Natural recovery of dwarf shrubs following topsoil and vegetation clearing on gravel and sand plains in the southern Namib Desert

Abstract

Natural recovery of vegetation in arid areas is expected to take long time spans. Relatively rapid turn-over times have, however, been reported in Succulent Karoo vegetation in southern Africa, suggesting a certain resilience. This study investigated natural recovery of coastal Succulent Karoo shrubland five, six and seven years after geological sampling in the southern Namib Desert. The geological sampling resulted in a grid-pattern of cleared and topsoil stripped 5 × 5 m areas in three study sites in slightly different environmental settings. Using plant species richness, vegetation cover, plant species composition and an adaptation of dominance–diversity curves as measures, the initiation of natural recovery was demonstrated at all three study sites. Calcrete and gravel plain vegetation showed the best recovery, followed by sand plain vegetation and gravel plain vegetation in a deflation valley (wind corridor). An adaptation of dominance–diversity curves proved useful in illustrating successional patterns in these sparsely vegetated, arid dwarf shrublands and provided a tool to extract information for species-level management intervention. An exceptional rainy season, a large edge effect due to the localised impact of the geological sampling, intact subsurface structure and natural sand deposition are hypothesised to have favoured the initiation of natural recovery in this arid area.