About 1,702 species of plants live on the Arctic tundra, including

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants t ...

s, short shrubs, herbs,

grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns a ...

es, mosses. These plants are adapted to short, cold growing seasons. They have the ability to withstand extremely cold temperatures in the winter (winter hardiness), and grow and reproduce in summer conditions that are quite limiting. As of 2005, arctic vegetation covered approximately of land. The area of arctic vegetation decreased by approximately from 1980 to 2000, with a corresponding increase in the

boreal forest Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruc ...

. This decrease is linked to the warming of the Arctic due to

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

Adaptations

Arctic plants have a number of adaptations to the compressed growing season and low temperatures: * They initiate growth rapidly in the spring, and flower and set seed much sooner than plants that grow in warmer conditions. * Their peak

metabolic rate Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...

occurs at a much lower temperature than plants from farther south, but only peaks for a short growing season. * Some Arctic plants grow close to the ground as cushion plants, which keep the plants close to the warm soil and shield the tender central growing shoot. * Arctic plants limit their height to be below the snow level. Plants that protrude above the snow are subject to strong winds, blowing snow, and being eaten by caribou, muskox, or ptarmigan. * Arctic plants can survive very low temperatures because of high concentration of soluble carbohydrates, such as

raffinose Raffinose is a trisaccharide composed of galactose, glucose, and fructose. It can be found in beans, cabbage, brussels sprouts, broccoli, asparagus, other vegetables, and whole grains. Raffinose can be hydrolyzed to D-galactose and sucrose ...

. * Reproduction by vegetative propagation is common. Mosses and lichens are common in the Arctic. These organisms have the ability to stop growth at any time and resume it promptly when conditions improve. They can even survive being covered by snow and ice for over a year.

Effect of climate

Arctic vegetation is largely controlled by the mean temperature in July, the warmest month. Arctic vegetation occurs in the tundra climate, where trees cannot grow. Tundra climate has two boundaries: the snow line, where permanent year-round snow and ice are on the ground, and the

tree line The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually cold temperatures, extreme snow ...

, where the climate becomes warm enough for trees to grow. The snow line occurs when all monthly mean temperatures are below . The formula used for the tree line has changed over time: under the

Köppen climate classification The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, nota ...

, the treeline occurs when the July temperature is . Otto Nordenskjöld proposed that the warmest month must be at 9-0.1 T in Celsius, where T is the temperature of the coldest month. In 1947, Holdridge proposed computing the average of all months whose mean temperature are above zero: the treeline would occur when that average is . Rohkunborri-Cassiope-Tetragona

The July mean temperature is close to 0°C in the coldest areas where Arctic vegetation can grow. At these temperatures, plants are at their metabolic limits, and small differences in the total amount of summer warmth make large difference in the amount of energy available for maintenance, growth and reproduction. As one goes for north to south, the size, horizontal cover, abundance, productivity and variety of plants increases: * Below , woody plants are absent. * From , woody plants grow as prostrate dwarf shrubs. Examples include '' Dryas'' sp., and '' Salix arctica''. * From , woody plants increase in height to . Examples include '' Arctous alpina'' and '' Cassiope tetragona''. * From , woody plants become erect dwarf shrubs, up to tall. Examples include '' Betula nana'', ''

Ledum decumbens ''Rhododendron tomentosum'' (syn. ''Ledum palustre''), commonly known as marsh Labrador tea, northern Labrador tea or wild rosemary, is a flowering plant in the subsection ''Ledum'' of the large genus ''Rhododendron'' in the family Ericaceae. D ...

'', ''

Vaccinium uliginosum ''Vaccinium uliginosum'' (bog bilberry, bog blueberry, northern bilberry or western blueberry) is a Eurasian and North American flowering plant in the genus '' Vaccinium'' within the heath family. Distribution ''Vaccinium uliginosum'' is nativ ...

''. * From , woody plants become low shrubs, up to tall. Examples include ''

Betula glandulosa ''Betula glandulosa'', the American dwarf birch, also known as resin birch or shrub birch, is a species of birch native to North America. Description American dwarf birch is a multi-stemmed shrub typically growing to tall, often forming dense ...

'' and '' Salix glauca''. * The treeline occurs when the July mean temperature is approximately . Because small changes in temperature affect survival, growth, and reproduction of arctic plants, the effects of local

microclimate A microclimate (or micro-climate) is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference but sometimes with a substantial one. The term may refer to areas as small as a few squ ...

s can be significant. Plants low to the ground can create their own microclimate: when the air temperature away from the ground is , the temperature of dark moss can be . Even if the local microclimate cannot maintain temperatures above , some arctic plants and flowers, such as '' Chamaenerion latifolium'', can survive a frost with no damage. Some plants start to grow under up to of snow cover.

References

{{DEFAULTSORT:Arctic Vegetation Flora of the Arctic