Lichen extinction occurs at rapid rates as a result of human activity, although species could potentially be rescued by conservation management based on ecophysiological knowledge. The boreal old forest cyanolichen Erioderma pedicellatum currently occurs in few sites worldwide. To protect it from extinction, it is essential to learn more about it. The last remaining good European site is a canyon with a waterfall, in a low-rainfall region of Norway. Here, a spatially restricted population of 1500–2000 thalli dominates the epiphytic vegetation of a small number of Picea abies canopies. We were able to document that 1) E. pedicellatum grew on thin branches with higher bark pH than is normal for P. abies in a canyon that provided an unusual combination of very high light, high air humidity, and cool temperatures in the growing season. However, the species did not inhabit the main waterfall spray zone. 2) Erioderma pedicellatum had a high light saturation point, high CO2 uptake at high light (≥ 600 μmol m−2 s−1) and cool temperatures (5–20 °C), and experienced strong suprasaturation depression of photosynthesis when fully hydrated. 3) It showed good tolerance of desiccation and high light; it was slightly more tolerant than the morphologically similar, but more common cyanolichen Pectenia plumbea. 4) The European population in its sunny habitat had higher water holding capacity than previously recorded in slightly shaded rainforest populations in Newfoundland, consistent with acclimation to compensate for high evaporative demands. Understanding the ecological niche and responses to critical environmental factors is essential for action plans to avoid extinction of E. pedicellatum. Methods used in this study could also be applicable for ecological understanding of other threatened lichen species.

We assessed multiple environmental factors that might influence the population vitality of the epiphytic lichen Lobaria pulmonaria at the individual tree and habitat levels in partially overgrown wooded meadows in Estonia. A total of 301 trees of four species were sampled at nine study plots, using a stratified factorial scheme, 151 colonized by L. pulmonaria and 150 not colonized by L. pulmonaria forming the control group. We used the Generalized Linear Models (GLZ) to identify a complex of factors which predicts the probability of the lichen occurring on tree trunks and the presence of apothecia on its individuals. We employed the General Linear Mixed Model (GLMM) to study the relationship between cover of L. pulmonaria and environmental factors. The occurrence probability of L. pulmonaria on tree trunks increased with increasing light availability and height of deciduous shrubs near the trunk, and decreased with increasing distance to the nearest colonized tree. The host tree species and its trunk properties were also of importance, particularly the facilitating effect of the cover of bryophytes upon L. pulmonaria. The probability of occurrence of apothecia increased with maximum values of bark pH and cover of L. pulmonaria on the trunk. We conclude that partially overgrown wooded meadows are suitable habitats for L. pulmonaria. However, to maintain the vitality of these populations, a specific management scheme, preventing development of a dense stand, should be applied. Management requirements would include 1) selective cutting of overgrowing coniferous trees (particularly spruce), 2) preservation of adult and younger potential host trees within 10–20 m of colonized trees, 3) preservation of scattered deciduous shrubs in the vicinity of the host trees.

Wooded meadows with a history of traditional land use over thousands of years support a great diversity of various taxa. Today, however, high-species-rich communities in wooded meadows are threatened because of the cessation of traditional management in large areas. We studied lichen communities on 136 deciduous trees (Betula spp., Fraxinus excelsior and Quercus robur) in 12 wooded meadows in three regions of Estonia, and assessed the effect of habitat change due to the abandonment of traditional management on epiphytic lichen species composition, considering factors on three spatial scales: regional, habitat and individual tree. The variation partitioning approach in partial Canonical Correspondence Analysis (pCCA) revealed that most of the variation in species composition is described by the species of host tree and tree bark pH. Other tree level variables, foremost tree diameter, described as much of the compositional variation as geographic location (region) or environmental conditions in wooded meadows. Of the environmental factors studied, woodland canopy cover is the strongest predictor of the change in epiphytic lichen species composition from the community type of semi-open wooded meadows to species-poor communities characteristic of secondary forest. General Linear Model (GLM) analysis of the abundance of the 35 most frequently observed lichen species revealed that more than half of them (21) are influenced by site openness (canopy cover and/or undergrowth density), showing that increasing canopy cover has a negative effect on the abundance of epiphytic lichen species characteristic of traditionally managed semi-open wooded meadows. The results emphasize that the preservation of large old deciduous trees of various species and the maintenance of the semi-open structure of stands are vitally important for the protection of epiphytic lichen communities in wooded meadows.

Two surveys of the lichen and bryophyte flora growing on oak twigs from a Welsh and a Danish locality were compared with additional data on bark pH and % nitrogen in thalli of Hypogymnia physodes. Despite differences in climate and lichen flora, both sites showed a shift in the lichen communities from nitrogen sensitive (nitrophobe) to nitrogen tolerant (nitrophile) species, which was correlated with both increasing bark pH and an increase in total nitrogen in thalli of H. physodes. The floristic survey from Wales was a repetition of a study eight years earlier (Wolseley & Pryor 1999) now showing a loss of nitrophobes in all sites and the appearance of nitrophiles in pasture sites in 2003. This study demonstrates that lichens on twigs can be used as an early warning system to detect a response to changes in land management and nitrogen deposition.

The species richness and composition of lichens was quantified for four temperate broad-leaved tree species (Acer platanoides, Fraxinus excelsior, Tilia cordata and Ulmus glabra) in boreo-nemoral forests on the talus slope of the North-Estonian limestone escarpment (North-Estonian Klint). Thirteen study sites were distributed along the klint on a west to east gradient. The effects of tree and stand characteristics and geographical location of a stand on composition and diversity of epiphytic lichens were evaluated by multivariate analyses (DCA, CCA, pCCA) and by general linear mixed models (GLMM). Tree level variables (e.g. bark pH, bryophytes cover and host tree species) explained the largest fraction of the variation in lichen species composition. However, species richness and composition were significantly influenced also by the unique habitat conditions of klint forest (length of the forest fragment, proximity of the stand to the sea and height of the escarpment). A significant correlation between stand locality and lichen diversity on the tree bole was found which is most likely related to local air pollution gradients caused by alkaline cement dust and acid pollutants in the north-eastern part of Estonia.

The distribution of different ecological groups of lichens (acidophytes, ‘nitrophytes’, indifferent species) was compared on 1–24 year-old twigs of Abies sibirica sampled in the ‘pristine’ West Sayan and the polluted East Sayan Mountains (Krasnoyarsk District, South Siberia, Russia) to test their value as indicators of current pollution effects. Bark pH of twigs and bark chemistry (N, S, Ca, Mg, Al, Fe) were measured, and a preliminary estimate of emissions in the Krasnoyarsk District from livestock animal populations was calculated. In both regions, an unusually high twig bark pH and an abnormal species composition for A. sibirica canopy were found (e.g. Physcia aipolia, P. dubia, P. tenella, Phaeophyscia sp., Melanelia exasperatula and Candelariella vitellina), with P. tenella (East Sayan) and M. exasperatula (West Sayan) as dominants. The results confirm that the distribution of lichen species on Abies sibirica twigs is a valuable indicator of current changes in atmospheric conditions.