An area with a characteristic lichen flora ranging from complete absence to a full complement of foliose and fruticose species, depending on the level and type of air pollution present in the area. The standardized lichen zones for England and Wales range from zone 0 (complete absence), typical of heavily polluted industrial areas, to zone 10, in which bearded lichens (e.g. Usnea and Ramalina species) are present in association with many other species. Zone 10 is typical of unpolluted areas in which virtually no sulphur dioxide, fluorine compounds, or other air pollutants are present.
Subjects: Plant Sciences and Forestry — Ecology and Conservation.