Thesis (MScConsEcol(Conservation Ecology and Entomology)--Stellenbosch University, 2008. / The Succulent Karoo biodiversity hotspot is threatened by pressure caused by increasing
human populations and its associated land use types. Land use is primarily focussed on
agriculture, with livestock grazing as a dominant land use in the region. Cultivation is
also practiced along the major perennial rivers, and in drier areas, where this largely
depends on rainfall. Only about seven percent of the biome is formally protected, and this
area substantially under-represents the biodiversity of the Succulent Karoo and does not
incorporate key ecological processes and biodiversity drivers. Therefore, there is urgent
need for outside reserve conservation initiatives, whose success depend on understanding
the ecosystem function of the Succulent Karoo. This study aimed to determine the
impacts of heavy grazing, light grazing and cultivation (in a 30-year old fallow field) on
assemblages of ground-dwelling and flying invertebrates. Seasonal assemblage changes
were also determined. Vegetation structure and composition were determined using the
line-intercept method to determine if vegetation patterns explain patterns in invertebrate
assemblages. Abandoned fields harbour the lowest number of plant species, and these
together with the heavily grazed sizes are dominated by a high cover of Galenia africana
(Aizoaceae). Lightly grazed sites have the highest structural complexity, with a high
cover of succulents and non-succulent perennials. After the winter rains, annual plants
occupy most of the bare ground in heavily grazed and previously cultivated sites.
Seasonal changes in assemblages of ground-dwelling and flying invertebrates were
determined by sampling during the four seasons at the same localities. Results of pitfall
traps sampling for ground-dwelling invertebrates and coloured pan traps for flying
invertebrates showed that overall species richness and diversity peaked in spring for
flying invertebrates while peaks in richness for ground-dwelling invertebrates were in
summer, with no difference in overall diversity. Overall abundance for ground-dwelling
invertebrates was highest in summer and lowest in winter. Ground-dwelling invertebrate
fauna was dominated by Formicidae and Araneae. Grazing and cultivation lead to skewed
community composition of ground-dwelling invertebrates which favours disturbance
tolerant and generalist species such as Anoplolepis steingroeveri (Forel).
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/2228 |
| Date | 12 1900 |
| Creators | Nchai, Makebitsamang Constance |
| Contributors | Krug, Cornelia B., Samways, M. J., Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology. |
| Publisher | Imported from http://etd.sun.ac.za April 2010., Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | Stellenbosch University |
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