Renosterveld types:

RenosterveldNorth-western Mountain RenosterveldEscarpment Mountain Renosterveld Central Mountain RenosterveldWest Coast Renosterveld

62. WEST COAST RENOSTERVELD

Synonyms:

West Coast Renosterveld

Coastal Renosterveld (A46); Swartveld.

Statistics:

6 141 km²; ± 97% transformed; 1.76% conserved.

Locality & Physical Geography:

Western Cape forelands from just north of Piketberg, to Somerset West, mainly on the lowlands and low hills.

Climate:

The area is typically Mediterranean with most of its rain failing in winter. Rainfall varies from 300 to 600 mm, typically as cyclonic rain from cold fronts. The summers are hot and dry and conducive to fires.

Geology & Soil:

Confined largely to Malmesbury Group shales, Cape Granite Suite and Klipheuwel Formation shales, which weather to form heavy clays and loamy soils. In areas of higher rainfall, Fynbos elements become prominent and the boundary between Renosterveld and Fynbos vegetation types becomes diffuse. The area is characterized by "heuweltjies", which typically have more shrubby, thicket elements, although in some areas grasses may dominate.

Vegetation:

Characterized by mid-dense to closed cupressoid and small-leaved, mid-high evergreen shrubs, with regular clumps of broad-leaved, tall shrubs as emergents (especially on heuweltjies). The overstorey is dominated by Renosterbos Elytropappus rhinocerotis, with subdominants of Wild Rosemary Eriocephalus africanus, Dune Teabush Leysera gnaphalodes, Jakkalsstert Anthospermum aethiopicum, Athanasia trifurcata, Felicia filifolia, Metalasia muricata and Stoebe spiralis. The understorey is mainly annual and herbaceous with perennial grasses. The grass cover is sparser than in most other Renosterveld types, being dominated more by C₃ grasses (e.g. the genera Ehrharta, Pentaschistis, Merxmuellera, Tribolium, Cymbopogon and Eragrostis). Redgrass Themeda triandra and Cape Terpentinegrass Cymbopogon marginatus are locally abundant. Geophytes, mainly Irises (Iridaceae), Lilies(Liliaceae) and Sorrels (Oxalidaceae), are characteristic and may be abundant. The Mediterranean annual grasses, Oats Avena, Quaking Grass Briza and Ryegrass Lolium, have become widespread and common, and their effect on the indigenous grasses and geophytes is unknown. Bush clumps are dominated by typical Thicket Biome species, such as Wild Olive Olea europaea subsp. africana, Dune Taaibos Rhus laevigata and Bush Guarri Euclea racemosa.

Key Environmental Parameters:

Little is known about the early dynamics of West Coast Renosterveld. It has been suggested that grasses were never really dominant, and that Fynbos elements might once have been more common in the region. Records of large herds of big game suggest that grazing by large herbivores was important. The Khoi herders apparently used fire extensively to maintain a grassy component and migrated extensively within the region. Today few large tracts of Renosterveld remain, the largest being the Tygerberg Hills, and Elandsberg between Wellington and Voëlvlei. Less than 3% of natural vegetation remains, so that natural ecosystem processes are unlikely to persist.

Economic Uses:

Most of this vegetation type has been ploughed up for wheat. In wetter areas, viticulture is common. Small tracts of natural vegetation are used for grazing.

Conservation Status:

Less than 3% of the original area remains, with less than 1 % of the original area being found in nature reserves, the most important being the Elandsberg Private Nature Reserve. There are a large number of Red Data Book plant species in the area.

Key References:

Boucher (1981), Moll et al. (1984), Low & Jones (1995).

Author.

Tony Rebelo.