POLAR ECOSYSTEM

complex of living organisms in polar regions such as polar barrens and tundra. Southern limit of Arctic tundra and approximate line of demarcation between Low and High Arctic. Polar barrens and tundra are found at high latitudes on land surfaces not covered by perpetual ice and snow. These areas lying beyond the tree line comprise more than 10 percent of the Earth's land surface. Most are in the Arctic and subarctic, as little land area in the Antarctic is ever free of snow and ice (seefigure). The Arctic can be divided into the Low Arctic and High Arctic, according to various environmental and biological characteristics. Tundras are most common in the Low Arctic, and polar barrens are dominant in the High Arctic. The Russian term tundra is derived from the Finnish word tunturi, meaning treeless heights. Tundra is now used in a general sense to describe any cold-climate landscape having vegetation without trees, which includes both mountainous areas (alpine tundra) and areas in the Arctic, subarctic, and Antarctic. In a more restricted sense, tundra denotes a special type of vegetation association. The tundra zones of the polar regions are distinct from the polar barrens, which are sparsely vegetated. (For more information on Arctic and Antarctic lands see the articles Arctic and Antarctica.) Additional reading Peter J. Marchand, Life in the Cold: An Introduction to Winter Ecology, 2nd ed. (1991), describes the adaptations of plants and animals to the physical constraints of temperature, snow, and wind in high-latitude environments. Sanford Moss, Natural History of the Antarctic Peninsula (1988), an illustrated text, provides general descriptions of the life-forms of the Antarctic Peninsula in relation to the climate and adjacent marine system. G.E. Fogg, A History of Antarctic Science (1992), comprehensively reviews research done in Antarctica. Jack D. Ives and Roger G. Barry (eds.), Arctic and Alpine Environments (1974), looks at these ecosystems, their physical components, adaptations of life-forms present (including humans and their prehistorical and historical presence), and the impact of technology on these environments. Antarctic Bibliography (annual); and Arctic Bibliography, 16 vol. (195375), are useful reference works for publications on these regions.E. Imre Friedmann and Roseli Ocampo, Endolithic Blue-Green Algae in the Dry Valleys: Primary Producers in the Antarctic Desert Ecosystem, Science, 193(4259):12471249 (Sept. 24, 1976), details the unique forms of life found within rocks in Antarctica. Larry L. Tieszen (ed.), Vegetation and Production Ecology of an Alaskan Arctic Tundra (1978), focuses on the vegetation and its primary production in a wet tundra ecosystem. George O. Batzli (ed.), Patterns of Vegetation and Herbivory in Arctic Tundra (1980), describes the vegetation as well as the role of herbivores in the ecology of the tundra.George A. Llano (ed.), Adaptations Within Antarctic Ecosystems (1977), symposium proceedings, looks at the adaptation of organisms in both marine and terrestrial ecosystems. N. Leader-Williams, Reindeer on South Georgia: The Ecology of an Introduced Population (1988), discusses the effects of introducing mammals to the southern islands. L.C. Bliss (ed.), Truelove Lowland, Devon Island, Canada: A High Arctic Ecosystem (1977), focuses on ecosystem components. Yu.I. Chernov (IU.I. Chernov), The Living Tundra (1985; originally published in Russian, 1980), is a classic description of tundra landscapes, ecosystems, and plant and animal components. Jerry Brown et al. (eds.), An Arctic Ecosystem: The Coastal Tundra at Barrow, Alaska (1980), compiles research findings on ecosystem components of the Arctic tundra. L.C. Bliss, O.W. Heal, and J.J. Moore (eds.), Tundra Ecosystems: A Comparative Analysis (1981), is an excellent comprehensive synthesis on circumpolar and tundra systems. F. Stuart Chapin III et al. (eds.), Arctic Ecosystems in a Changing Climate: An Ecophysiological Perspective (1992), describes the physiological processes of plants and animals in this region and also discusses the consequences of global climate change on these processes. David R. Klein