Standardized lichen surveys were conducted on 849 trees in 132 ecological long-term observation plots in the Swiss Plateau and Pre-Alps: 262 lichen taxa were identified, 64 (24%) of them sorediate crustose species. Their mean percentage of the flora on individual trees and in individual plots was even higher. The mean percentage of crustose lichen species with vegetative propagules, such as soredia, was per plot significantly higher in the Pre-Alps than in the Plateau, higher in forest than in non-forest areas, and, according to the vegetation belts, lowest in the colline-submontane zone. It was found that the biodiversity of lichens could not be determined without considering the sorediate crustose lichens. Furthermore, by performing standardized surveys of all taxa, the occurrence of the following species in Switzerland was confirmed for the first time: Cliostomum leprosum, Fuscidea arboricola, Fuscidea pusilla, Hypacenomyce leucococca, Hypocenomyce sorophora, Lecanora norvegica, Lepraria eburnea, Lepraria elobata, Lepraria jackii, Lepraria obtusatica, Lepraria rigidula, Pertusaria borealis and Rinodina griseosoralifera. Seven taxa that displayed distinctive chemistry, could not yet be identified.