Hydrological effects of buried palaeosols in eroding landscapes: A case study in South Africa

Palaeosols have long been studied as valuable records of past climate and landscape changes. The influence of palaeosols on the functioning of present-day landscapes is receiving closer attention due to the relevance of palaeosols on long-term hydrological processes and the future hydrological and erosive response of catchments. This study describes a sequence of interbedded colluvial sedimentary deposits and buried palaeosols exposed by gully erosion in the Drakensberg escarpment foothills in KwaZulu-Natal province, South Africa. Model simulations are then presented that explore present-day hydrological effects of pedogenetic and textural differentiation under conditions of groundwater lowering caused by gully erosion at 14 sites. The results suggest that the colluvial deposits and palaeosols cause a significant increase in total annual drainage from most of the 14 studied sites compared with similar sites without textural or structural differentiation. In the simulations, sediment deposition, not palaeosol formation, has the most profound influence on the present-day hydrological functioning of the catchment: a true deposystem service. The effects of the limited observed palaeosol development on soil water holding capacity and actual soil water storage appear to be negligible