On the same biotope, various ecosystems exist over time. The change of one ecosystem to another can take both quite long and relatively short (several years) time intervals. The duration of the existence of ecosystems in this case is determined by the succession stage. A change in ecosystems in a biotope can be caused by catastrophic processes, but in this case, the biotope itself also changes significantly, and this change is not commonly called succession (with some exceptions, when a catastrophe, for example, a fire, is a natural stage of a cyclical succession)

Succession is a sequential, regular change of some communities by others in a certain part of the territory, due to internal factors of ecosystem development. Each previous community determines the conditions for the existence of the next and its own extinction. This is due to the fact that in ecosystems that are transitional in the succession row, an accumulation of matter and energy occurs, which they are no longer able to include in the cycle, biotope transformation, changes in the microclimate and other factors, and thereby create a material and energy base, as well as environmental conditions necessary for the formation of subsequent communities. However, there is another model that explains the succession mechanism as follows [: the species of each previous community are supplanted only by consistent competition, inhibiting and “resisting” the introduction of subsequent species. However, this theory only considers competitive relationships between species, not describing the whole picture of the ecosystem as a whole. Of course, such processes are underway, but competitive displacement of previous species is possible precisely because of their transformation of the biotope. Thus, both models describe different aspects of the process and are true at the same time.

An example of the stage of autotrophic succession is that the forest grows on the site of the fallow.

Succession is autotrophic (for example, succession after forest fire) and heterotrophic (e.g., drained swamp).

Heterotrophic succession stage example - wetland meadow

At the early stages of succession, species diversity is small, but as it develops, diversity grows, the species composition of the community changes, species with complex and long life cycles begin to prevail, larger organisms usually appear, mutually beneficial cooperations and symbioses develop, and the trophic structure of the ecosystem is complicated. It is usually assumed that the terminal stage of succession has the highest species biodiversity. This is not always true, but for climax communities of tropical forests this statement is true, and for communities temperate latitudes peak diversity occurs in the middle of the succession series or closer to the terminal stage. In the early stages, communities consist of species with a relatively high rate of reproduction and growth, but low ability to individual survival (r-strategists). In the terminal stage, exposure natural selection favors species with a low growth rate but greater survival ability (k-strategists).

As we move along the succession series, there is an ever greater involvement of nutrients in the cycle in ecosystems, possibly a relative closure of flows of nutrients such as nitrogen and calcium within the ecosystem. Therefore, in the terminal stage, when most of biogens involved in the cycle, ecosystems are more independent from the external input of these elements.

To study the succession process, various mathematical models are used, including stochastic ones.

Climax community

Yelnik (spruce forest) is a typical example of a climax community developing on some loamy soils in Northwest Russia in the southern taiga subzone. The concept of succession is closely related to the concept of climax community. The climax community is formed as a result of a successive change of ecosystems and represents the most balanced community], which uses material-energy flows as efficiently as possible, that is, supports the maximum possible biomass per unit of energy entering the ecosystem.

Pine forest as a climax community, on the contrary, develops on sandy and loamy soils

Theoretically, every succession series has a climax community (ecosystem), which is the terminal stage of development. However, in reality, the succession series is not always closed by menopause; a subclimax community can be realized, which is a community that precedes the climax community, which is sufficiently developed structurally and functionally. Such a situation can occur due to natural causes - environmental conditions or due to human activities (in this case it is called disclimax).

The emergence of biocenosis begins with the appearance of the first organisms in areas deprived of life (lava flows, volcanic islands, screes, exposed rocks, sand deposits and dried bottoms of water bodies). Settlement begins with the accidental introduction of organisms from territories already developed by them and depends on the properties of the substrate. This site for many plant seeds and animals that have entered here may not be suitable for propagation. Often, especially in the humid zone, the first settlers are representatives of algae, mosses and lichens.

As a rule, only a few of the introduced plant species successfully develop. Consumer animals settle a little later, since their existence without food is impossible, but their accidental visit to the developed areas is a fairly common occurrence. This stage of development of the biocenosis was called pioneer. Although the community has not yet formed at this stage, it already has an impact on abiotic environment: soil begins to form.

The pioneer stage is replaced by an unsaturated one, when plants begin to renew (by seeds or vegetatively), and animals multiply. Not all are engaged in unsaturated biocenosis environmental niches.

Gradually, the rate of settlement of the site increases due to both an increase in the number of individuals of pioneer vegetation before the formation of thickets, and the introduction of new species. The species composition of such a community is still unstable, new species are introduced quite easily, although competition is beginning to play a prominent role. This stage of development of the biocenosis group.

With the subsequent development of the community, the differentiation of the vegetation cover by tiers and sinusias occurs, its mosaic, species composition becomes stable food chains and consortia. In the end, all ecological niches are occupied and the further introduction of organisms becomes possible only after the crowding out or destruction of old-timers. This, final, stage of biocenosis formation is called saturated. However, the further development of the biocenosis does not stop, and random deviations in the species composition and relationships both between organisms and the environment can still take place.

Random deviations in the structure of the biocenosis are called fluctuations. As a rule, they are caused by random or seasonal changes in the number of species included in the biocenosis as a result of adverse meteorological phenomenafloods, earthquakes, etc.

Although the biocenosis is a rather conservative natural system, however, under the pressure of external circumstances, it can give way to another biocenosis. Sequential shift in time of some communities by others in a certain part of the environment is called succession. As a result of succession, one community is successively replaced by another without a return to its original state. Succession is caused by the interaction of organisms, mainly wounds, with each other and with the environment.

Successions are divided into primary-historical. Primary occur on primary soil-free soils - volcanic tuff and lava fields, loose sands, stony placers, etc. As the phytocenosis develops from the pioneer stage to saturated soil, it becomes more fertile and more and more chemical elements are involved in the biological cycle in increasing quantities. With increasing fertility, plant species developing on nutrient-rich soils displace less demanding species in this regard. At the same time, the animal population is also changing. Secondary successions occur in habitats of destroyed communities, where soils and some living organisms have been preserved. Secondary successions are characteristic of degraded pastures, fires, deforestation, excluded from agricultural use of arable land and other lands. as well as for artificial plantations. For example, often under the canopy of middle-aged pine crops on sandy loam soils, abundant natural regeneration of spruce begins, which eventually displaces the pine, provided that the next clear felling of the pine stand and forest cultivation are not carried out.

The change of one biocenosis to another during succession forms a succession series, or series. The study of succession series is of great importance in connection with the increasing anthropogenic impact on biocenoses. The end result of this kind of research can be the prediction of the formation of natural anthropogenic landscapes. The study of secondary succession and the factors causing them plays an important role in solving the problems of the protection and rational use of biological and land resources.

If the natural course of succession is not disturbed, the community gradually comes to a relatively stable state in which equilibrium is maintained between organisms, as well as between them and the environment, to menopause. Without human intervention, this biocenosis can exist indefinitely, for example, blueberry pine, lichen tundra on sandy soils.

The concept of menopause was developed in detail by the American botanist X. Cowles and is widely used in foreign botanical and geographical literature. According to this concept, menopause is the terminal stage in the evolution of the community, to which the soil of a certain type corresponds - pedoclimax. Successions leading to this stage are called progressive, and those that remove the biocenosis from it are called regressive.

Biocenoses, which, when violated, return to their original state, are called indigenous.

Transformed biocenoses do not return to their original state.

Succession. Ecosystem Succession Examples

Succession

Types of Successions

Secondary succession

Types of Succession Changes

Succession duration

Ecosystem Succession Examples

Communities are constantly changing. Their species composition, the number of various organisms, trophic structure, and other indicators of the community are changing.

Community change over time.

Succession is a sequential, regular change of some communities by others in a certain part of the territory, due to internal factors of ecosystem development.

In order to understand the nature of ecological succession, imagine an IDEAL community (that is, the total production of autotrophs in energy terms exactly corresponds to the energy costs that go towards ensuring the vital activity of its constituent organisms).

In ecology, total energy costs are called - the general breath of the community.

It is clear that in such an ideal case, the processes of production are balanced by the processes of respiration.

Consequently, the biomass of organisms in such a system remains constant, and the system itself is unchanged or equilibrium.

If the "general respiration" is less than the primary gross output - an accumulation of organic matter will occur in the ecosystem;

If more - its decrease.

In both the first and second cases, community changes will occur.

With an excess of the resource, there will always be species — which can master it, and with a deficiency — some of the species will die out.

Such a change is the essence of ecological succession

The main feature of this process is that community changes always occur in the direction of the equilibrium state.

1.1 Types of succession

Succession, which begins at a place deprived of life (for example, on a newly formed sand dune), is called primary succession.

In nature, primary successions are relatively rare and last much longer than secondary ones - up to several centuries.

Primary succession - this is the overgrowing of a place not previously occupied by vegetation: bare rocks or frozen volcanic lava.

Example:

Community formation on a bare rock section, a section of frozen volcanic lava, on a newly formed sand dune or after glacier retreat.

Only a few plants are able to live on such soil; they are called the pioneers of successions. Typical pioneers are mosses and lichens. They change the soil, releasing acid, which destroys and loosens stones. Dying mosses and lichens under the influence of bacteria - reducers decompose, and their remnants are mixed with loose stony substrate (sand).

This forms the first soil on which other plants can already grow. The need to destroy the parent rock - main reason slow progress of primary successions; note the increase in soil thickness as succession occurs.

On soil that is poor in nutrients, grasses settle that are more specifically capable and crowd out lichens and mosses. Grass roots penetrate rock fissures, push these cracks apart and destroy the stone more and more.

Herbs are replaced by perennial plants and shrubs, such as alder and willow. There are nodules on alder roots - special organs containing symbiotic bacteria that fix atmospheric nitrogen and contribute to the accumulation of large reserves in the soil, due to which the soil becomes more fertile.

Now, trees, such as pine, birch and spruce, can already grow on it.

Thus, the driving force behind succession is that plants change the soil beneath them, affecting its physical properties and chemical composition, so that it becomes suitable for competing species that displace the original inhabitants, causing a change of community - succession, due to plant competition they do not always live where conditions are better for them.

The course of primary successions takes place in several stages.

For example, in a forest zone: dry lifeless substrate - lichens, mosses - annual forbs - grasses and perennial grasses - shrubs - trees of the 1st generation - trees of the 2nd generation; in the steppe zone, succession ends at the stage of grasses, etc.

1.2 Secondary succession

The term “secondary succession” refers to communities that develop in place of a pre-existing community.

In places where the economic activities of people do not interfere with the relationships of organisms, a climax community develops that can exist indefinitely - until some external influence (plowing, logging, fire, volcanic eruption, flood) violates its natural structure.

In the event of a community destruction, succession begins in it - a slow process of restoration of the initial state.

Examples of secondary successions: overgrowing of an abandoned field, meadow, burning or logging.

Secondary succession lasts several decades.

It begins with the appearance of annual herbaceous plants on the liberated patch of soil. These are typical weeds: dandelion, sow thistle, coltsfoot and others. Their advantage is that they grow quickly and produce seeds adapted to spread over long distances with the help of wind or animals.

However, after two or three years they are replaced by competitors - perennial grasses, and then - shrubs and trees, primarily aspen.

These rocks obscure the ground, and their vast root systems take all the moisture out of the soil, so it becomes difficult for seedlings of the species that first hit the field to grow.

However, succession does not stop there; a pine appears behind the aspen; and the last - slowly growing shade-tolerant species, such as spruce or oak. A hundred years later, on this site, the community that was on the site of the field to the attention of the forest and plowing is being restored.

VEILIK- genus of perennials herbaceous plants Cereals, or Bluegrass families

Fig. 8.7. Secondary succession of the Siberian dark coniferous forest (fir-cedar taiga) after a devastating forest fire.

1.4 Duration of succession

The duration of succession is largely determined by the structure of the community. A study of primary succession in places such as sand dunes suggests that, under these conditions, menopause requires many hundreds of years. Secondary successions, for example, in clearings, are much faster. Nevertheless, it takes at least 200 years for a forest to recover in a temperate, humid climate.

If the climate is especially harsh (as, for example, in the desert, tundra or in the steppe), the duration of the series is shorter, since the community cannot significantly change the adverse physical environment. Secondary succession in the steppe, for example, lasts about 50 years.

The main stages of secondary succession in a temperate climate:

· The first stage of herbaceous vegetation lasts about 10 years;

· Second stage of shrubs? from 10 to 25 years;

· The third stage of deciduous trees? from 25 to 100 years;

· The fourth stage of conifers? more than 100 years.

Successions can be of various scales. They can go slowly, for millennia, or they can go fast - in a few days.

The duration of succession is largely determined by the structure of the community.

With primary succession, it takes hundreds of years to develop a sustainable community.

Pay attention!

The need to destroy the mother breed is the main reason for the slow progress of primary successions.

Secondary successions are much faster. This is because the primary community leaves behind a sufficient amount of nutrients, developed soil, which creates the conditions for the accelerated growth and development of new settlers.

Example:

In Europe at the end pliocene (3 million years ago) the ice age began. The glacier destroyed all life under its cover. He tore and smoothed the soil cover, crumbled rocks. With his retreat and climate warming, vast expanses of bare, lifeless land were exposed. Gradually, it was inhabited by various plants and animals. Of course, these changes were very slow. Where the glacier destroyed rainforestscontinues their recovery to date. These sites have not yet reached a steady state. So they did not have enough to complete succession and millions of years.

The changes that led to deciduous forests were also slow. miocene (20 million years ago) to the current northern Central Asian deserts.

Successions are much faster after a forest fire, when in a certain sequence one biocenosis changes to another, which finally leads to the restoration of a stable community.

Relatively fast fouling of cliffs occurs: sections of rock as a result of erosion or landslide.

The fastest successions are observed in a temporary reservoir or when changing communities in the decomposing corpse of an animal, in a rotting tree trunk, in a hay infusion.

General patterns of succession

IN general view The phenomenon of ecological succession can be characterized by the following provisions:

Succession is a natural process, the course of which can be foreseen.

Succession is the result of changes made by the communities themselves, that is, the process is not set from the outside.

Succession ends with the formation of a climax biocenosis, which is characterized by the greatest diversity, and, therefore, the most numerous connections between organisms.

Thus, the climax biocenosis is maximally protected from possible disturbances by external factors and is in a state of equilibrium.

The main feature of ecological succession is that community changes always occur in the direction of the equilibrium state.

When the ecosystem approaches the final stable state (climax state), in it, as in all equilibrium systems, there is a slowdown in all development processes.

Observations of successions show that some specific properties of biocenoses change in one direction, whatever the type of succession.

We formulate them.

Species of plants and animals are constantly changing.

The species diversity of organisms is increasing.

The size of organisms in the course of succession is growing.

Linear food chains dominated by herbivores turn into complex food webs. Detritious forms (consumers of dead organics) begin to play an increasing role in them.

Biological cycles are lengthening and becoming more complicated, organisms are becoming more and more environmentally specialized.

Organic matter biomass is increasing. There is a decrease in net production of the community and an increase in respiratory rate.

1.5 Significance of succession

A mature community with its great diversity, saturation with organisms, a more developed trophic structure, with balanced energy flows can withstand changes in physical factors (such as temperature, humidity) and even some types of chemical pollution to a much greater extent than the young community. However, the young community is able to produce new biomass in much larger quantities than the old. The remnants of civilizations and deserts, the occurrence of which is tied to human activities, are excellent proof that people never realized their close relationship with nature, the need to adapt to natural processes, and not to command them. Nevertheless, even the knowledge that has been accumulated at present is enough to make sure that turning our biosphere into one vast carpet of arable land is fraught with great danger. For our own protection, certain landscapes must be represented by natural communities.

Thus, a person can harvest a rich crop in the form of clean products, artificially supporting the community in the early stages of succession. Indeed, in a mature community, which is at the stage of menopause, the net annual production is spent mainly on the respiration of plants and animals and may even be zero.

On the other hand, from the point of view of a person, the stability of a community at the stage of menopause, its ability to withstand the effects of physical factors (and even control them) is a very important and highly desirable property. A person is interested in both productivity and stability of the community. To maintain human life, a balanced set of both early and mature stages of succession, which are in a state of energy and substance exchange, is needed. Excessive food created in young communities helps maintain older stages that help withstand external influences.

Arable land, for example, should be considered young succession stages. They are maintained in this condition thanks to the continuous labor of the farmer. Forests, on the other hand, are older, more diverse and more stable communities with low net output. It is imperative that people pay equal attention to both types of ecosystems. If the forest is destroyed in pursuit of temporary income from wood, water reserves will decrease and the soil will be demolished from the slopes. This will reduce district productivity. Forests are valuable to humans not only as suppliers of wood or as a source of additional space that can be occupied by cultivated plants.

Unfortunately, people are poorly aware of the consequences of environmental disruptions arising in pursuit of economic benefits. This is partly due to the fact that even environmental specialists still cannot give accurate predictions of the consequences that various disturbances of mature ecosystems lead to. The remnants of civilizations and deserts, the occurrence of which is due to human activity, are excellent proof that people never realized their close relationship with nature, the need to adapt to natural processes, and not to command them.

Nevertheless, even the knowledge that has been accumulated at present is enough to make sure that turning our biosphere into one vast carpet of arable land is fraught with great danger. For our own protection, certain landscapes must be represented by natural communities.

ATTACHMENT:

Indicate the stages of overgrowing of the reservoir from the proposed vegetation: sphagnum, sedge, bog pine, mixed forest, rosemary (sedge, sphagnum, rosemary, bog pine, mixed forest).

Distribute the succession stages in the correct order: annual plants, deciduous shrubs, perennials, coniferous trees (annual plants, perennials, shrubs, deciduous trees, conifers)

Locate the ongoing succession stages in time: populating the territory with mosses. germination of seeds of herbaceous plants, settlement with shrubs, the formation of a sustainable community, the settlement of bare rocks with lichens

1. Lichen settlement on bare rocks

2. settlement of the territory with mosses

3. seed germination of herbaceous plants

4. settlement with shrubs

5. building a sustainable community

The course of evolution (development) of the community cannot be predicted.

The most common patterns of evolution of biocenoses:

1. Species of plants and animals in the course of community development can be predicted.

2. Decreasesvariety of species of organisms.

3. Dimensions of organisms in the course of succession are declining.

4, food chains are shortened and simplified. An increasing role in them begins to play detritophages.

5. Biological cycles get complicated , organisms are becoming more environmentally specialized.

6. Biomass of organic matter during community development increases. Going on growth community clean products and slowdownrespiratory rate.

The addition of ecosystems is a dynamic process. In ecosystems, changes are constantly occurring in the state and life of their members and in the ratio of populations. The manifold changes occurring in any community are classified into two main types: cyclic and translational.

Cyclic changes communities reflects the daily, seasonal and perennial periodicity of external conditions and the manifestation of internal (endogenous) rhythms of organisms.

Daily cycles are mainly associated with rhythm natural phenomena and is strictly periodic in nature. Seasonal variability of biocenoses is expressed in changes not only in state and activity, but also quantitative ratio individual species depending on the cycles of their reproduction, seasonal migrations, the death of individual generations during the year.

The tier structure of the biocenosis is also often subject to seasonal variability: individual plant tiers can completely disappear in the corresponding seasons of the year, for example, a grassy tier consisting of annuals.

Long-term cyclicity depends on changes in meteorological conditions over the years (climatic fluctuations), uneven rainfall over years, with periodic recurrence of droughts or other external factors affecting the community (for example, the degree of river spill). In addition, long-term periodicity may be associated with features life cycle edificator plants, with the repetition of mass reproduction of animals or microorganisms pathogenic for plants, etc.

Translational changesin the community ultimately lead to a change of this community to another, with a different set of dominant species. Such shifts may be caused by factors external to the cenosis that have been operating in the same direction for a long time, for example, the drainage of bog soils increasing as a result of land reclamation, increasing pollution of water bodies, increased grazing, etc. The resulting changes in one biocenosis are called another exogenetic. Endogenetic shifts arise as a result of processes occurring within the community itself.

Successions

The sequential change of one biocenosis is called another (from lat. Succesio - sequence, change) - succession.Succession is a process of ecosystem self-development. The succession is based on the incompleteness of the biological cycle in this biocenosis. As a result of vital activity, every living organism changes its environment around itself, removing some of the substances from it and saturating it with metabolic products. With a more or less prolonged existence of populations, they change their environment in an unfavorable direction and as a result they become crowded out populations of other species for which the environmental transformations caused are environmentally beneficial. Thus, in the community there is a change in the dominant species. The successive series of gradually and naturally replacing each other in succession of communities is called succession series.

Distinguish between primary and secondary succession. Primary succession It begins in places deprived of life (on rocks, sand, cliffs). Secondary succession is a successive change of one community that existed on this substrate, another more perfect for these abiotic processes. Secondary successions occur, as a rule, faster and easier than the primary ones, since the soil profile, seeds, rudiments, and part of the former population and former ties are preserved in the disturbed habitat.

In any succession series, the pace of changes is gradually slowing down. The end result is the formation of a relatively stable stage - menopause community or menopause. The initial, pioneer groupings of species are characterized by the greatest dynamism and instability. Menopausal ecosystems are capable of long-term self-maintenance in an appropriate range of conditions, since they acquire such features of the organization of biocenoses that allow maintaining a balanced circulation of substances.

7. Artificial ecosystems: agro and urban ecosystems

A person receives a lot of products from natural systems, however, agriculture is the main source of food for him.

Agroecosystems created by man to obtain a high yield - the net production of autotrophs. Summarizing everything already said above about agroecosystems, we emphasize the following main differences from natural ones:

1. The diversity of species is sharply reduced in them: a decrease in the species of cultivated plants also reduces the species diversity of the animal population of the biocenosis; the species diversity of animals bred by humans is negligible compared to natural; Cultivated pastures (with grass replanting) are similar to agricultural fields in species diversity.

2. Species of plants and animals cultivated by humans “evolve” due to artificial selection and are uncompetitive in the fight against wild species without human support.

3. Agroecosystems receive additional energy subsidized by humans, except solar.

4. Net production (harvest) is removed from the ecosystem and does not enter the biocenosis food chain, and its partial use by pests, harvesting losses, which can also get into natural trophic chains, are completely prevented by humans.

Ecosystems of fields, orchards, pastures, kitchen gardens and other agrocenoses are simplified systems supported by humans in the early stages of succession, and they are just as unstable and incapable of self-regulation as natural pioneer communities, therefore they cannot exist without human support .

More than 50% of the world's population lives in cities today. Process urbanization - this is the growth of the urban population, the number and size of cities, the increasing role of the city in people's lives, the spread of urban lifestyle. Today, urban areas occupy 1% of the land, but concentrate 50% of the world's population, produce 80% of the gross product (GDP), and account for 80% of all emissions.

Metropolis- This is an overgrowth of cities. The interconnection of all components and phenomena of the urban and natural environment is called urban ecosystem. Urboecosystems have a specific place in geographical space. it open systemsmanaged. Their important feature is anthropocentrism.

Although the biocenosis is a rather conservative natural system, however, under the pressure of external circumstances, it can give way to another biocenosis. The successive change in time of some communities by others in a certain part of the environment is called succession (from Lat successia, succession). As a result of succession, one community is successively replaced by another without a return to its original state. Succession is caused by the interaction of organisms, mainly wounds, with each other and with the environment.

Successions are divided into primary – historical. Primary occur on primary soil-free Soils - volcanic tuff and lava fields, loose sands, rocky placers, etc. As the phytocenosis develops from the pioneer stage to saturated soil, the soil becomes more fertile and more and more chemical elements are involved in the biological cycle in increasing quantities. With increasing fertility, plant species developing on nutrient-rich soils displace less demanding species in this regard. At the same time, the animal population is also changing. Secondary successions occur in habitats of destroyed communities, where soils and some living organisms have been preserved. Destruction of biocenoses can be caused by natural processes (hurricanes, showers, floods, landslides, prolonged droughts, volcanic eruptions, etc.). as well as changes in the living environment by Organisms (for example, when a reservoir overgrows, the aquatic environment is replaced by peat deposits). Secondary successions are characteristic of degraded pastures, cottages, deforestation, excluded from agricultural use of arable land and other lands. as well as for artificial plantations. For example, often under the canopy of middle-aged pine crops on sandy loam soils, abundant natural regeneration of spruce begins, which eventually displaces the pine, provided that the next clear felling of the pine stand and forest cultivation are not carried out. In burned areas with loamy and loamy soils, pioneer vegetation from willow tea and warty birch is replaced by spruce plantations over time.

In recent decades, large-scale drainage and irrigation works have gained particular importance in changing the vegetation cover. In the swamp forests, which are in the zone of influence of the drainage channels, hygrophytes plants disappear (sedge ols, for example, are transformed into nettles). The transformation of the species composition, including the animal population, also affects forests that come to drained swamps. Irrigation land reclamation, on the contrary, promotes the active penetration of plants of the hygrophilic and mesophilic groups into waterlogged areas as a result of the accumulation of water used for irrigation. Industrial pollution of the environment also has a noticeable effect on biocenoses. All these changes are secondary successions.

The change of one biocenosis to another during succession forms a succession series, or series. The study of succession series is of great importance in connection with the increasing anthropogenic impact on biocenoses. The end result of this kind of research can be the prediction of the formation of natural and man-made landscapes. The study of secondary succession and the factors causing them plays an important role in solving the problems of the protection and rational use of biological and land resources.

If the natural course of succession is not disturbed, the community gradually comes to a relatively stable state in which equilibrium is maintained between organisms, as well as between them and the environment, to menopause. Without human intervention, this biocenosis can exist indefinitely, for example, blueberry pine, lichen tundra on sandy soils.

The concept of menopause was developed in detail by the American botanist X. Kauls and is widely used in foreign botanical and geographical literature. According to this concept, menopause is the terminal stage in the evolution of the community, to which the soil of a certain type corresponds - pedoclimax. Successions leading to this stage are called progressive, and those that remove the biocenosis from it are called regressive. It is impossible, however, to give the concept of menopause its absolute meaning and to assume that upon reaching it, the community stops developing.

Biocenoses, which, when violated, return to their original state, are called indigenous. Birch forest will grow at the place where the blueberry pine or sorrel spruce has been cut down, and it, in turn, will again be replaced by blueberry pine or sorrel spruce. In this case, we are talking about the indigenous types of forests.

Transformed biocenoses do not return to their original state. So, the lowland sedge swamp drained and developed for agricultural crops after the depletion of the peat deposit and the destruction of the drainage network with the cessation of agricultural use for some reason develops in the direction of the formation of birch or alder small forests. The zoocenosis of this small forest is different from the animal species community of the open grass swamp.

1.6 Classification

In order to scientific knowledge biocenoses and the practical application of knowledge of them, the community of organisms must be classified according to their relative dimension and complexity of organization.

The classification is designed to put their entire diversity in order with the help of a system of taxonomic categories, i.e., taxa, combining in this case groups of biocenoses with varying degrees of commonality of individual properties and characters, as well as structure and origin. In this case, a certain subordination of simple taxa to complex taxons, taxa of small (local) dimension to taxa of planetary dimension, and the gradual complication of their organization should be observed. In addition, the classification of biocenoses should take into account the presence of possible boundaries between them.

There are no special difficulties in establishing boundaries when neighboring biocenoses have clear indicative signs. For example, an upland bog with a rosemary – moss cover and a short pine stand contrasts with the surrounding pine forest community on sandy soils. The border between the forest and the meadow is also clearly visible. However, since the conditions for the existence of communities change more gradually than the communities themselves, the boundaries of biocenoses are usually blurred. The gradual transition from one phytocenosis to another with their proximity and the change of one phytocenosis to another in time is reflected in the concept of a continuum (from Latin continuum - continuous) of vegetation developed by the Soviet geobotanist L.G. Ramensky, an American ecologist P. X. Whittaker.

Borders between communities are sharper in those cases when edificators have the greatest transformative effect on the environment, for example, the boundaries between forests, formed by different tree species - pine, spruce, oak and others. In the steppes, semi-deserts, and deserts, the boundaries between communities are more gradual, since the environmentally transforming role of grassy species is less contrasting.

The classification of communities uses taxonomic categories adopted in plant geography and based on the identification of dominants and edificators, which indicates the recognition of phytocenosis as an ecological framework that determines the structure of biocenosis. The taxonomic system of communities constructed by dominants and edifiers can be expressed as follows: association - group of associations formation group of formations class of formations type of biome - biocenotic cover.

The lowest taxonomic category is association. It is a combination of homogeneous microbiocenoses with the same structure, species composition and similar relationships between organisms and between them and the environment. IN field conditions the main signs of its separation are: the same tier addition, similar mosaic (spotted, scattered), the coincidence of dominants and edificators, as well as the relative homogeneity of the habitat. The name of the association for multi-tiered communities consists of the generic names of the dominant tier dominant (condominants) and edificators in each tier, for example, juniper – mossy pine, spruce, birch and blueberry, etc. The name of complex meadow associations is formed by listing the dominant and subdominant, and the dominant is called the last , for example, edulyutichno – meadow – bluegrass association. Usually meadow associations are indicated in Latin: Ranunculus + Roa pratensis.

A group of biocenotic associations is formed by associations that differ in the composition of one of the tiers. Blueberry pine, for example, combines associations with the undergrowth of juniper, buckthorn and undergrowth of birch. The group of cereal – small-sedge – mixed-grass associations includes meadow communities with a set of the mentioned groups of meadow grasses (cereals, small sedges, forbs).

The biocenotic formation includes groups of associations. The formation is distinguished by the dominant, according to which it is called: the formation of common pine, black alder, pedunculate oak, white saxaul, cauliflower, wormwood, etc. This is the main unit of medium rank, widely used in mapping forest vegetation.