A Review of Lichens in Metal-Enriched Environments

Abstract

The importance of mineralogy in determining lichen assemblages occurring on metalliferous rocks and derived soils is discussed with reference to environments enriched in metals from mine and smelter wastes and other sites involving human activities. A study of lichens growing on Cu and Fe sulphide-rich rocks in Scandinavia is presented. This data suggests that the composition of the lichen communities is governed by mineralogy, which influences the mobility and availability of Cu²⁺ and Fe²⁺ in the environment, rather than the total concentrations of either metals within the substratum. A new lichen community, the Lecideion inopis Purvis, is described characterized by the faithful species Lecidea inops, Psilolechia leprosa and several Cu-rich ecotypes. This community occurs alkaline environments where Cu is fixed predominantly as a secondary hydroxide or carbonate. Conversely, low pH, Fe sulphide-rich environments, where Cu may also be present, are characterized by the Acarosporion sinopicae, which includes several species with a rusty colouration. Contrasting assemblages rich in terricolous ephemeral species, especially Vezdaea spp. occurring in Pb/Zn-rich environments, and the comparatively species-poor assemblages on Cr and Ni-rich ultrabasic rocks, are also reviewed. Although mine spoil heaps and other mineralized environments are perceived in human terms as toxic, they may support a diversity of lichens, including rare taxa restricted to these sites. The systematic description of these lichen communities in relation to rock mineralogy and chemical processes are necessary if physiological tolerance and speciation are to be understood.