Savannahs regulate an agro-ecosystem crucial for the production of domestic livestock, one of the main sources of income worldwide as well as in South African rural communities. Nevertheless, globally these ecosystem functions are threatened by intense human exploitation, inappropriate land use and environmental changes. Leaf area index (LAI) defined as one half the total green leaf area per unit ground surface area, is an inventory of the plant green leaves that defines the actual size of the interface between the vegetation and the atmosphere. Thus, LAI spatial data could serve as an indicator of rangeland productivity. Consequently, the accurate and rapid estimation of LAI is a key requirement for farmers and policy makers to devise sustainable management strategies for rangeland resources. In this study, the main focus was to assess the utility and the accuracy of the PROSAILH radiative transfer model (RTM) to estimate LAI in the South African rangeland on the recently launched Landsat 8 sensor data. The Landsat 8 sensor has been a promising sensor for estimating grassland LAI as compared to its predecessors Landsat 5 to 7 sensors because of its increased radiometric resolution. For this purpose, two PROSAIL inversion methods and semi- empirical methods such as Normalized difference vegetation index (NDVI) were utilized to estimate LAI. The results showed that physically based approaches surpassed empirical approach with highest accuracy yielded by artificial neural network (ANN) inversion approach (RMSE=0.138), in contrast to the Look-Up Table (LUT) approach (RMSE=0.265). In conclusion, the results of this study proved that PROSAIL RTM approach on Landsat 8 data could be utilized to accurately estimate LAI at regional scale which could aid in rapid assessment and monitoring of the rangeland resources. / Environmental Sciences / M. Sc. (Environmental Science)

MSc (Botany) / Department of Botany / Plant populations are determined by many elements that impose demographic filters. Following disturbance, in African savanna woodland trees regenerate both sexually and vegetatively. Vachellia karroo (Hayne) Banfi and Galasso, family Fabaceae and sub family Mimosideae, commonly known as “sweet thorn” or “soetdoring” (Afrikaans), is a leguminous shrub common throughout Southern Africa. Its distribution range is from the Southwestern Cape northwards into Namibia, Angola, Botswana, Zambia and Zimbabwe. It is a pioneer species and has the ability to encroach rapidly into grassland grazing areas. Therefore, V. karroo is considered the most important woody invader of grasslands in South Africa. This study aimed at investigating the population biology and ecology of V. karroo in the clay waterlogged site of the Nylsvley Nature Reserve. Plant height, stem circumference, canopy cover, distance between individuals were measured and disturbance levels on individuals of V. karroo were estimated during sampling. The results showed that the population of V. karroo display an adequate growth curve thus implying that the population of V. karroo in the Nylsvley Nature Reserve is healthy and viable. More mature healthy individuals were found in September and December, than during June and July; this is obviously because early summer season, and in September most of the savanna plant species were starting to actively recover from the winter dry season. This is confirmation enough that the population of V. karroo is expanding in the clay waterlogged areas of Nylsvley Nature Reserve.

A vegetation survey was conducted on the newly acquired farm portions of the farm Doornrandje 386 JR, which are being incorporated into Gauteng Department of Agriculture and Rural Development’s protected area expansion. This study provides an ecological basis for establishing an efficient management programme for the area. From a TWINSPAN classification, refined by Braun-Blanquet procedures, five plant communities were identified. A classification and description of the major plant communities is presented. Descriptions of the plant communities include characteristic species, as well as prominent and less conspicuous species of the tree, shrub, herb and grass strata. Floristic analyses of the vegetation and a biodiversity comparison of the different plant communities found on the farm are also undertaken. This study proves that the extended land incorporated into the Reserve contributes to the biological diversity of the study area. / Environmental Sciences / M. Sc. (Environmental Science)

A vegetation survey was conducted on the newly acquired farm portions of the farm Doornrandje 386 JR, which are being incorporated into Gauteng Department of Agriculture and Rural Development’s protected area expansion. This study provides an ecological basis for establishing an efficient management programme for the area. From a TWINSPAN classification, refined by Braun-Blanquet procedures, five plant communities were identified. A classification and description of the major plant communities is presented. Descriptions of the plant communities include characteristic species, as well as prominent and less conspicuous species of the tree, shrub, herb and grass strata. Floristic analyses of the vegetation and a biodiversity comparison of the different plant communities found on the farm are also undertaken. This study proves that the extended land incorporated into the Reserve contributes to the biological diversity of the study area. / Environmental Sciences / M. Sc. (Environmental Science)