FREQUENCY, DIVERSITY AND ECOLOGICAL STRATEGIES OF EPIPHYTIC LICHENS IN THE SWISS CENTRAL PLATEAU AND THE PRE-ALPS

To identify representative quantitative criteria for the creation of a future Red List of epiphytic lichens, 849 trees in 132 long-term ecol ogical observation plots in the Swiss Central Plateau and the Pre-Alps were surveyed by standard sampling. Based on the trees, frequency dat a of the lichen taxa observed are described by the log series model, i ndicating the controlling effect of few ecological factors. Based on t he plots, four classes of scarcity, each comprising 25% of the species , were established. As a contribution to the development of a national , representative survey of lichens, alpha-diversity (species richness, species density) and beta-diversity (dissimilarity) were calculated i n terms of region, vegetation formation, vegetation belt and for their combinations. Differences in lichen diversity between the Central Pla teau and the Pre-Alps were caused by the bigger elevational range in t he Pre-Alps, which resulted in a higher species richness. alpha-Divers ity of forest and non-forest were similar, whereas each vegetation for mation showed one third of its species restricted to it. The contribut ions to the total lichen diversity of crustose, foliose and fruticose as well as of generative and vegetative species was calculated. Specif ic features along the altitudinal gradient of vegetation belts emerged : the percentage of crustose and generative lichens declined with ever y altitudinal step, increased in fruticose and vegetative lichens, and was the same in foliose species. (C) 1997 The British Lichen Society.