A successful burn

A SUCCESSFUL BURN

A lot of our grasslands are becoming dominated by woody plants, particularly Helichrysum wilmsii and H.kraussii, which are strongly scented low scrub bushes. Woody plants begin to dominate grasslands when there is a lack of fire. Because woody plants have a canopy they appear to cover the entire ground but in fact the canopy creates a shade that smothers the grass beneath it resulting in bare ground between plant stems. This causes a higher rate of erosion as the water runs beneath the canopies over the bare ground, not to mention it reduces graze for wild game. Grasses, on the other hand, are designed with their upright leaves to grow very closely alongside one another, minimizing erosion. This is why grasslands naturally burn more regularly than any other type of biome, mostly through lightning fires from dry and wet thunderstorms. With our fire breaks, roads and fire control methods, we cannot rely on natural lightning fires to combat these encroachments of woody plants. We, therefore have to rely on human-induced management burns to control them. In our case, hot fires are required initially to destroy the woody plants.

Don MacCrimmon leading David Maseko and his team from KLF in the ignition sequence along the tracer which follows the cycle path from Haartebeesvlakte to Loop road. Note the large KLF fire trucks in the backround.

Another advantage of a hot fire is that it will kill relatively large Pine trees that also tend to encroach on our grasslands. Those of you who have travelled to the north eastern part of the Estate in the last few years will have noted how those grasslands have been encroached by large plantations of Pine. My team and I have been fighting Pine all over the Estate since I arrived here but we had not yet reached the north eastern areas. Because of this, I decided a very hot fire was needed in the area this year to assist in the removal of these Pine trees.

Our team struggled to contain the fire on the bottom of Loop road because of the amount of moribund fuel. The Cruiser with the bakkie sakkie (just ahead of the flames) was invaluable in stopping the fire from jumping! Note the massive amount of Pine trees on the slopes behind the smoke.

Now, to create a hot fire that does not damage the shallow roots of the grasses, there needs to be sufficient moisture in the soil (usually at least 30mm rain just prior to the planned burn) but the grasses and bushes themselves need to be dry. The ambient temperatures also need to be higher than 22 degrees for the fire to be hot enough to destroy the woody plants. these conditions are common when the Fire Danger Index (FDI) is also high. This means we have to contact the Mpumalanga Fire Control Department on the day we intend to burn and receive a burning permit. to receive the permit we have to reveal the amount of fire-fighters we intend to employ and the amount of fire fighting equipment we aim to use so that the fire cannot rage out of control.

A view of the burned block from the KLF road at the end of the day

Well, since the area I wanted to burn spanned part of the Estate, part of Mount Anderson Water Reserve and part of Komatiland Forests, I had to make sure we all worked together on the project. And so we were all on stand-by when, on the 12 October, conditions were perfect for a hot burn. The ignition points were long due to lack of vertical fire breaks on the Estate, so we had three teams (one from each property) lighting the fire. Everything went off just dandily, it did! We had a hard time in the low lying areas because of the abundance of fuel there, but managed to control the fire. Trent Sinclair and his team from MAWR also had difficulty at the very end of the operation as the winds turned in the afternoon. The photo at the top was taken from the Loop road just opposite Pebble Creek (Unit 25) during this struggle!

A photo taken the following day of about half of the block from Loop road just west of the cycle path junction.

 

A few days afterwards, I explored the block and found no animal carcasses or any other collateral damage as I had hoped and expected. Animals that live in grasslands are well adapted for evading fire because it is such a common occurrence. I did, however, find many Pine tree carcasses which was very pleasing! On the west facing slopes of the burned block, about 90% of all Pines were destroyed. On the south facing slopes, about 60% of Pines were destroyed and on the east facing slopes, where the fire was cooler, only between 10 and 20% of the Pines were killed. Overall, more than 60% of Pine trees in the block were killed, saving us many months of back-breaking work!

Dead Pines. Big ones too! Mission accomplished.

There will be another two seasons of hot burns on the Estate before I can prepare the grasslands for the type of burning that is optimal. Once the woody plants have been brought under control, the entire Estate will be burned tri-annually (a third per year). The grasslands will be divided into many much smaller burn blocks which will burn alternately during the wet seasons on cool, wet days. This kind of management burning is called Patch Mosaic Burning and is the method employed by Mpumalamga Parks and Tourism Agency and National Parks. This method will minimize silting up of the rivers and will require much less staff. These types of fires will only burn off the moribund and will simulate lightning fires keeping our grasslands pristine into the future....