Fynbos Biome

[Renosterveld] [Fynbos]

The Fynbos Biome is considered by many to be synonymous with the Cape Floristic Region or Cape Floral Kingdom. However, the "biome" refers only to the two key vegetation groups (Fynbos and Renosterveld) within the region, whereas both the "region" and the "kingdom" refer to the general geographical area and include other vegetation types in the Forest, Nama Karoo, Succulent Karoo and Thicket Biomes, but exclude peripheral outliers of the Fynbos Biome such as the Kamiesberg, North-western and Escarpment Mountain Renosterveld (59,60) and Grassy Fynbos (65) east of Port Elizabeth. However, the contribution of Fynbos vegetation to the species richness, endemicity and fame of the region is so overwhelming, that the Cape Floristic Region and Cape Floral Kingdom can be considered to be "essentially Fynbos."

The Cape Floral Kingdom is the smallest of the six Floral Kingdoms in the world, and is the only one contained in its entirety within a single country. It is characterized by its high richness in plant species (8 700 species) and its high endemicity (68% of plant species are confined to the Cape Floral Kingdom). The Cape Floral Kingdom thus compares with some of the richest floras worldwide, surpassing many tropical forest regions in its floral diversity.

In South Africa, over one third of all plant species occur in the Cape Floral Kingdom, even though the Kingdom occupies less than 6% of the area of the country. This is not primarily due to the large number of vegetation types in the Cape Floral Kingdom. Over 7 000 of the plant species occur in only five Fynbos vegetation types, with perhaps an additional 1 000 species in the three Renosterveld vegetation types. The contribution of Succulent and Nama Karoo, Thicket and Forest vegetation types in the region to the plant species diversity is thus relatively small. Thus, although the Cape Floral Kingdom contains five biomes, only the Fynbos Biome, comprising the Fynbos and Renosterveld vegetation groups, contains most of the floral diversity. Furthermore, the Cape Floral Kingdom traditionally does not include the Fynbos and Renosterveld vegetation outliers to the north and east. Including these would mean that endemicity would approach 80%, the highest level of endemicity on any subcontinent.

Distressingly, some three-quarters of all plants in the South African Red Data Book occur in the Cape Floral Kingdom: 1 700 plant species are threatened to some extent with extinction! This is much more than one would expect based on either the area of the Kingdom (6%) or its plant numbers (36%). This again reflects the unique nature of Fynbos vegetation: many Fynbos species are extremely localized in their distribution, with sets of such localized species organized into "centres of endemism." The city of Cape Town sits squarely on two such centres of endemism and several hundred species are threatened by urban expansion. However, a more serious threat is alien plants, which infest large tracts of otherwise undisturbed mountains and flats: their impact on these extremely localized species is severe. Aliens are thus the major threat to Fynbos vegetation and its plant diversity, especially in the mountains. On the lowlands and on the less steep slopes the major threat is agriculture - new technologies, fertilisers and crops are steadily eating into our floral reserves. Another important threat is the misuse of fire. Fynbos must burn, but fires in the wrong season (such as in spring, instead of late summer) or too frequently (so that plants do not have time to set seed) eliminate species. Several factors influence fire dynamics in Fynbos - global warming, grazing practices and fire management (ignition events, size of burns), but their relative importance and interactions are poorly understood.

The two major vegetation groupings in Fynbos are quite distinct and have contrasting ecological systems. Essentially, Renosterveld used to contain the large animals in the Cape Floristic Kingdom, but these are now extinct or else have been reintroduced into conservation areas. By contrast, Fynbos is much richer in plant species, but has such poor soils that it cannot support even low densities of big game. However, most of the endemic amphibian, bird and mammal species in the region, occur in Fynbos vegetation types. Key references: Bond & Goldblatt (1984), Hall & Veldhuis (1985), Cowling (1992), Rebelo (1994), Cowling & Richardson (1995).


 

Renosterveld

Map of RenosterveldRenosterveld is characterized by the dominance of members of the Daisy Family (Asteraceae), specifically one species - Renosterbos Elytropappus rhinocerotis, from which the vegetation type gets its name. Although Renosterbos is the characteristic dominant, many other plants are also prominent - for instance in the Daisy Family (Asteraceae): Eriocephalus, Felicia, Helichrysum, Pteronia, Relhania; Pea Family (Fabaceae): Aspalathus; Gardenia Family (Rubiaceae): Anthospermum; Cocoa Family (Sterculiaceae): Hermannia; Thyme Family (Thymelaeaceae): Passerina. All these shrubs are characterized by their small, tough, grey leaves.

Grasses are also abundant. In fact, it is alleged that the high shrub cover is a result of continuous grazing. Early records suggest that the Renosterveld had abundant grasses, and that the game and Khoi cattle migrated over the region. With the establishment of European stock farmers, continuous grazing and the elimination of the diverse grazing-browsing fauna, the shrubby element was promoted. This theory is not universally accepted, but proponents argue to the sudden decline of hay near Cape Town in the early 1700s, and the many historical records of early explorers claiming that Renosterbos was taking over and that grass was becoming scarce.

Another feature of Renosterveld is the high species richness of geophytic plants (chiefly in the Iris Family (lridaceae) and Lily Family (Liliaceae), but also in the Orchid Family (Orchidaceae)).

Proteas, Ericas and Restios - typical of Fynbos - tend to be absent in Renosterveld, or are present at very low abundances. There are few endemics to Renosterveld vegetation alone, many of the species occurring in Fynbos as well. However, species endemic to the Cape Floral Kingdom comprise about one-third of Renosterveld plant species, and many of these belong to families which are not considered to be of "Cape affinity" (i.e. these families are also diverse outside the Cape Floral Kingdom).

Typically, Renosterveld is largely confined to fine-grained soils - mainly clays and silts - which are derived from the shales of the Maimesbury and Bokkeveld Groups and the Karoo Sequence. In drier regions it also occurs on Cape Granite Suite-derived soils. Because all these soils are fertile, much of Renosterveld has been ploughed for wheat.

Renosterveld tends to occur where rainfall is between 250 (rarely to 200 mm) to 600 mm per year and at least 30% falls in winter. Where the rainfall is higher, the soils become leached and Renosterveld is replaced by Asteraceous Fynbos. Generally, where the rainfall is less than 250 mm it is replaced by one of the Succulent Karoo vegetation types.

Because of its high soil fertility, it is probable that all the herds of large game in the Fynbos Biome occurred in Renosterveld. Thus Mountain Zebra, Quagga, Bluebuck, Red Hartebeest, Eland, Bontebok, Elephant, Black Rhino and Buffalo were common, as were Lion, Cheetah, Wild Dog, Spotted Hyena and Leopard. Two of these only ever occurred within the Fynbos Biome: Bluebuck and Bontebok. Of these large mammals, only the Mountain Zebra and Leopard survived (by fleeing to the mountains), with the Bontebok just surviving near Bredasdorp. All the other species became extinct in the Fynbos Biome (one elephant survives in the Forest Biome within the Fynbos Biome area), although many have been introduced into conservation areas from outside the region. The Quagga and Bluebuck are extinct.

This high fertility has meant that most of the area has been converted to agriculture. Less than 5% of West Coast Renosterveld remains (the Rio Convention has as its goal the preservation of 10%!), with other Renosterveld types also heavily ploughed or used as augmented pasture. It seems unlikely that viable populations of large mammals will ever be reintroduced into the Fynbos Biome for this reason.

The conservation status of this region has been the focus of several symposia and workshops.

 

Click images to enlarge  
Renosterveld 1
Renosterveld on Fairfield Farm, Napier, Western Cape.
Renosterveld 2
Spring flowers in Renosterveld, Nieuwoudtville, Northern Cape
Renosterveld 3
Renosterbos (Elytropappus rhinocerotis) in the foreground, near Pakhuis Pass, W. Cape.

Fynbos

Map of FynbosThe various Fynbos vegetation types comprise most of the area of the Fynbos Biome. Fynbos is characterized by the presence of the following three elements:

1. A restioid component, belonging to the Restionaceae or the Cape Reed Family. Some definitions require a mere 5% cover of restiods in an area to classify it as a Fynbos vegetation type. The Restionaceae have been described as shrubby grasses, and replace grasses on nutrient-poor soils where there is a strong winter component to the annual rainfall. Sedges and many grasses within Fynbos also share the "restioid" characters of reduced or absent leaves and tough, wiry stems.

2. An ericoid or heath component. By far the majority of plant species - and the greatest cover after restioids comprise plants with small, narrow, rolled leaves with thick-walled cells on the upper leaf surface and a channel containing hairs on the lower surface. Although the Heaths (Ericaceae) feature prominently, the Daisy (Asteraceae), Blacktip (Bruniaceae), Pea (Fabaceae), Jujube (Rhamnaceae) and Thyme (Thymelaeaceae) Families also have structurally similar leaves. Many of these plants are wispy and insubstantial, although some form quite dense bushes.

3. A proteoid component. These plants, almost exclusively of the Proteaceae, have broad, isobilateral (both surfaces similar) leaves. They are the dominant overstorey in Fynbos. Although some members occur in ecotones and some occur in Renosterveld, by far the majority are confined to Fynbos.

Fynbos is characterized by the presence of seven endemic or near-endemic plant families: Blacktips (Bruniaceae), Guyalone (Geissolomaceae), Sillyberry (Grubbiaceae), Brickleaf (Penaeaceae), Buttbush (Retziaceae), Dewstick (Roridulaceae) and Candlestick (Stilbaceae). Only the Bruniaceae (75 spp.), Penaeaceae (21 spp.) and Stilbaceae (13 spp.) comprise more than five species. The fifteen largest families comprise 70% of the species in the Fynbos Biome

Table of largest families in fynbos

Over 7 000 plant species occur in the Fynbos vegetation types. Endemicity is very high - over 80% of plant species are confined to the Cape Floral Kingdom and Fynbos Biome. The majority of these, although exact numbers are unknown, are confined to one or more of the various Fynbos vegetation types.

Many species have very narrow distributional ranges. Thus, based on the Proteaceae for which we have the most finely detailed data, some 24 centres of endemism (areas with species sharing similar localized distributional ranges) have been identified.

Whereas there is near unanimity as to the definition of Fynbos as a unit, there are widely divergent opinions on the major vegetation types within Fynbos. This stems from the high species richness and the large number of localized species, which prevents an easy comparison of species lists between centres of endemism. Consequently, the definition of vegetation types based on species composition, the basis for determining types in the other biomes, has never been achieved in Fynbos.

A structural approach, suggested by Campbell in 1985, recognises Proteoid, Ericaceous, Restioid, Asteraceous, Shrubby and Grassy vegetation types. This approach denies a difference in Fynbos types between the mountains and the lowlands of the Biome. However, the different types occur on a scale too fine to map here Ericaceous on the wet, upper south slopes, Asteraceous on the drier northern slopes and the wetter, shale-derived soils, Restioid on the winter water-logged and summer and slopes, and Proteoid on the richer colluvial, sandstone-derived soils. Shrubby Fynbos is ecotonal to forest where rock outcrops, gorges and stream courses protect the vegetation from fires, and Grassy Fynbos predominates where the summer component of the rainfall allows grasses to outcompete the restioids. These basic components are further subdivided into over 60 types based on structural adaptations.

An older classification by Moll & Bossi in 1983, recognized three main types of Fynbos. These are Mountain, Grassy and Lowland Fynbos. The Grassy type corresponds to that of Campbell. However, the Mountain and Lowland dichotomy has never been defined or defended. It has been criticised as merely one of cartographic convenience. Mountain Fynbos was classified into Dry, Mesic and Wet Fynbos, with a fourth type - Arid (for the northern Cederberg and Swartberg) - perhaps required. Grassy Fynbos was categorized as either Mesic (on southern slopes and nearer the coast) or Dry (northern slopes and predominantly inland). Lowland Fynbos was subdivided into three main types based on their edaphic (soil) requirements. Of the three, only the subdivisions of the Lowland Fynbos types correspond to mapable patterns of endemism and are adopted here (the other units were recognized on LANDSAT satellite imagery, but do not correspond to structural vegetation type classes).

Fynbos vegetation types occur predominantly on well-leached, infertile soils. The Cape Supergroup sandstones typically produce such soils, but under high rainfall conditions, granites and even shales become sufficiently leached to support Asteraceous Fynbos, replacing Renosterveld. This usually occurs at about 600 to 800 mm annual rainfall, but may be much less on granites, especially at higher altitudes. Below 200 mm Fynbos is replaced by Succulent Karoo, presumably because at such low rainfall, the vegetation does not burn frequently enough.

Fynbos has a low animal biomass, although species richness of birds, mammals, frogs, reptiles and insects is quite high, and most Fynbos Biome endemics occur in Fynbos vegetation types. Although these animals play a major role in pollination and seed dispersal, they appear to play a minor part in influencing vegetation structure and composition. This is partly due to the high carbon to nitrogen ratio, which effectively excludes browsing of all but the youngest leaves.

Fire is a major influence on Fynbos community processes. Fynbos must burn at between 6 and 45 years of age in order to sustain its plant species. Many species store their fruit in fire-safe cones for release after a fire, and ants are enticed to bury fruit where they are safe from rodents and fire. After fire many plant species resprout, but the majority rely on the predictability of fires and only regenerate after the fire from seeds. Without fire, Fynbos becomes senescent and Forest and Thicket elements begin invading.

Because of the low productivity of Fynbos vegetation types, due to the infertile soils, they are little utilized for agriculture. The major use of Fynbos is for recreation, water catchment and exotic plantations. In some areas vegetation harvesting for the cut-flower trade occurs, and wild flower orchards are being established in Fynbos areas. The implications of these for hybridization and gene transfer are-poorly understood and are of conservation significance - we need to conserve the genetic material for future cultivar selections rather than lose wild genetic reserves by careless orchard placement. On richer soils where the rainfall is high, Fynbos has been converted to fruit orchards and vineyards. With more modern agricultural techniques (liquid fertilisation, terracing, hydroponics) much marginal land is becoming suitable for agriculture. At present dam building - both for agricultural and urban use - is a threat, albeit a minor one, compared with alien encroachment, urbanization and fires.

 

Click image to enlarge
 
Fynbos 1
Elim Fynbos (Lowland fynbos) Elim, southern Cape.
Fynbos 2
Proteoid fynbos dominated by Protea laurifolia, Leucadendron saligna and Restionaceae on the slopes of Keereomsberg, Western Cape.
Fynbos 33
Sand Plain fynbos near Wellington, Western Cape. The brown Cape reeds (Restionaceae) dominate the fynbos while the geelbos or common sunshine conebush (Leucadendron salignum, a fire resprouter) is the dominant shrub. In the background is the greatest threat to fynbos vegetation - alien invaders, in this case pines, although some Australian hakea or needlebush plants can be seen invading the foreground. The veld is about 5 or 6 years old, the dead bushes being members of the pea family (Aspalathus species) which have already set seed and died, some skeletons of plants from the previous fire cycle, and chopped out Hakea sericea. The soil is deep aeolian sand over granite or shale. Riverine habitat can be seen in the background. The fynbos on the mountains in the background will be similar in appearance, but much richer in species and with more ericoid shrubs.
Fynbos4
Mimetes cucullatus (Proteaceae), Bosmansbos, Western Cape.
Fynbos 5
Proteoid fynbos dominated by Protea eximia, Keeromsberg, Western Cape.
 Fynbos 6
Erica sp. amongst restios on the east-facing slopes of Keeromsberg, Western Cape

 

 

Text on this page from reference below, images by NBI staff members


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