Distribution and habitat ecology of the threatened forest lichen Lobaria pulmonaria in Estonia
Lobaria pulmonaria is a widely used as an indicator species of undisturbed old-growth forests ecosystems, but the knowledge about its habitat ecology is still highly fragmented. To quantify the distribution, habitat preference and host tree specificity of Lobaria pulmonaria we utilised data from databases and field surveys in Estonia. The number of L. pulmonaria localities is the highest in the densely forested regions, concentrated mainly in small forest patches defined as ‘ecologically highly valuable’. The species grows mostly on deciduous trees, particularly on aspen (Populus tremula). L. pulmonaria is most common in oligo-mesotrophic boreal, eutrophic boreo-nemoral and in eutrophic paludifying forests, and prefers forests with an average age of trees more than 100 years. In addition, we found that younger stands could be suitable habitats for L. pulmonaria if the structure of the stand is comparable to mature stands. In spite of the many localities of L. pulmonaria in Estonia, the species is still threatened because (1) the rotation period of tree stands is short, (2) it is abundant in forest types which are rare or under strong economic pressure, (3) and it prefers host trees which have a restricted distribution in Estonia or are not favoured in forest management practice.