Arctic terrestrial ecosystem

text by Malu Avila & Stephen Coulson

In the Arctic, land areas have predominantly treeless permafrost and large areas with tundra (more about different habitats here).

Across the Arctic, the 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 been recently 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. Vascular plant cover is often limited, for example restricted to less than 15% in both Svalbard and Franz Josef Land (Aleksandrova, 1983; Jónsdóttir, 2005; Cooper, 2011). Along the west coast of Svalbard and the southern areas of Novaya Zemlya areas of dwarf shrub tundra or heath characterized by species such as Dryas octopetala and Cassiope tetragona may develop. Bare soil in all three archipelagoes often possesses a “biological crust” of cyanobacteria, bacteria, algae and lichen.

Vascular plant diversity in Franz Josef Land totals 74 species (Tkach et al., 2008), 173 in Svalbard (Elven and Elvebakk, 1996) 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 597 recorded species (Elvebakk and Hertel, 1996). 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 face temperatures no lower than -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 dryer 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 over short distances. Generally, the soils are thin, rarely more than a few centimeters thick, and overlie moraine debris, patterned ground or bedrock. In wetter areas, moss may develop into thick carpets or turfs some tens of centimeters 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 also accumulate illustrating the impact of nutrient flow from the marine environment to the often nutrient limited terrestrial habitat (Odasz, 1994).