How really nice to read something by someone who cares and who understands. Well done Lood Wentzel.
We need YOUR kind of comment to educate those people who are currently uninformed but who truly want to know the facts.
The normal Veld Fires you get in Kruger National Park are NOT “man-made” (“or unnatural”). Veld Fires are a product of this “too many elephants” story, too.
For veld fires to burn there must be combustible material in the habitat. For fires to burn HOTLY, however, there must be LOTS of combustible material in the habitat… and that means lots of grass (or dead woody material)and dead woody material is normally a product of the previous years’ fires. Grass, however, is the most obvious and the most abundant combustible material in wild veld fires…. which, when driven by a wind, rages across vast stretches of grassland during the dry season (doing a lot damaged to woody plants).
Habitats, however, grow naturally towards their state of “vegetative CLIMAX” – and a habitat’s climax is the maximum state of growth that the vegetation a particular habitat can grow to.
A grassland habitat, for example – IF GRASSLAND is truly the climax vegetation type – will grow to the maximum state of grassland habitats (in terms of grass species and grass mass) which that particular ecosystem is designed to accommodate.
AND, you can (naturally) have pockets of grassland growing inside what is otherwise a woodland habitat complex. This will give you a mosaic of different habitat types all growing in the same general area (depending on soil type; temperature regime and rainfall). And all caused or influenced by fire.
Frost or no frost etc affects a grassland, too. Heavy frosts, for example kill off many tree-species saplings at the height of winter – and this fact favours the grass.
Young trees are competitors for the grass – taking both nutrients and moisture (in the soil) away from each other (because they have to share the same soil nutrients and soil water).
This is why many low-lying pieces of ground (vleis) remain free of trees. The frost kills off the saplings (or renders them weak); and when the grass burns it kills off the young trees completely.
This is why many vlei systems never have trees.
Above all, however, grassland needs full and open exposure to sunlight.
So, one of the prerequisites of a healthy grassland is access to maximum sunlight. When sunlight is deficient grass will not grow – or it won’t grow vigorously – OR only ‘tender’ broad-leafed grasses (grass that like an modicum of shade during the heat of the day), will be found growing in the shade of a tree.
Fire tends to keep grasslands growing as grasslands, because many grasses are pretty fire-resistant and they will burn hotly when fires come along – the intense heat killing off all the young woody plants that are struggling to grow out (i.e. those that are striving to return to a woodland climax state).
But fire doesn’t damage these kinds of veld grasses – because their perennial root stock is protected from the heat because its root stock is under the ground.
The botanists will tell you that fire created the savannah habitat (treed/grasslands); and fire maintains it in that state.
A very large part of Kruger National Park is deciduous woodland climax – which, when the big top-canopy trees were in their climax state, cast considerable shade below their canopies. These semi-shade conditions were ideal for a whole host of understory plants that cannot grow in direct sunlight (they grow in naturally mottled semi-shade conditions under big trees). The understory plants, in “their” shade cast even greater shade beneath – and thus the conditions become perfect for a very diverse and complex understory habitat.
This, altogether, therefore, reduced the penetration of the sun’s hot and bright rays to ground level – so much so, that grass could NOT grow in those conditions at all.
When the elephant numbers became “excessive” (i.e. too many elephants for the habitats to sustainably carry) they removed “more than” 95 percent of the deciduous trees that made up the deciduous woodland complex. And once the top canopy trees were gone, 100 percent of understory habitats disappeared, too.
Thus, where there were deciduous woodlands all over Kruger National Park before the elephants became too plentiful – when they BECAME “too many” – they created a new situation where sunlight was able to penetrate to the ground everywhere.
This promoted grass growth where no grass ever grow before…. and that set a perpetual motion syndrome in place there the grass burned – every year hotter and hotter. The hot fires killed whatever tree sapling were trying to grow – which promoted yet more grass growth – so the vicious circle began.
The hottest fires in Kruger National Park, however, are constructed by man.
They occur when man decides that he wants to burn off a “block of land” (such a block of country that is surrounded on all sides by a system of roads).
In the past it has been common practice for game rangers to travel all round such a block setting fire to the grass at the inner road-side. In this way the fire burns inwardly on itself from the surrounding perimeter. As the grass starts to burn more and more fiercely – from all sides all around – it sucks in air from the surrounding country so the fire tends to act like a funnel – or a chimney – and it becomes self-generating. The core area of the fire, therefore, acting like a furnace generates huge temperatures rising towards the burning centre of the chimney which incinerates all plants and animals that have been caught inside the chimney.
We must never forget, however, that if it wasn’t for the fact that:
(1) there are too many elephants in Kruger National Park, more than 95 percent of the top canopy trees in the woodlands would not have been removed;
(2) that the shade once cast be those trees (and their undergrowth) used to stop grass from growing on the ground beneath them; and
(3) that being so, fiercely hot veld fires would not be possible.
Those people, therefore, who separate direct tree damage caused by too many elephants from consequential tree (and sapling) damage caused by hot veld-fires, are not “seeing the bigger picture”.
It is the fact that there are too many elephants in Kruger National Park which is causing the very damaging hot fires, too!