An assessment of epiphytic lichen diversity and environmental quality in Knocksink Wood Nature Reserve, Ireland

Epiphytic lichens are extremely sensitive to environmental perturbations. This research work has adapted and applied recently developed methods of assessing epiphytic lichen species diversity to the Irish semi-natural acidophilous woodlands of Knocksink Wood Nature Reserve, Enniskerry, Co. Wicklow, Ireland. The study has focused on the differences that arise in relation to acidophilous oak versus ash-hazel woodlands at Knocksink. The frequency of occurrence of lichen species on a defined portion of tree bark is used as an estimate of diversity and to evaluate the degree of environmental stress on the sensitive lichen community. Epiphytic lichens were investigated across the oak woodland (Blechno-Quercetum petraeae) and ash-hazel woodland (Corylo-Fraxinetum) and a total of 30 lichen taxa were recorded on trunks and 11 on twigs and branches. Results showed that 26 epiphytic lichen taxa were found on the oak tree trunks in the oak woodland and 14 epiphytic lichen taxa on the ash tree trunks in the ash-hazel woodland. The genera with the highest number of species were Opegrapha, Pertusaria and Arthonia for tree trunks and Parmelia, Hypogymnia for tree canopies. Lichen diversity (LD) results were interpreted in terms of environmental assessment and a relatively low environmental quality was detected. Further comparison to other broadleaf woodlands in Ireland revealed a poverty of epiphytic lichen flora at Knocksink. Oak trees in the oak woodland were recognized as richer in lichen flora on the trunk area than ash trees in ash-hazel woodland. However, the epiphytic lichens in the ash-hazel woodland showed a higher LD score than that in the oak woodland at Knocksink Wood. This research advances understanding of environment influences on sensitive epiphytic lichens and their abundance and distribution in Irish broadleaf woodlands.