Summary

Sustainable soil management requires information on present day natural rates of erosion in order to develop generally accepted management goals. But, data on rates of natural erosion from uncultivated land under current climate conditions is difficult to find. This holds especially for southern Africa, where human induced soil erosion is presently believed to exceed natural rates by one to two orders of magnitude.

In the framework of this joint German-South African research project we aim to establish natural erosion rates for an African savanna by investigating longterm denudation, contemporary sediment yield and sediment sources in a nature conservation area, i.e. the Kruger National Park (KNP). The KNP is particularly suited for this study because the area was set aside for wild life conservation over 100 years ago and never experienced agricultural development and disturbance. Furthermore, KNP is an exceptionally well documented area providing a number of data sets relevant to studies on erosion (e.g., DEMs, geology, soils, vegetation and vegetation change, fire records, climatological records, drainage, aerial photos). Taking into account variation in endogenetic (geology, soils and relief) and exogenetic (climate and vegetation) drivers of erosion the objectives of this research project are:
1) Determination of contemporary average near-natural sediment yield rates on the catchment scale based on volumetric mapping of the deposits in reservoirs (total N = 20) established 40 to 80 years ago.
2) Determination of the late Quaternary rates of erosion using cosmogenic nuclide dating of river deposits upstream of the reservoirs
3) The identification of major sediment sources within the catchments using sediment fingerprinting methods (geochemistry, magnetic susceptibility) in order to apportion sediment yield to contributing areas of selected reservoir catchments.

Generally, the anticipated results will advance the understanding of the late Quaternary geomorphodynamic evolution and trajectories of savanna environments. Specifically, they will provide SANParks with spatially distributed data on sediment production within the KNP and support the development and refinement of Thesholds of Potential Concern (TPC) for degradation. When compared to the abundant data on soil erosion from cultivated land, the results will provide a base for an assessment of the soil preservation ecosystem services of KNP and nature conservation areas in general. In addition, the results are of importance for the foundation and justification of soil and water management goals in the dry savanna regions of South Africa and neighboring countries (e.g. the Greater Limpopo Transfrontier Conservation Area).

Student involvment

There will be the opportunity for students from FSU Jena, Germany, and Rhodes University, South Africa, to participate in field and lab work pertinent to the study.

Publications

The results of the reconnaissance survey conducted in 2008 are published in:

Presentations (up to 2017, only)