Patterns of vascular plant diversity were studied at different spatial scales (100 m2, 1000 m2, 1 ha and 1 km2) along the BIOTA Southern Africa transects from the Kavango in northern Namibia to the Cape of Good Hope in South Africa, covering six biomes in the western part of southern Africa and a steep rainfall gradient. We analysed family richness, species richness, as well as z-values (i.e. the slopes of power-law species-area relationships as measures of β-diversity) on all these spatial scales in order to provide baseline data for biodiversity assessment in the region and an understanding of the influence of potential drivers on various dimensions of biodiversity. For the last purpose, we related our biodiversity parameters via correlations, linear and polynomial regressions as well as analyses of variance (ANOVAs) to potential drivers such as geography, landuse, climate, and soil. Finally, we used the time-series data of the BIOTA Observatories to analyse whether a change in species richness occurred during the project period.