Dry Tundra

Dry tundra is the common term for a wide range of tundra habitats from rather flat areas with very stony soil, and low, usually sparse vascular plants to rocky habitats on exposed alpine summits and ridges, characterized by low mat and cushion plants and an abundance of bare rocks. Widely used synonyms of dry tundra are ridge tundra, fell-field from the Danish field-mark or rock desert, and blockfield or the German term Felsenmeer (sea of rocks). The common environmental features of dry tundra are exposure to strong wind and desiccation, usually convex land-forms, and little or no snow cover during normal winter conditions in contrast to neighboring habitats.

Dry tundra is a common habitat throughout much of the High Arctic, especially in the Canadian Arctic Archipelago. It is also important in the Low Arctic mountains of Scandinavia, Greenland, the northern and polar Urals, Taymyr, and the amphi-Beringian area. Outside of the Arctic, dry tundra is widely distributed within the alpine belt of the boreal zone. It is notable that the term "tundra" originates from the Saami word tunturi, which refers to the treeless mountain landscapes of Lapland dominated by dry tundra and dwarf-shrub heaths. Species of the genus Dryas dominate these environments throughout the Low Arctic and south of the High Arctic and are characteristic of dry tundra. Along with Dryas species, other prostrate mat shrubs like Loiseleuria decumbens, Arctostaphylos alpina, and Diapensia lapponica, some prostrate willows, and numerous cushion plants of genera such as Potentilla, Oxytropis, and Artemisia are common here. Dense pubescence (covering of downy, short hair) is characteristic for many plants, and helps retain water and heat emitted by the plant. Most dry tundra communities are discontinuous within diverse cryoturba-tion-driven lateral structures. The community structure also strongly correlates with snow accumulation. Continuous dry tundra vegetation of the Low Arctic is restricted to depressions and slope bottoms with about 20-25 cm snow accumulation. Prostrate mat shrubs dominate here with an admixture of low dwarf shrubs from genera Betula, Salix, Vaccinium, Empetrum, Ledum, and Cassiope; fruticose and foliose lichens are frequent. Prostrate mat shrubs with an admixture of cushions and crustaceous lichens and with about 20% of gravely bare ground are typical of habitats with less than 20 cm winter snow. In the most extremely exposed habitats with no or fragmentary winter snow, plants survive only in microdepressions and frost-boil cracks forming a netlike cover of Dryas, cushion plants, and crustaceous lichens amid mainly gravely bare ground. A similar reduction of plant cover in dry habitats is observed in the northward direction. Dry High Arctic environments are characterized by scattered Dryas-cushion herb-crustaceous lichen tundra, further north by extremely poor rocky or gravely desert with sparse cushions and crustaceous lichens, and by bare ground and rock in the polar desert.

Due to the thin snow cover, dry tundra is an important winter pasture for domesticated and wild reindeer, muskox, and snow sheep. Dry tundra diversity both in community structure and species composition is especially high in the northeastern Asia. There are many xeric (adapted to an extremely dry habitat) species populating dry tundra, mostly of densely pubescent cushion growth form from genera such as Potentilla, Artemisia, Oxytropis, Draba, and Senecio. Most of these genera probably originated from continental northern Asia and Beringia, when the wide land bridge linked Asia with North America intermittently for nearly 30 million years in the Tertiary, and survived mainly as relicts within Asian and Beringian refugia with no full glaciations during the Pleistocene. Fossils of the genus Dryas are known from high latitudes since the late Neogene (about 5 million years ago).

Volodya Razzhivin

See also Dwarf-Shrub Heaths; Fell-Fields; Mesic Tundra

Further Reading

Aleksandrova, V.D., The Arctic and Antarctic: Their Division into Geobotanical Areas, Cambridge: Cambridge University Press, 1980

Chapin III, F.S. & Ch. Körner (editors), "Arctic and alpine biodiversity: patterns, causes, and ecosystem consequences. Ecological Studies, 113, (1995): 320pp Chernov, Yu.I. & N.V. Matveyeva, "Arctic Ecosystems in Russia." In Polar and Alpine Tundra. Ecosystems of the World 3, edited by F.E. Wielgolaski, Amsterdam: Elsevier, 1997, pp. 361-507 Daniels, F.J.A., "Vegetation of the Angmagssalik District, Southeast Greenland, IV. Shrub, dwarf shrub and terricolous lichens." Meddelelser om Grönland Bioscience, 10 (1982): 1-78

Elvebakk, A., "Tundra diversity and ecological characteristics of Svalbard." In Polar and Alpine Tundra, edited by F.E. Wielgolaski, Amsterdam: Elsevier, 1997, pp. 347-359

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