LIFE ON EARTH

BIODIVERSITY

Regional Habitats

Biomes, Bioregions and Vegetation-Types

Regional habitats are associated with broad-scale biome and bioregion ecological units influenced by the climate and topography of a region. The biosphere lies at the boundary of two distinct South African Biomes – grassland and savanna, with remnants of a third biome – afromontane forest.

Slide 93 - biomes

Imbedded in each biome are assemblages of plants that are likely found together in an area, at a finer scale than the biome. These assemblages are influenced by local geology, soil type, hydrology and micro-climate, and have been classified as vegetation types (VT) by Mucina and Rutherford. There are 435 vegetation types classified for South Africa, of which 15 are found in the Magaliesberg Biosphere. These are highlighted in the descriptions of the biomes in which they occur.

Savanna Biome

The Savanna biome covers the Central Bushveld Bioregion, to which seven of the vegetation-types of the Biosphere belong. The bioregion encompasses the plains to the north of the Magaliesberg (Marikana Thornveld and Norite Koppies Bushveld VT), the Moot valley (Moot Plains Bushveld VT) opening out to the western edge of the biosphere (Zeerust Thornveld VT) and on the mountains and ridges throughout (Gold Reef Mountain Bushveld, Gauteng Shale Mountain Bushveld and Andesite Mountain Bushveld VT).

Typically this central bushveld bioregion is represented by woody vegetation and a grass dominated herbaceous layer. Depending on local conditions, trees form semi-open to closed thickets or woodlands, and can range from short deciduous bush cover to a medium-tall +5m tree cover of deciduous and evergreen trees. Some vegetation types are dominated by thorny species (Acacia sp).

Slide 89 – Moot Plains Bushveld

None of the Norite Koppies Bushveld VT is formally protected. It mostly occurs to the north of the biosphere, with 4% of its extent within the biosphere transition zone.  It is under severe threat from granite mining, which strips the entire surface and tops of the koppies, leaving them completely degraded.

Grassland Biome

The grassland bioregion that predominates in the Biosphere is Mesic Highveld Grassland. Characterised by a Mean Annual Precipitation above 650mm and frost, a thick cover of sourveld grass species dominate in the summer, followed by a dormant winter period. The high diversity of forbs found in grasslands, is what makes grasslands an important biome for species richness (Mucina & Rutherford, 2010). Rocky habitats show a diversity of woody species, which occur in the form of scattered shrub groups or solitary small trees. Riverine habitats contain frost tolerant and deciduous woody species. 

Five grassland types that are distinguished by geology, soils, elevation topography and rainfall, occur in the biosphere (Carletonville Dolomite Grassland, Egoli Granite Grassland, Rand Highveld Grassland, Waterberg Magaliesberg Summit Sourveld, Soweto Grassland VT) . Notably, Waterberg Magaliesberg Summit Sourveld has a unique set of environmental conditions that support biogeographically important taxa and some endemic floral species (Mucina & Rutherford, 2010 ; Gill & Engelbrecht, 2012).

The Crocodile River Reserve, and some of the Cradle of Humankind World Heritage site, contains much of the remaining Egoli Granite Grassland outside of urban Johannesburg. This vegetation type is highly vulnerable to urban expansion and the CCR and Gauteng Biodiversity Stewardship authority have been working towards its protection through the establishment of the reserve, which is soon to be promulgated.

Forest Biome

The Northern Afro temperate Forest vegetation type forms part of the Zonal and Intrazonal Forests Bioregion. It is a grouping of inland isolated forest patches of the northern Highveld occurring in low-escarpment kloofs and ridges, usually at an attitude of 1450-1900m above sea level. The Magaliesberg forests mark the western most occurrence of this vegetation type (Mucina & Rutherford, 2010).

In the context of the Biosphere these forests are found in the kloofs and valleys along the northern slopes of the Magaliesberg. Vegetation is of afromontane origin, and is relatively species poor for a forest biome (Mucina & Rutherford, 2010). However, these forests support some biodiversity that does not occur in savanna nor grassland systems.

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FAUNA AND FLORA

The unique assemblage of flora and associated fauna of the Magaliesberg is well recognised, and a biosphere status for the region was conceived due to the large number of species represented in the area, which includes a number of threatened red and orange list species.

Today, over 500 flowering plants are described in The Field guide to Wild Flowers of the Magaliesberg by Gill and Engelbrecht, 2012.

A checklist of birds of the Magaliesberg, by Wesson & Balt (2014), totals 434 species, and the Magaliesberg and Witwatersberg areas (more than 62% of the Biosphere area) is identified as an Important Bird Area, by Birdlife South Africa meaning that it contains species of global conservation concern and supports large numbers of migratory water birds on a regular basis.

The significant biodiversity of the region has been recorded through scientific investigation for many years. Botanical and zoological collection and hunting expeditions around the Magaliesberg from 1835 onwards into the twentieth century identified and described a number of new species to science. Notably, these include the Sable Antelope and two endemic floras of the mountains.

Puffback

The Cape Vulture (Gyps coprotheres), is the subject of ongoing research and monitoring in the Magaliesberg (Whittington-Jones, et al., 2014) and it has become somewhat of a flagship species for the region. The NGO, Vulpro, leads the way in the conservation, awareness and rehabilitation of Africa’s Vultures from their operation which is located in the biosphere.

SLIDE 84 – KLOOFS AND VULTURES

Monitoring of the movements of leopard (Panthera pardus) and brown hyaena (Hyaena brunnea) in the Magaliesberg and The Cradle of Humankind World Heritage site, are ongoing projects.

strawberry leopard (FROM PAUL)
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