Intensive grazing of Kalahari rangelands has led to woody plant encroachment, notably of Acacia mellifera and Grewia flava. The mechanisms causing this process, and the ecological stability of woody plant encroached ecosystems, remain uncertain. Past studies suggest that canopy-soil relations may enhance woody plant competitive dominance. Key words: Acacia mellifera, cyanobacterial soil crusts, Grewia flava, Kalahari, woody shrub encroachment.