Kruger National Park
Scientific Services
Exclosures
Maps of whereabouts of all exclosures and enclosures
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Description of each past and present and what type of research occurs there
The three exclosures mentioned here are the Letaba on the Letaba River, Nkuhlu on the Sabie River opposite Nkuhlu picnic site and Makhohlola in the south-eastern corner of the KNP just north of Crocodile Bridge. Table 1 provides a summarized description of the exclosures.
Table 1. Brief description of the scientific exclosures in the KNP.
| Exclosure | Meaning of name | Year of construction | Size | Substrate type | Vegetation type |
|---|---|---|---|---|---|
Letaba |
Sotho for “sand river” |
2002 |
129 ha |
Granite (sandy soils) |
Letaba River Rugged Veld - mainly mopane/combretum woodland with distinctive riparian zone |
Nkuhlu |
Tsonga for “natal mahogany” |
2002 |
139 ha |
Granite (sandy soils) |
Thickets of the Sabie and Crocodile Rivers - dense woody vegetation referred to as Acacia nigrescens/Combretum apiculatum association |
Makhohlola |
Tsonga for “he who coughs all the time” |
Early 1970’s |
4 ha (of which 2 ha unfenced) |
Basalt (clayey soils) |
Sclerocarya birrea/Acacia nigrescens Savanna – open tree savanna |
Purpose
The main purpose of these exclosures is to determine the effect of different combinations of fire, elephants and other herbivores on the vegetation. The exclosures will be maintained and managed as such for the next 20-25 years during which close monitoring of changes will be done. The set-up also provides ideal opportunities for other research, such as soil – plant relationships, soil nutrient and population dynamic studies.
Scientific Issues
During the initial stages of the exclosures, baseline vegetation surveys were conducted to serve as benchmarks against which subsequent changes will be measured. These surveys will be repeated every five years, thereby building a time-series dataset.
A detailed soil survey, including a classification and descriptions of soil profiles, has been completed in 2003. Fine-scale orthomaps with contour intervals of 0.5 m were also produced for both Letaba and Nkuhlu exclosures, based on low-level aerial photography.
On-going data collection on soil water parameters is being performed since the beginning of the exclosures and will provide important information on soil water movement locally and along the toposequence.
Fixed-point and aerial photography have also been conducted to form part of the longer term monitoring programmes.
Below follows a list of currently registered projects as conducted by SANParks and visiting researchers:
- Comparing grass biomass production of sodic sites and crest zones in the semi-arid, granitic lowveld of Mpumalanga and Limpopo . (Researcher: Glynn Alard ; contact person: Nick Zambatis )- only at Nkuhlu
- Ant monitoring. (Researcher: Alan Andersen, Aleric Fisher and Hendrik Sithole )
- Large woody debris and herbivory as drivers of riparian succession along the Sabie River , Kruger National Park , South Africa . (Researcher: Neil Pettit; contact person: Nick Zambatis )
- An analysis of the impacts of elephants on woody vegetation in the research exclosures.(Researcher: Sampson Mamphweli; contact person: Nick Zambatis )
- Below-ground processes experiments. (Researcher: Joe Craine; contact person: Nick Zambatis )
- Global climate change and primary productivity: the effect of inter-rainfall interval on grass growth. (Researcher: Tony Swemmer; contact person: Nick Zambatis )
- Population dynamics and the effects of herbivory and fire on the regeneration ecology of Acacianigrescens and Dichrostachys cinerea in the Kruger National Park, South Africa. (Researcher: Bradley Wilson; contact person: Holger Eckhardt )
- Soil and plant nutrient relationships in riparian, sodic and upland vegetation in the presence and absence of large herbivores and fire (Researcher: Shayne Jacobs; contact person: Holger Eckhardt )
- Determination of the Rodentia in the Nkuhlu exclosure: A baseline survey. (Researcher: Mike Smith; contact person: Andrew Deacon ).
Feedbacks
Attached you will find some feedback on project no. 2 (see list above) regarding ant monitoring. Hopefully we will be able to provide you with feedback on other projects as well in our next issue.
Management Issues
The exclosures are regularly patrolled and inspected; breakages and faulty electrical systems are reported immediately and usually soon afterwards attended to by a qualified maintenance team. Serious damage to the sacrificial exclosures was inflicted by higher flows of the rivers earlier this year. Due to persistent high water levels, repair work could only be conducted later towards the end of the rainy season. Batteries and energizers had to be replaced on a few occasions. In general, it seems that the frequency of breakages has declined considerably, which might be ascribed to the animals getting used to the fences. However, an increase in breakages or at least attempts by animals to get into the exclosures, can be expected towards the end of the dry season due to the availability of relatively higher amounts of grazing and browsing material.
The company Momotheka Fencing is currently busy putting up a Bonnox fence at the Nkuhlu exclosure as an addition to the existing fence in order to prevent animals from jumping through the fence. The Kruger Park Marathon Club has kindly made funds available for this fencing exercise.
Human-induced erosion in the exclosures is a concern, especially along the fences where trenches had been dug to bury the cement wall. This problem is being addressed and will be tackled in August/September before the next rainy season starts.