Correlations between vegetation, soil and geology in the semi-arid Bushmanland region of South Africa
Since the early 1900’s scientists have investigated the different factors that play a part in biodiversity and species richness with respect to vegetation composition. Plant species have different needs for nutrients, moisture as well as the amount of radiation that it receives. Therefore, the species composition for each environment will differ according to the chemical-, physical- and anthropogenic properties of that environment which include geological properties, soil properties, climate, topography as well as anthropogenic influences Limited knowledge is available with respect to the geology-soil relationships as well as relationships between vegetation and soils in the semi-arid regions of southern Africa. Existing information just refers to brief descriptions of the vegetation-soil interactions. The main aim of this study is to determine if there are relationships between vegetation, soil and geology in the semiarid Bushmanland region of South-Africa. The study was conducted on an area approximately 60 km south south-west of Kakamas in the Northern Cape of South Africa. This site was chosen based on the homogenous climate and topography, minimal anthropogenic influences, as well as its plant diversity and richness in soiland geological differences. In order to fulfil the main aim of this study, vegetation, soil and geological assessments and surveys were conducted. Soil forms the intermediate medium between geology and vegetation and has an extensive influence on plant ecology and diversity. Therefore, soil forms, pedochemical properties and physical characteristics were examined in detail. A vegetation assessment was done primarily to assess the role of parent material and soil medium in the development of plant communities and for the identification of vegetation habitats. This information was finally used to identify two-tier and three their relationships. Method 1 was used to identify four interrelationships between plant communities and either soil forms or geological formations and lithology. With the help of Method 2, a total of 19 three-tier combinations were identified. It was established that a three-tier relationship between grassland vegetation, calcic soils and surficial calcrete deposits is typical for the semi-arid Bushmanland region. Drainage systems in this part of South Africa are associated with shrubs and grasses (in particular Rhigozum trichotomum which dominates these areas) as well as cumulic soils.