60 years on, the Experimental Burn Plots of the Kruger Nat. Park continue to provide new insights for savanna ecology

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60 years on, the Experimental Burn Plots of the Kruger Nat. Park continue to provide new insights for savanna ecology

Post by Lisbeth »

By Tony Swemmer, Manager, SAEON Ndlovu Node

In 1954, conservation managers in the Kruger National Park initiated what would become one of the longest-running fire experiments in the world, amid concerns about the lack of information regarding the effects of fire on the fauna and flora of the park.

At the time, burning of natural grassland and savannas was a highly contentious issue. Many felt that fire could only have a negative effect on nature.

However, a fire suppression policy that had been in place since 1948 had led to new concerns about bush encroachment and deterioration of grass production in the complete absence of fire. Furthermore, the accumulation of dead grass during the fire suppression period was resulting in wildfires that were large and difficult to control (about a quarter of the park was burnt by unintended fires in 1953).

In response, the newly formed “Biology Section” of the Kruger National Park set up “burning trials” at four sites, in four of the major ecosystem types in the park. The design was large and ambitious - four replicated “strings”, each consisting of seven plots, were laid out at each site, with each plot an impressive seven hectare in size.

Each plot within a string was assigned a different burning treatment including a control (no burning) and various combinations of fire frequency (once a year or once every three years) and season (winter, spring or summer). These plots are clearly visible from space, along with the double roads which enclose a fire break on each side of each string.

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The vegetation of the plots was surveyed at the start of the experiment, with the intention of resurveying every year. However, this proved to be too ambitious due to the number and size of the plots, and the large numbers of small trees and shrubs present.

It took three years just to do the initial survey of all plots. Management were able to successfully implement, and record, the burns planned for each plot every year, resulting in a long-term experiment that is now of immense value for understanding the role of fire on savanna ecosystems.

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Researchers from around the world have recognised the value of this unique ecological research infrastructure, now known as the Experimental Burn Plots (EBPs) of the Kruger National Park, and many research projects have been conducted on the EBPs since the late 1990s. Results produced by these researchers have in turn assisted staff of the SANParks Scientific Services division to motivate for the budgets required to keep the experiment going (controlled burning of up to 144 plots a year at remote sites within a large national park is not cheap).

Impact of factors other than fire
The carefully maintained burning treatments, and associated data, of the 60-year-old EBPs are now allowing researchers to determine the roles of factors other than fire that affect the composition and functioning of savanna ecosystems. Of particular interest are two factors that have changed substantially since the initiation of the experiment: elephants and atmospheric carbon dioxide (CO2).

In the 1950s, elephant numbers in the park were still low and elephant impacts on vegetation negligible. Atmospheric CO2 was not much higher than pre-industrial levels. In order to test how these factors might be altering the effect of fire on vegetation, the SAEON Ndlovu Node and SANParks Scientific Services teamed up to resample the trees at all four sites over the summer of 2015-2016.

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Surprising results
Analysis of these data, together with the data collected from all previous samples - in the 1950s, 1970s, 1990s and 2000s, has produced some surprising results.

The density of trees and shrubs has clearly declined at the two drier sites (Mopane and Satara) regardless of burning treatment. This reflects the increasing impacts of elephants over recent decades, and demonstrates that fire is not required in these systems to prevent bush encroachment above a certain population density of elephants.

The EBP site of intermediate rainfall, located near Skukuza camp, has experienced high variable trends in tree and shrub density, most likely reflecting complicated interactions of soil types, fire and elephants.

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At the Pretoriuskop site (“Pkop” in the above graph), tree and shrub densities have increased, even on plots burnt every year. This site, which has the highest rainfall, now supports far higher densities than any of the other sites, as well as most parts of the park.

It is possible that plants at this site have been able to utilise elevated levels of atmospheric CO2 to overcome the harmful effects of fire (the exact mechanism behind this is explained in SAEON’s “Change is in the Air” booklet). However, closer examination reveals that while increases were dramatic between the 1970s and 1990s, there has been no significant increase in tree and shrub density since then, even on plots that never burn. This suggests that any effect of CO2 is now over, perhaps due to counteracting effects of increasing elephant impacts, or due to increasing competition between trees and shrubs.

Further research
Further research is needed to determine the exact causes of these trends, and continued implementation and sampling of the EBPs will play a critical role in helping ecologists to determine the true causes of past (and future) changes in the structure and functioning of our savannas.

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Re: 60 years on, the Experimental Burn Plots of the Kruger Nat. Park continue to provide new insights for savanna ecolog

Post by Richprins »

Extremely interesting, this! Especially the apparent CO2 effect that seems not so important? :-?


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Re: 60 years on, the Experimental Burn Plots of the Kruger Nat. Park continue to provide new insights for savanna ecolog

Post by okie »

A few years ago , I noticed these " roads" alongside the S49 , and with nothing to indicate a no-go , I drove up and down to see what its all about ;-)
Each plot had a marker , as seen here .
IMG_2207.JPG
IMG_2204.JPG
IMG_2203.JPG

All very interesting , all the plots looked the same to me :O^

And not a single animal at all 0*\


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Re: 60 years on, the Experimental Burn Plots of the Kruger Nat. Park continue to provide new insights for savanna ecolog

Post by Lisbeth »

At least now you know what the plots were for ;-)


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Re: 60 years on, the Experimental Burn Plots of the Kruger Nat. Park continue to provide new insights for savanna ecolog

Post by RogerFraser »

\O Interesting :yes:


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Re: 60 years on, the Experimental Burn Plots of the Kruger Nat. Park continue to provide new insights for savanna ecolog

Post by Richprins »

Fighting fire with fire – Kruger nearing 70 years of testing fire regimes
A fire experiment, one of the many ongoing research projects in the Kruger National Park (KNP), has been running since the 1950s.
1 day ago
Linzetta Calitz


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Standing between two plots of 150 by 350 metres near Skukuza, Tercia Strydom, an abiotic scientist in the park, explained that it was one of the world’s largest, long-term fire experiments.

“The reason why this experiment was started was to test the role of different fire regimes (different fire frequencies and intensities) on savannah vegetation.

“What we see here are just two plots. It is repeated in the landscape across the park, and there are 208 of these plots that we have been maintaining for the last almost 70 years.”

Strydom said the KNP has a long history of fires that translates to a system of fire management and research.



“Our management strategy has gone through many eras over the past decades and we have learned a lot along the way as research improves and we get the latest technology.

These days we make use of satellite imagery to monitor our fires across the park, so we have come a long way to where we are today.”
The satellites provide the park with updates twice a day.

She said it is important to note that fires are an important part of the system. Both animals and trees are able to cope with fires, said Strydom.

“Many of these tall trees have very thick bark that allows them to cope with a fire.

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“Only once a tree is compromised, for example when a marula tree is debarked by an elephant because he is eating, a fire comes through and the heat penetrates into the inner cambium of the tree; that is the part that transports nutrients and water from the roots to the leaves. That is often how we lose our big trees; it is not just because of a fire.

“What is quite interesting and shows how these animals have evolved with fires, is that when we are burning and putting in controlled experimental burns, birds come and flock because they know insects will be trying to get away from the fire.”

Animals are seen grazing on the side of the veld that has burnt as well. Strydom said this shows that there is something they want and need in that area.

When it comes to the experiment, there are two plots next to each other. One is scheduled to burn at a specific time, while the other serves as a control plot that does not get burned at all.



These two are then compared to see what the effects are on the vegetation. To the untrained eye the plots might not look very different, but Strydom pointed out that one is “more woody with a lot more grass, where the other is a more open area”.

“There is one plot that we burn every year in August, then there is one that also gets burned in August, but only once every three years. There is then three years’ worth of ‘fuel load’, so the intensity is slightly different. It will be more intense, because there is three years’ worth of grasses that we are burning.

“Then we have one that burns once every three years in December, which is a much cooler fire, because the grasses are starting to green up. Then there is one every three years October, and every three years April.

“We burn five times a year and then there are various frequencies. Every year, every two years, every three years and up in Satara, and at Mopani we burn every four and six years as well, and then there is one plot where fires have been kept out.”

Strydom said this experiment was started during a time when the thinking was that fires are bad for the system. National policy at the time prohibited prescribed burning because of the perceived effects it had on soil.



“The thinking was that fires are bad for the soil and that they will lead to soil erosion and degradation, and that is bad for farming. That was when we thought we need to have an experiment to see if fires have a detrimental role or are a positive for the savannah. And after the last decades of research, we have seen and shown that fires are very important for the system.”

Strydom did her masters on these burn plots and is busy with her doctorate. She is taking a look at the effect of fires on soil hydrology: do they cause erosion, do they cause a reduction in the filtration rates and are they bad for soil nutrients?

Initial findings suggest that when it comes to soil, a fire does not make that big of a difference.
Regrowth after a fire in Malelane in 2020. > Photo: SANParks

“Fires do have an initial effect on soil. With regards to infiltration, they will slow it down initially, especially when there is still ash on the surface. And then, over time, like within a year, there is no difference between one plot and the other; the hydrology is very similar.”

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The experiment also has collaborators from different countries. Strydom mentioned the involvement of the European Space Agency. With the satellites currently available, they are able to pick up fires on these plots, which was not possible with older satellites.

One of the few disadvantages of such a large-scale, long-term experiment is the funding and logistics it requires.


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“Although this is one of our champion research infrastructures in the park, maintaining it takes a lot. Two-hundred and eight burn plots burned five times a year at various frequencies does take a lot.

“Somehow we have managed it for the last 60-plus years. We have maintained the integrity of the experiment. We make sure that if it is scheduled to burn every year August, we will burn it.

“So far, so good; we have not had major issues with regards to maintaining it.”

https://lowvelder.co.za/731252/fighting ... e-regimes/


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Re: 60 years on, the Experimental Burn Plots of the Kruger Nat. Park continue to provide new insights for savanna ecolog

Post by Lisbeth »

Very interesting. They are doing a serious study, but after 70 years it would have been nice to hear about the results that have been reached. By now they must have an idea of which is the ideal way of handling the fire.


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