World distribution: Erioderma pedicellatum is an amphi-atlantic species which is known from the Atlantic coast of North America (New Brunswick, Nova Scotia, and Newfoundland; Ahti & Jørgensen 1971, Jørgensen 1972a, Maass 1980, 1983) and from Scandinavia (Ahlner 1948, Jørgensen 1990, Holien et al. 1995). In Sweden it was known only from Värmland (Ahlner 1948) where it is now regarded as extinct (Aronsson et al. 1995)
Ecology: Results. The substrate was exclusively small twigs of Picea abies. The habitats were very humid, shaded forests in small brook ravines on marine sediments with a field layer dominated by large ferns and herbs. In both localities the individuals were growing close to naturally occurring gaps (small swamps) which might indicate demands for rather high incident light as well as a stable, high humidity. Discussion. According to Maass (1980, 1983), E. pedicellatum is a species that demands stable and high humidity. It tolerates low winter temperatures, and may therefore be regarded as a hygric oceanic and thermic 'continental' species (cf. Holten 1988). It is the only true boreal species of a genus with a tropical and subtropical main distribution. While the species has been recorded only on twigs of P. abies in Scandinavia, it has also been found on the trunk, mainly of Abies balsamea, in North America. Other noteworthy threatened lichens like Pannaria ahlneri and Pseudocyphellaria crocata have been found associated with E. pedicellatum, both in North America and in Norway. Erioderma pedicellatum is very rare and declining also in North America (Maass 1980, 1983). According to Maass, the establishment, i.e. the resynthetisation of new thalli, is possibly an extremely critical stage in the life cycle of this non-sorediate species. The photobiont, a cyanobacteria of the genus Scytonema, is not known neither in its free-living form nor from any other lichen species growing in the forests containing E. pedicellatum in central Norway. Another important ecological observation mentioned by Maass (1980) is that E. pedicellatum seems to be restricted to fire-free refugia.
Threats: Results. The three Norwegian localities recorded by Ahlner (1948) have been clearcut and replanted. The two new localities are threatened by logging. Discussion. Logging not only directly removes possible substrates, but also indirectly alters the microclimate in adjacent woodland areas. This was clearly demonstrated at the site Brattmoviken in Värmland, Sweden which was protected in the early fifties (Ahlner 1954). The surrounding forest was clearcut, causing desiccation of the microhabitat and death of the E. pedicellatum population which counted several hundred individuals (Ahlner 1954, Jørgensen 1990). Like other cyanophilic lichens, E. pedicellatum is probably highly susceptible to atmospheric pollution. However, as Grong is situated within the part of Norway with the lowest known sulphur concentration in the precipitation (Statens forurensingstilsyn 1992), this is unlikely to be a threat for this species in Norway
Status: The three old collections from Norway were made in 1938 and 1939 (Ahlner 1948), and the species has since then not been observed in Norway until the summer of 1994 when it was discovered in two localities with only one specimen in each (Holien et al. 1995). The specimen in the Overhalla locality (3803) disappeared in the winter 1994/1995
Specimens in other herbaria, litterature, etc.