A survey of epiphytic species on annual increments of Quercus petraea twigs in a west Wales woodland has shown that distribution of lichen species and rates of succession are affected by a range of environmental conditions. Lichen communities were recorded for 1–15 years on randomly sampled twigs along marked woodland boundaries affected by a range of climatic and management conditions. Results show that there is a correlation between environmental condition and lichen communities of twigs, and that indicator species can be used to detect trends towards acidification or eutrophication.