What types of trees live in temperate latitudes. Broad-leaved forests: characteristics of the natural zone, geographical location, climate and soils of broad-leaved forests, map. Forest vegetation of North America and Western Europe

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FOREST, compact array of trees and shrubs. More than a third of the land surface is covered with forests or suitable for their development. However, the areas occupied by forests are unevenly distributed between the continents and even within each of them. For example, forest cover covers almost half of South America, about a third of Europe and the US, and much of Africa and Asia; in Australia, on the contrary, there are few of them, and some major countries, such as Egypt, are generally treeless. Forests are completely absent in Antarctica and Greenland, but low trees grow in the extreme south of the latter.

Although the most characteristic feature of a forest is the presence of trees and shrubs, it is not just woody vegetation, but a complex community (or ecosystem) consisting of closely related elements. Like all ecosystems, the forest is formed by a combination of living organisms (biota) and the inanimate (abiotic) environment of their habitat. The forest biota includes, in addition to trees and shrubs, other plants (grasses, mosses, fungi, algae, and lichens), as well as vertebrates and invertebrates, and bacteria. The abiotic component is represented by air, soil and water. All these components are alive and inanimate nature are closely interconnected due to the passage of energy flow through the ecosystem and the circulation of oxygen and other substances in it. For example, energy sunlight used by plants for photosynthesis, the process of making organic nutrients from water and carbon dioxide. Since this is characteristic only of green plants, all animals must eat either these plants or other animals, which in turn eat plants. Thus, plants directly or indirectly provide food for all other organisms. As a by-product of photosynthesis, oxygen is released into the air, replenishing its reserves in the atmosphere. Bacteria and other organisms involved in the decomposition of organic matter play a vital role important role in forest ecosystems. They turn complex chemical compounds, which make up metabolic waste and the remains of plants and animals, into simple ones that can be reused by organisms.

In most forests, several tiers are distinguished, formed by foliage of plants of different heights. The topmost, consisting of the crowns of the most tall trees, is called the first tier or forest canopy. In some areas, especially in the tropics, individual giant trees rise significantly above the canopy. If there are other relatively closed tree tiers under it, they are called the second, third, etc. Shrubs, tall grasses (in some types of forest) and stunted trees form the undergrowth. The herbaceous layer consists of subshrubs and grasses. Mosses, lichens and creeping plant species form a surface, or ground, layer.

Organic matter, consisting of fallen leaves, twigs, flowers, fruits, bark and other plant remains, as well as feces and animal carcasses, shells of pupae and larvae, etc., forms forest floor on the soil surface. In most forests, the litter is the most densely populated layer. Often there are several million living organisms per square meter - from protozoa and bacteria to mice and other small mammals.

The edge of the forest is a transitional strip between it and the adjacent type of vegetation. It is characteristic that within the limits of the edge the trees are covered with foliage almost to the very ground, and many shrubs and herbs common here are rare or not found at all in the forest and in neighboring open areas. plant communities. Some bird species, often thought of as forest birds, actually live mainly on forest edges, which are also an important habitat type for mammals.

Forest classifications.

There are many types of forests and many ways to classify them. For example, they can be classified by geographical distribution (eastern, tropical, etc.) or by position in the relief (plains, floodplains, etc.). They can also be grouped according to the seasonal aspect. Thus, forests are considered evergreen if living foliage is preserved on trees. all year round. In a deciduous forest, the leaves fall with the onset of the cold or dry season, and the trees remain bare for several weeks or months each year. Some forests, such as the oak forests of the southwestern United States, are formed by trees shedding old leaves and forming new ones within two to three spring weeks. Such communities can be called semi-deciduous or semi-evergreen.

Sometimes the basis for the classification of forests are characteristics the tree species that form them, and the forests are respectively divided into coniferous, broad-leaved, mixed, etc. A combination of morphological and seasonal characteristics is also possible in the classification (for example, evergreen coniferous or broad-leaved deciduous forests). In another case, the names of forest-forming species are used (oak-brown or red-oak-white-oak-holokary forests, etc.).

For some purposes, especially commercial ones, it is useful to classify forests according to the relative age of the trees. For example, stands of the same age consist of trees of approximately the same age, while stands of different ages consist of trees of a wide age range.

There are also sparse (light) or closed forests. In the first case, tree crowns, as a rule, do not touch or overlap, and the canopy is discontinuous. In a closed forest, it is more or less continuous and is formed by intertwining or overlapping tree crowns.

Another descriptive classification is based on the degree of forest disturbance, mainly as a result of human activities. For example, in a virgin (primary) forest, mainly mature or old (overmature) trees grow, and the rest of the vegetation is not artificially changed. On clearings, conflagrations and abandoned fields, secondary, or derivative, forests develop.

FACTORS AFFECTING FOREST GROWTH

It is believed that the distribution of forests is determined mainly by regional climate features, i.e. mainly by temperatures and precipitation, and at a more local level by microclimate. Soils, fires, animals and non-woody vegetation play an important role in creating microclimatic conditions.

Climate and relief.

In general, forests are common in regions where the annual rainfall is at least 250-380 mm, and the duration of the frost-free period is at least 14-16 weeks. Moisture conditions depend on the temperature and the nature of the relief. For example, in the Tucson region (Arizona, USA) there is a desert, and only rarely scattered low trees and saguaro cacti (giant carnegia) grow on the watersheds, and in the west of Colorado, in the national monument of the same name, the slopes of the valleys and hilltops are covered with sparse forests from juniper and cedar pine. Differences in the vegetation of these areas are explained by climatic conditions: despite the same amount of precipitation (approx. 280 mm per year), relative humidity lower in Arizona because due to more high temperatures more water is lost through evaporation and transpiration.

Low temperatures also make water inaccessible to plants (so-called physiological dryness). Under such conditions, cold deserts are formed. The absence of trees in the polar regions and high mountains is explained by the short growing season and the inaccessibility of frozen water for plants.

The impact of local climatic conditions is most noticeable in latitudinally extending valleys or on the slopes of mountain ranges of the same orientation. In the Northern Hemisphere, the slopes of northern exposure are not illuminated by direct sunlight. As a result, they are colder than the southern ones, they have less evaporation and do not change temperatures so quickly and abruptly. Rock weathering is also weaker here, and these slopes are usually steeper. In the semiarid regions, forests can grow on them, while in the southern regions adjacent to them, only shrubs or herbaceous vegetation. In humid areas, both slopes are usually covered with forest, but beech, maple, hemlock and other moisture-loving tree species grow on the northern ones, and oak, hazel and other trees that can tolerate long periods of low soil moisture on the southern ones.

Soils.

Humidity and chemical composition Soils are the main conditions that determine the distribution of trees. As mentioned above, humidity depends on the amount of precipitation and topography. In addition, it is affected by the structure of the soil, i.e. the size of its constituent particles, the degree of their aggregation, or sticking together, and the amount of organic matter present. In general, the larger the particles, the less they are aggregated, the lower the content of organic matter and the water-holding capacity of the soil.

On soils with a high content of certain chemicals, forests and even individual trees usually do not grow at all. A striking example- soils formed on serpentinites - rocks consisting of magnesium silicate with an admixture of iron. Serpentine moors are small, prominent patches of herbaceous vegetation scattered among the forests of Pennsylvania, Maryland, California, several other states, and Canada. Soil salinization is much more widespread, excluding the possibility of growth of almost all tree species. It is observed along the shores of the seas and in deserts.

Some properties of soils, mainly their chemistry, affect the composition of tree species that settle on them. This is especially noticeable in places where alkaline soils formed on limestones closely coexist with acidic soils formed on sandstones, gneisses and shales. For example, in the eastern United States, sugar maple, beech, and basswood are common in calcareous soils, while oak and hazel often dominate in acid soils. In the southwestern United States, limestone soils are treeless, although forests grow nearby on soils formed on other rocks.

Fires.

Few trees can survive fires that recur annually or at intervals of several years, and most species do not tolerate fire at all. Thus, frequent fires usually do not allow the development of the forest and lead to the spread of other types of vegetation, in particular herbaceous. For example, a significant part of the prairies in the United States and Canada, probably for this reason, remained treeless. On almost every continent, areas devoid of trees due to frequent fires cover areas from a few hectares to thousands of square kilometers.

Within forest regions, fires can have a profound effect on forest composition. For example, in the western United States, lodgepole pine and Douglas pine (Menzies' pseudosuga) are commonly found in in large numbers either after strong fires, or in areas that often burn out. Under similar conditions, in the northeast of the United States, Banks pine grows, and in the southeast - pine and bog pine. In the absence of fires, these species are eventually replaced by other tree species. Forestry is now using the method of planned burning, which favors the growth of fire-resistant tree species with valuable wood.

Animals

have a significant impact on both distribution and composition of forests. For example, rabbits in Great Britain and other countries not only leave huge areas treeless, but also deprive them of shrub cover. Bison may be partly responsible for the deforestation of the Midwest prairie North America. Even small mammals, such as mice, can interfere with the reforestation of burnt areas and abandoned agricultural land by eating seeds and nibbling tree shoots. And yet, of all living beings, the most powerful influence on forests is exerted by a person who cuts down and burns them, poisons them with pesticides until they are completely destroyed, and then plows up or builds up the vacant lands. Livestock grazing also hinders reforestation in clear cut areas.

Other factors.

Few studies have focused on the role of shrubs, herbaceous plants, lichens and mosses in crowding out forests or slowing their recovery. However, in forest regions, areas covered with shrubs sometimes remain treeless for more than 30 years. Even a herbage of grasses or other plants, such as goldenrod or asters, can prevent many tree species from settling. Over the past few years, it has been experimentally shown that many of these plants release chemical compounds that inhibit the germination of tree seeds.

FOREST HISTORY

The age of the Earth is 4.5–6.6 billion years. Primitive life forms probably arose at a very early stages the history of our planet, since the fossil remains of plant cells were found in rocks older than 3.1 billion years. The oldest organisms known to us are blue-green algae and bacteria, fossils of which have been found in Africa. Tree plants, and thus the first forests, are relatively recent, and their history spans less than 10% of the Earth's lifetime. Although it would seem that trees are evolutionarily more progressive than flowering grasses, fossil remains indicate that the latter descended from tall tree-like ancestors, and not vice versa.

The oldest land plants are known from the Upper Silurian deposits of Australia, ca. 395 million years. Vegetation, consisting of low shrub forms, spread widely on land in the Early Devonian, ca. 370 million years ago. The first trees were giant horsetails and club mosses, reaching a height of more than 7.5 m. These trees in the Late Devonian formed low-growing forests with an undergrowth of primitive ferns and other small plants.

During the Carboniferous period, which began approximately 345 million years ago, dense forests of giant horsetails, club mosses and tree-like ferns up to 30 m or more high grew on vast areas of land. Apparently, they were confined to waterlogged lowlands, where dead leaves and fallen trunks did not decompose, but accumulated in the form of peat. Subsequently, the peat was covered with silty and sandy deposits. As they accumulated, peat under high pressure conditions gradually transformed into coal. It often contains numerous plant fossils. An important evolutionary event in carboniferous period was the appearance of primitive gymnosperms - seed ferns and cordaites.

The Permian period began c. 280 million years ago with a sharp transformation. The climate became more and more arid, and the face of the planet changed under the influence of powerful glaciation of the Southern Hemisphere, mountain building and catastrophic redistribution of land and sea. During this period, giant horsetails, club mosses and tree ferns died out, they were replaced by primitive cycads and conifers. The appearance of the Earth's forests began to change, and this process continued for mesozoic era, which began ca. 225 million years ago. In the Triassic and Jurassic periods, cycads and conifers were the main forest-forming species. A lot of ginkgos appeared. One of the species, ginkgo biloba, is still found naturally in Eastern China and is planted as an ornamental tree in the cities of Southern Europe, East Asia and North America. Sequoias also grew in abundance, the range of which is now limited to California and southern Oregon, and in the Triassic and Jurassic they were found in most of North America, Europe, Central Asia and even in Greenland. were most widely distributed coniferous forests from species similar to modern araucaria. Petrified trunks of coniferous trees have been preserved in the Petrified Forest National Park (in translation - stone forest) in Arizona and some other areas the globe.

The oldest known angiosperms, or flowering plants, are palms, the remains of which have been found in Triassic deposits in Colorado. Next, Jurassic period characterized by an increase in the diversity of flowering plants. The role of conifers and other gymnosperms decreased, and gradually over Cretaceous(135-65 million years ago), flowering plants became dominant, mostly trees and shrubs. They were represented by the ancestors of such modern species as ficus, magnolia, holly, oak, sassafras, willow and maple. During the Cretaceous and Paleogene, metasequoia, the "deciduous" conifer tree, now growing only in the interior of China. The wide development of forests of this composition in North America, in Greenland and in most of the Arctic indicates that a mild climate prevailed on Earth.

The Paleocene period, which began ca. 65 million years ago, was characterized by a warm, humid climate. Under such conditions, the flora was distinguished by species diversity and abounded in angiosperms. Almost everywhere in the Northern Hemisphere, forests were distributed, similar in composition to modern forests tropics and temperate zone. The most northern of the main types of flora that existed at that time, arcto-tertiary, included deciduous trees and other plants very similar to those currently growing in eastern North America and Asia. The second type of flora, Tertiary Neotropical, was confined to lower latitudes and was represented by evergreen broad-leaved species related to modern species growing in the tropics and subtropics.

In the Neogene, climatic conditions apparently became more diverse, and there was a shift in flora types towards the equator. Forest areas were shrinking, and grass communities were spreading over ever larger areas. The third type of flora - madrotetian - was apparently formed on the basis of the above two in connection with the progressive aridization of the climate in the west of North America. This flora is characterized by small-leaved trees and shrubs, close to those now growing in the southwestern United States and Mexico.

The arctotertiary flora has spread circumpolarly in the northern regions of the globe. Forests throughout this territory were marked by a striking similarity. They were dominated by broad-leaved species (elm, chestnut, maple), as well as alder and metasequoia. In the Late Cenozoic, many trees that are now characteristic of the eastern regions of the United States with wet summers disappeared in the west of North America as a result of mountain building processes and climate changes that took place there. conifers playing minor role in the arcto-tertiary flora, became predominant in the western forests.

Final period cenozoic era, called the Quaternary, began ca. 1.8 million years ago and continues to this day. It was characterized by the alternation of extensive continental glaciations and warm interglacial epochs, similar to the modern one. Despite the short duration of the Quaternary period (only 0.5% of the history of our planet), it is with it that the evolution of man, who has become the dominant species on Earth, is associated. In Europe, the composition of forests has become simpler, as many tree species have died out, and the area of ​​​​forests themselves has been significantly reduced everywhere. Huge areas of land were repeatedly covered with powerful ice sheets, and then freed from ice. Even now, 10,000 years after the end of last glaciation, the forests of the Northern Hemisphere are still adapting to the climate changes that have taken place since then.

FORESTS OF THE GLOBE

According to the nature of the forest cover, three large latitudinal zones can be distinguished: boreal, or northern, coniferous forests(taiga); forests temperate latitudes; tropical and sub rainforest. In each of these zones, there are several types of forests.

Zone of boreal (taiga) forests

The boreal forest zone is the northernmost. It extends from 72° 52º N. in Asia (which is much north of the Arctic Circle) to about 45 ° N.L. in the central part of this continent and in the west of North America. There is no similar zone in the Southern Hemisphere.

The taiga forests are characterized by evergreen conifers, mainly different types of spruce, fir and pine. Deciduous deciduous trees are also common, such as various types of birch, alder and poplar. In Siberia, larch dominates, shedding needles for the winter.

Temperate forest zone.

Such forests are common in North and South America, Asia, Africa, New Zealand and Australia. They are represented by summer-green (deciduous), broad-leaved, coniferous, evergreen, mixed (rain), hard-leaved (sclerophilous) and other less common types of forests.

Summergreen forests are common in eastern North America, the British Isles, mainland Europe, East Asia and Japan, as well as in the extreme southwest of South America. Usually they consist of only one tree layer, although in some areas a second one is also expressed. Shrub undergrowth is developed in some places, usually not having a continuous distribution. There are few tree vines here, and as a rule, only mosses, liverworts and lichens are represented from epiphytes. They play a significant role herbaceous plants that bloom in spring when the trees are bare. Most trees also bloom in the spring, before the leaves come out.

Coniferous forests of temperate latitudes are distributed mainly in the west and southeast of North America and in Eurasia. The most characteristic of them are various types of pines, but other conifers are also common in the west of North America.

Evergreen mixed (rain) forests of temperate latitudes are found where there is a lot of precipitation, and temperatures rarely fall below 0 ° C. Such communities are found in the southwest of North America, the southeast of the United States, southern Japan, Korea, China, Australia, New Zealand and the extreme south of Africa. Oaks, magnolias and notophaguses dominate here, to which conifers are mixed. Of the epiphytes, lichens and mosses are most characteristic, densely covering the lower parts of tree trunks.

Hard-leaved (sclerophyllous) forests are common in areas with dry, hot summers and cooler, wetter winters, dominated by evergreen trees and shrubs with small, leathery leaves. Trees are usually stunted with twisted trunks. Sparse forests of this type are typical for the Mediterranean and Black Sea regions, where evergreen oaks and pines predominate. Forests of the Mediterranean type, but with a different species composition, are also found in the extreme south of Africa, in Australia, Mexico, central regions Chile and the southwestern United States.

Tropical and subtropical forest zone.

This zone is the leader in species diversity of tree species. For example, at least 2,500 tree species grow in the Amazon basin alone. It is believed that there are about the same number on the Malay Peninsula. As a rule, the trees of this zone are thin-barked with thick leathery leaves covered with a wax coating. Usually the leaves fall off at the same time and are quickly replaced by new ones, so the plants are never naked. Although some species shed all their foliage at once, different breeds this leaf fall occurs at different times and is not associated with any specific seasonal phenomenon. In tropical rainforests, caulifloria is extremely widespread, i.e. the development of flowers and fruits directly on the trunk and branches of trees.

Savanna forests are common in tropical regions with a distinct dry season and less annual rainfall than in the dense forest belt. It is characterized by trees from the legume family, usually with a flat umbrella-shaped crown, shedding foliage in the dry season. As a rule, they are far apart from each other, except in places where groundwater is near the surface. The grass cover is almost continuous and is formed mainly by grasses. Usually the height of the trees is less than 18 m, and often no more than 3–4.5 m, and therefore, during the wet season, grasses can rise above the tree layer. Savanna forests cover most of Cuba and other islands caribbean, many areas of Brazil, northern Argentina, Eastern and Central Africa and some areas of India, China and Australia.

In those tropical regions where precipitation is even less and the dry season is longer, communities of xerophilous thorny trees and shrubs are widely developed. They are common in South America, the Caribbean, Mexico and Central America, northern Africa and Australia. Tree species here are deciduous or with leaves in the form of scales. Leafless shrubs with green stems are also characteristic. Many species are covered with spines, and the stems or roots of plants are often swollen and composed of water-storing tissues.

Typical savannas are common in the tropics and subtropics. These are "park" communities in which individual deciduous or evergreen trees or their groups are scattered among a dense carpet of high grasses. Savannahs are found in hot climates with fairly high rainfall (over 2000 mm per year), relatively evenly falling during the wet season lasting from 4 to 6.5 months. Huge areas can be flooded during the rainy season. Acacias and other legume trees are most common in savannahs, but palm trees are also common.

The roots of most tree species here reach the usually shallow water table, so the trees are only short of moisture during exceptionally dry periods. Their trunks are mostly low and often twisted, and the crowns are located at a height of 3–6 m. Savanna grasses up to 4.5 m high sometimes rise above the trees.

FOREST MANAGEMENT AND FOREST PROTECTION

The science that studies forests is called forest science. One of its main applied industries is forestry, which develops methods for reforesting, utilizing and reforesting clear cuts, burnt areas and otherwise disturbed forest areas. It is also dealing with the problem of creating forests in formerly treeless areas. Forestry requires knowledge of the properties of tree species and their genetics in order to breed hybrids or select natural lines with special traits, such as increased resistance to insect or disease attack and high growth rates. The direction called dendrology is associated with the classification of trees. Another area of ​​forestry is the ecology of tree species.

Dendrometry, or forest inventory, is the establishment of quantitative parameters of forests: timber reserves, height and quality of trees and stands. Such data are needed to evaluate forests for commercial purposes, as well as to study their development and determine the effectiveness of various methods of their use and cultivation.

Forest inventory - a system of measures for the cultivation and purposeful use of forests based on knowledge in the field of forestry, socio-economic information and experience entrepreneurial activity. The first attempts at rational forest management were aimed at improving hunting conditions and the renewal of game animals. In the 18th century, forest management work began in Germany in order to increase wood production. Although in the United States already in 1817 protected plantations appeared to provide ship timber navy but only at the end of the 19th century. showed interest in forest management. Initially, two goals were pursued: water protection and logging. Later, the concept of multi-purpose use of forest areas was formed: for wood production, reproduction wildlife, protection of water and soil resources, recreation, scientific research, satisfaction of aesthetic and other needs. Usually one of these functions predominates, but there are also multi-purpose forests.

Another important area of ​​modern forestry is the protection of forests. Every year, forests are severely affected by insect and disease infestations, fires and adverse weather events such as hurricanes, droughts and heavy snowfalls with gusty winds, resulting in icing of trunks and branches. A person can also apply great harm irrational logging, grazing in unsuitable for this purpose forest lands, the destruction of predators that control the number of pests, and direct deforestation.

Protection of wildlife resources.

Many species of game animals are part of forest ecosystems and are often found in forest lands and where forests alternate with open landscapes. In addition, many species of fish abound in dense, cool waters in forested watersheds. Beaver, mink, elk, bear, fox, deer, turkey, partridge and other large and small game animals inhabit mainly forests. Some species prefer old forests, others prefer young communities with dense undergrowth and undergrowth, and still others live where forests alternate or border on treeless areas. One of the tasks rational use forests - the creation of the most favorable conditions for the habitat of a certain species of animals or to ensure the greatest species diversity fauna.

Protection of waters and soils.

Forests in general are very effective in regulating surface runoff and conserve water in the soil. Everyone who has taken shelter from the rain under the trees knows that their crowns intercept and retain part of the precipitation. Most of the rest of the water is absorbed by the soil rather than running down the surface into rivers and lakes. Therefore, soil erosion is poorly developed in forested areas. Although part of the absorbed moisture again comes to the surface from the springs, this does not happen immediately, but after a few days or weeks, and is not accompanied by sharp floods. Another part of the infiltrated moisture enters deeper aquifers and replenishes groundwater.

Fighting forest fires and their prevention.

Fires damage or destroy valuable wood and adversely affect reforestation. By depriving the soil of vegetation cover, they lead to serious and long-term deterioration watersheds, reduce the recreational and scientific value of landscapes. At the same time, wild animals suffer or die, houses and other buildings burn down, people die.

Of all the events that cause economic damage to forests, forest fires are the most controllable, as most of them are caused by humans.

To prevent forest fires mass propaganda (posters, thematic exhibitions, special environmental programs) and enforcement of laws restricting the use of fire in forests are important. Reducing the risk of fire is equally important. To do this, flammable shrubs are removed along the roads. To reduce the risk of fire from lightning strikes, deadwood is cut down. Inside the forests, fire-fighting clearings are laid, dividing the forest into sections, within which the fire is easier to localize and extinguish.

When a forest fire starts, first of all, it is necessary to accurately and quickly detect its source. During periods of special fire danger, for example, during a drought, air patrols are additionally active. When a fire is spotted, firefighters are alerted to its location and extent. Dispatchers quickly form and dispatch fire brigades, often assisted by volunteers. While the fire is being fought, observers on towers and in the air transmit by radio information about the speed and direction of its spread, which helps to quickly extinguish the fire.

Control of pests and diseases.

The cost of wood loss due to insect damage and disease outweighs the damage caused to forests by all other factors, including fires.

IN normal conditions the number of insect pests and disease-causing organisms (pathogens) in forests is relatively low. They thin out dense young stands and kill weak or damaged trees. Nevertheless, from time to time the number of such insects or pathogens increases dramatically, which leads to the death of trees over large areas. The complete extermination of all harmful species is economically unprofitable and biologically unreasonable. Therefore, the task of protecting forests is to prevent outbreaks of their numbers and reduce losses in cases where such outbreaks do occur.

To develop methods for protecting forests from damage, it is necessary to Scientific research. They include determining the species of forest pests, studying their life cycle, food or host species, and natural enemies. These works make it possible to develop new lines or hybrids of tree species that combine resistance to diseases and pests with useful economic properties.

To reduce the populations of forest pests such as gypsy moth, spruce budworm and moth, aerial spraying of insecticides was widely used in the past. However, this destroys not only the pests against which it is used, but also beneficial insects. Insecticides are also deadly to birds, mammals, and other animals, so such measures are usually resorted to only when all other measures have failed.

Herbicides are used to kill intermediate hosts of disease-causing organisms or infected trees in order to limit the spread of the disease. Direct treatment of plants with pesticides is usually advisable only in nurseries and artificial plantations. Most pathogen killers are applied to the soil or applied at the seedling stage before planting.

A number of preventive measures are applied to avoid or reduce the damage caused by pests or diseases. Particularly susceptible to diseases, weak or infected trees are removed during periodic sanitary felling. intermediate hosts pathogens are killed with herbicides. Measures are being taken to protect and increase the number of natural enemies of insect pests.

FOREST CLEARING

The destruction of forests on earth is happening at an alarming rate. In the mid-1990s, according to the World Resources Institute, tropical forests alone were disappearing at a rate of 16-20 million hectares per year, i.e. 0.6 hectares per second, mainly to meet the needs of a growing population for agricultural land and timber. IN temperate zone Northern hemisphere forests are heavily affected by air-polluting industrial waste, and the vast forests of Siberia (the taiga) are under the threat of large-scale deforestation.

Deforestation is a major global environmental problem. Forests in the process of photosynthesis absorb a huge amount of carbon dioxide, so their destruction can lead to an increase in its concentration in the atmosphere, which, as many scientists believe, will increase in the 21st century. will contribute to global warming due to the so-called. greenhouse effect. Moreover, the now widespread burning of tropical rainforests in developing countries leads to an increase in carbon dioxide in the atmosphere. IN tropical forests the majority of species of animals, plants and microorganisms of the planet still live, the diversity of which is constantly declining. Some of them are used or will be used in the future in medicine and agriculture.

Literature:

Geography forest resources the globe. M., 1960
Forests of the USSR, tt. 1–5. M., 1966–1970
Walter G. Vegetation of the globe, tt. 1–3. M., 1969–1975
Bukshtynov A.D., Groshev B.I., Krylov G.V. Forests. M., 1981

Lush crowns in summer deciduous trees create a deep shadow. Therefore, light-loving forest plants bloom in spring, when the leaves on the trees have not yet blossomed. Other forest plants have adapted to the lack of light. In the glades, where there is a lot of sun, grasses and flowers grow rapidly all summer. Large herbivorous deer graze here. They eat young shoots of trees and shrubs, preventing clearings from overgrowing.

In the broad-leaved forests of Eurasia live fallow deer, roe deer, spotted deer and noble olein, which are also called deer or red deer. Red deer live in small groups. Males stay separate from females for most of the year. Only males have horns. In early spring they shed old horns and new ones begin to grow in them, which are finally formed by the beginning of autumn. In early autumn, deer begin mating season- the rut, accompanied by a roar and fights of males. Deer grapple with branched antlers, trying to knock down an opponent. The winner gathers several females around him, protecting them from other males. And in spring, females give birth to one calf. The mother spends a whole year with the baby, protecting him from danger. The spotted skin of deer camouflages them well among the light and shadow of the forest.

Forests are temperate latitudes - the ecosystem most severely affected by human activity. These forests, which once occupied vast areas of Europe and Asia, were cut down for agricultural land, the construction of villages and cities, and as a result, many species of animals and plants disappeared. Now in Europe, only small areas of untouched forests have survived, most of which have become nature reserves. Reserves are protected areas of wildlife, but which are located rare species animals and plants. Any economic activity is prohibited in the reserves.

Belovezhskaya Pushcha - reserve; located on the border of Belarus and Poland, is one of the last untouched forests in Europe. A rare species lives here and in natural conditions. wild bull- bison. For a long time the bison was an object of hunting and at the beginning of our century completely disappeared in the wild, surviving only in zoos. In many countries, measures were taken to restore the number of bison - they were bred in nurseries and released into the wild. Now in many reserves there are herds of wild bison, and this animal is no longer threatened with extinction.

Boars live in the forests of Europe and Asia - omnivorous wild pigs. They prefer damp swampy places where they like to wallow in the mud. An adult male - a billhook - has sharp long fangs resembling daggers. Cleavers dig with fangs

juicy roots from the ground, defend themselves from enemies and fight for the female. A female boar is sometimes called a pig. It is she who builds a large nest from boughs and spruce branches for her offspring - Gaina. Its bottom is covered with moss, grass and leaves, so that the piglets are warm and cozy.

Beavers are skilled dam builders. These large rodents block forest rivers: they gnaw trunks of young trees with their sharp teeth, fell them and drag them to the river, where they lay them in heaps on the bottom, fixing them with clay and stones. In the resulting dam, a beaver hut is being built - a nest for a female with cubs. When the water level rises, the beavers build new floors so that the top of the nest is above the water. And the entrance to the nest, for security reasons, is arranged under water. In summer, beavers feed on tree bark, leaves, and grass. For the winter, they store wood, the warehouse of which is arranged at the bottom of the river. As a result of the activity of beavers, the water of blocked rivers sometimes floods large areas of the forest.

Badgers - representatives of the mustelid family - are excellent underground builders. They live in families, digging complex burrows underground with a cozy nesting chamber, several entrances and many otnorok - dead ends and pantries. There are even special spaces in these holes - the Badger's toilets are very clean, they constantly clean and expand their housing. Badger settlements gradually grow, turning into underground settlements that can last up to a hundred years.

Badger otnorks often inhabit other forest dwellers, such as foxes. Foxes are sluts, and if they settle nearby, clean badgers sometimes leave their holes themselves.

The forest is full of life - damp lowlands and streams are inhabited by frogs and newts, under tree bark, many insects live in the forest floor, butterflies fly over the flowers, and nimble lizards hide in the crevices of stones

In spring and summer, songbirds, titmouse, robin, warbler, song thrush and nightingale fill the forest with their trills. Some of them feed on fruits and seeds, others catch insects.

Jay - a large forest bird - steals eggs and chicks of other birds in summer, and in autumn, like a squirrel, it stocks up acorns for the winter, burying them in the ground. The Sparrowhawk is the main gate of the forest birdies. This wasp has rounded wings that allow it to easily maneuver through the trees while chasing prey.

They occupy a much smaller area in the forest zone than the taiga. They grow in the west of the European part of Russia and in the south of the Far East.

In Siberia, mixed and broad-leaved forests are absent: there the taiga passes directly into the steppe.

More than 90% of mixed forests consist of coniferous and small-leaved species. This is mainly spruce and pine with an admixture of birch and aspen. There are few broad-leaved species in mixed forests. Broad-leaved forests consist mainly of oak, linden, maple, elm, in the southwestern regions - ash, hornbeam, beech. The same breeds, but local species are also represented on Far East, where, in addition, grow Manchurian walnut, grapes and creepers.

The northern boundary of the distribution of the zone lies approximately along 57 ° N. sh., above which the oak disappears, and the southern one adjoins the northern border of the forest-steppe, where the spruce disappears. This territory forms, as it were, a triangle with peaks in Leningrad, Sverdlovsk, and Kyiv.

Mixed and broad-leaved forests are located mainly on the East European Plain, which has a flat, low-lying surface interrupted by a number of uplands. Here are the sources, watersheds and pools largest rivers European part of Russia: Volga, Dnieper, Western Dvina. On floodplains, forests are interspersed with lush meadows, and on watersheds - plowed fields. Due to the proximity of groundwater and limited runoff, flat lowlands are heavily swamped in places (Polesie, Meshchera). In addition to forest swamps and lakes, in some areas there are sandy soils covered with pine. In forests on clearings and swamps, many berry bushes and herbs grow.

Compared to the taiga, the climate is mixed and deciduous forests less severe. Winter is not so long and frosty, summer is warm. average temperature January -10...-11°С, and July + 18...+19°С. The average annual rainfall is from 800 to 400 mm. In general, the climate is transitional from maritime to continental in the direction from west to east. If in the Baltic States and Belarus the proximity of the sea smooths out the difference between the air temperature in summer and winter, then in the Vyatka and Kama basins it becomes significant. In summer, the air here warms up to +40°С, and in winter frosts reach -45°С. Winds prevail in all seasons of the year, carrying moisture from Atlantic Ocean.

The snow cover is less thick than in the taiga, with a layer of 20-30 (in the west) to 80-90 cm (in the east). It lasts an average of 140-150 days a year, in the southern regions - 30-60 days.

With the onset of winter, life in the forests, especially in broad-leaved ones, freezes. Most insectivorous birds fly away to warmer climes, and some of the animals flow into hibernation or sleep ( the bats, hedgehogs, dormouse, badgers, bears). In spring and summer, all tiers of forests are inhabited by various animals.

According to the generally accepted classification, plants are divided into coniferous and deciduous. The latter include those that shed their green cover at a certain time. As a rule, such trees grow during the spring-summer growing season, change color during the fall, and then shed their foliage. This is how they adapt to the winter cold.

In deciduous forests grows a lot different types trees, shrubs and herbs. Most of them are representatives broadleaf plants such as oak, maple, beech, walnut, hornbeam and chestnut. Small-leaved trees are also often found here - birch, poplar, linden, alder and aspen.

There are several different types of crops such as mountain laurel, azaleas and mosses that live in a shady forest where little sunlight reaches.

Deciduous forests of Russia

On the territory of Russia, deciduous forests occupy a narrow strip between the southern steppes and northern zone mixed forests. This wedge stretches from the Baltic republics to the Urals and beyond, to Novosibirsk and the Mongolian border. This zone has a warm and humid climate.

In the northern regions, the common oak, linden, ash, maple, and elm are mainly distributed. In the western and southern parts, the variety of species increases due to hornbeam, birch bark, nuts, sycamore, cherry, and poplar.

Most of the secondary forests in this zone are pure birch stands, very popular with Russian landscape painters. Do not count the variety of shrubs and herbs that are rich in the deciduous forest zone of Russia.

Soils

Brown soil prevails in the bulk of deciduous forests. This is a very fertile land. In autumn, the leaves fall from the trees, decompose and help to give the soil its nutrients. Earthworms help mix nutrients, enriching it with humus.

Tree roots go deep into the ground, extracting nutrients during the growing season. However, with the onset of autumn, the foliage crumbles and enriches the soil with useful trace elements.

Deciduous forest zone

Deciduous forests are located between the subtropics and the zone of mixed and coniferous forests. It is somewhere between 500-600 and 430-460 latitudes. The reflection of latitudes is mirror image for the Northern and Southern hemispheres. Regardless, the world's largest deciduous forests are usually concentrated in the North. You will find them in Europe, North America, parts of Russia, China and Japan.

There are also deciduous forests in the Southern Hemisphere, although they are usually much smaller and extend across the expanses of New Zealand, southeastern Australia and South Asia. In South America, there are two large areas of deciduous forests in southern Chile and in Paraguay. It should be noted that vegetation animal world in them is usually different from life in the north.

Deciduous forests tend to thrive in hilly areas with certain types soil.

Climate

As mentioned above, unlike conifers, deciduous forests are defined by the fact that their trees lose their leaves once a year with the change of season, it goes without saying that the climate of most of them is not extreme, but varies with the season. These areas will have four well-defined periods, with pronounced biological processes - the foliage changes color in the fall, falls in the winter and grows in the spring. Deciduous forests are also sometimes referred to as temperate and broadleaf, indicating that they are often found in areas temperate climate. It is he who provides a pronounced seasonality, snow cover in winter and a relatively stable amount of annual precipitation.

The average temperature in the warm seasons is +15 C, and the lower one, as a rule, drops below 0 C. The amount of precipitation reaches 500-800 mm. These figures may vary depending on geographic location because, as mentioned above, deciduous forests can be found all over the world.

For the normal life of deciduous forests, the warm period should be at least 120 days, but in some areas it reaches 250 days a year without frost.

weather in deciduous forest depends on the weather in the region. Colder winters tend to increase the diversity of vegetation types.

In the vast territories of North America and Eurasia, mixed and broad-leaved forests are located. The zones of these green areas are in a temperate geographic zone Earth. The list of plants that these forests are rich in includes pine and spruce, maple and linden, oak and ash, hornbeam and beech.

Mixed and broad-leaved forests are the habitat of roe deer and elk and red deer, ferrets and martens, squirrels and beavers, wild boars and foxes, hares and chipmunks, as well as many mouse-like rodents. The birds that consider these massifs their home are storks and cuckoos, owls and capercaillie, hazel grouses and geese, ducks and owls. In the lakes and rivers of this forest zone, mainly cyprinids are found. Sometimes there are salmon.

Mixed and broad-leaved forests have been heavily affected by human activities. Since ancient times, people began to cut them down, replacing them with fields.

Woodlands of North America and Western Europe

The territory has its own southern border. It is located in the western part of Eurasia and in the region of the North American Great Lakes. Its coordinates are about sixty degrees northern latitude. To the south of this mark, along with coniferous species, broad-leaved species are present in the forests. At the same time, trees in different parts lights are represented by their different types.

The climate is mixed and deciduous forests warmer than in the coniferous zone. Summer period in these zones is longer than in the north, but winters are quite cold and snowy. In such mixed and broad-leaved forests, broad-leaved plants with wide blades dominate.

In autumn, they shed their cover, resulting in the formation of humus. Moderate moisture contributes to the accumulation of mineral and organic substances in the upper soil layers.

The transitional strip, on the territory of which they are located, is heterogeneous. In the formation of vegetation in these massifs, local conditions, as well as types of soil rocks, play an important role.

So, for example, in the southern part of Sweden, as well as in the Baltic states large areas are occupied by forests with a predominance of pure spruce forest. They grow on moraine loamy soils.

Somewhat to the south, coniferous species fall out of the forest stand. Forests are only becoming broad-leaved. In these zones, the temperature in January, on average, does not fall below minus ten, and in July this figure is thirteen to twenty-three degrees Celsius.

Forest vegetation of North America and Western Europe

It is difficult to draw a clear line between mixed and broad-leaved forests. Conifers can be found far in the south, up to the subtropical zone. In addition, felling of deciduous trees was carried out more intensively. This caused a predominant proportion of conifers.

The vegetation of mixed and broad-leaved forests is diverse. In the south, from the subtropics, magnolias, paulownias penetrated into their territory. In the undergrowth, next to lilacs and honeysuckle, rhododendron and bamboo can be found. Common in such areas and creepers from lemongrass, etc.

Forests of Russia

In those latitudes where the taiga stretches its southern borders, mixed and broad-leaved forests come into their possession. Their territory extends to forest-steppes. The zone in which the green massifs are located, consisting of trees of mixed and broad-leaved species, is located from western borders Russia to the place where the Oka flows into the Volga.

The climate, which is typical for mixed and deciduous forests of Russia

Nothing protects the zone of green areas from the influence of the Atlantic Ocean, which determines weather on its territory. The climate of mixed and broad-leaved forests of Russia is moderately warm. However, it is quite soft. Climatic conditions This zone has a favorable effect on the growth of coniferous trees along with broad-leaved trees. At these latitudes there is warm summer and relatively long cold winters.

The atmospheric temperature of mixed and broad-leaved forests during the warm period has an average value exceeding ten degrees. In addition, the climate in this zone is characterized by high humidity. During the warm period, it falls and maximum amount precipitation (ranging from 600 to 800 millimeters). These factors favorably affect the growth of broad-leaved trees.

reservoirs

On the territory of mixed and broad-leaved forests of the Russian Federation, abounding rivers originate, the path of which passes through the East European Plain. Their list includes the Dnieper, as well as the Volga, the Western Dvina, and others.

The occurrence of surface water in this zone is quite close to the surface layers of the earth. This fact, as well as the dissected landscape of the relief and the presence of clayey-sandy deposits favor the formation of lakes and swamps.

Vegetation

In the European region of Russia, mixed and broad-leaved forests are heterogeneous. Oak and linden, ash and elm are widespread in the western part of the zone. Moving to the east, the continentality of the climate increases. There is a shift of the southern boundary of the zone to the north, and at the same time, fir and spruce become the predominant tree species. The role of broad-leaved species is significantly reduced. In the eastern regions, linden is most often found. This tree forms the second tier in mixed forest areas. Undergrowth develops well in such areas. It is represented by plants such as hazel, euonymus, and honeysuckle. But in the low-lying grass cover, taiga plant species grow - majnik and oxalis.

The flora of mixed and broad-leaved forests changes as you move south. This is due to climate change, which is becoming warmer. In these zones, the amount of precipitation is close to the evaporation rate. These areas are dominated by deciduous forests. Coniferous tree species are becoming rarer. The main role in such forests belongs to oak and linden.

The territories of these green forests are rich in floodplain and upland meadows, which are located on alluvial soil layers. There are also swamps. Among them, low-lying and transitional ones predominate.

Animal world

Mixed and broad-leaved forests in former times were rich wild animals and birds. Now the representatives of the fauna have been pushed aside by man to the least populated zones or exterminated altogether. To preserve or restore a particular species, there are specially created reserves. Typical animals living in the zone of mixed and broad-leaved forests are the black polecat, bison, elk, beaver, etc. The species of animals living in Eurasia are close in origin to those species whose habitat is European zone. These are roe deer and deer, marten and mink, muskrat and dormouse.

Acclimatized in this area dappled deer and deer, as well as muskrat. In mixed and broad-leaved forests, you can meet snake and agile lizard.

human activities

Mixed and broad-leaved forests of Russia contain huge reserves of timber. Their bowels are rich in valuable minerals, and the rivers have colossal reserves of energy. These zones have been mastered by man for a long time. This is especially true. On its territory, significant areas are set aside for cattle breeding and agriculture. In order to save forest complexes, are created National parks. Reserves and nature reserves are also open.