The natural community - biocenosis - has species, ecological and spatial structures.

species structure- one of the most important signs of biocenosis. Its main indicators are species composition- number of species and population size- quantitative ratio of individuals.

Each specific biocenosis is characterized by a certain species composition. At the same time, some types of biocenosis can be represented by numerous populations, while others can be small. The number of species in the biocenosis per unit area is called its species richness. The species that dominate the biocenosis are called dominants(from lat. dominantie - dominant). For example, in spruce forests, spruce dominates among the trees, in the grass cover - oxalis or green mosses, and among birds - the kinglet or robin.

Along with dominants in biocenoses, species are distinguished - edificators(from lat. aedificator - builder). Edificators are the builders of the biocenosis, i.e., species that greatly change the environment and thereby create certain conditions for the life of other species of this biocenosis. Usually, the dominant species is also an edificator. For example, spruce in a spruce forest, along with dominance, has high edificatory properties. This is expressed in its ability to strongly shade the soil, create an acidic environment with its root secretions and form podzolic soils. Due to the high edificatory properties of spruce, only shade-tolerant and shade-loving plant species can live under its canopy. Under the canopy of a spruce forest, blueberries can be dominant, but they are not an edificator. In pine forests, pine is the edificator. But, compared to spruce, it is a weaker edificator, because the pine forest is relatively light and sparse. On sphagnum peatlands, sphagnum mosses are edificators, in oak forests - oak, in feather grass steppe - feather grass, etc.

According to the total number of species and their ratio, the species diversity of the biocenosis is judged. Species diversity is a sign of ecological diversity: the more species, the more ecological niches in a given community.

Ecological structure of biocenosis- this is the ratio of ecological groups of organisms that perform certain functions in the community in each ecological niche. Each biocenosis is composed of certain ecological groups of organisms. For example, sclerophytes and succulents dominate in dry arid conditions, while hygrophytes dominate in humid areas.

The ecological structure of the biocenosis is also reflected by the ratio of groups of organisms united by a similar type of nutrition. For example, saprophages predominate in forests, phytophages prevail in the steppes, and predators and detritivores predominate in the depths of the World Ocean. Biocenoses with a similar ecological structure may have a different species composition, since in them the same ecological niches can be occupied by ecologically similar, but not related species. Such species perform the same functions in similar biocenoses and are called vicarious or substitutes. For example, vicarious species are saigas in the steppes of Kazakhstan, antelopes in the savannahs of Africa, bison in the prairies of America, kangaroos in the savannahs of Australia. They occupy similar ecological niches and perform the same functions.

Spatial structure expressed in the horizontal and vertical division of the phytocenosis into separate elements, each of which plays its role in the accumulation and transformation of matter and energy. Vertically, the plant community is divided into tiers- horizontal layers, strata, in which the above-ground and underground parts of plants of certain life forms are located. Layering is especially pronounced in forest phytocenoses, where up to six layers are distinguished:

I tier - trees of the first size (spruce, pine, birch, linden, maple, oak);

II tier - trees of the second magnitude (mountain ash, bird cherry, willow);

III tier - shrubs (hazel, wild rose, euonymus, honeysuckle);

IV tier - shrubs and tall grasses (ledum, heather, blueberries, Ivan-tea);

V tier - small grasses (sour, sedge, European hoof, etc.); *

Tier VI - mosses, ground lichens, liverworts. Low-level communities (meadow, steppe, swamp) have

two or three tiers. The underground parts of plants are also tiered. The roots of trees penetrate deeper than those of shrubs, the roots of herbaceous plants are located closer to the surface, and directly on it are moss rhizoids. At the same time, there are much more roots in the surface layers of the soil than in the deep ones.

Due to layering, various plants, especially their nutritional organs (leaves), are located at different heights and therefore easily coexist in the community. Thus, the tiers determine the composition and structure of the phytocenosis. If there are few of them, then the plant community is called simple, if a lot difficult.

Plants of each tier and the microclimate caused by them create a certain environment for animals and microorganisms. For example, bacteria, fungi, insects, mites, and worms live in the soil layer of the forest. Higher tiers are occupied by herbivorous insects, birds, and mammals. At the same time, birds live in a strictly defined layer, especially during the nesting period. So, species that nest only on the ground include chicken, oatmeal, black grouse. Song thrushes, warblers, bullfinches live in the shrub layer, and finches, kinglets, goldfinches, birds of prey and others live in the crowns of trees.

The animal population of the biocenosis (zoocenosis), being confined to plants, is also distributed over tiers. For example, among insects, the following groups are distinguished:

Geobium - inhabitants of the soil;

Herpetobium - insects of the ground surface layer;

Bryobium - inhabitants of the moss layer;

Phillobius - inhabitants of the herbage;

Aerobium - inhabitants of higher tiers.

In aquatic communities, the vertical layered structure is primarily determined by external conditions, namely, light and temperature regimes. For example, in the aquatic community, the following tiers are distinguished:

Semi-submerged plants;

Rooting plants with floating leaves;

underwater plants;

Bottom plants.

Animal and plant species of different tiers are distinguished by their relation to environmental conditions. Thus, the plants of each underlying tier are more shade tolerant than those located above them. Types of different tiers in the biocenosis are in close relationship and interdependence. Plants of the lower tiers have a positive effect on the animal population both in quantitative and qualitative ratios.

The tier can be considered as a structural unit of the biocenosis, which differs from other parts of it by certain environmental conditions, a set of plants, animals and microorganisms. Each tier has its own system of relationships between its constituent components.

The vertical distribution of organisms in the biocenosis also determines a certain structure in the horizontal direction.

The horizontal structure of biocenoses is expressed by their mosaic and is realized in the form of an uneven distribution of populations of individual species over the area. This is determined, on the one hand, by the unequal soil conditions and microclimate, and, on the other hand, by the relationships of individual individuals both within the population and among themselves. On this basis, various kinds of microgroups are formed, in which species populations are interconnected by closer functional relationships than with the rest of the biocenosis.

dual (single plant), cenopopulation (populations of a species in a plant community), regional and specific.

Synusia(from the Greek synusia - coexistence, community) - spatially and ecologically delimited parts of a phytocenosis, consisting of plant species of one or more ecologically close life forms. If the tier is a morphological concept, then synusia is an ecological one. It may coincide with the tier and may be only part of it. A tier may have several synergies. The synusia reflects a mosaic of ecological factors in the formation of a plant community: pine occupies dry sandy soils, spruce occupies more humid sandy and loamy soils, birch and aspen occupy clearings, etc. For example, in the sagebrush-saltwort desert, one can distinguish synusia of early spring ephemera and synusia of summer-autumn shrubs (wormwood, saltwort); in the pine forest - synusia of cranberries and blueberries.

Parcels- these are the structural parts of the horizontal dissection of the biocenosis, differing in composition, structure, properties of the components, the specifics of their relationships and material and energy exchange. Paracellular, i.e., elementary, groupings are distinguished not only in plant populations, but also in animal populations, in contrast to the synusia and tier, which are usually considered as concepts of botany.

The spatial structure of the community is an indicator of the diversity of ecological niches in a given habitat, the richness and completeness of the use of environmental resources by the community, as well as an indicator of the relative stability of the community.

• introductory lesson for free;
• A large number of experienced teachers (native and Russian-speaking);
• Courses NOT for a specific period (month, six months, year), but for a specific number of lessons (5, 10, 20, 50);
• Over 10,000 satisfied customers.
• The cost of one lesson with a Russian-speaking teacher - from 600 rubles, with a native speaker - from 1500 rubles

The structure of the biocenosis

There are species, spatial and ecological structures of the biocenosis.

species structure – the number of species that form a given biocenosis, and the ratio of their abundance or mass. That is, the species structure of the biocenosis is determined by the species diversity and the quantitative ratio of the number of species or their mass to each other.

species diversity - the number of species in a given community. There are poor and species-rich biocenoses. Species diversity depends on the age of the community (young communities are poorer than mature ones) and on the favorableness of the main environmental factors - temperature, humidity, food resources (biocenoses of high latitudes, deserts and high mountains are poor in species).

R. Whittaker proposed to distinguish the following types of biodiversity: α -variety - species diversity in a given habitat; β -diversity - the sum of all species of all habitats in a given area; γ- diversity– diversity of landscapes (combination of α- and β- diversity).

Jaccard's laws of diversity – 1) the species diversity of the territory (γ-diversity) is directly proportional to the diversity of its environmental conditions; 2) the species richness of the community (α-diversity) grows simultaneously with the expansion of the area and decreases as the homogeneity of the latter increases.

De Candolle-Wallace's Geographic Conditioning Rule for Variations in Diversity – as you move from north to south, as a rule, there is an increase in the species diversity of communities.

Darlington's rule - reducing the area of ​​the island by 10 times, as a rule, reduces the number of animals living on it by half.

Distinguishes poor and species-rich biocenoses. In the polar arctic deserts and northern tundras with extreme heat deficiency, in waterless hot deserts, in water bodies heavily polluted with sewage - wherever one or several environmental factors deviate far from the average level that is optimal for life, communities are severely depleted. The species spectrum is also small in those biocenoses that are often subjected to some kind of catastrophic impact, for example, annual flooding due to river floods or regular destruction of vegetation during plowing, the use of herbicides and other anthropogenic interventions. Conversely, wherever the conditions of the abiotic environment approach the optimal average for life, extremely species-rich communities emerge. Tropical forests, coral reefs with their diverse population, river valleys in arid regions, etc., can serve as examples.

The species composition of biocenoses, in addition, depends on the duration of their existence, the history of each biocenosis. Young, just emerging communities usually include a smaller set of species than long-established, mature ones. Biocenoses created by man (fields, gardens, orchards) are also poorer in species than natural systems similar to them (forest steppe, meadow).

However, even the most depleted biocenoses include, according to at least hundreds of species of organisms belonging to different systematic and ecological groups. In addition to wheat, the agrocenosis of a wheat field includes, at least in a minimal amount, a variety of weeds, insect pests of wheat and predators that feed on phytophages, mouse-like rodents, invertebrates - inhabitants of the soil and the ground layer, microscopic organisms, pathogenic fungi and many others. Species-rich natural communities include thousands and even tens of thousands of species, united by a complex system of diverse relationships.

They have a high species diversity ecotones – transitional zones between communities, and an increase in species diversity here is called edge effect. It is well known that the forest edges are usually more lush and richer in vegetation, more species of birds nest, more species of insects, spiders, etc. are found than in the depths of the forest. Here, the conditions of illumination, humidity, and temperature are more diverse (forest-tundra, forest-steppe).

The significance of an individual species in the species structure of the biocenosis is judged by several indicators: the abundance of the species, the frequency of occurrence and the degree of dominance. The abundance of the species the number or mass of individuals of a given species per unit area or volume of space it occupies. Frequency of occurrence - percentage of the number of samples or sites where the species occurs to the total number of samples or sites. It characterizes the uniformity or uneven distribution of the species in the biocenosis. The degree of dominance - the ratio of the number of individuals of a given species to the total number of all individuals of the group under consideration. Diversity Index calculated by Shannon's formula H=-Σ pi log2 pi, where Σ is the sign of the sum, pi- the share of each species in the communities (in terms of abundance or mass), and log2 pi is the binary logarithm.

The following types are distinguished in the community: dominant , dominant in number, and "minor" few and rare. Among the dominants are highlighted edificators (builders) are species that determine the microenvironment (microclimate) of the entire community. As a rule, these are plants.

Dominants dominate the community and constitute the "species core" of any biocenosis. Dominant, or mass, species determine its appearance, maintain the main connections, and influence the habitat to the greatest extent. Typically, typical terrestrial biocenoses are named according to the dominant plant species: blueberry pine forest, hairy sedge birch forest, etc. Certain types of animals, fungi and microorganisms also dominate in each of them.

The main edificators of terrestrial biocenoses are certain types of plants: in spruce forests - spruce, in pine forests - pine, in the steppes - sod grasses (feather grass, fescue, etc.). However, in some cases, animals can also be edificators. For example, in territories occupied by marmot colonies, it is their burrowing activity that mainly determines the nature of the landscape and the conditions for plant growth. In the seas, typical edificators among animals are reef-building coral polyps.

In addition to a relatively small number of dominant species, the biocenosis usually includes many small and even rare forms. They are also very important for the life of the biocenosis. They create its species richness, increase the diversity of biocenotic relationships and serve as a reserve for replenishment and replacement of dominants, that is, they give stability to the biocenosis and ensure the reliability of its functioning under different conditions.

With a decrease in the number of species, the abundance of individual forms usually sharply increases. In such impoverished communities, biocenotic ties are weakened and some of the most competitive species are able to reproduce freely.

ruleTineman - the more specific the environmental conditions, the poorer the species composition of the community and the higher the number of individual species can be. In species-poor biocenoses, the abundance of individual species can be extremely high. Suffice it to recall outbreaks of mass reproduction of lemmings in the tundra or insect pests in agrocenoses.

In the richest biocenoses, almost all species are few in number. In tropical forests, it is rare to find several trees of the same species side by side. In such communities, outbreaks of mass reproduction of individual species do not occur, and biocenoses are highly stable.

Spatial structure – distribution of organisms of different species in space (vertically and horizontally). The spatial structure is formed primarily by the plant part of the biocenosis. Distinguish layering (vertical structure of the biocenosis) and mosaic (the structure of the biocenosis horizontally).

Layering is especially noticeable in temperate forests. For example, in spruce forests, tree, grass-shrub and moss layers are clearly distinguished. Five or six tiers can also be distinguished in the broad-leaved forest.

In the forests there is always inter-tiered (extra-tiered) plants - these are algae and lichens on tree trunks and branches, higher spore and flowering epiphytes, creepers, etc.

Layering is also expressed in herbaceous communities (meadows, steppes, savannahs), but not always clearly enough.

Animals are also predominantly confined to one or another layer of vegetation. Some of them do not leave the corresponding tier at all. For example, among insects, the following groups are distinguished: inhabitants of the soil - geobium, ground, surface layer - herpetobium, moss layer - bryobium, herbage - phyllobium, higher tiers - aerobium. Among the birds there are species that nest only on the ground (chicken, black grouse, skates, buntings, etc.), others - in the shrub layer (singing thrushes, bullfinches, warblers) or in the crowns of trees (finches, kinglets, goldfinches, large predators, etc. .).

Dissection in the horizontal direction - mosaic - characteristic of almost all phytocenoses, therefore, within them, structural units are distinguished, which have received different names: microgroups, microcenoses, microphytocenoses, parcels, etc.

ecological structure – ratio of organisms of different ecological groups. Biocenoses with a similar ecological structure may have a different species composition. This is due to the fact that the same ecological niches can be occupied by ecologically similar but far from related species. Such types are called replacing or vicarious .

The ecological structure of communities is also reflected by the ratio of such groups of organisms as hygrophytes, mesophytes and xerophytes among plants or hygrophiles, mesophiles and xerophiles among animals, as well as the spectra of life forms. It is quite natural that in dry arid conditions, vegetation is characterized by the predominance of sclerophytes and succulents, while in highly humid biotopes, hygro- and even hydrophytes are richer.

Important characteristics of the structure of the biocenosis are consortia, synusia and parcel. consortium – a structural unit of a biocenosis that unites autotrophic and heterotrophic organisms on the basis of spatial (topical) and nutritional (trophic) links around the central member (nucleus). For example, a single tree or a group of trees (an edificator plant) and organisms associated with it. Biocenosis is a system of interconnected consortia.

Synusia – a structural part in the vertical division of the biocenosis, formed by species similar in life form and limited in space (or in time). Spatially, synusia can coincide with the horizon, canopy, layer, tier of biogeocenosis. For example, in a pine forest, one can distinguish pine synusia, lingonberry sinusia, green moss synusia, etc.

Parcel – a structural part in the horizontal dissection of the biocenosis, which differs from other parts in the composition and properties of the components. The parcel is isolated (limited) according to the leading element of vegetation. For example, areas of broad-leaved trees in a coniferous forest.

For the first time, the term "biocenosis" was used in his work by Carl Moebius in 1877 to describe all organisms that inhabit the territory and interact with each other. He combined the Greek words "βίος" - life and "κοινός" - common into one, which formed the basis of the concepts of "spatial structure of the biocenosis" and many others.

Animals, vegetation and microorganisms, in all their diversity, living and growing on a certain territory, marked by conditional boundaries, are called biocenosis. In addition, all living things are influenced by the environment, that is, the organic interacts with the inorganic. And this is happening and has been happening for a long period of time.

Even an inattentive observer will notice that animals and plants, microorganisms, are distributed or distributed over the territory they occupy, in width and height. This distribution is called spatial.

In addition, all living organisms that exist in this area have species diversity. All these species together or their combination is the species structure of the biocenosis.

No one doubts that in the process of living together on a common natural site, all its inhabitants interact with each other. The most common form of such interaction is eating one another. A cat is a bird or a mouse. The mouse is a grain.

A grain, during growth, consumes useful substances from the earth, and they are obtained when the worms “recycle” all the previous ones after their death. The worm is eaten by the bird. And so in a circle. Such a cycle is the trophic structure of the biocenosis. A cat, a mouse, a bird, a grain and others are links, and all together a trophic chain.

Thus, the ecological structure of the biocenosis has three types.

The structure that characterizes its spatial content is divided into two types.

The height distribution is a vertical or tiered structure. Distribution across the width or in the plane - horizontal or mosaic.

The tiers are most pronounced in plants and represent their species distribution in layers located at different distances from the ground. On this basis, plants are divided into shade-tolerant and photophilous. If you list, starting from the ground and up, that is, moss-lichen, shrub-herb, shrub and tree tiers.

We can talk about the tiers of habitat in insects. Here the principle of distribution of species is as follows: the inhabitants of the soil, its surface layer, mosses, herbage, and the last - the topmost.

For animals and birds, longlines are practically not expressed.

The horizontal structure, that is, a planar cut at each of the vertical levels, is characterized by species diversity or mosaic. The occupancy of each such layer by living organisms depends on several factors. This is the influence of the surrounding inanimate nature or an abiogenic factor. The vegetation of this horizon. The combined influence of inanimate nature and the plant world. And the last factor inherent near the soil level is the diversity that arose as a result of the vital activity of burrowing animals.

The species structure of the biocenosis, that is, the totality of all types of flora and fauna, is formed depending on various factors. There are communities with a predominance of animal species, and there are plant species. And the set of species itself can change. The most famous such change can be considered a decrease in species diversity from topical zones to the poles of the Earth. As we approach the "tops" of the planet, the number of species, both plants and animals, is reduced.

A prime example would be the diversity of species in rainforests. For example, in the Amazon River basin, they can be counted only in trees up to 90 per 1 ha. While in temperate latitudes, the same trees will have no more than 10 of them. At the junction of the taiga and tundra zones, there will be a maximum of 5. And there will be no trees at all in the arctic zone or the alpine highlands. The same picture in the world of animals and microorganisms.

This structure is characterized not only by the number of species, but also by the number of individuals in each species. This indicates the richness of the biocenosis and is its qualitative characteristic. The species that has the largest number of individuals, has the greatest biomass or productivity is called dominant or dominant. This is especially clearly illustrated by the spruce forest, where trees of this species fill the entire territory and shade, preventing other vegetation from developing.

The competition that arises between two species leads to the displacement of one from the habitat halo by the other. This principle of competitive exclusion, based on the results of his observations and research, was formulated by G.F. Gause.

Trophic

The trophic structure is based on three groups of organisms.

The first is producers, that is, producing. These are organisms that produce or synthesize organic substances from water and carbon dioxide, that is, from inorganic substances. They use solar energy as a source. The term "producer" means, as a rule, green plants, which make up about 99% of all life on Earth. Green plants are the basis of the ecological pyramid and its first link.

The third group is decomposers or reducing agents. These include organisms that break down dead organic matter and turn it into inorganic matter. In the food chain above, they were worms. In addition to them, decomposers are protozoa, fungi, bacteria and other microorganisms. As a result of their activity, organic residues are converted into CO2, H2O and simple salts. This is how the food chain ends and starts again.

In the biocenosis, trophic links between producers, consumers and decomposers must be permanent and uninterrupted. If they break or at least slow down or stop in time, then this can lead to the death of the entire biocenosis.

Peculiarities

Any of the described structures is not stable and unchanging. Their boundaries are arbitrary. Living organisms from one layer or horizontal cut can flow or affect another. Starting life on one level and ending it on another. An example would be insects whose larvae develop in water or soil, while they themselves live and die in the upper tiers.

The ecological structure of the biocenosis stands somewhat apart, because it is based on the principle of adaptation of species to various circumstances. For example, to nutrition, appearance, environment, size, and so on. The peculiarity is that these circumstances or conditions are natural, and can be created and shaped by man. The presence of natural and artificial factors predetermines the quantity and quality of species occupying a certain territory or ecological niche.

An inorganic or inanimate environment that forms a homogeneous space for living organisms is called a biotope, the size of which can be very different. The ecological type of biocenosis is considered inextricably linked with the biotope.

Watch the video: Ecological structure of biocenosis.

BIOTIC COMMUNITIES

When it comes to ecosystems, biotic community commonly understood biocenosis, because the community is the population biotope- places of life of the biocenosis.

Biocenosis- ϶ᴛᴏ need-organismal system, consisting of three components: vegetation, animals and microorganisms. In such a system, individual species, populations, and groups of species can be replaced, respectively, by others without much damage to the community, and the system itself exists by balancing the forces of antagonism between species. The stability of the community is determined by the quantitative regulation of the number of some species by others, and its size depends on external factors - on the size of the territory with homogeneous abiotic properties, i.e. on the size of the territory. e. biotope. Functioning in continuous unity, biocenosis and biotope form biogeocenosis, or ecosystem. The boundaries of the biocenosis coincide with the boundaries of the biotope and, therefore, with the boundaries ecosystems. Biotic community (biocenosis) - a higher level of organization than the population, which is its integral part. Biocenosis has a complex internal structure. Allocate species and spatial structures of biocenoses.

It is important to note that for the existence of a community, not only the size of the number of organisms is important, but even more important is the species diversity, ĸᴏᴛᴏᴩᴏᴇ is the basis of biological diversity in wildlife. According to the Convention on Biological Diversity of the United Nations Conference on Environment and Development (Rio de Janeiro, 1992), under biodiversity It is customary to understand diversity within a species, between species, and the diversity of ecosystems.

Diversity within a species is the basis for stability in the development of populations, diversity between species and, consequently, populations is the basis for the existence of a biocenosis as the main part of an ecosystem.

species structure biocenosis is characterized by species diversity and the quantitative ratio of species, depending on a number of factors. The main limiting factors are temperature, humidity and lack of food resources. For this reason, biocenoses (communities) of ecosystems of high latitudes, deserts and high mountains are the poorest in species. Organisms whose life forms are adapted to such conditions can survive here. Biocenoses rich in species are tropical forests, with a diverse fauna and where it is difficult to find even two trees of the same species standing side by side.

Usually, natural biocenoses are considered poor in species if they contain tens and hundreds of plant and animal species, rich - ϶ᴛᴏ several thousand or tens of thousands of species. Species richness The composition of biocenoses is determined either by the relative or absolute number of species and depends on the age of the community: young, just starting to develop, are poor in species compared to mature or climax communities.

Species diversity– this is the number of species in a given community or region, i.e., it has a more specific content and is one of the most important both qualitative and quantitative characteristics of ecosystem stability. It is interconnected with a variety of environmental conditions. The more organisms find in a given biotope suitable conditions for themselves according to environmental requirements, the more species will settle in it.

The species diversity in a given habitat is called α- variety, and the sum of all species living in all habitats within a given region, β -diversity. Indicators for the quantitative assessment of species diversity, diversity indices are usually the ratio between the number of species, their numbers, biomass, productivity, etc., or the ratio of the number of species to unit area.

An important indicator is the quantitative ratio of the number of species to each other. It is one thing when five species are contained among a hundred individuals in a ratio of 96:1:1:1:1, and another if they are related as 20:20:20:20:20. The latter ratio is clearly preferable, since the first grouping is much more uniform.

The most favorable conditions for the existence of many species are characteristic of transitional zones between communities, which are called tokens, and the trend towards an increase in species diversity here is called edge effect.

The ecotone is rich in species, primarily because they come here from all border communities, but, in addition, it may contain its own characteristic species that are not found in such communities. A vivid example of this is the forest "edge", on which the vegetation is more lush and richer, much more birds nest, more insects, etc., than in the depths of the forest.

Species that dominate in numbers are called dominant or simply - the dominants of this community. But among them there are those without which other species cannot exist. They are called edificators(lat. - "builders"). Οʜᴎ determine the microenvironment (microclimate) of the entire community, and their removal threatens to completely destroy the biocenosis. As a rule, plants - spruce, pine, cedar, feather grass, and only occasionally - animals (marmots) act as edificators.

"Minor" species - few and even rare - are also very important in the community. Their predominance is ϶ᴛᴏ a guarantee of the sustainable development of communities. In the richest biocenoses, almost all species are few in number, but the poorer the species composition, the more dominant species. Under certain conditions, there are "outbreaks" in the number of individual dominants.

To assess diversity, other indicators are also used, which significantly complement the above. The abundance of the species- the number of individuals of a given species per unit area or volume of space occupied by them. The degree of dominance - the ratio (usually in percent) of the number of individuals of a given species to the total number of all individuals of the group under consideration.

At the same time, the assessment of the biodiversity of the biocenosis as a whole in terms of the number of species will be incorrect if we do not take into account organism sizes. After all, the biocenosis includes both bacteria and macroorganisms. For this reason, it is extremely important to combine organisms into groups that are close in size. Here you can also approach from the point of view of taxonomy (birds, insects, Asteraceae, etc.), ecological and morphological (trees, grasses, mosses, etc.), or in general in terms of size (microfauna, mesofauna and macrofauna of soils or silts, etc.). . P.). At the same time, it should be borne in mind that within the biocenosis there are also special structural associations - consortia. consortium- a group of heterogeneous organisms that settle on the body or in the body of an individual of any particular species - central member consortia - capable of creating a certain microenvironment around itself. Other members of the consortium can create smaller consortia, etc., i.e., consortia of the first, second, third, etc. order can be distinguished. Hence it is clear that biocenosis - ϶ᴛᴏ system of interconnected consortia.

Most often, the central members of the consortium are plants. Consortia arise on the basis of close diverse relationships between species (Fig. 4.1).

In nature, all living organisms are in constant relationship with each other. What is it called? Biocenosis is an established set of microorganisms, fungi, plants and animals, which has historically formed in a relatively homogeneous living space. Moreover, all these living organisms are connected not only with each other, but also with their environment. Biocenosis can exist both on land and in water.

Origin of the term

The concept was first used by the famous German botanist and zoologist Karl Möbius in 1877. He used it to describe the totality and relationships of organisms inhabiting a certain area, which is called a biotope. Biocenosis is one of the main objects of study of modern ecology.

The essence of relationships

Biocenosis is a relationship that has arisen on the basis of a biogenic cycle. It is he who provides it in specific conditions. What is the structure of the biocenosis? This dynamic and self-regulating system consists of the following interrelated components:

• Producers (aphtotrophs), which are producers of organic substances from inorganic ones. Some bacteria and plants in the process of photosynthesis convert solar energy and synthesize organic matter, which is consumed by living organisms, called heterotrophs (consumers, decomposers). Producers capture carbon dioxide from the atmosphere, which is emitted by other organisms, and produce oxygen.
• Consumers, which are the main consumers of organic substances. Herbivores eat plant foods, which in turn become a meal for carnivorous predators. Due to the process of digestion, consumers carry out the primary grinding of organic matter. This is the initial stage of its disintegration.
• Decomposers, finally decomposing organic substances. They dispose of waste and corpses of producers and consumers. Decomposers are bacteria and fungi. The result of their vital activity is mineral substances, which are again consumed by producers.

Thus, it is possible to trace all the connections in the biocenosis.

Basic concepts

All members of the community of living organisms are usually called certain terms derived from Greek words:

• the totality of plants in a particular area, - phytocenosis;
• all types of animals living within the same area - zoocenosis;
• all microorganisms living in the biocenosis - microbiocenosis;
• fungal community - mycocenosis.

Quantitative indicators

The most important quantitative indicators of biocenoses:

• biomass, which is the total mass of all living organisms in specific natural conditions;
• biodiversity, which is the total number of species in the biocenosis.

Biotope and biocenosis

In the scientific literature, such terms as "biotope", "biocenosis" are often used. What do they mean and how do they differ from each other? In fact, the totality of living organisms included in a particular ecological system is commonly called a biotic community. Biocenosis has the same definition. This is a set of populations of living organisms living in a certain geographical area. It differs from others in a number of chemical (soil, water) and physical (solar exposure, altitude, area size) indicators. A section of the abiotic environment occupied by a biocenosis is called a biotope. So both of these concepts are used to describe communities of living organisms. In other words, biotope and biocenosis are practically the same thing.

Structure

There are several types of biocenosis structures. All of them characterize it according to different criteria. These include:

• The spatial structure of the biocenosis, which is divided into 2 types: horizontal (mosaic) and vertical (tiered). It characterizes the living conditions of living organisms in specific natural conditions.
• The species structure of the biocenosis, which is responsible for a certain diversity of the biotope. It is a collection of all populations that are part of it.
• Trophic structure of biocenosis.

Mosaic and layered

The spatial structure of the biocenosis is determined by the location of living organisms of different species relative to each other in the horizontal and vertical directions. Layering ensures the most complete use of the environment and a uniform distribution of species along the vertical. Thanks to this, their maximum productivity is achieved. So, in any forests, the following tiers are distinguished:

• ground (mosses, lichens);
• grassy;
• shrubby;
• woody, including trees of the first and second magnitude.

The corresponding arrangement of animals is superimposed on the tiering. Due to the vertical structure of the biocenosis, plants most fully use the light flux. Thus, light-loving trees grow in the upper tiers, and shade-tolerant trees grow in the lower ones. Different horizons are also distinguished in the soil, depending on the degree of saturation with roots.

Under the influence of vegetation, the biocenosis of the forest creates its own microenvironment. In it, not only an increase in temperature is observed, but also a change in the gas composition of the air. Such transformations of the microenvironment favor the formation and layering of fauna, including insects, animals, and birds.

The spatial structure of the biocenosis also has a mosaic structure. This term refers to the horizontal variability of flora and fauna. Mosaic in area depends on the diversity of species and their quantitative ratio. It is also influenced by soil and landscape conditions. Often, a person creates an artificial mosaic, cutting down forests, draining swamps, etc. Because of this, new communities form in these territories.

Mosaic is inherent in almost all phytocenoses. Within them, the following structural units are distinguished:

• Consortia, which are a collection of species united by topical and trophic links and dependent on the core of this grouping (central member). Most often, its basis is a plant, and its components are microorganisms, insects, animals.
• Synusia, which are a group of species in a phytocenosis belonging to close life forms.
• Parcels, representing the structural part of the horizontal section of the biocenosis, which differs from its other components in its composition and properties.

Spatial structure of the community

A good example for understanding vertical layering in living beings are insects. Among them there are such representatives:

• soil inhabitants - geobias;
• inhabitants of the surface layer of the earth - herpetobia;
• bryobia living in mosses;
• located in the herbage of phyllobia;
• living on trees and shrubs aerobia.

Horizontal structure is caused by a number of different reasons:

• abiogenic mosaic, which includes factors of inanimate nature, such as organic and inorganic substances, climate;
• phytogenic, associated with the growth of plant organisms;
• eolian-phytogenic, which is a mosaic of abiotic and phytogenic factors;
• biogenic, associated primarily with animals that are able to dig the ground.

Species structure of biocenosis

The number of species in the biotope directly depends on the stability of the climate, the time of existence and the productivity of the biocenosis. So, for example, in a tropical forest, such a structure will be much wider than in a desert. All biotopes differ from each other in the number of species inhabiting them. The most numerous biogeocenoses are called dominant. In some of them, it is simply impossible to determine the exact number of living beings. As a rule, scientists determine the number of different species concentrated in a particular area. This indicator characterizes the species richness of the biotope.

This structure makes it possible to determine the qualitative composition of the biocenosis. When comparing territories of the same area, the species richness of the biotope is determined. In science, there is the so-called Gause principle (competitive exclusion). In accordance with it, it is believed that if in a homogeneous environment there are 2 types of similar living organisms together, then under constant conditions one of them will gradually replace the other. At the same time, they have a competitive relationship.

The species structure of the biocenosis includes 2 concepts: "wealth" and "diversity". They are somewhat different from each other. Thus, species richness is the total set of species living in a community. It is expressed by a list of all representatives of different groups of living organisms. Species diversity is an indicator that characterizes not only the composition of the biocenosis, but also the quantitative relationships between its representatives.

Scientists distinguish between poor and rich biotopes. These types of biocenosis differ among themselves in the number of representatives of communities. The age of the biotope plays an important role in this. Thus, young communities that began their formation relatively recently include a small set of species. Every year the number of living beings in it can increase. The poorest are biotopes created by man (gardens, orchards, fields).

Trophic structure

The interaction of various organisms that have their own specific place in the cycle of biological substances is called the trophic structure of the biocenosis. It consists of the following components:

Features of biocenoses

Populations and biocenoses are the subject of careful study. Thus, scientists have found that most aquatic and almost all terrestrial biotopes contain microorganisms, plants and animals. They established the following feature: the greater the difference in two neighboring biocenoses, the more heterogeneous the conditions at their boundaries. It has also been established that the abundance of a certain group of organisms in a biotope largely depends on their size. In other words, the smaller the individual, the greater the abundance of this species. It has also been established that groups of living creatures of different sizes live in a biotope on different scales of time and space. So, the life cycle of some unicellular organisms takes place within one hour, and a large animal - within decades.

Number of species

In each biotope, a group of main species is distinguished, the most numerous in each size class. It is the connections between them that are decisive for the normal life of the biocenosis. Those species that prevail in terms of numbers and productivity are considered to be the dominants of this community. They dominate it and are the core of this biotope. An example is grass bluegrass, which occupies the maximum area in a pasture. She is the main producer of this community. In the richest biocenoses, almost always all types of living organisms are few in number. So, even in the tropics, several identical trees are rarely found in one small area. Since such biotopes are distinguished by their high stability, outbreaks of mass reproduction of some representatives of the flora or fauna are rare in them.

All types of community constitute its biodiversity. The biotope has certain principles. As a rule, it consists of several main species, characterized by high abundance, and a large number of rare species, characterized by a small number of its representatives. This biodiversity is the basis for the equilibrium state of a particular ecosystem and its sustainability. It is thanks to him that a closed cycle of biogens (nutrients) occurs in the biotope.

Artificial biocenoses

Biotopes are formed not only naturally. In their life, people have long learned to create communities with properties that are useful to us. Examples of human-made biocenosis:

• man-made canals, reservoirs, ponds;
• pastures and fields for crops;
• drained swamps;
• renewable gardens, parks and groves;
• field-protective forest plantations.