Faculty of Science
School of Animal,Plants and Enviromental Science
0204279a
craigm.kznwildlife.com / Fire is a key determinant of savanna dynamics, and would thus have a major influence on the
vegetation dynamics of Mkuzi Game Reserve. Given this logic, it is an important and
commonly used management tool in this reserve. Its main uses in the reserve are for either
removing moribund material or for reducing woody plant encroachment, both of which
normally entail dry season burns. As a consequence, fire often results in a green flush of
vegetation that is highly favoured by grazing herbivores. A further management goal is
maintaining or improving biological diversity by promoting vegetation heterogeneity.
Current policy prescribes this should be achieved through point-source ignitions rather than
by block-burning, which was the earlier practice.
This study explores spatial and temporal fire patterns at a landscape scale in Mkuzi Game
Reserve using Geographic Information Systems (GIS). Much of our understanding of the
dynamics of fire has previously been determined at a plot scale and scaling up of these
insights to a landscape scale is problematic, hence this project aimed to contribute to our
understanding of the dynamics of fire at a landscape scale. The study also specifically
examined how the fire regime in the reserve has changed with a change in the burning
philosophy and strategy, namely from block burning to the point source ignition (PSI)
strategy, which began to be implemented in the mid-1980's.
Fire frequency was related to both geological type and vegetation type. The fact that geology
was related to fire frequency was not surprising because the relationship between geology and
vegetation in the reserve has previously been established. The varying amount of herbaceous
material per vegetation type apparently influenced fire frequency. Spatial variation in fire
frequency was also positively related to rainfall variation over the reserve, while the total area
burnt per annum was positively related to the preceding wet season rainfall, but not for years
with a high dry season rainfall. The influence of rainfall on grass production and thus fuel
load explained these relationships. In addition, there was some evidence of a carry over
effect of rainfall where the previous wet season rainfall together with the preceding wet
season rainfall influenced total annual area burnt, but this was only significant for years when
dry season rainfall was low. Contrary to an expected negative influence, dry season rainfall
had no effect on the total annual area burnt. Grazer biomass had a significant limiting effect
on fire frequency over the reserve (spatially), most likely due to consumption of herbaceous
ii
material, but there was no relationship between grazer biomass and total annual area burnt
(temporally). Dry season burns were significantly larger than wet season burns and can be
attributed to the more favourable fuel condition during the dry season. Intense burns were
also generally larger than the cooler burns, namely those rated as patchy/very patchy and
clean. This was mainly attributed to a high fuel load which is critical for intense fires but also
positively influences the spread of fire.
The comparison of the block burning strategy and the point source ignition (PSI) strategy
showed that fire frequency was greater during the PSI burning period than during the block
burning period. The total area burnt per annum was greater during the PSI burning period
than during the block burning period, but individual burn sizes were not significantly
different between the two strategies. Evidence showed that individual burns that occurred
during the PSI period had boundaries that were more irregular than those of block burns.
Fires were most common during the dry season for both burning strategies, but the proportion
of the burns that occurred during the dry season was greater for the PSI burning period than
for the block burning period. Evidence also showed that a much greater emphasis was put on
applying dry season prescribed burns during the PSI period than during the block burning
period. A greater effort was also made during the PSI period to burn firebreaks, which were
only implemented during the dry season. Arson fires (started deliberately or accidentally by
neighbours) were more common during the block burning period than during the PSI period,
while under both burning strategies, they were more common during the dry season than the
wet season. There was no distinguishable difference in the burn intensity patterns between
block and PSI burning, that is, the proportions of burns in the different burn intensity classes
were not significantly different between the two burning strategies. Although the
contribution of the individual fire barrier types showed some change with a change from
block burning to a PSI strategy, the combined contribution of natural barriers did not increase,
and that of management barriers did not decrease, as would have been expected. In addition,
natural and management barriers were apparently of equivalent importance during both
burning strategies.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/1777 |
| Date | 16 November 2006 |
| Creators | Mulqueeny, Craig |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 2384712 bytes, application/pdf, application/pdf |
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