A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2015. / Land transformation and associated habitat loss has been identified as one of the biggest global factors affecting decreases in frog biodiversity. Gauteng Province is South Africa’s economic hub and much of the Highveld grassland, characteristic of the region, has been transformed for urban and agricultural purposes. Large, isolated depressions underlain by impervious soils – known as pans – are typical wetland systems of the Highveld region which form habitat for many frog species. I undertook a coarse assessment of amphibian habitat in eleven pans (six representing urban and five representing agricultural areas) by measuring water quality at one point in time (electro-conductivity, temperature, pH, and concentration of sulphates, ortho-phosphates, ammonia, nitrates + nitrites and metals (Na, Mg, K, Ca)), and pan metrics, such as distance to tarred road, area of available terrestrial habitat and pan area. A frog survey using the pitfall-trap method of capture was also conducted at each of the sample sites for the purposes of evaluating frog biodiversity and spatial habitat utilisation. Evidence of acid mine drainage contamination, extensive dumping of household and building waste, nutrient enrichment and close proximity to roads with heavy traffic were found at urban sites. Agricultural sites were located significantly further away from tarred roads compared to urban sites but some were affected by deposition of eroded material from nearby cropland. A Pearson’s Correlation found a strong correlation between NO2 + NO3-N concentration and Amietophrynus gutturalis abundance across sites. Correlation matrices detected a strong, positive correlation between available terrestrial habitat adjacent to pans and pan proximity to tarred road with abundance of Cacosternum boettgeri, Pyxicephalus adspersus and Tomopterna cryptotis. At least six of the eight recorded frog species were captured at 80 m from the pan shoreline. Based on potential sensitivity of some species to available terrestrial habitat area, I recommend that buffer zones around pans should be between 100 and 500 m to ensure species persistence.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/18594 |
| Date | 25 May 2015 |
| Creators | Thomas, Ryan |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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