Best Game Viewing Area in Kruger. Main Wildebeest, Zebra Habitat on Sclerocarya caffra and Acacia nigrescens Savanna
Gertenbach Landscape Number 17 includes Sclerocarya caffra and Acacia nigrescens Savanna
In my opinion this large region is probably the best in the whole Kruger National Park if you want to see large herds, wide varieties of animals including the Big 5.
This landscape extends from the Crocodile River in the south to just north of Satara with the Lebombo Mountains as the eastern and the Karoo sediments as the western boundary. It is one of the largest landscapes and occupies 1411 km/2 or 7.2 percent of the KNP. A characteristic of this landscape is that it consists of reasonably flat plains with individual well defined drainage channels.
Location and Geomorphology
All the larger rivers such as the Crocodile, Sabie, Nwaswitsonto, Nwanedzi and Sweni cut through the landscape while smaller spruits such as the Nhlowa, Mlondozi, Guweni, Mrunzuluku, Gudzane, and Mtomene drain this area. According to Bristow (1980) the underlaying parent material of this landscape is Sabi River Basalts with a possibility of dolerite intrusions in the basalt.
The altitude varies from 170 metres in the vicinity of Crocodile Bridge to as much as 250 metres above sea level, just north of Satara.
The Sclerocarya caffra/Acacia nigrescens savanna is the centre of the wildebeest and zebra habitat in the KNP. These animals migrate annually between the northern and southern parts of this landscape (Smuts 1974). In summer when water and grazing are plentiful the game congregates in the vicinity of Tsokwane/Lindanda/- Guweni/Sweni to migrate southwards to the Mlondozi/Sabie River area in the dry season. It appears that the annual migrations take place between the two most important variations of the Sclerocarya caffra/Acacia nigrescens savanna as described above.
Buffalo, kudu, giraffe, waterbuck, steenbok and ostrich occur in large numbers but elephant are only represented by lone bulls. These elephant bulls have caused considerable damage to large trees near the tourist and firbreak roads. The role played by herds of buffalo in keeping the veld short and open for animals such as wildebeest and zebra is a feature which should be exploited in the management of buffalo. Tsessebe are present at Mlondozi. Individual reedbuck are regularly seen in the long grassveld north of Satara. Lions are abundant, and like the wildebeest and zebra, this landscape is probably the centre of their distribution in the KNP. Hyaenas are plentiful, while cheetah are well represented.
Gertenbach(1980) states that the rainfall of this landscape diminishes from south to north. The long-term average annual rainfall at Crocodile Bridge is 599,6 mm while the average for Satara is 548.2 mm. The temperature experienced in this landscape probably varies as well, but Table 3 gives the temperature for Satara which is probably applicable to this landscape as a whole. Frost is limited to the bottomlands along the rivers and even then on an irregular basis.
The Sabi River Basalts weather to form a black, brown or red clayey soil. The soil depth does not normally exceed one metre and the dominant Forms are Bonheim, Shortlands, Swartland, Milkwood, Mayo, Glenrosa and Valsrivier. In the low lying areas vertisols of the Arcadia and Rensburg Forms can also be expected. The soil pattern is relatively homogeneous and no great changes in soil types occur over short distances. The clay contents in the soil varies between 25 and 50 percent and it is rich in plant nutrients. Table 8 indicates the quantity of exchangeable plant nutritients of a typical soil sample.
Table 8 … Exchangeable plant nutrients of a typical soil sample in Landscape 17
Soil Form: Bonheim
Soil Series: Bushman
Parent Material: Basalt
|A - Horizon||B - Horizon|
Van Wyk (1973) divides the landscape in two, viz. Knobthorn/Maroela-veld and the Leadwood/Maroela/Albizia-veld. Pienaar (1963) calls it the Sclerocarya caffra/Acacia nigrescens savanna, while Van der Schijff (1957) referred to it as the Knoppiesdoring/Maroela bushveld with five associations of which only two have a direct bearing on this landscape. The other three associations belong to other landscapes. Coetzee (1983) describes this landscape as a non-vertic, tropical, semi-arid,
Fig. 36. Landscape 17. Sclerocarya caffra/Acacia nigrescens Savanna south of Tshokwane. – page 64 original report
Fig. 37. Landscape 17. Sclerocarya caffra/Acacia nigrescens Savanna north of Tshokwane. – page 64
Basaltic lowveld. He distin, Aristidaguish 14 different plant communities that represent different variations of Sclerocarya caffra/Acacia nigrescens-veld.
The most important two components of this landscape are the Sclerocarya caffra and Dichrostachys cinerea/Pterocarpus rotundifolius/Themeda triandra-tree-veld south of Tshokwane (Fig.36) and the Sclerocarya caffra/Acacia nigrescens/Themeda triandra/Bothriochloa radicans-tree-veld north of Tshokwane (Fig.37). This larger division is mainly attributed to the higher rainfall in the southern and the lower rainfall in the northern section of this landscape, with the 550mm isohyet as the reputed boundary. The other associations described by Coetzee (1983) for this landscape are either very local or are secondary communities as a result of overgrazing. The Sclerocarya caffra/Dichrostachys cinerea/Pterocarpus rotundifolius/Themeda triandra-tree-veld south of Tshokwane is an open tree savanna with a moderate shrub later, but with a dense field layer. Dominant trees in this association are Sclerocarya caffra, Acacia nigrescens, Lannea stuhlmannii and Lonchocarpus capassa. Species in the shrub layer are Dichrostachys cinerea subsp. africana, Pterocarpus rotundifolius, Acacia nilotica, A. gerrardii, Albizia harveyi, Maytenus senegalensis, Ozoroa engleri, Ximenia caffra, Dalbergia melanoxylon, Maytenus heterophylla and Cissus cornifolia. The two variations of the veld are best distinguished by the presence or absence of Maytenus senegalensis. The field layer is dense and the sequence of dominance is Themeda triandra, Panicum coloratum, Digitaria eriantha var. pentzii, Bothriochloa radicans, Panicum maximum, Heteropogon contortus and Urochloa mosambicensis.
The Sclerocarya caffra/Acacia nigrescens/Themeda triandra/Bothriochloa radicans-tree-veld north of Tshokwane is also an open tree savanna with a moderate to sparse shrub layer and a dense field layer. The dominant trees are Sclerocarya caffra, Acacia nigrescens, Lannea stuhlmannii and Combretum imberbe. The shrub layer is sparse to moderate and Acacia nigrescens, Dichrostachys cinerea subsp. africana, Albizia harveyi, Acacia gerrardii, A. tortilis, Grewia bicolor, Dalbergia melanoxylon, Securinega virosa, Combretum hereroense, Ziziphus mucronata, Ormocarpum trichocarpum, Maerua parvifolia and Ehretia rigida are usually present. The big difference between the two associations, nevertheless, lies in the composition of the field layer. The field layer of the latter association is also dense but the sequence of dominance is Themeda triandra, Bothriochloa radicans, Digitaria eriantha var. pentzii, Panicum coloratum, Urochloa mosambicensis, Aristida congesta subsp. barbicollis and Eragrostis superba. Other species that occur regularly are Enneapogon cenchroides, Schmidtia pappophoroides, Panicum maximum, Heteropogon contortus and Sporobolus fimbriatus.
Everything indicates that the latter is a drier variation of the Sclerocaya caffra/Acacia nigrescens Savanna. Forbs which commonly occur in both the variations of the Sclerocarya caffra/Acacia nigrescens Savanna are Vernonia oligocephala, Rhynchosia minima, Chascanum hederaceum, Heliotropium steudneri, Crotalaria virgulata, Tephrosia polystachya, Rhynchosia densiflora and Cassia mimosoides. A characteristic of this landscape is that forbs are fairly scarce in the stable undisturbed veld. Under conditions of moderate to heavy grazing the above-mentioned forbs show a marked increase and species such as Solanum panduraeforme, Sericorema remotiflora, Pavonia patens, Ipomoea obscura, Justicia flava, Hermbstaedtia odorata, Corchorus asplenifolius, Barleria prionitis and Phyllanthus asperulatus increase considerably.
On the floodplains along the Sweni spruit in this landscape a unique community which consists of a Hyphaene natalensis-savanna occurs (Fig. 38). Dominant woody species are Hyphaene natalensis, Acacia tortilis, Euclea divinorum, Lonchocarpus capassa and Croton megalobotrys. Dominant grasses are Sporobolus nitens. S smutsii, Dactyloctenium aegyptium, Chloris virgata and Schmidtia pappophoroides. This stand of Hyphaene natalensis is the most southerly and impressive occurrence fo this species in the KNP and is therefore given special attention and protection against fires.
Fig. 38. Landscape 17. Hyphaene natalensis Savanna. – page 66
The vegetation on Oakleaf-soils on the banks of spruits and rivers is a tall tree savanna and includes the following woody species: Lonchocarpus capassa, Ficus sycomorus, Diospyros mespiliformis, Kigelia africana, Trichelia emetica, Croton megalobotrys, Acacia robusta, A. tortilis, Combretum hereroense, C. imberbe, Maytenus senegalensis, Acacia xanthophloea and Hyphaene natalensis, Phoenix reclinata and Cyperus sexangularis occur in the stream beds, together with Phragmites australis. The stream banks of this landscape has a typical floodplain, dyke wall and stream bed. (Fig. 39).
Local vegetation variations of this landscape were described by Coetzee (1983). Where soils become shallow the following species occur more commonly: Combretum apiculatum, Acacia exuvialus, Terminalia prunioides, Grewia bicolor, Digitaria eriantha var. pentzii, Aristida congesta subsp. barbicollis and Heteropogon contortus.
Fig.39. Landscape 17. Sweni stream bank. – page 67
Fig. 40. Landscape 17. Acacia gerrardii Savanna – page 67
In the vicinity of Rietpan/Mlondozi, Acacia gerrardii and Pterocarpus rotundifolius are dominant and Sclerocarya caffra is almost absent (Fig. 40). In certain low lying parts, species such as Acacia tortilis, Combretum imberbe, Lannea stuhlmannii, Dalbergia melanoxylon and Lonchocarpus capassa are more common. Where soils are very clayey and show vertic characteristics stunted Acacia nigrescens with Setaria woodii-stands occur and where the soils show signs of sodium saturation, species such as Acacia borleae associated with Chloris mosambicensis and Setaria woodii occur (Fig.41). The grass Schoenefeldia transiens is limited to this community and it is the only record of this grass being found in the Republic of South Africa. The latter vegetation variation will be discussed in more detail under Landscape 18.
Landscape 41. Landscape 17. Acacia borleae thickets. – page 68
The occurrence of impala in this relatively high grassveld is observed from time to time. This phenomenon should be seen in a serious light considering that the occurrence of this game species, especially in the inner veld, indicates a deterioration of the field layer and suggests that the bush encroachment is taking place. The use of such indicator species is of great value in monitoring natural phenomena in the KNP.