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The present study was undertaken to assess species number and turnover of soil lichens occurring along the BIOTA Southern Africa transect, analyse their association with environmental parameters and to identify floristic affinities among the Observatories. In total, 73 soil surface lichen species were recorded. Species richness was highest in the Succulent Karoo, followed by the Savannah and Desert biomes, while soil lichens were absent (or scarce) in the Nama Karoo biome. The Observatories subject to winter rainfall were lichenologically clearly distinct from the ones in the summer rainfall area. In order to identify the environmental factors most related to lichen richness at the different Observatories, a multivariate analysis with selected climatic (temperature, air humidity and rainfall) and soil (acidity, EC) parameters, and altitude was carried out. While humidity, soil salinity, air temperature and altitude proved to be significantly correlated with lichen richness in most sites, soil acidity and precipitation amount were relevant only in few cases.