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Human economic activity has led to the formation in nature of artificial ecosystems with certain properties, which are called agrocenoses (agrobiogeocenoses or agroecosystems).

Agrocenosis (Greek agros - field) is a community of organisms living on agricultural lands occupied by crops or plantings of cultivated plants. At the same time, their structure and function are created, maintained and controlled by a person in his own interests. Examples of such ecosystems are fields, vegetable gardens, orchards, parks, artificial pastures, flower beds, etc. Communities of plants and animals artificially created by humans in marine and freshwater bodies of water can also be classified as agrocenoses.

Agricultural ecosystems occupy about 1/3 of the land area, with 10% being arable land and the rest being natural forage land. In order to manage agrocenosis, a person spends anthropogenic energy on soil cultivation, sowing high-yielding plant varieties, land reclamation, applying fertilizers and chemicals plant protection, for heating livestock buildings, etc. Management can be intensive (high energy investment) or extensive (low energy investment). However, even with an intensive management strategy, the share of anthropogenic energy in the energy budget of the ecosystem is no more than 1%. Organisms living within the agrocenosis and not related to objects economic activity people are constantly exposed to anthropogenic factors and are forced to adapt to them.

Between natural and artificial biogeocenoses, along with similarities, there are also large differences that are important to take into account in agricultural practice.

The differences between agrocenoses and biogeocenoses are (Table 1):

1. Small species diversity living organisms

One or several species (varieties) of plants are usually cultivated in the fields, which leads to a significant depletion of the species composition of animals, fungi, and bacteria. In addition, the biological uniformity of cultivated plant varieties occupying large areas(sometimes tens of thousands of hectares), is often the main reason for their mass destruction by specialized insects (for example, the Colorado potato beetle) or damage by pathogens (powdery mildew, rust, smut fungi, late blight, etc.).

2. Short power circuits

In an agrocenosis, as in a biogeocenosis, there are producers (cultivated plants and weeds), consumers (insects, voles, birds, mice, foxes, etc.), and decomposers (fungi and bacteria). At the same time, the obligatory link in the food chain is the person who cultivates the fields, gardens and harvests. But, due to the small number of species in the agrocenosis, which have a high abundance (cultivated plants, weeds, pests, pathogens), the food chains in it are short and simple.

3. Incomplete cycle of substances

In a natural biogeocenosis, the primary production of plants (harvest) is consumed in numerous food chains (networks) and returns again to the biological cycle system in the form carbon dioxide, water and mineral nutrition elements. In an agrocenosis, such a cycle of elements is sharply disrupted, since a significant part of them is irreversibly removed by humans with the harvest. Therefore, to compensate for their losses and, consequently, increase the productivity of cultivated plants, it is necessary to constantly add fertilizers to the soil.

4. Source of energy used (anthropogenic energy)

For natural biogeocenosis, the only source of energy is the Sun. At the same time, agrocenoses, in addition to solar energy, receive anthropogenic additional energy, which man spent on the production of fertilizers, chemicals against weeds, pests and diseases, on irrigation or drainage of land, etc. Without such additional energy expenditure, the long-term existence of agrocenoses is practically impossible.

5. Artificial selection

IN natural ecosystems ah exists natural selection, rejecting non-competitive species and forms of organisms and their communities in the ecosystem and thereby ensuring its main property - sustainability.

Directed by man, primarily to maximize the productivity of agricultural crops.

6. Instability

The smaller the number of species composing an agrocenosis, the less stable this ecosystem is. The least stable monoculture (wheat, rice, cotton, etc.) requires the application of fertilizers and pesticides for its existence. Among agrocenoses, the most stable are multi-species ecosystems, for example, a meadow. The instability of agrocenosis is also due to the fact that defense mechanisms producers - cultivated plants - are weaker than those of wild species, whose adaptations have been improved in the course of natural selection over millions of years.

Table 1

Comparative characteristics of natural ecosystems and agrocenoses

7. Lack of complete self-regulation

Agricultural systems are not capable of self-regulation and self-renewal, and are subject to the threat of death due to the mass reproduction of pests or pathogens. Agrocenosis is regulated by humans, and if it is not maintained, it will quickly collapse and disappear. Cultivated plants will not withstand competition with wild species and will be forced out. In place of the agrocenosis, a steppe will appear in an arid climate, and a forest in a colder and more humid climate.

Thus, in comparison with natural biogeocenoses, agrocenoses have a limited species composition of plants and animals, are not capable of self-renewal and self-regulation, are subject to the threat of death as a result of the mass reproduction of pests or pathogens, and require tireless human activity to maintain them. Their undeniable advantages compared to natural ecosystems lies in the unlimited potential for increased productivity. However, their implementation is possible only with constant, scientifically based soil care, provision of plants with moisture and mineral nutrients, and protection of plants from unfavorable abiotic and biotic factors.

Having worked through these topics, you should be able to:

1. Give definitions: “ecology”, “ecological factor”, “photoperiodism”, “ ecological niche", "habitat", "population", "biocenosis", "ecosystem", "producer", "consumer", "decomposer", "succession", "agrocenosis".
2. Give examples of photoperiodic reactions of plants and, if possible, animals.
3. Explain the difference between a population's habitat and its niche. Give examples for each of these concepts.
4. Comment on Shelford's law and be able to construct a graph of the dependence of organisms on abiotic environmental factors.
5. Describe an example of a successful biological method pest control.
6. Explain the causes of the population explosion and possible consequences, as well as the significance of the decline in fertility, which typically follows a decline in mortality.
7. Build a circuit the food chain; correctly indicate the traffic level of each component of a given ecosystem.
8. Construct a diagram of the simple cycle of the following elements: oxygen, nitrogen, carbon.
9. Describe the events that occur when the lake becomes overgrown; after deforestation.
10. Indicate the differences between agrocenosis and biocenosis.
11. Talk about the meaning and structure of the biosphere.
12. Explain how agriculture, fossil fuel use, and plastic production contribute to environmental pollution and suggest measures to prevent it.

Ivanova T.V., Kalinova G.S., Myagkova A.N. "General Biology". Moscow, "Enlightenment", 2000

• Topic 18. "Habitat. Environmental factors." Chapter 1; pp. 10-58
• Topic 19. "Populations. Types of relationships between organisms." chapter 2 §8-14; pp. 60-99; Chapter 5 § 30-33
• Topic 20. "Ecosystems." chapter 2 §15-22; pp. 106-137
• Topic 21. "Biosphere. Cycles of matter." Chapter 6 §34-42; pp. 217-290

Lecture No. 5. Artificial ecosystems

5.1 Natural and artificial ecosystems

In the biosphere, in addition to natural biogeocenoses and ecosystems, there are communities artificially created by human economic activity - anthropogenic ecosystems.

Natural ecosystems are distinguished by significant species diversity, exist for a long time, they are capable of self-regulation, and have great stability and resilience. The biomass and nutrients created in them remain and are used within the biocenoses, enriching their resources.

Artificial ecosystems - agrocenoses (fields of wheat, potatoes, vegetable gardens, farms with adjacent pastures, fish ponds, etc.) make up a small part of the land surface, but provide about 90% of food energy.

Development Agriculture Since ancient times, it has been accompanied by the complete destruction of vegetation cover over large areas in order to make room for a small number of species selected by humans that are most suitable for nutrition.

However, initially human activity in agricultural society fit into the biochemical cycle and did not change the flow of energy in the biosphere. In modern agricultural production, the use of synthesized energy during mechanical cultivation of the land, the use of fertilizers and pesticides has sharply increased. This disrupts the overall energy balance of the biosphere, which can lead to unpredictable consequences.

Comparison of natural and simplified anthropogenic ecosystems

(after Miller, 1993)

5.2 Artificial ecosystems

5.2.1 Agroecosystems

Agroecosystem(from the Greek agros - field) - a biotic community created and regularly maintained by humans in order to obtain agricultural products. Usually includes a set of organisms living on agricultural lands.

Agroecosystems include fields, orchards, vegetable gardens, vineyards, large livestock complexes with adjacent artificial pastures.

A characteristic feature of agroecosystems is low ecological reliability, but high productivity of one (several) species or varieties of cultivated plants or animals. Their main difference from natural ecosystems is their simplified structure and depleted species composition.

Agroecosystems are different from natural ecosystems a number of features:

1. The diversity of living organisms in them is sharply reduced to obtain the highest possible production.

In a rye or wheat field, in addition to the cereal monoculture, you can find only a few types of weeds. In a natural meadow, biological diversity is much higher, but biological productivity is many times lower than in a sown field.

Artificial pest control - mostly necessary condition maintaining agroecosystems. Therefore, in agricultural practice they use powerful tools suppression of the number of undesirable species: pesticides, herbicides, etc. Environmental consequences These actions lead, however, to a number of undesirable effects other than those for which they are used.

2. Species of agricultural plants and animals in agroecosystems are obtained as a result of artificial rather than natural selection, and cannot withstand the struggle for existence with wild species without human support.

As a result, there is a sharp narrowing of the genetic base of agricultural crops, which are extremely sensitive to the massive proliferation of pests and diseases.

3. Agroecosystems are more open; matter and energy are removed from them with crops, livestock products, and also as a result of soil destruction.

In natural biocenoses, primary plant production is consumed in numerous food chains and again returns to the biological cycle system in the form of carbon dioxide, water and mineral nutrition elements.

Due to the constant harvesting and disruption of soil formation processes, with long-term cultivation of monoculture on cultivated lands, a gradual decrease in soil fertility occurs. This situation in ecology is called law of diminishing returns .

Thus, for prudent and rational farming it is necessary to take into account the depletion of soil resources and maintain soil fertility with the help of improved agricultural technology, rational crop rotation and other techniques.

The change of vegetation cover in agroecosystems does not occur naturally, but by the will of man, which does not always have a good effect on the quality of the abiotic factors included in it. This is especially true for soil fertility.

Main difference agroecosystems from natural ecosystems - getting extra energy for normal functioning.

Additional energy refers to any type of energy introduced into agroecosystems. This may be the muscular strength of humans or animals, different kinds fuel for operating agricultural machinery, fertilizers, pesticides, pesticides, additional lighting, etc. The concept of “additional energy” also includes new breeds of domestic animals and varieties of cultivated plants introduced into the structure of agroecosystems.

It should be noted that agroecosystems are highly fragile communities. They are not capable of self-healing and self-regulation, and are subject to the threat of death from mass reproduction of pests or diseases.

The reason for the instability is that agrocenoses are composed of one (monoculture) or, less often, a maximum of 2–3 species. That is why any disease, any pest can destroy an agrocenosis. However, people deliberately simplify the structure of the agrocenosis in order to obtain maximum production yield. Agrocenoses, to a much greater extent than natural cenoses (forest, meadow, pastures), are susceptible to erosion, leaching, salinization and pest invasion. Without human intervention, agrocenoses of grain and vegetable crops exist for no more than a year, berry plants - 3–4, fruit crops– 20–30 years. They then disintegrate or die.

The advantage of agrocenoses Natural ecosystems are faced with the production of food necessary for humans and great opportunities for increasing productivity. However, they are implemented only with constant care for the fertility of the land, providing plants with moisture, and protecting cultivated populations, varieties and breeds of plants and animals from the adverse effects of natural flora and fauna.

All agroecosystems of fields, gardens, pasture meadows, vegetable gardens, and greenhouses artificially created in agricultural practice are systems specifically supported by humans.

In relation to the communities that develop in agroecosystems, the emphasis is gradually changing in connection with the general development of environmental knowledge. In place of ideas about the fragmentary nature of coenotic connections and the extreme simplification of agrocenoses, there emerges an understanding of their complex systemic organization, where humans significantly influence only individual links, and the entire system continues to develop according to natural laws.

From an ecological point of view, it is extremely dangerous to simplify the natural environment of humans, turning the entire landscape into an agricultural one. The main strategy for creating a highly productive and sustainable landscape should be to preserve and enhance its diversity.

Along with maintaining highly productive fields, special care should be taken to preserve protected areas that are not subject to anthropogenic impact. Reserves with rich species diversity are a source of species for communities recovering in succession.

Comparative characteristics of natural ecosystems and agroecosystems

The crop is harvested to satisfy human needs and feed livestock. Living matter accumulates for some time without being consumed. The highest productivity develops only for a short time

5.2.2.Industrial-urban ecosystems The situation is completely different in ecosystems, which include industrial-urban systems - here fuel energy completely replaces solar energy

. Compared to the flow of energy in natural ecosystems, its consumption here is two to three orders of magnitude higher.

In connection with the above, it should be noted that artificial ecosystems cannot exist without natural systems, while natural ecosystems can exist without anthropogenic ones.

Urban systems Urban system (urbosystem)

- “an unstable natural-anthropogenic system consisting of architectural and construction objects and sharply disturbed natural ecosystems” (Reimers, 1990). As the city develops, its functional zones become more and more differentiated - these are.

industrial, residential, forest park- these are areas where industrial facilities of various industries are concentrated (metallurgical, chemical, mechanical engineering, electronics, etc.). They are the main sources of pollution environment.

Residential zones- these are areas where residential buildings, administrative buildings, cultural and educational facilities, etc. are concentrated.

Forest Park - This is a green area around the city, cultivated by man, that is, adapted for mass recreation, sports, and entertainment. Its sections are also possible inside cities, but usually here city ​​parks- tree plantations in the city, occupying quite large areas and also serving citizens for recreation. Unlike natural forests and even forest parks, city parks and similar smaller plantings in the city (squares, boulevards) are not self-sustaining and self-regulating systems.

Forest park zones, city parks and other areas of territory allocated and specially adapted for people’s recreation are called recreational zones (territories, sections, etc.).

The deepening of urbanization processes leads to the complication of the city's infrastructure. Beginning to occupy a significant place transport And transport facilities(roads, gas stations, garages, service stations, railways with their complex infrastructure, including underground ones - metro; airfields with a service complex, etc.). Transport systems cross everything functional areas cities and influence the entire urban environment (urban environment).

The environment surrounding a person under these conditions, it is a set of abiotic and social environments that jointly and directly influence people and their economy. At the same time, according to N.F. Reimers (1990), it can be divided into natural environment And natural environment transformed by man(anthropogenic landscapes up to the artificial environment of people - buildings, asphalt roads, artificial lighting, etc., i.e. artificial environment).

In general, the urban environment and urban-type settlements is part technosphere, that is, the biosphere, radically transformed by man into technical and man-made objects.

In addition to the terrestrial part of the landscape, its lithogenic basis, i.e., the surface part of the lithosphere, which is usually called the geological environment, also falls into the orbit of human economic activity (E.M. Sergeev, 1979).

Geological environment- This rocks, The groundwater, which are influenced by human economic activity (Fig. 10.2).

In urban areas, in urban ecosystems, one can distinguish a group of systems that reflect the complexity of the interaction of buildings and structures with the environment, which are called natural-technical systems(Trofimov, Epishin, 1985) (Fig. 10.2). They are closely connected with anthropogenic landscapes, with their geological structure and relief.

Thus, urban systems are the concentration of population, residential and industrial buildings and structures. The existence of urban systems depends on the energy of fossil fuels and nuclear energy raw materials, and is artificially regulated and maintained by humans.

The environment of urban systems, both its geographical and geological parts, has been most strongly changed and, in fact, has become artificial, here problems of utilization and reutilization of natural resources involved in circulation, pollution and cleaning of the environment arise, here there is an increasing isolation of economic and production cycles from natural metabolism (biogeochemical turnover) and energy flow in natural ecosystems. And finally, it is here that the population density and the built environment are highest, which threaten not only human health, but also for the survival of all humanity. Human health is an indicator of the quality of this environment.

is an interaction between living and inanimate nature, which consists of living organisms and their habitat. An ecological system is a large-scale balance and connection that allows the maintenance of a population of species of living things. Nowadays, there are natural and anthropogenic ecosystems. The differences between them are that the first is created by the forces of nature, and the second with the help of humans.

The meaning of agrocenosis

Agrocenosis is an ecosystem created by human hands for the purpose of producing crops, animals and mushrooms. An agrocenosis is also called an agroecosystem. Examples of agrocenosis are:

• apple and other orchards;
• corn and sunflower fields;
• cow and sheep pastures;
• vineyards;
• vegetable gardens

Man, due to satisfying his needs and increasing population, has recently been forced to change and destroy natural ecosystems. In order to rationalize and increase the volume of agricultural crops, people create agroecosystems. Nowadays, 10% of all available land is occupied by land for growing crops, and 20% is pasture.

The difference between natural ecosystems and agrocenosis

The main differences between agrocenosis and natural ecosystems are:

• artificially created crops cannot compete in the fight against wild species and;
• agroecosystems are not adapted to self-healing, and are completely dependent on humans and without him they quickly weaken and die;
• a large number of one species in the agroecosystem contributes to the large-scale development of viruses, bacteria and harmful insects;
• There is a much greater diversity of species in nature than in human-grown crops.

Artificially created agricultural plots must be under full human control. A disadvantage of agrocenosis is the frequent increase in populations of pests and fungi, which not only harm the crop, but can also worsen the condition of the environment. The population size of a crop in an agrocenosis increases only through the use of:

• weed and pest control;
• dryland irrigation;
• drying waterlogged soil;
• replacement of crop varieties;
• fertilizers with organic and mineral substances.

In the process of creating an agroecosystem, man built completely artificial stages of development. Soil reclamation is very popular - an extensive set of measures aimed at improving natural conditions in order to obtain the maximum high level harvest. Only the correct scientific approach, monitoring soil conditions, moisture levels and mineral fertilizers are able to increase the productivity of agrocenosis in comparison with the natural ecosystem.

Negative consequences of agrocenosis

It is important for humanity to maintain a balance of agro- and natural ecosystems. People create agroecosystems to increase food supply and use them for food processing. However, the creation of artificial agroecosystems requires additional territories, so people often plow the land and thereby destroy existing natural ecosystems. This upsets the balance of wild and cultivated species of animals and plants.

The second negative role is played by pesticides, which are often used to control pests in agroecosystems. These chemicals Through water, air and insect pests they enter natural ecosystems and pollute them. In addition, excessive use of fertilizers for agroecosystems also causes groundwater problems.

• The similarity of natural ecosystems and agrocenoses;
• Differences between natural ecosystems and agrocenoses.

1. Presence of three functional groups

(producers, consumers, decomposers)

Wheat field

producers

consumers

decomposers

Similarities of agrocenosis with a natural ecosystem:

2. Availability of food webs

rider

plants

owl

caterpillars

quail

lark

fox

mouse

Food web of agrocenosis

plants

caterpillars

mouse

rider

quail

lark

fox

owl

Similarities of agrocenosis with a natural ecosystem:

3. Tiered structure

Similarities of agrocenosis with a natural ecosystem:

abiotic factors

Similarities of agrocenosis with a natural ecosystem:

4. Influence of environmental factors

biotic factors

Similarities of agrocenosis with a natural ecosystem:

4. Influence of environmental factors

anthropogenic factors

Similarities of agrocenosis with a natural ecosystem:

5. Eat often species - dominant

Species – dominant– a species that predominates in an ecosystem in terms of numbers and influence

Differences

characteristics

Natural ecosystem

1. Species diversity

Agrocenosis

Many species forming highly branched food webs

There are fewer species, the dominant species is determined by man

Differences agrocenosis and natural ecosystem:

characteristics

Natural ecosystem

2. Sustainability

Agrocenosis

Unstable, without a person dies

Stable

Differences agrocenosis and natural ecosystem:

characteristics

Natural ecosystem

3. Action of selection

Agrocenosis

Valid natural selection , more adapted individuals remain

Natural selection is weakened and in effect artificial selection , valuable individuals remain

Differences agrocenosis and natural ecosystem:

characteristics

Natural ecosystem

4. Energy source

Agrocenosis

Solar energy and human energy (watering, weeding, fertilizing, etc.)

Energy of sun

Differences agrocenosis and natural ecosystem:

characteristics

Natural ecosystem

5. Cycle of elements

Agrocenosis

Some of the elements are taken by the person with the harvest, the cycle is incomplete

Full cycle

Differences agrocenosis and natural ecosystem:

characteristics

Natural ecosystem

6. Self-regulation

Agrocenosis

Man regulates

Capable of self-regulation

Differences agrocenosis and natural ecosystem:

characteristics

Natural ecosystem

7. Productivity (creating organic matter during photosynthesis per unit time)

Agrocenosis

High thanks to man

Depends on natural conditions

Fill the table.

Natural community

Natural selection

Agrocenosis

Artificial selection

Please rate driving forces, forming natural and artificial ecosystems:

• Does not affect the ecosystem;
• Affects the ecosystem;
• The impact on the ecosystem is minimal;
• The action is aimed at achieving maximum productivity.

Species composition of the community

Natural community

Species composition

Agrocenosis

Less/more for each position.

Distribute characteristics:

General characteristic characteristic

characteristics only for only for

natural agrocenosis

ecosystems

Characteristics:

1. Inorganic substances absorbed by producers from the soil are removed from the ecosystem.

2. Presence of decomposers in the ecosystem.

3. The ecosystem quickly collapses without human intervention.

4. Presence of producers in food chains.

5. The main source of energy is the sun.

6. Inorganic substances absorbed by producers from the soil are returned to the ecosystem.

Characteristics:

7. The ecosystem is stable over time without human intervention.

8. Part of energy or chemical substances can be artificially introduced by humans.

9. Humans have little influence on the circulation of substances.

10. Characterized by a variety of ecological niches.

11. Presence of consumers in food chains.

12. Required element the food chain is man.

Natural ecosystems and man-made agrocenoses have General characteristics: _____________________.

The differences are due to _________________

____________________________________.