Basalt slopes to Levubu Riverare Dry Mopane Rugged Veld
Location and Geomorphology
The basalt slopes towards the Levubu River are physiologically dry as a result of the steep slopes and shallow calcareous soils. The terrain is strongly undulating and is comparable to the slopes of the Olifants, Letaba and Shingwedzi Rivers (Landscapes 7, 10, 21 and 22). Spruits draining this area are the Madzaringwe, Nkovakulu and Thanmbyi. Koppies occur regularly in this landscape.
The Adansonia digitata/Colophospermum mopane Rugged Veld is rugged in the true sense of the word. Rainfall varies between 450 and 500 mm annually and there is a relatively high run-off of rainwater as a result of the steep slopes. Pafuri with an average rainfall of 438 mm per year is in the centre of this landscape. The summer temperatures are very high with a 40o/c often experienced during the period November to March. Temperature data for Shingwedzi (Table 6) is probably the most applicable for this landscape where frost seldom, if ever, occurs.
The soils of this landscape are shallow, calcareous and contain a reasonable amount of clay. The soils are mostly dark in colour, but the structure of the topsoil is sometimes poorly developed. Dominant Forms are Milkwood, Mayo, Mispah and Glenrosa. Shallow lithosols occur on the koppies.
The vegetation of this landscape is discussed in detail by Van Rooyen (1978) under the heading colophospermum mopane/Commiphora glandulosa/Seddera capensis – Open Bush Savanna. This vegetation corresponds to that of the Colophospermum mopane shrubveld on Basalt (Landscape 23) and also to other forms of rugged veld viz. Landscape 4, 7, 10, 21 and 22.
It is an open tree savanna and the physiognomic dominance of Adansonia digitata and Colophospermum mopane trees and shrubs give the landscape its name (Fig.59). The following woody species also occur regularly: Kirkia acuminate, Sclerocarya caffra, Combretum apiculatum, Commiphora glandulosa, Terminalia prunioides, Grewia bicolor, Cissus cornifolia, Acacia nigrescens, Maerua parvifolia, Zanthoxylum humilis, Commiphora mollis, C. edulis, Sterculia rogersii, Dichrostachys cinerea subsp. adricana, Combretum mossambicense, Markhamia acuminata, Grewia villosa, Gardenia resiniflua and Ormocarpum trichocarpum.
Fig. 59. Landscape 25. Adansonia digitata/Colophospermum mopane Rugged Veld. – page 91
The sparse field layer is dominated by Enneapogon cenchroides, Aristida congesta subsp. congesta, Panicum maximum, Digitaria eriantha var. pentzii, Hibiscus micranthus and Neuracanthus africanus. The absence of Themeda triandra is conspicuous. Other herbaceous species that occur here are the following: Aristida congesta subsp. barbicollis, Bothriochloa radicans, Fingerhutia africana, Pseudobrachiaria deflexa, Rhynchosia totta, Seddera capense, Indigofera vicioides, Phyllanthus burchellii, Monechma monechmoides, Tephrosia polystachya, Euphorbia neopolycnemoides, Becium obovatum, Ecbolium revolutum, Dalechampia galpinii, Aptosimum lineare and Leucas glabrata.
Elephant, buffalo and zebra are the most important game species, but occur infrequently. Eland and sable antelope seldom occur, but impala are quite common. Nyala and kudu are fairly widespread while duiker and steenbok are well represented. Some baobab trees are seriously damaged by elephant bulls at certain times of the year, but these trees have an amazing ability to recover.