Lichen and bryophyte diversity is often exceptional in old rainforests of the temperate zone, but these forests occupy only a very small fraction of their former extent. Epiphyte diversity changes along the vertical gradient of a tree, but in Nova Scotia, Canada, no studies have investigated higher canopy strata, leaving the composition of epiphytes in these habitats uncharacterized. In this study, we explore arboreal lichen and bryophyte communities in the lower crown and lower bole of old eastern hemlock trees. We examined 27 trees at 9 sites across Nova Scotia, Canada. Each tree was surveyed using visual percent-cover estimates at the lower bole and in the lower crown. Single rope ascension was used to access the lower crown with minimal impact on epiphyte communities or tree cambium health. Habitat properties were also recorded, including bark pH, tree girth and height, and canopy cover. Results showed higher pH, and greater richness and cover of macrolichens in the lower crown compared to the lower bole, whereas bryophyte species richness and microlichen cover were both greater on the lower bole of host trees compared to the lower crown. Macrolichen diversity, as represented by Shannon's index (H'), did not differ in relation to habitat, but it increased from the northeast to the southwest of the province. Our results provide a baseline for lichen and bryophyte diversity on old eastern hemlock.

Lecanora exspersa Nyl., a corticolous sterile sorediate crustose lichen previously known only from sparse collections in the mountains of Eurasia, is here reported as new to North America. We collected eight specimens attributable to this name as a part of our recently launched comprehensive lichen inventory of the southern Rocky Mountains and adjacent high plains of Colorado. Chemical and morphological study of these specimens as well as a molecular phylogeny containing our specimens, accessions of L. exspersa from Europe, and other sorediate members of the genus with which L. exspersa may be confused, helped to confirm its identification and placement within the L. subfusca group. This new record for North America is characterized by its thin, grey, smooth to verruculose thallus on bark or wood, its discrete, circular mint-green soralia that erupt from verrucae (these becoming larger and plane with age and often bearing a prominent thalline rim), and its production of atranorin and nephrosteranic acid. We provide discussion along with a dichotomous key to help facilitate the identification of this species and other sorediate species of Lecanora from western North America. Continued fieldwork followed by herbarium studies of the Colorado lichen biota will, we predict, yield many new additional records as in the present report as well as species new to science.