Okavango Delta Management Plan - Ramsar Convention on Wetlands

ecause surface head fires cause least damage to the grass sward and crown fires can cause
maximum damage to woody vegetation when fire is used to control bush encroachment;
ii. When burning to remove moribund and/or unacceptable grass material a cool fire of 2 000 kJ/s/m is necessary. This can be achieved when the grass fuel load is >4 000 kg/ha,
the air temperature is >25°C and the relative humidity 13 mm. When burning to control the
encroachment of undesirable plants like bush encroachment, a high intensity fire is required and it is
recommended that this be applied before the first spring rains in August/September when it is
extremely hot and dry.
iv. In the case of burning in the Seasonal Swamps where the growth of the vegetation is generally
influenced by the annual flood waters entering the <strong>Delta</strong> the ideal burning window for removing
moribund and/or unpalatable grass material is during the period May to July, applying the fires
when the grass sward is dormant before the flood waters start rising.
v. If it should be necessary to reduce the growth of trees and shrubs in the Seasonal Swamps then
burning must be applied later in the winter during August/September when it is extremely hot and
dry thereby ensuring high intensity fires necessary to control encroaching trees and shrubs.
vi. When burning to remove moribund and/or unacceptable grass material the frequency of burning
will depend upon the accumulation rate of excess grass litter. Field experience indicates that
burning is necessary for this reason when the grass fuel load exceeds 4 000 kg/ha and therefore the
frequency of burning of areas in the Seasonal Swamps and the Acacia, Burkea and Mopane
Woodlands can be determined using this criterion.
vii. In order to prevent overgrazing it is important to ensure that the burnt area exceeds the short term
forage requirements of the grazing animals that are attracted to the highly palatable and nutritious
re-growth that develops after a burn i.e. burn relatively large areas at any one time. Another
effective strategy is to apply a series of patch burns at regular intervals throughout the duration of
the burning window during the dormant season. This has the effect of attracting the grazing animals
to the newly burnt areas after the different fires thereby spreading the impact of grazing over the
entire burnt area and avoiding the detrimental effects of heavy continuous grazing after the burns.
5.2.7.2 Practical Application of Controlled Burning
In the practical application, a controlled burning program should be guided by the
following factors (ODMP – Fire <strong>Management</strong> <strong>Plan</strong>, 2006):
a) The weather conditions as described and assessed using the recommended Fire
Danger Rating System should be appropriate for burning.
b) Appropriate burning procedures for the application of the controlled burn
should be used i.e. applying a block burn or a patch mosaic burn
c) Adequate and appropriate firebreaks for the area being burnt should be
provided or be in place.
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