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Description of the mixed forest - Mixed forests: characteristics and features of the natural zone, geographical location, climate and soils of mixed forests. Soil types

Mixed forests are a natural area where a mixture of coniferous and deciduous trees grows (with an admixture of more than 5% of plants of a different type). All life forms of vegetation occupy their ecological niches, forming a unique balance. A thicket with a diverse composition of trees is resistant to environmental influences, has a mosaic structure and a diverse flora and fauna. If a favorable combination of coniferous and deciduous species has formed in the forest stand, such a diversity of forests is more productive than a homogeneous one.

Characteristics and features of the natural zone of mixed forests.

There are coniferous-small-leaved and coniferous-broad-leaved forests. The former, growing in the taiga regions of Eurasia, are not durable. They precede the change from small-leaved groves to indigenous coniferous forests or broad-leaved oak forests. And coniferous-broad-leaved thickets are considered a sustainable natural formation. Such ecosystems develop cyclically, with a temporary predominance of conifers or a number of deciduous species. Depending on the climate, terrain, soil and hydrological regime, the composition of trees varies. Often there are spruce, pine, fir, oak, beech, linden, maple, ash, aspen, birch and other species in various combinations.

Mixed forests are formed in the temperate climate zone ( moderately continental climate ) with a clear change of seasons - relatively hot summers and cold winters. The average annual rainfall here usually reaches 600-700 mm. With insufficient evaporation, excessive moisture and waterlogging of the area is observed.

Coniferous-deciduous forests grow in North America (in most of Canada, in the north of the USA), in the western part of South America, Eurasia (Europe, Russia, Central Asia), Great Britain, in northern Japan. This natural zone in the south is replaced by forest-steppe or broadleaf forest, and to the north it turns into coniferous.

Under mixed forests with a predominant share of deciduous species, gray and brown forest soils. They are characterized by a higher content of humus than in podzolic taiga varieties. If the main ones are conifers, then soddy-podzolic soils of low fertility, with high acidity and excessive moisture, predominate.

In Russia, accurate accounting of the number mixed forests not conducted. On average, they account for up to half of the total area of the country's forest fund. They grow throughout Western Europe, reaching Eastern Europe, where they border on the taiga along a conditional line from St. Petersburg to Nizhny Novgorod. Further to the east, a narrow strip stretches to the Urals.

Characteristics and features of the natural zone of mixed forests.

See geographical position zones of mixed forests on the map of natural zones.

Mixed forests are formed in the temperate climate zone ( temperate continental climate) with a clear change of seasons - relatively hot summers and cold winters. The average annual rainfall here usually reaches 600-700 mm. With insufficient evaporation, excessive moisture and waterlogging of the area is observed.

Coniferous-deciduous forests grow in North America (in most of Canada, in the north of the USA), in the western part of South America, Eurasia (Europe, Russia, Central Asia), Great Britain, in the north of Japan. This natural zone in the south is replaced by forest-steppe or broad-leaved forest, and to the north it turns into coniferous.

Under mixed forests with a predominant share of deciduous species, gray and brown forest soils. They are characterized by a higher content of humus than in podzolic taiga varieties. If conifers are the main ones, then soddy-podzolic soils of low fertility, with high acidity and excessive moisture, predominate.

In Russia, accurate records of the number of mixed forests are not kept. On average, they account for up to half of the total area of the country's forest fund. They grow throughout Western Europe, reaching Eastern Europe, where they border on the taiga along a conditional line from St. Petersburg to Nizhny Novgorod. Further to the east, a narrow strip stretches to the Urals.

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A mixed forest is a territory in which deciduous and coniferous trees harmoniously coexist. If the admixture of tree species is more than 5% of the total volume of flora, we can already speak of a mixed type of forest.

The mixed forest forms a zone of coniferous-deciduous forests, and this is already a whole natural zone characteristic of forests in the temperate zone. There are also coniferous-small-leaved forests that are formed in the taiga as a result of the restoration of previously cut down pines or spruces, which begin to displace different types of birch and aspen.

Main characteristic

(Typical mixed forest)

Mixed forests almost always coexist with broad-leaved forests in the south. In the northern hemisphere, they also border the taiga.

There are the following types of mixed forests in the temperate zone:

coniferous-broad-leaved;
secondary small-leaved with the addition of coniferous and broad-leaved species;
mixed, which is a combination of deciduous and evergreen species.

Subtropical mixed fox is distinguished by a combination of laurel and coniferous species. Any mixed forest is distinguished by a pronounced layering, as well as the presence of areas without a forest: the so-called opolye and woodlands.

Location of zones

Mixed forests as a combination of coniferous and broad-leaved species are found in the East European and West Siberian plains, as well as in the Carpathians, the Caucasus and the Far East.

In general, both mixed and broad-leaved forests occupy a smaller share of the forest area. Russian Federation like coniferous taiga. The fact is that such ecosystems do not take root in Siberia. They are traditional only for the European and Far Eastern regions and at the same time grow in broken lines. Pure mixed forests are found south of the taiga, as well as beyond the Urals to the Amur region.

Climate

forest plantations mixed type characterized by cold, but not very long winters and hot summers. Climatic conditions are such that precipitation does not exceed 700 mm per year. The moisture coefficient is increased, but may change during the summer. In our country, mixed forests stand on soddy-podzolic soil, and in the west - on brown forest soil. As a rule, winter temperatures do not fall below -10˚C.

Broad-leaved forest plantations are distinguished by a humid and moderately humid climate, where precipitation is distributed evenly throughout the year. At the same time, temperatures are quite high, and even in January it is never colder than -8˚C. High humidity and abundant heat stimulate the work of bacteria and fungal organisms, due to which the leaves quickly decompose, and the soil retains maximum fertility.

Features of the plant world

Features of biochemical and biological processes cause the density of species diversity as you move towards broad-leaved species. European mixed forests are distinguished by the obligatory presence of pine, spruce, maple, oak, linden, ash, elm, and viburnum, hazel, honeysuckle are in the lead among shrubs. Ferns are very common as herbs. Caucasian mixed forests in large volumes contain beech, fir, and Far Eastern - birch, walnut, hornbeam, larch. These same forests are distinguished by a variety of lianas.

Fauna representatives

Mixed forests are inhabited by those animals and birds that are generally considered typical for forest conditions. These are moose, foxes, wolves, bears, wild boars, hedgehogs, hares, badgers. If we talk about individual broad-leaved forests, then here the species diversity of birds, rodents and ungulates is especially striking. Roe deer, fallow deer, deer, beavers, muskrats and nutrias are found in such forests.

Economic activity

The temperate natural zone, including mixed forests, has long been mastered by local residents and is densely populated. An impressive part of the forest plantations was cut down several centuries ago, because of which the composition of the forest has changed and the proportion of small-leaved species has increased. In place of many forests, agricultural territories and settlements appeared.

Broad-leaved forests can generally be considered rare forest ecosystems. After the 17th century, they were cut down on a large scale, largely because wood was needed for the sailing fleet. Broad-leaved forests were also actively cut down for arable land and meadows. Oak plantations have been especially hard hit by such human activities, and it is unlikely that they will ever be restored.

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mixed forests

Mixed forests are a natural zone of the temperate climate zone. The mixed forest usually borders in the south with a zone of deciduous forests. It is characteristic of the Northern Hemisphere and is found in the east of North America: the north of the USA - the south of Canada, as well as in Eurasia. Here, mixed forests stretch from the borders of Eastern Europe: Poland and Belarus to Western Siberia. Their northern border with the taiga roughly runs through St. Petersburg, Yaroslavl and Yekaterinburg. A mixed forest is much more adapted to cold climatic conditions than a broad-leaved one. Here the vegetation already withstands cold winters with average temperatures below -16°C and even frosts over -30°C. Summer here is quite warm with average values from +16 to +24°C. The annual rainfall is within 500 mm and decreases inland.

The vegetation of mixed forests, in addition to broad-leaved species: oak, maple, linden, poplar, is represented by small-leaved and coniferous trees, the percentage of which increases towards the north of the natural zone. Birch, alder, willow, mountain ash, spruce, and pine are common here. Most of the trees are deciduous, which is an adaptation to cold winters. temperate zone. At the same time, coniferous trees, with the exception of larch, remain green. all year round. The soils of mixed forests in the south are gray forest, in the north - soddy-podzolic, not very fertile, however, suitable for growing plants. The fauna of forests is represented by mammals. Moose, foxes, wolves, bears, wild boars, beavers, otters, lynx live here. Of the smaller ones: weasel, ferret, squirrel. Skunks, opossums, deer are also found in North America.

The mixed forest has been mastered by man, its vast areas have been reduced and now they are arable land and meadows. There are now few large massifs left, they are mostly crossed by transport highways, cut down and occupied by settlements.

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Mixed forests of Russia. Plants and animals of the mixed forest. Soils of mixed forests

Broad-leaved and mixed forests make up a much smaller percentage of Russia's forest zone than coniferous taiga. In Siberia, they are completely absent. Broad-leaved and mixed forests are typical for the European part and the Far East region of the Russian Federation. They are formed by deciduous and coniferous trees. They have not only a mixed composition of forest stands, but also differ in the diversity of the animal world, resistance to negative environmental influences, and mosaic structure.

Types and layering of mixed forests

There are coniferous-small-leaved and mixed-broad-leaved forests. The former grow mainly in continental regions. Mixed forests have a clearly visible layering (changes in the composition of the flora, depending on the height). The uppermost tier is tall spruces, pines, oaks. Somewhat lower grow birches, maples, elms, lindens, wild pears and apple trees, younger oak forests and others. Next come lower trees: mountain ash, viburnum, etc. The next tier is formed by shrubs: viburnum, hazel, hawthorn, rose hips, raspberries and many others. Next come the semi-shrubs. Grasses, lichens and mosses grow at the very bottom.

Intermediate and primary forms of coniferous-small-leaved forest

An interesting feature is that mixed-small-leaved massifs are considered only an intermediate stage in the formation of a coniferous forest. However, they are also indigenous: massifs of stone birch (Kamchatka), birch pegs in the forest-steppes, aspen bushes and swampy alder forests (south of the European part of the Russian Federation). Small-leaved forests are very light. This contributes to the lush growth of the grass cover and its diversity. Coniferous-mixed broad-leaved forest, on the contrary, belongs to stable natural formations. It is distributed in the transition zone between taiga and broad-leaved types. Coniferous-deciduous forests grow on the plains and on the lowest mountain belt with temperate and humid climatic conditions.

Zone of mixed and deciduous forests

Coniferous-deciduous forests grow in the warmer regions of the temperate zone. They are distinguished by the diversity and richness of the grass cover. They grow in intermittent stripes from the European part of the Russian Federation to the Far East. Their landscapes are favorable for people. To the south of the taiga is a zone of mixed forests. They are distributed throughout the entire area of the East European Plain, as well as beyond the Urals (up to the Amur region). They do not form a continuous zone.

The approximate border of the European section of broad-leaved and mixed forests in the north lies along 57 ° N. sh. Above it, the oak (one of the key trees) almost completely disappears. The southern one almost comes into contact with the northern border of the forest-steppes, where the spruce completely disappears. This zone is a triangular area with two vertices in Russia (Yekaterinburg, St. Petersburg) and the third one in Ukraine (Kyiv). That is, as the distance from the main zone to the north, broad-leaved, as well as mixed forests gradually leave the watershed spaces. They prefer river valleys that are warmer and protected from icy winds with access to the surface of carbonate rocks. On them, forests of broad-leaved and mixed types gradually reach the taiga in small massifs.

The East European Plain is mostly low-lying and flat, with only occasional elevations. Here are the sources, basins and watersheds of the largest Russian rivers: Dnieper, Volga, Western Dvina. On their floodplains, meadows are interspersed with forests and arable lands. In some regions, the lowlands, due to the proximity of groundwater, as well as the limited flow, are extremely swampy in places. There are also areas with sandy soils on which pine forests grow. Berry bushes and herbs grow in swamps and clearings. This area is the most suitable for coniferous-deciduous forests.

Human influence

Broad-leaved, as well as mixed forests, are subject to various influences from people for a long time. Therefore, many massifs have changed a lot: the native vegetation has either been completely destroyed, or partially or completely replaced by secondary rocks. Now the remains of broad-leaved forests, which have survived under severe anthropogenic pressure, have a different structure of flora changes. Some species, having lost their place in indigenous communities, grow in anthropogenically disturbed habitats or have taken up intrazonal positions.

Climate

The climate of mixed forests is quite mild. It is characterized by relatively warm winters (on average from 0 to –16°C) and long summers (16–24°C) compared to the taiga zone. The average annual rainfall is 500-1000 mm. It exceeds evaporation everywhere, which is a feature of a pronounced flushing water regime. Mixed forests have such a characteristic feature as a high level of grass cover development. Their biomass averages 2-3 thousand c/ha. The level of litter also exceeds the biomass of the taiga, however, due to the higher activity of microorganisms, the destruction of organic matter is much faster. Therefore, mixed forests are thinner and have a higher level of litter decomposition than taiga coniferous forests.

Soils of mixed forests

The soils of mixed forests are diverse. The cover has a rather variegated structure. On the territory of the East European Plain, the most common type is soddy-podzolic soil. It is a southern variety of classical podzolic soils and is formed only in the presence of loamy soil-forming rocks. The soddy-podzolic soil has the same profile structure and a similar structure. It differs from the podzolic one in the lower massiveness of the litter (up to 5 cm), as well as in the greater thickness of all horizons. And these are not the only differences. Soddy-podzolic soils have a more pronounced humus horizon A1, which is located under the litter. Appearance it differs from a similar layer of podzolic soils. The upper part contains the rhizomes of the grass cover and forms the turf. The horizon can be colored in various shades of gray and has a loose structure. The layer thickness is 5-20 cm, the proportion of humus is up to 4%. The upper part of the profile of these soils has an acidic reaction. As it deepens, it becomes even smaller.

Soils of mixed broad-leaved forests

Gray forest soils of mixed-deciduous forests are formed in inland regions. In Russia, they are distributed from the European part to Transbaikalia. In such soils, precipitation penetrates to a great depth. However, groundwater horizons are often very deep. Therefore, wetting of the soil to their level is typical only in highly humid areas.

The soils of mixed forests are better suited for farming than those of taiga. In the southern regions of the European part of the Russian Federation, arable land makes up to 45% of the area. Closer to the north and taiga, the share of arable land gradually decreases. Agriculture in these regions is difficult due to the strong leaching, waterlogging and bouldering of soils. To receive good harvests requires a lot of fertilizer.

General characteristics of fauna and flora

The plants and animals of the mixed forest are very diverse. In terms of species richness of flora and fauna, they are comparable only with tropical jungle and are home to many carnivores and herbivores. Here, squirrels and other living creatures settle on high trees, birds make nests on the crowns, hares and foxes equip holes at the roots, and beavers live near the rivers. The species diversity of the mixed zone is very high. Both the inhabitants of the taiga and broad-leaved forests, and the inhabitants of the forest-steppes feel comfortable here. Some are awake all year round, while others hibernate for the winter. The plants and animals of the mixed forest have a symbiotic relationship. Many herbivores feed on various berries, which are abundant in mixed forests.

mixed forest trees

Mixed-small-leaved forests are approximately 90% composed of coniferous and small-leaved tree species. There are not many broad-leaved varieties. Together with coniferous trees, aspens, birches, alders, willows, and poplars grow in them. Bereznyakov as a part of massifs of this type most. As a rule, they are secondary - that is, they grow in forest fires, clearings and clearings, old unused arable lands. In open habitats, such forests regenerate well and grow rapidly in the first years. Human economic activity contributes to the expansion of their areas.

Coniferous-broad-leaved forests mainly consist of spruces, lindens, pines, oaks, elms, elms, maples, and in the southwestern regions of the Russian Federation - beech, ash and hornbeam. The same trees, but of local varieties, grow in the Far East region along with grapes, Manchurian walnuts and lianas. In many ways, the composition and structure of the forest stand of coniferous-broad-leaved forests depends on climatic conditions, relief and soil-hydrological regime of a particular region. Oak, spruce, maple, fir and other species predominate in the North Caucasus. But the most diverse in composition are Far Eastern forests coniferous-broad-leaved type. They are formed by cedar pine, white fir, Ayan spruce, several varieties of maple, Manchurian ash, Mongolian oak, Amur linden and the aforementioned local species of vegetation.

Species diversity of the animal world

Of the large herbivores, moose, bison, wild boars, roe deer and spotted deer (the species has been introduced and adapted) live in mixed forests. Of the rodents, there are forest squirrels, martens, ermines, beavers, chipmunks, otters, mice, badgers, minks, black ferrets. Mixed forests abound in a large number of bird species. Many of them are listed below, but not all of them: oriole, nuthatch, siskin, field thrush, goshawk, hazel grouse, bullfinch, nightingale, cuckoo, hoopoe, gray crane, goldfinch, woodpecker, black grouse, chaffinch. More or less large predators are represented by wolves, lynxes and foxes. The mixed forests are also home to hares (hare and hare), lizards, hedgehogs, snakes, frogs and brown bears.

Mushrooms and berries

The berries are represented by blueberries, raspberries, lingonberries, cranberries, blackberries, bird cherry, wild strawberries, stone berries, elderberries, mountain ash, viburnum, dogrose, hawthorn. In the forests of this type there are a lot of edible mushrooms: boletus, porcini, valui, chanterelles, russula, mushrooms, milk mushrooms, boletus, volnushki, various rows, boletus, moss mushrooms, mushrooms and others. One of the most dangerous poisonous macromycetes are fly agarics and pale grebes.

shrubs

The mixed forests of Russia abound in shrubs. The understory layer is unusually developed. Oak massifs are characterized by the presence of hazel, euonymus, wolf's bast, forest honeysuckle, and in the northern zone - brittle buckthorn. Rose hips grow on the edges and in light forests. In the forests of the coniferous-broad-leaved type, liana-like plants are also found: new fence, climbing hops, bittersweet nightshade.

Herbs

Mixed forest grasses (especially coniferous-broad-leaved type) have a large species diversity, as well as a complex vertical structure. The most typical and widely represented category is mesophilic nemoral plants. Among them, representatives of oak broad grass stand out. These are plants in which the leaf plate has a significant width. These include: perennial forestry, common gout, obscure lungwort, May lily of the valley, European hoof, hairy sedge, yellow greenfinch, lanceolate stellate, nomad (black and spring), amazing violet. Cereals are represented by oak bluegrass, giant fescue, forest reed grass, short-legged feathery, spreading pine forest and some others. The flat leaves of these plants are a variant of adaptation to the specific phytoenvironment of coniferous-deciduous forests.

In addition to the above perennial species, these massifs also contain herbs of the ephemeroid group. They transfer their growing season to spring time, when the lighting is maximum. After the snow melts, it is the ephemeroids that form a beautifully blooming carpet of yellow anemones and goose onions, purple corydalis and lilac-bluish woods. These plants go through a life cycle in a couple of weeks, and when the leaves of the trees bloom, their aerial part dies off over time. They experience an unfavorable period under a layer of soil in the form of tubers, bulbs and rhizomes.

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coniferous, mixed, broad-leaved and small-leaved

Forests make up slightly more than 45% of the area of Russia, and almost a quarter of the total forest area of the world. In the European part of the country, there are much fewer of them than in the Asian. The most common forest-forming tree species are spruce, larch, pine, cedar, oak, maple and hornbeam. Many berry bushes, mushrooms, valuable herbs grow in the forests, as well as countless species of fauna. Deforestation leads to the reduction of forest areas and the threat of extinction of many animals. In the 21st century, it is very important to be able to reproduce forest resources, which play one of the main roles in climate regulation on the planet.

Forest cover map of Russia in %

Russia is the largest country in the world, and for this reason, many natural zones are located on its territory in which different kinds trees. The forests of Russia, depending on the predominance of certain tree species, are divided into four main types: 1) coniferous forests; 2) deciduous forests; 3) mixed forests; 4) small-leaved forests. We'll look at each of these forest types in more detail below.

Characteristics of coniferous forests in Russia

Coniferous forests are located on the territory of the natural zone of the taiga, and occupy about 70% of the total forest area of the country. This zone is known for low temperatures and humid air. Coniferous forests stretch from the western borders of Russia to the Verkhoyansk Range. The main forest-forming species are spruce, pine, fir and larch.

In severe winter conditions, mixed forests are most often found: dark coniferous and light coniferous. Evergreen tree species thrive well. Photosynthesis in them begins in the spring with the onset of favorable weather conditions. Undergrowth is practically absent in the taiga. There is podzolic soil and many swamps. Conifers shed needles, which, when decomposed, release compounds toxic to many plants into the ground. The ground is covered, as a rule, by mosses and lichens. Shrubs and flowers mainly grow along the banks of the rivers, there are very few of them in the dark places of the forest. There is lingonberry, juniper, mountain ash, blueberry and curly lily.

It is the weather conditions that determine the flora of Russia. The temperate continental climate prevails in the zone of coniferous forests. Winters are dry and cold, lasting an average of six months. Short summers are warm and humid, with numerous cyclones. For autumn and spring, as a rule, only one month is allotted. Conifers are not demanding on temperature extremes.

Representatives of the animal world feed on moss, lichens, bark and cones. The high forest crown protects the animals from the winds, and the branches make it possible to build nests. Typical representatives of the fauna of coniferous forests are vole, hare, Siberian weasel, chipmunk. Of the large mammals, the Siberian tiger, brown bear, lynx and elk can be noted, and from the forest-tundra zone comes to coniferous forests reindeer. Eagles and vultures soar in the sky.

Coniferous wood is considered one of the most valuable. Its approximate reserve is 5.8 billion cubic meters. In addition to logging, oil, gold and gas production is carried out in the taiga. The coniferous forests of Russia are a huge forest area. It suffers from forest fires and uncontrolled logging. Due to negative human activities, rare animals die. There are many reserves, but for the full restoration of forests, it is necessary to properly organize protection and rationally use the country's forest resources.

Characteristics of broad-leaved forests in Russia

Broadleaf forest/Wikipedia

The territory of deciduous forests extends from the western border of Russia to the Ural Mountains. The main tree species are beech, oak, elm, linden, maple and hornbeam. The forests are multi-tiered: the upper tier is replaced by canopy and undergrowth, which, in turn, are herbaceous plants and forest litter. The soil is covered with mosses. There are areas in which lush crowns completely exclude undergrowth. Foliage, falling off, decomposes and forms humus. The soil in the undergrowth is rich in organomineral compounds.

Forests are located in the temperate continental zone. The weather here is much warmer than in the neighboring taiga. Summer lasts four months, the average temperature per season is +10°C. This contributes to the growth of broad-leaved tree species. The climate is humid and there is a lot of precipitation. Average monthly temperature in January it drops to -16ºС. The maximum precipitation falls in summer, there is no deep snow cover.

The leaves cannot survive the cold period of the year, and fall off in mid-autumn. A dense cover of foliage, twigs, and bark protects the ground from excessive evaporation. The soil is rich in trace elements, it provides the trees with everything they need. The foliage that has fallen for the winter covers the root system, protects it from the cold and stimulates the roots to further growth.

The composition of the animal world in the European part is somewhat different from the Far Eastern forests. Asian lands cover thickets of fern, ilmen and linden. The dense thickets are inhabited by elk, Himalayan bear and Ussurian tiger. Cotton muzzle, viper and Amur snake are common reptiles. European broadleaf forests have become home to wild boar, elk, deer, wolf, weasel, beaver, muskrat and nutria. Mice, lizards, snakes, moles and hedgehogs also live there. Birds are represented by black grouse, owls, owls, starlings, swallows and larks.

The zone of deciduous forests has long been mastered by man, especially in the west of Russia. People had to significantly reduce the green area for the sake of grazing, crop production and building cities. Trees are the main raw material for the logging industry. Processing of secondary raw materials has been established. The subsoil is rich in minerals, and in large rivers there is potential for the development of hydroelectric power.

The forest area is significantly reduced, while forests are cut down on the same scale. Because of anthropogenic influence Red Book plants and animals are dying out. Unscrupulous entrepreneurs cut down huge areas of forests. To preserve natural complexes, several reserves and national parks were created, but this is not enough. Broad-leaved tree species grow relatively quickly. It is necessary to organize the planting of seedlings on the territory of cut forests, as well as carefully use the remaining forest areas.

Characteristics of mixed forests in Russia

Mixed forests are located in the Russian Plain, West Siberian Plain, Amur and Primorye. A variety of tree species are found in this zone. These forests are characterized by pronounced layering. Poplars, pines and firs stretch towards the light. Below them rise maples, elms, lindens and oaks. The tier of shrubs is represented by hawthorn, wild rose, raspberry and blackberry. The soil is covered with lichens, mosses and low grasses.

Trees of mixed forests are easier to tolerate the severity of the climate than in neighboring broad-leaved ones. The vegetation withstands frosts down to -30ºС. The amount of precipitation depends on the region. There is more snow in European forests than in the Far East. The maximum amount of precipitation falls on the warm season. Summers are mild and humid. The climate changes from maritime to continental, from west to east.

The continuous renewal of green mass contributes to the nourishment of trees and the cleansing of the earth from unnecessary substances. The inhabitants of the forest use the resources of all tiers as forage base. Coniferous seeds attract birds, rodents eat nuts, larvae under the bark are food for insectivorous birds.

Numerous once animals were exterminated as a result of uncontrolled hunting. You can also meet roe deer and wild boar. Bison and red deer are preserved only in nature reserves. A well-known predator of the mixed forest is the common fox. The badger lives in the European part. Squirrel, mink, dormouse, marten, forest cat, brown bear are considered common representatives of the fauna of mixed forests. The world of birds is also diverse, especially a lot of woodpeckers, capercaillie, wild pigeons, finches and robins.

Stocks of valuable timber are located in the Asian part. Manchurian walnut, Korean cedar, whole-leaved fir are famous for their strength and resistance to decay. Eleutherococcus and lemongrass are used for medical purposes. On the territory of Europe, logging activities are carried out.

Mixed forests have suffered more than others at the hands of man. This has led to a number of environmental problems. The need for agricultural land has led to the deforestation of a significant part of the territories. The ecosystem has changed due to the drainage of swamps. The growth of settlements, especially in the west, has led to a 30% reduction in forest cover.

The foliage of trees perfectly processes carbon dioxide. Deforestation, which has reached gigantic proportions, has destroyed millions of hectares. Because of this, harmful gases accumulate in the atmosphere, creating a greenhouse effect. Hundreds of animal species and flora disappears from the face of the earth. Through the fault of people, forest fires occur, radically changing the ecosystem. On the rare species animals are hunted illegally. Resources are almost depleted, only the interaction of the state and citizens can stop the process of destruction of the country's mixed forests.

Characteristics of small-leaved forests in Russia

The zone of small-leaved forests extends from the East European Plain to the Far East. Forests stretch in a narrow strip, sometimes replacing broad-leaved ones. finely deciduous trees play the role of a second forest, replacing broad-leaved and coniferous species.

The main forest-forming species are birch, alder and aspen. Their foliage is distinguished by a narrow leaf plate. Trees are undemanding to climate and soil quality. Birch forests are the most widespread.

Often trees grow on the site of fires or felling. Alder reproduces by shoots, and aspen - by root offspring. Where there were no forests, trees grow by seed. An amazing feature is the ability to accumulate moisture. Thickets of alder and birch block the way to fire, do not allow spreading to noble species.

The animal world is formed under the influence of indigenous trees. A lot of birds. Of the mammals, there are hares, lynxes, moose and squirrels. Strips of small-leaved forests alternating with economic lands are favorite places for raccoon dogs.

Secondary forests contribute to the restoration of green areas, although it takes about 180 years for full rehabilitation. They act as a fire buffer. It remains to be hoped that small-leaved forests will contribute to the reorganization of the country's forest resources.

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Mixed and broad-leaved forests of Russia

Mixed forests differ from other species in that different tree species can be found on their territory. For example, not only deciduous, but also coniferous forests grow here. While broad-leaved forest areas consist mainly of certain species.

The climatic conditions in these areas are characterized by moderate temperatures and are quite acceptable for the growth of various tree species.

Features of mixed forests in Russia

It is the richest forest in natural resources, found in only a few countries. For our state, the development and cultivation of species growing in such forests is an important component of the successful development of the entire industry of the country.

Mixed forests are considered as such and belong to this species only when the admixture of two varieties of tree species: deciduous and coniferous is about 5% of the total volume of the forest.

In the territories of our country, where mixed forests grow, it is generally warm enough and there is no prolonged precipitation. Summer here is not characterized by abnormal heat and sudden changes in temperature conditions. While in winter there will be no heavy snowfalls or natural disasters associated with sharp drops in temperatures.

Mixed forests are characterized by:

temperate climate,
the presence of an optimal moisture coefficient,
the growth of a wide variety of trees within the same forest area.

Closer to the south of the natural zone where mixed forests grow, there are massifs in which broad-leaved tree species predominate. After all, most of the north is occupied by taiga. The climatic conditions of these territories allow only the most “hardy” tree species to grow here.

The soils of mixed forests are particularly fertile. The constant renewal of nature contributes to their nourishment and cleansing the earth of unnecessary substances. For example, soil that has already been cultivated by man needs to be updated. It will take several years for the forest area to be able to expand its volumes again.

If we consider mixed forests from the point of view of the history of their appearance, then in the past they were present in large areas. However, due to human activities and the development of urban infrastructure, forest areas have significantly reduced their volumes.

Despite the fact that our country has huge advantages in terms of the development of the forest industry, every year the areas of mixed forests and other varieties of these natural resources are significantly reduced.

This leads to natural disasters, after all, only durable root system trees can hold back strong winds and prevent floods. Mixed forests are a whole complex of all kinds of natural elements and resources combined in one area.

Only these massifs create a special natural zone, represented by coniferous-deciduous forests. There are only a few places in the world whose climate allows such a variety of trees to be collected in one area. At the same time, so that they can peacefully coexist with each other, in fact, in the same climatic zone.

But it is allowed to produce timber on these lands only after receiving the relevant documents, approved in the first place by the state. Such natural areas, on which forests grow, are considered the property of the state. These laws have been passed to:

reduce unauthorized cutting of trees,
allow mixed forests to freely expand their territories,
take care of improving the environmental situation in Russia by increasing the volume of forests.

The areas of coniferous forests have recently been significantly reduced. But the situation is saved by coniferous-small-leaved forests. They allow these natural areas to quickly restore their natural potential. This is due to the growth on the site of already cut down trees, the so-called young forests.

They reduce the stages of transition of the forest damaged by clearings to the full restoration of the forest. In fact, birch and pine trees grow on the site of cut down pine and spruce species, which are the most demanded natural resources in the forest industry.

The mixed forests of Europe, as well as the forests prevailing in our country, are practically in the same natural zone. Therefore, the main species that form forests belonging to this variety are: spruce and oak. It is rare in our time to find an array where, among all tree species, ash or maple stands out the most.

After the man began to develop these lands, most of the breeds simply disappeared from these places. For their complete restoration, years are needed and the organization of work on planting the required number of seedlings, which will become the basis for the future forest.

Nature is unique, because it is able to create such diverse forests. They differ from each other not only in the shape of the leaves, but also in a whole complex of various characteristics. Mixed forests cannot be formed by human efforts and properly planted trees.

To artificially create a similar ecosystem functioning at the expense of own resources and being completely autonomous is almost impossible. Therefore, a person has no choice but to preserve the wealth already existing in our country.

It is possible to create forests artificially for only one purpose - further felling and harvesting of already processed natural material. Sometimes trees are planted to purify water in nearby rivers or to create an additional natural "filter" to purify the air.

Such synthetically created forests lend themselves well to cutting down, and their potential can be restored by planting new seedlings. Thus, nature has time to replenish the volume of forest resources that has already been developed in the forest.

Mixed forests are very difficult to grow in artificial conditions. That is, if you just randomly plant a few trees in the territory you need for subsequent felling, only some species will be able to fully grow.

After all, in fact, a mixed forest is a unique system that has existed for several hundred years, created by nature, taking into account:

the climate of our country,
hardiness of trees that constantly grew in the same area,
the existence of a certain forest area that protects young trees from strong winds and other climatic influences.

In addition, it makes no sense to wait until the newly planted seedlings grow. The technologies that ensure their landing are partially used. For example, new, young trees or seedlings are planted in an already developed area. At the same time, the species of these trees should already grow in this mixed forest.

Broad-leaved forests of Russia

Despite the fact that these forests are found in our country more often than mixed forests, the volume of their arrays is significantly reduced. A forest can be attributed to a broad-leaved species only if several varieties of trees with deciduous and wide leaf blades grow in it. For comparison, in mixed forests, in addition to deciduous trees, coniferous trees grow, with needles in place of leaves. In fact, these needles replace leaves for trees.

For the formation of these forests, a moderate type of climate and good humidity are needed. Abrupt changes in temperature and harsh winters can sometimes be tolerated by broad-leaved forests. However, for their full development, they need a more “calm” climate.

That is, in order to go through one cycle of its life, first buds grow on a tree, then leaves, flowers appear, and only then fruits. Leaves in autumn period years fall, allowing the tree to prepare for the winter period. Surprisingly, the leaves become fertilizer and additional insulation for the winter for the same species on which it once grew. When winter comes, all processes in the trees stop, they fall into a state similar to sleep.

If we consider mixed forests, then conifers are more active in winter, as they are able to endure even the most severe climatic conditions. Therefore, different types of trees are combined in mixed forests.

Broad-leaved forest types are present mainly in the south of Chile, America and a number of other countries, the climatic zones of which are similar in their weather conditions and temperature regime.

The soils here are rich in useful minerals and fertilizers. Often in broad-leaved forests there are chernozems and podzolic soils. But sometimes there are also gray, brown forest and other varieties most characteristic of deciduous trees.

Leaves, as mentioned above, are an additional and almost universal nutrient for trees. They contain all the substances necessary for these breeds, allowing them to accelerate their growth or slow it down if climatic conditions have changed.

Winter in deciduous forests is quite mild, sudden changes in the climatic picture of the natural zone is not observed. If we compare them with mixed ones, the climate of which varies depending on the natural zone, then deciduous trees like climatically moderate winters and warm summers. Only in the summer periods of the year can a tree recover its strength after a winter sleep and fully grow.

Due to such temperate climate and the absence of strong humidity, the level of waterlogging for these places is reduced. Therefore, there are practically no swamps here. But they take place in those natural zones, the climate of which is already closer to mixed forests and taiga regions, where the humidity is much higher.

The most common are forests, the main trees in which are: linden, hornbeam or oak. But you can also meet maple.

Our country is rich in various types of forests, while in America there are only a few species of trees. In the past, this country was proud of oak and chestnut forests. They have practically disappeared from our planet and are present in insignificant clusters of trees.

In this regard, Russia has more opportunities to create the formation of various forests. It all depends on:

nature,
human activity,
the speed of urban infrastructure development, which is the main reason for the deforestation of most forest areas in Russia.

wood-prom.ru

Mixed and broad-leaved forests | Geography Grade 6

mixed forests- natural zone of the temperate zone, transitional from the taiga zone to the zone of broad-leaved forests. Mixed forests form in a fairly humid climate, are common in oceanic and transitional climatic areas continents in Europe, North America, South America, New Zealand, Tasmania.

This zone of mixed forests is characterized by a climate with moderately cold, snowy winters (t°average January from -5 to -14°С) and warm summers (t°average July up to +20°С). The amount of precipitation (400-800 mm per year) slightly exceeds evaporation.
Forests are coniferous-broad-leaved, and in more continental areas - coniferous-small-leaved, mainly on soddy-podzolic soils. Coniferous species are dominated by: spruce, pine, fir; from small-leaved species stand out: birch, aspen; from broad-leaved: oak, maple, linden, ash. Increase in share in species composition broad-leaved species occurs in the direction of removal from the poles and with an increase in climate humidity.
The animal world consists of both taiga species and species living in broad-leaved forests: hare, lynx, elk, fox, squirrel, wild boar, capercaillie, black grouse, etc.

The territory of the zone of mixed forests is one of the most economically developed. There is a high population density, there are a large number of large cities. This has led to the fact that the natural vegetation of the zone has been preserved only in small areas, and most of the territory is occupied by cities, agricultural lands, etc.

broadleaf forests- a natural zone of the temperate zone, formed in the humid climate of the oceanic territories of the continents. The main areas of deciduous forests are common in Europe and North America, where they are sometimes distinguished as the southern part of a single zone of temperate forests; small patches of deciduous forests exist in South America.
This zone is characterized by a maritime and temperate continental climate with moderately cold winters (average January temperature from -5 to -15 °С) and rather long warm summers (average July temperature up to +22 °С). The amount of precipitation (600-1500 mm per year) is approximately equal to or slightly greater than evaporation.

The vegetation is dominated by trees with broad leaves that fall in winter. Dominant species: oak, beech, maple, ash, linden, hornbeam, chestnut and other trees that give significant shading, a dense grass cover is characteristic. Under deciduous forests, brown forest and gray forest soils are common.
In Europe, broad-leaved forests occupied the largest area. Here the most common tree is oak (petiolate, rocky and other species). In North America, broadleaf forests are prominent southeast of the Great Lakes. In South America, the zone is represented by southern beech forests in southern Chile.
Among the inhabitants of the zone there are ungulates and predators; of mammals, characteristic species are mink, black polecat, European wild cat, dormice, bison, etc. Of birds - green woodpecker, cuckoo, woodcock, pheasant.

Favorable climate and soil fertility led to active settlement and development of this natural zone, expansion of arable land and deforestation, so the place of natural vegetation in most of the broad-leaved forests was occupied by anthropogenic complexes.

Types and layering of mixed forests

Intermediate and primary forms of coniferous-small-leaved forest

An interesting feature is that mixed-small-leaved massifs are considered only an intermediate stage in the formation of a coniferous forest. However, they are also indigenous: massifs of stone birch (Kamchatka), birch pegs in the forest-steppes, aspen bushes and swampy alder forests (south of the European part of the Russian Federation). Small-leaved forests are very light. This contributes to the lush growth of the grass cover and its diversity. broad-leaved type, on the contrary, refers to stable natural formations. It is distributed in the transition zone between taiga and broad-leaved types. grow on the plains and on the lowest mountain belt with temperate and humid climatic conditions.

The approximate border of the European section of broad-leaved and mixed forests in the north lies along 57 ° N. sh. Above it, the oak (one of the key trees) almost completely disappears. The southern one almost comes into contact with the northern border of the forest-steppes, where the spruce completely disappears. This zone is a section in the form of a triangle, two peaks of which are in Russia (Ekaterinburg, St. Petersburg), and the third - in Ukraine (Kyiv). That is, as the distance from the main zone to the north, broad-leaved, as well as mixed forests gradually leave the watershed spaces. They prefer river valleys that are warmer and protected from icy winds with access to the surface of carbonate rocks. On them, forests of broad-leaved and mixed types gradually reach the taiga in small massifs.

The East European Plain is mostly low-lying and flat, with only occasional elevations. Here are the sources, basins and watersheds of the largest Russian rivers: the Dnieper, the Volga, the Western Dvina. On their floodplains, meadows are interspersed with forests and arable lands. In some regions, the lowlands, due to the proximity of groundwater, as well as the limited flow, are extremely swampy in places. There are also areas with sandy soils on which pine forests grow. Berry bushes and herbs grow in swamps and clearings. This area is the most suitable for coniferous-deciduous forests.

Human influence

Climate

The climate of mixed forests is quite mild. It is characterized by relatively warm winters (on average from 0 to -16°C) and long summers (16-24°C) compared to the taiga zone. The average annual rainfall is 500-1000 mm. It exceeds evaporation everywhere, which is a feature of the pronounced leaching water regime. Mixed forests have such a characteristic feature as a high level of grass cover development. Their biomass averages 2-3 thousand c/ha. The level of litter also exceeds the biomass of the taiga, however, due to the higher activity of microorganisms, the destruction of organic matter is much faster. Therefore, mixed forests are thinner and have a higher level of litter decomposition than taiga coniferous forests.

Soils of mixed forests

The soils of mixed forests are diverse. The cover has a rather variegated structure. On the territory of the East European Plain, the most common type is soddy-podzolic soil. It is a southern variety of classical podzolic soils and is formed only in the presence of loamy soil-forming rocks. The soddy-podzolic soil has the same profile structure and a similar structure. It differs from the podzolic one in the lower massiveness of the litter (up to 5 cm), as well as in the greater thickness of all horizons. And these are not the only differences. Soddy-podzolic soils have a more pronounced humus horizon A1, which is located under the litter. Its appearance differs from the similar layer of podzolic soils. The upper part contains the rhizomes of the grass cover and forms the turf. The horizon can be colored in various shades of gray and has a loose structure. The layer thickness is 5-20 cm, the proportion of humus is up to 4%. The upper part of the profile of these soils has an acidic reaction. As it deepens, it becomes even smaller.

Soils of mixed broad-leaved forests

General characteristics of fauna and flora

The plants and animals of the mixed forest are very diverse. In terms of species richness of flora and fauna, they are comparable only to the tropical jungle and are home to many predators and herbivores. Here, squirrels and other living creatures settle on high trees, birds make nests on the crowns, hares and foxes equip holes at the roots, and beavers live near the rivers. The species diversity of the mixed zone is very high. Both the inhabitants of the taiga and broad-leaved forests, and the inhabitants of the forest-steppes feel comfortable here. Some are awake all year round, while others hibernate for the winter. Plants and have a symbiotic relationship. Many herbivores feed on various berries, which are abundant in mixed forests.

Mixed-small-leaved forests are approximately 90% composed of coniferous and small-leaved tree species. There are not many broad-leaved varieties. Together with coniferous trees, aspens, birches, alders, willows, and poplars grow in them. There are the most birch forests in the massifs of this type. As a rule, they are secondary - that is, they grow in forest fires, clearings and clearings, old unused arable lands. In open habitats, such forests regenerate well and in the first years, the expansion of their areas is facilitated by

Coniferous-broad-leaved forests mainly consist of spruces, lindens, pines, oaks, elms, elms, maples, and in the southwestern regions of the Russian Federation - beech, ash and hornbeam. The same trees, but of local varieties, grow in the Far East region along with grapes and lianas. In many respects, the composition and structure of the forest stand of coniferous-broad-leaved forests depends on climatic conditions, topography, and the soil-hydrological regime of a particular region. Oak, spruce, maple, fir and other species predominate in the North Caucasus. But the most diverse in composition are the Far Eastern forests of the coniferous-broad-leaved type. They are formed by cedar pine, white fir, Ayan spruce, several Manchurian ash, Mongolian oak, Amur linden and the above-mentioned local vegetation species.

Species diversity of the animal world

Mushrooms and berries

shrubs

The mixed forests of Russia abound in shrubs. The understory layer is unusually developed. Oak massifs are characterized by the presence of hazel, euonymus, forest honeysuckle, and in the northern zone - brittle buckthorn. Rose hips grow on the edges and in light forests. In the forests of the coniferous-broad-leaved type, liana-like plants are also found: new fence, climbing hops, bittersweet nightshade.

Herbs

Mixed forest grasses (especially coniferous-broad-leaved type) have a large species diversity, as well as a complex vertical structure. The most typical and widely represented category is the mesophilic nemoral plants. Among them, representatives of oak broad grass stand out. These are plants in which the leaf plate has a significant width. These include: perennial forestry, common gout, obscure lungwort, May lily of the valley, hairy sedge, yellow greenfinch, lanceolate chickweed, nomad (black and spring), amazing violet. Cereals are represented by oak bluegrass, giant fescue, forest reed grass, short-legged feathery, spreading pine forest and some others. The flat leaves of these plants are a variant of adaptation to the specific phytoenvironment of coniferous-deciduous forests.

The annual sum of temperatures over 10 °C ranges from 2200-4000°, the duration of the growing season is from 130-210 days. In winter, the soil freezes for a period of several days to 4-5 months. Soil formation proceeds on siallitic carbonate and carbonate-free weathering crusts. Horizontal zonality and faciality are well expressed in the distribution of soils.

Within the subboreal zone, deciduous forests with a rich ground cover are widespread. Some formed in a mild oceanic climate, others - in inland regions. The landscapes of these forests have been greatly altered by man, the vegetation has either been completely destroyed or replaced by a secondary one.

Gray forest soils are formed in inland regions, from Belarus to Baikal. To the east, the severity and dryness of the climate is growing, the average annual temperatures vary from +7 in the west to -5 in the east, the duration of the frost-free period - from 250 to 180 days, precipitation - from 600 to 300 mm.

The dominant vegetation is deciduous herbaceous forests, in the west hornbeam-oak, between the Dnieper and Volga - linden-oak with an admixture of ash, in Western Siberia - birch-aspen, and even to the east larch appears. The weight of the litter is 7-9 t/ha, which is much more than in the taiga. The litter is rich in ash elements, especially calcium, which reaches up to 100 kg/ha.

The soil-forming rocks are usually covering loess-like loams, often carbonate. Gray forest soils have a thick (20-30 cm) humus horizon A1 with a cloddy structure, under which lies a less thick A2 (A1A2) of gray color and a leafy-lamellar structure, replaced by a powerful brown-brown intrusion horizon B (up to 100 cm).

Three subtypes are distinguished: light gray, gray, dark gray, and dark gray soils do not have an A2 horizon. The clear differentiation of the soil profile is due to intensive processes of lessivage. The content of silt in the mountains. B is twice as high as in layer A. The humus content is 3-7%, part of the litter is concentrated in the forest litter. There is so much calcium in the litter that it often does not have time to be washed out, forming neoplasms of wavellite (calcium oxalate). In gray forest soils, humus dominates, transitional from coarse to mull. The reaction is slightly acidic, in A1 it is close to neutral. In them, the upper horizons are depleted in the clay fraction compared to the rock, enriched in SiO2 and depleted in sesquioxides, which is due to the processes of podzolization and lessivage. However, the content of humus in them is high, it varies from 2 to 12%.

Features of the genesis clearly reflect their physico-chemical properties. Light gray forest soils are acidic, base saturation is about 70%, CEC in loamy soils is about 14-16 in the humus horizon and increases in the illuvial to 90 meq/100 g of soil. Physical and physico-mechanical properties depend on the degree of humus content and particle size distribution. Dark gray soils have the best properties, which differ from other subtypes by their high humus content and well-defined water-resistant structure. They are less favorable in light gray soils, which are characterized by low moisture capacity and water permeability, easily swim and form a crust.

There are serious provincial peculiarities. In Ukraine, they have a very powerful A1 (up to 50 cm), in the Cis-Urals the power is less, but the humus content is higher.

For a long time, the origin of gray forest soils was explained either by the degradation of chernozems when the forest invaded the steppe, or by the progradation of forest soils (according to Williams) when the steppe invaded the forest.

Gray forest soils are zonal soils of the forest-steppe, in which treeless spaces alternate with forests, gray soils - with typical northern and podzolized chernozems. In the northern part of the zone, they are in contact with soddy-podzolic soils, in the southern part - with steppe chernozems.

In the agricultural use of light gray and gray forest soils, the measures are of the same type. For their effective use, it is necessary to apply organic and mineral fertilizers, liming, sowing perennial grasses. On dark gray forest soils, liming is carried out in exceptional cases. As a result of long-term use, gray forest soils are often depleted and eroded and require chemical reclamation. Grain, fodder, horticultural crops, flax, sugar beets are grown here.

In the woods steppe zone erosion is developed, therefore, it is necessary to carry out anti-erosion measures: soil-protective crop rotations, strip placement of crops, processing across slopes, furrowing, ditching, creating forest belts. Of great importance are measures for the conservation and accumulation of moisture (snow retention, methods of tillage).

With a significant amount of precipitation (600-650 mm), the profile of brown forest soils is washed out weakly, since most of the precipitation falls in summer and the flushing regime is very short. The mild climate contributes to the activation of transformation processes organic matter. A significant part of the litter is vigorously processed by numerous invertebrates, forming a mull humus horizon. Quite a lot of brown humic acids are formed in the subordinate position of quantitatively predominant fulvic acids, giving complexes with iron. These compounds are deposited in the form of weakly polymerized films on fine particles. A fragile-nutty structure is formed.

For the development of burozems, the following environmental conditions are necessary: 1) broad-leaved (coniferous-broad-leaved) forests with a rich ground grass cover with a powerful nitrogen-calcium circulation of substances; 2) washing water regime; 3) subsoil drainage; 4) short freezing of soils, providing intensive weathering; 5) a relatively small age of soil formation due to the tendency of burozems to evolve into other types.

In burozems, two soil-forming processes dominate: claying of the entire soil layer without moving weathering products down the profile and humus formation with the formation of dark, but with brown tones due to the predominance of brown humic and fulvic acids of the humus horizon, stained with iron oxides. Brown forest - always soils of drained slopes, or dissected hilly territory. There are no burozems on the lowlands. The higher the slope, the more humus.

A very common particular soil-forming process is lessivage, that is, the slow washing of silt particles in the form of suspensions into horizon B. The profile of brown forest soils is characterized by weak differentiation, medium-thick (20-25 cm) humus (humus 4-6%, closer to the litter up to 12% ) horizon. The gray-brown humus horizon is replaced by the Bm horizon (50-60 cm) with a lumpy-nutty structure. A diagnostic feature of such soils is the presence of clayey mountains. B in the absence of eluvial horizons. The degree of browning depends on the content of free iron hydroxides.

Clay formation in the profile of burozems can be both the result of the transformation of primary minerals and the synthesis of clays from ionic components. Transformations of micas into illite are especially common, and the brown color mainly determines the deposition of goethite. The soil-forming rock is usually loess-like pale yellow loam, sometimes with carbonate neoformations. The aqueous extract has a reaction close to neutral. A large amount of silty particles causes a significant absorption capacity with a predominance of calcium.

Burozems have a lot of transitional forms with other types. On the FAO/UNESCO International Map of the World, such soils are called cambisols. In addition to the usual burozems, Soviet systematics distinguished gley, podzolic-brown, podzolic-brown gley, and meadow podbel burozems (especially common in the Far East).

High moisture capacity with good water permeability, good thermal properties, significant absorption capacity with a predominance of calcium, stable lumpy structure determine the high level of natural fertility.

These soils are very fertile with a sufficient amount of fertilizers and optimal agricultural practices. The highest grain yields in Europe are obtained on brown forest soils, part of which is occupied by vineyards and orchards. Due to the high water permeability, burozems are resistant to water erosion, and the clay composition prevents deflation.

Chernozem soils of the forest-steppe and steppe zones

Chernozems occupy 1.7% of the land (260 million hectares) and more than 70% of this area is located in the CIS. Significant areas of chernozems are found in Romania, Bulgaria, Hungary, the Czech Republic, and Germany, where they do not form clear zones. They account for 2.6% of the area

On the territory of the CIS, chernozem soils are distributed in the form of a wide belt from the lower reaches of the Danube to Altai and further east in separate massifs to Khingan. Such a latitudinal and especially meridional extent determined the heterogeneity natural conditions, which led to the identification of three main soil facies. They differ in the degree of manifestation of the main processes, the structure of the profile, which was influenced by the change in the hydrothermal coefficient when moving from west to east. These are facies: western - subcontinental; central - continental; the eastern one is extremely continental.

As you move from west to east, the dryness of the climate and its continentality increase, as winter temperatures decrease, and summer temperatures remain at the same level. A milder climate in the forest-steppe: the average temperature in July is from 23-25 °С in the west to 19-21 °С in the east, in January - from -4 to -25 °С. The duration of the period with temperatures above 10 ° C in the west of the forest-steppe is 150-180 days, in the east - 90-120 days, and in the steppe zone, respectively, 140-180 and 97-140 days. The sum of active temperatures in the forest-steppe from west to east varies from 3000 to 1500, and in the steppe zone - from 3600 to 1700 °C. Precipitation falls more in Ciscaucasia - 500-600, in the Volga region - 300-400, Northern Kazakhstan 300-350 mm. The relief in the European provinces varies from flat to plain-ridged and ridged, in the foothill regions of Altai and Eastern Siberia it is flat-undulating and ridged.

Along the watersheds and river terraces in Western Siberia and Kazakhstan there are birch pegs, in the European part - oaks. At present, natural vegetation has been preserved in small areas, since the main massifs of chernozem soils have long been plowed up.

Regarding the origin of chernozems, various hypotheses were put forward, which can be summarized in three groups:

The theory of plant-terrestrial origin;

Hypothesis of marine origin;

The theory of swamp origin.

The founder of the first theory was M.V. Lomonosov, who in 1763 wrote that the chernozem "came from the decay of animal and plant bodies over time." In its final form, this theory was developed by V.V. Dokuchaev (1883), who wrote that chernozem is the result of the combined activity of climate, vegetation, topography and parent rock and that it was formed after the decomposition of grassy steppe vegetation. Then in 1886 P.A. Kostychev found out that the roots of perennial grasses are important in the formation of chernozem, and that is why the dark color of soils stops at the boundary of root formation. Thus, the roots are the main structure-forming chernozems.

According to the maritime hypothesis, chernozem is a product of the deposition of sea silt left after the retreat of the Black and Caspian Seas.

According to the third version, chernozem originated from swamps and tundra, on which low shrubs, sedges, grasses, reeds and other marsh plants grew. The remains of these plants with climate warming served as material for the formation of chernozem.

By modern ideas; in the formation of chernozems, the leading process is humus-accumulative in combination with the migration of calcium bicarbonate in the profile. The course of these processes causes the formation of a powerful humus horizon, the accumulation of nutrients in it and structuring, since plant biomass rich in nitrogen (1-1.5%), ash elements (7-8%) enters the soil, and 40 -60% of the total biomass (10-20 t/ha), 40-60% of the litter falls on the roots.

Humus is best formed by the decomposition of rich litter in a neutral or alkaline reaction, under aerobic conditions, in combination with a favorable temperature and water regime. Such conditions in the chernozem zone are created in spring and early summer. Hummification occurs under conditions of excess Ca(HCO3)2, which contributes to the accumulation of calcium humates, and humic acids predominate in the composition of humus. It almost completely lacks free fulvic acids, which, moreover, are more complex in composition compared to podzolic soils. During the period of summer desiccation, humification weakens, while the rate of mineralization of humic acids decreases and the processes of complication of their molecules intensify. The decomposition of soil minerals due to the lack of free humic acids is difficult. Organo-mineral compounds have a significant share in the composition of humus, which contributes to the formation of an agronomically valuable structure. As a result, chernozems are characterized by the presence of a thick humus horizon with a high content of humus, which gradually decreases with depth, and a carbonate-accumulative horizon under it, although carbonate-free chernozems are also found.

In general, the profile of virgin chernozem has the following structure:

O - steppe felt; A1 - dark-colored humus horizon with a granular structure; AB - dark-colored humus horizon with some browning, with dark brown streaks, spots, structure is nutty or lumpy-granular; B - brown transitional horizon with humus streaks; C - parent breed, usually Sk.

The conditions of chernozem formation depend on facial features. Chernozems of subcontinental or western facies are common in Germany, Poland, Hungary, Moldova, southern Ukraine and Ciscaucasia, where they develop in conditions of short, warm and humid winters, warm summers and dry autumns. As a result, a powerful humus horizon of 100-200 cm in typical and 70-100 cm in ordinary chernozems is formed. They contain from 0.5% in the upper part to 4-6% of carbonates: at a depth in the form of raids, in the form of cobwebs in the upper horizons, micellar form - in the lower ones. Most of these soils are characterized by easily soluble salts and alkalinity. Carbonates stand out from above in the form of spots, from top to bottom - in the form of cranes in typical chernozems, in the form of mycelium and white-eye - in ordinary ones.

Chernozems of the forest-steppe are represented by podzolized, leached and typical, respectively, located in the northern, central and southern parts zones.

The profile of podzolized chernozems has the following structure:

A (Apah) - A1 - A1B - Bt - Vk-Sk. The main distinguishing feature of this subtype is a whitish powder in the humus layer, the color of which is gray or dark gray. There is also a whitish powder in horizon B, which lies below 120-150 cm and gradually passes into the carbonate rock Sk. The thickness of the humus layer (A1+A1B) varies from 30 to 70 cm.

The leached chernozems do not have powdering, the thickness of the A1 horizon is 30-50 cm, the lower boundary of the B1 horizon is at a depth of 70-60 cm. These chernozems are characterized by the presence of the Bt horizon leached from carbonates, which has a brownish color with humus streaks. The transition to the BC or C horizon is distinct, at the boundary there is an accumulation of carbonates in the form of veins, lime mold.

Typical chernozems (A-AB1-B1k-B2k-(BC)-Ck) have a humus profile with a thickness of 90-120 cm or more, carbonates appear at a depth of 60-70 cm (in the lower part of the AB1 or B2 horizon in the form of cranes, mycelium, tubules).

The B2 horizon with humus streaks lies below, passing into the Bk horizon in which carbonates are presented in the form of white-eye. The latter is a diagnostic feature for this subtype. The lower horizons at a depth of 1.5-2.0 m often contain gypsum, sometimes easily soluble salts. Solonetsity is possible with a low content of exchangeable sodium in the soil absorbing complex. They often boil off the surface.

Chernozems of the globe are the most developed soils. These soils are fertile and the sustainability of agriculture is based on them. Valuable grain crops are grown on these soils, including durum wheat, corn, as well as sugar beet, sunflower, orchards and vineyards.

Unfortunately, the realization of the potential fertility of these soils is hindered by an unstable water regime, frequent droughts, and erosion. Therefore, the main measures are the methods of regulating the water regime by creating shelterbelts, organizing the territory, a system of agricultural practices for the accumulation and conservation of moisture, snow retention, etc. To protect against water and wind erosion, soil-protective crop rotations, non-moldboard and minimal methods of tillage, rocker crops, terracing of slopes, etc.

Chernozems are rich in nutrients, but even on these soils it is necessary to introduce mineral, primarily phosphorus and nitrogen, as well as organic fertilizers, without which it is impossible to keep the humus content at the level of the initial values. On the chernozems of the forest-steppe, liming is effective, on alkaline soils - gypsum.

In the agricultural use of chernozems, it is necessary to know about the quantitative values of agrochemical, agrophysical and biological indicators that determine the level of cultivation.

Chestnut soils of dry steppes

The zonal soils of the dry steppes of the boreal belt are chestnut soils. They take on the globe 262.2 million ha, distributed mainly in the Northern Hemisphere. In Eurasia, they are located to the south, and in North America - to the west of the black earth zone at higher absolute levels. Widespread in the USA, in the south of Ukraine, in Russia, Kazakhstan.

The zone is characterized by cold winters with little snow cover and warm dry summers. The temperature in July is 20-25 °С, in January from -5 to -25 °С. The average annual temperature in the European part is 9 °С, in the Asian - 2-3 °С. The sum of temperatures > 10 °С - 2200-3500 °С, the annual amount of precipitation is 200-400 mm, the type of water regime is non-leaching (KU 0.25-0.45). Dry winds are frequent, precipitation falls mainly in the form of showers. Moisture reserves in the soil are created due to snowmelt or autumn rains, since summer precipitation completely evaporates. The relief is flat, disturbed by depressions in the form of depressions, estuaries, depressions. Solonetzes, solods, meadow-chestnut soils are formed in them, which determines the complexity of the soil cover. Soil-forming rocks are loess-like loams, predominantly carbonate, saline marine sediments, chocolate clays of the Aral-Caspian transgression, eluvium-deluvium of various bedrocks.

Vegetation in the zone of dry steppes is heterogeneous, low-growing, sparse, covering the surface by 50-70%. Grasses predominate in its composition, forming wormwood-fescue and wormwood-fescue-feather grass steppes. Solonetzic and saline chestnut soils are covered with wormwood, fescue, rodwort, chamomile, lichens and blue-green algae. Steppe shrubs (tavolozhka, elm) and woody vegetation (oak, aspen, steppe cherry, etc.) are widespread along the bottom of hollows and beams. A significant part of the plant roots (45%) is concentrated in the 0-12 cm layer; in the 12-30 cm layer, their number sharply decreases. In general, the biomass of plants is about 20 t/ha, the annual growth of green mass is about 3 t/ha, the growth of roots is 11 t/ha, annually in biological cycle about 600 kg/ha of ash elements and about 150 kg/ha of nitrogen are involved, the same amount is consumed annually.

The term “chestnut soils” was introduced by V.V. Dokuchaev in 1883 as a special type of soil formation. The same processes are involved in the formation of these soils as in the formation of chernozems, i.e. sod, as well as migration and accumulation of carbonates. But these processes take place in an arid climate and with the participation of xerophytic vegetation; therefore, the accumulation of humus in chestnut soils is weaker than in chernozems, and they are characterized by weak leaching of the profile from carbonates, gypsum, and easily soluble salts.

The chestnut soil profile has the following structure:

Ad - turf; A1 - chestnut humus horizon with a grayish tinge, cloddy-dusty, clearly stratified in the upper part, thickness 15-30 cm; B - humus transitional horizon grayish-brown with a brown tint, compacted, coarse-cloddy-prismatic with vertical cracks, effervescent at a depth of 35-45 cm; C (deeper than 50 cm) - light-yellow or brownish-yellow, dense, prism-shaped, with abundant carbonates in the form of white-eye, veins or powdery accumulations, depending on the hydrothermal regime or parent rock, gypsum appears from a depth of 120-150 cm. Chestnut soils are divided into three subtypes: dark chestnut - contain 4-5% humus; chestnut - 3-4% humus and light chestnut - contain 2-3% humus. According to the content of exchangeable sodium (% of CEC), slightly solonetzic (3-5), medium solonetzic (5-10), strongly solonetzic (10-15) are distinguished.

Chestnut soils are similar in properties to chernozems. The silt profile in ordinary soils is not differentiated, montmorillonite and hydromica predominate in the silty fraction, in solonetzic soils, silt moves to horizon B, as a result of which it is strongly compacted (OM 1.5–1.7 g/cm3), so autumn precipitation is not pass deeper than 70-100 cm. The cation exchange capacity is low, filled with calcium and magnesium by 85%, pHH20 - 7.1-8.1. At various depths there are accumulations of carbonates, gypsum, and easily soluble salts.

Among the chestnut soils in the depressions, there are meadow-chestnut soils, which are distinguished by a greater thickness of humus horizons (45–55 cm), an increased absorption capacity (30–40 meq/100 g), and a higher content of nutrients. Chestnut soils are potentially fertile, dark chestnut soils are half plowed, light chestnut soils are less than 5%. Their use requires, first of all, the improvement of the water regime due to the accumulation of moisture through snow retention, shelter belts, rocker crops, and processing methods. On light chestnut soils, agriculture is unprofitable without irrigation. On alkaline soils, gypsuming is necessary; physiologically acidic forms are more effective from mineral fertilizers.

Chestnut soils are subject to water (heavy) and wind (light) erosion, so it is necessary to implement a set of anti-erosion measures. Alkaline and saline soils should be sown with salt-tolerant crops (alfalfa, sweet clover, wheatgrass, etc.). Meadow-chestnut soils, which are characterized by better water supply due to surface spring runoff, can be effectively used without irrigation.

On the southern border of the coniferous forest zone, about 60 ° N. sh. in the west of Eurasia and in the Great Lakes region of North America, broad-leaved trees join conifers. It is warmer here, humidification is no longer excessive, but sufficient due to greater evaporation. Summers are longer, but winters are cold and covered with snow. In such conditions, oaks, lindens, maples, elms, ash trees, and sometimes beeches can grow. All of them are represented in Eurasia and North America by different species.

In these coniferous-broad-leaved forests, broad herbs appear - plants with wide leaf blades dominate in the grass cover. Large litter of deciduous trees, shrubs and grass cover contributes to the formation of humus, and moderate moisture - to the accumulation of organic and mineral substances in the upper soil horizons.

As a result, soddy-podzolic soils with a well-defined humus horizon are formed. They are usually podzolized. The degree of podzolization depends on the properties of the soil and on the nature of the relief, which affects the drainage of the territory. When the water stagnates, gleying also develops.

As in every transition zone, in mixed forests, the internal structure of the vegetation cover is affected by big influence local conditions: relief, properties of surface rocks.

For example, on moraine loams in southern Sweden, the Baltic countries, in European Russia many forests dominated by spruce or pure spruce forests. Pine forests are widespread on the terminal moraine ridges and outwash plains of Poland, the Baltic States, Belarus, and Russia, composed of rocks of light mechanical composition from the surface. In Belovezhskaya Pushcha, a large forest area located in the zone of mixed forests, 50% of plantations are pine forests, and the remaining half are spruce-pine forests, spruce forests, oak-hornbeam forests, secondary alder and aspen forests.

The heterogeneity of forests is exacerbated by selective logging.

Yes, in central regions In Russia, oak, widely used in the economy, was cut down. It can be guessed that it grew here in mixed forests almost everywhere, based on individual surviving specimens and the presence of shrubs and grasses characteristic of oak forests in coniferous and small-leaved forests. Clearings and fires also contribute to the replacement of polydominant forest communities by monodominant, often secondary birch and aspen forests, sometimes with an admixture of oak or spruce, and sometimes pure. The forests of this zone on both continents were also cut down for agricultural land, since soddy-podzolic soils have a certain fertility.

broadleaf forests

To the south, conifers "fall out" from the forest stand. The forests become purely broad-leaved. In this zone, the average July temperatures are 13-23°C, the average January temperatures are not lower than -10°C. Moisture conditions are different, but at least 500 mm of precipitation falls annually, and the summer is quite humid. Under such conditions, forests grow in the oceanic sectors of the continents and disappear in the central parts, where it is hotter and dry summer and cold winter.

Vegetation and soils

In European broad-leaved forests, the main species are pedunculate oak and European beech. They are often joined by maple, linden, ash, elm hornbeam.

These forests, sometimes with an admixture of birch, in the recent past occupied all plains and mountain slopes up to a height of 1000-1200 m in Western and Central Europe. The well-known geobotanist A.P. Ilyinsky called beech forests “the child of the oceanic climate”. On the plains, they do not enter east of Moldova. In the mountains, these forests usually grow on the northern and western more humid and cool slopes or above the oak. Oak forests, which are less demanding in terms of moisture, but require summer heat, reach the easternmost border of the zone and also form forest islands in the forest-steppe. The original form of oaks were evergreen species, they became deciduous in conditions of relatively low winter temperatures. Indeed, the leaves from oaks fly around later than from other trees, and sometimes dry foliage keeps on the branches all winter. Peculiar chestnut forests of southwestern Europe with an undergrowth of evergreen shrubs - holly and yew berry. They survived only in the lower mountain belt of southeastern France. There are very few forests left in Europe. Only on the slopes of the mountains there are more or less large forests. In the names of some mountain ranges there is the word "forest": Czech Forest, Thuringian Forest, Black Forest (in translation - "Black Forest"), etc. Relatively fertile brown and gray forest soils are formed under broad-leaved forests. They have a fairly thick and dark humus horizon with a humus content of 6-7%, a neutral reaction. The influx horizon has a nutty structure and humus films along the edges of structural units. with such soils, they are almost completely plowed up.

Animal world

The animal world is very diverse and rich. Wild boars, roe deer, red deer, hares, badgers, hedgehogs still live in the surviving forests of Europe, there are martens, forest cats, lynxes, brown bears and some other species predatory mammals. In the forest litter and in the soil, there is an abundant fauna of invertebrates that process leaf litter. There are many insects and their caterpillars in the crowns of trees. They eat leaves and shoots, and small birds feed on them: warblers, warblers, tits. etc. There are birds and rodents that eat seeds and fruits: jays, wood mice and voles, dormice.

Broad-leaved forests of East Asia are peculiar. Here the conditions are somewhat different: at very damp heat cold winter season. The history of the development of the modern organic world was also different than in the West. In glacial epochs, vegetation and animals could retreat south to their usual habitats, since there were no significant sublatitudinal mountain barriers. For the same reason, a free exchange of species between zonal groups is still possible.

Vegetation

Here it is difficult to draw a line between mixed and broad-leaved forests: conifers go far south to the subtropics. In addition, deciduous trees were cut down more intensively, and the proportion of conifers in mixed forests is predominant. But from subtropical latitudes evergreen magnolias, tulip tree, paulownias penetrated into this zone. In the undergrowth, along with honeysuckle and lilac, bamboo and rhododendron are common. There are numerous creepers: actinidia, wild grapes, vineyard, lemongrass. Bamboo and some creepers penetrate far to the north and are found even in the Far Eastern taiga. Lots of endemic plants. In addition to trees common to Europe, represented, however, by their own species, Manchurian walnut, velvet tree, and Chosenia grow here. Araliaceae are widespread. In the grass cover, along with close to European genera and even species, there are endemics: for example, ginseng, one of the Jeffersonia species (other species of this genus are common in North America). Under these forests, as well as under Western European ones, brown forest soils are formed.

In the animal world, the same features are observed as in the plant. The fauna is very rich and unique. It contains animals close to North American and tropical Asian species. Tiger, leopard, marten kharza, some species of birds and insects live from Hindustan to the Far East.

There are few forested areas in East Asia. Within overpopulated China, all serviceable Agriculture The land has long been plowed up. The Far Eastern "Manchurian" flora has survived mainly on the territory of our country, but even here it is under the threat of destruction. There are remnants of these forests in mountainous areas. Better than on the mainland, forests have been preserved on the islands of the Japanese archipelago, where they occupy the lower mountain belt on about. Honshu and in the south about. Hokkaido. Here the participation of evergreen species is great and the degree of endemism in the flora and fauna is high. Forestry significantly altered the composition and structure Japanese forests, but the inhabitants of the country take good care of their forests, especially in numerous national parks and reserves.

Similar reasons determine the originality of the broad-leaved forests of eastern North America. Here, too, there are no sublatitudinal mountain barriers and free migration is possible.

The submeridional strike of the zone has led to the fact that in the north the proportion of broad-leaved species is very large and deciduous forests almost approach the forest-tundra. In the south, the admixture of evergreens increases, which penetrate far to the north. With the change of climatic conditions from temperate to subtropical latitudes, the participation of evergreen and thermophilic flora in general increases, and forests become humid subtropical.

In terms of diversity and preservation of relict plants, these forests are close to East Asian ones. Both have simply common elements - a tulip tree, magnolias, etc. The forests of the Southern Appalachians are especially rich, similar in structure to rain tropical ones: they are polydominant, multi-tiered, with lianas and epiphytes. In the northeastern United States and Canada, broadleaf forests are more similar to European ones. They are dominated by sugar maple, american ash, large-leaved beech. American broad-leaved forests have survived mainly in mountainous regions, but even there they have been significantly modified.

The fauna of the North American forests has features and similarities, and differences with the Eurasian ones.

There are related species: the wapiti deer is a race of red deer, but the virgin deer lives there - a representative of a subfamily endemic to America. Mice and rats are replaced in the same ecological niches hamster-like. Endemic and large water vole - muskrat, which is often called water or musky rat. Similar to the East Asian black bear baribal. Pecan marten, raccoon gargle are endemic, gray fox that can climb trees. In the broad-leaved forests of North America, the only representative of marsupials on the Northern continents lives - the opossum, or marsupial rat. Of the endemic birds, mockingbirds, and Eurasian flycatchers and warblers are replaced by tyrannids and treeworts. In the west, South American hummingbirds penetrate to the northernmost border of the zone.

The productivity of broad-leaved forests is up to 150-200 c/ha, mixed - about 100 c/ha. In large areas of both continents, they are cut down, and the land is occupied by agricultural land. Often, during reforestation, broad-leaved species are replaced by fast-growing conifers and small-leaved species. The animals that inhabited these ecotopes are gradually disappearing, and their ranges are shrinking. The unique richest Appalachian forests and the beautiful chestnut forests of the south of France suffered, among other things. Special measures are required to protect still existing forest areas.