Meetings of the Royal Botanical Society of the Netherlands

An attempt has been made to present a picture of the epiphytic lichen flora and vegetation in the surroundings of’s-Hertogenbosch, Noord-Brabant, The Netherlands at the beginning of this century, mainly based on herbarium material collected at that time by J. H. Wakker. To allow a comparison with the present situation, a field survey in the study area was made in 1974. The area’s epiphytic lichen flora showed a strong decline: of a total of 115 species collected by Wakker, only 46 species were found recently. As the Wakker samples usually contained more than one species, they could be treated as vegetation relevees. Thus some epiphytic lichen communities occurring in the area at the beginning of this century could be identified. Most of these communities have become now much impoverished or have disappeared entirly, especially those on acid substrates. Only one community (dominated by Lecanora conizaeoides) has strongly expanded. Considering the ecology of the species it was found that species with a narrow ecological amplitude, whose occurrence was limited to only one community, have usually disappeared. Species with a wider amplitude are still being found in the area, but their occurrence is often limited now to substrates with a high pH value.