Borovichev E.A. Botanical excursion on the Northern Soroya. Hammerfest, 2014.

Lichens Lichens are a puzzling group o f organisms. Literally, they represent ‘mini-ecosystems’ which consist o f two separate organisms - fungus and a photosynthetic partner growing together. The lichen thallus is a symbiotic formation composed o f a photobiont or phycobiont consisting o f cells o f green algae, commonly Trebouxia and\or blue-green algae, commonly Nostoc, and a mycobiont fungus. Lichens vary in colour, from nearly white to tints o f gray or brown, red, orange or yellow. The most brightly colored lichens are usually to be seen on rocks or tree bark in open sunny habitats. Color o f lichens is thought to be of importance in regulating temperature, since certain pigments scatter or reflect radiation from the sun protecting the sensitive algae layer, and keeping the lichen body cooler (Brodo et al., 2001 ). Lichens comprise a very important part of subarctic and arctic ecosystems. They are often the first organisms to colonize exposed rocks high in mountains and in tundra zone. They start the slow process weathering barren rocks and incorporating minerals into their bodies. This makes nutrients available to other forms o f plant life. Lichens occur on various substrata, on the surface o f bark, stone, fine earth, etc. Individual lichen can be more than a thousand years old. Lichens are remarkably resistant to changes in environmental conditions and can remain dormant for long periods if conditions are not favorable for their growth. No one knows for certain how many lichen species there are on Earth, estimates vary from 13500 to 30000 species (Purvis, 2010). It is not difficult to discover new records and species o f lichens even in comparatively well studied regions, for example - in the north o f Europe. The "Norwegian lichen flora is probably one o f the best studied in the world. They have recorded 1985 species (Timdal et al., 2010) however, the lichen flora o f the Soreya Island has not been properly investigated. To read about lichens one need to know some special terms concerning morphology and biology o f lichens. Thallus is the lichen body. Thallus is attached to its substratum by short root like organs called Tremolecia atrata, one o fthe commonest epilithic crustose lichens ofthe Soroya Island Fruticose lichen Pseudephebepuhescens grows on the exposed siliceous rock 89