Floristic and structural features of the coastal foreland vegetation south of the Berg River , western Cape Province , South Africa

Floristic and structural features of the three main vegetation types found in the coastal foreland of the western Cape Province, south of the Berg River, are outlined. Coastal Renosterveld. which occupies 6% of its former extent, is the most threatened type, followed by Coastal Fynbos (14%) and West Coast Strandveld (41%). Coastal Renosterveld is closely related to Mountain Fynbos vegetation found on clay-rich soils together with West Coast Strandveld inclusions in specific habitats. Coastal Renosterveld is the product of recent regular disturbance by a short interval burning regime and overgrazing.


INTRODUCTION
The Cape Floral Kingdom (Good. 1974;Takhtajan, 1969) is concentrated in the region known as Capensis (Taylor. 1978;Walter. 1973).The western part has a distinctly mediterranean-type climate with dry summers and wet winters, but eastward the rainfall becomes increasingly non-seasonal (Taylor. 1980).The region is bounded to the north and east principally by the Karoo-Namib Region together with some outliers of the Sudano-Zambezian and Afromontane Regions (Taylor. 1980;Werger, 1978;Werger & Coetzee. 1978;White, 1978).
The Capensis vegetation has recently been subdivided into two main formations, namely, the heathlands on oligotrophic soils which are called fynbos (Kruger, 1979) and mediterranean-type shrublands, the scrub formations found on the more fertile soils, called renosterveld and strandveld (Boucher & Moll, 1981;Di Castri, 1981).
The indigenous vegetation of the coastal foreland of the western Cape Province, between the Berg River and False Bay is described in this paper.Structural and floristic features of the vegetation are related to variations in the habitat.Some tentative suggestions on the affinities between the local veld types (Acocks, 1975) and their derivation are presented.The main vegetation types shown in Fig. 1 are based on the interpretation of 1: 10 000 scale orthophoto maps, on data obtained from the intensive study of three east-west transects through the area, and on field experience.Island outliers of The western Cape has been inhabited by hunter-gatherers since the Late Pleistocene and by herders for at least the last 2000 years (Avery, 1975).Nomadic Khoisan or Hottentot tribes used fire to stimulate vegetation regrowth for grazing purposes, a habit adopted by European man subsequent to his arrival here in 1652.Fires caused by lightning and by rock falls are considered to be a natural phenome non in the mountains of the south-western Cape (Taylor, 1978) and they would presumably have spread from there to the adjacent lowland areas.
European man has destroyed large areas of the coastal foreland vegetation through his unrelenting quest for grazing, for fuel and for arable land.This vegetation has been depleted to the extent that at most only 14,7% of the western coastal foreland vegetation remains in a reasonably natural state today.(Boucher & Jarman. 1977).Chamaephytes generally form a lower shrub layer with perennial grasses abundantly interspersed up to 1.0 m tall.Typical species of the lower shrub layer are Ehrharta calycina, E. villosa, Limonium perigrinum, Ruschia caroli, Tetragonia fruticosa and T. spicata.A high proportion of the West Coast Strandveld shrubs, dwarf shrubs and even annuals have succulent leaves or stems.Deciduous-leaved geophytes are regularly encountered and the annual flora often provides mass displays of colour in spring particularly in disturbed areas (Acocks, 1975;Boucher & Jarman, 1977;Boucher & Moll. 1981;Taylor, 1978).
Strandveld vegetation is very variable, for instance the sandy littoral generally supports prostrate, spreading succulent chamaephytes.while small patches of a tall broad-leaved sclerophyllous scrub, up to about 3,5 m high, with a closed canopy can develop in isolated sheltered positions between the dunes.The dominant species in these latter situations are Euclea racemosa and Sideroxylon inerme.Olea europaea subsp.africana.The margins and interior of these 2-4 m tall Olea patches are commonly dominated by deciduous, orthophyllous.microphyllous, nanophanerophytes, particularly a number of Rhus species.Hemicryptophytes and geophytes are usually abundant in the herbaceous stratum.These bush clumps are associated with Microhodotermes viator termitaria which have been present in the area for the last one million years (J.J. N. Lambrechts, pers.comm.).These bush clumps are also usually clustered around rock outcrops and drainage lines, probably because of more favour able, moist, local conditions.

Scattered clumps of
For at least a decade or two these old lands retain an overwhelming dominance of the Asteraceae found in the general Coastal Renosterveld matrix.Single robust Elytropappus rhinocerotis individuals have been found to persist for at least 50 years.
Coastal Renosterveld is not generally considered to be a true Cape heathland vegetation because it lacks the constant presence of the ericoid component (Taylor, 1978).although Ericaceae are not entirely absent from this veld type.

COASTAL FYNBOS
This heathland vegetation occurs on leached acid sands which accumulate from the in situ weathering of granites and sandstones, or as wind blown accumulations of sand from rivers or estuaries, or on leached maritime dunes.The sands vary in depth from less than a metre to more than 70 m.
The typical form of this veld type is dominated by ericoid.narrow leptophyllous, evergreen, divarica tely branched shrubs and rhizomatous hemicryptophyters 0,75 -1.50 m tall.Taller, up to 2,5 m high.micro-to mesophyHous, sclerophyllous, shrubs increase towards the margins of the Coastal Fynbos where the sand is shallower.Annual herbs and geophytes occur throughout, but they do not assume the same proportions found in either the Coastal Renosterveld or the West Coast Strandveld.The low nutrient status of the substrate is probably respon sible for the virtual absence of the invasive European annual flora.In contrast, this treeless vegetation (Campbell et al., 1979;Kruger, 1979;Levyns, 1961)

DISCUSSION
The West Coast Strandveld in the arid winter rainfall area of Namaqualand has a more open canopy than in the western Cape and the vegetation is generally shorter.Succulents become more prominent and the vegetation assumes the appea rance of Succulent Karoo after disturbance.Scrub forest patches are far more common in the strandveld east of False Bay, where the summer drought is less severe (Boucher & Moll, 1981;Taylor, 1961Taylor, , 1978;;Von Breitenbach, 1974).The West Coast Strandveld plants react to the dry summer and wet winter periods in an expected fashion, growing when it is wet and being generally dormant in the dry period.The dominant broad leaved sclerophyllous scrub species all sprout after fires.The West Coast Strandveld is, therefore, a typical mediterranean-type climate shrubland vege tation of lime-rich sandy soils adapted to a fire regime.

Some component species of the western Coastal
Fynbos are apparently out of phase with their environment in that they grow during the dry summer period.A high proportion of the Coastal Fynbos species have very small or reduced leaves, a low proportion of succulence and the perennial herbaceous flora is largely hard and stiff with reduced leaves and photosynthetic stems.These conditions are possibly an adaptation to the low nutrient status of the substrate where it is advantageous to utilize the meagre nutrient re sources efficiently, as soon as they become available, without wasting them in the production of unneces sary vegetative parts.They also have anatomical adaptations to use water economically (Cutler 1972;Low, 1980;Specht, 1979;Specht et al., 1980).
The ability of western Coastal Fynbos to survive under low rainfall minima is indicated by its presence in the semidesert conditions of Namaqua land in a rainfall of around 100 mm per annum.This contrasts markedly to the Coastal Fynbos in the Knysna area of the southern Cape, which receives a mean annual rainfall of about 1 400 mm per annum and occurs alongside tall temperate forests.The low rainfall (100-700 mm per annum), the summer soil moisture deficits and the periodic fires have been suggested as reasons for the absence of indigenous trees in the western Coastal Fynbos (Campbell et al., 1979).
Coastal Fynbos is far more uniform in composi tion than Mountain Fynbos, possibly because of the uniformity of the sandy plains in contrast to the great variety of niches present in the folded mountains of the Cape.
Coastal Renosterveld is akin to the Californian Coastal Sage (Rutherford, 1978;Taylor, 1978) in that it is the product of a disturbed environment.This condition is shown by the overwhelming dominance over large areas by a few species with pioneering abilities.It is tempting to postulate about the development of the Coastal Renosterveld to its present state.Species which can become dominant in pelitic upland fynbos, that is Mountain Fynbos on weathered granites or shales, are either dominant or are scattered through the Coastal Renosterveld.These species that are mainly confined to the shrubby matrix of the Coastal Renosterveld are largely unpalatable seed regenerating species with a short maturation period of maximally five years (e.g. the dominant Asteraceae), or sprouting species of Ericaceae (Erica sparsa), Proteaceae (Leucaden dron salignum) and Restionaceae (Restio cuspidata), or geophytes (Watsonia spp.).Fifty-four percent of the species found in a recent survey to be restricted to the Coastal Renosterveld have also been recorded in the Mountain Fynbos vegetation of the Jonkershoek State Forest.The remaining bush clump species on termitaria and around granite rock outcrops in the Coastal Renosterveld are largely sprouting species, geophytes and annuals which are structurally and floristically allied to the West Coast Strandveld.
The overwhelming contribution of species which can withstand recurrent five yearly fires is indicated in Table 2 for the western coastal lowland.
The conclusion drawn is that the western coastal foreland vegetation is the product of disturbance that probably took the form of repeated short interval fires, overgrazing and the collection of firewood (Acocks, 1979;Killick, 1979;Kruger, 1979;Levyns, 1929Levyns, , 1950Levyns, , 1956;;Story, 1952).
Present day longer intervals of more than ten years between fires and the almost complete

CONCLUSIONS
The West Coast Strandveld, Coastal Fynbos and Coastal Renosterveld all appear to be types that have been exposed to a relatively short interval fire regime and to heavy grazing.This is a relatively recent phenomenon, probably related to the appearance about 2 000 years ago of pastoral Khoisan (Hottentot) tribes, who used fire to improve the grazing for their flocks of sheep and cattle.Subsequent to their settlement here 300 years ago, European settlers adopted this practice in an uncontrolled fashion, despite repeated legislation and heavy fines designed to curb this habit (Botha, 1924).It might reasonably be postulated that the present composition and structure of the lowland vegetation, particularly of the treeless Coastal Fynbos, is due to the very recent introduction of a short interval fire regime under which a tree flora must still evolve.The success of the acacias, pines and eucalypts in the Coastal Fynbos suggests, however, that the evolution of an indigenous tree flora might never take place because this so-called 'vacant niche' will have been occupied.Unvegetated expanses of sand accompany overgrazing in Coastal Fynbos and result in longer intervals between fires.The systematic burning of this veld type to obtain better grazing has been superseded recently, in parts by brush-cutting.This system benefits the sprouting plants, particularly the Restionaceae, which achieve an overwhelming dominance to the detriment of seed regenerating species.This degradation is equivalent to that of Coastal Renosterveld and West Coast Strandveld, under a short interval burning regime coupled with overgrazing where the stages of degradation go from dominance by scrub, to shrubs, to low inedible dwarf shrubs, particularly succulents, to perennial herbs and finally to dominance by annuals.This degrada tion is considered to be related to a general drier soil climate.
Table 1 outlines the degree to which the three veld types in this area, namely.West Coast Strandveld, Coastal Renosterveld and Coastal Fynbos, have been reduced through the activities of man.Coastal Renosterveld is by far the most threatened of these veld types.
F ig. 1.-Coastal foreland vegetation of the western Cape south of the Berg River.

TABLE 1 .
-Remaining natural vegetation in the western Cape foreland south of the Berg River in 1972.Extracted from the 1972 series of Willdenowia striata and emergent Thamnochortus spp.(Restionaceae).as sociated with a depauperate West Coast Strandveld vegetation, occur with increasing abundance as the distance from the sea increases, together with marginal fynbos species belonging to the Fabaceae (Aspalathus), Polygalaceae (Muraltia and Nylandtia), Rutaceae (Agathosma and Diosma) and Thymelaeaceae (Passerina).Ericaceae and Proteaceae are not found in West Coast Strandveld vegetation.Rubiaceae) is generally abundant and geophytes belonging to the families Iridaceae.Liliaceae and Oxalidaceae are important compo nents of the basic Coastal Renosterveld matrix.Perennial grasses such as Cymbopogon marginatus, Pentaschistis spp.and Themeda triandra become locally abundant with annual European grasses and herbs common in very disturbed situations.Restion aceae are seldom dominant, but can usually be found in this veld type.Randomly scattered bush clumps through the Coastal Renosterveld matrix are dominated by the sclerophyllous evergreen tree.
COASTAL RENOSTERVELDThis veld type is found on shales and granites in a rainfall zone of 250-550 mm per annum.Typically, is very susceptible to invasion by trees and tall shrubs from the Australian heathlands, such as Acacia spp.andEucalyptus spp.Leptospermum spp., and by Pinus spp.from the northern hemisphere heathlands.x

TABLE 2 .
-Mode of regeneration of perennial species restricted to each of the three veld types in the coastal foreland of the western Cape (data based on observation and the analysis of sample data)