Savanna Fire Ignition Research Experiment
(SavFIRE): Effects of point vs perimeter
ignitions on fire mosaics
Navashni Govender1, Winston Trollope2, Chris Austin3, Alex Held4
1
Scientific Services, Kruger National Park, South Africa ([email protected]),
2
University of Fort Hare, South Africa, 3Wildland Fire Training Center Africa, South
Africa, 4Chair AfriFireNet and www.workingonfire.org, South Africa
A recent development in the use of fire in large conservation areas like the Kruger National
Park, is the hypothesis that the desired biodiversity of the overall ecosystem will be promoted
by controlled burns applied as point ignitions instead of perimeter ignitions (block burns). At
this stage benefits associated with controlled burns applied as point ignitions are untested
hypotheses. An urgent necessity thus exists to determine whether point ignitions do in fact
result in a greater fire mosaic of different types and intensities of fires compared to areas burnt
as perimeter ignitions and at what scale. Preliminary results from treatments (500ha vs 2000ha)
suggest that fire mosaic patterns are most strongly influenced by the prevailing weather
conditions at the time of ignition. This project attempts to determine the threshold area and
weather conditions required for similar fire patterns and mosaics resulting from a point ignition
and perimeter ignition. It is envisioned that such an investigation would promote the improved
use of controlled burning in conservation areas, achieving their objective of promoting
biodiversity in the national parks system and wild life areas in South Africa thereby benefiting
ecotourism and its positive effects on poverty relief.
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
Introduction
In 2002 the Kruger National Park, changed their fire policy from a lightning driven system
to that of an Integrated Fire Management System (Biggs, 2002). This new fire policy
incorporates all three dominant ignition sources in KNP (rangers, lightning and transmigrant) as well as integrating elements of range condition and patch mosaic burning. The
objective of this burning system is to maintain biodiversity through realistically coexisting with the reality of unplanned burns caused by illegal trans-migrants from
neighbouring countries and other causes. An important component of this new system is
the application of patch mosaic burns as point ignitions early in the fire season (April –
June), thereby creating a mosaic of burnt and unburnt areas and breaking up the fuel load
in order to prevent the larger runaway wild fires late in the fire season (July – September).
The policy is also based on an assumption that burning patterns of fires are an effective
surrogate measure of biodiversity i.e. the more diverse the burning patterns the greater the
biodiversity (Parr & Andersen, 2006). It is therefore believed that controlled burns applied
as point ignitions instead of perimeter ignitions (block burns) will promote biodiversity of
the ecosystem. This is because it is postulated that point ignitions will result in greater fire
mosaic developing as a result of greater variation in fire conditions (i.e. longer time period
of fires, greater variation in temperature, humidity, wind speed and direction, type of fire
and intensity). At this stage all these perceived benefits of controlled burns applied as
point ignitions are untested hypotheses and an urgent necessity exists to determine whether
they do in fact result in greater fire mosaic of different types and intensities of fires
compared to areas burnt as perimeter ignitions and therefore promote biodiversity.
SavFIRE (Savanna Fire Ignition Research Experiment) is a burning trial that is being
conducted in the Kruger National Park, South Africa. The primary objective of the trial is
to test the hypothesis that the behaviour and resultant fire mosaic of controlled burns
applied as point and perimeter ignitions, is significantly different when applied to small
areas, but becomes increasingly similar as the areas being burnt increases in size, until a
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
threshold is reached greater than which the fire behaviour and fire mosaics are not
significantly different.
However, an added factor is that fires ignited as point ignitions are more hazardous and
difficult to control compared to perimeter ignitions which are applied to areas with
prepared firebreaks. If the same diverse fire mosaic can be obtained by applying perimeter
ignitions to areas above a certain threshold size this would be an attractive ignition
procedure for fire managers within conservation areas who are currently mandated to
maintain and promote biodiversity.
Current fire management strategies are aimed to introduce increased fire variability
(frequency, intensity and type) into the landscape through the use of dynamic fire mosaics
across space and time (Brockett et. al 2001). It is therefore firmly believed that conducting
this fire research will make a highly significant practical contribution to fire management,
by promoting the improved use of controlled burning within conservation areas.
Study site
The Kruger National Park is one of the largest proclaimed and officially protected natural
areas in the world. Established in 1926, the park is approximately 1 898 458 ha, occupying
almost 2.5 percent of the total land surface area in South Africa (Figure 1). It is situated in
the north-eastern region of South Africa and is separated from adjoining Mozambique by
the Lebombo mountain range in the east and from Zimbabwe in the north by the Limpopo
valley. Mean average rainfall for the entire park is approximately 500 mm, but varies
around 350 mm in the north to around 750 mm in the south. The park is also distinctively
divided in two by its geology, with granitic sandy soils on the western half of the park and
basaltic clay soils on the eastern half. The vegetation of the park is dominated by trees
from the Acacia, Combretum, Sclerocarya and Colophospermum genera. The flora of the
park comprises +/- 2000 taxa, including over 400 tree and shrub species, and over 220
grasses. The fauna of the park includes 148 mammal and +/- 500 bird species.
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
N
W
E
S
Punda Maria
â
Shingwedzi
â
Mopaniâ
Letaba
â
Satara
â Main Tourist Camps
Gertenbach Landscapes
Colophospermum mopane shrubveld on basalt
Combretum collinum / Combretum zeyheri woodland
Lowveld Sour Bushveld of Pretoriuskop
Sclerocarya birrea subspecies caffra /Acacia nigrescens savanna
Major Rivers
Skukuza
â
Lower Sabieâ
20
0
20
40
60 Kilometers
Adapted from Biggs, et.al.2003
Figure 1: Illustrating the distribution of the four major vegetation types within the
Kruger National Park and the location of the KNP within South Africa.
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
The SavFIRE project will be conducted in three of the four major vegetation types as
described by Gertenbach, 1983 in the KNP (Table 1).
Table 1. Description of the three landscapes in the Kruger National Park, South
Africa, where the SavFIRE project will be conducted.
Landscape
Dominant vegetation
type
Underlying
geology
M ean annual
rainfall
(mm)
M ooiplaas
Satara
Pretoriuskop
Savanna dominated by
dense low (1-2m)
mopane
(Colophospermum
mopane) trees
Savanna dominated by
scattered tall (10-15m)
M arula (Sclerocarya
birrea) and knobthorn
(Acacia nigrescens) trees
Savanna dominated by
dense tall (10-15m)
Terminalia sericea trees
Altitude
range
(m)
Basalt
496
300-340
Basalt
544
240-320
Granite
737
560-640
Method
Point & perimeter ignitions will be applied to paired areas ranging from 500, 2000 and
3000 hectares under similar plant fuel (> 4000 kg/ha), fuel moisture (fully cured, < 20%),
weather conditions (air temperature, ± 25 0C, RH, ± 40 % and wind speed, ± 10 km/h) and
fire danger index ± 50. This method will be replication in three landscapes in the KNP
(Table 1).
The first phase of SavFIRE was conducted as a “trial run” in savanna dominated by
mopane (Colophospermum mopane) trees in October, 2006. This was a means of
identifying and dealing with the logistical challenges associated with such a large field
scale burning trial thereby providing essential experience for the implementation of the
remainder of the trial. The treatment application comprised burning two relatively small
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
areas (500 and 2000 ha), igniting them simultaneously with point and perimeter ignitions
(Figure 2). Application of all fire treatment is undertaken by the Working on Fire
Organization.
A visual description of the resultant fire patterns of the point and perimeter ignition burns
applied to the two different areas is provided by the aerial photographs that were taken
from the Working On Fire spotter aircraft during the application of the fires in the
SavFIRE burning trial. Results will be presented separately for each of the controlled
burns in the different burn blocks.
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
Figure 2: The location and orientation of the “trial run” of SavFIRE that were ignited with
point and perimeter ignitions in the Mopane Veld in the Mooiplaas section of the Kruger
National Park during October, 2006
Results
The resulted presented in this paper only reflect the potential effect of varying weather
conditions on fire mosaics. The two area treatments (500 and 2000 ha) were lit under very
different weather conditions (Table 2), resulting in marked differences in fire mosaics. The
500 ha point and perimeter treatments were burnt in an FDI of 62/65, (classed as orange very dangerous) with a fire intensity of 6041 kJ/s/m. The 2000 ha point and perimeter
treatments were burnt in an FDI of 39, (classed as green - moderate) with a fire intensity of
1733 kJ/s/m.
Table 2: Weather and fuel conditions prevailing at the time of ignition of the
respective treatments.
Ignition
Area
Fuel load
FMC
Air Temp
RH
Wind speed
source
(ha)
(kg/ha)
(%)
(0C)
(%)
(km/h)
Point
500
3252
23
31
32
1.9
65
Perimeter
500
2998
19
34
35
2.0
62
Point
2000
3110
17
27
51
1.2
39
Perimeter
2000
2801
16
26
52
1.1
39
The higher FDI’s and fire intensities of the 500 ha point and perimeter treatments is
indicative of extreme atmospheric conditions (high ambient temperatures and wind
speed and low relative humidity – Table 2) at the time of ignition, that promoted the
rapid combustion of fuel and provide favorable conditions for the development of high
intensity fires and resulted in a clean fire burn with no fire mosaic.
During the application of the 2000 ha point and perimeter treatments, the lower FDI’s
and fire intensities is illustrative of the benign atmospheric conditions (lower ambient
FDI
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
temperatures and wind speeds and higher relative humidity – Table 2) at the time of
ignition. The 2000 ha fires burnt over two days and the diurnal variations in weather
conditions during the course of this burn resulted in a well developed and diverse fire
mosaic of burnt and unburnt areas.
Point Ignition – 500ha
Three point ignitions 20m in length and 600m apart were ignited 450m in from the
northern boundary of the ALPHA 1 burn block (Figure 3.1 & 3.2).
3.1
The point ignitions were ignited when the air temperature was 31.30C, relative
humidity 43.7%, a north to north easterly wind of 1.6 km/h and a percentage grass
curing factor of 100 % yielding an FDI of 51.
3.2
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
However, within an hour the FDI had increased to 61 (very dangerous). These extreme
weather conditions resulted in the point ignitions spreading rapidly sideways as
flanking fires and after 42 minutes had coalesced into a single broad fire front (Figure
3.3).
3.3
This burnt as a rapidly moving high intensity head fire down to the southern point of
the triangular block (Figure 3.4) extinguishing itself against the southern firebreak
after 2 hours after the initial ignition of the point fires (Figure 3.5). The point ignitions
initiated in the burn block burnt uniformly resulting in no development of a fire
mosaic.
3.4
3.5
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
Perimeter Ignition – 500ha
The perimeter ignition commenced with an initial slow moving back fire burning
against the north wind along the southern boundary of the plot (Figure 4.1).
4.1
This was followed by a rapidly moving head fire when the block was ignited with the
wind along the north western and eastern boundaries (Figure 4.2).
4.2
As with the 500ha point ignition, the perimeter fire was ignited under extreme weather
conditions commencing with a FDI of 51 which increased to 61 within an hour and
thereafter 69 after two hours since the initial ignition. These high FDI’s caused the
head fires to develop high rates of spread and extreme fire intensities which resulted in
a clean burn with a uniform fire mosaic (Figures 4.3).
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
4.2
Perimeter Ignition – 2000ha
Following the normal practice to apply perimeter ignitions a back fire was initiated
along the northern and western boundary of the ALPHA 2 burn block (Figure 5.1). At
the initiation of the burn the weather conditions were relatively mild with the air
temperature at 260C, the relative humidity 62%, the wind speed 2.3 km/h and the grass
curing factor of 100 % resulting in an FDI of 37.
5.1
This treatment was ignited late in the afternoon and burnt through the night. The
variations in the weather conditions during the course of this burn (diurnal changes)
resulted in a well developed fire mosaic of burnt and unburnt areas (Figures 5.2 &5.3).
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
5.3
5.2
Point Ignition – 2000ha
The 2000ha point ignition experiment was lit under similar weather condition to the
perimeter ignition which, were relatively mild with the air temperature at 260C, the
relative humidity 62%, the wind 2.3 km/h from the south east and the grass curing
factor of 100 % resulting in an FDI of 37. Initially the three point ignitions burnt as
long tongues (Figure 6.1). A change in wind direction had the effect of coalescing the
three point ignitions into a single fire front that burnt predominantly as a head fire in a
south westerly direction (Figure 6.2).
6.1
6.2
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
Overnight change in wind direction, allowed the northern flank of the fire front
stabilised and continued to burn as a slow moving back fire, in a northerly direction,
resulting in a continuous line of back fire extending across the entire breadth of the
burn block (Figure 6.3).
6.3
Due to the slow rate of spread (0.02m/s) of the fire front, which was now burning as a
backfire and the forecast of extreme fire conditions, the fire line was beaten out
(Figure 6.4), resulting in approximately 1000 ha being burnt in a very desirable fire
mosaic (Figure 6.5).
6.4
6.5
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
Discussion and Conclusion
Given the importance of fire as a key driver in various global biomes, informed fire
management is essential for effective biodiversity management. Throughout the
decades fire management regimes have been based on many paradigms, ranging from
the “balance of nature” paradigm (Mentis & Bailey, 1990) to “upset the balance of
nature” thinking (Parr & Brockett, 1999). Currently conservation fire management
policies promote the importance of variability and flexibility in burning thereby
increasing the patchiness of fire mosaics, heterogeneity and biodiversity (Parr &
Andersen, 2006).
Preliminary results have indicated that prevailing weather conditions (air temperature,
relative humidity and wind speed) during fires have a significant effect on the
development of fire mosaics. By selecting weather conditions that are less extreme
(lower air temperatures and higher relative humidity) one can successfully achieve the
formation of a diverse range of fire mosaics, even at scales of only 2000ha. This is in
contrast to the conclusion by Brockett et al (2001), who suggest that the patch mosaic
burning system involving the use of point ignitions is best suited to large conservation
areas of greater than 20000 ha. Results here indicate that the use of patch mosaic
burning can be used in significantly smaller wildlife conservation areas.
Despite widespread support for the patch mosaics burning as a strategic goal for
biodiversity conservation, conservation managers have struggled to operationalize it
effectively. For example, management plans typically lack the details on the scale and
distribution of patchiness that is considered desirable on and how fire mangers attend
to achieve this patchiness. Without such detail it is unlikely that management aims
will be achieved or that outcomes of management can even be effectively assessed
(Andersen, 1999). Clearly there is much work that needs to be done to elucidate the
intricacies of an effective patch mosaic burning system. This project attempts through
experimental research to develop methods for quantifying scales of achieving
“pryodiversity for biodiversity” by providing clear and detailed operational guidelines
for fire managers.
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held
Acknowledgments
All the members of the SavFIRE team are thanked for the professional manner in
which they performed their duties that ensured the success of this first replication. In
particular the aerial support provided by Mr Egmund van Diyk and the ground staff of
the Working On Fire team led by Mr Bandit Steyn are to be commended for their
complete dedication and expertise in controlling the point and perimeter ignition fires
under extremely challenging weather conditions.
References
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and control. Australian Biologist 12: 63-70.
Biggs, H.C. 2002 Kruger National Park Fire Policy. Internal Document from South
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Biggs, R., Biggs, H.C., Dunne, T.T., Govender, N. & Potgieter, A.L.F. 2003
Experimental burn plot trial in the Kruger National Park: history,
experimental design and suggestions for data analysis. Koedoe 46, 1-15.
Brockett, B.H., Biggs, H.C., & van Wilgen, B.W. 2001. A patch mosaic burning
system for conservation areas in southern African savannas. International
Journal of Wildland Fire 10: 169-183.
Gertenbach, W.P.D. 1983. Landscapes of the Kruger National Park. Koedoe 26: 921.
Mentis, M. T., & A. W. Bailey. 1990 Changing perceptions of fire management in
savanna parks. Journal of the Grassland Society of Southern Africa 7:81–84.
Parr, C. L., & B. H. Brockett. 1999 Patch-mosaic burning: a new paradigm for
savanna fire management in protected areas? Koedoe 42:117–130.
Parr, C.L & Andersen, A.N. 2006 Patch mosaic burning for biodiversity
conservation: A critique of the pyrodiversity paradigm. Conservation
Biology 20: 1610 – 1619.
Regional Session F – SavFIRE – Govender, Trollope, Austin & Held