Abstract:
Sekhukhuneland is an area of diverse geology and rich phytodiversity. This region harbours the world's
largest reserves of chromium and platinum ore. A literature review of heavy metal soils is presented as
introduction and motivation for this dissertation. Special attention was given to the effects of chromium
on plants, due to its abundance in the Sekhukhuneland study area. Floristic elements of the
Sekhukhuneland study area were determined by means of field work, herbarium studies and literature
surveys. Approximately 50 endemic and 70 near-endemic taxa were identified for this region. Families
such as Euphorbiaceae, Fabaceae, Liliaceae and Vitaceae proved the most prolific in endemic taxa.
Distribution ranges for each of the floristic elements were mapped and analysed with a Geographical
Information System. Plant distributions showed distinct floristic patterns within Sekhukhuneland, and
links with other mountainous regions of the Northern Provinces of South Africa. Percentage surface cover
of all the various geological substrates (predominantly Rustenburg Layered Suite and Transvaal Sequence)
were calculated for each quarter degree grid in the study area. A correlation was found between the
region's percentage endemism and percentage surface cover of ultramafic substrates. The ultramafic
substrates, norite, anorthosite and pyroxenite, showed a significant positive correlation with percentage
endemism. The high number of endemics and the endemic-ultramafic correlation in certain quarter
degree grids, enabled the identification of focal areas of endemism in the study area. These focal areas of
endemism support the status of Sekhukhuneland as an important Centre of Endemism.
