Boreal and arctic siliceous inland cliff

Siliceous (rich in quartz and silicate minerals such as mica or feldspar) rock walls and cliffs in the boreal and arctic biogeographical regions, excluding supralittoral cliffs adjacent to the sea with salt spray influence (habitat B3.1) as well as very wet, dripping vertical rocks (habitat H3.4). These siliceous cliffs in the North chiefly consist of granite, gneiss and other kinds of hard crystalline acid rock. Soft mica schist is also common. Volcanic rocks occur locally.

The vegetation consists of a limited number of vascular plants in rock crevices and on ledges, while epilithic bryophytes, lichens as well as micro-algae occur on dry or wet rock faces, overhangs and in all kinds of sheltered microsites. Although these rock types are all base-poor, they show marked variation in their chemical composition and can harbor hundreds of different lichens and bryophytes and a range of plant communities. For example, lichen communities on quartzite and diorite are composed largely of different species. The most base-poor rocks include sandstone and quartzite, followed by granites, gneisses, and granulites. Rocks with reduced acidity include phyllite, mica schist, gabbro, and diorite; they host species that are slightly more nutrient demanding. In the boreal zone, diabase and amphibolite represent more base-rich rock types that form transitions between base-poor and base-rich habitats (this type and H3.2a). However, in most cases these cliffs do not host remarkable calciphilous communities, like on limestone cliffs.

Usually, the highest diversity of species is found in cliffs with the highest geomorphological diversity. Especially lichen and bryophyte communities vary according to microhabitats like rock slopes, vertical and overhanging rock faces, cavities, shelves, and ledges, as well as crevices of different size or fissures on walls. For example, the most bare and sunny walls are dominated by crustose and foliose lichens and small cushion-forming bryophytes, whereas shady vertical surfaces are covered by mat- or cushion-forming bryophytes. The gloomiest cavities may harbor fan-like bryophytes (e.g. Neckera spp.), powdery lichens or algae. Crustose and foliose lichens are well represented with numerous genera; particularly species-rich are, e.g., Lecanora, Parmelia s.l., Rhizocarpon, Stereocaulon, and Umbilicaria. Among the mosses, numerous species of Grimmia, Racomitrium, Schistidium, Andreaea and many other genera occur. The vegetation of vascular plants is rather poor but small ferns (Asplenium spp.) may occur, except in the far north.

Specific plant communities can be recognized on Fe and Cu sulphide-rich rocks, where the specialized flora includes copper moss Mielichhoferia elongata and lichens that favour iron-containing rocks (e.g. Acarospora sinopica, Lecanora epanora, Lecidea silacea, Miriquidica atrofulva, Tremolecia atrata). Bird nesting cliffs (excl. coastal bird cliffs) have also a special species composition, as they gain extra nutrients from guano and host so-called ornithocoprophilous plants.

Boreal and arctic siliceous cliffs occur in Iceland, northern Scotland, the Shetland, Orkney and Faroe Island groups, Svalbard, Fennoscandia and the northern Baltic region, moreover in Greenland, northern Russia and circumpolar in North Siberia and North America. In the boreal lowlands, cliffs are usually small and low and located in forest environments, whereas in the Scandinavian Mountain range and in the arctic zone the most massive cliffs occur on open mountain slopes and may be hundreds of meters high and kilometers long.

Indicators of good quality:

Boreal and arctic siliceous cliffs are of particular importance for cryptogams, in particular for lichen and bryophyte diversity. The biodiversity varies between regions, phytogeographic zones and altitudinal belts. The species diversity varies enormously also in entirely natural communities in cliff habitats. Usually, the smallest rock formations with monotonous microtopography and little variation in rock types show low diversity, whereas larger cliff complexes with heterogeneous geomorphology and varying rock types may represent local biodiversity hotspots. Therefore, low species diversity or absence of rare species should not as such be interpreted as an indicator of low habitat quality, unless it is caused by anthropogenic influence.

The following characteristics may be used as indicators for assessing trends in quality:
•    Occurrence of rare species of lichens, bryophytes and phytogeographically significant vascular plant taxa, 
•    Presence of sizable open exposed rock with species-rich bryophyte carpets and lichen crusts, and of different aspects of rock walls, different exposure to insolation, moisture and rock structures such as overhangs, cavities, rock shelters, ledges
•    Presence of indicators of good air quality, e.g. usneoid lichens or Lobaria spp.
•    Contact with natural habitats such as screes, boulder fields, and pioneer grasslands 
•    Absence of quarrying and control structures 
•    Absence of garbage dumping and anthropogenic nutrient input from above the cliff
•    Absence of rock climbing facilities
•    Absence of alien species

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats