The cold Arctic climate averages only 5° C (41° F) at the height of Summer, and 32° C (26° F) in midwinter. Precipitation over much of the Arctic is actually very low…usually less than 25 centimeters (10 inches) of water equivalence each year. About 30 centimeters (12 inches) of snow equals 2.5 centimeters (one inch) of water. Two thirds of the precipitation comes as Summer rains and this is augmented by meltwater from winter snows. By definition, then, most of the Arctic qualifies as a desert. The ground, however, is in a perpetual deep freeze, or permafrost, just 1560 centimeters (624 inches) below the surface. So, water does manage to accumulate as it is prevented from sinking deep into the ground by the permafrost just below the surface, hence the extensive wetlands and an abundance of moisture available for plants. The depth of the permafrost varies with different local conditions, but becomes gradually deeper (farther from the surface) as one travels south, until it disappears altogether. It correlates fairly closely with the treeline, because it helps to restrict tree growth by keeping the surface layer too waterlogged for large plants. If it were not for the permafrost, what little moisture the Arctic receives in the Summer would soak away deep in the soil, out of reach from most plant life. As a result, the plant life is amazingly rich and extensive during the short growing season. Most Arctic plant or plant-like species are simple lichens and mosses, but more complex vascular plants such as ferns, grasses, sedges, herbs, flowering plants also abound and dwarf shrubs
As one would expect, plants in the Arctic have had to adapt to extremely harsh conditions that normally cripple or kill most plants, including extremely low temperatures, continuous night during the long Winter (as well as nearly continuous daylight during the Summer), acidic and infertile soils (here is also a major lack of nutrients), alternating freeze and thaw conditions, long periods of snow cover, permafrost, and strong, desiccating winds. The short growing season lasts only a few months, but once the snow cover melts, plants seem to explode into new leaf growth and colorful blooms. ArcticFew plants outside of the Arctic can survive these conditions. plant life is inactive for as much as nine months out of the year while the plants go dormant under a blanket of snow, although some plants have the ability to grow even under a layer of snow and can photosynthesize in extremely cold temperatures.
Arctic plants tend to be surprisingly small and rugged, and grow very close to the ground. Many of them grow closely clumped together (especially those known as cushion plants). These are two important adaptations that help protect plants from both cold temperatures and the strong winds. The all-pervasive permafrost precludes plants developing large, deep root systems, which undoubtedly contributes to the small, stunted stature of the Arctic plants. Even the leaves are especially small, which helps the plants better retain moisture. In addition to the typical lichens, mosses, ferns, and flowering plants, numerous tree groups are represented here, including evergreens, willows, birches, etc., but they are all dwarf species and look kind of like naturally formed bonsai trees.
Almost all high Arctic plants are perennials (that is, they do not die in the winter), because the short Summer doesn’t allow enough time for most of them to go through their entire life cycle in one growing season. The flora is greatly influenced by the short growing season, in some areas lasting only about seven weeks, so flowering plants make efficient use of the long hours of Summer sunlight to produce flowers very quickly…much faster than temperate and tropical species. A combination of inherent problems, such as slow microbial action (cold soil temperatures retard metabolism), poor soil drainage, and poor aeration, prevent the quick breakdown of organic matter. This allows the accumulation of peat, which results in acidic soil, with a low level of nitrogen. Poor soils, together with cold temperatures, cause plants to mature slowly. These problems are offset somewhat by the long daylight hours which allow almost continuous photosynthetic activity during the growing season. Many plants have specially designed concaved flowers that face toward the Sun, helping them stay warmer than the surrounding air. In addition, most Arctic plants are dark-colored (many are reddish), which probably allows the plants to absorb more solar radiation for extra warmth. Many flowering plants also have fuzzy coverings on their stems, leaves, and flower buds in order to provide extra protection from the drying and cooling effects of the wind. Some even have woolly coverings on their seeds. Warmer temperatures are important to the plants, because a higher temperature allows a higher rate of metabolism, thereby faster growth.
The Arctic ecosystem is often referred to simply as Tundra, but scientists often classify the into separate biogeographic zones. One method divides it into the High Arctic Zone (including the polar desert and sedgemoss tundra), which is made up of scattered plant communities that are restricted to only the most favorable regions, and the Low Arctic Zone (including the cottongrass/shrub tundra system), which is basically a continuous carpet of vegetation. Sometimes a third zone is included with this system the Middle Arctic Zone.
The High Arctic Zone is dominated by sedges and grasses, but also contains lichens, mosses, ferns, numerous flowering plants (lilies, daisies, saxifarages, buttercups, legumes, pinks, roses, and others), shrubs, and dwarfed, scrubby willows and birches. It is controlled by an assortment of climatic and biological influences, such as temperature, precipitation, winds, erosion, soil qualities, microbes, etc., covered in large part by a surface layer of peat. Except for protected areas along rivers and lakes in the Low Arctic, the tundra vegetation usually grows no higher than 35 centimeters (14 inches). It covers almost the entirety of Greenland, Svalbard, much of the Canadian Archipelago (including almost all of Baffin, Ellesmere, Devon, and Somerset islands, and significant portions of both Melville and Victoria islands), as well as several sections of various Canadian peninsulas which project into the archipelago region, as well as many islands off the coast of Siberia. There is, in general, an inverse relationship between floral diversity in the Arctic and latitude. In other words, as one moves northward, the species diversity of plants decreases. Also, isolated areas, such as remote islands or interior regions cut off by mountains, ice fields, etc., tend to have lower species diversity than non-isolated areas of similar latitude. It has been estimated that the Arctic contains about 1,000 species of flowering plants. About 600 of these species are endemic, and about 200 are circumpolar. In Svalbard, however, only six to seven percent of the land-area is covered by vegetation and within this, only 176 species of plants have been identified.
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