Vegetation ecology of the southern Free State: 1. Plant communities of the Zastron area

260

S. Ali'. J. Bot. 1999.65(4)260- 269

Vegetation ecology of the southern Free State: 1. Plant communities of the Zastron area P.W. Malan*, H.J.T. Venter and P.J. du Preez Department of Botany and Genetics, University of the Free State, P.O. Box 339, Bloemfontein, 9300 Republic of South Africa Received 26 July 1996: revised 12 Februm:v /1)99

An analysis of the plant communities of the Zastron area (South Africa) is presented The Bra~n-8Ianquet-techn i que, supplemented by TWINS PAN, was used for the phytosociological classification of the vegetation Twenty distinct plant commun ities were recognized and described. An hierarchical classification is presented and each vegetation unit IS related to specific environmental characteristics. A OECORANA ordination IS also presented, showing environmental gradients.

Keywords: Braun-Blanquel vegetation classification , OECORANA ordination, habitat related , southern Free State, TWINSPAN *To whom correspondence should be addressed at P.O.Box 292, Mafikeng , 2745 Republic of South Africa.

Introduction Each plant community may be regarded as an unique entity with its own species composition associated with a specific set of environmental factors. According to Westhoff (1971) the description of plant communities is essential to provide a scientific inventory for conservation and in general for the preservation of biotic diversity. The fact that Acocks' (1988) broad analysis and description of South African vegetation types is one of the most cited botanical publications, indicates the importance and need for such vegetation classifications. The necessity to identify and describe the Grassland and Nama Karoo Biomes was stated by Mentis and Huntley (1982), Scheepers (1986) and Hilton-Taylor (1987). From a phytosociological viewpoint, relatively little is known about the vegetation of the southern Free State and thi s data set and reSUlting classifications provide the basis for a phytosociological synthesis of the vegetation of the southern Free State which is currently under study by the authors. This paper specifically reports on the detailed Braun-Blanquet classification and plant-ecological interpretation of the plant communities of the Zastron area.

Study area The study area covers approximately 1 270 km 2 and is situated between 27°00' and 27°30' E longitude and 30'00' and 30°40' S latitude in the south-eastern part of the southern Free State (Figure 1). The study area lies within the Cymbopogon-Themeda Veld (Veld type 48, Acocks 1953) and within the 600-800 mm rainfall interval (Figure 1). According to Acocks (1988), Karoo invasion is well under way in the Southern Variation of the Cymbopogon-Themeda Veld with patches of Pefllzia gfobosa and Wafafrida saxaJifis, developing on the heavier so il forms along valleys and eroded shaly hillsides. This phenomenon is well illustrated in Table I (species groups V and Z). Geologically the area is characterized by Molteno and Elliot Formations. The uppermost formation, namely the Clarens Formation, forms a prominent cliff on the northern side of Aasvoelberg. Molteno Formation, the first of the Stormberg Group, lies on top of the Beaufort Group. The Elliot Formation follows conformably on the Molteno Formation (Dingle et of. 1983). The topography of the area consists mainly of continuous hills and mountains with moderate and high relief, allowing only stock farming and small-scale crop production.

The Ca and Ib land lypes are the 1110st prominent in the study area (Land Type Survey Staff. III Press). The ea land type qualifies as a plinthic catena (which is rep resented by Hutton-. Bainsvlei-, Avalon- and Longlands soil forms) (Land Type Survey Staff in press). Dolerite outcrops are conspi cuous in the general top ography of the study area. Loose scree, as well as Mispah, Sterkspruit and Val sri vier soil forms are prominent on slop es while Valsrivier. Milkwood and Dundee soil forms are prominent on the low-ly ing plains (Malan et al. 1995). The lb land type accommodates land where exposed rocks cover 60-80% of the soil surface. These rocky portions may be underlain by soil which would have qualified the unit for inclusion in another broad soil pattern would it !lot have been for the surface rockiness . Dundee and Oakl eaf soil- forms are the most common soils within this land type (Land Type Survey Stan: in press). Generally the soils in the Zastron area are referred to as 'Podsolie' (pH < 7) soi ls. T hi s so il s arc generally deeper than 'solonetic ' (pH > 7) and contains a high salt (especially sod ium compounds) content soils and also comprises well-developed horizons. Donga and surface erosion are a common pheno menon of these soils (Potgieter III 0/ J9(5). Altitude ranges from I 350- .1 000 1ll above sea level.

Methods ReJcves were compiled in 76 sample plots. Stratificatioll \'..-as based on topographical position (crest. plateau or slope), aspect and geology. Plot sizes \\ ere fix ed 011 1(l() m: ( I () 111 x I () Ill) (Scheepers 1975). In each sample plot the !lorIstic composition \\ as recorded and a cover-abundance vallie accordilll,! to the 13raun-Blantjuet scal<.; (Braun-Blanque! 19(4) was all ocated to each spec!es. Other em·lronmental variables such as sui l furm. land type. percentage rockiness of the soi l surface and habItat disturbance ,.,.ere also recorded Two-\vay indicator spec ies
S. Arr. J. Bot. 1999,65(4)

261 1 Clif/ortia nitidula-Rhus erosa Major community 2 Stoebe plunlosa-Leucosidea sericea Major commun ity 2.1 Leucosidea sericea--l'hemeda rriandra Community 2.2 Stoebe plumosa- Elionurus 1I11t1;ClIS Commun ity 2.3 Stoebe plumosa-Peucedanllm capense Community 2.4 Clif/orlia paw.:istaminea- Passerina montana Community 2.5 Lellcosidea sericea- Pelargollillll1 alchemilloides Community 2.6 Hyparrhenia hirla- Osyds lanceolata Community 2.6.1 He/ichlysllm ruglilosum-Lellcosidea sericea Sub-community 2.6.2 Rhlls dregeana-Lellcosidea sencea Sub-community 3 Olea europaea- Rhlls Imrchellii Major community 3.1 Euclea crispa subsp. crispo-Rhus dentata Community 3.2 Clutia pulchella -Diospyros /ycio;des Community 3.2.1 Jamesbrittenia atroplIrplirea- Rhlls erosa Sub-community 3.2.2 Rhlls lanceo-Celtis (di'icana Sub-community 3.3 Protasparaglls slI(ll'eolens-Eragrostis /ehmanniana Community 3.3.1 Cymbopogon excOl'allfs-·/J,·o[a,\paragI{s s1/(]veolens Sub-community 3.3.2 Eragrostis clIrvula- 5;1Itera alb{/IOl·a Sub-community 3.3.3 Cheilanlhes eckloniana--Traglls koeledoides Sub-community 3.3.4 Olea ellropaea- A;felianl/!lIs camosus Sub-community 3.3.5 Aloeferox- Rhig(cum abuva/llm Community 3.4.1 Aloeferox- Setaria incrassata Sub-community 3.4.2 Aloe ferO-Y-Olea ellropaea Sub-community 3.5 Rhus ciliata- Olea eltrOpaea Comlllunity 3.6 Euclea crispa subsp. ovala- Olea ell/"Opaea Community

REPUBLIC OF SOUTH AFRICA

.

29"S ,

Pet ru s burg

27°E

• 8locm l 0r11eon

60Q

\

N

"

mm R~r isoytt ,

,

'Nepener _\ FJ uresm,th

Description of the communities STUDY AREA

50

100 km

Figure J The location of the study area in which the plant communities were analyzed. habitats (Venter & Joubert 1985). According to Coates Palgrave (1984) , Eucfea cnspa subsp. crispa has a very widespread distribution, while E. crispa subsp. ovata has a restricted distribution in the southern Free State and extends down to Cradock and Middelburg in the Eastern Cape and \vestwards to Kimberley and Kurllman in the Northern Cape. According to Venter and Joubert (1985), Rhus pyroides subsp. pyroldes is common in open veld, ravine or stream bank scrub throughout the whole of the Free State, except the north~eastern corner. Rhus pyroides subsp. gracilis, however, is restricted to fores t margins and along river banks in the north~eastern corner of the Free State (Venter & Joubert 1985).

Results and Discussion In this study the classification of the vegetation was achieved by way of the floristic~sociological approach with the essential viewpoint that plant communities are units of classification based primarily on species composition (Mueller-Dombois & Ellenberg 1974; Whittaker 1978), The general vegetation of this area can be considered as the Themeda triandra- Olea europaea vegetation unit (species AB & group AC, Table 1). According to Fuis (1993) variations in moisture and microclimate are related to differences in irradiation due to different aspects and gradients. Three major plant communities, of which one (major community 1) is not further divided into distinct communities and sub-communities, have been recognized and are illustrated in the phytosociological table (Table I ). The hierarchical classification of these communities is summarized as follows:

1 Cliffortia nitidula-Rhus erosa Major Community A plant community which was found to be restricted to the moderately steep east-facing footsJopes of the Aasvoelberg Mountain, where Avalon soils are th e most prominent. The Elliot and Molteno Formations are the most important geological formations with the Ca land type covering nearly 80% of the area. These areas are often disturbed by hikers and have a low species diversity (Table I). Species of species group A (Tab le 1) characterize this plant community with ('[{florlja nilidlfla (species group A) the most conspicuous, having high cover~abulldance values. According to Coates Pal grave ( 1984), C l1itidllla can reach six metres in height. However, the average height of C nitidula in this major community did not exceed three metres. The only other conspicuous species present include the woody shrub, Rhus el'osa (species group Z, Tab le I ). R erosa is commonly found in the rocky areas in the southern Free State

2 Stoebe plumosa-Leucosidea sericea Major community This vegetation unit is encountered on the moist, steep southerly facing slopes (30- 60°), where also a higher species diversity is found to be present (Table I ). The diagnostic species are tho se listed in species group J (Table 1). Leucosidca sericca is the only diagnostic tree species being abundant in some areas. The he ight of this tree varies from two to six metres and is widely dispersed in the mountainous areas, especially in kloof forests and 011 mountain slopes in the Free State (Venter & Joubert 1985). The exotic rose, Rosa eglanteria (species group J) has long pendulous branches which are spinose. This species often forms dense impenetrable stands . Passerina montana and Sloebe pllfll10sa (species group J) are the only two other diagnostic species present (Tab le I). Seven distinct vegewtion units were identified within this plant community (Table I).

~

S . Aft.J.BM . 19~.650 )

Table 1

Phytosociological table of the plant communities of the Zastron Area I 1

Pl~nt

oommunity number

3

2

2.,

~I

11 . 1 12 11 2.21 2 . 31 2 . 4 12

3.1 1

.1 I .2

3.2

3 .3

. 1 1 . 21 . 11.2 1. 31

3 . 5 13.6 1

3 .•

. 41

.S

.1

.2 1

1555~ 1 555 1 5555155~51555551555 1 55551555'515 5 55I'55'144414441441333 1 444142544 1 444444 J 444 1 22233 1 613 1

133331G5715755 1555517G7771G6GJ4445144444 1532313333 17S814491S8J999 1oS01 02033 1777777 1G77 1gSSG1 109S 1 123451S301712GIS945 13124!5145617s90126345 111BOIB6971913134614'I189 1291139156 1234678 1g01 179311 1648 1

R.olev6 Number

SPECIES GROUP A clittor~l~ nitldula lUlu. pyrolde. aubjip . gr&0111.

J,ragroati. raoeme •• Gnidia mio:z:ophylla

Linum thunberg11

144331 I~ 111 IAARRI 1,,",,1 I

"'"

II IR 11 1 I

I R

"'"

SPECIES GROUP B &11onuru' m\ltlou.

1 I

1111212

8P&CI&8 GROUP C

Peuaed&nun capena.

1121121

11

"

IR

1l>J,CIIS GROUP D

Cl1ttortia pauet.tAminea

1

1

1533231 111M. I

Oxa11_ corn1culata

RI

81>1:0II.8 GROUP &

Pelarqonlum al.che=illoldea gollohryaum nudJ.tol1um

Rhynohoala nerve •• 8alvia

+ RI

I+M.I 11R I I I ++1

I

"'"

~cron.ta

sPloue GROUP F

Hel10hryaum rugul oaum Hel1ototrichon turgldulum setaria -.phaeelat. &ragroati. nindanala Vernonia c~n.l.

Iragr oatia

c~.l.

Penni •• tum

*ph~latum

J1MilI

1111211

I R

1132 I 12 11 I ~++I I HI 1 I

I

R 1

11 1 1

I I 11 IR

1IR RI

BlIICIZIl GItOUl' CJ

Senecio ia.tldeua

111212+Jt21R1+

8PIC1&' aROUP R 8uthorl andia miorophylla

11 I

Rhua t1roge&n&

Ari.to. oognata aRCUs

QiU)Up

IR I

"" I 1+21111

I

I """'"

I

fri.taohya leucothrlx »1011.... oal0m0lano. 8PlOl&. GROUP

21

I +

I.

llR

"" """

R R+

J

8toel)o plWDO ••

IR

LeuOClaidea .er1oea

1

Pa •••rlna montana Ron eqlantdria

132 11513 11211 I llR!53 I ill 1 IIUUIl IR 112512 2511 5511212 IlRll3 231331221 1 2 I 22 1 22121423112 I 2 I 2 1 I 11 112 211 I I 12 2121 1 1

+1

8PECIZS Gl\OUP K

The.1.um .pec1.e. CU •• onia pan1.cuiata

I +

1

De1oape~ ooope~1.

1111 1 11R I

11

I "" I

I

snClIlS GROUP L Hy~a1.ne lI.t'~icana

Rhu. dClnt ata

Zuo1ea

o~1.apll.

RI I

aUbap. or1.pa

SPletz8 GROUP W Hyparrhenia h1.rta SPZClIl8 GROUP N W.iioa dooumbena J~abritteni& atropurpurea tndigot'er& nig~omont&na

Jl I

"'"I

I R I 1++11

Jl

I 1 I

1

I 1 I

11211 I 3 11 1243121 3231 I R1211 22M. I 1

1R12 1 I

1211111121212 11 1

IR+IHI

''''''''''

I SUU+ I

13423321344 1

IR RI

I

R

R

s. Afr. 1. Bot. Table 1

1999, 65(4)

263

Continued , 1

Plant cOll'Il'lll.lnlty nUlflbor

2

3

11 . 1 12 11 2 . 2 1 2 . 31 2 . 4 12 . 5 1

3. 1 1

2. ' .1 I

3.2

. 1 I . 21 . 1 1 . 21 . 31 . 41

.2

3 . .513 . 61

3.

3 .3

. .5

. 21

.1

1.5.5.5515.55 155.5.51 .5.5.5.5 1.5.5.55.51.5.5.5 1.5.5.5.51.5.5.5.551.555.5155551444144414413331444142544144444414441222331613 1 13333 16.57157.55155.55176777 1666 1444.5144444 153231333311881449[881999108010203317777771677 J95.56110951 12345 183017126189.513124.5 14561789012634.5111 8 01 8697 1913 134 6 14517 89 129113 91.56 123467&1901 17 931116481 8PZOIJ8 GROUP 0

Bud4leja .alviltolla

aPKCUB

OJlOUP

51

Cluti. puloholla

I 31241

,.

AAIR,+1 11 1111

BPECIES aRCUP Q

IU'J\U l ance.

celti.

..,

'"

a!ric~a

•

P.von!" bUl'ohell!!

BPlons

22[11111

[2221 2 12111 11 lJUUtI 1 1+R.1

,

3

2

, 1

1

QROUl' Jt.

Cymbopogon eXolloVOl tua

11221 132 I

1

12

Tarohonanthua oaqphoratus Vi.oum rotunditoll um

1

.,,

''''' , 'IU

Btaohy • .nilI Da.

,""

8cl&go a lblca

Irloaephalua orleola-a

'''''

Prota.,paragua larioinus

1

1 111

.,

8PECII& OROUP S

"

Oayrl. lano&olata Chel lanthc. ooklonlana

1

11 11

I~

I

,11 ,

1111

1211 12111212111111 1 1R 111 31 I R 1 1RJl IR RIR + IR. IIll IJUlllll!

'"

BPiOnS aROUP '1'

Ir.qroatl. ourvula

F. '"

't II,getelI. minuta

Populua oaneaoans Pr\,lnua

,.

,.'"

,

'1'euorlum trltldum

GlWUl'

1

,"'"

l21lU 11 lrutilltl 111

,

• •

V

,

+ +JR.

Hellanthua como.us

Pontzi. 91000_. Ga~anla

kreba!ana I n digotcra alternan.

2' " ,., , 'F.

, "

"

2

11

11 11

"

8PECI.S aROUP W WalaEridA aaxatl11a Prota~aragu. auaVDolona

•

le~nnlana

"

2

85110118 GitOVP X

setaria inoraa.ata baohi. hamata Yibiacna trionWll Heliohry'WIl piloaollua ~rb1na Qblongata

12211

"

SalVia ve.rbenaCia

Ira9roatla

IR+I IHI

.

IPlons OROUP U

'1'raqua koelerlo1daa exalt. depre •••

,

1 11

2

,"'"

,'" ,,""

~ :uloa

Helinia rapens Butera albiflora

sp.Cns

1221 11R.1 I R+I

, ,3

,. ,

11

,

[Rll+ 111111 1 113 11 1 I11RI +R[ 211 11 1112 1222 1 21 I 111 1 I

,, -

• ,. .,, , , , 11

"

,'''''',

'"

1

,

11

2

2

111 1 11 IJUUJU\t 1 In. R.

, 11

,

, IW\'

8PZCIE8 aROUP Y

J 22222213321

Aloe t'erox iU'ligo%um oboVatum

221 1 21R

Grewia oooidentalia

..

8llEen8 GROUP Z

Dioapyroa lyaioide. Velloia t'llit'olia Dio.pyroa au.tro-at'ricana lUlu. ero •• Rha=nu. pr1noide.

112

2 111121

,

2

,

1211121111111 11221211 11 13

111111 1212 12233 14431 2154(22 13231 123 1121111 +11 11112RRlll111 1 I +RR.[ 121 11111121 1111[ 1112211lttl 1 11 1 1111 I 1 121 11+11111" 3 3 [ 41 11211 1224[ 52 2114 13333 1 21 1+112111 1 12 2 132221111 I , 1 , , 1 22 11111 1 112133 1 1112 1 1 lttl

1111 11 1 11 1 [1 1 I

11343 1 3 ,

j,

,

11211

,,"'"-,

''''' ,

,.,.

•,

"'"

, ,

,

,

,

,

1

264

S. Ati·. J. Bot. 1999,65(4)

Table 1

Continued 1 1

Plant oommunity

n~r

1

2

3

11.1 12.11 2 . 21 2 . 3 1 2 . 4 12 51

2.6

3 .1 r

I .1 I . 2

3.2

3.3

I .1 I . 21 . 11 . 2 1 . 31 . 41

3,4

.5 1

.1

I

3.513 6 1

.21

15555155515555 15555 1555551555 155551555551555515555 14441444144 13331444142544144444414441222331613 1 13333[6571575515555 1761771666144451444441532313333 1788[449188 19991080 1020331771717167719556110951 12345J83 0 171261694513124514561789012634511180186971913[34614517891291139156 123467819011793111648 1 spzCt:ts GROUP AA

Rhu. o1111lta

1

+

121

1

Zuphorbl& maurltllnlea sp~cnB

IR 1

I

GROUP 1
Ole.. ouropae.a lIub.p. a!ricana

RIl l

SU\UI burchelli1

It I

lucle... orllp", lublp . ovat-.

1 1 1 1231 1 1131223 12 311121222 1 1 122232 121 211211132322 11 221 1 t 2 11 2211222 111 I 11222 12 213 323 11R2 11 11 1 122 I 1111 121 1 1 1 1 i1 2 11 11 1 RI332 ( I I ~

[

Heteropogon eontortu.

11 R2 1

Arl.tlda dittuu.

JR

Ari.tlda oongesta

1

sp:r;cue

1243321

1

I

11 I 1

1 1 2

I

i1

1 1 Rl. 131 1 12 21 1 12 2221 1121 1211 1 1 1 1 1 1 1 I~ 1 112

l 1H 211 1 13

22 1 1

1

~ 11 1 1 22 2112 1 11 11411Rl.

GROUP At!

'l'hemeda trlandr ...

I RR 132412122 1 123 12

12 133212233 1111

2.1 Leucosidea sericea-Themeda triandra Community The Leucosidea sericea- Themeda triandra Communi ty is encountered on the virtually undisturbed moist, steep (30-60°) slopes, fac ing south-south-east to south-south-west. Large dolerite and sandstone boulders occur and cover 40--60% of the soil surface. In the absence of diagnostic species, Themeda triandra (species group AC, Tab le 1) has a high constan cy and canopy cover. Other species present incl ude Stoebe p/llmosa, Passerina monlana, Leucosidea sericea, Rosa eglanteria (species group J), Rhlls erosa and Rhamnlls prinoides (species group Z). According to Coates Pal grave (1984), L. sericea can reach up to seven metres in height and usually occurs at high altitudes along stream s and in ravines , as was also the case in this instance. In KwaZulu-Natal, Lellcosidea is troublesome as it invades overgrazed and disturbed areas, forming impenetrable thi ckets which me best erad icated by chopping plants down to the ground. In mountainous areas the presence of these trees is taken as an indicati on that the streams are suitable for trout-stocking (Coates Palgrave 1984). 2.2 Stoebe plumosa-Elionurus muticus Community This plant comm unity is associated with open shrubland at the feet of southerly facing hill s. Th is vegetation unit thrives in full sun . Large uneven and rough rock plates occur and cover 50% of the soil surface. The grass species, Elionurus muticus (species group B), is the only differentiating species present (Table I). According to Van Olldtshoon ( 199 I) this species is well adapted to rocky habitats. Patches are severely utilized and disturbed, especially by the rock dassie (Procavia capens;s). Fuls (1993) also reports patch-like over-utilization by rock dassies, especially on southerly facing slopes of the low thicket commu nities of rocky outcrops in the northern Free State. The forb Stoebe pJumosa (species group J) is indicative of disturbed areas. Themeda Iriandra (species group AC) is the only dominanl grass species (Table I). 2.3 Stoebe plumosa-Peucedanum capense Community This plant community is restricted to the feet of cool south-facing slopes. Alt hough do lerite may be present, these slopes consist predominantly of sandsto ne ledges. Fine gravel may be present, but the so il is primarily clayish, especially in the

12111 11

1 1 1111 12331 1 133

I 22232112 I 33211231

lower-ly ing local ities. Like the Stoebe pI1l11l0Sa- £1i0l1llrlls mlllicils Comm unity of the Sloebe pllln1osa- Lew.:osidea sericea Major Co mmunity, no diagnostic woody species occur. Peucedaullm capense (speci es group C) differentiates this community (Table I). Of note is the local ly high cover-abundance of Lr!lU.:osidea sericea and the absence of the thorny. exotic rose, Rosa eg/anteria (s pecies group J). Other important woody species are Diospyros Iycioides, D auslro-alricana. Rhus erosa and Rhamnus prinoides (species group Z). Accord ing to Coates Pal grave (1984), a decoction of the decorticated root of R. prinoides is taken as a blood purifier and to treat pneumonia. Parts of this plant are widely favou red as a protective charm which is used against lightning, to protect homes and to safeguard the courts of Basuthll ch iefs (Coates Palgrave 1984).

2.4 Cliffortia paucistaminea-Passerina montana Community This plant community is encountered at the feet of south to southwest facing slopes. Rocks and pieces of fine gravel are visible on the soil surface. Large sandstone boulders occur at these foots lopes. Apart from ('Itrforlia pmrdslalllinea (species group D) and Passer;no montana (species group J), this plant community does not have a dominan t or co nspicuous woody co mponent. The small forb species. Om/is cOl'l1iculata (species group D), together with C. pallcisremlllea, are the only two diagnostic species with the latter having a notably high cove rabundance (Table t ). Leucosidea sericea (spec ies group J) has a relatively low cover-abundance and is, together with Rhus erosa (species group Z), the on ly woody species present (Table I). 2.5 Leucosidea sericea- Pelargonium alchemilloides Community This plant community is restricted to the lower altitudes of moist plateaux of dolerite hills. Flat slabs of rock are prominent and cover 60--70% of the so il surface. Diagnostic tree species are absent with only the species of species group E characterizing thi s vegetation unit (Table I). Leltcosidea sericea, Passerina montana (spec ies group J). Myrsine alrieana. Rhus denlata. £lIch~a crijpa subsp. crispo (spec ies group L), Osyris lanceolala (spec ies group S), Fe/icia fi/[folia,

s. Afr. J.

Bot. 1999,65(4)

Diospyros llI/slro·(~fricalla. Rhus erosa and Rhamnlls prinoides (spec ies group Z) are the only shru bs present, all with a maximum height not exceed ing two metres - probably due to the rockiness of the subst ratum.

2.6 Hyparrhenia hirta-Osyris lanceolata Community Thi s pl ant community is mainly associated with moi st and coo l south-facing slopes of the Aasvoelberg Mountain near Zastron. The slo pes are often clifflike. The presence of the grass, Hyparrhenia hiNa (species group M), the most widespread of all the hyparrhenias (Gibbs Russell el at 1990), together with the species from species group J, differentiate th is vegetation unit (Table I). H. hirla. common ly known as 'de ktamboekiegras' is a perennial, rhizomatous grass which grows we Jl ill stony soils (Gibbs Russell el al. 1990). The vegetation is o ften dense with Leucosidea serkea (s pecies group J) often exceeding four metres in height. The tree, o.\yris lanceolata (species g roup S), the exotic rose, Rosa eglanleria (species group J), and the shrub, Rhus erosa (species group Z), are th e onl y ot her wide ly distributed woody species. Two di stinct sub-com munities were identified (Tab le 1). 2.6.1 Helichrysum rugulosum-Leucosidea sericea Sub-community This very limited plant community was encountered on fo otslopes of southerly facing hills. The area is rocky and large sandstone bou lders (> :2 m in diameter) cover 60- 70% of the soi l surface . This is an important thoroughfare for hikers and thus resulted in th e degradation of the vegetation due to trampling. The diagnostic species are listed in species group F (Table I ) lfeli,'hlySW11 rugztloslll11 and the grasses Heliclotricholl IIIrgiduIUI1I. Se/ada sphacelalo and Eragroslis nindensis are the mos t widely di stributed among these species. Lellcosidea sericea, Rosa eglonleria (species gro up J), Osyris lanceolala (species group S) and Rhus el'osa (species group Z) are the most abundant woody species with Hyparrhen;a hiTla (s pecies group M) and The met/a Il'ial1dl'a (species group AC) the grasses with the highest covel'abundance (Table J ). Themeda triafldra has a higher cove r- abundan ce in this vegetation unit than in the Rhus dregr!(Il1o- Lelicosidea sericea Sub-community (Tabl e I). 2.6.2 Rhus dregeana-Leucosidea sericea Sub-community Thi s sub-community is associated with the moi st and coo l south-fac ing slopes. These slopes predominantly consi st of sandstone ledges, often being cliff-like. The slopes are moist and cool due to th e shading by the cliffs. The vegetation is dense and the rocky slabs co vering 60-70% of the soil surface give th e area a rocky appearance. This moist shrub land is typical of the mountainous areas of th e eas tern Free Stat s, Lesotho, Natal and eastern Cape and has been desc ribed by se veral botanists (Bews 1917; West 1951; Story 1952; Kill ick 1959, 1963; Roberts 1966; Edwards 1967 & Du Preez 1991). According to Roberts ( 1966), the Lellcasidea sericea- Myrsine nfricana forest of Thaba 'Nch u Mountain is more cl osely related to the mesophytic bush and moist forest co mmuniti es o f the eas tern Cape, as described by Story (1952), than to the shrublands of th e Natal Midlands, as reported by Killick (1959, 1963 ). Du Preez ( 199 I ) stated that the Lellcasidea .l"ericea- Bliddleja saligl/o moist shrubland of Korannaberg occurs on sites where co nditions are too harsh for the devel opment of ravine forest or in places where destruction of forest took place. Speci~s of species group H (Table I) characterize thi s vegetati on unit with Rhus dregeana the only diagnostic woody species prese nt. The only other diagnostic species present, is Aristea t.:ognara. The grass Trislachya leucothrix and the small fern ,

265

Pel/aea calome/ol/os (s pecies g roup I ) are evident. especially between the rock slabs. Only a few oth er woody species occur with Lellcosidea seJ'icea (species group J ). Uhll.\· dentala. Euclea crispa subsp. crispa, J'Iyrsine aj/'/(:alla (species group L), Buddleja sa/vii/alia (species group 0). o.\yris lanceolala (species group S), Diospyros ~}'cioides and R/WI11IllIJ prinoides (species group Z) being the most important (Table I). Species of species groups Land 0 are prominent within th is vegetation unit. but are absent within the He/ichlyswn I'Ifgulosum- Leucosidea sericea Sub-community. The latter also lacks Rhamnus prinoides (species group Z) whi ch is prominent within this vegetation unit (Table I).

3 Olea europaea-Rhus burchellii Major Community This open woodland major com munity is associ ated with the ravines as wel l as mo ist sou th - and sout h-east facing slopes of hills. The habitat condi tions here are drier than in the previous two major communities (majo r com munities 1and 2). The soil surface is rocky and of dolerit ic origi n. Species of species group AB (Tab le I) are diagnostic. Olea europaea subsp. africal1a and /
3.1 Euclea crispa subsp . crispa-Rhus denlala Community This shrubland is restricted to the rocky ravines at the foot of south-facing slopes. Stones and fine grave l from upslope occllr on the soil surface . This is a inconspi cuolls vegetation unit with onl y a few diagnostic species, Thesium sp, Delosperma coope"; and Cussonia pankulata (species grou p K) are the diagnostics of thi s community, all having low coverabundance va lues (Table I). Myrsille ajricana, Rhus denlata. Euclea crispo subsp. crispa (Species group L), Buddleja salvi{(olia (spec ies group 0), o',yris lanceolata (species group S), Rhigozuln ObOl'011I1l1, GrelVia occidenlalis (species group Y), Dimpyros /ycioides, D. ollslro-africana, Rhus erosa (species group Z), R. bUl'chel/;i and Olea europaea subsp. africana (species group AB) are the 1110st abundant woody species present. Among the grall1in oid s Hypal'l'henia hirta (species group M) and Themeda triandra (species group AC) are the most abundant (Table I ). 3.2 Clutia pulchella-Diospyros Iycioides Community A shrubland community si tuated at low alt itude on south-facing h ills. The soil is poorly drai ned and do leri te roc k sheets cove r large areas (50-70%) of the soi l surface. Pieces of fin e sandsto ne gravel erod ing from ups lope are com mon. Clulia pulchella (species group P) differe ntiates this plant com munity . According to Coates Pal grave ( 1984), C pulchella occurs over a wide range of alt itud es and in a va riety of habitats, from karroid scrub to evergreen forests. Venter and Joubert (1985), however, emphasized th at thi s species com monly occurs in shady ravines and below large trees. Th is was mainly the case here, as Clulia pu/chella grows well in the shade of especially Diospyros Iycioides (species group Z) and Rhus lancea (species group Q). Species of species groups B, C, G, H, I, R and X are absent from this community Crab le 1) . Species of species groups 5, Z, AS and AC (Table 1) are widespread with Osyris lam;eolala (species group 5), Diospyros austro-a!ricana. D. Iycioides. Rhus eroso (spec ies group Z), Rhus hUl'chellii. Olea ellropaea

266 subsp. africana (species group AS) the most important woody species and Arislida diffusa (spec ies group AB) the on ly consp icuous grass , The sma ll fern . Cheilanthes eckloniana (s pecies group S), grows especially well in the cracks between rock sheets, but is inconspicuous here. This vegetation unit is further subdivided into two distinct subcommunities (Table I).

3.2.1 Jamesbrittenia atropurpurea-Rhus erosa Sub-community This sub-community occurs in low altitude areas on south-facing hills and along streambeds where a sandy deposit often overlies the rock sheets. No loose scree is visible and the so il is of a clayish nature. This sub-community is characterised by the species listed in group N (Tab le I). Besides these diagnostic species, all of which have low cover-abundance values, Diospyros Jycioides and especially Rhus erosa have high cover·abundance values (species group Z, Table I). It further differs from the Euclea crispo subsp. crispo-Rhus dentaia Community in the presence of Cliffortia nilidula and Rhus pyroides subsp. gracilis (species group A), as well as the higher cover·abundance of, Diospyros auslro-africana, D. Iycioides Rhus erosa (species group Z) and Rhus burchellii (species group AB), and the absence of the grass, Hyparrhenia hirla (species group M). Besides Themeda lriandra (species group AC) with a low constancy, Aris/ida diffusa (species group AS) is the only other graminoid with a high constancy and cover-abundance values (Table 1). 3.2 .2 Rhus lancea-Celtis africana SUb-community This vegetat ion unit is situated at low altitudes and is restricted to drainage channels at the foot,lopes of south-facing hills. Gravel and sandstone stones occur on the soil surface. Species of species group Q differentiate this community with Rhus lancea and Celtis africana the only two diagnostic woody species. 8uddleja salviifolia (species group 0) and Rhus erosa (species group Z) are absent within th is vegetation unit (Table I). Diospyros lycioides (species group Z), Rhus burchellii and Olea ellropaea subsp. a/ricana (species group AB) are among the other conspicuous woody species. Diospyros Iycioides, especially, is very abundant and Rhamnus prinoides (species group Z) and Euclea crispa subsp. ovala (species group AB), though inconspicuous, are also present (Table I). 3.3 Protasperagus suaveolens-Eragrostis lehmanniana Community This plant community is associated with moist habitat cond itions at the mid slopes of south-facing slopes. Habitat disturbance is a more common phenomenon than in the Clulia pulchella- Diospyros Iycioides Community. Aboout 500/0-60% of the soil su rface is cove red with dolerite and sandstones stones. Walafrida saxalilis, Protasparagus suaveolens and Eragrostis lehmanniana (species group W) are the diagnostic species of this vegetation unit (Table 1). Also conspicuous are Diospyros Iycioides, Rhus erosa (species group Z), R. bllrchellii and Olea ellropaea subsp. africana (species group AB) , none of which are higher than two metres. This co mmunity can be subdivided into five sub-communities (Tab le I). 3.3.1 Cymbopogon excavatus-Protasparagus suaveolens Sub-community This plant com munity occurs on low altitudes of the midslopes. especially along the disturbed, moist rocky areas of low south~facing hills. Due to the rockiness of the soil surface,

s.

Ali". 1. Bot. 1999.65(4)

especially in the lower-l ying areas. standing water is visib le for weeks after good rains. Species listed in species group R characterize thi s vegetation unit (Table I) of which (he grass. (vmhopogon exc:aI'aIIlS, and the shrub , Tarchol1rmthlls camphoraflls, have the highest cover-abundance va lues (Table I). C excavalus , coml11only known as Broad-leaved Turpent ine Grass is highl y unpalatable to livestock due to the turpentine sme ll of its leaves (Van Dudtshoorn 1991). The semi-parasite 1';sculIl ro{und{folilll11 (species group R) is virtually restricted to TarcllOllunthlis campharalus According to Coates Palgravs (1984), sp linters of r call1phoraIus are poisonous. causing septic sores which are difficult to heal. It provides good fuel , burning even when green. Zulu women use the leaves to perfume their hair (Coates Palgrave 1984).

3.3.2 Eragrostis curvula-Sutera albiflora Sub-community This plant commu nity has a restricted distribution and is present on th e midslopes of the so uth~facing slopes of low hills. The soil surface is rocky and the vegetation is often disturbed, mostly by local farming practices (cattle and sheep). The characteristic species are listed in species group T (Table 1) with Erngrosfis ClI/Tutu th e only species with a noteworthy occurrence. The tree, Diospyros Iycioid(!.~· (species group Z), is conspicuolls and completely do mi nates the vegetation (Tab le I) . 3.3.3 Cheilanthes eckloniana-Tragus koelerioides Sub-community A community restricted to the midslopes of south-facing hills with an abundance of dolerite and sandstone rocks ( > 2 111 in diameter) . The habitat is mo re disturbed than the habitat associated with Erogroslis clirvulo- SlIlera albifloro Sub-community. Tragus koelerioides, a common grass species in disturbed and overgrazed areas and the forb Oxalis depressa (species group U) are restricted to the shady patches between big dolerite and sandstone boulders. The woody component is inconsp icuous and onl y the trees, Diospyros Iycioides (species group Z). and Olea I!uropaea subsp. a/ricana (species group AB), as well as the shrubs. Rhus erosa and Diospyros ollstfO-t?/i-icr1f1o (species group Z) and R. burchellii (species group AB) occur. Besides Tragus koe!erioides, Themeda triandra (species group AC) and Heleropogoll contorlllS (species group AB) are the only notewort hy graminoids present (Table I). 3.3.4 Olea europaea-Melianthus comosus Sub-community This is a very local and limited plant community occurring 011 moist clayish soil of the midslopes. Big rocks are co mmo n. but no gravel or stones occur on the soil surface. Melirmthus com()SIlS is the most conspic uous among [lie five differentiating species (species group V. Table 1). Diospyros Iycioides (species group Z) is the Illost abundant tree species. Th is vegetat ion unit differs marked ly from the Cheilanthes eckloniollaTragus koelerioides Sub-commu nity in the presence of Eragro.Y1is lehmannial10 (species group W). the stronger presence of Diospyros Iycioides (species group Z) and the low cover-abundance values of Olea europaea subsp. aji'icoJ1u (species group AB) and Themeda triandra (species group AC, Table 1). 3.3.5 Olea europaea-Walafrida saxatilis Sub-community This vegetation unit is very limited. occurr ing only locally at very disturbed patches of the midslopes of south-facing hills, south-west of Wepener. This sub-comJllunity is not characterized by any diagnost ic species group (T3ble I ). Rims bllrchellii and Olea ellropaea subsp. t?fricana (species group AB) are the on ly two conspicuous woody species present. Grasses are scarce and are restricted to Eragrnslis lellllWlllli(ll1o (species group W).

S. Arr. J. Bot. 1999,65(4)

267

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Figure 2 /\ DCA (DECORANA) ordination of the major plant communities of the Zastron Area. a: CiijJorlia nilldula- Rhlls erosa Major community. b: Stoehe pllllnosQ- Leucosidea sericea Major community. c: Olea ellropaea- Rhus bllrchellii Major community.

Aristida di[fl/sa (species group AB) and Themeda triandra (species group AC, Table 1).

3.4 Aloe ferox-Rhigozum obovatum Community TheAloeJerox-Rhigozul1I obovatum Comm un ity is fou nd on the moist upland crests of steep (30--60°) so uth- and south-east facing slopes in the south-eastern parts of the study area near the former Transkei border. The vegetation of these dolerite hills is virtually undisturbed. However, patches of overgrazing, pa rticularly by rock dass ies (Procavia capensis) occu r. Aloeferox (s pecies group Y) is the only exclusive ly diagnostic species present with the shrubs, Rhigozum obovatum and GrelVia occidelllalis, also evident (species group Y, Table 1) . According to Bornman an d Hardy ( 1971 ) A.ferox is distributed over a range of 1 000 kilometres from Swell endam in the Western Cape to the sout hern parts of Lesot ho and varies considerably in its differe nt localities. These aloe plants grow singly or in dense groups and have tall stems up to 3 metres high (Bornman & Hardy 1971). The present authors endorse their observations. Other widely distributed woody species, besides R. obovatum and G. occidentalis, incl ude the shrubs Felicia fili/olia and Diospyros alls/ro-ajricana (species group Z). The trees, Diospyros /ycioides (species group Z), Olea europaea subsp. a/ricana (species group AB) and the shrubs, Rhus erosa (species group Z) and R. burchellii (species group AB) are inconspicuous. Hyparrhenia hirta (species grou p M) and Themeda Ir;andra (species gro up AC) are the abundant g rasses (Table 1). This vegetation unit shows affinities with the Hyparrhenia hirta-Osyris lanceo/ala Commun ity and Euclea crispa subsp. crispa-Rhus dentata

Community by the presence of Hypa,.,.hellia hirta (species group M, Table I). Two distinct units further divide thi s com munity (Tab le 1).

3.4 .1 Aloe ferox-Setaria incrassata Sub-community The A/oe !erox-Setaria incl'(Jssara Su b- com munity occurs in we ll-drained areas with big sandstone rocks covering 40-60% of the surface. The aspect is mainly south-east. Overgrazing of the vegetati on, especiall y by the rock dassie is common . The differentia l species are listed in species group X of whi ch Setaria incrassata and Rlischia hamata are the most abu ndant. Rhus erosa (species group Z) is the most conspicuous woody species with Themeda t";andra (species group AC), Heleropogon contortus (species group AS) and espec ially Hyparrhenia hirta (species group M) the most prominent grasses (Table 1). 3.4 .2 Aloe ferox-Olea europaea Sub-community This vegetati on unit occurs on the well-drained areas of south-facing slopes of hills. The habitat is drier than that of the Aloe/erox-Setaria il1crassatn Sub-community. This sub-com mun ity further differs fro m the Aloe leroxSelaria incrassata Sub-commu nity in the absence of diagnostic species, the absence of Diospyl'os Iycioides (species group Z) and Euclea crispa subsp. ovalO (species group AS), the higher cover-abundance of ffyparrhenia hil"fn (species group IV!) and Aloe /erox (s pecies group V), as well as the lowe r cove r-abundances of the shrub Rhwf erosa (species group Z) and dIe grasses, Heteropogon conto,.tus (species group AS ) and Themeda triandra (species group AC. Tab le I).

s.

268

3.5 Rhus ciliata-Olea europaea Community The fUllts ciliaJa - Oh:l1 eltl'opaea Commun ity is strongly associated wi th the d rier hi ll s and ri dges of the study area between Wepencr il nd Zastroll. The aspects arc mostly south to south-east

on iso lated dolerite hi lls and ridges. The Ca land type is th e most important a nd in dicates land that qualifies as a pl inthic catena

\V ith Hutton-, Bainsvlei-. Avalon- and Longland s soils being the most prominent (Land Type Survey Staff, in press), The Rhlls ciliata- Olea ellropaea Community is limited in distribution nn tl s ize and has only two differentiating species, Rhus cilia /a and f:..'lfphorb ia maurilanica, of which only R. "iliola is ab undant (spec ies group AA). Olea europaea (species gro up AS) is the on ly consp icuous tree species with Arisada c(JIIgesta, .1 diflit.w (species group AS) and Themeda lrialldra (s pecies group AC) the most prominent grasses (Tab le I ).

3.6 Euclea crispa subsp. ovata-Olea europaea Community Like th e IUIUS cilia/a- Olea europaell Commu nity, this vegetation uili t is also restricted to the dr ier hills and rid ges of the study areCl. T he aspect is south to south-east. The Fb land type is mos t pro m inent and indi cates land where li me regularly occurs in th e so il . G lenrosa , Mispah and Oak leaf soils are the most abund ant ( Lan d Type Survey Staff, in press). T hi s is also a vcry limi ted vegetation unit with only a few species present. Diagnos tic species are absent. Euclea cri,'pa subsp. om/a is the on ly shrub present in abundance (species g roup AS, Tab le 1). This plant communi ty also lacks species of species gro up AA (Table I ) which characterise the RIms r.:ilia/(l- Olea ellrupoea Communi ty. The shrubs Rhus hurchellii and EIIc:Iea cr;.\·{)(1 subsp . ()I'ora (species g roup AS) are the on ly other abu ndant woody representatives (T able I).

Ordination In the scatter d iagram (F igure 2) the distributi on o f the releves a lo ng the first and seco nd ax es of the DECORANA o rd ination is give n. The di stributi on of the different plant com m uni ti es and su b-commu ni t ies o n th e diag ram were not cl ea r. It was thus decided to only include differences between the different plant maj or com munitie s. Major communities associated w ith ravi nes in relatively wet conditions on Elliot Formations are situa ted to the right of the di agram and relatively dry open woodland vegetati on on Molteno Sandstone to the left (axis I). A long the sec ond axi s., the plant communi ties with re latively low species diversity arc si tuated at the bottom of the diagram, while the plant communities with higher species diversity are situated towards the to p (Figu re 2).

Ali·. J . Bo t. 1999.65(4)

occu pied by sub-surhlCc rocks. re~ul t s in deeper rai nfall mfiltratiOll , favour ing spec ies with a £aproot sys telli . Equa lly importalH may be the protecti on of seedl ings and yo ung plants by the rocks. from frost and fi re ( Fuls 19(3). T he most important woody spec ies ellt:olll\tered incl ude !J1ll1dleja sal\'i~fofi(/. Diospyros mt.\·lro -(~!i·/(:a lla, j) ~vcio;dcs, I:'uc/eo crispa subsp. Ol"(lta, FeliCIa !ili/olio, (in'1I'ia occidel11alis. I.elfcosideo sericea, Olea eurolwea subsp. a/Nclllla, (hyris Imu:eolata, Rhamnus prino;des. Rhlls hl/rcll/!Ihi. R erosa and the exotic rose Rosa eglonre";a ( '/ieilalllhes /!cklollhll1(1 is the most important fern and grows espccially well in l.:n:vices betwecn rocks as well as all the plateau x. Abundant grasses are restr icted to .·Ins/ida d{(fllsa . ..1. congesta. 1-Ic!lel"()JI()gcllI coI1fO/"(lIS. ! ~l'j){II.,.hellia hirta and Themelio (r;mull'fl Lellcosidea sericea and Huddle/II sullglla are also abundant in the mo ist shrubland and forest co llll11 unities of Korann abcrg descr ibed by Du Preez ( 199 I ). Accord ing to Du Preez ( 1991). a geo logical fe allJrc thm plays all important role in thc surviva l o rth e Afro- lil o ntane forest commun ities, is the narrow ravi nes wherc do ler ite dykes cu t through the C lare ns Formation at the edge of the cli ffs. During rhe intrusio n phase (Jurass ic Period ). hot igneous mat erial penetratcd th e sandsto ne and baked it to hard so lid rock. w hi ch is res istant to weat hering. The ravincs deve loptd by the subsequcnt more rapid weathering of the dolerite dykts (Du Preez 1(9 1). Yellow, apedal, well-drained, o ligotrophi c soils are restricted to the plateaux. Lithoso ls are found lll a inl y on the talus slopes (Du Preez 1991 ). Roberts (1966) menti ons AIl'o-montanc fynbos comlll un ities from T haba'Nchu mountain, but his c lass ifi cation is derived from an association analysi s. wh ich is not com parable to a Braun-Blanquet classificatioll. The presented delineati on of the plant com m unit ies and associated habitats should be used as th e bas is tor future managemen t and conse rvation of th ese areas. Althoug h the dist ri bution of these plan t co mm unit ies is restr icted to the sout h-eastern corner of the sou th ern Free State. there are disti nct si m ilarit ies and diffe rences between these species and com mu niti es rllld those pla nt t.:ollllllu nities encountered in th e drier part of the southern Free State (M alan el (1/. 19(5) . Due to the vulnerability of the vegetation in this area, special care should be taken to protect it from destruction by fi re . habitat di sturbance by hikers. especia ll y all the Aasvoe lberg Mounta in. and the collection of firewood . T his shrubland vegetatio n is of great importance for the conservation of wildlife. Bes ides the providing of shelter for num ero us mammals and bird species. it also hosts important nesting s ites for the endangered Cape Vulture (Gyps coprolheres).

Discussion The a im of this st ud y was to iden ti fy, characterise and eco logicall y inte rpret the plan t commu nities of the Zastro n area in the !;oll thern Free S tate. A ltho ugh the Olea /!l//"ofJaea-RlllIs burchellii Major Comm unity (major cO lllmunity 3) are generally regarded as dry shrubland ( Mal an 1992; Malan e l 01 1995), these vegetati o n uni ts a lso occ ur within the GOO- 800 mill rainfall inte rva l and are thus included in thi s manu script. The study area offers a wide variety of habitats and microcJ imates in a limited area. All vegetation units in thi s study can be related to specifi c environmenta l conditions and can, therefore, be ecologically di stinguished and interpreted. The strong presence of woody species on many rocky outcrops in th e clima ti c climax Grassland Biome is ascribed to the shelter and favourab le m o isture regimes associated with high percen tages of sur face and sub-surface rock . Rainfa ll accu mul ation between roc ks, co ncomitant with the vo lum e of the so il pro fil e

References ACOC KS. J.P.H. 1<)53 Vdd types of SOllt h AIi·ica. Melli hoI .'·11/"1' S. Aft.. 28: t- I n . ACOC KS. J. P.H. 19Xt{. Veld tYIlt's n t" S{)l1th Afril:
.S. Afi-. J. Bot. 1999,65(4) Sllllth-~asiern Orange Free State and related areas with special reference to Korannabcrg. Unpu blished Ph. D. dissertation. Universi ty of the Orange Free Slale. Bloemfontein . EDWARDS. D. 1%7. A plant ecological survey of the Tugel a River Bas in. Natal. Mem. bOI. Surv. S. Afr. 36: 1- 285 . PUt S. E.R. 1993. Vegetation eco logy o fl he nort hern Orange Free State. Unpubl ished Ph .D. d issertation. Un ivers ity of Pretori a. Pretoria.

GIBBS RUSSELL. G.E.. WATSON, L.. KOEKEMOER. M.. SMOOK, L.. BARKER. N.I' .. ANDE RSON. H.M. & DALLW1TZ, MJ. 1990. Grasses ofsollth ern Africa. Mem hot. SUI'V S Afr. 58: 1-437.

269 MENTIS_ M.T. & HUNTL EY, BJ. 1982. A d~scriptioll ortlle Grassland B iome Rroject. S Air. nat. Sr:i. Prog Rep. 62: 1- 129.

MUELLER-DOMBOIS, D. & ELLEN BERG, II. 1974. Aims and Meth· ods o.- Vegetation Ecolog). Wiley, New York .

POTGIETER, PJ . (ED.), LE ROUX. PAL .. VAN BILJON. JJ .. VAN DER RYST. c.. KlUG E, S. & I'RETO RllIS, T. 1995. Regional overv iew study or til!! Free State. COllllnissllmed by the Land and Agricu ltural Policy Centre. Bloem fon tein. ROBERTS, B.R. 1966. The ecology of T haba'Nchll. A statistical study

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