Southern Afrotemperate Forest (the Southern Cape Forests) is a kind of tall, shady, multilayered indigenous South African forest.This is the main forest-type in the south-western part ofSouth Africa, naturally extending from theCape Peninsula in the west, as far asPort Elizabeth in the east. In this range (apart from the massiveKnysna-Tsitsikamma forest complex), it usually occurs in small forest pockets, surrounded byfynbos vegetation.
This forest ecosystem is a subtype of the generalAfromontane forest, which can be found across Africa as far north as Ethiopia. However, it is distinguished from other types of forests in Southern Africa by its relatively distinct range of species and its being confined to the far south-western tip of Africa – separated from the other forested areas to the east and north. Southern Afrotemperate Forest tends to grow on soils derived fromsandstone andgranite which are the dominant rock formations in the south-western Cape.[1]
TheWestern Cape is prone to seasonal fires and the various types of fynbos vegetation that dominate here are all governed by the fire cycles. However, Southern Afrotemperate Forest is not adapted to fire, so is always restricted to "fire refugia" such as gorges, wet riverine areas, or rocky scree slopes where fires cannot reach. In the absence of veld fires, the taller forests tend to expand at the expense of the fynbos.[2]
It is conventionally divided into three closely related subtypes:
This is a type of medium-height scree forest usually only found in small patches, growing on steep, rocky slopes and by mountain streams. It is endemic to the Western Cape.
Based on location and the species composition of the forests, this type is often informally divided into riverine forests (oewerbos inAfrikaans) and scree forests (dasbos in Afrikaans). The species composition of these two subtypes differs slightly, but they are still similar enough to be classed together as an ecosystem. The dominant, largest, and most obvious tree species areMetrosideros angustifolia,Brabejum stellatifolium,Cassine schinoides,Apodytes dimidiata,Cunonia capensis,Ilex mitis,Kiggelaria africana,Rapanea melanophloeos,Olinia ventosa, andPodocarpus elongatus.
Western Cape Talus forests naturally undergo periodic disturbance, flooding in the case of riverine forests, and rock-slides in the case of scree forests. Swift regeneration immediately follows. The natural cycle of disturbance of the surrounding fynbos vegetation is fire-driven, but this has little effect on the sheltered talus forests.[3]
The main threats to this ecosystem are from invasive alien plants, especiallyblack wattle trees. The natural habitat of Western Cape Talus is usually withincatchment areas, and they thus perform an important function in regulating the water-systems and preventing erosion. They are also host to many scenic hiking trails and have value as a source of medicinal plants. In addition, several species (such asClivia mirabilis andCryptocarya angustifolia) are endemic to these forests and occur nowhere else in the world.[4]
The thicker, deeper, denser "South-western Cape forests" are dominated by larger afromontane trees. These tall woodlands are typically found in sheltered gorges and mountainous areas in the Western Cape.
They also include the Cape Peninsula Forests such as those atNewlands Forest,Kirstenbosch, andOrangekloof, which are all located aroundTable Mountain, within the city ofCape Town.
Typical species include massive trees such asyellowwoods,Ilex mitis,Kiggelaria africana,Assegai trees,ironwoods,Cunonia capensis,Cassine species,Olinia ventosa, andRapanea melanophloeos, which form the highest canopy; smaller trees such asHalleria lucida,Diospyros whyteana, andMaytenus acuminata, which form a medium layer; as well as a variety offerns, herbs, bushes,vines, andlianas (e.g.Asparagus scandens,Rhoicissus tomentosa). Though not as rich in biodiversity as the Southern Cape Afrotemperate forests, these woodlands still contain a variety of endemic plants and animals which occur nowhere else in the world.[5]
The major threats come from invasive alien plants such asAustralian cheesewood,bugweed, black wattle,lantana,privet, andpine trees. Western Cape Afrotemperate forests have a high socioeconomic value, due to their use forrecreation such as hiking, their role in preserving the Western Cape's water supply, and their natural production of an enormous range ofmedicinal plants.[6][7]
By far, the largest portion of Southern Afrotemperate Forest includes the enormousKnysna-Tsitsikamma forests. It extends fromMossel Bay in theWestern Cape, eastwards into theEastern Cape, nearly as far as Port Elizabeth.
This is a tall, dense, species-rich forest in a moist and warm temperate climate. The highest canopy is formed from the intermeshed crowns of the most massive trees. Understories are formed from medium-sized, multitrunked trees and the forest floor is home to a range of indigenous shrubs, bushes, ferns, and flowers. Enormouslianas and vines reach up to the canopy and between the branches and a variety of animals inhabit these woods. This forest is very similar to Western Cape Afrotemperate Forest with a very high species overlap; however, it also has some lesser similarities with the Amatole mistbelt forests that lie further to the east in the Drakensberg mountain range.Previously, large game was abundant, but today it is largely exterminated. A small population ofelephants survives atKnysna.
It is often subdivided into three smaller vegetation types: the Southern Cape Mountain forest, Coastal-Platform, and Scarp forests.[8]
Some of the major indigenous tree species:
