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Love your grasslands ...
The grasslands of the Witwatersrand ridge are very much on our doorstep.
South Africa in general is a botanical hotspot; not only is it rich in numbers of plant species (c.24000) but about 70% of these occur nowhere else in the world – they are ‘endemic’.
Grassland that has developed naturally, and has never been disturbed by man’s activity, sustains a high number of species of all types, plant and animal. That is, it has a very high biodiversity. Far from grasslands in South Africa being just ‘oceans of grass’ about 6 out of 10 grassland plants are ‘non grass’ species. Alas, this ‘primary grassland’ is a fairly rare vegetation type worldwide.
This is because grasslands represent a particularly congenial habitat for man. Their climate is generally mild (cool to cold winter nights are the worst of their climatic extremes). Moreover, the staple foods of agricultural man (as opposed to his early hunter-gatherers) are grasses – or cereal crops, as we call them now. No wonder, therefore, that mankind’s food grows best in grassland areas, and no wonder that very few grassland areas remain unexploited, and in their natural state.
On South Africa’s highveld, the Suikerbosrand Nature Reserve
is probably the only substantial remnant of natural grassland that remains, there are no areas of comparable size left to conserve.
Overall about 60% of South Africa’s natural grassland has been destroyed and a mere 2,4% conserved. Worse, some sub-types of grassland have suffered far greater destruction and far less conservation. Afforestation poses the greatest threat to grasslands. Though the forestry industry makes much of its preservation of natural woodland, it continues to plough up pristine grassland.
Highveld grassland differs from bushveld grassland (which commences abruptly just north of the Magaliesberg
) and from fynbos in that it is a very stable habitat. For example, annual plants are comparatively rare, and in general grassland species place little reliance on seeds to ensure their annual regeneration; virtually all of them are perennial. (However, they do produce seeds; these serve as an ‘insurance policy’ for the plants, as well as being a food resource for other creatures). Because grassland plants are adapted to stability, the habitat is very susceptible to major disturbances like ploughing. One reason is that, being stable, grassland has not evolved the necessary pioneer species that lie dormant in seed form ready to colonise disturbed patches when they are created. Thus, it is the complete opposite to Namaqualand, where disturbance encourages survival of the famous, colourful, annual species. Thus species richness in highveld grassland reflects a lack of disturbance. Grassland tends to support pioneer species only in wetlands and riverine fringes, for these areas have always been subject to frequent natural disturbance.
Grassland differs from fynbos in that frequent (even annual) burning is not necessarily deleterious. (Fynbos degrades if burnt more often than every 5-7 years). This is because highveld plants have had to adapt to frequent natural fires that happen as a result of the very high rate of lightning strikes (one of the highest rates in the world). It’s thus not surprising (though botanists have only recently found out) that smoke is as much a growth/germination trigger in grassland (and montane grassland), as it is in fynbos.
In fact, not only frequent burning but also grazing (now simulated by domestic stock) is essential components of a healthy, well-developed highveld grassland. Interestingly mowing does not appear to be an effective substitute for grazing.