Arctic terrestrial ecosystem
Arctic land is predominantly treeless permafrost with large areas of tundra. The Arctic environment is highly heterogenous, with for example dry stony ridges, periglacial features, areas of late snow lie, heath, or wet moss, all in close proximity (Thomas et al., 2008). Large areas have recently been reworked by glacial action and possess continuous underlying permafrost, influencing soil hydrology.
On a regional basis, northern areas consist largely of polar desert characterized by low precipitation and a short snow-free growing season. In Svalbard and Franz Josef Land vascular plant cover is often restricted to less than 15% (Aleksandrova, 1983; Jónsdóttir, 2005; Cooper, 2011). Dwarf shrub tundra or heath, such as species as Dryas octopetala and Cassiope tetragona, are characteristic along the west coast of Svalbard and the southern areas of Novaya Zemlya. In all three archipelagos, bare soil often possesses a “biological crust” of cyanobacteria, bacteria, algae and lichens.
Vascular plant diversity totals 74 species in Franz Josef Land (Tkach et al., 2008), 184 in Svalbard (http://www.svalbardflora.no/) and 216 in Novaya Zemlya (Tkach et al., 2008). Bryophyta (mosses, liverworts and hornworts) form an important component of the environment in the Arctic (Turetsky et al. 2012), with 373 accepted species in Svalbard (Frisvoll and Elvebakk, 1996). Lichens are more speciose, with 778 recorded species in Svalbard (see lichen chapter). Similar recent inventories of bryophytes or lichens of Novaya Zemlya and Franz Josef Land are not available.
On a landscape scale, the habitat is comprised of a heterogeneous mosaic (Jónsdóttir, 2005). The ridge tops, blown free of winter snow, or areas kept clear of snow by wind eddies, may experience winter temperatures approaching -40°C, while organic soils protected under deeper snow do not exceed temperatures below -10°C (Coulson et al., 1995). Melting snow and permafrost may provide a constant cold-water source throughout the summer resulting in cold, wet and boggy areas in direct proximity to drier polar desert vegetation. The shallow active layer in the permafrost exaggerates this effect by hindering drainage. Soils may also vary considerably in depth and form between short distances. Generally, the soils are thin, rarely more than a few centimetres deep, and cover moraine debris, patterned ground or bedrock. In wetter areas, moss may develop into thick carpets or turfs some tens of centimetres deep, efficiently insulating the ground beneath against insolation (Coulson et al., 1993). In nutrient enriched areas, for example under bird cliffs, organic soils of over 10 cm depth may accumulate, illustrating the impact of nutrient flow from the marine environment to the often nutrient limited terrestrial habitat (Odasz, 1994).