The origin and geomorphological significance of earth mounds in the Mkhuze wetlands, KwaZulu-Natal.
The study sheds light on the occurrence and development of earth mounds in the Mkhuze Wetlands, KwaZulu-Natal. It compares this system with the Okavango Delta. The conceptual model developed by Ellery and co-workers for mima mound development in the Okavango Delta is said to have worldwide applicability (Ellery at al. 1998). This study investigates the applicability of this model in the formation and development of earth mounds in Mkhuze Floodplain. The activities of termite species are regarded as responsible for the formation of earth mounds in the Okavango Delta. The Mkhuze Wetlands represent one of South Africa’s most pristine wetland systems (Cowan 1995). They have also been declared as part of the Isimangaliso Park, a World Heritage Site (Cowan 1995). Many studies have been conducted in Mkhuze Wetlands in order to gain more knowledge and understanding of how the system functions, so that it can be managed wisely. Although termites are thought to be associated with these features (Adams 2004), very little has been done to assess or even verify if the changes in soil chemistry and mineralogy across these mounds can be linked to termite activities. This study investigates the soil mineralogy and physico-chemical properties across mounds found in the Mkhuze Wetlands and determines through its findings any possible link to termite activities. Most mounds in Mkhuze were identified in the intermittently flooded region of the floodplain. Results from particle size analysis were indicative of a bimodal distribution in mound soils. Two major components in mounds were a combination of clay size particles, silts and very fine sand, and fine to medium sand, with traces of coarse sand. There was a significant difference in the distribution of soil particle size fractions found on mounds compared to soils adjacent to the mounds. The chemical composition of the clay size particles found on the mounds was different when compared to that found in adjacent soils. There were also higher concentrations of minerals derived from solute chemicals found in the centre of the mounds at depth. Precipitation of solutes in mid regions of the mounds is thought to attest to spatial evapotranspiration rates across mounds. Although no direct evidence of termites was found in the mounds, there are indications that termites have been responsible for the development of the mounds and that in certain mounds plants have led to mound growth due to precipitation of solutes driven by evapotranspiration.