Vegetation and flora of the Southern Drakensberg Escarpment and adjacent areas

Abstract

The grasslands of South Africa, and especially the higher altitudinal grasslands, are under increasing human pressure. In this study a floristic-ecological account of the vegetation of the southernmost Drakensberg and its foothills is given. This is the first comprehensive botanical study undertaken in this floristically poorly known region. The study area is situated in the magisterial districts of Barkly-East, Elliot and Maclear between 30°40' and 31°35' S, and 27°25' and 28°35' E. In the study area afforestation is the greatest threat at lower altitudes, whereas at the higher altitudes overgrazing, trampling and invasion by exotic plant species impact negatively on the native vegetation. A brief review of the history and previous botanical exploration of the area, as well as the physical environment are given. Four main plant communities - the Maytenus undata- Rhus dentata woodland and forests communities, Harpechloafalx- Pycreus cooperi hygrophilous communities, Themeda triandra - Alloteropsis semialata high altitude communities and Alloteropsis semialata- Rendlia altera Afromontane grassland communities, with various sub-communities and variants are identified and described. An annotated check-list of the plant species collected in the study area and distribution maps of all the Drakensberg Alpine Region and local endemic species found in the study area are given. Twenty two local endemic species and 74 rare and threatened taxa were identified. During the study 1 991 species and infraspecific taxa of vascular plants were collected or listed. Most of the endemic species in the study area are located above 1 500m altitude. Due to the relatively low number of local endemic species (22) the study area can at best be considered as a weak centre of endemism. However, it is clearly linked with two other major centres of plant endemism, namely the Drakensberg Alpine Region (DAR) and Maputaland-Pondoland Region (MPR). Within the study area 194 DAR and 86 MPR endemic species were recorded. No local endemic species occur in the forest and wetland communities. Most of the rare and threatened species are found in open grassland which are the areas most suitable for afforestation. This causes a major conflict between the forestry industry and conservation agencies in the area. All grasslands situated at an altitude of above 1 600 m are floristically very diverse and adequate representative areas should be protected, especially the areas of Tentkop and Elands Heights. Soils here are highly erodible and forestry and trampling in these areas should therefore be avoided at all costs. The higher lying grasslands and, to a lesser extent, the lower lying grasslands are ecologically sensitive areas. This is particularly so where the underlying mother rock is basalt, which weathers into highly erodible soils. It is suggested that all areas above 1 600 m be declared "no-go" areas for afforestation. This is based on not only the number of endemic and rare species found in these areas, but also because of the floristic diversity and aesthetic value they hold for eco-tourism. All habitats are sensitive to some degree, but the most threatened areas are the higher lying and open grasslands. Areas that are generally unsuitable for afforestation include rocky outcrops, vleis, drainage lines and forests. Most of these areas are protected by law, albeit for reasons not to do with biodiversity or endangered species. AFRIKAANS : Die grasvelde van Suid-Afrika, en veral die hoërliggende grasvelde, is onder toenemende menslike druk. In hierdie ondersoek word 'n floristies-ekologiese weergawe gegee van die plantegroei van die mees suidelike Drakensberg-eskarp en voetheuwels. Hierdie is die eerste uitgebreide plantkundige ondersoek in dié gebied. Die studiegebied is geleë in die Barkly-Oos, Elliot en Maclear landdrosdistrikte tussen 30º40' en 31º35' S, en 27º25' en 28º35' 0. In die studiegebied is bosbou die grootste bedreiging in laerliggende gebiede, terwyl oorbeweiding, vertrapping en indringing van uitheemse plantspesies die grootste negatiewe impak op die inheemse plantegroei van die hoërliggende gebiede bet. 'n Kort historiese oorsig, die vernaamste vorige versamelaars in die gebied en 'n beskrywing van die fisiese omgewing word verskaf. Vier hoof plantgemeenskappe word onderskei - die Maytenus undata - Rhus dentata boomveld en woud gemeenskappe, Harpechloa falx - Pycreus cooperi vlei gemeenskappe, Themeda triandra - Allotercpsis semialata hoogliggende grasveld gemeenskappe en die Alloteropsis semialata - Rendlia altera Afromontaan grasveld gemeenskappe met verskeie sub-gemeenskappe en variante. 'n Spesielys van aile spesies wat tot nog toe in die studiegebied aangeteken is, asook verspreidingskaarte van alle Drakensberg Alpynse en lokale endemiese spesies wat in die studiegebied versamel is, word verskaf. Twee-en-twintig lokale endemiese spesies en 74 skaars en bedreigde spesies is vir dié gebied geïdentifiseer. Gedurende die ondersoek is 1 991 spesies en infraspesifieke vaatplanttaksa versamel of gelys. Die meeste van die endemiese spesies in die studiegebied word hoër as 1 500 m bo seevlak aangetref. As gevolg van die relatief lae getal endemiese spesies (22) in die studiegebied, kan hierdie streek slegs as 'n swak sentrum van endemisme beskou word. Die gebied vorm egter deel van beide die Drakensberg Alpynse Sentrum en die Maputaland-Pondoland Sentrum van endemisme. Vir die studiegebied is 194 Drakensberg Alpynse en 86 Maputaland-Pondoland endemiese spesies aangeteken. Geen lokale endemiese spesies word in die woud en vlei gemeenskappe aangetref nie. Die meeste van die skaars en bedreigde spesies is met oop grasvelde geassosieer. Laasgenoemde is ook die mees geskikte habitat vir bosbou. Dié feit is verantwoordelik vir die meeste konflik tussen die bosboubedryf en bewaringsgroepe. Grasvelde bokant 1 600 m het 'n hoë floristiese diversiteit en daadwerklike pogings behoort aangewend te word om dit te bewaar, veral in die Tentkop en Elands Heights gebiede. Gronde in hierdie gebiede is besonder maklik erodeerbaar. Bosbou en vertrapping deur vee behoort ten alle koste vermy te word. Die hoogliggende, en tot 'n mindere mate die laagliggende grasvelde is ekologies baie sensitief. Dit is veral die geval waar die onderliggende moedermateriaal basalt is, omdat laasgenoemde gesteente tot gronde met 'n hoë erosie-potensiaal verweer. Daar word voorstel dat geen bosbou in gebiede bo 'n hoogte van 1 600 m beoefen word nie. Hierdie voorstel word nie net gemaak op grond van die aantal endemiese, skaars en bedreigde spesies nie, maar ook met die oog op die voordele wat die estetiese landskap vir ekotoerisme mag inhou. Enige habitat is tot 'n sekere mate sensitief, maar in die studiegebied is die mees sensitiewe dele uit 'n plantkundige oogpunt is die hoërliggende oop grasvelde. Laerliggende gebiede wat nie vir bosbou geskik is nie sluit vlei gebiede, klip koppies en randjies, woude en dreinerings lyne in. Die meeste van hierdie gebiede word deur die wet beskerm, alhoewel nie noodwendig as gevolg van biodiversiteit of bedreigde spesies nie.