Coniferous-deciduous forests of the Russian Plain - natural area temperate zone, characterized by a relatively mild, humid climate, growing along the watersheds of coniferous-deciduous forests on sod-podzolic soils. It is also called the zone of mixed forests, which is not entirely accurate, since taiga forests are often mixed in the composition of the species. These two names, apparently, can be considered synonymous.
In the north, the zone borders on the taiga, in the south - on the forest-steppe, in the west, outside the USSR, it passes into the zone of deciduous forests Western Europe... The leading role in the formation of the landscape is played by the position of the zone in the south-west of the forest belt of the USSR, in relative proximity to the Atlantic Ocean. Compared to the taiga, the climate of mixed forests is warmer and more humid, and in its extreme northwest (Kaliningrad region) it is transitional from maritime to continental.
About 50-55 cyclones pass through the Kaliningrad region throughout the year; in winter here almost every second day with the passage of the front. The sum of temperatures for the period with a stable temperature above 10 ° in the north of the zone is about 1800 °, in the south - 2400 °. The average duration of the frost-free period increases from 120 days in the northeast of the zone to 165 days in the west of the Kaliningrad region and in the Kiev region. There is more precipitation in the zone than in the taiga. Their annual amount ranges from 600 to 700 mm, and on the western slopes of the hills it reaches 800 mm. Moisture balance is positive; in the south, it approaches neutral: the amount of evaporation here is almost equal to the annual amount of precipitation. The moisture coefficient of Vysotsky-Ivanov, as in the taiga, is more than one, the Budyko dryness index slightly increases and ranges from 2/3 to 1. There is enough heat and moisture for the cultivation of various crops: gray bread, wheat, potatoes, flax, sugar beet (southwest), hemp (south of the zone), forage grasses.
In conditions of a positive moisture balance, the surface runoff in the coniferous-deciduous forests is large (350-150 mm), the river network is well developed, and the rivers themselves are rich in water. The most significant rivers, the basin of which lies entirely within the zone, are the Western Dvina and the Neman. The Western Dvina, despite the small area of the basin (85100 km 2), has an average long-term water discharge at the mouth of 680 m 3 / sec. Due to the positive moisture balance, groundwater occurs close to the surface (from 0 to 10 m) and is widely used for various economic needs. The variability in the distribution and depth of occurrence is distinguished by the waters of the end-moor ridge. As in the taiga, the mineralization of groundwater in the zone is weak, the concentration of salts ranges from 100 to 500 mg / l.
The proximity of groundwater in a humid climate causes widespread development of waterlogging processes. Upland and lowland bogs cover most of the lowlands and depressions; they are often found on high, but insufficiently drained watersheds. Among the bogs in the north of the zone, high sphagnum peat bogs, sometimes covered with undersized pine, prevail. To the south of Moscow and Minsk, transitional and lowland bogs prevail, containing peat of a lower quality compared to the sphagnum peat of raised bogs. Peat of high and transitional bogs in the zone of coniferous-deciduous forests is widely used for fuel and for fertilizing fields. Large areas of bogs, after draining, have been converted into fertile arable and hayfields. The most expedient is the drainage of transitional and low-lying bogs, which are relatively rich in mineral salts. Agricultural development of raised bogs, poor in mineral salts, requires large expenditures of labor and material resources and does not always bring the necessary economical effect... When developing peat in quarries, it is recommended to leave an agricultural protective layer (the bottom layer of a peat deposit) with a thickness of 30 cm, which is then used as organic matter for the newly created soil.
The zone of mixed and deciduous forests is located in the western part of the plain between the taiga and forest-steppe and extends from the western borders of Russia to the confluence of the Oka and the Volga. The territory of the zone is open to the Atlantic Ocean and its impact on the climate is decisive.
The zone is characterized by a mild, moderately warm climate. In the relief, there is a combination of uplands (200 m or more) and lowlands. The bedded plains are overlain by moraine, lacustrine-alluvial, fluvioglacial and loess rocks. Sod-podzolic and gray forest soils are formed within the zone under conditions of a moderately humid and moderately warm Atlantic-continental climate.
Here the large high-water rivers of the East European Plain begin - the Volga, the Dnieper, the Western Dvina, and others. The underground waters lie close to the surface. This contributes to the development of swamps and lakes with a dissected relief, clay-sandy deposits and sufficient moisture.
The climate of the zone favors the growth of coniferous trees together with broad-leaved ones. Depending on the conditions of the relief and the degree of moisture, meadows and bogs are also formed. European coniferous-deciduous forests are heterogeneous. Of broad-leaved species in the zone, linden, ash, elm, oak are common. As we move to the east, due to an increase in the continentality of the climate, the southern border of the zone shifts significantly to the north, the role of spruce and fir increases, while the role of broad-leaved species decreases.
The most widespread of the broad-leaved species in the zone is linden, which forms the second tier in mixed forests. They have a well-developed undergrowth with a predominance of hazel, honeysuckle, and euonymus. In the herbaceous cover, taiga representatives - oxalis, minik - are combined with elements of oak forests, among which a significant role is played by snow, clefthoof, woodruff, etc.
The natural complexes of the zone change to the south, as the climate becomes warmer, the amount of precipitation approaches evaporation, the dominance is shifting to broad-leaved species, and conifers become rare. In these forests, the main role belongs to linden and oak.
Here, as well as in the taiga, dry and floodplain meadows on alluvial soils are developed. Among the bogs, transitional and lowland ones prevail. There are few sphagnum bogs.
In the zone of mixed and deciduous forests in historical times there were many wild animals and birds. At present, they are pushed aside to the least populated areas or are completely exterminated and are only preserved and restored in reserves. Today, the typical animals of the zone are wild boar, elk, bison, black or wood polecat, badger, etc. In recent decades, the number of wild boar, river beaver and elk has increased significantly.
The boar range border has moved to the northeast and southeast in some places up to 600 km or more. Coniferous-deciduous forests are characterized by animal species characteristic of Eurasia, but mostly similar in origin to the species of western deciduous and mixed forests, for example, European roe deer, European red deer, European mink, marten, dormouse, European forest cat, muskrat. Red deer, sika deer, muskrat have been acclimatized. Among reptiles in mixed forests, a quick lizard and so are widespread.
Rice. 7. Geological structure of the Valdai Upland
The zone of coniferous-deciduous forests has long been densely populated and developed, therefore its nature has been greatly changed by human activity. For example, forests occupy only 30% of the territory of the zone, the most convenient plots are plowed up or occupied by pastures; there has been a change in the animal kingdom species composition- The tarpans and European tours that once lived in the forests have completely disappeared. Marten, wolverine, desman, golden eagle, osprey, white-tailed eagle, white and gray partridges have become rare.
Great work was carried out to restore the river beaver, bison, red deer, increase the number of elk, acclimatize the raccoon dog, American mink and muskrat. Many species of animals and plants have been taken under protection. In the zone, reserves have been created that protect the most typical natural complexes and especially rare animals and plants. Among them is the biosphere Prioksko-Terrasny Reserve, which protects the natural complexes of the center of the zone, which played an important role in the restoration of bison brought from Belovezhskaya Pushcha and the Caucasus in dense coniferous-deciduous forests.
Valdai province extends from upstream rivers Lovati and Zapadnaya Dvina to the north-north-east to Lake Onega. It consists of the heights of Valdai (341 m), Tikhvin (280 m) and Vepsovskaya (304 m), separated by depressions about 100 m above sea level. In the west, the hills abruptly break off with the picturesque Valdai-Onega scarp (up to 150-200 m) to the Priilmenskaya lowland. In the east, the hills gradually turn into the adjacent low-lying plains.
The province is located on the western flank of the Moscow syneclise; therefore, the sedimentary stratum that composes the cover is monoclinal. The Valdai-Onega scarp is usually considered as a carbonic clint (cuesta scarp), which fixes the boundary of distribution of Carboniferous rocks, represented by limestones, dolomites and marls.
The province is located in the marginal part of the Valdai glaciation, therefore, a well-preserved glacial-accumulative hilly-moraine relief with end-moraine ridges (Torzhok, Vyshnevolotskaya, Lesnaya, etc.) and numerous moraine lakes along the basins (Seliger, Volgo, Valdai, Velieux, etc.). This strip of young picturesque landscapes is called Poozerie. The thickness of the moraine covering the preglacial relief varies from 1–2 m to 100 and more meters.
The carbonate rocks under the moraine cause the development of karst landforms where the thickness of the Quaternary deposits is small - within the Carboniferous scarp itself and in the valleys of the rivers cutting through it. Karst forms are represented by saucers, ponors, hollows, as well as cavities, caverns, caves.
The sources of the Volga, Dnieper and Western Dvina lie on the Valdai Upland. Many rivers flow in troughs of glacial melt water, and their valleys are not yet fully formed. Short rivers connect numerous lakes, forming a single water system.
The climate of the province is humid with cool summers. average temperature July is only 16 ° C, and the average daily temperature rarely rises above 20 ° C. Winter is moderately cold. The average January temperature is -9 ...- 10 ° С. Cyclones that often come here cause thaws. Annual precipitation is more than 800 mm, which is the maximum for the Russian Plain. The maximum is in the summer.
The province is characterized by an extraordinary diversity of soil and vegetation cover, which is due to the frequent change of parent rocks and landforms. Moraine hills and ridges are covered with broadleaf-spruce forests on sod-podzolic and podzolic soils. Pine forests predominate on outwash plains, lakeside sands and sandy hills. On limestones, dolomites and carbonate moraine, dark-colored humus-calcareous soils are widespread, on which spruce-broad-leaved forests grow, dominated by oak, with linden, ash and elm in the second tier.
Damp meadows and pine-sphagnum low-lying grassy and convex ridge-hollow bogs with cloudberries and cranberries are scattered among the forests. They are confined to the bottoms of wide valleys, lake shores, and sometimes flat watersheds.
A significant part of the area of the province was long and strongly altered by man, but in some places poorly altered areas are still preserved. Here in 1931 the Central Forest Reserve was created, which now has the status of a biosphere reserve. Its territory is covered with spruce and spruce-deciduous forests typical of the province.
Meshcherskaya province is located between the Klyazma and Oka rivers. In the north, it is limited by the slopes of the Smolensk-Moscow Upland, in the east - by the Oksko-Tsninsky shaft. The typical landscape of Meshchera is a gently undulating alluvial-outwash forest plain 80-150 m above sea level with lakes and swamps. Moraine-erosion uplifts with average heights of 150-200 m are widespread along the edges of Meshchera.
This type of landscape is called woodland. Woodland landscapes formed at the edge of the Pleistocene ice sheet, in depressions of the preglacial relief, along which the flow of melted glacial waters took place. There are also elevated outliers or "loess islands" - opolya. On the East European Plain within Russia, the Polissya type of landscapes forms a whole belt, consisting of the Bryansk-Zhizdrinsky, Meshchersky, Mokshinsky, Balakhninsky, Vetluzhsky, Kamsko-Vyatsky and other woodlands.
Meshchera is confined to the preglacial tectonic trough. At its base, there are Carboniferous limestones overlain by Jurassic and Cretaceous sandy-argillaceous deposits. Quaternary deposits consist of eroded moraine preserved in the highest areas of the preglacial relief (Yegoryevskoe plateau, Oksko-Tsninsky swell, etc.), and large strata of sands and loams of water-glacial and alluvial origin. In the central part of Meshchera, there is a lowland with peat bogs and lakes (Svyatoe, Velikoe, etc.). Around it stretch wide strips of sandy plains with dunes. Rivers flow slowly in flat swampy lowlands and drain them poorly.
Meshchera's climate is moderately humid with cold, snowy and long winters. The average January temperature is -11 ...- 12 ° С. Snow lies up to 150-160 days at maximum height snow cover 50-55 cm. Winter types of weather are unstable - with frosts and thaws. Due to the significant amount of snow, the floods on the Meshchera rivers are long. Summers are warm with maximum precipitation. The average July temperature is 18.5-19 ° C. The annual amount of precipitation (about 600 mm) exceeds the evaporation rate, therefore the territory is excessively humid.
The main area of Meshchera is covered with pine forests, in some places with an admixture of oak and swamps. Spruce and birch forests are less common. Sod-podzolic and sod-podzolic-gley soils have formed under the forests on sands and sandy-clayey sediments. Light lichen forests are widespread on sandy ramparts, hills and dunes; spruce-pine forests with an admixture of oak, maple and linden dominate in the interfluves along the slopes of the valleys; grow on moraine outcrops mixed forests from spruce, oak and linden, with hazel undergrowth and thick grass cover from snow, clefthoof, lily of the valley; wet oak forests are found on the floodplains.
Swamps occupy about 35% of Meshchera's surface. The main types of bogs are lowland and transitional, among which there are sphagnum-sedge, hypnum-sedge, sedge and birch-sedge. Upper bogs are less common, but they form large tracts and contain thick peat beds (up to 8 m) of high quality. The Shaturskaya thermal power plant operates on Meshchersky peat.
Various landscapes are located in the south of Meshchera in the wide valley of the Oka and the strongly meandering valley of the Pra River, as well as in their interfluve. There, in 1935, the Oksky Nature Reserve was created.
Zone of arctic deserts. In this zone lie Franz Josef Land, Novaya Zemlya, Severnaya Zemlya, New Siberian Islands. The zone is characterized by a huge amount of ice and snow in all seasons of the year. They are the main element of the landscape.All year round, the Arctic air prevails here, the radiation balance for the year is less than 400 mJ / m 2, the average July temperatures are 4-2 ° C. The relative humidity is very high - 85%. Precipitation falls 400-200 mm, and almost all of them fall in solid form, which contributes to the emergence of ice sheets and glaciers. However, in some places, the supply of moisture in the air is small, and therefore, with an increase in temperature and strong winds, a large lack of moisture is formed and strong evaporation of snow occurs.
The soil-forming process in the Arctic takes place in a thin active layer and is at the initial stage of development. In the valleys of rivers and streams and on sea terraces, two types of soils are formed - typical polar desert soils on polygonal drained plains and polar desert solonchaks in saline coastal areas. They are characterized by a low humus content (up to 1.5%), weakly expressed genetic horizons and a very low thickness. In the arctic deserts, there are almost no swamps, few lakes, salt spots form on the soil surface in dry weather with strong winds.
The vegetation cover is extremely sparse and patchy; it is characterized by a poor species composition and extremely low productivity. Low-organized plants dominate: lichens, mosses, algae. The annual growth of mosses and lichens does not exceed 1–2 mm. Plants are extremely selective in their distribution. More or less closed groupings of plants exist only in places sheltered from cold winds, on fine earth, where the thickness of the active layer is greater.
The main background of the Arctic deserts is formed by crustose lichens. Hypnum mosses are common, sphagnum mosses appear only in the south of the zone in very limited quantities. Higher plants are characterized by saxifrage, polar poppy, crumbs, stellate, Arctic pike, bluegrass and some others. Cereals thrive, forming hemispherical cushions up to 10 cm in diameter on a fertilized substrate near nesting gulls and burrow lemmings. At the spots of snow, an ice buttercup and a polar willow grow, reaching only 3-5 cm in height. Fauna, like flora, is poor in species; there are lemming, arctic fox, reindeer, polar bear, and among birds, ptarmigan and snowy owl are ubiquitous. On the rocky shores there are numerous bird colonies - massive nesting sites of seabirds (guillemots, luriks, ivory gulls, fulmars, eiders, etc.). The southern shores of Franz Josef Land, the western shores of Novaya Zemlya are a continuous bird colony.
1) What forest zones do you know from the course on geography of continents and oceans?
Taiga, mixed and deciduous forests, humid equatorial forests, variable-humid subequatorial forests.
2) What climatic conditions are necessary for the spread of forest zones?
For the distribution of forest areas, sufficient moisture is required.
Using the maps, determine where the taiga zone is located, what climatic and soil conditions, what relief and inland waters are characteristic of it.
Taiga is a natural zone of the temperate zone, characterized by a cool, humid climate, the predominance of coniferous forests in the vegetation cover on podzolic soils and sphagnum bogs.
Questions in paragraph
* Carefully consider the placement of coniferous forests in the taiga zone on the vegetation map and think about what explains their growth in certain areas.
Dark coniferous spruce-fir forests prevail in the European part of the zone and in Western Siberia, where cedar forests join them. There is sufficient moisture and small temperature differences. Most of the Middle and Eastern Siberia covered with larch forests. Pine forests grow everywhere on sandy and gravelly soils. The forests of the Far Eastern Primorye have a very special character, where on the Sikhote-Alin ridge such southern views like Amur velvet, cork oak, growing in a monsoon climate.
* Indicate the reason for the replacement of taiga with mixed and deciduous forests. Tell us about the climatic conditions of the zone. What tree species are mixed forests made of? What breeds are broadleaf?
Taiga is replaced by mixed, and then deciduous forests due to changes in climatic conditions when moving south. The thermal regime of the zone of mixed and deciduous forests and the degree of its moisture content are favorable for agriculture. Sod-podzolic and gray forest soils are highly fertile. 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 widespread here. Deciduous forests are characterized primarily by such types of trees as oak, beech, hornbeam, maple, linden, chestnut, ash, elm.
* Identify features geographic location mixed forest zones. Describe its climatic conditions.
Mixed forests - natural temperate zone climatic zone... The mixed forest usually borders the broad-leaved forest zone in the south. Their northern border with the taiga roughly passes through St. Petersburg, Yaroslavl and Yekaterinburg. Mixed forest is much more adaptable to cold climates than broadleaf forest. Here, the vegetation already withstands cold winters with average temperatures below -16 ° C and even with frosts as low as -30 ° C. Summers are quite warm here with average values from +16 to + 24 ° C. Annual precipitation is within 500 mm and decreases in the interior of the mainland.
Questions at the end of a paragraph
1. What role does the forest play in human life?
Forests are a source of various valuable raw materials - animal and flora, wood. Wood is used as fuel, for papermaking, in the wood-chemical industry. Forests are an important recreational resource. Forests affect the climate, prevent soil destruction, and purify the air.
2. What are the causes of forest diversity?
The reason for the diversity of forests is in the diversity of natural conditions.
3. What is the difference between the forests of the European part of Russia and the Siberian taiga?
Dark coniferous spruce-fir forests prevail in the European part of the zone and in Western Siberia, where cedar forests join them. Most of Central and Eastern Siberia is covered with larch forests. Forests differ not only in species composition, but also in climatic conditions, soils, flora and fauna.
4. What are the similarities and differences between forest zones North America and Eurasia?
The broadleaved forests of North America, in comparison with the forests of Eurasia, are distinguished by the richness of tree and shrub species. Large-leaved beech predominates in the forests, reaching 40 m in height and more than 1 liter in diameter. In autumn, its leaves turn red-brown and fall off in October - December. Large-leaved beech is used in gardens and parks in the southern regions of Russia as an ornamental tree. Unlike the forests of North America, in the beech forests of Eurasia, there is almost no grass cover and a layer of shrubs. In Eurasia at the 40th parallel there are no natural zones of mixed and deciduous forests and taiga zones. In North America, there is no natural zone of variably humid monsoon forests.
5. Determine where the southern border of Russian forests lies, and think about why forest vegetation is replaced by forest-steppe.
Forest zone occupies more than half of the territory of Russia. It stretches in a wide strip from the western border of Russia with Finland to the river. Lena and Aldan in the east. The width of the forest zone in western Russia is about 2000 km, in Western Siberia about 1300 km, beyond Baikal about 1800 km. In the north, the zone borders on the forest-tundra, in the south - on the forest-steppe, and in Eastern Siberia - on the mountain taiga of Sayan and Transbaikalia. The forest zone is replaced by a forest-steppe due to a decrease in the amount of precipitation.
A mixed forest is an area where deciduous and coniferous trees coexist in a harmonious manner. If the admixture of wood species is more than 5% of the total flora, we can already talk about a mixed type of forest.
Mixed forest forms a zone of coniferous-deciduous forests, and this is already a whole natural zone, characteristic of forests in temperate... There are also coniferous-small-leaved forests, which are formed in the taiga as a result of the restoration of previously cut pines or spruces, which are beginning to displace different types of birch and aspen.
Main characteristic
(Typical mixed forest)
Mixed forests almost always coexist with broadleaf forests in the south. In the northern hemisphere, they also border the taiga.
There are the following varieties of mixed forests in the temperate zone:
- coniferous-broadleaf;
- 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 gives off a combination of laurel and conifers... Any mixed forest is distinguished by a pronounced layering, as well as the presence of areas without 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 deciduous 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 dashed lines. Pure mixed forests are found south of the taiga, as well as beyond the Urals to the Amur region.
Climate
Mixed forest plantations are characterized by cold, but not very long winters and hot summers. Climatic conditions are such that precipitation falls no more than 700 mm per year. At the same time, the moisture coefficient is increased, but it can change during the summer. In our country, mixed forests stand on sod-podzolic soil, and in the west - on brown forest soil. As a rule, winter temperatures do not drop below -10˚C.
Broad-leaved forest plantations are characterized by a humid and moderately humid climate, where rainfall 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 decompose quickly and the soil retains maximum fertility.
Features of the plant world
Features of biochemical and biological processes determine the densification of species diversity as we move to broad-leaved species. European mixed forests are distinguished by the obligatory presence of pine, spruce, maple, oak, linden, ash, elm, and among shrubs the leading ones are viburnum, hazel, and honeysuckle. Ferns are very common as herbs. The Caucasian mixed forests in large volumes contain beech, fir, and the Far East - birch, walnut, hornbeam, larch. The same forests are distinguished by a variety of vines.
Fauna representatives
The mixed forests are inhabited by those animals and birds, which are generally considered to be typical for forest conditions. These are moose, foxes, wolves, bears, wild boars, hedgehogs, hares, badgers. If we talk about individual deciduous forests, then here the species diversity of birds, rodents and ungulates is especially striking. Roe deer, fallow deer, deer, beavers, muskrats and nutria are found in such forests.
Economic activity
The temperate natural zone, including mixed forests, has long been developed by local residents and densely populated. An impressive part of the forest plantations was cut down several centuries ago, due to 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 timber was required for the sailing fleet. Also, deciduous forests were actively cut down for arable land and meadows. Oak plantations have suffered especially badly from such human activity, and it will never be possible to restore them.