Mediterranean old-growth forests: the role of forest type in the conservation of epiphytic lichens

The present study investigated the effect of forest type on epiphytic lichen communities and selected indicator species, useful for long-term monitoring programs in Mediterranean forests. The results showed that only few species are common to many plots while others are locally rare. Epiphytic lichen diversity and communities were significantly influenced by forest type: Quercus cerris-dominated forests hosted a richer lichen flora, Fagus sylvatica-dominated forests showed the majority of rare species, while mixed forests, though poorly represented in the study area, hosted the majority of indicator species, revealing the presence of important and exclusive habitats. In particular, old established forests are characterized by both stand- and tree- continuity, while mixed forests offer a higher diversity of tree substrates. Our findings highlight the role of tree substrate variability for lichen colonisation. The presence of non-dominant tree species contributes to the variability of habitats and ecological niches. This allows the development of well preserved lichen communities compared to those of structurally less complex or even monospecific forests.