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Fighting fire with fire
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“We’re burning down the berg!” shouts Thami Shezi as fire roars up the catchment.
Getting their first taste of fire ecology hands on, the SAEON Grasslands Node interns Nqobile Lushozi, Luke Bodmann and Nobuhle Mweli look on nervously.
Then Thami smiles. “Soon it is going to be beautiful,” he says, and explains to the team how the grass will flush and how a flowering spree can be expected later in the growing season.
The mesic grasslands of South Africa’s Drakensberg are known as “fire” climax grasslands. Without fire, changes would occur in the biodiversity and services provided by the grasslands. The grasslands provide us with water, carbon storage and outstanding scenic beauty.
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The effects of different fire regimes on biodiversity
Paul Gordijn, botanical technician at the Node, is currently investigating the effects of different fire regimes on biodiversity for his PhD. He is using historic plot data to assess long-term vegetation dynamics in relation to fire and land use.
The high rainfall in areas of southern Africa allows the buildup of sufficient grassy biomass to sustain frequent fires, naturally ignited by lightning and sometimes even by rock falls. The average return interval for fires in the Drakensberg is about two to three years.
The biodiversity in our grasslands is dependent on burns such as these. Without fire, these grasslands and their extremely high biodiversity value would disappear.
Fire management
The Grasslands-Forests-Wetlands Node’s host organisation, Ezemvelo KZN Wildlife (EKZNW), has a comprehensive fire management plan aimed at promoting the rich biodiversity of the uKhahlamba Drakensberg Park.
Active fire management is considered necessary in a landscape where human influences have become more prevalent than natural disturbances. For example, dry season winter arson fires are considered a major problem in the Drakensberg, exposing soils to wind erosion, causing damage to property and threatening human life.
Spring burns every two to three years are considered a good regime for maintaining healthy grasslands. As a natural disturbance regime in the landscape, the long-term monitoring efforts undertaken by the Node incorporate fires into the monitoring framework. This means fires are allowed in the experimental catchments despite an extensive instrumentation network that Node researchers and technicians have deployed in the area.
“Our challenge each year is to protect the sophisticated instrument systems from the frequent winter arson fires,” says Node Coordinator Sue van Rensburg. “We also need to ensure that when we do burn the catchments on their two-year rotation, we do not lose any valuable equipment.”
The Node team has strong support from land custodians EKZNW. They host a Working on Fire team from the Department of Environmental Affairs who, under EKZNW's direction, provide the necessary ground-based support to ensure that the experimental areas can be burnt with relative safety.
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Planned spring burn
In September this year, catchments 6 and 7 were burnt in a planned spring burn. Says Sue: “The fire provided us with the opportunity to expose our interns to fire ecology and the excitement of ‘burning down the berg’, as Thami put it.”
The responsibility of ensuring the equipment is safe falls on instrument technician Kent Lawrence, with assistance from development technician, Siphiwe Mfeka.
“Preparation for the fire season starts as early as May every year,” explains Kent. "First, breaks around the equipment are cut and raked. Then we wait for absolutely perfect conditions to burn breaks around the equipment - no wind and cool, preferably humid conditions, just as the first frosts arrive.”
At the same time, EKZNW prepares tracer lines around the main catchment on historic firebreak lines. In June, once the frost has cured the grass, the EKZNW team burns these breaks between the tracer lines, protecting each of the catchments. These firebreaks are intended to protect the catchments from potential arson fires.
The “planned” schedule for the research catchments is to burn them every two years in spring as the first rains arrive. This practice has been in place for the experimental catchments since the 1950s.
The big day dawns…
The 1st of September signals spring, time for the actual catchment burns. Again, waiting for the right conditions is critical. Ideally it should have rained at least once before the burns. Berg wind conditions (hot and dry) with high-speed winds result in “red” days and must be avoided.
After waiting a few days, removing a few vulnerable gauges and doing a few pre-fire measurements, management decided on the day. The Node team set off early to get everything prepared for the fire team, enjoying the sunrise on the way up.
“Once everyone had arrived on site, an extensive discussion followed to ensure we have a clear plan and everyone is on the same page,” says Kent. “Safety is of utmost importance - things can go wrong very fast without good planning and communication.”
The first task is to burn inside the equipment areas under very controlled conditions. Once this is done, the catchments can “burn freely” as the equipment areas are now considered “safe”.
“We use the wind, initially setting a back burn from the top of the catchments, working against the prevailing winds, with the firebreak as the forward burn boundary,” explains Kent. Side and mid sections are lit to allow a forward burn up the top section of the catchment. Lines are then drawn down on either side of the catchment and closed off around the base to allow for a roaring forward burn up the lower centre of the catchment.
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After the fire, team members immediately replaced the gauges they had taken out the previous day. They also did some (not so high tech) measurements of flame height, effective enough to show the variability of the flame heights over the catchments.
The Node team is proud to report that both catchments 6 and 7 were successfully burnt within an exhilarating two hours.
