Marloth Park Management Plan. - Nkomazi Local Municipality

Bush control
Causes for bush encroachment are manifold. One cause is the misuse of fire. Drought and
human disturbance together with the absence of game migration and the absence of tree
damage by animals, such as elephant, are more likely to cause bush encroachment. The most
important reason for bush encroached areas in southern Africa, is the imbalance in stocking of
the different feeding groups. High stocking rates of grazers, and low stocking rates of
browsers, results in over-utilisation of the grass sward.
With high stocking rates of browsers, young woody plant seedlings cannot develop into
mature shrubs and trees, due to severe over-utilisation. Too low stocking rates of browsers
will result in an abundance of trees and shrubs that will eventually reach densities that
suppress the maintenance and/or development of the grass stratum. Passive management
alone, such as the introduction of large browsers like elephant Loxodonta africana and black
rhinoceros Diceros bicornis can be considered, but does not seem sufficient in correcting
these imbalances. Furthermore, the introduction of these animals is limited to larger
conservations areas only. Correcting these historic imbalances, usually attributed to cattle
ranching, cannot effectively be corrected by adjusting the stocking rates, and active
management will be required. Manipulation of the browser population is considered a tool for
long-term bush control.
Fire as a means of active bush control is of questionable use. Furthermore, the use of fire is
not advised in sweet veld areas, and other measures need to be taken. Mechanical methods
such as clearing bush with chains or bulldozers are effective but cost inhibitive. Even more of
a disadvantage with this method of bush clearing is the soil compaction and disturbance of the
grass layer. Where the grass layer is already decimated, this method is not recommended.
Another mechanical method is ring-barking or girdling. This method causes death of trees
within 1 to 3 years through removal of the bark around the trunk. Chemical treatment of the
exposed trunk area enhances the process and inhibits coppicing. This method is not feasible
for multi-stemmed tree species.
Alternatively, the manual slashing, felling and chopping down of trees is the only mechanical
means of removing encroaching woody plants. Serviceable tools are an axe, a hand-held or
tractor driven chainsaw, a circular saw or a brush cutter. With a tractor driven circular chain
saw up to 2.4 ha can be cleared in one day. Mechanical bush clearing is best combined with
chemical treatment, in this case stump treatment with an herbicide. Stem notching and
application of an herbicide is not feasible with multi-stemmed trees.
© Ecological Associates/ Marloth Park 97