The vegetation of the tundra and forest-tundra, its forms, methods of plant reproduction, and adaptability to survival largely depend on the features that characterize these zones.

Geographical location

The location of the tundra zone falls on Earth. On the Eurasian continent it stretches along the entire coast of the North Seas Arctic Ocean for tens of thousands of kilometers. The northern coast of mainland North America is also occupied by tundra. The length of the zone from north to south is on average about 500 kilometers. In addition, tundra occupies some islands near Antarctica. In the mountains, where it is expressed altitudinal zone, mountain tundras are formed. Taking into account all the territories where the zone is located, its total area on the planet. It is about 3 million km2.

Forest-tundra is a zone where tundra vegetation and taiga vegetation are located in small areas. Forest-tundra stretches from west to east to the south of the tundra on the continents of Eurasia and North America. The length of the strip from north to south ranges from 30 to 400 kilometers. On its southern borders the forest-tundra turns into a forest zone.

Climatic conditions affecting plant growth

The climate of the tundra and forest-tundra zone is very harsh. The duration of winter is from 6 to 8 months a year. During all this time there is a constant snow cover, the air temperature sometimes drops to 50 degrees below zero. The polar night lasts about two months. Strong cold winds and snow storms almost never subside.

Summer in the tundra is short and cool. Frosts and precipitation in the form of snow are possible. Despite the surface of the earth, it does not receive much heat, since the sun does not rise high above the horizon and sends scattered rays to the earth. To survive in such conditions, tundra vegetation must adapt.

The influence of permafrost on the species composition of vegetation

During the warm season, in the tundra zone the soil thaws only to a depth of no more than 50 centimeters. Next comes a layer of permafrost. This factor is one of the decisive factors in the spread of plants in the tundra zone. The same factor affects their species diversity.

Permafrost has a significant impact on the terrain. Freezing and thawing of rocks leads to their deformation. As a result of the heaving process, surface forms such as bumps appear. Their height is no more than two meters above sea level, but the appearance similar forms also affects the vegetation of the tundra, its distribution across certain territory.

The influence of soil on the species diversity of vegetation

In the tundra and forest-tundra zones, high temperatures are observed. It is especially noticeable during the period of snow melting. Water cannot penetrate deep due to the presence of permafrost. Its evaporation is also not very intense due to the low air temperature. For these reasons, meltwater and precipitation accumulate on the surface, forming large and small swamps.

High swampiness, presence of permafrost, predominance low temperatures impede the flow of chemicals and biological processes in the soil. It contains little humus and ferric oxide accumulates. Tundra-gley soils are suitable for the growth of only certain types of plants. But tundra vegetation adapts to such living conditions. A person who has visited these parts during the flowering period of plants will have indelible impressions on for many years- the blooming tundra is so beautiful and attractive!

In the forest-tundra, the natural fertile layer of the earth is also thin. The soil is poor nutrients, it is characterized increased acidity. When cultivating land, add to the soil composition large number mineral and organic fertilizers. In the treated areas of the forest-tundra, there is a more diverse variety of herbaceous vegetation, trees and shrubs.

Types

The vegetation of the tundra and forest-tundra largely depends on the type. Their landscapes seem monotonous only at first glance.

The hummocky and hilly tundras occupy the most large areas. Among the swamps, the plant turf forms mounds and hummocks, on which many species of plants take root. A special type of tundra is polygonal. Here you can see them in the form of large polygons, which are broken by depressions and frost cracks.

There are other approaches to classifying such a natural zone as the tundra. What vegetation predominates in a certain area will be the type of tundra. For example, moss-lichen tundra consists of areas covered different types mosses and lichens. There are also shrub tundras, where thickets of polar willow, dwarf pine, and bushy alder are common.

Plants

As mentioned earlier, the vegetation of the tundra and forest-tundra had to adapt to the harsh climatic conditions subarctic zone of the Earth. Otherwise, her life and development would be impossible here.

The adaptability of tundra and forest-tundra plants is expressed in the following. Most of the fauna are perennials. Annual plants with a short summer would not be able to complete their life cycle. Only a small part of plants reproduces by seeds. The main way to prolong life is vegetative.

The short stature of tundra plants allows them to survive during strong winds. This is also facilitated by the creeping nature of the shoots and their ability to intertwine with each other, forming something like a soft pillow. IN winter period all parts of the plants are under the snow. This saves them from severe frosts. Most tundra and forest-tundra plants have a waxy coating on their leaves, which promotes moderate evaporation of moisture from their surface.

The vegetation of the tundra, photographs of individual species of which are available in the article, is represented by perennial frost-resistant grasses, buttercups, cotton grass, dandelions, and poppies that dominate the lowlands and swamps. The trees include dwarf birch and bushy alder. These tree species in the forest-tundra can already reach a height of three meters or more. Among the shrubs, blueberries, cloudberries, blueberries, and lingonberries are widespread. Mosses and lichens take root at higher elevations, many of which are the main type of food for the animals living in these places.

Forest-tundra and taiga

The vegetation of the tundra and taiga is very different from each other. Forest-tundra is a transition zone between them. On the territory of the forest-tundra, among the treeless space, you can find islands of thickets of spruce, birch, larch and other tree species.

The forest-tundra zone is unique, since tundra vegetation and taiga vegetation are found on its territory, which becomes more noticeable as you move south. Forest areas consisting of individual breeds trees and shrubs, create the most favorable conditions for the growth of herbaceous vegetation. Thanks to trees and shrubs, wind speed is reduced and delayed more snow that covers plants, saving them from freezing.

Study of vegetation of the subarctic zone

The vegetation cover of the tundra and forest-tundra has not yet been fully studied. Systematic scientific description of the species growing here began only in the middle of the last century.

To continue this work, special expeditions are being created today. During them, scientists are also trying to establish how the vegetation of the tundra and forest-tundra is influenced by the animals living in these zones. They want to get answers to questions about whether the species diversity of plants changes in areas protected from the presence of certain species of animals, how long it takes to completely restore the destroyed vegetation cover. So far, scientists have not found answers to all questions regarding the natural balance in the subarctic zone of the planet.

Fauna protection

The nature of the tundra and forest-tundra is very vulnerable. It takes dozens of years, and in some cases centuries, to restore the soil layer and vegetation cover.
Man has long realized that it is he who has a detrimental effect on the nature of the tundra and forest-tundra. Trying to atone for their guilt, people created a number of nature reserves, national parks, reserves. They are located both in Russia and other countries of the world.

The youngest landscape zone on the Russian Plain is tundra. It was formed only after the death of the Valdai glacier.

Some, although not particularly significant, fluctuations in the boundaries of landscape zones were observed in post-glacial times. In particular, there is a lot of evidence suggesting that during the climatic optimum (Atlantic period) most of the continental tundra of the Russian Plain was captured by taiga and forest-tundra.

Tundra and forest-tundra are two independent landscape zones. However, the forest-tundra on the Russian Plain is presented as a narrow strip that has not yet been sufficiently studied, therefore, for convenience of description, it is combined here with the tundra zone.

The tundra and forest-tundra zones include the Arctic islands: Franz Josef Land, New Earth, Vaygach, Kolguev and the coast Barents Sea on the mainland.

The southern border of the forest-tundra on the mainland passes near the Arctic Circle, and the northern island of the Franz Josef Land archipelago lies at latitude 81045 "N. This geographical location determines the small amount of total solar radiation in the tundra. And although in the summer, during a continuous polar day, solar radiation and reaches more or less significant sizes, but the overwhelming majority of it is used not for heating the soil and air, but for the evaporation of moisture. Therefore, the air temperature in the tundra and forest-tundra is low even in summer: the average July temperature in the forest-tundra is about 12°, and on Franz Josef Land it is close to zero.

The severity of summer in the tundra and forest-tundra increases due to the fact that their territory is washed by the waters of the Barents and White Seas, which absorb a lot of heat spent on melting ice and heating water. But in winter, the seas “heat” the territory of the tundra and forest-tundra and prevent a sharp cooling of the air. The latter is especially noticeable on the Murmansk coast, where the Barents Sea does not freeze even in winter. Average temperature January on the Murmansk coast is higher than --10°, and only in the north of Novaya Zemlya and on Franz Josef Land does it drop below --20°.

In addition to the seas, the weakening of the climate continuity of the European tundras is strongly influenced by active cyclonic activity. It is associated with the passage of the Arctic front over the Barents Sea. In winter, warm masses of Atlantic air come here with cyclones, causing unstable weather with heavy precipitation. The annual precipitation in European tundras is 300--400 mm; this is much more than the annual precipitation in the tundra of Siberia.

Tundra and forest-tundra are young landscapes. Their territory was freed from continental ice later than other areas. Here, traces of the presence of the glacier are clearly visible in the relief, and the north of Novaya Zemlya and a large part of the Franz Josef Land archipelago are still hidden under ice.

The formation of tundra and forest-tundra landscapes occurs under conditions of prevailing frost weathering; the activity of the biological components of the landscape - vegetation, fauna and microorganisms in the soil - is not very active. It intensifies to the south - in typical tundra and forest-tundra. In the Arctic deserts, on Franz Josef Land, the tundra landscape is in the first stages of formation: lichens, mosses and flowering plants clinging to the soil grow in separate clumps, most often along frost-cut cracks in rocks. In the typical tundra subzone there is a fully formed landscape well adapted to the cold climate of the North with developed moss-lichen, shrub and shrub cover.

In landscape terms, the tundra zone is divided into three subzones. The Arctic desert subzone includes Franz Josef Land and northern Novaya Zemlya. Natural conditions subzones are characterized by exceptional severity. Average temperature warm month-- July -- below 4.5°. The soils of Arctic deserts are polygonal, skeletal, with sparse and in some places completely disappearing plant cover. We believe, just like L. S. Berg and I. M. Ivanov, that this subzone can be considered as an independent ice zone; The landscape feature of this zone throughout the year is ice and snow. Name " ice zone" conveys the essence of the landscape of the extreme latitudes of the Arctic more fully than " arctic zone", as some researchers suggest calling it.

Subzone arctic tundra distributed in the south of Novaya Zemlya, Vaigach Island and the coast of Baydaratskaya Bay. The average July temperature here is 5-6°. The vegetation, as in the previous subzone, is very poor; only a few species of low-growing grasses and shrubs rise above the moss-lichen ground cover. The subzone is heavily swamped, with peaty-gley soils and hypnotic bogs predominating.

Typical tundra is characteristic of the entire continental coast of the Barents Sea. The average July temperature there reaches 6-10°. In the north of the subzone, moss and lichen tundras are predominantly developed; in the south, shrub tundras with thickets of polar willow and polar birch grow. Unlike the two previous subzones, sphagnum bogs here acquire landscape significance.

The vegetation cover of a typical tundra is often very similar to the corresponding tiers of the taiga - moss-lichen and shrub. Looking at some areas of the moss-lichen tundra, dotted with blueberries or lingonberries, you can’t help but think that there was once a lot of noise here coniferous forests. There is nothing surprising in such an assumption. Between the tundra and the moss-lichen and shrub cover of the taiga there is not only a physiognomic similarity, but also a genetic commonality. During the post-glacial climatic optimum, forests, most likely of the forest-tundra open forest type, covered almost the entire continental tundra of the Russian Plain. Later, due to climate cooling, the forests retreated to the south, and the moss-lichen and shrub layers, in a modified form, became part of the tundra vegetation cover.

L. S. Berg believed that the advance of the tundra into the forest, caused by climate cooling, continues to this day. G.I. Tanfilyev also assumed that the tundra was encroaching on the forest, but he saw the reason for this, unlike L.S. Berg, not in the cooling of the climate, but in the fact that huge snowdrifts were blowing up on the edges of the forest, the melting of which leads to waterlogging soil and death of tree species.

A different view on the relationship between the tundra and forest was held by V. R. Williams. In his opinion, the young tundra landscape over time, regardless of general climate changes, evolves into a forest landscape, and therefore, at present, it is not the tundra that is advancing on the forest, but the forests on the tundra.

Observations over the last two decades show that in nature there is an encroachment of forests onto the tundra. The process of forest encroachment on the tundra is not local, but universal in nature; it is noted in the tundras of the Russian Plain, Eastern and North-Eastern Siberia, North America. Now it is difficult to say whether the encroachment of forests on the tundra is the result of a directed climate change towards warming, or whether it is a consequence of short-term, periodic climate fluctuations and soon the encroachment of forests on the tundra may stop or be replaced by the opposite process - the encroachment of tundra on the forest.

In addition to climate, the relationship between the tundra and forest is influenced by other factors that should not be forgotten. In particular, in tundras that have recently been freed from a glacier, the erosive dissection of the relief increases, and this improves drainage and increases the forest suitability of the tundra, and promotes the movement of forests to the north. Another important factor-- human activity. For many centuries, people have destroyed forests in the forest-tundra. Many northern island forests have disappeared without a trace under the influence of human activity. It is precisely such artificially deforested areas that are primarily captured by the forest as it moves north. Therefore, in case of protection northern forests and moderate use of forest-tundra for pastures, it is possible to expand the forest area, not associated with changes in any natural components of the landscape.

Regardless of the reasons causing the forest to encroach on the tundra, this process is of great economic importance. It creates favorable conditions for afforestation of the forest-tundra and southern regions of the tundra. Successful experiments in afforestation in the tundra have already been carried out in the area of ​​​​the cities of Naryan-Mar and Vorkuta and along the Pechora railway. Afforestation of the tundra will improve its microclimate and increase the productivity of northern meadows and pastures.

Forest-tundra is a natural zone of the subarctic zone, transitional from tundra to taiga, characterized by the widespread development of open forests and clearings. B. N. Gorodkov, L. S. Berg and V. S. Govorukhin consider it a subzone of the tundra zone; There are researchers who classify forest-tundra as taiga. For example, in the book “Physical-geographical zoning of the USSR” (1968), compiled by different authors: on the Russian Plain the forest-tundra is included in the tundra zone, in Western Siberia it is represented independent zone, and in Central Siberia, being combined with the northern taiga, separated into special zone forest-tundra and northern woodlands. Northern border forest-tundra coincides with the northernmost areas of open forests on watersheds, the southern - with the extreme southern areas of tundra in watershed conditions. The length of the zone from north to south is relatively small - from 20 to 200 km. Like the tundra zone, forest-tundra is located mainly north of the Arctic Circle.

The climatic conditions of the forest-tundra are similar to the climate of the tundra zone. The most significant difference is that summer in the forest-tundra is warmer and longer than in the tundra. The average air temperature here in July reaches 11.0-14.0°. The sum of temperatures for a period with a stable temperature above 10° is equal to 600–800° west of the Yenisei and 400–600° east of it. This is the first zone, if you move from north to south, where meteorological summer is noticeably pronounced - the time when the average daily air temperature rises above 15°. In the area of ​​Murmansk, Salekhard and Dudinka it lasts about 20 days. On the contrary, in winter the forest-tundra is colder than the tundra. The average air temperature in January ranges from -10 to -38°. The greater severity of winter is explained by the fact that the forest-tundra is located at some distance from sea ​​coast, lies in close proximity to the supercooled interior of Eurasia. For the same reason, wind speeds in the forest-tundra are somewhat lower than in the tundra, and the snow cover, due to the presence of forests, is more evenly distributed.

Permafrost occurs throughout the entire forest-tundra, but in the west of the zone it has an intermittent distribution. The zone is characterized by thermokarst processes associated with the presence underground ice, and swelling mounds (hydrolaccoliths).

The annual amount of precipitation in the forest-tundra is 150-450 mm, which is much greater than the evaporation rate. A positive moisture balance and permafrost contribute to the widespread development of swamping, and thermokarst contributes to the formation of shallow lakes. Forest-tundra is one of the most swampy natural zones. In contrast to the tundra, along with hypnum bogs, sphagnum bogs are widespread in it and peat bogs, sometimes of considerable thickness, begin to appear. The surface of peat bogs is uneven: small and large mounds alternate with wet hollows or small lakes.

) - zone forest-tundra. It forms a rather narrow strip (from 20 to 200 km) along the southern border of the tundra zone. Here, against the background of vegetation typical of the tundra, there are isolated trees and small islands of sparse forest.

Forest-tundra climate

It is much warmer in the forest-tundra than in the tundra. The annual precipitation reaches 400 mm, which is much higher than evaporation, and therefore the forest-tundra is characterized by severe swampiness.

Forests stretch along river valleys flowing from south to north, and are also represented by open forests in the interfluves. The flatness of the territory, warmer and longer summers with excess moisture determined the development of tundra-gley, podzolic, permafrost-taiga soils. These are poor soils, and to provide the tree with nutrients it is necessary large area. Therefore, the forests of watersheds are unique - they are sparse and individual oppressed trees are distant from each other.

Plants and animals of the forest-tundra

In the flora and fauna of the forest-tundra there are simultaneously tundra species of plants and animals, and forest ones.

Plants

Forest strips in the forest-tundra consist of low-growing curves birch trees, oils And larches, in the interfluves there are open forests and tundra shrubs. Harsh conditions, of course, are well tolerated by tundra plants, which are also forest-tundra plants: bushes ( blueberry, veronica), low-growing perennial grasses ( fescue squat), mosses and lichens ( reindeer moss, cuckoo flax).

In the forest-tundra zone Eastern Europe grows mainly from trees fluffy birch (Betulapubescens), and beyond the Urals - Siberian larch (Larixsibirica), Siberian spruce (Piceaobovata)(Fig. 139). The trees are low-growing, often with twisted trunks, covered with bearded lichens. Material from the site

Animals

The presence of sufficient food supply in the forest-tundra attracts adapted species animals both tundra and forests: moose, brown bears , squirrels, snowshoe hares, wolves, arctic foxes, lemmings, wood grouse And hazel grouse. Yes, wide hooves reindeer, convenient for shoveling snow, help them dig out reindeer moss. Developed hair protects against cold weather.

Forestumndra

On the Russian Plain, forest-tundra is included in tundra zone B western Siberia It is represented by an independent zone and in Central Siberia it is combined with the northern taiga and separated into a special zone of forest-tundra and northern woodlands.

Geographical location

The length of the zone from north to south is relatively small - from 20 to 200 km. Like the tundra zone, forest-tundra is located mainly north of the Arctic Circle

Climate

The climatic conditions of the forest-tundra are similar to the climate of the tundra zone. The most significant difference is that summer in the forest-tundra is warmer and longer than in the tundra. The average air temperature here in July reaches 11.0-14.0°. The sum of temperatures for a period with a stable temperature above 10°. This is the first, if you move from north to south, zone where meteorological summer is noticeably expressed - the time when the average daily air temperature rises above 15°.. On the contrary, in winter the forest-tundra is colder than in the tundra. The average air temperature in January ranges from -10 to -38°. The greater severity of winter is explained by the fact that the forest-tundra is located at some distance from the sea coast and lies in close proximity to the supercooled interior regions of Eurasia. For the same reason, wind speeds in the forest-tundra are somewhat lower than in the tundra, and the snow cover, due to the presence of forests, is more evenly distributed.

Permafrost occurs throughout the entire forest-tundra, but in the west of the zone it has an intermittent distribution. The zone is characterized by thermokarst processes associated with the presence of underground ice and heaving mounds (hydrolaccoliths).

The annual precipitation in the forest-tundra is 150-450 mm, which is much greater than the evaporation value. A positive moisture balance and permafrost contribute to the widespread development of waterlogging, and thermokarst contributes to the formation of shallow lakes. Forest-tundra is one of the most swampy natural zones. Unlike the tundra, swamps are widespread in it and peat bogs, sometimes of considerable thickness, begin to occur. The surface of peat bogs is uneven: small and large mounds alternate with wet hollows or small lakes.

On average, 350 - 400 mm of precipitation falls annually in the east, in the west - 500 - 600 mm, which gives excess moisture. Permafrost in the Eastern European tundra is discontinuous, while in the Siberian tundra it is continuous. Excessive moisture in combination with permafrost leads to intense waterlogging. Typical are hummocky peatlands with a peat layer thickness of 2 - 3 m (in the south - up to 5 m). A sharp maximum flow is observed in the spring, when the snow melts.

Soils

Thermokarst lakes in the Siberian forest-tundra are typical for forest-tundra and in some places occupy more than half of the area. The soils of the forest-tundra have much in common with the soils of both the tundra and the northern taiga. However, compared to the tundra, podzol and peat formation increases. The soil cover is variegated and heterogeneous.