23. COASTAL BUSHVELD-GRASSLAND

Synonym:

Coastal Forest and Thornveld (A1)

Statistics:

11 881 km²; area transformed unknown but high; 14.03% conserved.

Locality & Physical Geography:

This mosaic of vegetation types occurs from just above sea level to about 300 m altitude. The terrain is more or less flat to gently undulating, but rises overall quite steeply towards the interior. The area is deeply dissected by the many rivers which drain eastwards across KwaZulu-Natal.

Climate:

The climate is humid with only one or two months experiencing very little or no rain. The rainfall exceeds 1 000 mm per year. Mean annual temperatures for January are around 25C and those in July around 17C.

Geology & Soil:

Sandy soils of Quaternary aeolian and marine origin.

Vegetation:

Remaining forest patches are characterised by species such as: Forest Iron Plum Drypetes gerrardii, Umzimbeet Millettia grandis, White lronwood Vepris undulata, Protorhus longifolia, Trichilia emetica, Brachylaena spp., Celtis spp., Chaetacme aristata and Mimusops obovata. These forest patches are also characterised by a large number of species of woody lianas. Much closer to the seashore, evergreen thicket occurs on littoral dunes. On the seaward side the canopy exhibits the typical clipped appearance of wind-pruning as a result of constant exposure to salt-laden easterly winds. Typical canopy species are: Coast Red Milkwood Mimusops caffra, Dune Jackalberry Diospyros rotundifolia, Natal Guarri Euclea natalensis, Brachylaena discolor and Apodytes dimidiata. Secondary woody vegetation is patchy and often characterised by Sweet Thorn Acacia karroo together with Scented Thorn A. nilotica and Splendid Thorn A. robusta. The grassy matrix includes species such as Ngongoni Bristlegrass Aristida junciformis, Eragrostis spp., Sporobolus spp., Hyparrhenia spp., Digitaria spp., Setaria spp. and occasionally Themeda triandra. The vegetation often has a shrubby appearance, due to many dwarf geoxylophytes, including Diospyros galpinii, Dwarf Mobola Parinari capensis subsp. incohata, Veined Medlar Pachystigma venosum, Eugenia albanensis, E. capensis, Ancylobotrys petersiana and Salacia kraussii. Locally, at swampy localities in northern KwaZulu-Natal, the Illala Palm Hyphaene coriacea, is very prominent.

Key Environmental Parameters:

The vegetation is restricted to sandy soils of marine origin and is influenced by salt spray, fire and grazing. The water table plays a crucial role in defining plant communities on the geologically young substratum.

Economic Uses:

Agriculture, especially for sugar, and exotic timber plantations. Wild timber has long since ceased to be economically viable, but extensive exotic plantations have been established.

Conservation Status:

Well conserved along the coast, mainly at St Lucia, Sodwana and Kosi Bay. However, the unique inland bushveld/ grassland plains, which are high in endemic plant species, are poorly conserved. Existing examples of this vegetation type are mere remnants. Where they do occur they invariably exhibit signs of disturbance and invasion by alien plants' At around 2 000 years before present, this disturbance commenced in the north with the arrival of the first Black farmers on the coastal plain. However, the disturbance which they created was generally light and highly localised. From the turn of this century urbanisation, industrial development and establishment of sugar and timber plantations, as well as plantations of other tropical crops such as bananas, became the main causes for the eradication of this vegetation type. Good specimens of valuable timber species have long since been removed but illegal exploitation of poorer specimens continues to pose a threat.

Key References:

Moll (1976), Tinley (1976), Weisser (1978), Van Wyk (1995).

Authors:

Ed Granger, George Bredenkamp & Noel van Rooyen.