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Addo’s Diverse
Biomes A biome is a
major ecological community i.e. a division of the world’s
vegetation that corresponds to a particular climate and is
characterized by certain types of plants and animals, for
example Forest or Fynbos.
The park encompasses five of South Africa's seven biomes: -
Forest (Alexandria forest) in the Woody Cape area, -
Subtropical Thicket in the original Addo section (also in
the Kabouga, Colchester, Nyathi sections), - Grassland in
the Zuurberg section, - Fynbos in the Zuurberg section, -
Nama Karoo in the Darlington section. Subtropical Thicket is
the largest biome in the AENP, covering 69% of the area.
Forest covers 10% of the area. Nama Karoo covers 7% of the
area. Fynbos and Grassland each cover 5% of the area. (The
remaining area is covered by the dunefield).
In these 5 biomes, 43
distinct land classes have been mapped. 29 of the 43 land
classes (67%) have been identified as experiencing a high
level of threat. (Potential threats include grazing,
agriculture, alien plant infestation, mining and human
settlement disturbances).
The original Addo-Elephant
area is mainly covered by subtropical thicket (also known as
valley bushveld), characterized by impenetrable Spekboom. It
was this vegetation that protected the last remaining
elephant and buffalo from being wiped out by hunters.
The Zuurberg Mountains harbour deep wooded kloofs and
streams. In the exposed higher altitude areas, grassland and
fynbos are found. Moving inland over the mountains the area
around Darlington Lake turns to succulent Karoo-type (arid
semi-desert) vegetation known as Noorsveld. On the seaward
side of the original elephant section the Woody Cape section
contains a remarkable display of coastal dune-fields and
coastal grassy plains. Moving east the Alexandria Forest is
an excellent example of pristine temperate forest.
Subtropical Thicket
Subtropical Thicket
was formerly classified as a type of savanna but has
since been classified as a separate biome. The large
diversity of animals found is associated with the rich plant
diversity.
This biome contains
112 different vegetation types comprising 1558 plant
species. 322 of these species (20%) are endemic and found
nowhere else.
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Dune Thicket
occurs along the coastal strip in a narrow band.
Thicket occurs in the higher rainfall areas and woody
species are dominant, grasses are present and there are
less succulents.
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Valley Thicket
is found in valleys with a high woody component and more
succulents.
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Arid Thicket
is found in the interior with succulents being dominant
and a small woody component.
Grassland
Grassland is defined as those areas where grasses dominate
the vegetation and where woody plants are absent or rare.
They occupy 24,1% of the country's surface area. Most
grassland occurs in high-rainfall areas, where thunderstorms
and hail are common in summer and frost is common in winter.
The grassland biome is regarded as the third-richest area in
terms of plant species diversity, with a total number of 3
788 species. The most noteworthy species with a wide
distribution is rooigras (Themeda triandra).
Fynbos
Fynbos occupies 5,3 %
of South Africa with its complement of at least 8 578
species of flowering plants. It is recognised supporting one
of the most diverse and distinctive floras in the world. All
in all, 5 832 or 68 % of the plant species are endemic. Many
of the fynbos plant species are restricted to extremely
small distribution ranges, a fact which has rendered them
dangerously susceptible to extinction. Fynbos consists of
evergreen heathlands and shrublands in which fine-leafed low
shrubs and leafless tufted grasslike plants are typical.
Proteas, ericas and restios are typical components of fynbos.
Trees are rare and grasses comprise a relatively small part
of the biomass. The floristic diversity of the fynbos is not
paralleled by an equally rich fauna due to the absence of
grass and berry-producing plants. Fire is a very important
component in fynbos. Most fynbos is highly flammable due to
the common presence of flammable oils. Finely wooded fynbos
plants are obligate seeders, which means that the whole
plant dies after fire and can only reproduce through seed.
This distinguishes fynbos from the other ecosystems where
fire is common. Many plant species are dependent for
pollination on small mammals or birds such as the Cape
sugarbird (Promerops cafer).
Both Grassland and
Fynbos are fire-dependent and fire-adapted. Research has
shown that isolated patches of fire-prone vegetation can
lose up to 75% of their species when fires are prevented
from spreading to them for long periods. This has
implications on management actions since both Fynbos and
Grassland in the AENP are surrounded by relatively
non-flammable Subtropical Thicket, Forest and Nama Karoo.
Nama-Karoo
The Nama-Karoo covers
most of the vast central plateau region of the Western and
Northern Cape Provinces. The area forms an ecotone or
transition between the Cape flora to the south, and the
tropical savanna in the north. Many of the plant species of
the Nama-Karoo also occur in the savanna, grassland,
succulent Karoo and fynbos biomes. Species that occur in the
Nama-Karoo include the sweet-thorn (Acacia karroo), stone
plant (Lithops ruschiorum) and blue Karoo daisy (Felicia
australis). A rich variety of rodents and reptiles occur in
the Nama-Karoo.
Forest
The forests of South
Africa include the indigenous evergreen and semi-deciduous
closed forests of the coastal lowlands and escarpment slopes
and cover only about 0.25% of the land area. With a few
exceptions such as the forests of the Knysna area and the
KwaZulu-Natal coastal dune systems, forests are small,
usually occupying less than 1 000 ha. These forests amount
to little more than patches scattered through the higher
rainfall areas. The total area of forests in South Africa is
probably less than 2 000 km2. The forest
structure results in reduced light levels in the area
beneath the canopy where species such as tree ferns are
common. Typical mammals include the bushbuck (Tragelaphus
scriptus) and bush pig (Potamochoerus porcus) and typical
birds include the Knysna lourie (Tauraco corythaix). Despite
the small land surface area that they occupy, forests have
relatively high species richness. Only fynbos exceeds the
species richness found in forests.
Alexandria forest (Acocks
Veld Type No. 2) or Indian Ocean forest can be distinguished
from other forest types by the relatively low percentage of
shade-loving trees in the species composition, and is thus
phytogeographically distinct from forests in other regions.
This veld type is highly threatened with only about 5 % of
the original extent of the veld type presently conserved
under formal conservation. Woody Cape Nature Reserve
represents more than 90% of the Alexandria forest veld type
conserved. The Alexandria forest receives the highest
rainfall in the AENP, about 600-700 mm per year.
Afro-montane forest
Afro-montane forest
is found in the ravines and valleys in several sections
of the park Wetlands
The term "wetlands" groups together a wide range of inland
and coastal habitats - from mountain sponges and midland
marshes to swamp forests and estuaries - linked by rivers
and streams. These wetlands share common and important
functions in river catchments by providing a regular water
supply, by filtering the water naturally, by reducing the
effects of floods and droughts, and by providing a vital
wildlife habitat and superb recreational areas for people.
Most wetlands are characterised by a high water table,
water-carrying soil and hydrophytes (water-loving plants),
but in semi-arid Southern Africa there are numerous pans
that support few if any hydrophytes and that may contain
shallow water only once in five or more years.
Wetlands play an
important role in maintaining biodiversity since they
support an extraordinary variety of plant and birdlife e.g.
the red bishop (Euplectes orix), the South African shelduck
(Tadorna cana), insects, mammals, reptiles, amphibians, e.g.
the striped stream frog (Strongylopus fasciatus), fish and
invertebrate species. Wetland plants such as the bulrush (Typha
capensis), play an important role in the healthy functioning
of a wetland ecosystem by generating organic matter, the
primary element for any foodweb. They also provide the soil
and water with oxygen, prevent erosion and serve as a filter
that purifies the water. These plants provide food, shelter
and breeding sites for many birds and aquatic animals such
as the hippopotamus.
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