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Tundra

Page history last edited by PBworks 14 years, 2 months ago

 

Tundra

 

 

 

 

 

A treeless plain which extends as a band between Boreal Forest (Taiga) and the polar desert.

 

 

The term tundra comes from the Sami word tūndâr (Finnish: tunturi) for sparse woodlands and barrens near the timberline. (http://en.wikipedia.org/wiki/Tundra, 18.09.06) In contrast to this original meaning, the modern use of tundra imply treelessness and shows the diversity, which circulates in the scientific discourse to classify tundra, typically according to vegetation characteristics. (An excellent discussion of tundra can be found in Young 1989, Chapter 8). This definition is based on the reports of CAFF (Conservation of Arctic Flora and Fauna) and AMAP (Arctic Monitoring and Assessment Programme). According to them, tundra is (beside the polar desert) the typical ecozone of the Arctic regions of North America and Eurasia, located between the timberline (or northern treeline) and the polar desert.(see Pict.1) CAFF and AMAP neglected to mention the southern dimension of tundra, also known as alpine tundra, which can be found in any alpine area all over the globe.

Pict. 1 : Tundra Locations:

 

 

 In difference to the ecozone of the boreal forest (taiga), south of the timberline, trees only grow sparsely as low shrubs, because of low temperatures ( -34° C (-30° F) as the average winter temperature and 3-12° C (37-54° F) as the average summer temperature), short growing seasons and very little precipitations.

The typical tundra soil is the permafrost which is a permanent frozen soil. During summer time the top layers of permafrost thaw and offer a very short possibility to tundra plants to grow.

As permafrost disables water to flow off the soil it becomes very wet despite very little precipitations. Therefore peatlands extend to tundra too.

Another specific feature for tundra are little hills with frozen core called pingos.

The dominant tundra vegetation are mosses, lichens, cushion plants and grasses, which build an essentially closed vegetation cover, in comparison with the incomplete plant cover in the polar desert, which is largely bare ground or rock. (CAFF 2001: 131-133; AMAP 1997: 40)

 

A peat moss:

 

Preconditions for Flora

Tundra exists where there is adequate moisture and summer temperatures above the freezing point. The growing season extends to three or four months. Then, the characteristic tundra soil, Permafrost, begins to melt within the so called active layer. The dominant and still frozen deeper layers restrict water drainage and turn the landscape into wetlands with their typical peat soil, a thick layer of organic matter. Plants have to adapt to both actions of soil, freezing and thawing, because Permafrost doesn`t allow deep roots to grow, nor offers nutriens all the year round, thus limiting size and types of plants. Tundra landscape contains a wide range of local habitats, from dwarf willow and birch shrub tundra, over sedge-dominated mires and tussock tundra to dry ridges with heath communities. In the North American usage, these tundra classifications build the so called Low Arctic. Similar geograpic and climate conditions within the circumpolar north supply that the tundra regions in Eurasia and North America share Flora and Fauna species more or less equally (which is unique, compared to other ecozones across the globe). (CAFF 2001: 131-133; AMAP 1997: 40)

 

Fauna

The tundra vegetation is rich enough to support a number of mammals and birds in summer, which are well adapted to the harsh climate in winter. Some mammals, such as marmot and brown bear, hibernate during the long winter season, other animals, like most of the caribou/reindeer and muskox and several birds migrate to other areas. The majority of insects, like mosquitoes and several biting flies, are dormant. Resident non-hibernating species, such as lemmings, ptarmigan and arctic foxes live off fat reserves and little food that is available. (CAFF 2001: 133/138; AMAP 1997: 40-41)

 

Humans

From the earliest times, humans have lived in tundra regions. In recent years, the tundra has been used in increasingly intensive ways, where indigenous living and use (such as hunting and reindeer herding) gets more and more in conflict with the global interest in resources like oil, gas and minerals. Including the impact of climate change, the tundra of the 21th century can be seen as a fragile ecosystem, confronted with several local and global threats. (CAFF 2001: 150/154)

Climate Changes

The climate changes have distinct effects on snow cover and permafrost layer of tundra. Higher temperatures and growing precipitations cause that the spring snow melting starts earlier then usual and also the permafrost is thawing and disappearing very quickly. Higher precipitations and water on the top of the melting ice makes this melting effect even quicker and a specific landscape called Thermokarst is appearing at the place of former permafrost.

Thawing soil of tundra leads to another negative effect. Peatlands are one of the most significant sources of greenhouse gases – CO2 and CH4 in the world. As the ice is melting huge amount of these gases are relieved of the peat and come into the atmosphere. As a result climate changes together with their negative effects on landscape even speed up. Such changes of course translate into lives of local animals, vegetation and humans too. (More information on possible changes scenarios can be found in CAFF, #2 Ecology, page 20)

References:

  • AMAP (Arctic Monitoring and Assessment Programme) 1997. Arctic Pollution Issues: A State of the Arctic Environment Report. Oslo: xii. 188 p.
  • CAFF (Conservation of Arctic Flora and Fauna) 2001. Arctic Flora and Fauna: Status and Conservation. Helsinki: Edita. 272 p.
  • Young, S.B. 1989. Gateway to the Arctic: the northern forest and the timberline. In: S.B. Young. To the Arctic: an introduction to the far northern world. Wiley Science, N.Y., pp. 151-181
  • Introduction to the Circumpolar World, University of the Arctic –BCS 100. Module: Geography and Physical Processes of the Circumpolar World., 8, 18 p.
  • Introduction to the Circumpolar World, University of the Arctic –BCS 100. Module: Environment and Global Climate Change., 12 – 13, 16 p.
  • http://en.wikipedia.org/wiki/Tundra, 18.09.06
  • http://cs.wikipedia.org/wiki/Tundra  25.09.2007
  • http://upload.wikimedia.org/wikipedia/commons/a/a5/800px-Map-Tundra.png
  • http://www.royalalbertamuseum.ca/natural/botany/research/_images/moss.jpg
  • http://www.worldbiomes.com/pics/TundraBiome.jpg
  • http://www.uwsp.edu/geo/faculty/ritter/images/biosphere/vegetation/tundra_ice_mounds_Alaska_DDS21 26.09.2007

 

 

by Dorothee Arenhövel

by Aneta Stillerova

 

 

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