Diversity and ecology of soil lichens in the Knersvlakte

The lichen vegetation forming biological soil crusts is described for the first time for a semi-desert area of the Republic of South Africa (Knersvlakte, Namaqualand). Thirty- five terricolous lichen taxa were recorded. Fifty-two percent of the lichens are endemic to Namaqualand according to current knowledge. Squamulose and crustose lichens were the most common (over 60% of taxa) and most contained green algal photobionts. Three main communities were distinguished: 1) a widespread community composed by Collema coccophorum, Psora aff. crenata, Placidium tenellum and P. squamulosum; 2) a rare community characterized by foliose lichens belonging to Xanthoparmelia, Neofuscelia and Paraparmelia; and 3) a rare, crustose community formed by Caloplaca sp. (''C. sp. 1''), Toninia sp. (''T. sp. 1''), T. ruginosa and Buellia sp. (''B. sp. 2''). The lichen taxa and vegetation of the study area are unique and are threatened by land management practices and changing climate.