S. Afr. J. Bot. 1998,64(1) 1- 17 Vegetation ecology of the southern Free State: Shrubland communities of the rocky outcrops P.W. Malan " H.J-T. Venter and P.J. du Preez p.o. Box 292, Mafikeng, 2745 Republic of South Africa Received 20 Fehruary f 997; revised 28 Juzv /9!r A phytosociologica[ analysis of the vegetation of the rocky outcrops of the southern Free State is presented. Releves were compiled in 185 stratified random sample plots. A TWINSPAN classification, refined by Braun-Blanquet procedures, resulted in 35 plant communities. All these communities have ecological similarities and diffe rences as pomted out by the DCA ordination. The described communities serve as a basis for their spatial distribution in this area as well as for determining their conservation status in the face of increasing development and agricultu re. Keywords: 8rau n~Blanquet vegetation classification, DECORANA ordination, habitat re la ted, rocky outcrops, southern Free State, TWIN SPAN . • To whom correspondence should be addressed. Introduction Methods The Grassland Biome in South Afri ca is under heavy pressure Releves wen:: compiled in 185 stratilicd random sample plots. Sur­ from several different forms of man induced activities (Du Preez veys v,·ere do ne during the summer and late summer of 1993 and 1991 ). To enable optimal resource ut il ization and conservation, a 1994. Stratification was hased on rainfall, topographical po ~i tion vegetation classification program has been implemented in the (slope. crest and plateau). soi l form and geology. No care was taken Gras sland Biome (Mentis & Huntley 1982; Scheepers 1987). to place sample plots in st:!vere ly degraded areas. Plot sizes were 2 This survey was planned to provide data for the synecological fixed at 100 m (Scheepcrs 1975). In each sample plot a list of all syn th es is of the Grassland Bi ome Project (Scheepers 1987). species present was compiled and the cover-abundance of each spe­ Attempts to conserve biotic diversity are pointless and impos­ cies noted llsing the Braun-Blanquct scale (M ueller Dombois & Ellenberg 1974). T!L'\a names conform to those of Arnold lind De si bl e if the entities contributing to diversity are not known. Plant Wet ( 1993). No dist inctions we re made between different subspecies cOll1mun ities are conceived as individual, recognizable entities except for Euclea crispo sl1hsp. crisp!1 and Elle/ea crispa subsp. (C'oetzee el al. 1993) and are characterised by thei r fl ori st ic com­ ovalo. According to Vcnkr and Jouhert (1985) the In ttcr is mainly pos ition (Whiuaker 1978). Because the natural vegetation of the distributed through th e dr ier ridge vdd of the sou thern Free State. rocky Ol1tcrops in the southern f ree State is clearly adversely while Euclea crispo suhsp. crispo IS common to abundant in the aftected by past and existing farm ing practices as well as contin ­ kloof forests and rocky habitats in the moist areas in the southern uous urban development (Furs 1993), a detailed study of these Free State. This is con ll nned by Malan et 01. (S ubmitted). Euclea areas is long overdue. crispo subsp. ovata is referred to as Euclea crispa whi le Olea eIlro~ The main objecti ve of thi s study was, therefore, to classify, paea subsp. ajricana is referred to as Olea ellropaea in the text. All describe and ecologically interpret the shrubland communities of the reference spec imens are hOllsed at the Gt:o Potts Herbariu m at the rocky outcrops in the southern Free State. These data should the University of the Orange Free Swte. Other relevant information be of importance for ecologicall y sound resource management, such as habitat disturbance. degradation of the vegetation, rockiness planning as well as for the identification of possible conservation of the soi l surface and hum an impact 011 the habitat were also noted. areas, especially in the urban areas. Soi l depth was determined by driving a marked steel pin as deep as possible into the soi l. Two~way indicator species ana lysis (TWINS PAN) (Hill 1979a) Study A rea was applied to the Iloristic data set in order to derive a first approxi­ The area studied is si tuated in the southern Free State west of th e mat ion of the vegetat ion types of the area. Refinement was dOll e by 60()-ROO Illlll rainfall interval and is bounded by 24° 20' and 27" means ofBr au n~Bl anquet procedures (I3reden kamp et at. 1989). The 00' E longitude and 29° 00' and 30° 50' S latitude. Plant commu­ nities east of the 600-800 mm rainfall interval are discussed else­ where (Malan ef at. Submitted). Towns situated in the study area are (from north to south) Bloemfontein, Petrusburg, Fauresmith, - 29·S Wepener, Zastron and Bethu lie (Figure 1). In this area, wetlands r-:::...,e...g. 17 '. f - ,""'- ~ are mostly represented by streams, rivers and vleis and are ~ N ";& _m .. ""or.I!' .. ... • ~" 7 mainl y found in bottomland situations. The area covers approxi­ , 2 . ·'",c."",n wt~, '\ mately 26 000 km Permanently waterlogged soil s are scarce -'- JO ·S \ and seasonally standing water is mostly restricted to s l ow -drain~ --~,. ing watercourses and drainage channels. Slow-draini ng st reams '\, 'l .." • are t.:omlllo n owing to the flatn ess of th e terrain over most of the " ~ -~D study area. • ~ 100 ~'" The rai nfall is erratic, especially in the western part of the r= I I stu dy area and increases in an easterly direction from a 300-400 mm per annum rainfall interval to a 600-800 !TIm per annum Figure I The location of the study area in relation La towns ill the rainfall interval. southern Free State. s. Mr. 1. Rot. 19n. fi4( I) tloristic data set was further subjected to an ordination algorithm 1.2 Buddleja saligna- ElU.:/ea crispa Community (H il l I 979b). 10 determine habitat gmdients and the relationship with J .2. J Opl/nlia ficll .~·- illdica- Blidd/eja salignQ Sub-community. cnvironrnl!lltal variables. 1.2.2 Hermannia b,),olliijolia P(lwmin Imrchellii Sub-community. Results and Discussion 1.2.3 May tenus po/yacantha· Bllddleja ,W/ligna Sub-community. The vegetation of the rocky outcrops of the study area generally 1.2.4 Pupa/ia lappac·ea -Lantana rllgosa Sub-community. has a low species diversity (See Table I ), but contains a variety 1.2.5 Aloe broomii- 71wmeda Irimu/ra Sub-community. of trees, shrubs, herbs and forbs. The general vegetation of the 1.2.6 Triraphis andropogonoides- /Jmld/eja saligl1a Sub-communi ty. rocky outcrops can be classified as the Themedcllriandra- Eliclea 1.2.7 Buddleja saligna- Themeda f,-i(lnelro Sub-community. cri,\pa Shrub land. This vegetation can be divided into two major communities, namely shrub land vegetation of hills and ridges 1.3 Tarchonanthus camphoraflls-Themeda triandra Community. (Major community 1) and dwarf shrubland associated with flat 1.3.1 Digitaria eriallllw- TarehOlUlI1llll1s camphoratus areas on the plateaux of hills (Major community 2). Sub-community. The shrubland of the hills and ridges can further be divided 1.3.1.1 !-lermmmia vestita- Prota.vparagus capel1sis Variant. into four di stinct vegetation types: 1.3. 1.2 Se/ago albido- ()xalis comir;lI/ma Variant. I 3.1.3 Light/oOlia albens- Euslachys paspaloides Variant. 1. J shrubland of ravines and south- and east-facing slopes; 1. 3.2 HelichryslIlll =eyheri- Themeda Iriandra Sub-community. 1.2 shrllbland of the drier north and west-facing slopes; 1.3.3 Euryops mulllfidus-TarchOlulIll/llIs camphm·ofll.'i 1.3 shrubland of the dry, overutilized and disturbed crests and Sub-community. plateaux; and 1.3.4 Rhigo=um ObOl'alllJ11- J'urchVllClnthwi cGmphv/·a/u.\" J.4 shrubland of low hills on north and west-facing slopes. Sub-community. The most abundant woody species associated with the hills 1.3 .4.1 Slipagroslis l1amaquel1sis- Rhigo=unJ ohOl'OIl1111 Variant. include Olen ellropuea, Grell'ia vccideJ1lalis (species group K, 1.3.4.2 RhigozllIn obovatum-Heteropogoll cOJ/lorlus Variant. Table 1), Buddleja saligna (species group Q), TardlOnanrll/{s Community. camphoratus (species group Z), Em'lea crispo, Rhll ,~' erOSQ, Feli­ 1.4 Elldea crispa- Themeda trialldm 1.4.1 Euclea crispa- Tragus berlervniaJlIl.\· Sub-community. cia fi/i/olia, Diospyros austro-a.!ricana, £hretia rigida (species 1.4.2 Setaria sphacelala- Rhus ciliala Sub-community. group AF). Rhus burchellii, and R. ciliata (species group Al, 1.4.3 Phyllanthus parvuhls- SeSal11uII7 capense Sub-colllmunity. Table 1). 1.4.4 Kleinia longifolia- Themeda Jriandra Sub-community. The grasses, DigiJaria eriantha (species g roup U) and £us­ 1.4.5 Cymbopogon excavallls- Euc!ea crispa Sub-communily. tachys paspa/oides (species group T) frequently occur in open 1.4.6 Euclea cr;spa- Arislida diffusa Sub-community. shrubland. but are limited to the low shrubland vegetation. Graminoids such as Themeda lriandra and lieferopogon conlor­ 2 ivlohria caffrorum- 7hemeda triandro Major-community. Ius (species group AJ) are conspicuous throughout the entire 2. 1 Eberlan=io spinosa- Mohria caffrorum Community study area (Table I). 2.2 Fdicia maricala- Mohria ca.ffrorllm Community. Dwarf shrubland associated with flat areas on the plateaux of hills occurs primarily under dry conditions, is virtually unpro­ Description of the communities tected from v·lind erosion, and is restricted· to only a few shrubs 1 Euclea crispa-Aristida ddfi/sa Major Community and dwarf shrubs such as Rhus erosa, R. ciliata, Eberlanzia spinosa and Febcia '!lUricata as well as the small fern, Mohria This shrubland occurs mostly on the southerly and easterly fac­ caffrorulII (Table 1 ) .