Ecosystems are one of the key concepts of ecology, which is a system that includes several components: a community of animals, plants and microorganisms, a characteristic habitat, a whole system of relationships through which the interchange of substances and energies occurs. In science, there are several classifications of ecosystems. One of them divides all known ecosystems into two large classes: natural, created by nature, and artificial, those created by man.
Natural ecosystems They are characterized by: A close relationship between organic and inorganic substances. A complete, closed circle of the cycle of substances: starting from the appearance of organic matter and ending with its decay and decomposition into inorganic components. Resilience and self-healing ability.
All natural ecosystems are determined by the following characteristics: 1. Species structure: the number of each species of animal or plant is regulated by natural conditions. 2. Spatial structure: all organisms are located in a strict horizontal or vertical hierarchy. 3. Biotic and abiotic substances. The organisms that make up the ecosystem are divided into inorganic (abiotic: light, air, soil, wind, humidity, pressure) and organic (biotic animals, plants). 4. In turn, the biotic component is divided into producers, consumers and destroyers.
Artificial ecosystems Artificial ecosystems are communities of animals and plants living in the conditions that humans have created for them. They are also called noobiogeocenoses or socioecosystems. Examples: field, pasture, city, society, spaceship, zoo, garden, artificial pond, reservoir.
Comparative characteristics of natural and artificial ecosystems Natural ecosystems Artificial ecosystems The main component is solar energy. Mainly, it receives energy from fuel and prepared food (heterotrophic) Forms fertile soil Depletes the soil All natural ecosystems absorb carbon dioxide and produce oxygen Most artificial ecosystems consume oxygen and produce carbon dioxide Large species diversity Limited number of species of organisms High stability, ability for self-regulation and self-healing Weak stability, since such an ecosystem depends on human activity Closed metabolism Open metabolic chain Creates habitats for wild animals and plants Destroys wildlife habitats
Ecosystems are unified natural complexes that are formed by a combination of living organisms and their habitat. The science of ecology studies these formations.
The term “ecosystem” appeared in 1935. It was proposed to be used by the English ecologist A. Tansley. A natural or natural-anthropogenic complex in which both living and indirect components are in close relationship through metabolism and the distribution of energy flow - all this is included in the concept of “ecosystem”. There are different types of ecosystems. These basic functional units of the biosphere are divided into separate groups and studied by environmental science.
Classification by origin
There are various ecosystems on our planet. Ecosystem types are classified in a certain way. However, it is impossible to connect together all the diversity of these units of the biosphere. That is why there are several classifications of ecological systems. For example, they are distinguished by origin. This:
- Natural (natural) ecosystems. These include those complexes in which the circulation of substances occurs without any human intervention.
- Artificial (anthropogenic) ecosystems. They are created by man and are able to exist only with his direct support.
Natural ecosystems
Natural complexes that exist without human participation have their own internal classification. There are the following types of natural ecosystems based on energy:
Fully dependent on solar radiation;
Receiving energy not only from the heavenly body, but also from other natural sources.
The first of these two types of ecosystems is unproductive. Nevertheless, such natural complexes are extremely important for our planet, since they exist over vast areas and influence climate formation, clean large volumes of the atmosphere, etc.
Natural complexes that receive energy from several sources are the most productive.
Artificial biosphere units
Anthropogenic ecosystems are also different. The types of ecosystems included in this group include:
Agroecosystems that appear as a result of human agriculture;
Technoecosystems arising as a result of industrial development;
Urban ecosystems resulting from the creation of settlements.
All these are types of anthropogenic ecosystems created with the direct participation of humans.
Diversity of natural components of the biosphere
There are different types and types of natural ecosystems. Moreover, ecologists distinguish them based on the climatic and natural conditions of their existence. Thus, there are three groups and a number of different units of the biosphere.
Main types of natural ecosystems:
Ground;
Freshwater;
Marine.
Terrestrial natural complexes
The variety of types of terrestrial ecosystems includes:
Arctic and alpine tundra;
Coniferous boreal forests;
Deciduous massifs of the temperate zone;
Savannas and tropical grasslands;
Chaparrals, which are areas with dry summers and rainy winters;
Deserts (both shrub and grassy);
Semi-evergreen tropical forests located in areas with distinct dry and wet seasons;
Tropical evergreen rain forests.
In addition to the main types of ecosystems, there are also transitional ones. These are forest-tundras, semi-deserts, etc.
Reasons for the existence of various types of natural complexes
By what principle are various natural ecosystems located on our planet? Types of ecosystems of natural origin are located in one zone or another depending on the amount of precipitation and air temperature. It is known that the climate in different parts of the globe has significant differences. At the same time, the annual amount of precipitation is not the same. It can range from 0 to 250 or more millimeters. In this case, precipitation falls either evenly throughout all seasons, or falls mostly during a certain wet period. The average annual temperature also varies on our planet. It can range from negative values to thirty-eight degrees Celsius. The constancy of heating of air masses also varies. It may not have significant differences throughout the year, as, for example, at the equator, or it may constantly change.
Characteristics of natural complexes
The diversity of types of natural ecosystems of the terrestrial group leads to the fact that each of them has its own distinctive characteristics. So, in the tundras, which are located north of the taiga, there is a very cold climate. This area is characterized by negative average annual temperatures and polar day-night cycles. Summer in these parts lasts only a few weeks. At the same time, the ground has time to thaw to a small meter depth. Precipitation in the tundra falls less than 200-300 millimeters throughout the year. Due to such climatic conditions, these lands are poor in vegetation, represented by slowly growing lichens, moss, as well as dwarf or creeping lingonberry and blueberry bushes. At times you can meet
The fauna is not rich either. It is represented by reindeer, small burrowing mammals, as well as predators such as ermine, arctic fox and weasel. The bird world is represented by the polar owl, snow bunting and plover. Insects in the tundra are mostly dipteran species. The tundra ecosystem is very vulnerable due to its poor ability to recover.
The taiga, located in the northern regions of America and Eurasia, is very diverse. This ecosystem is characterized by cold and long winters and abundant precipitation in the form of snow. The flora is represented by evergreen coniferous tracts, in which fir and spruce, pine and larch grow. Representatives of the animal world include moose and badgers, bears and squirrels, sables and wolverines, wolves and lynxes, foxes and minks. The taiga is characterized by the presence of many lakes and swamps.
The following ecosystems are represented by broad-leaved forests. Ecosystem species of this type are found in the eastern United States, East Asia, and Western Europe. This is a seasonal climate zone, where temperatures in winter drop below zero, and between 750 and 1500 mm of precipitation falls throughout the year. The flora of such an ecosystem is represented by broad-leaved trees such as beech and oak, ash and linden. There are bushes and a thick layer of grass here. The fauna is represented by bears and moose, foxes and lynxes, squirrels and shrews. Owls and woodpeckers, blackbirds and falcons live in such an ecosystem.
Temperate steppe zones are found in Eurasia and North America. Their analogues are tussocks in New Zealand, as well as pampas in South America. The climate in these areas is seasonal. In summer, the air heats up from moderately warm to very high values. Winter temperatures are negative. During the year, there is from 250 to 750 millimeters of precipitation. The flora of the steppes is represented mainly by turf grasses. Animals include bison and antelope, saigas and gophers, rabbits and marmots, wolves and hyenas.
Chaparrals are located in the Mediterranean, as well as in California, Georgia, Mexico and the southern shores of Australia. These are zones of mild temperate climate, where precipitation falls from 500 to 700 millimeters throughout the year. Vegetation here includes shrubs and trees with evergreen hard leaves, such as wild pistachio, laurel, etc.
Ecological systems such as savannas are located in East and Central Africa, South America and Australia. A significant part of them is located in South India. These are zones of hot and dry climate, where precipitation falls from 250 to 750 mm throughout the year. The vegetation is mainly grassy, with only rare deciduous trees (palms, baobabs and acacias) found here and there. The fauna is represented by zebras and antelopes, rhinoceroses and giraffes, leopards and lions, vultures, etc. There are many blood-sucking insects in these parts, such as the tsetse fly.
Deserts are found in parts of Africa, northern Mexico, etc. The climate here is dry, with rainfall less than 250 mm per year. Days in deserts are hot and nights are cold. The vegetation is represented by cacti and sparse shrubs with extensive root systems. Among the representatives of the animal world, gophers and jerboas, antelopes and wolves are common. This is a fragile ecosystem, easily destroyed by water and wind erosion.
Semi-evergreen tropical deciduous forests are found in Central America and Asia. These areas experience alternating dry and wet seasons. The average annual precipitation is from 800 to 1300 mm. Tropical forests are inhabited by a rich fauna.
Tropical rain forests are found in many parts of our planet. They are found in Central America, northern South America, central and western equatorial Africa, coastal areas of northwestern Australia, as well as on the islands of the Pacific and Indian Oceans. Warm climatic conditions in these parts are not seasonal. Heavy rainfall exceeds the limit of 2500 mm throughout the year. This system is distinguished by a huge diversity of flora and fauna.
Existing natural complexes, as a rule, do not have any clear boundaries. Between them there is necessarily a transition zone. In it, not only does the interaction of populations of different types of ecosystems occur, but also special types of living organisms occur. Thus, the transition zone includes a greater diversity of fauna and flora than the surrounding areas.
Aquatic natural complexes
These biosphere units can exist in fresh water bodies and seas. The first of these include ecosystems such as:
Lentic are reservoirs, that is, standing water;
Lotic, represented by streams, rivers, springs;
Upwelling areas where productive fishing occurs;
Straits, bays, estuaries, which are estuaries;
Deep-water reef zones.
Example of a natural complex
Ecologists distinguish a wide variety of types of natural ecosystems. Nevertheless, the existence of each of them follows the same pattern. In order to most deeply understand the interaction of all living and non-living creatures in a unit of the biosphere, consider the species. All microorganisms and animals living here have a direct impact on the chemical composition of the air and soil.
A meadow is an equilibrium system that includes various elements. Some of them, macroproducers, which are herbaceous vegetation, create the organic products of this terrestrial community. Further, the life of the natural complex is carried out due to the biological food chain. Plant animals or primary consumers feed on meadow grasses and their parts. These are representatives of the fauna such as large herbivores and insects, rodents and many types of invertebrates (gopher and hare, partridge, etc.).
Primary consumers feed on secondary consumers, which include carnivorous birds and mammals (wolf, owl, hawk, fox, etc.). Next, reducers are involved in the work. Without them, a complete description of the ecosystem is impossible. Species of many fungi and bacteria are these elements in the natural complex. Decomposers decompose organic products to a mineral state. If temperature conditions are favorable, then plant debris and dead animals quickly disintegrate into simple compounds. Some of these components contain batteries that are leached and reused. The more stable part of organic residues (humus, cellulose, etc.) decomposes more slowly, feeding the plant world.
Anthropogenic ecosystems
The natural complexes discussed above are capable of existing without any human intervention. The situation is completely different in anthropogenic ecosystems. Their connections work only with the direct participation of a person. For example, an agroecosystem. The main condition for its existence is not only the use of solar energy, but also the receipt of “subsidies” in the form of a kind of fuel.
In part, this system is similar to natural. Similarities with the natural complex are observed during the growth and development of plants, which occurs due to the energy of the Sun. However, farming is impossible without soil preparation and harvesting. And these processes require energy subsidies from human society.
What type of ecosystem does the city belong to? This is an anthropogenic complex in which fuel energy is of great importance. Its consumption is two to three times higher than the flow of solar rays. The city can be compared to deep-sea or cave ecosystems. After all, the existence of precisely these biogeocenoses largely depends on the supply of substances and energy from the outside.
Urban ecosystems emerged through a historical process called urbanization. Under his influence, the population of countries left rural areas, creating large settlements. Gradually, cities increasingly strengthened their role in the development of society. At the same time, to improve life, man himself created a complex urban system. This led to a certain separation of cities from nature and disruption of existing natural complexes. The settlement system can be called urban. However, as industry developed, things changed somewhat. What type of ecosystem does the city on whose territory the plant or factory operates belong to? Rather, it can be called industrial-urban. This complex consists of residential areas and territories in which facilities producing a variety of products are located. The city ecosystem differs from the natural one in a more abundant and, in addition, toxic flow of various wastes.
In order to improve their living environment, people create so-called green belts around their settlements. They consist of grass lawns and shrubs, trees and ponds. These small-sized natural ecosystems create organic products that do not play a special role in urban life. To survive, people need food, fuel, water and electricity from outside.
The process of urbanization has significantly changed the life of our planet. The impact of the artificially created anthropogenic system has greatly changed nature over vast areas of the Earth. At the same time, the city influences not only those zones where the architectural and construction objects themselves are located. It affects vast areas and beyond. For example, with an increase in demand for wood products, people cut down forests.
During the functioning of a city, many different substances enter the atmosphere. They pollute the air and change climate conditions. Cities have higher cloud cover and less sunshine, more fog and drizzle, and are slightly warmer than nearby rural areas.
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.
The development of agriculture since ancient times 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 food.
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)
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Natural ecosystem (swamp, meadow, forest) |
Anthropogenic ecosystem (field, factory, house) |
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Receives, converts, accumulates solar energy |
Consumes energy from fossil and nuclear fuels |
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Produces oxygen and consumes carbon dioxide |
Consumes oxygen and produces carbon dioxide when fossils are burned |
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Forms fertile soil |
Depletes or poses a threat to fertile soils |
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Accumulates, purifies and gradually consumes water |
Consumes a lot of water and pollutes it |
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Creates habitats for a variety of wildlife species |
Destroys the habitats of many species of wildlife |
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Free filters and disinfects pollutants and waste |
Produces pollutants and waste that must be decontaminated at the expense of the public |
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Has the ability self-preservation and self-healing |
Requires high costs for constant maintenance and restoration |
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 regulation of pest numbers is, for the most part, a necessary condition for maintaining agroecosystems. Therefore, in agricultural practice, powerful means are used to suppress the number of undesirable species: pesticides, herbicides, etc. The environmental consequences of 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 could be the muscular strength of humans or animals, various types of fuel for operating agricultural machines, 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 participation, 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, 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
|
Natural ecosystems |
Agroecosystems |
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Primary natural elementary units of the biosphere, formed during evolution |
Secondary artificial elementary units of the biosphere transformed by humans |
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Complex systems with a significant number of animal and plant species in which populations of several species dominate. They are characterized by a stable dynamic balance achieved by self-regulation |
Simplified systems with dominant populations of one plant or animal species. They are stable and characterized by the variability of the structure of their biomass |
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Productivity is determined by the adaptive characteristics of organisms participating in the cycle of substances |
Productivity is determined by the level of economic activity and depends on economic and technical capabilities |
|
Primary products are used by animals and participate in the cycle of substances. “Consumption” occurs almost simultaneously with “production” |
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 that 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.
Industrial zones- these are areas where industrial facilities of various industries are concentrated (metallurgical, chemical, mechanical engineering, electronics, etc.). They are the main sources of environmental pollution.
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 all functional zones of the city 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- these are rocks, groundwater, which are affected 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.
Artificial ecosystems ( noobiogeocenoses or socioecosystems ) is a collection of organisms living in man-made conditions. In contrast, an ecosystem includes an additional peer community called noocenosis .
Noocenosis is part of an artificial ecosystem, including means of labor, society and products of labor.
Agrocenosis is a biocenosis artificially created by man for his own purposes with a certain level and nature of productivity.
Currently, about ten percent of the land is occupied by agrocenoses.
Despite the fact that in an agrocenosis, as in any natural ecosystem, there are obligatory trophic levels - producers, consumers, decomposers that form typical trophic networks, there are quite large differences between these two types of communities:
1) In agrocenoses the diversity of organisms is sharply reduced. Man maintains the monotony and species poverty of agrocenoses with a special complex system of agrotechnical measures. In the fields, one type of plant is usually cultivated, and therefore both the animal population and the composition of soil microorganisms are sharply depleted. However, even the most depleted agrocenoses include several dozen species of organisms belonging to different systematic and ecological groups. For example, in addition to wheat, the agrocenosis of a wheat field includes weeds, insects - wheat pests and predators, invertebrates - inhabitants of the soil and ground layer, pathogenic fungi, etc.
2) Species cultivated by humans are supported by artificial selection and cannot withstand the struggle for existence without human support.
3) Agroecosystems receive additional energy due to human activities, which provide additional conditions for the growth of cultivated plants.
4) Pure primary production of agrocenosis (plant biomass) is removed from the ecosystem in the form of crops and does not enter the food chain. Its partial consumption by pests is prevented in every possible way by human activity. As a result, the soil is depleted of minerals necessary for plant life. Therefore, human intervention in the form of fertilization is again necessary.
In agrocenoses, the effect of natural selection is weakened and mainly artificial selection operates, aimed at the maximum productivity of plants needed by humans, and not those that are better adapted to environmental conditions.
Thus, agrocenoses, unlike natural systems, are not self-regulating systems, but are regulated by humans. The goal of such regulation is to increase the productivity of the agrocenosis. To achieve this, dry lands are irrigated and waterlogged lands are drained; Weeds and crop-eating animals are destroyed, varieties of cultivated plants are changed and fertilizers are applied. All this creates benefits only for cultivated plants.
Unlike the natural ecosystem, the agrocenosis is unstable; it quickly collapses, because cultivated plants will not withstand competition with wild plants and will be crowded out by them.
Agrobiocenoses are also characterized by an edge effect in the distribution of insect pests. They concentrate mainly in the edge strip, and occupy the center of the field to a lesser extent. This phenomenon is due to the fact that in the transition zone competition between individual plant species sharply intensifies, and this, in turn, reduces the level of protective reactions in the latter against insects.
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*The term “ecosystem” is applicable to biocenoses and biotopes of various sizes, for example, the trunk of a dead tree, a forest or pond, or the ocean. These are all natural ecosystems. As an example of a natural, relatively simple ecosystem, consider the ecosystem of a small pond. The pond ecosystem can be thought of as two main components.
**Natural ecosystems are quite complex, and studying them using the traditional scientific method of “experience and control” is very difficult. Therefore, environmental scientists use laboratory artificial microecosystems that simulate processes occurring in natural conditions.
Aquarium as an artificial ecosystem
There is a misconception about "balance" in an aquarium. It is possible to achieve an approximate balance in the aquarium in terms of gas and food regimes only if there are few fish in it and there is a lot of water and plants. As early as 1857, J. Warrington established "that wonderful and delightful balance between the animal and vegetable kingdoms" in a 12-gallon (54.6 L) aquarium with several goldfish and snails. In addition, he planted a large number of perennial aquatic Vallisneria plants, which serve as food for fish. J. Warrington correctly assessed not only the interaction of fish and plants, but also the importance of detritivorous snails “for the decomposition of plant debris and mucus,” as a result of which “what could have acted as a poisonous principle was turned into a fertile medium for plant growth.” Most attempts by hobbyists to achieve balance in an aquarium end in failure due to the fact that too many fish are placed in the aquarium (an elementary case of overpopulation). Therefore, amateur aquarists have to periodically artificially maintain balance in the aquarium (additional nutrition, aeration, periodic cleaning of the aquarium).
***Perhaps the best way to imagine an artificial ecosystem is to think about space travel, since a person, leaving the biosphere, must take with him a clearly limited system that would provide all his vital needs using sunlight as energy coming from surrounding space environment.
Spaceship as an artificial ecosystem
There are open and closed types of spacecraft.
IN open system (without regeneration) the flow of substances and energy goes in one direction, and the life of the system will depend on the supply of water, food and oxygen. Used materials and waste are stored on the spacecraft until returned to earth or thrown into space (!).
IN closed In all parameters (except energy) the system undergoes a circulation of substances, which, just like the flow of energy, can be regulated using external mechanisms. Today, almost all spacecraft use an open-type system with varying degrees of regeneration.