African bush. 불더스 비취(Boulders beach). 케이프타운(Cape town)

African bush. 불더스 비취(Boulders beach).

케이프타운(Cape town). 남아공(South Africa)

 

Manitoka Myoporum serratum (Australia)

 

a patch of african bush

You are surrounded by alien trees: invasive Manitoka and Rooikrans from Australia.

 

When like threatens like

Plants from other Mediterranean climate regions are the greatest threat to fynbos and

thicket biodiversity in the Cape floral Kingdom.

Most invasive aliens were introduced for forestry, as ornamental plants and dune

stabilisation.

 

Why are these foreigners so unwelcome ?

Alien invaders from other Mediterranean regions such as southwest Australis are

adapted to similar environmental conditions as those found at the Cape: infertile soils,

summer droughts and fire.

Invaders in coastal thicket can also survive sea spray and wind.

These invasives are free from their natural enemies, which normally control them in

their native countries.

Removed from their home environment, these invasive plants spread like an

aggressive green cancer.

Alien plants are being removed gradually at Boulders so as to avoid disturbing

penguin breeding habitat.

 

Attacking biodiversity

Woody alien species change the environment by:

● Out-competing native plants by producing more seed and growing more rapidly.

    Rapid growth allows them to shade out local, sun-loving species.

● Causing more frequent fires that burn at higher temperatures thatn indigenous

    vegetation, and for longer. This kills the seeds of some fynbos species while

    causing alien seeds to germinate.

● Stabilising coastal sand dunes, thereby destroying the habitat of many local dune

    specialists.

● Using more water due to their greater size and broader leaves, thus serving as

    "windmills" that suck precious water from streams and marshes.

 

The eradication of invasive alien plant species is a national priority in South Africa.

 

 

v

Rooikrans Acacia cyclops (Australia)

 

Mountain fynbos with Protea cynaroides in foreground

 

 

The Cape Floral Kingdom

The Cape Floral Kingdom (CFK) is the smallest, most species-rich and most threatened of the world's six floral kingdoms

The CFK covers only 0.04 % of the Earth's surface (90000 square kilometres), but is home to about 9000 plant species - a regional diversity that rivals that of some tropical rainforests.

 

Two vegetation types - fynbos and renosterveld - contain most of the floral diversity in this globally unique region. Natural vegetation in the cultivated lowland areas of the CFK is highly threatened by human activities and invasive alien plants.

Incredibly, 69% of fynbos plant species occur nowhere else on earth. The Cape Peninsula has 2286 plant species of which about 150 are not found elsewhere.

Fynbos is like an ecological island isolated from the rest of Africa by its unique environmental conditions: infertile soils, summer droughts and intense fires with long inter-fire periods of 5-15 years.

Proteas, ericas, reed-like restios and geophytes (bulbous plants) are characteristic fynbos plants. Renosterveld occurs on richer soils and used to support large animals such as elephant and lion in pre-colonial times.

Fynbos is the dominant vegetation of the Cape Peninsula National Park.

At the coast, dune thicket can replace fynbos where fires are less frequent and sands contain fine seashell fragments and leaf litter.

 

 

 

 

The fynbos of the Cape Peninsula's mountains is replaced by dune thicket at Boulders

 

Thicket habitat

Thicket vegetation is dominated by dense, evergreen shrubs that are often thorny and

fruit-bearing. Climbers are common in areas of tall vegetation.

 

Unlike fynbos, thicket occurs on more fertile, fire-protected sites such as coastal

dunes (hence the Afrikaans name, "strandveld"), in river valleys and around rocky

outcrops.

The Boulders coastline is the ideal fefuge for thicket species.

 

Penguin shelter

African Penguins prefer breeding where they are sheltered against hot weather and

predators like Kelp Gulls.

 

Boulders represents high quality real estate for penguins - its bushes, deep sand and rock crevices offer a variety of nesting options.

 

The only penguins that nest in the open are in the densest areas of the colony -

exposed to predators, they seek safety in numbers. Most of the penguins at Boulders

nest under shrubs.

 

Wind-pruning

Boulders is one of a few sites on the shores of False Bay where thicket has managed to escape the worst effects of the wind and grow into a small forest.

 

 

Notorious for its summertime south-easterly winds, False Bay is swept by gales for

about 100 days a year.

 

The battering and dehydrating winds also carry vast amounts of salt spray that are

deposited on plants.

 

The drying and stunting effects of wind and salt literally "prunes" seaside vegetation

into an even hedge.

 

Plants that are best able to cope with wind exposure are those which have thick,

leathery leaves.

 

It is only in sheltered, well-watered coastal environments - for example, Boulders -

that clumps of thicket can turn into small forests. Some species, such as milkwoods,

can reach a height of 3m.

 

 

Blue kuni-bush Rhus glauca

 

Camphor tree

Tarchonanthus camphoratus

 

Mature dune thicket with candelabra flowers Brunsvigia orientalis

in foreground

 

Sea buarri Euclea racemosa

 

Ideal nesting habitat for penguins

 

Sea, seeds and fire

Dune thicket owes its existence to the sea for another reason.

 

Many of the nutrients in the soil come from the nutrient-rich waters of False Bay.

The nutrients are brought to shore by the south-east wind, and by the movement of animals (such as penguins) between sea and land.

 

Fruit-eating birds are important seed dispersers in thicket.

 

In contrast with fynbos, many thicket plants have fleshy fruits.

 

Birds deposit the seeds under perches in established bushes, giving rise to dense,

fire-resistant clumps of thicket vegetation.

 

 

Redwinged Starling

Onycholgnathus morio

 

Spotted Mousebird

Colius striathus

 

Cape Bulbul

Pycnonotus capensis

 

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