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Biotic determinants of heterogeneity in a South African savanna

PhD ceremony:Ms C.M. Gosling
When:December 19, 2014
Supervisor:prof. dr. H. (Han) Olff
Co-supervisor:J. cromsigt
Where:Academy building RUG
Faculty:Science and Engineering
Biotic determinants of heterogeneity in a South African savanna

Patchiness is important in maintaining a productive, healthy ecosystem. Understanding causes of heterogeneity are important for conservation. The thesis of Cleo Gosling describes, and aims to explain, vegetation patchiness across a range of scales in Hluhluwe iMfolozi Park, South Africa. Why does a patch of trees occur here, and grasses there? Do the causes of this patchiness change as you look at different sized patches? Gosling’s particular focus was on the effects of features created by rhino, such as wallows, middens, and gamepaths, and three different types of termite mound, on vegetation patches. This comparison of mega- and micro- herbivores makes her work unique.

Gosling found that termite mounds, specifically those built by Macrotermes, were the most influential in creating different vegetation patches, across all scales examined (1 m2 – 0.25 km2).She also examined which factors may influence where termites are likely to be most active. Increased rainfall and tall vegetation reduced termite activity; these conditions promote microbial decomposition which may influence termite food resources. Therefore, although Gosling found that termites have an important role in creating vegetation patchiness, it maybe that ecosystem drivers need to be examined at yet smaller scales. An important conclusion of Gosling is that the size of an organism may not be a indicator of its importance in ecosystems. Both rhino and termites are important and have comparable effects.  General conservation efforts would do well to encourage healthy termite populations, and the development of termite mounds, to generate a patchy and robust system, before introducing suites of large herbivores.