AbstractsBiology & Animal Science

Thesis (MScConEcol (Conservation Ecology and Entomology)) – University of Stellenbosch, 2011. ENGLISH ABSTRACT: Invasive alien plants (IAPs) reduce streamflow and threaten the biodiversity of South Africa’s Cape Floristic Region. Up-to-date information on invasive vegetation is required for land management agencies to formulate policies and make appropriate resource management decisions. Invasion maps are typically not updated often enough because of the time and expenses required to do so. As a result, invasion maps for South Africa are limited to coarse resolution data or isolated small scale studies. Invasive alien plants change the landscape by destabilizing catchments and thereby increasing soil erosion, altering fire regimes and hydrology, as well as changing the physical and chemical composition of the soil. Information on IAPs is needed at a landscape scale. Remote sensing is a powerful tool that can be used to characterise landscapes in a biologically meaningful manner. The Normalised Difference Vegetation Index (NDVI) was used to create an up-to-date invasion map of the Agulhas Plain, lying at the heart of the species rich Cape Floristic Region. This information was combined with actual evapotranspiration data from the Surface Energy Balance Algorithm for Land (SEBAL) study done by Water Watch and the Council for Scientific and Industrial Research. The results showed that invasive vegetation uses more water than natural fynbos vegetation and that the greatest amount of water would be made available by clearing the invaded deep sands on the Agulhas Plain. These deep sand areas conflict with the priority areas of the Working for Water programme. This IAP eradication programme targets sparsely invaded upland areas for long-term sustainability. The recommendation of this study is to clear invaded wetland and riparian areas as these zones yield the greatest hydrological benefit per hectare and meet the priorities of Working for Water. Overall, 36 million cubic meters of water would be made available by clearing the Agulhas Plain. It can be concluded that there is a significant hydrological benefit to clearing invasive alien vegetation on the Agulhas Plain. AFRIKAANSE OPSOMMING: Indringerplante (IP) verminder stroomvloei en bedreig die biodiversiteit van Suid-Afrika se Kaapse Floristiese Streek. Die nuutste inligting oor uitheemse plantegroei is nodig vir grondbestuuragentskappe om beleide te formuleer vir die neem van toepaslike hulpbronbestuur besluite. As gevolg van die tyd en uitgawes wat nodig is om indringingskaarte op te dateer, word dit gewoonlik nie dikwels genoeg gedoen nie. Dus is indringingskaarte vir Suid-Afrika beperk tot growwe resolusie data of geïsoleerde kleinskaal studies. Indringerplante verander die landskap deur opvangsgebiede te destabiliseer en sodoende te lei tot gronderosie, verandering van vuurregimes en hidrologie, sowel as die verandering in die fisiese en chemiese samestelling van die grond. Inligting oor IP is nodig op 'n…