In the vastness of the tundra. Polar bioclimatic belt Cracks in the tundra of Canada in summer

The word "tundra" in Finnish means treeless bare hill. And in fact, it occupies vast territories of the Northern Hemisphere in the subarctic latitudes, where mossy and lichen vegetation prevails in a rather harsh climate. The spaces are distinguished by the absence of tall trees, although the tundra and forest-tundra border on luxurious taiga forests. Only perennial grasses and small shrubs cover the cold ground during periods of short summer.

Due to the high and low volatility, there is an effect of waterlogging of the lands in these harsh places. But what prevents water from seeping into tundra soil?

Climate

The tundra zone stretches in a narrow strip across the north of Eurasia, and moreover, larger areas are located in Russia and Canada. and subantarctic. With strong winds and air temperatures in winter down to -30°, and in summer barely reaching +5 + 10° Celsius, even here they do not grow.

A long snowy winter and only 2-3 relatively warm months a year contribute to the fact that the tundra suffers from an excess of moisture. The low temperature regime does not allow it to evaporate, swamping vast areas. Winter for the tundra is a polar night, and in summer the sun shines almost all day long. Spring and autumn, with the manifestation of all their signs, fit into a single month - May and September, respectively. They are characterized by the rapid disappearance of low snow cover and the same rapid return in early October.

Characteristic features of tundra soil

The features of the harsh subarctic and subantarctic climate, as well as the soil, are what prevent water from seeping into the tundra soil. Thaws are only enough to thaw only the upper layers of the earth to an insignificant depth. turns the tundra soil into an icy block, and this state does not change.

In winter, a lot of snow falls in these parts, but it falls on the desert plains in a thin layer, since strong winds blow away most of it.

Gley and stony soils have a characteristic rusty and gray color. The layers of the soil cover of the tundra either thaw or freeze, gradually mixing with each other. Thus, humus, humus and peat sink to a meter depth. With an abundance of moisture, clay and loamy soils become waterlogged. On flat plains, the earth literally bends under the weight of a person, trying to suck him into a thick quagmire. However, the peat layer does not exceed 50 centimeters due to the poor cover of herbaceous plants and moss. On sandy dehydrated areas, the soil layer is podzols and podburs.

What prevents water from seeping into tundra soil?

So far, the issue has not been fully resolved. What's blocking the water? It seeps into moisture only in summer, through a peat cushion and cracks formed by severe frosts. But since during the winter the earth freezes to a depth of one and a half kilometers and does not have time to thaw in a short warm period, the boundary layer, literally turned into a stone-ice crust, becomes an insurmountable barrier for water.

Thus, the answer to the question of what prevents water from seeping into the tundra soil is simple and logical: the permafrost does not allow moisture to seep deep, and the water does not warm up to such an extent as to melt the frozen ground. This is how the boundless and unheated tundra lives for thousands of years.

Spotted tundras are widespread in the Arctic and are found in the bald belt of some mountain uplifts. Undoubtedly, they are not the same in character and have different origins. There are several hypotheses that somehow explain the genesis of bare patches 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 upon freezing and breaks through the frozen surface crust in weak places (along cracks, etc.), pouring out like a small mud volcano. So, due to the outpouring of quicksand, compressed from below by permanent, and from above by seasonal permafrost, bare, bare spots are formed, devoid of vegetation. Then they, subjected to erosion, 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 as a result of an outpouring of a mud volcano on the surface, tearing the vegetative sod. Then the spots, subjected to erosion, increase in size. The erosion of the plant sod is also favored by the protrusion of stone blocks from the soil during freezing. L. N. Tyulina attaches great importance to permafrost in the formation of characteristic elements of relief and microrelief on Mount Iremel, although she failed to get to the frozen horizon and no evidence in favor of its existence was given.

In the highlands of the non-polar part of the Urals, no one has yet observed permafrost in mineral soils. Nevertheless, this fact does not confuse some researchers who assume its presence in the high-mountainous region of the Ural Range. 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 compiled by him as an area of ​​permafrost . From the work of N. A. Preobrazhensky, we can conclude that the 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 bald mountains of the Southern Urals, which in some years do not have time to completely melt over 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 places and blowing frozen vegetation into the fine earth, which is also subjected to snow corrosion. From frost and drying, the surface of the soil cracks into polygonal fragments, the vegetation cover is preserved only along cracks and grooves between bare spots that are slightly convex 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 the surface of the spots takes on a horizontal position on weak slopes. In addition to the "dry", B. N. Gorodkov, we distinguish "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 slips, tearing the turf and exposing the soil. The formation of bare spots, according to B.N. Gorodkov, may be the result of other reasons: erosion by rains and spring waters, wetting, 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 that binds the soil surface. In contrast, V. S. Govorukhin believes that spots appear before vegetation. In the upper reaches of the Khulga and Synya rivers, high in the mountains, he discovered areas of "anorganic spotted tundra" with characteristic stepped areas of fine earth, but, according to this researcher, completely devoid of any kind of vegetation. Having traced in nature a number of links in the chain of gradual overgrowth of such areas, V. S. Govorukhin came to the conclusion that at first a stepped microrelief, characteristic of spotted tundra, is formed in the highlands. In winter, under the influence of severe frosts, the surface is divided into polygons. The viscous semi-liquid masses of the formed particles gradually slide down the slopes. In this case, the heaviest particles slide down, while the thinner particles settle higher. Then vegetation appears along the margins of the bare spots and in the hollows between them. According to this researcher, spotted tundras observed in the high mountains of the Urals characterize various stages of the advance of vegetation on lifeless territories that were freed from the 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 just as hard 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 the geological sense), the exposed rocky substrate seems lifeless only at first glance. In fact, it is inhabited by microorganisms, scale lichens, and often also by mosses, that is, it is not “anorganic”.

V. B. Sochava, who studied the spotted tundras of the Anadyr Territory, believes that the formation of spots is the result of partial degradation of the peat layer in those areas where further growth of peat has ceased. 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, protrusion of the mineral soil upwards and the formation of bare spots. Subsequently, the process of peat formation begins again on 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 Mountain Range, the mountain spotted tundras are not the same, they fall into several types of different origin.

As for the patchy mountain tundras described by us, the formation of clay-rubbly spots in them is associated mainly with the rupture of the plant sod by semi-liquid quicksand, which lies on a stony substrate. At the moment of freezing of the upper soil horizon, the quicksand, experiencing pressure from both sides, breaks through the vegetative sod. The resulting bare areas are further eroded by rain and melt water. Then they expand and connect with tubules, through which excess liquefied clay flows. Further erosion of bare spots leads to the fact that small clay particles are gradually carried away by water in depth, and the clay surface of the spot decreases more and more, and the outer edge of the turf is eroded in width. So, in the mountain tundra, rounded pits (boilers) with a rocky bottom are formed. Cracks under the stones serve as the initial ways of washing off the fine earth from the surface of the spots into the depth of the placer. The washed-out 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. Accepting a number of provisions of L. N. Tyulina, we do not consider it necessary to invoke the hypothetical factor of permafrost to explain the causes of spot formation in the mountain tundra of the Urals, especially its southern part. The fine-earth soil layer on the bald mountains of the Urals is underlain by stone blocks and rubble, therefore, when the surface layer of the soil freezes, it is quite possible for quicksand to pour out onto the surface.

The most distinctly late stages of spot formation (appearance of cauldrons with a rocky bottom) can be traced in the Southern Urals (especially on Mount Iremel). The process of spot formation in the mountain tundra has gone further here, which is probably due to the fact that the bald mountains of the Southern Urals were freed from glaciation earlier.

Spot formation in the mountain tundras of the Subpolar and Northern Urals is greatly enhanced as a result of the immoderate grazing of deer, damaging 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 tundra where the layer of fine earth is more developed.

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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. Member of the 2nd expedition, candidate of geological and mineralogical sciences Vladimir Olenchenko spoke about the conclusions reached by scientists.

At the beginning of 2014, information appeared in the media about an unusual geological formation 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 autumn of 2014, several expeditions were sent to the area where the crater formed. As a result of the 1st expedition, data were obtained on the dimensions of the crater and the first results of geophysical studies of the internal structure of the crater. To clarify the data, the Russian Center for the Development of the Arctic (Salekhard) organized the second comprehensive expedition, which was attended by 8 researchers from Novosibirsk, Tyumen and Moscow.

It lasted 15 days, from August 29 to September 12. Detailed areal geophysical studies of the territory of the crater formation were carried out using electromagnetic and electrical sounding methods.

Now the crater is gradually turning into a lake. Most of the lakes in Yamal are of thermokarst origin. They are formed as a result of thawing of massive ice and icy rocks. However, recent events have shown that some of the lakes may be traces of gas emission funnels.

One of the participants of the 2nd expedition, Candidate of Geological and Mineralogical Sciences, Associate Professor of the A. A. Trofimuk Institute of Petroleum Geology and Geophysics of the Siberian Branch of the Russian Academy of Sciences Vladimir Olenchenko spoke about the tasks of the expedition, the reasons for the formation of craters and how they can be dangerous.

“The reason for the formation of craters, such funnels, is a pneumatic release, that is, a sudden release of gas ... The tension gradually increases and then there is a bang. It's a bit like popping a cork out of a champagne bottle. But there are several reasons and they are complex. Among them is global warming, which warms up the frozen strata, which leads both to a change in strength properties, as well as to the destruction of relict gas hydrates, which occur at a shallow depth and whose geophysical features we have established just 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 taken place, to make detailed geophysical studies, and also to take additional ice samples.

“As we expected, now the crater is 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 melt, flow around and it will already look like an ordinary lake,” says Vladimir Olenchenko.

At the same time, he assured that such neoplasms do not pose a danger to settlements, since it is unlikely that relic gas hydrants are within them at a depth.

The scientist explained that it is not the crater itself that explodes, but heaving mounds, since the crater is already a consequence of the explosion. Since there is no experience in studying such objects in Russia yet, scientists are now trying to develop criteria for recognizing heaving mounds in order to later learn how to predict these phenomena.

Polar bioclimatic belt characteristic of the regions of the Arctic and Antarctic. The main geographical indicator - the sum of positive temperatures does not exceed 800С. 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, the de Long Islands, the north of the New Siberian Islands) and the northern tip of the Taimyr Peninsula. The Arctic zone of polar deserts also covers the northern coast of Greenland, some islands of the North American archipelago. Polar deserts are also common in the high-latitude regions of Antarctica, which are free from ice cover.

The zone of the polar arctic deserts is distinguished by the exceptional severity of nature and the dryness of the climate. Large areas are occupied by glaciers. In the spaces free from the glacier, the Arctic desert actually spreads. Here, with a sharp lack of atmospheric moisture (50-100 mm), the processes of frosty weathering proceed vigorously. The soil cover is practically absent. Soil fragments: ferruginous films on a rocky surface, several millimeters of organic-mineral mixture under scale lichens, sometimes salt efflorescence, carbonate content of surface sediments.

In phytocenoses, a weak participation of terrestrial vegetation is observed, which in places forms a closed cover in relief depressions 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, huddle. There is no need to talk about a stable animal world. There are no reindeer or lemmings in 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 bears, sea otters, etc. In addition, there are lemmings, arctic foxes and some other animals.

In Antarctica, non-ice-covered landscapes 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 rocks and fine-earth sediments is exposed. Various types of scale and fruticose lichens and lithophilic mosses settle in places on the rocks, and mosses are much more common on a fine-earth substrate. The flora of green and blue-green algae is abundant in rock crevices and on fine-earth substrate.

Penguin settlements and seal rookeries in the coastal and insular 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. On the coast, in addition to various species of seals, there are more than 10 species of birds: penguins, petrels, skuas, etc.

Thus, in glacial (ice) deserts, all signs of desert weathering and soil formation are clearly and everywhere expressed: very weak clay formation, 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 catenas. mesorelief elements.

tundra zone

The tundra zone is located south of the arctic zone. In Eurasia, it extends from the northwest of the Kola Peninsula to the Bering Strait. Four provinces are distinguished on the territory of the tundra: Kola, Kanin-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. With an average July temperature below 10-12, trees can no longer grow. Summer, in our understanding, if we call summer days with an average daily air temperature above 12, as a rule, does not happen in the tundra.

From west to east, the climate of the tundra becomes more continental - precipitation becomes less, and winters are colder. The Murmansk coast, which is 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 delta of the Lena River 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, and the climate again becomes more maritime: winters are not so frosty, but summers are cooler.

Frosts stand in the tundra from 6 to 8 months, in the delta of the river. Lena even up to 8 1/2 months. However, in winter it is warmer in Murman than on the northern coast of the Caspian: January is -6 here, while in Astrakhan -9. In the Siberian continental tundra, frosts reach -50 in January. Winters inland are colder than on the coast. But the summer on the coast is very cool. In summer, the weather in the tundra is unusually changeable: warm days with a positive temperature of 15-20 and warm nights alternate with rainy and cold days, when the temperature drops to -4 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. In the southern parts of the Subarctic, the air temperature can stay around 25 for several days.

But the level of maximum temperatures is not yet a 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 may even breed in the winter on the tundra, as lemmings do. But the main part of the tundra community is active only in the summer (vegetation, microorganisms, invertebrates). In summer, all the main abiotic processes in the landscape also take place: weathering, erosion, permafrost thawing, etc. Therefore, of paramount importance in the life of the tundra is the duration of the frost-free period, which determines the main features of the tundra landscape, its organic world.

The total amount of precipitation in the tundra is insignificant, on average 150-250 mm with deviations to the smaller and larger sides. In terms of precipitation, the tundra approaches the desert regions of low latitudes. However, there is a lot of water in the tundra, high soil and air humidity. Large areas are occupied by swamps. The tundra is more humid 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. Ground ice, snow, melt waters, fogs and prolonged drizzling rains are all the most 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; protection of plants and animals from winter cold; snow corrosion; limiting the terms of active life, etc. The role of snow as a heat insulator protecting soil, vegetation and animals from low winter temperatures is widely known. In winter, under snow, the conditions are quite favorable not only for keeping 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, white hare, white and tundra partridges. All of them must somehow get to the vegetation hidden under the snow. In the southern half of the tundra zone, the white hare eats bushes sticking out from under the snow in winter. There are few hares in the tundra, and this meager and coarse food is enough for them. But there is not enough food for deer and partridge here. They cannot break through a thick layer of very dense snow and migrate to the south in autumn, to the forest-tundra and taiga, where the snow is loose and where there is more food.

The Arctic is nival landscapes, 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, determines the possibility of the existence of many species, protecting them from the winter cold. Protecting biotopes from winter cold, snow promotes the habitation 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, is intensifying. All this increases the diversity of the flora and fauna of the North. And this is the guarantee of prosperity and sustainability of tundra communities.

Relief. Most of the tundra is dominated by a flat terrain, in some places hilly, ridged or ridged, abounding in closed thermokarst depressions occupied by lakes and swamps. In some provinces, the relief is typically mountainous (Khibiny, the Polar Urals, the Byrranga mountains, the Chukotka mountain range, etc.).

Permafrost phenomena - crack formation, heaving, solifluction (sliding of soils along a slope), thermokarst - form a spotty-small-polygonal and tuberculate (spotted-tuberculous) microrelief on tundra watersheds and their slopes, a large-polygonal, flat- and coarse-hilly microrelief - on vast marsh plains. From north to south of the tundra zone, abyssal and thermokarst microforms (hillocks, hillocks) become increasingly important.

Rocks- glacial, marine and alluvial deposits of various mechanical composition, often very stony. In the mountains, soil-forming rocks are predominantly represented by coarse skeletal eluvium of bedrocks.

Vegetation. General landscape-forming features of phytocenoses of the tundra zone 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 determine the dominance of mosses and lichens, shrubs and shrubs, short stature and sparseness of perennials. Annuals are practically absent.

2. Tundra vegetation develops in conditions of excessive 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 (as well as desert plants): small leaves, pubescence, wax coating and etc.

3. Low compared to other natural areas of the Earth, the amount of synthesized biomass (4-5 c/ha) and the slow pace of its humification and mineralization. In this regard, prerequisites are created for the accumulation of semi-decomposed plant residues (peat) on the soil surface. Due to excessive moisture, peat formation and gleying processes are facilitated by the dominance of anaerobic processes, both in the organic and in the mineral part of the soil mass.

4. According to the chemical composition, plant residues are characterized by an exceptionally low ash content. When they decompose, organic acids are formed, causing a strong acidification of the soil mass.

Animal world The tundra is characterized by poor species composition with a high number of animals. Severe winter conditions are tolerated by only a few species: lemmings, arctic fox, reindeer, white partridge, snowy owl, hare, polar wolf, ermine, long-tailed ground squirrel, weasel, etc. In the tundra of North America, in addition, live musk ox (musk ox ) and caribou - an analogue of the reindeer. In summer, a mass of migratory birds appear in the tundra, arriving to nest and attracted by an abundance of various foods (brants, geese, sandpipers, 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 there is a layer of earth that freezes in winter and thaws in summer. It's called active layer. Its value 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 take place and soils develop. The wall of the gallery, carved into the permafrost, resembles 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 with lenses of ice. This stone 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 of sub-zero temperatures of the surface atmosphere.

Permafrost is one of the factors that maintain the swampiness and water content of tundra landscapes, as it is an aquiclude that prevents vertical water filtration and drainage of the territory. And, of course, permafrost is a constant “refrigerator” that reduces the biological activity of soils and weathering crusts.

ground cover. The predominant soils of the tundra are of the peat-gley type. The main soil-forming processes are: peating 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.

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, acid reaction of the environment, toxic compounds of reduced iron and manganese.

The gley horizon, due to oversaturation with moisture, often has thixotropic properties associated with the characteristics of mineral colloids. Thixotropy- the phenomenon of the transformation of a solid soil mass into a fluid one (gel into a sol). This occurs when 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 passes into a floating state.

The formation of spotted tundra. Spots of bare soil (usually 40-50 cm in diameter) are surrounded by a somewhat raised ridge of solid moss sod. Rolls of neighboring spots are separated by depressions - hollows filled with peat and loose moss sod. Usually spotted tundras are confined to high terraces. Their formation is associated with the processes of soil cracking, rupture of moss sod, and extrusion of waterlogged soil onto the surface.

Bare soils in the spotted tundra 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 variety of ecological conditions, due to which the vegetation and fauna are diverse in the spotted tundra.

With the onset of autumn, hypothermia and freezing of the active soil mass begins from permafrost. The upper horizons are insulated with a moss cover. The increase in pressure during freezing leads to the spreading of the thixotropic soil mass of the gley horizon.

Common in northern tundra polygonal tundra, which is formed on homogeneous sandy-loamy deposits. Usually polygons consist of four-, five-, hexagons. Convex areas of fine-earth material of the polygonal tundra are very often bordered by stony fragments displaced from fine-earth material as a result of cryogenic phenomena. This freezing of stones on the soil surface is also associated with the formation of ice under the stone in its absence above it. The expanding ice, as a result of many years of cycles, pushes rocks to the surface. The freezing of stones to the surface is also due to the fact that the freezing of soils begins from permafrost.

A specific element of tundra landscapes is mounds-hydrolacoliths. Their height varies from 1 m (diameter 2-5 m) to 70 m (diameter 150-200 m). The appearance of hillocks is explained by heaving of the soil as a result of the formation of an underground ice lens. Outside, the hillocks are covered with a peat layer about 1 m thick. Beneath it is frozen mineral soil, consisting of fine earth deposits, with a thickness of one to several meters. 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.

The 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, pits are formed, which destroy all ground structures and, first of all, the road network.

In the tundra there is another type of peculiar landscapes - hilly swamps. On 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 - swampy watered areas. These swamps are most characteristic of the subzones of the southern and typical tundras of the western sector of the Subarctic of Eurasia. To the north, and especially in the arctic tundra, they are becoming less and less.

Solifluction, the formation of spotted and polygonal tundras, hydrolacoliths, thermokarst and some other phenomena are combined 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, stay in a frozen state and thaw. There are three stages of cryogenesis: 1) the stage of cooling-freezing, which begins at the appearance of zero temperature and ends with the complete freezing of the entire soil profile or its part capable of freezing 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 freezing layer.

Cryogenesis occurs in all freezing soils. The longer and deeper the freezing and the lower the temperature, the more noticeable the specific effect of cryogenesis, which is most pronounced 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.

subzone of arctic tundra. The extreme north is the arctic tundra subzone, in which not only trees are absent, but also shrubs, or the latter appear only along the rivers. There are absolutely no sphagnum peatlands 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 tundras of northern Yamal, northern Taimyr and the southern New Siberian Islands, the islands of Vaigach, Novaya Zemlya, and Wrangel. This subzone is located in the real Arctic climate. At its southern border, the average July temperatures are 4-5С, at the northern border - about 1.5С. Temperatures below 0C and snowfall are possible throughout the summer. The thickness of the snow cover is insignificant, therefore winter conditions for animals and plants are especially severe.

The main feature of the Arctic tundra landscape is the ubiquitous distribution of bare soils. On the watersheds, various variants of communities are developed, in which patches of bare ground are surrounded by vegetative sod. They are called spotted, medallion, polygonal spotted, etc. Bare soils occupy about 50% of their area. A moss cushion with sprigs of dwarf willows interspersed in it, saxifrage, grasses is located along a frost crack around bare ground. The Arctic tundras are very diverse: stony, gravelly, clay with a regular medallion structure, with vegetation cover in the form of curtains, strips, nets, etc. Permafrost phenomena in the arctic tundra subzone are very diverse and noticeable everywhere.

Weak weathering and intense cryogenic (permafrost) processes create a very diverse, sharply intersected micro- and nanorelief in the Arctic tundra. There are a lot of rock fragments and rubble everywhere. The surface of the soil is covered with cracks, hollows, tubercles. The bare soils of the Arctic tundra at first glance seem lifeless, but a rich world of organisms develops on them. The upper soil layer is inhabited by a mass of unicellular algae and nematodes that feed on them, enchitreids, springtails and larger animals - earthworms, larvae of centipede mosquitoes. On the surface there are many scale lichens that look like mold. Flowering plants are scattered among the rubble - cereals, poppies, siversia, dryad, mytniki, saxifrage, grains, forget-me-nots, etc. Neither taiga, nor forest-tundra, nor south-tundra species penetrate into the arctic tundra. For example, there are absolutely no such species as dwarf birch, crowberry, alpine arctous, cowberry, blueberry, cloudberry, sedge, white partridge, sandpipers - dandy and small godwit, Middendorf's vole. Here, many characteristic mass inhabitants of typical tundras, such as the oystercatcher, dunlin, are also few or absent. All this emphasizes the extreme specificity and originality of the climatic regime of this subzone. To live here, special adaptations are needed to exist in these harsh conditions.

Typical tundra subzone. South of the arctic tundra there is a wide subzone of typical, or shrubby, tundra, where there are also no trees, but shrubs and, in particular, shrubs are found not only along river flows, but also on interfluve watersheds. Its boundaries roughly 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 Yugorsky peninsulas. Between Yana and Kolyma and on the rest of it - only small, mostly southern, fragments. It is completely absent on the mainland west of the Yugra Peninsula.

This subzone is the embodiment of the type of landscape that is called the tundra. There are not only trees here, but rather 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 the valleys of streams and along the banks of lakes, where a lot of snow accumulates.

Typical tundra is the realm of mosses. A powerful moss cushion 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 controversial role in the life of the tundra. It is the mosses that ensure the complete density of vegetation in the watershed spaces. 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 negatively affects the development of organisms. The thicker, denser it is, the colder the soil and the higher the level of permafrost. On the other hand, the moss cover prevents the occurrence of thermokarst and thus has a stabilizing effect on the vegetation. The disastrous consequences of moss turf being torn off as a result of, for example, the movement of caterpillar vehicles are well known.

The moss sod serves as a habitat for a rich complex of invertebrates called 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, enchytreids, larvae of long-legged mosquitoes, ground beetles, etc. The life of lemmings depends on mosses. They lay complex labyrinths of passages in the sod, 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. There are many creeping shrubs (polar willows, dwarf birch, partridge grass, cassiopeia, cowberry, crowberry, etc.). Sometimes cottongrass and dicotyledonous herbaceous plants (saxifrage, wintergreen, Asteraceae, etc.) are plentiful. In some places in the moss sod there are many lichens (leafy, tubular, bushy, scale, etc.).

In addition to the main communities with a continuous moss cover, spotted tundras are also very common in the subzone.

Southern tundra subzone. To the south of the typical tundra, in the form of a narrow strip, the subzone of the southern tundra stretches. There are already trees in this subzone, but the forest areas formed by them are located only along the rivers. On the watersheds there are only shrubs, at most single trees. Sphagnum peatlands are well developed and already in large numbers.

A shrub layer is developed on the main areas of the watersheds. It is formed by birches, willows, alder. Under the canopy of shrubs, herbaceous plants (sedges, cotton grasses, cereals), shrubs (blueberries, lingonberries, rosemary) are plentiful. Below is a continuous moss cover.

In the southern tundra, there are single woody plants, most often larches. They are undersized, have curved thin trunks or a special, dwarf shape.

In the southern tundra, the vegetation cover is very diverse. The watersheds are interspersed with thickets of willows, birch (dernik), alder and tundra without shrubs with a continuous moss cover or with patches of bare ground. Various bogs are developed in the depressions - hypnum, sphagnum, flat and with peat mounds. On the southern slopes there is a vegetation cover of cereals, legumes, various herbs. On the raised brows there are thickets of berry bushes and semi-shrubs: lingonberries, blueberries, crowberries, arctous, etc. Near water, near lakes and along the banks of streams, various near-water 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 wealthy communities. The flora and fauna are very diverse here. In addition to typical tundra species, there are many inhabitants of middle latitudes. For example, in the European and Siberian southern tundras of plants, you can everywhere find the usual ones in the middle lane - marsh cinquefoil, common spleen, marsh marigold and even heat-loving common thyme; from birds - warbler, thrush, common snipe and short-eared owl. Pintail nests here on the lakes, and along with typical tundra rodents, there is a widespread root vole.

Forest-tundra subzone. On the southern outskirts 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 river flows, but, in the form of islands, also rise to interfluve watersheds. Sphagnum peat bogs reach great development here and form a special type of hilly tundra.

Forest-tundra - a zone of low forests of dwarf birch, small willow, juniper with separate undersized trees of spruce, larch. The harsh conditions of the tundra, the lack of nutrients, the presence of permafrost at shallow depths hinder the growth and development of woody plants. Trees aged 200-300 years are undersized, gnarled, knotty, 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 dwarf form, which is formed by many tree species in the Subarctic. Sometimes they form dense, impenetrable thickets. Dwarfs are especially characteristic of mountainous regions and the Far Eastern North, where the tundra landscape descends to very low latitudes and captures the areas of many tree species. Thus, elfin cedar is widespread everywhere, which is sometimes considered a variety of cedar pine, sometimes a special species. Favorable conditions are created in the thickets of elfins for wintering animals: under the snow lying on top of thick bushes there are many voids, in some places the surface of the litter or soil is open. This makes it easier to move around and get food.

Some features of the animal world. Among the animals found on the territory of the Subarctic there are a lot of predators: the wolf, the fox, the wolverine, the brown bear, the weasel, the ermine, and several species of shrews. This is a characteristic feature of the mammalian fauna of the tundra. However, all of the listed species are aliens 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 polar fox is the only native tundra species of predatory animals that is of significant importance in the biocenoses of the Arctic. On the other hand, among the herbivorous rodents and ungulates there is the largest number of the most characteristic tundra endemics. These are ungulate and Ob lemmings, musk ox and reindeer, narrow-skulled vole and Middendorf's vole.

The most impressive are the wild deer. Wild deer have been preserved mainly in the form of three herds: on the Kola Peninsula under the conditions of a protected regime, in 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 domestic grazing 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 disturbance of the vegetation cover. The mountainous areas of Putorana, where wild reindeer concentrate for wintering, are also hardly suitable for use by reindeer herding farms. Contacts between wild and domestic reindeer in these areas are possible only for 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 come to nest in the summer: tundra and American swans, partridges, red-throated goose, snowy owl, loons, waders, etc.

Agricultural use of the tundra. Farming in the tundra zone on a large scale is impossible. Only small consumer gardening is widespread in it, turnips, radishes, onions are sown and potatoes are planted.

The main occupation in the tundra is reindeer herding, based on scarce fodder reserves. The main winter pasture for deer is lichens - reindeer moss, which, in the form of lichen tundra, although they occupy a fairly large area, grow extremely slowly, and, in particular, do not renew well after grazing and trampling. The increase for various subzones is: in the forest tundra - 4-6 mm over the summer, in a typical tundra - 2-3 mm and in the arctic - 1-2 mm.

It goes without saying that after their destruction by grazing, lichens on pastures resume extremely slowly. In various regions, the renewal period, which is practically equal to the turnover of pastures, is determined on average 15-30 years. A heavily degraded reindeer pasture should not be revisited earlier than after 15 years.

Yagel and other lichens make up the dominant, almost 9 months of the year, but not the exclusive food of deer. In the summer, when the snow melts in the tundra, the reindeer 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 predominantly a carnivore, and not a herbivore, in the presence of shrubs and herbs, he always prefers the first. At this time, its food is mainly branches, leaves and young shoots of dwarf birch or polar birch and willows, to a lesser extent herbaceous plants: sedges, cotton grass and cereals.

The protein regime of reindeer food is also peculiar. Since lichens are poor in nitrogenous substances, feeding the animal with them for 8-9 months causes all the signs of protein and mineral starvation in it. To cover the lack of proteins during the summer, deer are extremely willing to eat various mushrooms, which often appear in abundance in drier parts of the tundra. All autumn, and sometimes the beginning of winter, digging out dried mushrooms from under the snow, deer are busy looking for mushrooms, and a crop failure causes a lot of trouble for reindeer herders.

Thus, reindeer herding is naturally a nomadic economy, because in winter it needs lichen pastures, in spring wet low-lying swamps and river valleys, and in autumn dry moss-lichen or moss tundra.

The tundra of North America is part of the natural tundra zone of the Northern Hemisphere.

The Arctic tundra is an area of ​​low, flat and swampy coastal plains covered with lakes filled with melted ice.
The American tundra zone occupies the northern part of the mainland of North America and runs from Northern Alaska along the coast of Hudson Bay to the north. In the east, where the influence of the Labrador current affects, the tundra extends to 55-54 ° N. sh.
To the north of the border of broad-leaved and coniferous trees, shrub tundra extends, 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 go 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 region is in many ways similar to the forest-tundra and taiga, there is nothing surprising in the fact that suddenly for a traveler, low and bent in all directions vegetation in open places is suddenly replaced by tall trees in river valleys and at the foot of mountains.
However, when moving north, the predominance of real tundra with mosses, lichen, sedge and cotton grass becomes more and more noticeable, and tree massifs disappear completely.
A feature 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 vegetative period 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, nicknamed pingo in Sulfur America.
The climate of the North American tundra is very harsh. The wind here is gaining extreme strength, it blows snow into the lowlands, where snow drifts are formed, which persist even in summer. It is precisely because of the lack of snow on the plains that the soil freezes through and does not have time to warm up in a short summer. Over a larger area, the climate of the Arctic tundra is more humid and damp than within the boundaries of the circumpolar tundra, which extends from American Alaska to the east - up to Canadian Quebec.
Separately, the tundra of the north-west of North America is distinguished - the Alaska Range and the Saint Elijah Mountains. This ecoregion includes the mountains of the interior of Alaska, which are permanently covered in ice and snow. Those rare areas that remain free of ice are stony, rocky and high mountain tundra.
The occupations of the local population in the tundra of both North America and Eurasia are similar. These are reindeer husbandry (the Arctic tundra becomes vast pastures for reindeer in the summer), hunting for sea animals (according to quotas from the Ministry of Natural Resources), and fishing. Of the crafts - bone carving and sewing clothes and shoes from deer skins. There are no large cities in the tundra of North America.
The biggest danger threatening the tundra of North America comes from oil and gas pipelines, the development of hydrocarbon deposits and global warming.
The fauna of the North American tundra is much richer in species composition than vegetation. Of the large mammals, caribou deer, brown bear, polar wolf, polar weasel, polar bear and musk ox (musk ox) predominate, of small mammals - fox, arctic fox, lemming and ermine, of birds - white goose, black goose, white and tundra partridge , Alaskan plantain (bird of the oat family) and snowy owl, from 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 tundra of North America is characteristic only for these places. It took experts a long time to figure this out. For example, at the dawn of studying the animals of North America, the caribou deer and the Eurasian reindeer were considered different species (today in America there are two subspecies of caribou - tundra and forest), and along with them - the American and Eurasian elk. 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 completely identical.
There are many examples of this. The gray-haired marmot is a typical inhabitant of the mountainous American tundra - the 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 do not know that he disappeared from the tundra of Eurasia during the time of primitive people who mercilessly destroyed the animal population.
In general, most of the 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 arriving on the Labrador Peninsula, even several species of tropical hummingbirds, juncos (a genus of passerine birds from the bunting family, characteristic only for North America) ), savannah bunting (only occasionally found in the tundra of Chukotka), Canada goose (the most widespread species of game birds here).
The further north, the poorer the fauna and the more its life is connected with the sea: these are auks and gulls nesting on the rocks, and pinnipeds with polar bears. A rare visitor from the depths of the southern tundra is the arctic fox and snow bunting.
The problems associated with pollution of the tundra are largely similar for different parts of it due to the nature of the minerals being developed here, their storage and transportation. Despite the strictest control and multimillion-dollar fines for leaks from oil pipelines, environmental pollution continues, deer refuse to use special passages, and road trains rip off the top protective layer of tundra soil with their caterpillars, which takes almost a hundred years to restore.

general information

Administrative affiliation: USA, Canada.

Languages: English, Eskimo.
Ethnic composition: Whites, African Americans, Indigenous peoples (Eskimos, Athabaskan Indians, Haida, Tlingit and Tsimshians).
Religions: Christianity (Protestantism), traditional religions.
Monetary units: Canadian dollar, US dollar.

Large rivers:, Anderson, Horton (Canada).

Numbers

Climate and weather

January average temperature: up to -30°С.

July average temperature: from +5 to +10°С.

Average annual rainfall: 200-400 mm.

Relative humidity: 70%.

Economy

Industry: oil refining, petrochemical, food (meat-packing, flour-grinding).

Seaports.

Agriculture: animal husbandry (reindeer breeding).

Hunting and fishing.

traditional crafts: bone carving, making clothes from deer and polar fox skins.
Service sector: tourism, transport, trade.

Attractions

■ Natural: Gates of the Arctic National Park and Preserve (Alaska, USA), Kobuk Valley National Park (Alaska, USA), Wapusk and Yukkusayksalik National Parks (Hudson Bay Coast, Canada), Gros Morne National Park ( Newfoundland Island, Canada), Thorngat Mountains National Park (Labrador Peninsula, Canada).

Curious facts

■ Labrador tea tundra plant has red leaves to use chlorophyll and the sun's heat to keep the internal heat. None of the tundra animals eat it.

■ During the year, the North American tundra receives less precipitation than the desert.

■ The Mackenzie River was discovered and first passed by the Scottish traveler Alexander Mackenzie in 1789. Its original name is Disappointment, which literally means “disappointment” in English. By giving the river such a strange name, Mackenzie expressed his own frustration at the fact that it led him not to the Pacific Ocean, but to the Arctic Ocean.

■ The term "pingo" as a typical North American designation of heaving 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 highway along the Trans-Alaska Pipeline, which runs from Barlow to the Pacific port of Valdez and poses the biggest threat to the ecology of the North American tundra.