Mopane Shrubveld on Gabbro, Timbavati River to Phonda Hillocks west of Shingwedzi
Location and Geomorphology
The landscape forms a narrow intermittent strip from the Timbavati River to Phonda hillocks west of Shingwedzi. It is a continuation of the gabbro intrusion that also forms the underlying material of Landscape 19. The terrain of this landscape is flat to slightly undulating and is higher situated than the surrounding granite (+/- 350 metres). Numerous outcrops or koppies like Shilawuri, Chugamila, Tsange and Phonda consist of undecomposed gabbro. This landscape covers 284 km/2 or 1,5 percent of the area of the KNP.
The mopane shrubveld on gabbro is high lying and frost seldom occurs. Temperature data for Letaba and Shingwedzi (Tables 5 and 6) are applicable to this landscape. Rainfall varies between 450 and 500 mm per annum.
The soils that develop from the gabbro are dark in colour and contain relatively large amounts of clay. These soils contain more exchangeable nutrients compared to soils that develop from granite, therefore the grazing on the gabbro is usually more palatable. Dominant soil Forms are Milkwood, Mayo, Bonheim and Swartland with vertisols in the areas with a concave topography. The soils on the koppies are shallow and can be classified as lithosols.
Gertenbach (1978) gives a complete description of this landscape under the name of Themeda triandra/Colophospermum mopane-shrubveld (Fig. 57). Two variations of the shrubveld viz. a Sclerocarya caffra- and an Acacia nigrescens-variation occur. The two variations differ not only as far as their botanic composition is concerned but have considerable differences in structure. The Sclerocarya caffra-variation is dominated by Colophospermum mopane shrubs and the following woody species are common: Commiphora africana, Sclerocarya caffra, Acacia exuvialis, Albizia harveyi, Dalbergia melanoxylon, Grewia bicolor and Cissus cornifolia. There are practically no large trees in this shrubveld. A structural comparison of the two variations is described in the origina article
Fig. 57. Landscape 24. Colophospermum mopane Shrubveld on Gabbro. – page 89
The Acacia nigrescens-variation is also a shrubveld, but a few larger shrubs and trees occur. Colophospermum mopane trees and shrubs occur and the following woody species are present: Acacia nigrescens, Commiphora africana, Dichrostachys cinerea subsp. africana, Acacia tortilis, Ziziphus mucronata, Acacia exuvialis, Albizia harveyi, Securinega virosa, Lannea stuhlmannii, Grewia bicolor, Cissus cornifolia and Dalbergia melanoxylon. As far as the botanic composition is concerned the Acacia nigrescens-variation has a greater variety of species than the Sclerocarya caffra-variation.
The field layer of both these variations are dense and have the following dominant species in common: Fingerhutia africana, Panicum coloratum, Scmidtia pappophoroides, Heteropogon contortus, Digitaria eriantha var. pentzii, Bothriochloa radicans, Themeda triandra, Cymbopogon plurinodis, Eragrostis superba, Panicum maximum, Urochloa mosambicensis, Heliotropium steudneri, Phyllanthus pentandrus, P. asperulatus, Corbichonia decumbens, Euphorbia neopolycnemoides, Tephrosia polystachya, Indigofera bainesii, Corchorus asplenifolius, Rhynchosia totta and Ipomoea crassipes. The following herbaceous species are restricted to the Acacia nigrescens-variation: Sporobolus nitens, Pavonia patens, Veronia fastigiata, Hibiscus pusillus, Tragia dioica, Ipomoea obscura and Commelina bengalensis.
The vegetation that occurs on the gabbro outcrops (Fig. 58) include the following species: Combretum apiculatum, Pappea capensis (mountain type). Kirkia acuminate, Acacia nigrescens, Berchemia discolor, Bridelia mollis, Cassia abbreviate, Commiphora mollis, Diospyros mespiliformis, Dombeya rotundifolia, Ficus soldanella, Steganotaenia araliacea. Sterculia rogersii, Terminalia prunioides, Combretum mossambicense, Gardenia resiniflua, Grewia hexamita and G. flavescens.
Fig. 58. Landscape 24. Shilawari, a gabbro outcrop. – page 90
Seeing that the structure of the mopane-shrubveld corresponds with that of Landscape 23 (Colophospermum mopane Shrubveld on Basalt) there is also a similarity in the animals that occur here. Roan antelope for example occur on the gabbro between Letaba and Phalaborwa. The same applies for small herds around Stapelkop dam and Nkokodzi. Other game species that occur in this landscape are buffalo, zebra, eland, ostrich, white rhino (at Chugamila) and single elephant bulls. Tsessebe occur around Swartkops, Stamp-en-Stoot and Stapelkop dams. Kudu, waterbuck, impala and giraffe are notably scarce in this type of veld.