Tundra of North America. Vegetation of arctic deserts and tundra
Polar bioclimatic zone typical for the Arctic and Antarctic regions. The main geographical indicator is the sum of positive temperatures does not exceed 800°C. The polar belt is represented by two zones: polar desert zone And tundra zone .
Polar Desert Zone
In the Northern Hemisphere, the Arctic desert zone includes the northern islands of the Arctic Ocean (Franz Josef Land, Severnaya Zemlya, de Long Islands, northern New Siberian Islands) and the northern tip of the Taimyr Peninsula. The Arctic zone of polar deserts also covers the northern coast of Greenland and some islands of the North American archipelago. Polar deserts are also common in high-latitude regions of Antarctica that are free from ice cover.
The zone of polar Arctic deserts is characterized by exceptionally harsh nature and dry climate. Large areas are occupied by glaciers. The Arctic desert actually spreads in areas free from glacier. Here, with a sharp lack of atmospheric moisture (50-100 mm), frost weathering processes occur vigorously. There is practically no soil cover. Soil fragments: ferruginous films on a rocky surface, several millimeters of organic-mineral mixture under crustacean lichens, sometimes salt efflorescence, carbonate content of surface sediments.
In phytocenoses, there is a weak participation of terrestrial vegetation, which in some places forms a closed cover in depressions of the relief and in shelters protected from the wind. However, on most of the elevated elements of the relief, the vegetation cover is very sparse; the soil surface is often covered with a shell of crushed stone, among which individual low-growing plants, mainly lichens, nestle. There is no need to talk about a stable animal world. There are no reindeer or lemmings on Franz Josef Land. But in the summer, colonies of seabirds nest, forming “bird colonies.” They are formed by puffins, puffins, gulls, auks and other birds. The life of most animals is connected with the ocean: walruses, seals, polar bear, sea otter, etc. In addition, there are lemmings, arctic foxes and some other animals.
In Antarctica, landscapes not covered with ice are called oases . Bioclimatic conditions are more intense than in the Arctic. The vegetation of the oases is very sparse: most of the surface of the rocks and fine-earth sediments is exposed. Various types of crustacean and fruticose lichens and lithophilous mosses settle in places on the rocks; mosses are much more common on fine-earth substrates. In rock cracks and on fine-earth substrates, the flora of green and blue-green algae is abundant.
Penguin settlements and seal rookeries in the coastal and island parts of Antarctica are especially abundantly populated with lichens and mosses. Since penguins and seals feed in the sea, the places of their long-term settlements are enriched with organic matter and mineral chemical elements of marine origin.
There are no land mammals in Antarctica. In addition to various types of seals, the coast is home to more than 10 species of birds: penguins, petrels, skuas, etc.
Thus, in glacial (ice) deserts all the signs of desert weathering and soil formation are clearly and universally expressed: very weak clay formation, the formation of desert tan crusts, widespread calcification of weathering products and soils, salt accumulation with differentiation of salts along the soil profile and within soil-geochemical catenae according to the elements of mesorelief.
Tundra zone
The tundra zone is located south of the Arctic zone. In Eurasia, it extends from the north-west of the Kola Peninsula to the Bering Strait. On the territory of the tundra there are four provinces: Kola, Kaninsko-Pechora, North Siberian and Chukotka-Anadyr.
The North American tundra covers the northern coasts of the continent and the southern part of the North American archipelago.
In the Southern Hemisphere of the Earth, the tundra zone is not observed.
Climate. The southern border of the tundra approximately coincides with the July air isotherm of 12°C. When the average July temperature is below 10-12°C, trees can no longer grow. Summer, in our understanding, if we call summer days with an average daily air temperature above 12°C, as a rule, does not exist in the tundra.
From west to east, the climate of the tundra becomes more continental - there is less precipitation and winters are colder. The Murmansk coast, under the influence of the Gulf Stream, has precipitation of 350-400 mm per year, average temperatures: February -6.2, July-August +9.1, amplitude - 15.3, while in the Lena River delta there is no precipitation only 100 mm per year, the average temperature in February is -42, and in July +5, i.e. amplitude is about 47. Across the Kolyma River, the influence of the Pacific Ocean begins to show itself, and the climate again becomes more maritime: winters are not so frosty, but summers are cooler.
Frosts last from 6 to 8 months in the tundra, in the river delta. Lena even up to 8 1/2 months. However, in winter it is warmer in Murman than on the northern shore of the Caspian Sea: January here is -6, while in Astrakhan -9. In the Siberian continental tundra, frosts reach -50°C in January. Winters inland are colder than on the coast. But summer on the coast is very cool. In summer, the weather in the tundra is unusually changeable: warm days with positive temperatures of 15-20°C and warm nights, alternating with rainy and cold days when the temperature drops to -4°C at night.
Maximum temperatures in the tundra can be high, but not for long. For example, in the north of Taimyr in July the air temperature is often around 20°C. In the southern parts of the Subarctic, air temperatures can remain around 25°C for several days.
But the level of maximum temperatures is not yet the decisive factor in the development of the organic world of the tundra. The main thing is the duration of the warm period. Certain species of animals, mainly birds and mammals, can be active in the Arctic throughout the year. These are: arctic fox, polar bear, tundra partridge, reindeer. Some can even breed in the tundra in winter, as lemmings do. But the main part of the tundra community is active only in the summer (vegetation, microorganisms, invertebrate animals). In summer, all the main abiotic processes in the landscape take place: weathering, erosion, permafrost thawing, etc. Therefore, the duration of the frost-free period, which determines the main features of the tundra landscape and its organic world, is of paramount importance in the life of the tundra.
The total amount of precipitation in the tundra is insignificant, on average 150-250 mm with deviations in smaller and larger directions. In terms of precipitation, the tundra approaches the desert regions of low latitudes. However, the tundra has a lot of water, high soil and air humidity. Large areas are occupied by swamps. The tundra is moistened more than other landscapes on Earth. Only some areas of swampy taiga regions, for example in Western Siberia, can compete with it in terms of the abundance of water. Nowhere is the landscape-forming role of water more pronounced than in the tundra. Underground ice, snow, melt water, fog and prolonged drizzling rains are all powerful ecological and landscape-forming factors in the tundra.
Excess water is associated with low evaporation and transpiration by plants, which everywhere does not exceed 100 mm per year.
The role of snow in the tundra is diverse: participation in the formation of the thermal regime, in particular the reflection of solar radiation as a result of high albedo and the absorption of heat for melting; reduction of weathering and denudation processes; protecting plants and animals from winter cold; snow corrosion; limiting the duration of active life, etc. The role of snow as a heat insulator that protects soil, vegetation and animals from low winter temperatures is widely known. In winter, under the snow, conditions are quite favorable not only for the preservation of animals and plants in a dormant state, but also for the active life of warm-blooded animals - lemmings, other voles, shrews, ermine, weasels.
Snow is the most important factor in the winter life of large herbivorous mammals and birds - reindeer, musk ox, mountain hare, ptarmigan and tundra partridge. They all must somehow get to the vegetation hidden under the snow. In the southern half of the tundra zone, the white hare in winter eats bush branches sticking out from under the snow. There are few hares in the tundra, and this meager and rough food is enough for them. But there is not enough food here for deer and partridge. They cannot dig through a thick layer of very dense snow and migrate south in the fall, to the forest-tundra and taiga, where the snow is loose and where there is more food.
The Arctic is a nival landscape, a world of snow and ice. The duration of snow cover is the main negative factor in the life of most animals and plants. At the same time, snow plays a huge positive role, determining the possibility of existence of many species, protecting them from the winter cold. By protecting biotopes from winter cold, snow promotes the habitat of species of more southern origin in the tundra zone. In those areas where there is little snow, life is poorer, but the process of formation of cold-resistant forms, well adapted to Arctic conditions, intensifies. All this increases the diversity of flora and fauna of the North. And this is the key to the prosperity and sustainability of tundra communities.
Relief. Most of the tundra territory is dominated by flat terrain, sometimes hilly, ridged or ridged, replete with closed thermokarst depressions occupied by lakes and swamps. In some provinces, the relief is typically mountainous (Khibiny, Polar Urals, Byrranga Mountains, Chukotka Mountains, etc.).
Permafrost phenomena - cracking, heaving, solifluction (sliding of soils along a slope), thermokarst - form spotted-small-polygonal and tuberculate (spotted-tubercular) microrelief on tundra watersheds and their slopes, large-polygonal, flat and large-hilly microrelief - on vast swamp plains. From north to south of the tundra zone, abyss and thermokarst microforms (hillocks, mounds) become increasingly important.
Rocks- glacial, marine and alluvial deposits of various mechanical compositions, often very rocky. In the mountains, soil-forming rocks are represented predominantly by coarse-skeletal eluvium of bedrock.
Vegetation. General landscape-forming features of tundra zone phytocenoses can be characterized as follows:
1. A long period of biological permafrost dormancy (about 8 months) and reduced biological activity in summer due to relatively low average daily temperatures and cooling of the soil profile by the cold of permafrost determines the dominance of mosses and lichens, shrubs and shrubs, low stature and sparseness of perennials. Annuals are practically absent.
2. Tundra vegetation develops in conditions of excess moisture, however, moisture often remains inaccessible to plants, as it is present in the form of ice, so many plants have adaptations to reduce evaporation (just like desert plants): small leaves, pubescence, waxy coating and etc.
3. Low amount of synthesized biomass compared to other natural zones of the Earth (4-5 c/ha) and slow rates of its humification and mineralization. In this regard, prerequisites are created for the accumulation of semi-decomposed plant residues on the soil surface (peat removal). Due to excess moisture, peat formation and gleying processes are facilitated by the dominance of anaerobic processes in both the organic and mineral parts of the soil mass.
4. In terms of chemical composition, plant residues are distinguished by exceptionally low ash content. When they decompose, organic acids are formed, causing severe acidification of the soil mass.
Animal world The tundra is characterized by a poor species composition with a high number of animals. Only a few species can withstand harsh winter conditions: lemmings, arctic fox, reindeer, ptarmigan, snowy owl, mountain hare, polar wolf, ermine, long-tailed ground squirrel, weasel, etc. The tundra of North America is also home to the musk ox (musk ox) ) and caribou - an analogue of reindeer. In summer, a mass of migratory birds appear in the tundra, arriving to nest and attracted by the abundance of various food (geese, waders, snipe, swans, etc.).
Permafrost. The most important condition for the formation of the nature of the tundra is permafrost. These are layers of soil or soil with negative temperatures throughout the year. The thickness is 1-400 m. Above the permafrost layer there is a layer of earth that freezes in winter and thaws in summer. It's called active layer. Its size ranges from 30-150 cm depending on the granulometric composition, the presence of a peat layer and geographic latitude. In this limited layer, biological processes occur and soils develop. The wall of the gallery, carved into the permafrost, resembles in appearance gray marble with veins and specks. Sometimes it looks more like a layer cake or a wall made of cast iron. Frozen soil is cemented by lenses of ice. This rock ice is tens of thousands of years old. The entire tundra of Russia, Canada and Alaska, except for the Kola Peninsula, is covered by permafrost. Its origin and maintenance is associated with centuries-long subzero temperatures of the surface atmosphere.
Permafrost is one of the factors that maintains swampiness and water content of tundra landscapes, since it is an aquifer that prevents vertical filtration of water and drainage of the territory. And, of course, permafrost is a constant “refrigerator” that reduces the biological activity of soils and weathering crusts.
Soil cover. The predominant soils of the tundra are of the peat-gley type. The main soil-forming processes are: peat removal of organic matter in the upper layers, above the mineral mass, and gleying of the mineral part of the soil profile. Genetic horizons: A t - peaty organogenic, 10-50 cm thick; A - humus, less than 5 cm and G - gley, up to permafrost thick.
All life in the tundra depends practically on the upper peat horizon.
The gley horizon is abiotic for plants and animals: there is no free oxygen, excess water, acidic reaction of the environment, toxic compounds of reduced iron and manganese.
Due to oversaturation with moisture, the gley horizon often has thixotropic properties associated with the characteristics of mineral colloids. Thixotropy- the phenomenon of transformation of solid soil mass into liquid (gel into sol). This occurs due to mechanical impacts on the soil.
Associated with thixotropy solifluction- sliding of the thixotropic soil layer down the slope under the influence of gravity. The gley soil layer liquefies and turns into a quicksand state.
The formation of spotted tundra. Patches of bare soil (usually 40-50 cm in diameter) are surrounded by a slightly raised ridge of solid moss turf. The ridges of adjacent spots are separated by depressions - hollows filled with peat and loose moss turf. Typically, spotted tundras are confined to high terraces. Their formation is associated with the processes of soil cracking, rupture of moss turf, and extrusion of waterlogged soil onto the surface.
Bare soils in spotted tundras are gradually overgrown. In one area you can find spots that are completely bare and almost completely overgrown with mosses and flowering plants. All this creates a great diversity of ecological conditions, due to which the flora and fauna of the spotted tundra are diverse.
With the onset of autumn, supercooling and freezing of the active soil mass begins from permafrost. The upper horizons are insulated with moss cover. The increase in pressure during freezing leads to the spreading of the thixotropic soil mass of the gley horizon.
Often found in the northern regions of the tundra polygonal tundra, which forms on homogeneous sandy-loamy deposits. Typically polygons consist of four, five, and hexagons. Convex areas of fine-earth material in polygonal tundra are often bordered by rocky debris displaced from the fine-earth material as a result of cryogenic phenomena. This freezing of stones onto the soil surface is also associated with the formation of ice under the stone in the absence of ice above it. Expanding ice, through multi-year cycles, pushes rocks to the surface. Freezing of stones to the surface is also due to the fact that soil freezing begins from permafrost.
A specific element of tundra landscapes is hydrolacolite mounds. Their height varies from 1 m (2-5 m in diameter) to 70 m (150-200 m in diameter). The appearance of the mounds is explained by soil heaving as a result of the formation of an underground ice lens. On the outside, the mounds are covered with a peat layer about 1 m thick. Underneath it is frozen mineral soil, consisting of fine-earth sediments, from one to several meters thick. The mineral soil is underlain by a dome-shaped mass of ice. Lenses of ice are characteristic of permafrost everywhere. Their volume can reach many cubic meters.
Thawing of hydrolacoliths for various reasons, mainly of anthropogenic origin, leads to subsidence of soils and soils, which are called thermokarst. In this case, failures, shifts, and holes are formed, which destroy all ground structures and, first of all, the road network.
Another type of peculiar landscapes is found in the tundra - hummocky swamps. In swampy lowlands, flat-topped peat mounds with a diameter of 1 to 10 m and a height of 0.5 to 1.5 m are developed in rows or groups. They consist of peat formed by mosses growing on their surface. The ridges of hillocks are separated from each other by hollows - marshy, water-logged areas. These swamps are most characteristic of the southern and typical tundra subzones of the western sector of the Subarctic of Eurasia. To the north, and especially in the Arctic tundras, they become less and less numerous.
Solifluction, the formation of patchy and polygonal tundras, hydrolacolites, thermokarst and some other phenomena are united under the general name - cryogenesis. This is a set of processes of physical, chemical and biological transformations occurring in soils due to the influence of negative temperatures, i.e. when they freeze, remain in a frozen state and thaw. There are three stages of cryogenesis: 1) the cooling-freezing stage, which begins when zero temperature appears and ends when the entire soil profile or part of it capable of freezing is completely frozen in the current year; 2) the frozen stage and 3) the heating-thawing stage, which begins with the penetration of positive temperatures into the soil and ends after the complete thawing of the seasonally frozen layer.
Cryogenesis occurs in all frozen soils. The longer, deeper the freezing and lower the temperature, the more noticeable the specific effect of cryogenesis, which is most clearly manifested in the tundra.
Tundra zonation. In the tundra zone, the following four subzones are distinguished: arctic tundra, typical or shrub tundra, southern tundra and forest-tundra subzone.
Arctic tundra subzone. The extreme north is the Arctic tundra subzone, in which not only trees, but also shrubs are absent, or the latter appear only along the rivers. There are absolutely no sphagnum peat bogs in this subzone, the vegetation is sparse and scattered, and there are very few plant species. Areas of patchy and polygonal tundra are widespread. Typical examples of this type are the tundra of northern Yamal, northern Taimyr and the southern New Siberian Islands, Vaygach, Novaya Zemlya, and Wrangel islands. This subzone is located in the region of the present Arctic climate. At its southern border, average July temperatures are 4-5°C, at the northern border - about 1.5°C. Temperatures below 0C and snowfall are possible here throughout the summer. The thickness of the snow cover is insignificant, so winter conditions are especially harsh for animals and plants.
The main feature of the Arctic tundra landscape is the widespread distribution of bare soils. On watersheds, various variants of communities are developed in which patches of bare soil are surrounded by plant turf. They are called spotted, medallion, polygonal spotted, etc. Bare soils occupy approximately 50% of their area. A moss cushion interspersed with twigs of dwarf willows, saxifrage, and grasses is located along a frost-breaking crack around the bare ground. Arctic tundras are very diverse: rocky, gravelly, clayey with a regular medallion structure, with vegetation in the form of clumps, strips, nets, etc. Permafrost phenomena in the Arctic tundra subzone are very diverse and noticeable everywhere.
Weakened weathering and intense cryogenic (permafrost) processes create a very diverse, sharply rugged micro- and nanorelief in the Arctic tundras. There are a lot of rock fragments and rubble everywhere. The surface of the soil is covered with cracks, hollows, and tubercles. The bare soils of the Arctic tundra seem lifeless at first glance, but a rich world of organisms develops on them. The upper layer of soil is inhabited by a mass of unicellular algae and nematodes, enchytraeids, springtails and larger animals - earthworms, larvae of long-legged mosquitoes - that feed on them. On the surface there are many scale lichens that look like mold. Flowering plants are scattered among the rubble - grasses, poppies, siversia, dryads, mytniks, saxifrages, cereals, forget-me-nots, etc. Neither taiga, forest-tundra, nor southern tundra species penetrate into the Arctic tundra. For example, there are no such species as dwarf birch, crowberry, arctic alpine, lingonberry, blueberry, cloudberry, sedge, white partridge, sandpipers - goldfinch and godwit, Middendorff's vole. Many characteristic mass inhabitants of typical tundras, such as the sandpiper and dunlin, are also small or absent here. All this emphasizes the extreme specificity and originality of the climatic regime of this subzone. Living here requires special adaptations that allow it to exist in these harsh conditions.
Subzone of typical tundra. To the south of the Arctic tundra there is a wide subzone of typical, or shrub, tundra, where there are also no trees, but shrubs and, in particular, shrubs are found not only along rivers, but also on interfluve watersheds. Its boundaries approximately correspond to the July isotherms: 8-11 in the south and 4-5 in the north. The area of this subzone is larger than the area of other subzones. In Eurasia, it is well represented in Taimyr, Yamal, Gydan and Yugra Peninsulas. Between Yana and Kolyma and the rest of it - only small, mainly southern, fragments. It is completely absent on the mainland west of the Yugra Peninsula.
This subzone is the embodiment of the type of landscape called tundra. There are not only trees here, but also fairly tall shrubs on the watersheds. The height of vegetation is completely determined by the thickness of the snow cover. Due to snow corrosion, only those plants that are hidden under the snow can survive the winter. Meanwhile, its thickness is small, most often 20-40 cm. Shrub thickets up to 1 m high are developed in lowlands, in stream valleys and along the shores of lakes, where a lot of snow accumulates.
Typical tundras are the kingdom of mosses. A powerful cushion of moss, covering the soil in a continuous layer, usually 5-7 cm thick, in some places up to 12 cm. The moss cover plays a huge and contradictory role in the life of the tundra. It is mosses that ensure complete vegetation cover in watershed areas. They have a great influence on soil temperature and the dynamics of seasonal thawing of soils. On the one hand, the moss cover delays the thawing of permafrost, prevents the soil from warming up and, thus, has a negative effect on the development of organisms. The thicker and denser it is, the colder the soil and the higher the permafrost level. On the other hand, the moss cover prevents the formation of thermokarst and thus has a stabilizing effect on the vegetation. The disastrous consequences of stripping moss turf as a result of, for example, the movement of tracked vehicles are well known.
The moss sward provides habitat for a rich assemblage of invertebrates called the hemiedaphon (semi-soil). It includes a large number of species of springtails, mites, spiders, and insects. At the same time, typical soil forms also live in the moss layer, for example, earthworms, enchytraeids, larvae of long-legged mosquitoes, ground beetles, etc. The life of lemmings depends on mosses. They make complex labyrinths of passages in the turf, and in winter they feed on the fleshy parts of flowering plants hidden in its thickness.
The herbaceous layer consists mainly of various sedges. There are arctic bluegrass, polar poppy, etc. Many creeping shrubs (polar willows, dwarf birch, partridge grass, cassiopeia, lingonberry, crowberry, etc.). Sometimes cotton grass and dicotyledonous herbaceous plants (saxifrage, wintergreen, asteraceae, etc.) are abundant. In some places, the moss turf contains a lot of lichens (leafy, tubular, bushy, crustose, etc.).
In addition to the main communities with continuous moss cover, spotted tundras are also very common in the subzone.
Southern tundra subzone. To the south of the typical tundra, a subzone of the southern tundra stretches in the form of a narrow strip. There are already trees in this subzone, but the forest areas formed by them are located only along the rivers. On watersheds there are only bushes, at most single trees. Sphagnum peat bogs are well developed and are already abundant.
A shrub layer is developed in the main areas of the watersheds. It is formed by birch trees, willows, and alder trees. Under the canopy of shrubs, herbaceous plants (sedges, cotton grass, grasses), and shrubs (blueberries, lingonberries, wild rosemary) are abundant. Below is a continuous moss cover.
In the southern tundra there are single woody plants, most often larches. They are short-growing, have curved thin trunks or a special, dwarf-like shape.
The southern tundras have very diverse vegetation cover. The watersheds are interspersed with thickets of willows, birches (erniks), alders and tundra without shrubs with a continuous moss cover or with patches of bare soil. Various swamps are developed in the depressions - hypnum, sphagnum, flat and with peat mounds. On the southern slopes there is a vegetation cover of cereals, legumes, and various herbs. On the raised edges there are thickets of berry bushes and subshrubs: lingonberries, blueberries, crowberries, arcticus, etc. Near water, near lakes and along the banks of streams, various semi-aquatic plant groups of sedges, horsetails, and grasses are developed.
The main manifestation of the severity of the polar climate in this subzone is the absence of woody vegetation here. Otherwise, the southern tundras are relatively rich communities. The flora and fauna here are very diverse. In addition to typical tundra species, there are many inhabitants of mid-latitudes. For example, in the European and Siberian southern tundras you can find plants everywhere that are common in the middle zone - marsh cinquefoil, common spleen, marsh marigold and even heat-loving common thyme; of birds - warbler, blackbird, common snipe and short-eared owl. The pintail nests on the lakes here, and the widespread housekeeper vole lives along with typical tundra rodents.
Forest-tundra subzone. On the southern edge of the tundra zone, on its border with the area of continuous forests, there is a transitional forest-tundra subzone, where forests and woody vegetation are distributed not only along the rivers, but, in the form of islands, also rise on interfluve watersheds. Sphagnum peat bogs reach enormous development here and form a special type of hilly tundra.
Forest-tundra is a zone of small forests of dwarf birch, small willow, juniper with individual low-growing spruce and larch trees. The harsh conditions of the tundra, poverty of nutrients, and the presence of permafrost at shallow depths complicate the growth and development of woody plants. Trees 200-300 years old are stunted, gnarled, gnarled, and have a diameter of 5-8 cm.
In the southern tundra you can find larch, which has the appearance of a highly branched bush pressed to the ground, rising only 30-50 cm. This is the so-called elfin form, which is formed by many tree species in the Subarctic. Sometimes they form dense, impenetrable thickets. Elf trees are especially characteristic of mountainous regions and the Far Eastern North, where the tundra landscape descends to very low latitudes and covers the habitats of many tree species. So dwarf cedar is widespread everywhere, which is considered either a variety of cedar pine or a special species. In the thickets of elfin trees, favorable conditions are created for wintering animals: there are many voids under the snow lying on top of the thick bushes, and in some places the surface of the litter or soil is open. This makes it easier to move and get food.
Some features of the animal world. Among the animals found in the Subarctic there are a lot of predators: wolf, fox, wolverine, brown bear, weasel, ermine, several species of shrews. This is a characteristic feature of the mammal fauna of the tundra. However, all of the listed species are newcomers from other zones. Among the predatory mammals, there are only two representatives of the truly Arctic fauna - the arctic fox and the polar bear. The Arctic fox is the only native tundra species of predatory animals that is of significant importance in the biocenoses of the Arctic. But among herbivorous rodents and ungulates, the largest number of characteristic tundra endemics is found. These are the ungulate and Ob lemmings, musk ox and reindeer, narrow-skulled vole and Middendorff's vole.
The most impressive are the wild deer. Wild deer has survived mainly in the form of three herds: on the Kola Peninsula under the reserve regime, on Taimyr and in the north of Yakutia. The territory occupied by these herds is small in relation to the total area of the reindeer herding zone.
The largest herd is Taimyr. The places of its main summer migrations and calving are where grazing by domestic animals is clearly unprofitable. Only the wild form is able to successfully use the vast, unproductive pastures of these harsh high-latitude landscapes without causing significant disturbances to the vegetation cover. The mountainous regions of Putorana, where wild deer concentrate for the winter, are also unsuitable for use by reindeer herding farms. Contacts between wild and domestic reindeer in these areas are possible only during relatively short periods. The Taimyr herd, numbering 400 thousand heads, is our national pride. The world's only nesting of white geese on Wrangel Island is also a national pride.
In the tundra there are huge flocks of migratory birds that arrive to nest in the summer: tundra and American swans, partridges, red-breasted goose, white owl, loons, waders, etc.
Agricultural use of the tundra. Agriculture in the tundra zone is impossible on a large scale. Only small-scale consumer gardening is common here; turnips, radishes, onions are sown, and potatoes are planted.
The main occupation in the tundra is reindeer husbandry, based on scarce food supplies. The main winter pasture for deer is lichens - moss moss, which, in the form of lichen tundras, although they occupy a fairly significant area, grow extremely slowly, and, in particular, do not regenerate well after being grazed and trampled. The increase for various subzones is: in the forest-tundra - 4-6 mm over the summer, in the typical tundra - 2-3 mm and in the Arctic - 1-2 mm.
It goes without saying that after they are destroyed by grazing, lichens on pastures regenerate extremely slowly. In various areas, the renewal period, almost equal to the turnover of pastures, is determined on average 15-30 years. A heavily overgrazed reindeer pasture should not be visited again sooner than after 15 years.
Moss moss and other lichens constitute the dominant, almost 9 months of the year, but not the exclusive food of deer. In summer, when the snow melts in the tundra, deer need other food and other types of so-called summer pastures. At this time, they need shrub tundra and river valleys with their tree and shrub vegetation. Since the deer is primarily a tree-eater and not a herbivore, in the presence of shrubs and grasses it always prefers the former. Its food at this time consists mainly of branches, leaves and young shoots of dwarf birch or polar birch and willow trees, and to a lesser extent herbaceous plants: sedge, cotton grass and cereals.
The protein regime of reindeer food is also peculiar. Since lichens are poor in nitrogenous substances, feeding an animal on them for 8-9 months causes all the signs of protein and mineral starvation. To cover the lack of proteins during the summer, deer extremely readily eat various mushrooms, which often appear in abundance in drier areas of the tundra. All autumn, and sometimes the beginning of winter, digging out dried mushrooms from under the snow, deer are busy searching for mushrooms and the failure of such harvests causes a lot of trouble for the reindeer herders.
Thus, reindeer herding is naturally a nomadic economy, because in winter it requires lichen pastures, in spring wet lowland swamps and river valleys, and in autumn dry moss-lichen or mossy tundra.
In the summer of 2014, mysterious craters appeared in the Yamal tundra and they continue to appear in 2015. Several expeditions were sent to study them. Participant of the 2nd expedition, candidate of geological and mineralogical sciences Vladimir Olenchenko spoke about the conclusions that the scientists came to.
At the beginning of 2014, information appeared in the media about an unusual geological formation that was accidentally discovered by helicopter pilots on the Yamal Peninsula near the Bovanenkovskoye field. The formation was a hole in the ground of impressive size and looked like a crater.
In the summer and fall of 2014, several expeditions were sent to the crater formation area. As a result of the 1st expedition, data on the size of the crater and the first results of geophysical studies of the internal structure of the crater were obtained. To clarify the data, the Russian Center for Arctic Development (Salekhard) organized a second comprehensive expedition, which included 8 researchers from Novosibirsk, Tyumen and Moscow.
It lasted 15 days, from August 29 to September 12. Detailed areal geophysical studies of the crater formation area were carried out using electromagnetic and electrical sounding methods.
Now the crater is gradually turning into a lake. Most lakes in Yamal are of thermokarst origin. They are formed as a result of the melting of formation ice and icy rocks. However, recent events have shown that some of the lakes may be traces of gas release craters.
One of the participants of the 2nd expedition, candidate of geological and mineralogical sciences, associate professor at the Institute of Petroleum Geology and Geophysics named after A. A. Trofimuk SB RAS, Vladimir Olenchenko, spoke about the objectives of the expedition, the reasons for the formation of craters and how they can be dangerous.
“The reason for the formation of craters, such craters, is a pneumatic release, that is, a sudden release of gas... The voltage gradually increases and then a pop occurs. It's a bit like popping the cork out of a bottle of champagne. But there are several reasons and they are complex. Among them is global warming, which heats up the frozen mass, which leads both to a change in strength properties, as well as to the destruction of relict gas hydrates, which lie at shallow depths and the geophysical signs of which we have established precisely in the area where this crater is located,” the expert said .
According to him, the task of the 2nd expedition was to examine the changes that had occurred, carry out detailed geophysical research, and also take additional ice samples.
“As we expected, the crater is now filling with ice... For the first time we saw a large deep hole in the ground. Now it looks more like a lake, one of the thousands of lakes in Yamal. The only thing that distinguishes it is its steep banks, but next year they will flow around and it will look like an ordinary lake,” says Vladimir Olenchenko.
At the same time, he assured that such new formations do not pose a danger to populated areas, since it is unlikely that relic gas hydrants exist within their boundaries at depth.
The scientist explained that it is not the crater itself that explodes, but the heaving mounds, since the crater is already a consequence of the explosion. Since Russia does not yet have experience in studying such objects, scientists are now trying to develop criteria for recognizing heaving mounds, so that they can subsequently learn to predict these phenomena.
This ecoregion covers the northern continent of North America. Of course, it has many similarities with the Eurasian tundra: many species of fauna living in North American territories are either relatives of Eurasian species or are distributed in general on both continents. The problems faced by tundra defenders are also largely similar: the development of oil and gas fields leads to catastrophic pollution of the unique natural world.
The Arctic tundra is an area of low, flat and marshy coastal plains covered with lakes filled with melted ice.
LINK IN THE TUNDRA CHAIN
The tundra of North America is part of the natural tundra zone of the Northern Hemisphere.
The American tundra zone occupies the northern part of the North American continent and runs from Northern Alaska along the coast of Hudson Bay to the north of Labrador and Newfoundland. In the east, where the influence of the Labrador Current is felt, the tundra extends to 55-54° N. w.
To the north of the border of distribution of broad-leaved and coniferous trees there are shrub tundras, where such unpretentious plants as creeping heather, dwarf and polar birch, willow, alder and low shrubs predominate.
Since the tundra of North America is located in areas where the waters of the Arctic Ocean extend deep into the land, there is a very confusing picture of the wind regime, with frequent changes in direction and different strengths. Therefore, the geography of distribution of tundra plants is extremely complex. Since this area is in many ways similar to the forest-tundra and taiga, it is not surprising that, quite suddenly for the traveler, the low vegetation bent in all directions in open areas is suddenly replaced by tall trees in river valleys and at the foot of the mountains.
However, as you move north, the predominance of true tundra with mosses, lichen, sedge and cotton grass becomes more and more noticeable, and the woody areas disappear completely.
The peculiarity of the North American tundra is the wide distribution of the Arctic landscape - low, flat and swampy coastal plains. The vegetation here is sparse, with a short growing season and is represented mainly by mosses and lichens. It does not form an even cover and often sows cracks in the soil formed due to severe frosts. Where ice and earth are mixed, ice wedges and heaving mounds are formed, called pingos in Sulfur America.
The climate of the North American tundra is very harsh. The wind here gains extreme strength, it blows snow into the lowlands, where snow drifts form, which persist even in summer. It is precisely because of the lack of snow on the plains that the soil freezes and does not have time to warm up during the short summer. Over a larger area, the climate of the Arctic tundra is more humid and damp than within the boundaries of the subpolar tundra, which extends from American Alaska eastward to Canadian Quebec.
The tundra of northwestern North America - the Alaska Range and the St. Elias Mountains - is distinguished separately. This ecoregion includes the mountains of interior Alaska, which are permanently covered with ice and snow. The rare areas that remain ice-free are rocky, rocky, and alpine tundra.
The occupations of the local population in the tundra of both North America and Eurasia are similar. This includes reindeer herding (the Arctic tundra becomes vast pastures for reindeer in the summer), hunting sea animals (according to quotas from the Ministry of Natural Resources) and fishing. Crafts include bone carving and sewing clothes and shoes from deer skins. There are no large cities in the tundra of North America.
The tundra zone occupies the northern coast of North America. The southern border of the tundra in the west passes near the Arctic Circle, to the east it deepens into more southern latitudes, capturing the coast
Hudson Bay and the northern part of the Labrador Peninsula.
TUNDRA IS UNDER THREAT
The biggest threats facing the North American tundra come from oil and gas pipelines, hydrocarbon development, and global warming.
The fauna of the North American tundra is much richer in species composition than the vegetation. Large mammals are dominated by caribou, brown bear, polar wolf, arctic weasel, polar bear and musk ox, small mammals are fox, arctic fox, lemming and ermine, and birds are white goose, brant, white and tundra partridge. , Alaskan plantain (a bird of the Bunting family) and the white owl, among marine mammals - seal, walrus, narwhal, beluga whale, bowhead whale. There are a lot of fish in the rivers: lake trout, whitefish, grayling.
However, only a very small part of the flora and fauna of the North American tundra is characteristic only of these places. It took specialists a lot of time to figure this out. For example, at the dawn of the study of animals in North America, caribou and Eurasian reindeer were considered different species (today in America there are two subspecies of caribou - tundra and forest), and along with them, American and Eurasian moose. Later studies of the movement of species along the Bering Isthmus, which once connected North America and Eurasia, showed that all these species are related or even identical.
There are many examples of this. The gray-haired marmot is a typical inhabitant of the mountainous American tundra - a brother of the mountain-tundra Siberian black-capped marmot. The long-tailed ground squirrel, an inhabitant of the American tundra, also lives in Siberia. The musk ox could be called a “Native American”, if you did not know that it disappeared from the tundras of Eurasia during the times of primitive people, who mercilessly destroyed the animal’s population.
In general, most American tundra endemics are represented by relatively young species that have recently separated from their closest relatives from the same genus.
A completely unique phenomenon for the tundra of North America is the spread of certain species of birds that arrive here only in the summer months: among such species that fly to the Labrador Peninsula, even several species of tropical hummingbirds and juncos have been spotted (a genus of passerine birds from the bunting family, characteristic only of North America ), savannah bunting (only occasionally found in the tundra of Chukotka), Canada goose (the most common species of game bird here).
The further north you go, the poorer the fauna is and the more its life is connected with the sea: these include auks and gulls nesting on the rocks, and pinnipeds and polar bears. A rare guest from the depths of the southern tundra is the Arctic fox and snow bunting.
The problems associated with tundra pollution are largely similar for different areas due to the nature of the minerals being mined here, their storage and transportation. Despite strict controls and multimillion-dollar fines for leaks from oil pipelines, environmental pollution continues, deer refuse to use special passages, and road trains tear off the top protective layer of tundra soil with their tracks, which takes almost a hundred years to restore.
FUN FACTS
■ The Mackenzie River was discovered and first navigated by Scottish explorer Alexander Mackenzie in 1789. Its original name was Disappointment, which literally means “disappointment” in English. Having given the river such a strange name, Mackenzie expressed his own frustration that it led him not to the Pacific Ocean, but to the Arctic Ocean.
■ The term “pingo” as a typically North American designation for a swelling mound first appeared in 1938. It was borrowed from the Eskimos by the Danish-Canadian botanist Alf Porslig.
■ The easiest way to get deep into the North American tundra is to drive along the Trans-Alaska Pipeline, which runs from Barlow to the Pacific port of Valdez and poses the greatest threat to the ecology of the North American tundra.
■ Tundra Labrador tea plant has red leaves to use chlorophyll and the sun's heat to retain internal heat. None of the tundra animals eat it.
■ The North American tundra receives less annual precipitation than the Mojave Desert.
ATTRACTIONS
■ Natural: Gates of the Arctic National Park and Preserve (Alaska, USA), Kobuk Valley National Park (Alaska, USA), Wapusk and Yukkusaiksalik National Parks (Hudson Bay Coast, Canada), Gross National Park Morne (Newfoundland Island, Canada), Torngat Mountains National Park (Labrador Peninsula, Canada).
Atlas. The whole world is in your hands #255
Spotted tundras are widespread in the Arctic and are found in the goltsy belt of some mountain uplifts. There is no doubt that they are not the same in character and have different origins. There are several hypotheses that one way or another explain the genesis of bare spots in these tundras.
According to V.N. Sukachev, the formation of spots in the Arctic tundra is a consequence of soil freezing in the presence of permanent (permafrost). Excessively moistened loam before freezing is a semi-liquid mass - “quicksand”. This semi-liquid layer expands when freezing and breaks through the frozen surface crust in weak spots (along cracks, etc.), pouring out like a small mud volcano. Thus, due to the outpouring of quicksand on the surface, compressed from below by constant and from above by seasonal permafrost, bare bare spots devoid of vegetation are formed. Then, subject to erosion, they expand and deepen.
L.N. Tyulina develops the hypothesis of V.N. Sukachev in relation to the mountain tundra of the Southern Urals (Mount Iremel). In her opinion, spots in the mountain tundra appear due to the outpouring of a mud volcano onto the surface, tearing apart the plant turf. Then the spots, being washed away, increase in size. The erosion of plant turf is also facilitated by the bulging of stone blocks from the soil when frozen. L.N. Tyulina attaches great importance to permafrost in the formation of characteristic elements of relief and microrelief on Mount Iremel, although she was unable to get to the bottom of the frozen horizon and no evidence was given in favor of its existence.
In the highlands of the non-polar part of the Urals, no one has yet observed permafrost in mineral soils. However, this fact does not bother some researchers, who suggest its presence in the high-mountainous region of the Ural ridge. Not to mention the articles of L. N. Tyulina, one should mention the later published work of N. A. Preobrazhensky, who shaded all the large mountain peaks (Yaman-Tau, Iremel, Zigalga, etc.) on the geomorphological map of the Southern Urals he compiled as an area of permafrost . From the work of N.A. Preobrazhensky, we can conclude that its author actually did not have any data on this issue and refers only to rare cases of the presence of small snow spots on some loaches of the Southern Urals, which in some years do not have time to completely melt during the summer. Even the findings of sporadic permafrost in the foothills of the Northern Urals do not yet prove its presence in the highlands of the Southern Urals.
According to B.N. Gorodkov, “dry spotted tundra arises under the influence of winter winds, blowing snow from open areas and blowing frozen vegetation into fine earth, which is also subject to snow corrosion. Due to frost and drying, the soil surface cracks into polygonal sections; the vegetation cover is preserved only along cracks and grooves between weakly convex, bare spots due to shedding of the edges. In spring and during rain, the spots are saturated with water, puddles sometimes stagnate on them, the loam swells and becomes semi-liquid, which is why on weak slopes the surface of the spots takes on a horizontal position.” In addition to the “dry”, B.N. Gorodkov distinguishes “wet” spotted tundra, in which spots arise as a result of the removal of fine earth to the surface by oozing subsoil flows. At the same time, the loam often slides, tearing the turf and exposing the soil. The formation of bare spots, according to B. N. Gorodkov, can be a consequence of other reasons: erosion by rain and spring waters, soaking, damage by deer hooves.
L.N. Tyulina and B.N. Gorodkov proceed from the fact that spots in the mountain tundra are formed as a result of the destruction or rupture of the turf of the vegetation cover connecting the soil surface. In contrast, V.S. Govorukhin believes that spots appear before vegetation. In the upper reaches of the Khulgi and Syni rivers, high in the mountains, he discovered areas of “anorganic spotted tundra” with characteristic stepped areas of fine earth, but, in the opinion of this researcher, completely devoid of any vegetation. Having traced a number of links in nature in the chain of gradual overgrowing of such areas, V.S. Govorukhin came to the conclusion that first, in the highlands, a stepped microrelief characteristic of spotted tundras is formed. In winter, under the influence of severe frosts, the surface is divided into polygons. The viscous semi-liquid masses of the formed units gradually slide down the slopes. In this case, the heaviest particles slide lower, and the thinner ones settle higher. Then vegetation appears along the edges of the bare spots and in the hollows between them. According to this researcher, the spotted tundras observed in the highlands of the Urals characterize various stages of the advance of vegetation onto lifeless territories that were freed from ice cover in the past. The term “anorganic tundra” proposed by V.S. Govorukhin cannot be considered successful. The concept of “tundra,” along with special environmental conditions, includes a certain complex of plants, and a tundra without plants is as difficult to imagine as a forest without trees. Therefore, if such completely lifeless (“anorganic”) territories in the highlands of the Urals really existed, they could not be called tundra. However, even relatively recently (in a geological sense), the exposed rocky substrate seems lifeless only at first glance. In fact, it is inhabited by microorganisms, crustose lichens, and often also mosses, that is, it is not “anorganic”.
V.B. Sochava, who studied the spotted tundras of the Anadyr region, believes that the formation of spots is the result of partial degradation of the peat layer in those areas where further peat growth has stopped. This causes uneven freezing of the active soil layer (in degraded areas the soil freezes earlier), the occurrence of vertical stresses in the degrading peat layer, upward bulging of mineral soil and the formation of bare spots. Subsequently, the process of peat formation begins again on the bare spots.
Comparing the available literature data, it is easy to see that spotted tundras are very diverse in their structure and origin. The spotted tundras of the high-mountainous region of the Urals differ sharply from the Anadyr spotted tundras described by V. B. Sochava. But even within the Ural range, the mountain spotted tundras are not the same; they fall into several types that have different origins.
As for the spotted mountain tundras we described, the formation of clay-gravelly spots in them is associated primarily with the rupture of the plant turf by semi-liquid quicksand, which lies on a rocky substrate. When the upper soil horizon freezes, the quicksand, experiencing pressure from both sides, breaks through the plant turf. The resulting bare areas are subsequently washed away by rain and melt water. Then they expand and are connected by channels through which excess liquefied clay flows. Further erosion of the bare spots leads to the fact that small clay particles are gradually carried deeper by water, and the clay surface of the spot becomes increasingly lower, and the outer edge of the turf is eroded in width. Thus, in the mountain tundra, round pits (cauldrons) with a rocky bottom are formed. Cracks under the stones serve as the initial paths for washing away fine earth from the surface of the spots into the depths of the placer. The washed away fine-earth material is carried by spring waters into streams flowing from under the placers.
Thus, spot formation in the mountain tundras of the Urals is most correctly explained by the hypothesis of V.N. Sukachev, initially proposed for the flat Arctic tundras, and then developed and supplemented in relation to the natural conditions of the mountain peaks of the Urals. Accepting a number of provisions of L.N. Tyulina, we do not consider it necessary to involve the hypothetical factor of permafrost to explain the causes of spot formation in the mountain tundras of the Urals, especially its southern part. The fine-earth soil layer in the chars of the Urals is underlain by stone blocks and crushed stone, so when the surface layer of soil freezes, it is quite possible for quicksand to flow onto the surface.
The later stages of spot formation (the appearance of cauldrons with a rocky bottom) are most clearly visible in the Southern Urals (especially on Mount Iremel). The process of spot formation in the mountain tundras has gone further here, which is probably due to the fact that the chars of the Southern Urals were freed from glaciation earlier.
Spot formation in the mountain tundras of the Subpolar and Northern Urals increases significantly as a result of excessive grazing by deer, which damage the plant turf with their hooves.
Consequently, spotted tundras do not represent an independent stage in the development of mountain tundra vegetation. The formation of bare spots occurs in moss-shrub, moss-shrub and grass-moss tundras, i.e. in those types of tundras where the fine earth layer is more developed.
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