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Comparison of Plant Communities Inside and Outside the Moringa ovalifolia Plot at Sprokieswoud in Etosha National Park; Namibia. Done by Asante - Sana C. Namugongo ==

Moringa ovalifolia, also known as the Phantom tree, in English, or Sprokiesboom in Afrikaans, is one of the most fascinating trees found in Etosha National Park. It is a well known tourist attraction, because of the way it grows in the Sprokieswoud area. Moringa trees usually grow on hill slopes and rocky escarpments around the northern and central regions bordering to the Namib Desert, but the Moringa trees in Sprokieswoud grow on an open calcaric plain.

Moringa belongs to the monotypic family Moringaceae, with only 12 known species and this unique family is phylogenetically placed between Capparaceae and Facaceae. The name ovalifolia, derives from the tree’s oval leaflets. Another well known Moringa species is the Moringa oleifera, but is not indigenous to Namibia. This tree is native to India and its seeds are utilised by humans and animals. People use the seeds for yielding an oil, as lubricant, formerly used by watchmakers (Mannheimer & Curtis, 2009). Currently it is used in soaps, salads and also as a water-clarifying agent (Van Jaarsveld, 2007). Animals such as elephants, giraffe and springbok eat the fruit and leaves, while elephants and porcupine utilize the fleshy stem, which results in its strange and bizarre shape. This near-endemic plant, which also extends into southern Angola, is protected by the Nature Conservation Ordinance No. 4 of 1975 (Curtis & Mannheimer, 2005).

The Moringa tree, is a conspicuous, deciduous plant with a thick, succulent trunk that can reach up to 1 m in diameter and can grow up to a height of 8 m. The bark is smooth, silver-grey or pale brown with a shiny green sheen and is resinous. The leaves are twice-compound, alternately arranged and cluster near the ends of the branches, leaflets are oval shaped and can grow up to 25 mm long. (Van Jaarsveld, 2007).

Flowering time is mainly from November to May and fruiting occurs from October to May. The flowers are small, white and appear abundantly before or after young leaves have branched. They are followed by the triangular shaped, long grey-brown pods, up to 400 mm and split along three valves releasing winged seeds (Curtis & Mannheimer, 2005).

In 2011, a study was conducted to compare the plant communities inside and outside the Moringa ovalifolia enclosure at Sprokieswoud. The enclosure at Sprokieswoud was erected in the early 1970s, and the area inside the enclosure has not been utilised for the past 40 years. The objectives for this study were to:

1.	Compare the species richness and abundance of the vegetation inside and outside the enclosure for grasses and small herbaceous plants as well as trees and shrubs

2.	Develop and apply an index of vitality and an index of decay for the Moringa ovalifolia trees.

3.	Compare the vitality and decay of Moringa ovalifolia trees inside and outside the enclosure.

4.	Investigate the re-growth of “dead” Moringa trees as well as the growth of saplings inside and outside the enclosure.

The results from this study showed that the enclosed area was underutilised, while the grasses outside the enclosure were utilised.

From this survey the tree with the highest density inside the enclosure was the Moringa tree with 48 %, while outside the enclosure it was the Mopane tree (Colophospermum mopane) with 60 %. Although Rattle Bush (Catophractes alexandri) was found both inside (5 %) and outside (10 %) the enclosure, a few trees in either area.

Vitality and Decay The Moringa ovalifolia trees inside the enclosure were in better condition than the trees outside, and had higher ratings. But at the same time, the highest number of decaying trees were found inside the enclosure and not outside. A reason for this would be that the trees outside the enclosure were being utilised by other animals as food and decayed faster than those inside the enclosure. It would take a long time for the dead trees protected inside the enclosure to disintegrate as no animals feed, burrow or remove sections of it..

Height Classes

The height class data that was collected for this survey, showed that inside the enclosure, there was a high percentage of trees in height classes ≤ 2 m and 4.1-6 m. The high percentage of trees found in height class ≤ 2 m shows that there is a success in seedling establishment during the rainy season. The lowest percentage of trees was found in height class > 6 m, which would indicate that there are fewer older trees compared to those found in height classes ≤ 2 m and 4.1-6 m.

As for the trees outside the enclosure, there was a high percentage of trees in the height class of > 6 m, while there was a sharp decrease with the trees found between 2.1 and 6 m. This means that these height classes may become depleted leaving no trees to replace those above 6 m.  This survey also revealed that only trees higher than 6 m were able to produce seeds. This is because the trees outside the enclosure are not given a chance to fully mature and bear seeds at a lower height class, because of animals such as giraffes and elephants eating them, thus resulting in pre-mature seeds being produced.

One can assume that there are two possible reasons for this, firstly the enclosure was designed to protect the densest area of the Moringa ovalifolia trees. Secondly as unprotected Moringa ovalifolia trees gradually disappear outside the area, there would then be a high relative abundance of Mopane trees that occur more commonly in the Sprokieswoud area.

Re-growth and Seedlings

Although few, all seedlings were found inside the enclosure. When the survey began in March, the seedlings were all in very good condition, but during the Moringa Monitoring Programme surveyed in May, there were indications that the leaves had been eaten by insects as shown in Figure 7 below.

Only one example of re-growth occurred inside and outside the enclosure. So not a large enough sample size to make any comparison. The re-growth could be attributed to the fire that occurred in 2009 as well as the high rainfall in 2011. Re-growth was also noted outside the plots that were surveyed, so again the plots selected may not have been sufficient, but growth noted in March had remained by May.

Conclusion

•	The grass species composition showed that although there were more grass species outside the enclosure, there could be a possibility that the grasses inside are competing for resources at a higher rate, because of over-utilisation.

•	The species composition of the trees and shrubs showed a similar number of Mopane and Moringa trees inside the enclosure and a higher number of Mopane outside.

•	There was a high number of trees with high vitality scores, but at the same time had more trees in a decaying state inside the enclosure. This is because there were no animals to utilise the trees for the decaying process to be faster.

•	With the height classes, the trees inside the enclosure showed to have a successful seed establishment because of the high number of trees found below 2 m. As for the trees outside the enclosure, there was a high number of trees above 6 m compared to those between 2.1 and 6 m that occurred in fewer numbers. The depletion of these height classes may result with there not being any trees to replace those above 6 m.

•	The was a high number of seedlings found inside the enclosure, while re-growth remained relatively similar both inside and outside the enclosure.

Recommendations

•	Monitoring on the Moringa trees should be continued and published. The vitality and decay indices developed and tested in this study should be included as well.

•	This survey did not test any differences in soil composition both inside and outside the enclosure, which might be included in future, to link it to concerns experienced by Nott and Nott (1987 a and b).

•	Another study could be done to observe what would happen if the existing enclosure were divided in half with one half of the enclosure left half way open to allow small grazers to enter underneath to graze on the grass and the other half to remain completely fenced off.

References

Curtis, B. and Mannheimer, C. (2005). Tree atlas of Namibia. Windhoek: National Botanical Research Institute.

Du Plessis, W. P. and Venzke, K. (1989). Die monitering van Moringa ovalifolia te Sprokieswoud (Nasionale Etoshawildtuin) met bestuursaanbevelings. Internal Report. Okaukuejo: Etosha Ecological Institute.

Joubert, D. (2007). Ecology 1 study guide: biotic components of ecosystems, species composition and species diversity. Windhoek: Polytechnic of Namibia.

Mannheimer, C. and Curtis B. (2009). Le Roux and Müller’s field guide to the trees and shrubs of Namibia. Windhoek: Macmillan Education Namibia.

McIntyre, C. (2007). Namibia. 3 ed. Connecticut: The Globe Pequot Press Inc.

Namugongo, A. (2011). Comparison of plant communities inside and outside the Moringa ovalifolia plot at Sprokieswoud in Etosha National Park; Namibia. Unpublished Report. Windhoek: Polytechnic of Nambibia.

Nott, K. and Nott. T. (1987). Monitoring of uncommon and area localized plant populations in Etosha National Park. Final Progress Report. Okaukuejo: Etosha Ecological Institute.

Nott, T. and Nott, K. (1987). The monitoring of density and structure of Moringa ovalifolia at Sprokieswoud 1985 - 1987. Progress Report No. 2. Unpublished. Okaukuejo: Etosha Ecological Institute.

Oliver, W. And Oliver, S. (1993). A guide to Namibian game parks. Windhoek: Longman Namibia.

Shatumbu, G. Unpublished. The monitoring of density and structure of Moringa ovalifolia at Sprokieswoud. Progress Report No. 4. (2008). Okaukuejo: Etosha Ecological Institute.

Shiponeni, N. (2011). Population dynamics for an endemic tree species, Moringa ovalifolia Dinter & Berger: population structure, recruitment, reproductive vigour in different habitats. Unpublished, project proposal. Windhoek: University of Namibia.

Van Jaarsveld, E. (2007, January). Moringa ovalifolia Dinter & A. Berger. Retrieved January 12, 2011, from http://www.plantzafrica.com/plantklm/moringoval.html.

Vilho, A M. (2010). Population structure of and apparent mortality rates in three populations of Aloe dichotoma at Canyon Nature Park. Unpublished. Windhoek: Polytechnic of Namibia.