IR IR R + RR R 1 R R R IR Eragroscis capensis 1 RI RR R ++ I 1 Digicaria tricholaenoides 1 R + 1 + + + + R 1 R 1 R Ziziphus zeyheriana 1 1 +R ++ RI I

Species Group C

Heeeropogon concortus IAR3RRB+A++ ARA+R + R1++RI RR R R +RR++ +1+ A R R +1 Anehospermum hispidulum 1 RR +RRR RR RRR RRI RR R R RRRR R R RI R R R R I Hermannia depressa 1 R R+ +R RR +RR+R+RR+ 1 ++RR R+R + ++ +1 R R I

Species Group 0 Cyperus rupestris 1 + RRR RR RR RR +R IR R IRRRR RR R R R +R11 R +1 R Eragroscris superba 1+ +R R + R+ + R'RRI R 1R +1 R R R 1 1

Species Group E Elionurus muticus IA A++ABB AB3B+ RA +B++ IAAA 1++A3AAR3+ABABBBIA++B+1R1R+13+BBBA3A3B11 + + 1 R IR R + Vl Setaria sphacelata 1 RRA111111 1+1B1+A++AA +AAIR +RBR1R A+ AR+AR1+RIRR+ +R+ R+++1 ++ R 1R + RI RR R ++ + I BR ~ Ariscida congesta subsp. congesta 1++RRRR+RR++RRR++RR+RRR1++ IRR R R R R IRRRR+R + RR+R+ R + R R 1+ 1 R + q> Arctotis arctocoides 1 R+R+ R R RR R RR +1 +R R+ RI R R R R+ RR 1 R IR Epa/tes gariepina 1+ + + + IR + R 1 R + R R+ R R I I R -7 ~ ~ Species Group F '-0 ;- Crabbea acau/is 1 R RR + R RRR R IR RRR RR+R R R +RRI +RR+ R R R R +R R R RfR+R++RR RR 1 R R +1 R 1 ::l Hibiscus trionum IRRR +RR + RR I+R R RR R RR 1 R+ + RR+R RRR+R+RR RRRI+R RR RR RI + R R RR+ 1 ~ fficroch/oa caf'f'ra I I+RR1+++RR11+++++ +1 R ++ R 1 RRR R + RRI R1 RRR+ +R+ + RR I + R R I R R 1 R 1 Chamaesyce inequilaCera I R RR R R \0 I RR R R RI R R + R R + R I RRRR R R R I R R R I RR 1 -\0 Berkheya onopordif'o/ia I R R RRR+RRRR RR 1 RRR R R RRRR+I R R R I R RRR I R R I R RI ~ Oigicaria argyrograpca IR R1R1 A R R ++ I + R R R A+ I R R +R 1 R + I R+R R 1 R VI I I 00 ~ Table 1 Continued en ::<'> species Group G <-. I R R++R+ R++ +, I R R + R A R +I+R R++ A IR+1A+ R+ R + I + I b::1 Ariscida biparCica + RR R R R I R R R 1+1 R RR lRI R I Panicum scapfianum R R +1 R+RR + RR I ?- I + R I R R RRR R I R + RI+ ++R RR R+ 1 I ..... Gazania krebsiana \0 \0 Species Group H P + , IRR1+++1+++1 VI R I R + R I R R R I 00 Acacia karroo R R IR R R 1+++l++R1++1 Procasparagus laricinus I + R IR ~ I I + R I R IR RR+R+RRI Tageees minuea R I I RR+ R R R I Rhus pyroides I I I R + R++ I + I IR I Bidens pilosa I R I RRR R I Rubia horrida I I I RI I RI RR RI Convolvulus sagieeaCus IR I R+1 R I Chloris virgaea R I I I I I IRRR R I Ziziphus mucronaea I R R IA R + +1 Sporobolus africanus AI I I I I I R+ + + I Archyranehes aspera I R BIRR R I Penniseeum sphacelaeum I I I R I I I ++ R I Teucrium criridum I 1++ R I Sporobolus rimbriacus I I

Species Group I ++ I 1 R I + R 133 llRB ARB RIB B RI Secaria nigriroseris RR R I RRRR IR +R+ R I +RR+ I Seddera capensis I R I I R R I I + R IR+ R R I R I Galium capense 1+ + I + R 11 R B IR + A +1 Sporobolus ioclados RI ... I + I I R R + I R R 1+ 1A RI Eragroseis micraneha I + + I R RI +R I Ornichogalum cenuirolium I R I

Species Group J RR+ 3+ +IB1A+ARR+3+113B+ 33BR33ABBAAI3+B A++ RA I R R R R R RBI B+ RR+RRRR++RR A+R+IB+ R R+R+AR+ [ragrostiS plana IR+ R RRRR+R R I R R R +R I++RR R R IR RRR + RR R+IR R RRR R+I Salvia runcinaea I RRRR +R I RR I RR I+R R RR I + I Sucera auraneiaca 1 R I R I R RR R R R R I + R R I + R 1R RR I I Nidorella anomala R R+ I RR 1+ R R + R I R R I Seabiosa eolumbaria 1/ R R +IR R

Spec i es Group K +A1A++AA+BA3+BA1BBABAB1AABIABRA++AR+AB++BA+A1ARIB+Al++ABABAABAAAAAA+AB++AIAR+AA+BB31RIABBRAA+ABAA++B+I++B++ABA++1 Eragroscis curvula 54345443344A3B44444453334BI4345B5443435334334441355444554343444443434B5551B3544543B5513B453345333B33413A+34343441 Themeda eriandra + ++lA+R1BBA11A++R+A B++IARB+3+BBAAB AB+BB1AAIBRRA+A++BAA1AA+AAA+ A++ A I +R +BA1R IR R+ +R 1 AR +1+A3 AAI Cymbopogon plurinoidis +R1R R+R ++11 + ++ +RIA++ lR R 1+ RI+1+++R+ 1+RR++111 +RRRA +IA +11+1 R +1 R R+++ R ++ 1 AABABAA+AI Panieum coloraCum ++R R RR + + 1RI + R RRI R+Rl R R RR++R R R IAR+R RR+ 11R R +R RAR++RI+A + A +1 Cynodon daetylon +R R R R1A AI RR+ + + R + I +RR R+++R+ + A + R IR 1 R I R RRA +R +R +1 BRA I Digicaria erianeha R+ R R R R R R RRRR 1+ R R RR RR+ RIR+RR RRR R RRR R RRR+IR R+R R R RIR +RRRR 1R I + RR R I [ragroscis obeusa +R+ R R + + + R+ IR R R R R RR IR++R R +R R ~ R+ ++ +1+ + +RRR RI+ R R+ I+++R+ +R1 I PenCzia globosa RR++R R RRRR + RRR RR I R R R+ R RRI + + +R lR 1R R R I R+ R R IR ++ +R 1R I 1 + +++RI Felicia murieaea R R +RR + R R1R R I R RRR+ RR +R +RRI R R R+ RR R RR I lR+ + R IR R + + +RI+++ ++RR+ I Conyza podoeephala RRR R RR IRR RRRRRRRRRRRIRRRR RR+RRRR+R R +IR+R+R+ RI R +RR R+I ++RRI Geigeria aspera R R RR+RRR I RRRR R RR RR RRRI RRR R+ +RRRR RR I ++RRRR+RRI+RRRR R + + R IR R R + RI Berkheya pinnaeirida R RRRRRR RR R R + I +R1+R R+RR1 R+ RI+ RR+ + R R 1R RI R R RIR RR ++RI R I Helichrysum rugulosum R R R R R I + R 1 R I +R + R R R+ R I R R R ++ + 11 R + + + I +R + + I Berkheya radula Bulbins narcissirolia R R R R R R R I R + I R R RR R R RR I R R I R RR R I R R R I Blepharis ineegrirolia R R RR R RR RR I RR R R I R RR RR R + I + R I R R R R I RR I Halarrida densirlora R R R R IR RR+ R R+ R I R RR I R I R+ RR I R R RI Monsonia anguscifolia R R R R I R RR I RR R R R R I R R I RR R I RR R I Conyza bonariensis R R I R I R R + R I+R I R R I + +1 R R I Hibiscus pusillus R I R I R R+ R+ I R I R I R +R I Solanum pandurirorme R R R R I R+ I + R R RI + I R R I R I RR R R R R R R R I R R R R I R R IR R I R I + I Sonehus dregeanus tv ~ 228 S.-Afr.Tydskr.Plantk., 1992,58(4)

radula and Blepharis integrifolia (species group K - Table 1.1 Elionurus muticus - Themeda triandra Upland 1). Shrubs and trees are seldom encountered in the undula Grassland (type releve: 150) ting grassland. The most conspicuous tree species that may This plant community occurs on the higher lying areas (ter be found occasionally is Acacia karroo. In disturbed places rain units 1 and 3) (Figure 3) and is restricted to reasonably this tree species often invades and may even become well-drained to well-drained soils. The most conspicuous dominant, presenting a serious bush-encroachment problem diagnostic graminoid is Elionurus muticus, a perennial, (Bredenkamp et al. 1989). All trees in the area are small and tufted grass species (species group E - Table 1). Other diag shrublike, seldom more than four metres in height. nostic grass species are the medium-sized, tufted, perennial Generally, this undulating grassland has a patchy appear Setaria sphacelata and the small tufted annuallbiennial ance due to uneven utilization by livestock. Slopes are Aristida congesta subsp. congesta, a pioneer species which seldom in excess of four degrees. The undulating grassland becomes abundant in disturbed areas. The diagnostic forb is not particularly species-rich, being mostly dominated by a species are Arctotis arctotoides and Epaltes gariepina few grass species (Table 1). A total of 217 species were (species group E - Table 1). This upland grassland encloses recorded in the 107 sample plots, with the average number two distinct plant communities: of species per sample plot being 24. The vegetation was divided into six distinct plant communities (Table 1). 1.1.1 Trichoneura grandiglumis - Microchloa caffra Grassland (type releve: 139) Classification This grassland is found on the drier crests of the undulating A hierarchical classification of the plant communities of the terrain (Figure 3). The plant community is restricted to the Eragrostis curvula - Themeda triandra Grassland is as well-drained, sandy soils which generally have a clay con follows: tent of less than 25%. Exposed rocks (covering less than Eragrostis curvula - Themeda triandra Grassland 20% of the soil surface), consisting of sandstone, dolerite and/or mudstone, are occasionally associated with this plant 1.1 Elionurus muticus - Themeda triandra Upland community. Diagnostic graminoids include the small, tufted, Grassland annual grass species Trichoneura grandiglumis and Sporo 1.1.1 Trichoneura grandiglumis - Microchloa caffra bolus discosporus, as well as the medium-sized, tufted, Grassland perennial Eragrostis gummiflua (species group A - Table 1). 1.1.2 Cymbopogon plurinodis - Elionurus muticus Grass- The small, tufted, perennial grass species Microchloa caffra land (species group F) as well as the large, tufted, perennial grass 1.1.2(a) Argyrolobium humile - Aristida bipartita Variant species Heteropogon contort us (species group C) were 1.1.2(b) Variant Aristida congesta - Panicum colora tum found to have a characteristically high constancy and cover/ 1.2 Eragrostis plana - Themeda triandra Lowland abundance in this plant community (Table 1). Diagnostic Grassland forbs include I-Ielichrysum dregeanum, Lippia scaberrima, 1.2.1 Setaria nigrirostris - Eragrostis plana Grassland Osteospermum scariosum and Commelina africana (species 1.2.1(a) Crabbea acaulis - Hibiscus trionum Variant group A). Diagnostic species were found to be subordinate 1.2.1(b) Eragrostis plana Variant and do not tend to become dominant. Significant decreases 1.2.2 Panicum coloratum - Acacia karroo Low Thicket in crown cover and other signs of degradation were often encountered in this grassland. Description of the communities The floristics and associated environmental attributes for the 1.1.2 Cymhopogon plurinodis - Elionurus muticus respective plant communities (Table 1) are given below. Grassland (type releve: 145) This plant community is encountered on the crests of the un Eragrostis curvula - Themeda triandra Grassland (type dulating terrain as well as areas adjacent to the crests releve: 67) (Figure 3). It occurs on relatively well-drained soils which This plant community occurs throughout the undulating mostly have a clay content of more than 25%. This com grasslands of the study area, excluding the rocky outcrops munity does not contain exclusive diagnostic species but is and watercourses. Themeda triandra, a widespread, relative rather characterized by the absence of the diagnostic species ly large, tufted, perennial grass species, is by far the most of the Trichoneura grandiglumis - Microchloa caffra Grass dominant and conspicuous species. This graminoid often land (species group A - Table 1). In addition, significant comprises more than 50% of the canopy cover, occasionally increases in the abundance and/or occurrence of graminoids rising to as much as 90%. Other conspicuous tufted, peren such as Elionurus muticus (species group E) and Cymbo nial grass species which are mostly present are Eragrostis pogon plurinodis (species group K) were recorded within curvula and Cymbopogon plurinodis. In well-preserved this plant community (Table 1). Species which are encount areas, healthy perennial grass populations suppress forbs, ered in this association but are absent from the Trichoneura dwarf karroid shrubs and woody species. However, in places grandiglumis - Microchloa caffra community include the where excessive and prolonged disturbance occurs, an in large, tufted, perennial grass species Aristida bipartita (a crease in forbs and woody species results. Species which are species characteristically associated with clayey soils), as generally encountered in this plant community are listed well as the forbs Gazania krebsiana (species group G) and under species group K (Table 1). The following plant com Sutera auriantica, Nidorella anomala and Scabiosa munities were distinguished within this broad, major plant columbaria (all indicative of increased soil moisture) community: (species group J - Table 1). A noteworthy increase in the S.Afr.J.Bot.,1992,58(4) 229

1.1.2(a) 1.1.1 1.1.2(a) 1.1.2(b) 1.2.1(a) 1.2.1(b) 1.2.2 1.1.2(b) 1.1.1

Plant commu nity

Terrain unit 3 3 4 5 4 3

Figure 3 A schematic illustration of the distribution of the plant communities along the terrain form gradient.

cover/abundance of Eragrostis plana, a wiry, tufted, 1.2 Eragrostis plana - Themeda triandra Lowland perennial grass species associated with moist, low-lying and Grassland (type releve: 116) disturbed areas, was also recorded in this plant community This plant community occurs on low-lying areas (bottom (species group J). Two variants were distinguished within land) (terrain unit 4) with moderately to poorly drained, this plant community: deep, clayey soils (Figure 3). It is principally characterized by an increase in the cover/abundance of Eragrostis plana 1.1.2(a) Argyrolobium humile - Aristida bipartita Vari (species group J - Table 1). Diagnostic species include the ant (type releve: 91) tufted, perennial grass species Setaria nigrirostris, the This plant community can be found on relatively well stoloniferous, mat-forming, perennial grass species Sporo drained (relatively dry), higher-lying, clayey soils (Figure bolus ioclados, as well as the forb Galium capense (species 3). Diagnostic species of this plant community are sub group I - Table 1). The constancy of the forb Salvia ordinate forbs with a low constancy and abundance such as runcinata was found to be higher within this plant Argyrolobium humile and Hermannia coccocarpa (species community (species group J - Table 1). Significant is the group B - Table 1). This community is also characterized by low constancy of graminoids such as Elionurus muticus, the increased abundance and constancy of Aristida bipartita Setaria sphacelata and Aristida congesta subsp. congesta in (species group G - Table I). Other graminoids with limited this plant community (species group E - Table 1). Further diagnostic value are Eragrostis capensis and Digitaria more, the cover/abundance and constancy of the large, tricholaenoides (species group B - Table 1). The small, tufted, perennial graminoid Cymbopogon plurinodis woody shrub Ziziphus zeyheriana is sometimes encountered in this plant community (species group B - Table 1). decreases markedly within this plant community (species group K - Table 1). Unfortunately, this plant community 1.1.2(b) Aristida congesta Panicum coloratum was mostly found to be degraded. The lowland grassland is Variant (type releve: 142) predominantly a grassland community, but a significant portion thereof, especially in the south-western parts of the This plant community is encountered on relatively well study area, contains conspicuous woody vegetation. This drained [albeit more moist than 1.1.2(a)], lower-lying, clay ey soils (Figure 3). This variant does not contain diagnostic lowland grassland encloses two distinct plant communities (Table 1): species which are exclusive to this specific plant community but is rather characterized by graminoids which have differ ential value owing to increases in cover/abundance within 1.2.1 Setaria nigrirostris - Eragrostis plana Grassland this plant community (Table 1). These include Aristida (type releve: 68) congesta subsp. congest a (species group E) and Panicum This grassland is encountered on moist, low-lying areas coloratum (species group K) (Table 1). Noteworthy is the where woody species are mostly absent (Figure 3). This general absence of the grass species Heteropogon contortus plant community does not contain species with a strong as well as the forbs Anthospermum hispidulum and diagnostic value (Table 1). Conspicuous species with limited Hermannia depressa from this plant community (species diagnostic value are Eragrostis plana (species group J) and group C - Table 1). The general absence of the latter species Setaria nigrirostris (species group I - Table 1). This confirms that this plant community is associated with grassland consists of two variants which are mainly distin increased soil moisture in comparison to the Argyrolobium guished by differences in the constancy of subordinate forb humile - Aristida bipartita Variant. species: 230 S.-Afr.Tydskr.Plantk., 1992.58(4)

1.2.1(a) Crabbea acaulis - Hibiscus trionum Variant rated first and foremost into land-use planning and manage (type releve: 5) ment. Future research will concentrate more specifically on This plant community is found on the higher-lying areas of the conservation status and ecological importance of the terrain unit 4 (Figure 3). These areas are slightly drier and species and plant communities of this region. are apparently less disturbed than the lower-lying areas. Species with a high constancy in this plant community are Acknowledgements the forbs Crabbe a acaulis. Hibiscus trionum and Chamae The assistance of Mrs M.S . Deutschlander is much apprecia syce inequilatera (species group F - Table 1). Noteworthy is ted. The research was funded by the Department of Environ the low constancy and cover/abundance of species listed mental Affairs. under species group E in this plant community (Table 1). References 1.2.1(b) Eragrostis plana Variant (type releve: 125) ACOCKS, J.P.H. 1953. Veld types of South Africa, 1st edn. Mem. This plant community is encountered on the lower-lying bOI. Surv. S. Afr. 28: 1 - 192. areas of terrain unit 4 (Figure 3) which were found to be ACOCKS, l .P.H. 1988. Veld types of South Africa, 3rd edn. disturbed throughout. This variant is characterized by a high Mem. bOI. Surv. S. Afr. 57: 1 - 146. cover/abundance of Eragrostis plana (species group J) as BREDENKAMP, G.I., JOUBERT. A.F. & BEZUIDENHOUT, H. 1989. A reconnaissance survey of the vegetation of the plains well as a low cover/abundance and constancy of species list in the Potchefstroom - Fochville - Parys area. S. Afr. 1. BOI. ed under species group F (Table 1). 55 : 199 - 206. FULS, E.R. 1992. Evaluating the influence of rainfall effectivity 1.2.2 Panicum coloratum - Acacia karroo Low Thicket on the vegetation trends of semi-arid grasslands. 1. Arid Env. (type releve: 120) (submitted). This is a very distinct plant community which contains con FULS. E.R., BREDENKAMP. G.1 .• VAN ROOYEN, N. & spicuous woody species. This low thicket is encountered in THERON. G.K. I 992a. The physical environment and major low-lying areas where duplex soils are mostly predominant plant communities of the Vredefort - Kroonstad - Lindley - (sandy A-horizon underlain by clayey B-horizon). More Heilbron area, northern Orange Free State. S. Afr. 1. BOI. 58 (in often than not this plant community is the result of bush press). FULS, E.R., BREDENKAMP, G.J. & VAN ROOYEN N. 1992b. encroachment due to severe disturbance and degradation. The plant communities of the rocky outcrops of the northern Not surprisingly, Acacia karroo, a woody shrub or small Orange Free State, South Africa. Vegelalio (in press). tree species known to be a vigorous invader, is the dominant GIBBS RUSSELL, G.E., REID, C., VAN ROOY, J. & SMOOK, woody species of this plant community. Other diagnostic L. 1985. List of species of southern African plants, 2nd edn, woody species, occurring as shrubs or small trees, are Rhus Part 1. Mem. bOI. Surv. S. Afr. 51 : 1 - 152. pyroides and Ziziphus mucronata (species group H - Table GIBBS RUSSELL, G.E., WELMAN, W.G., RETIEF, E., 1). The woody shrub Protasparagus laricinus commonly IMMELMAN, K.L., GERMISHUIZEN, G., PIENAAR, B.1., occurs in association with the larger woody species. Other VAN WYK, M., NICHOLAS, A., DE WET, C., MOGFORD, species encountered as undergrowth include the forbs J.C. & MULVENNA, J. 1987. List of species of southern Afri Tagetes minuta. Bidens pilosa. Rubia horrida and Archyran can plants, 2nd edn, Part 2. Mem. bOI. Surv. S. Afr. 56: 1 - thes aspera (species group H - Table 1). Graminoids found 270. HILL, M.O. 1979. TWINSPAN - a FORlRAN program for in this plant community, which have limited diagnostic arranging multivariate data in an ordered two-way table by value, include Chloris virgata. Sporobolus aJricanus. classification of the individuals and attributes. Cornell Uni Sporobolus Jimbriatus and Pennisetum sphacelatum (species versity, Ithaca, New York. group H - Table 1). Most of the diagnostic species of this KOOU, M.S., BREDENKAMP, GJ. & THERON, G.K. 1990. plant community are indicators of disturbance and/or retro Classification of the vegetation of the B land type in the north gression. western Orange Free State. S. Afr. 1. BOI. 56: 309 - 318. LAND TYPE SURVEY STAFF. 1984. Land types of the maps Concluding remarks 2626 Wesrand, 2726 Kroonstad. Mem. Agric. Nal. Resources All plant communities could be related to specific environ S. Afr. 4: 1 - 441. MENTIS, M.T. & HUNTLEY, B.I. 1982. A description of the mental conditions and are therefore ecologically distinguish Grassland Biome Project. S. Afr. Nal. Sci. Prog. Rep. 62: 1 - able and interpretable. This delineation of the plant com 29. munities and associated habitats of the undulating grasslands MUELLER-DOMBOIS, D. & ELLENBERG, H. 1974. Aims and of the northern Orange Free State should be used as the Methods of Vegetation Ecology. Wiley, New York. basis for future management and conservation of these SCHEEPERS, J.e. 1975. The plant ecology of the Kroonstad and areas. Long-term species and plant community conservation Bethlehem areas of the Highveld Agricultural Region. D.Sc. will only be assured if ecological boundaries are incorpo- dissertation, Univ . of Pretoria.