Tundra

• 1. Defining The Tundra Biome

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  In physical geography, a tundra is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: Arctic, Alpine, and Antarctic. Tundra vegetation is composed of dwarf shrubs, sedges, grasses, mosses, and lichens. Scattered trees grow in some tundra regions. The ecotone or ecological boundary region between the tundra and the forest is known as the tree line or timberline. The tundra soil is rich in nitrogen and phosphorus. The soil also contains large amounts of biomass and decomposed biomass that has been stored as methane and carbon dioxide in the permafrost. This makes the tundra soil a carbon sink. As global warming heats the ecosystem and causes soil thawing, the permafrost carbon cycle accelerates. It releases much of these soil-contained greenhouse gases into the atmosphere. This creates a feedback cycle that contributes to climate change.

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• 2. Etymology And Linguistic Origins

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  The word comes from the Russian ту́ндра spelled tundra. The first use of tundra in English was in 1824, spelled toundra. This spelling possibly indicates borrowing from French. The origin of the Russian word is uncertain. It may be a borrowing of the word тундар spelled tundar. This word belongs to the Sámi language family. It means fell, elevated wasteland, or marshy plain. This usage dates back to the 16th century. Some sources attribute the origin to Finnish instead. The linguistic path remains debated among scholars today.

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• 3. Arctic Ecosystem Dynamics

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  Arctic tundra occurs in the far Northern Hemisphere north of the taiga belt. Permafrost tundra includes vast areas of northern Russia and Canada. The polar tundra is home to several peoples who are mostly nomadic reindeer herders. These include the Nganasan and Nenets in the permafrost area. The Sámi people live in Sápmi. Arctic tundra contains areas of stark landscape and is frozen for much of the year. The soil there is frozen from down to up. This makes it impossible for trees to grow there. Instead, bare and sometimes rocky land can only support certain kinds of Arctic vegetation. Low-growing plants such as moss, heath, and lichen dominate the landscape. There are two main seasons, winter and summer, in the polar tundra areas. During the winter it is very cold, dark, and windy with the average temperature around minus 20 degrees Celsius. Extreme cold temperatures on the tundra generally do not drop as low as those experienced in taiga areas further south. During the summer, temperatures rise somewhat. The top layer of seasonally-frozen soil melts, leaving the ground very soggy. The tundra is covered in marshes, lakes, bogs, and streams during the warm months. Generally daytime temperatures during the summer rise to about 10 degrees Celsius but can often drop to 0 degrees or even below freezing. Arctic tundras are sometimes the subject of habitat conservation programs. In Canada and Russia, many of these areas are protected through a national biodiversity action plan.

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• 4. Antarctic Flora And Fauna

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  Antarctic tundra occurs on Antarctica and on several Antarctic and subantarctic islands. These include South Georgia and the South Sandwich Islands and the Kerguelen Islands. Most of Antarctica is too cold and dry to support vegetation. Most of the continent is covered by ice fields or cold deserts. However, some portions of the continent, particularly the Antarctic Peninsula, have areas of rocky soil that support plant life. The flora presently consists of around 300 to 400 species of lichens. It also includes 100 mosses, 25 liverworts, and around 700 terrestrial and aquatic algae species. These live on the areas of exposed rock and soil around the shore of the continent. Antarctica's two flowering plant species are the Antarctic hair grass Deschampsia antarctica and Antarctic pearlwort Colobanthus quitensis. They are found on the northern and western parts of the Antarctic Peninsula. In contrast with the Arctic tundra, the Antarctic tundra lacks a large mammal fauna. This is mostly due to its physical isolation from the other continents. Sea mammals and seabirds including seals and penguins inhabit areas near the shore. Some small mammals like rabbits and cats have been introduced by humans to some of the subantarctic islands. The Antipodes Subantarctic Islands tundra is an ecoregion that includes the Bounty Islands, Auckland Islands, Antipodes Islands, the Campbell Islands, and Macquarie Island. Species endemic to this ecoregion include the windswept helmet-orchid Corybas dienemus and the grooved helmet-orchid Corybas sulcatus. These are the only subantarctic orchids. The royal penguin and the Antipodean albatross also reside here. There is some ambiguity on whether Magellanic moorland should be considered tundra or not. Edmundo Pisano, a Chilean Phytogeographer, called it tundra since he considered the low temperatures key to restrict plant growth. More recent approaches have since recognized it as a temperate grassland. The flora and fauna of Antarctica and the Antarctic Islands south of 60 degrees south latitude are protected by the Antarctic Treaty System.

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• 5. Alpine High-Altitude Variations

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  Alpine tundra does not contain trees because the climate and soils at high altitude block tree growth. The cold climate of the alpine tundra is caused by the low air temperatures. It is similar to polar climate. Alpine tundra is generally better drained than arctic soils. Alpine tundra transitions to subalpine forests below the tree line. Stunted forests occurring within the forest-tundra ecotone are known as Krummholz. Alpine tundra can be affected by woody plant encroachment. Alpine tundra occurs in mountains worldwide. The flora of the alpine tundra is characterized by plants that grow close to the ground. These include perennial grasses, sedges, forbs, cushion plants, mosses, and lichens. The flora is adapted to the harsh conditions of the alpine environment. Conditions include low temperatures, dryness, ultraviolet radiation, and a short growing season.

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• 6. Climate Change Feedback Loops

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  A severe threat to tundra is climate change which causes permafrost to thaw. The thawing of the permafrost in a given area on human time scales could radically change which species can survive there. It also represents a significant risk to infrastructure built on top of permafrost such as roads and pipelines. In locations where dead vegetation and peat have accumulated, there is a risk of wildfire. An example is the 2007 fire of tundra which burned in 2007 on the north slope of the Brooks Range in Alaska. Such events may both result from and contribute to global warming. Carbon emissions from permafrost thaw contribute to the same warming which facilitates the thaw. This makes it a positive climate change feedback. The warming also intensifies the Arctic water cycle. Increased amounts of warmer rain are another factor which increases permafrost thaw depths. The IPCC Sixth Assessment Report estimates that carbon dioxide and methane released from permafrost could amount to the equivalent of 150 billion tons of carbon dioxide per degree Celsius of warming. For comparison, by 2019, annual anthropogenic emission of carbon dioxide alone stood around 36 billion tons. A 2018 perspectives article discussing tipping points in the climate system activated around 1.5 degrees Celsius of global warming suggested that at this threshold, permafrost thaw would add a further 0.5 degrees to global temperatures by 2100.

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