largest ecosystem. Ecosystems, types of ecosystems. Diversity of natural components of the biosphere

Ecological complexes, their types and components are the main tool that makes it possible to study and understand the place of man on the planet, his influence on the biosphere, as well as improve methods of protecting the environment and maintain its stability and existence. All types of ecosystems are interconnected and cannot exist separately, so it is important not to disturb their interaction with each other.

Definition and concept of the concept

An ecological system is a set of living organisms, their natural habitats and communication systems, through which energy, substances and information are exchanged. The concept of "ecosystem" was proposed by the botanist A. Tensley in 1935, who devoted his whole life to studying the processes of botany.

The ecological system acts as a separate structural unit that combines biotic and abiotic factors. It is characterized by its line of self-development, a certain organization and the ability to provide vital materials. The concept of an ecosystem appeared only in the 20th century, but since then its scheme has become much more complicated and continues to change. It is influenced by natural causes and the intervention of progressive aspects.

The ecosystem is the most important part of the natural complex of the geographical and biological shell of our planet, which consists of the following components: soil, air, flora, fauna and water resources.

Natural communities do not have clear boundaries. They are separated by geographical barriers such as mountains, deserts, rivers, seas or oceans, so they usually merge into each other. The transition zones between them are called ecotones.

The ecosystem is often called biogeocenosis, but scientists believe that the second concept cannot be considered a complete synonym for this term. Biogeocenosis is an analogue of an ecological system at the initial level, associated with a specific area of the terrestrial or aquatic environment. The ecosystem considers abstract areas.

There are many different natural complexes in the world, but they are all united by the same principle: in any system there is a regional component called a biotope and characterized by the same landscape and climate, as well as a biocenosis represented by the inhabitants of the group permanently residing in the biotope. Together they form a biogeocenosis and cannot exist separately from each other.

Structure and main components

An ecosystem is made up of living organisms and their non-living environment. Between them there is an interaction that provides a stable and sustainable system. Examples of ecological communities are a meadow, desert, lake or pond.

Any ecosystem includes components:

Consumers are carnivorous, herbivorous and omnivorous animals, as well as insectivorous plants. To survive, they need organic substances produced by producers. Decomposers destroy dead organic compounds of consumers and producers from which they receive food. At the same time, in external environment pass simple components that are by-products of metabolism. They are reproduced as a result of the cyclic metabolism that takes place between the abiotic and biotic environments of an ecological system.

Soils include a large number of mineral and organic components. They also contain living organisms. The land is the main source of food and living environment for consumers. plays an important role in nutrient cycling top part soil with plants.

Oxygen and carbon dioxide released from the atmosphere are essential for photosynthesis. Between the surface of the planet and the atmosphere there is a water cycle. Due to solar radiation, the atmosphere heats up, as a result of which water evaporates. The process of photosynthesis also requires light energy, which affects the growth of plants and the metabolic processes occurring in them.

Most living tissues are characterized by a high percentage of water contained in them. Very few cells survive when this substance is reduced. Most of them die already at an indicator below 40%. Water is the medium through which mineral nutrients enter plants. It is an indispensable source of animal survival, which is formed from atmospheric precipitation.

Natural systems are characterized by long periods of existence. For this, all components must work correctly. In addition, processes of exchange and interaction with the environment are important for ecological communities. Although all systems are individual, they all have structure and components.

Ecological communities are characterized by great diversity. Systems are distinguished by such features as size, location, influence of external factors, origin, source of energy, ability to self-regulate and restore. Various processes take place in them and different components are involved, so scientists give several types of ecosystems with their characteristics.

Depending on the scale, the following communities are distinguished:

microecosystem - a small-scale system (ponds, puddles, stumps);
mesoecosystem - an ecosystem of medium size (forests, rivers, large lakes);
macroecosystem - the largest system that unites several ecosystems at once according to similar biotic and abiotic factors(tropical forest with all the animals living in it and growing trees, water bodies).

Ecosystems can be located on land or in water. Aquatic communities are oceanic, marine, river, lake. Biogeocenoses are also distinguished by the influence of factors such as temperature, precipitation and solar energy.

By origin, scientists distinguish ecosystems:

Natural. Such systems are of natural origin and exist with the participation of the environment. All components perform their functions independently. The largest natural ecosystem is the Earth.
Artificial. These complexes are created by man, so they are also called anthropogenic. People form them to get food for themselves, fresh air and other products necessary for life. Examples of artificial ecosystems are gardens, parks, fields, household plots.

Many ecological systems exist due to solar energy. Only some complexes of the biosphere use organic remains as the main or only source of energy. According to the ability to self-regulate and restore ecosystems are divided into independent and dependent.

There are other classifications of natural complexes. When dividing into groups, their biological composition, species diversity, and the dominance of certain consumers are taken into account.

Natural ecosystems are systems that depend on solar energy from outside, but there are also those that need an additional source of nutrition. The first group, which is completely dependent on the celestial body, is characterized by poor productivity in the processing of substances, but such ecological communities cannot be dispensed with. They form the climate and the state of the air layer around the Earth. Complexes of natural origin are located on the largest territories in terms of area. Natural ecosystems include terrestrial and aquatic.

Terrestrial ecological communities are divided into several groups:

Forest. They are distinguished by an abundance of vegetation and a large number of living organisms that exist in small areas. In these natural complexes, there are various species of fauna, the density of which is quite high. Even small changes in forest ecosystems greatly affect their overall balance. These include tropical, temperate, broad-leaved and taiga forests.
Desert. Occupy areas of deserts where there is little rainfall. Extremely heat air, poor access to water resources and intense sunlight negatively affect the species diversity of animals and plants in these areas.
Meadow ecosystem. Grasslands cover the temperate and tropical regions of the planet. Their territories are covered with herbaceous plants, shrubs and a few trees. The meadows are inhabited by predators and herbivores. Communities are divided into savannas, prairies and steppes.
Mountain. The mountainous areas are characterized by harsh climatic conditions in which only the alpine flora survives. Animals that live in the highlands have thick fur coats that protect them from the cold.

Water natural complexes are located in the aquatic environment with the corresponding fauna and flora. Since water can have different properties, the complexes are divided into rivers, seas, oceans and other bodies of water.

Experts distinguish the following aquatic ecosystems:

Marine. The largest system covering about 70% of the planet's surface. Sea water contains a huge amount of dissolved salts and minerals. Marine ecosystems are divided into the following zones: oceanic, profundal, benthal, tidal, estuaries.
Freshwater. Covers about 0.8% of the entire surface of the planet. Freshwater communities are divided into stagnant, flowing and wetland natural complexes.

Marine systems are rich in corals, brown algae, cephalopods, echinoderms, sharks and many other consumers and producers. The freshwater complexes are home to reptiles, amphibians and approximately 40% of the world's fish species. In fast-moving waters, dissolved oxygen is present at a high concentration, due to which a greater species diversity of living organisms is maintained than in lakes and other stagnant waters.

Man-made systems

Everything that belongs to the natural ecosystem is not always able to fully function independently. If even one key factor is lost, the entire community will fail and other links will be lost. In the worst case, the entire system dies. Maintain existence and normal functioning ecological complexes helps people.

Anthropogenic ecosystems practically do not differ from natural ones, only the main role in them is played by the influence of people. Such ecological communities exist everywhere: farming and Agriculture, engineering systems, cities, industrial centers. Recent examples have negatively affected the ecology of the Earth. Industry disrupts the flow of natural processes in nature, harms the regions closest to it and displaces the natural environment.

Unfavorable external factors lead to the transformation of the entire ecosystem: species diversity and their total mass increase, some plants and animals are replaced by other varieties, food chains become more complicated. These changes take place over a long period.

People consider nature an unimportant link, although without it they cannot exist. A person often takes from nature, and in return gives very little. It will be possible to save natural ecosystems only with a careful attitude towards them, solving problems modern society and conservation of natural resources.

Types of ecosystems.

Ecological system (ecosystem)- a spatially defined set of living organisms and their habitat, united by material-energy and informational interactions.

Distinguish between aquatic and terrestrial natural ecosystems.

Aquatic ecosystems- these are rivers, lakes, ponds, swamps - freshwater ecosystems, as well as seas and oceans - reservoirs with salt water.

Terrestrial ecosystems- these are tundra, taiga, forest, forest-steppe, steppe, semi-desert, desert, mountain ecosystems.

Each terrestrial ecosystem has an abiotic component - biotope, or ecotope - a site with the same landscape, climatic, soil conditions; and the biotic component - a community, or biocenosis - the totality of all living organisms inhabiting a given biotope. The biotope is a common habitat for all members of the community. Biocenoses consist of representatives of many species of plants, animals and microorganisms. Almost every species in the biocenosis is represented by many individuals of different sex and age. They form a population of a given species in an ecosystem. It is very difficult to consider a biocenosis separately from a biotope, therefore such a concept as a biogeocenosis (biotope + biocenosis) is introduced. Biogeocenosis is an elementary terrestrial ecosystem, the main form of existence of natural ecosystems.

Every ecosystem contains groups of organisms. different types, distinguished by the method of nutrition:

Autotrophs (“self-feeding”);

Heterotrophs (“feeding on others”);

Consumers - consumers organic matter living organisms;

Ditritophages, or saprophages, are organisms that feed on dead organic matter - the remains of plants and animals;

Decomposers - bacteria and lower fungi - complete the destructive work of consumers and saprophages, bringing the decomposition of organic matter to its complete mineralization and returning the last portions of carbon dioxide, water and mineral elements to the ecosystem environment.

All these groups of organisms in any ecosystem closely interact with each other, coordinating the flows of matter and energy.

Thus , a natural ecosystem is characterized by three features:

1) an ecosystem is necessarily a combination of living and non-living components.

2) within the ecosystem, a full cycle is carried out, starting with the creation of organic matter and ending with its decomposition into inorganic components.

3) the ecosystem remains stable for some time, which is provided by a certain structure of biotic and abiotic components.

Examples of natural ecosystems are: a fallen tree, an animal corpse, a small body of water, a lake, a forest, a desert, a tundra, a land, an ocean, a biosphere.

As can be seen from the examples, simpler ecosystems are included in more complex ones. At the same time, a hierarchy of system organization is implemented, in this case environmental. Therefore, ecosystems are divided according to the spatial scale into microecosystems, mesoecosystems and macroecosystems.

Thus, the structure of nature should be considered as a systemic whole, consisting of ecosystems nested one into another, the highest of which is a unique global ecosystem - the biosphere. Within its framework, there is an exchange of energy and matter between all living and non-living components on a planetary scale.

Anthropogenic impact on natural ecosystems.

Anthropogenic factors, i.e. the results of human activities that lead to a change in the environment can be considered at the level of the region, country or global level.

Anthropogenic pollution of the atmosphere leads to global change. Atmospheric pollution comes in the form of aerosols and gaseous substances. The greatest danger is represented by gaseous substances, which account for about 80% of all emissions. First of all, these are compounds of sulfur, carbon, nitrogen. Carbon dioxide itself is not poisonous, but its accumulation is associated with the danger of such a global process as " the greenhouse effect". We see the consequences of global warming.

With the release of sulfur and nitrogen compounds into the atmosphere, precipitation is associated acid rain. Sulfur dioxide and nitrogen oxides in the air combine with water vapor, then, together with rain, fall to the ground in the form of dilute sulfuric and nitric acids. Such precipitation sharply violates the acidity of the soil, contributes to the death of plants and the drying up of forests, especially coniferous ones. Once in rivers and lakes, they have a depressing effect on flora and fauna, often leading to the complete destruction of biological life - from fish to microorganisms. The distance between the place of formation of acid precipitation and the place of their fall can be thousands of kilometers.

These negative global impacts are exacerbated by processes desertification and deforestation. The main factor of desertification is human activity. Among the anthropogenic causes are overgrazing, deforestation, excessive and improper land exploitation. Scientists have calculated that the total area of man-made deserts exceeded the area of natural ones. That is why desertification is classified as a global process.

Now consider examples of anthropogenic impact at the level of our country. Russia occupies one of the first places in the world in terms of reserves fresh water. And considering that the total fresh water resources make up only 2% of the total volume of the Earth's hydrosphere, it becomes clear how rich we are. The main danger to these resources is the pollution of the hydrosphere. The main reserves of fresh water are concentrated in lakes, the area of which in our country is larger than the territory of Great Britain. Baikal alone contains approximately 20% of the world's fresh water reserves.

Scholars distinguish three types hydrosphere pollution: physical, chemical and biological.

Physical pollution refers primarily to thermal pollution resulting from the discharge of heated water used for cooling at thermal power plants and nuclear power plants. The discharge of such waters leads to a violation of the natural water regime. For example, rivers in places where such waters are discharged do not freeze. In closed reservoirs, this leads to a decrease in the oxygen content, which leads to the death of fish and the rapid development of unicellular algae (“blooming” of water). Physical contamination also includes radioactive contamination.

Chemical pollution of the hydrosphere occurs as a result of the ingress of various chemicals and compounds into it. An example is the discharge of heavy metals (lead, mercury), fertilizers (nitrates, phosphates) and hydrocarbons (oil, organic pollution). The main source is industry and transport.

Biological pollution is created by microorganisms, often pathogens. They enter the aquatic environment with chemical, pulp and paper, Food Industry and livestock complexes. Such effluents can be sources of various diseases.

A special issue in this topic is the pollution of the oceans. It happens in three ways.

The first of these is river runoff, with which millions of tons of various metals, phosphorus compounds, and organic pollution enter the ocean. At the same time, almost all suspended and most dissolved substances are deposited in the mouths of rivers and adjacent shelves.

The second way of pollution is associated with precipitation, with which most of the lead, half of the mercury and pesticides enter the World Ocean.

Finally, the third way is directly related to human economic activity in the waters of the World Ocean. The most common type of pollution is oil pollution during the transportation and extraction of oil.

Results of anthropogenic impact.

In our time, the consequences of anthropogenic impact on the geographic environment are diverse and not all of them are controlled by man, many of them appear later. Let's list the main ones.

Climate change (geophysics) of the Earth based on the enhancement of the greenhouse effect, emissions of methane and other gases, aerosols, radioactive gases, changes in ozone concentration.

The weakening of the ozone screen, the formation of a large "ozone hole" over Antarctica and "small holes" in other regions.

Pollution of the nearest outer space and its littering.

Pollution of the atmosphere with toxic and harmful substances, followed by acid rain and the destruction of the ozone layer, which involves freons, nitrogen oxides, water vapor and other gaseous impurities.

Pollution of the ocean, burial of toxic and radioactive substances in it, saturation of its waters with carbon dioxide from the atmosphere, pollution with oil products, heavy metals, complex organic compounds, disruption of the normal ecological connection between the ocean and land waters due to the construction of dams and other hydraulic structures.

Depletion and pollution surface water sushi and groundwater, imbalance between surface and ground waters.

Radioactive contamination of local areas and some regions due to Chernobyl accident, operation of nuclear devices and atomic testing.

The continuing accumulation on the land surface of toxic and radioactive substances, household waste and industrial waste(especially non-decomposing plastics), the occurrence of secondary chemical reactions with the formation of toxic substances.

Desertification of the planet, expansion of already existing deserts and deepening of the process of desertification itself.

Reduction of areas of tropical and northern forests, leading to a decrease in the amount of oxygen and the disappearance of animal and plant species.

The term "ecosystem" was first proposed in 1935 by the English ecologist A. Tensley. An ecosystem is the main structural unit of ecology, it is a single natural or natural-anthropogenic complex formed by living organisms and their habitat, in which living and inert ecological components are united by cause-and-effect relationships, metabolism and distribution of energy flow. Ecosystems are very diverse. There are several classifications of ecosystems.

By origin, the following types of ecosystems are distinguished.

1. Natural (natural) ecosystems are those ecosystems in which biological cycle proceeds without direct human intervention. On the basis of energy, they are divided into two types:

Ecosystems that depend entirely on direct solar radiation receive little energy and are therefore unproductive. However, they are extremely important, as they occupy huge areas where large volumes of air are cleaned, climatic conditions are formed, etc.

Ecosystems that receive energy from both the Sun and other natural sources. These ecosystems are much more productive than the first ones.

2. Anthropogenic (artificial) ecosystems - ecosystems created by man, which are able to exist only with the support of man. These ecosystems include:

Agroecosystems (Greek agros - field) - artificial ecosystems resulting from human agricultural activities;

Technoecosystems - artificial ecosystems resulting from human industrial activity;

Urbanecosystems (lat. urbanus - urban) - ecosystems resulting from the creation of human settlements. In industrial-urban ecosystems, fuel energy does not supplement, but replaces solar energy. The need for energy in densely populated cities is 2-3 orders of magnitude greater than the flow that supports life in natural ecosystems driven by the Sun. There are also transitional types of ecosystems between natural and anthropogenic, for example, ecosystems of natural pastures used by humans for grazing farm animals. All ecosystems are interconnected and interdependent. There is a classification of natural ecosystems depending on natural and climatic conditions, based on the predominant type of vegetation in large biome regions. Biome - a set of different groups of organisms and their habitat in a certain landscape-geographical zone. A biome is characterized by the main type of climate, vegetation, or landscape features. The main types of natural ecosystems and biomes (according to Yu. Odum, 1986) include the following terrestrial ecosystems:

Evergreen tropical rainforest;

Semi-evergreen tropical forest (pronounced wet and dry seasons);

Desert grassy shrub;

Chaparral - areas with rainy winters and dry summers;

Tropical grasslands (grassland) and savanna;

Steppe of the temperate zone;

Temperate deciduous forest;

boreal coniferous forests;

Tundra arctic and alpine.

In aquatic habitats, where vegetation is hardly noticeable, the hydrological and physical features of the environment, such as "stagnant water", "flowing water", are the basis for distinguishing ecosystems. Aquatic ecosystems are divided into freshwater and marine.

Freshwater ecosystems:

Tape (stagnant water) - lakes, ponds, etc.;

Lotic (flowing waters) - rivers, streams, etc.;

Wetlands are swamps and marshy forests.

Marine Ecosystems:

open ocean(pelagic ecosystem);

Continental shelf waters (coastal waters);

Upwelling areas (fertile areas with productive fisheries);

Estuaries (coastal bays, straits, river mouths, etc.);

Deep water rift zones.

(English) Russian the lake with the totality of organisms is defined as a "microcosm" ("The lake as a microcosm" - "The lake as a microcosme" (eng.), 1887). The modern term was first proposed by the English ecologist A. Tensley (English) Russian in 1935. V. V. Dokuchaev also developed the idea of biocenosis as an integral system. However, in Russian science, the concept of biogeocenosis introduced by V.N. Sukachev (1944) has become generally accepted. In related sciences, there are also various definitions that more or less coincide with the concept of "ecosystem", for example, "geosystem" in geoecology or introduced around the same period by other scientists "Holocene" (F. Clements, 1930) and "bio-inert body "(V. I. Vernadsky, 1944) .

The concept of an ecosystem

Definitions

Sometimes it is emphasized that an ecosystem is a historically established system (see Biocenosis).

Ecosystem concept

Eugene Odum (1913-2000). Father of Ecosystem Ecology

An ecosystem is a complex (as L. Bertalanffy defines complex systems) self-organizing, self-regulating and self-developing system. The main characteristic of an ecosystem is the presence of relatively closed, spatially and temporally stable flows of matter and energy between the biotic and abiotic parts of the ecosystem. It follows from this that not every biological system can be called an ecosystem, for example, an aquarium or a rotten stump are not. These biological systems (natural or artificial) are not sufficiently self-sufficient and self-regulating (aquarium), if you stop regulating the conditions and maintain the characteristics at the same level, it will collapse quickly enough. Such communities do not form independent closed cycles of matter and energy (stump), but are only part of a larger system. Such systems should be called communities of lower rank, or microcosms. Sometimes the concept of facies is used for them (for example, in geoecology), but it is not able to fully describe such systems, especially artificial origin. In general, in different sciences, the concept of "facies" corresponds to different definitions: from systems of the sub-ecosystem level (in botany, landscape science) to concepts that are not related to the ecosystem (in geology), or the concept that unites homogeneous ecosystems (Sochava V. B.), or almost identical (Berg L. S., Ramensky L. G.) to the definition of an ecosystem.

Biogeocenosis and ecosystem

In accordance with the definitions, there is no difference between the concepts of "ecosystem" and "biogeocenosis", biogeocenosis can be considered a complete synonym for the term ecosystem. However, there is a widespread opinion that biogeocenosis can serve as an analogue of an ecosystem at the very initial level, since the term "biogeocenosis" places more emphasis on the connection of a biocenosis with a specific piece of land or aquatic environment, while an ecosystem involves any abstract area. Therefore, biogeocenoses are usually considered a special case of an ecosystem. Different authors in the definition of the term biogeocenosis list specific biotic and abiotic components of biogeocenosis, while the definition of an ecosystem is more general.

Ecosystem structure

An ecosystem can be divided into two components - biotic and abiotic. Biotic is divided into autotrophic (organisms that receive primary energy for existence from photo- and chemosynthesis or producers) and heterotrophic (organisms that receive energy from the processes of oxidation of organic matter - consumers and decomposers) components that form the trophic structure of the ecosystem.

The only source of energy for the existence of an ecosystem and the maintenance of various processes in it are producers that absorb the energy of the sun, (heat, chemical bonds) with an efficiency of 0.1 - 1%, rarely 3 - 4.5% of the initial amount. Autotrophs represent the first trophic level of an ecosystem. Subsequent trophic levels of the ecosystem are formed at the expense of consumers (2nd, 3rd, 4th and subsequent levels) and are closed by decomposers, which convert inanimate organic matter into a mineral form (abiotic component), which can be assimilated by an autotrophic element.

Main components of the ecosystem

From the point of view of the structure in the ecosystem, there are:

climatic regime, which determines temperature, humidity, lighting mode, etc. physical characteristics environment;
inorganic substances included in the cycle;
organic compounds that link the biotic and abiotic parts in the cycle of matter and energy;
producers - organisms that create primary products;
macroconsumers, or phagotrophs, are heterotrophs that eat other organisms or large particles of organic matter;
microconsumers (saprotrophs) - heterotrophs, mainly fungi and bacteria, which destroy dead organic matter, mineralizing it, thereby returning it to the cycle.

The last three components form the biomass of the ecosystem.

From the point of view of the functioning of the ecosystem, the following functional blocks of organisms are distinguished (in addition to autotrophs):

biophages - organisms that eat other living organisms,
saprophages - organisms that eat dead organic matter.

This division shows the temporal-functional relationship in the ecosystem, focusing on the division in time of the formation of organic matter and its redistribution within the ecosystem (biophages) and processing by saprophages. Between the death of organic matter and the re-inclusion of its components in the cycle of matter in the ecosystem, a significant period of time can pass, for example, in the case of a pine log, 100 years or more.

All these components are interconnected in space and time and form a single structural and functional system.

Ecotop

Usually the concept ecotope was defined as a habitat of organisms, characterized by a certain combination of environmental conditions: soils, soils, microclimate, etc. However, in this case this notion is actually almost identical to the notion climatetop.

At the moment, an ecotope, in contrast to a biotope, is understood as a certain territory or water area with the entire set and characteristics of soils, soils, microclimate and other factors in a form unchanged by organisms. Alluvial soils, newly formed volcanic or coral islands, man-made quarries and other newly formed territories can serve as examples of an ecotope. In this case climatetop is part of the ecotope.

climatetop

Initially climatetop was defined by V.N. Sukachev (1964) as the air part of the biogeocenosis, which differs from the surrounding atmosphere in its gas composition, especially the concentration of carbon dioxide in the surface biohorizon, oxygen in the same place and in the biohorizons of photosynthesis, air mode, saturation with biolines, reduced and altered solar radiation and illumination, the presence of luminescence of plants and some animals, a special thermal regime and air humidity regime.

At the moment, this concept is interpreted a little more broadly: as a characteristic of biogeocenosis, a combination of physical and chemical characteristics of the air or water environment that are essential for the organisms inhabiting this environment. The climatotope sets on a long-term scale the main physical characteristics of the existence of animals and plants, determining the range of organisms that can exist in a given ecosystem.

edaphotop

Under edaphotop soil is usually understood as constituent element ecotope. However, this concept should be more precisely defined as part of the inert environment transformed by organisms, that is, not the entire soil, but only part of it. The soil (edaphotop) is the most important component of the ecosystem: the cycles of matter and energy are closed in it, the transfer from dead organic matter to mineral and their involvement in living biomass is carried out. The main energy carriers in the edaphotope are organic carbon compounds, their labile and stable forms, they determine soil fertility to the greatest extent.

Biocenosis, presented in a schematic form as a food web and its biotope

Biotope

Biocenosis

Sometimes a third aspect of sustainability is singled out - the stability of an ecosystem in relation to changes in the characteristics of the environment and changes in its internal characteristics. In the event that the ecosystem functions stably in a wide range of environmental parameters and/or the ecosystem contains big number interchangeable species (that is, when different species that are similar in ecological functions in an ecosystem can replace each other), such a community is called dynamically strong(sustainable). Otherwise, when an ecosystem can exist in a very limited set of environmental parameters, and/or most species are irreplaceable in their functions, such a community is called dynamically brittle(unstable). It should be noted that this characteristic, in the general case, does not depend on the number of species and the complexity of communities. A classic example is the Great Barrier Reef off the coast of Australia (northeast coast), which is one of the world's biodiversity hotspots - symbiotic coral algae, dinoflagellates, are quite sensitive to temperature. A deviation from the optimum by just a couple of degrees leads to the death of algae, and up to 50-60% (according to some sources, up to 90%) of the nutrients polyps receive from the photosynthesis of their mutualists.

Ecosystems have many states in which it is in dynamic equilibrium; in case of removal from it by external forces, the ecosystem will not necessarily return to its original state, often it will be attracted by the nearest equilibrium state (attractor), although it can be very close to the original one.

Biodiversity and sustainability in ecosystems

The Amazon rain forests, like the equatorial rainforests, are places of the greatest biodiversity.

Usually, sustainability has been and is associated with the biodiversity of species in an ecosystem (alpha diversity), that is, the higher the biodiversity, the more complex the organization of communities, the more complex the food webs, the higher the resilience of ecosystems. But already 40 or more years ago, there were different points of view on this issue, and at the moment the most common opinion is that both local and general ecosystem stability depend on a much larger set of factors than just community complexity and biodiversity. So, at the moment, an increase in complexity, the strength of connections between ecosystem components, and the stability of matter and energy flows between components are usually associated with an increase in biodiversity.

The equatorial rainforest can contain more than 5000 species of plants (for comparison, in the forests of the taiga zone - rarely more than 200 species)

The importance of biodiversity lies in the fact that it allows the formation of many communities that differ in structure, form, and functions, and provides a sustainable opportunity for their formation. The higher the biodiversity, the more communities can exist, the greater the number of various reactions (from the point of view of biogeochemistry) can be carried out, ensuring the existence of the biosphere as a whole.

Ecosystem complexity and resilience

At the moment, there is no satisfactory definition and model that describes the complexity of systems and ecosystems in particular. There are two widely accepted definitions of complexity: Kolmogorov complexity is too specialized to apply to ecosystems. And a more abstract, but also unsatisfactory definition of complexity given by I. Prigogine in Time, Chaos, Quantum: Complex systems - not capable of being roughly or operationally described in terms of deterministic causations. In his other works, I. Prigogine wrote that he was not ready to give a strict definition of complexity, since complex is something that cannot be correctly defined at the moment.

Complexity parameters and their impact on sustainability

Traditionally, ecosystem complexity parameters have been assumed to be total number species (alpha diversity), a large number of interactions between species, the strength of interactions between populations, and various combinations of these characteristics. With the further development of these ideas, the statement appeared that the more ways of transfer and transformation of energy in an ecosystem, the more stable it is under various types violations.

However, later it was shown that these representations cannot characterize the sustainability of ecosystems. There are many examples of both highly stable monocultural communities (bracken phytocenoses) and weakly stable communities with high biodiversity (coral reefs, tropical forests). In the 1970s and 1980s, interest in modeling the dependence of sustainability on the complexity of ecosystems increased. The models developed during this period showed that in a randomly generated network of interactions in the community, when meaningless circuits (of type A eats B, B eats C, C eats A and this type) local stability decreases with increasing complexity. If we continue to complicate the model and take into account that consumers are affected by food resources, and food resources do not depend on consumers, then we can conclude that sustainability does not depend on complexity, or also decreases with its increase. Of course, such results are valid mainly for detrital food chains, in which consumers do not affect the flow of food resources, although they can change the nutritional value of the latter.

When studying overall resistance in a model of 6 species (2 predator-consumers of the second order, 2 consumers of the first order and 2 species at the base of the food chain), the removal of one of the species was studied. Connectivity was taken as a stability parameter. A community was considered stable if other species remained locally stable. The results obtained were consistent with the generally accepted view that with an increase in complexity with the loss of higher order predators, the stability of the community decreases, but with the loss of bases of the food chain with increasing complexity, the stability increased.

In the case of elastic stability, when complexity is also understood as connectivity, with increasing complexity, elastic stability also increases. That is, a greater diversity of species and a greater strength of communication between them allows communities to quickly restore their structure and functions. This fact confirms the generally accepted views on the role of biodiversity as a kind of pool (fund) for restoring the full structure of both ecosystems and more highly organized structures of the biosphere, as well as the biosphere itself as a whole. At the moment, the generally accepted and virtually undeniable idea is that the biosphere has evolved towards increasing biodiversity (all three of its components), accelerating the circulation of matter between the components of the biosphere, and “accelerating” the life time of both species and ecosystems.

Fluxes of Matter and Energy in Ecosystems

At the moment, the scientific understanding of all processes within an ecosystem is far from perfect, and in most studies, either the entire ecosystem or some of its parts act as a "black box" . At the same time, like any relatively closed system, an ecosystem is characterized by an incoming and outgoing energy flow and the distribution of these flows between ecosystem components.

Ecosystem productivity

When analyzing the productivity and flows of matter and energy in ecosystems, the concepts biomass and harvest on the vine . Growing crop refers to the mass of bodies of all organisms per unit area of land or water, and biomass is the mass of the same organisms in terms of energy (for example, in joules) or in terms of dry organic matter (for example, in tons per hectare). Biomass includes the entire body of organisms, including vitalized dead parts, and not only in plants, for example, bark and xylem, but also nails and keratinized parts in animals. Biomass turns into necromass only when a part of the organism dies (is separated from it) or the whole organism. Substances often fixed in biomass are “dead capital”, this is especially pronounced in plants: xylem substances may not enter the cycle for hundreds of years, serving only as a support for the plant.

Under primary product of the community (or primary biological production) refers to the formation of biomass (more precisely, the synthesis of plastic substances) by producers, without exception, of the energy expended on respiration per unit time per unit area (for example, per day per hectare).

The primary production of the community is divided into gross primary production , that is, all the products of photosynthesis without the cost of respiration, and net primary production , which is the difference between gross primary production and respiration costs. Sometimes it is also called pure assimilation or observed photosynthesis ).

Community Net Productivity - the rate of accumulation of organic matter not consumed by heterotrophs (and then decomposers). Usually calculated for the growing season or for the year. Thus, it is part of the production that cannot be recycled by the ecosystem itself. In more mature ecosystems, the value of the net productivity of the community tends to zero (see the concept of climax communities).

Secondary Community Productivity - the rate of energy accumulation at the level of consumers. Secondary production is not divided into gross and net, since consumers only consume energy assimilated by producers, part of it is not assimilated, part goes to respiration, and the rest goes to biomass, therefore it is more correct to call it secondary assimilation.

The distribution of energy and matter in an ecosystem can be represented as a system of equations. If the production of producers is presented as P 1, then the production of consumers of the first order will look like this:

P 2 \u003d P 1 -R 2,

where R 2 - the cost of breathing, heat transfer and unassimilated energy. The following consumers (second order) will process the biomass of first order consumers in accordance with:

P 3 \u003d P 2 -R 3

and so on, up to consumers of the highest order and decomposers. Thus, the more consumers (consumers) in the ecosystem, the more fully the energy is processed, initially recorded by the producers in plastic substances. In climax communities, where the diversity for a given region is usually maximum, such an energy processing scheme allows communities to function stably for a long time.

Energy ratios in ecosystems (environmental efficiency)

Graph of changes in the P / B ratio in ecosystems (according to A. K. Brodsky, 2002)

Spatial boundaries of the ecosystem (chorological aspect)

In nature, as a rule, there are no clear boundaries between different ecosystems. It is always possible to point to one or another ecosystem, but it is not possible to single out discrete boundaries, if they are not represented by various landscape factors (cliffs, rivers, various hill slopes, rock outcrops, etc.), because most often there are smooth transitions from one ecosystem to another. This is due to a relatively smooth change in the gradient of environmental factors (humidity, temperature, humidity, etc.). Sometimes transitions from one ecosystem to another may actually be an independent ecosystem. Usually, communities that form at the junction of different ecosystems are called ecotones. The term "ecotone" was introduced by F. Clements in 1905.

Ecotones

Ecotones play a significant role in maintaining the biological diversity of ecosystems due to the so-called edge effect - a combination of a complex of environmental factors of various ecosystems, which causes a greater variety of environmental conditions, therefore, licenses and ecological niches. Thus, the existence of species both from one and another ecosystem, as well as species specific to the ecotone (for example, vegetation of coastal-aquatic habitats) is possible.

Some possible options for boundaries (ecotones) between ecosystems

In Russian literature, the edge effect is sometimes referred to as the edge effect.

Examples of ecotones are coastal areas of land and water bodies (for example, the littoral), edges, transitions from forest ecosystems to field ones, estuaries. However, the ecotone is not always a place of increased biodiversity of species. For example, the estuaries of rivers flowing into the seas and oceans, on the contrary, are characterized by a reduced biodiversity of species, since the average salinity of the deltas does not allow the existence of many freshwater and brackish (marine) species.

An alternative idea of continual transitions between ecosystems is the idea of ecoclines (ecological series). Ecoclean- gradual change of biotopes, genetically and phenotypically adapted to a particular habitat, with a spatial change in any environmental factor (usually climatic), and therefore constituting a continuous series of forms without noticeable breaks in gradualness. The ecocline cannot be divided into ecotypes. For example, the length of the ears of foxes and many others. etc., their characters change from north to south so gradually that it is very difficult to distinguish clear morphological groups that would naturally unite into subspecies.

Temporal boundaries of the ecosystem (chronological aspect)

Change of community in a pine forest after a ground fire (left) and two years after the fire (right)

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

Succession

Succession - this is a consistent, natural change of some communities by others in a certain area of \u200b\u200bthe territory, due to internal factors in the development of ecosystems. Each previous community determines the conditions for the existence of the next and its own disappearance. This is due to the fact that in ecosystems that are transitional in the succession series, there is an accumulation of matter and energy that they are no longer able to include in the cycle, transformation of the biotope, changes in the microclimate and other factors, and thus a material and energy base is created, as well as the environmental conditions necessary for the formation of subsequent communities. However, there is another model that explains the mechanism of succession as follows: the species of each previous community are replaced only by consistent competition, inhibiting and "resisting" the introduction of subsequent species. However, this theory considers only competitive relations between species, not describing the whole picture of the ecosystem as a whole. Of course, such processes are underway, but the competitive displacement of previous species is possible precisely because of the transformation of the biotope by them. Thus, both models describe different aspects of the process and are correct at the same time.

Succession is autotrophic (for example, succession after forest fire) and heterotrophic (for example, a drained swamp). In the early stages of an autotrophic successional sequence, the P/R ratio is much greater than one, since usually the primary communities are highly productive, but the ecosystem structure has not yet been fully formed, and there is no way to utilize this biomass. Consistently, with the complication of communities, with the complication of the structure of the ecosystem, the cost of respiration (R) grows, as more and more heterotrophs appear responsible for the redistribution of matter-energy flows, the P / R ratio tends to unity and, in fact, is the same for the terminal community (ecosystems ) . Heterotrophic succession has the opposite characteristics: in it, the P / R ratio in the early stages is much less than one(since there is a lot of organic matter and there is no need for its synthesis, it can be immediately used to build a community) and gradually increases as you move through the successional stages.

An example of a heterotrophic succession stage is a swampy meadow

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

As you move along the successional series, there is an increasing involvement of biogenic elements in the cycle in ecosystems, a relative closure within the ecosystem of the flows of such biogenic elements as nitrogen and calcium (one of the most mobile biogens) is possible. Therefore, in the terminal stage, when most of the biogens are involved in the cycle, ecosystems are more independent of the external supply of these elements.

To study the process of succession, various mathematical models are used, including those of a stochastic nature.

climax community

The concept of succession is closely related to the concept of a climax community. The climax community is formed as a result of a successive change of ecosystems and is the most balanced community that makes the most efficient use of material and energy flows, that is, it maintains the maximum possible biomass per unit of energy entering the ecosystem.

Theoretically, each successional series has a climax community (ecosystem), which is the terminal stage of development (or several, the so-called polyclimax concept). However, in reality, the succession series is not always closed by the climax, a subclimax community (or called F. Clements - plagiclimax) can be realized, which is a community that precedes the climax, sufficiently developed structurally and functionally. This situation may arise due to natural causes- environmental conditions or due to human activity (in this case it is called disclimax).

Ecosystem Ranks

The issue of ranking ecosystems is quite complicated. The allocation of minimal ecosystems (biogeocenoses) and ecosystems of the highest rank - the biosphere is beyond doubt. Intermediate allocations are quite complex, since the complexity of the chorological aspect does not always unambiguously allow one to determine the boundaries of ecosystems. In geoecology (and landscape science) there is the following ranking: facies - tract (ecosystem) - landscape - geographical area - geographical area - biome - biosphere. In ecology, there is a similar ranking, however, it is usually believed that it is correct to single out only one intermediate ecosystem - the biome.

Biomes

Biome - a large system-geographical (ecosystem) subdivision within the natural-climatic zone (Reimers N. F.). According to R. H. Whittaker - a group of ecosystems of a given continent that have a similar structure or physiognomy of vegetation and the general nature of environmental conditions. This definition is somewhat incorrect, since there is a connection to a specific continent, and some biomes are present on different continents, for example, the tundra biome or the steppe.

At the moment, the most generally accepted definition is: “Biome is a set of ecosystems with a similar type of vegetation located in the same natural and climatic zone” (T. A. Akimova, V. V. Khaskin).

What these definitions have in common is that, in any case, a biome is a set of ecosystems of one natural-climatic zone.

Allocate from 8 to 30 biomes. The geographical distribution of biomes is determined by:

The law of geographical zoning (formulated by V. V. Dokuchaev)

Terrestrial biomes classified by vegetation type
polar deserts Tundra Taiga broadleaf forests	Steppes subtropical rainforests mediterranean biomes monsoon forests	Arid deserts xerophytic shrubs Southern steppes Semiarid deserts	Savannah Savannas with woody vegetation (forest-steppe) subtropical forest Tropical rain forest	Alpine tundra mountain forests

Biosphere

Term biosphere was introduced by Jean-Baptiste Lamarck in early XIX century, and in geology it was proposed by the Austrian geologist Eduard Suess in 1875. However, the creation of a holistic doctrine of the biosphere belongs to the Russian scientist Vladimir Ivanovich Vernadsky.

The biosphere is an ecosystem of a higher order that unites all other ecosystems and ensures the existence of life on Earth. The composition of the biosphere includes the following "spheres":

The biosphere is also not a closed system, it is actually completely provided with the energy of the Sun, a small part is the heat of the Earth itself. Every year, the Earth receives about 1.3 * 10 24 calories from the Sun. 40% of this energy is radiated back into space, about 15% goes to heat the atmosphere, soil and water, the rest of the energy is visible light, which is the source of photosynthesis.

V. I. Vernadsky for the first time clearly formulated the understanding that all life on the planet is inextricably linked with the biosphere and owes its existence to it:

artificial ecosystems

artificial ecosystems - these are ecosystems created by man, for example, agrocenoses, natural economic systems or Biosphere 2.

Artificial ecosystems have the same set of components as natural ones: producers, consumers and decomposers, but there are significant differences in the redistribution of matter and energy flows. In particular, human-created ecosystems differ from natural ones in the following ways:

Without the maintenance of energy flows by a person in artificial systems at one speed or another, natural processes are restored and the natural structure of the components of the ecosystem and the material-energy flows between them is formed.

Concepts similar to the concept of an ecosystem in related sciences

In ecogeology, landscape science and geoecology

In these sciences, there are concepts similar to the concept of an ecosystem. The difference lies in the fact that in these sciences there is a shift in the aspect of considering the structure and functions of ecosystems.

In general, in geographical sciences, it is customary to consider a natural territorial complex as an equivalent of an ecosystem.

Notes

Forbes, S.A. The lake as a microcosm // Bull. sci. Assoc. - Peoria, Illinois, 1887. - P. 77–87. Reprinted in Illinois Nat. Hist. Survey Bulletin 15(9):537-550.
Y. Odum. Fundamentals of ecology. - M .: Mir, 1975. - 741 p.
. Dictionaries at the Academy. archived
Y. Odum. Ecology. - M .: Mir, 1986.
Section "Ecosystems". The ECOLOGY site. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Biogeocenosis Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Nikolaykin, N. I., Nikolaykina, N. E., Melekhova, O. P. Ecology. - 5th. - M.: Bustard, 2006. - 640 p.
Brodsky A.K. A short course in general ecology, textbook for universities. - St. Petersburg: "Dean", 2000. - 224 p.
N. V. Koronovsky, Hydrothermal Formations in the Oceans . Soros Educational Journal, - No. 10, 1999, - pp. 55-62. Retrieved 14 August 2010.
D. V. Grichuk. Therodynamic Models of Submarine Hydrothermal Systems. - M .: Scientific world, 2000. - ISBN UDC 550.40
V. F. Levchenko. Chapter 3 // Evolution of the Biosphere before and after the appearance of man. - St. Petersburg: Nauka, 2004. - 166 p. - ISBN 5-02-026214-5
Rautian A.S. Paleontology as a source of information about the patterns and factors of evolution // Modern paleontology. - M ., 1988. - T. 2. - S. 76-118.
Rautian A. S., Zherikhin V. V. Phylocenogenesis Models and Lessons environmental crises geological past // Journal. total biology. - 1997. - V. 58 No. 4. - S. 20-47.
Ostroumov S. A. New variants of definitions of concepts and terms "ecosystem" and "biogeocenosis" // DAN. - 2002. - T. 383 No. 4. - S. 571-573.
M. Bigon, J. Harper, C. Townsend. Ecology. Individuals, populations and communities. - M .: Mir, 1989.
Ecotop Archived from the original on August 22, 2011. Retrieved August 14, 2010.
T. A. Rabotnov"On Biogeocenoses". // Bulletin of MOIP, Department of Biology, - vol. 81, - issue. 2. – 1976. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
climatotope. Bykov B. A."Ecological Dictionary" - Alma-Ata: "Science", 1983 - p.216. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Basic terms of ecology. Burenina E.M., Burenin E.P. Electronic textbook on ecology. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
climatotope. Dictionary of natural sciences (Yandex dictionaries). Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Archived from the original on August 22, 2011. Retrieved August 14, 2010.
. Ecological Dictionary (Dictionaries at Academician). Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Biocenosis. Great Soviet Encyclopedia. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Zoocenosis. Great Soviet Encyclopedia. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Ecosystem homeostasis. Scientific Information Portal VINITI. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Hutchinson S., Hawkins L. E. Oceans. Encyclopedic guide. - M .: Makhaon, 2007. - 304 p. - ISBN 5-18-001089-6
A. Gilyarov."Coral bleaching due to loss of rapport". Elements big science. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
A. D. Armand, Experiment "Gaia", the problem of the living earth. The Russian Academy of Sciences. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
A. V. Galanin. Lectures on ecology. . Website of the Botanical Garden of the Far Eastern Branch of the Russian Academy of Sciences. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Prigogine I., Stengers I. Time, chaos, quantum. - Moscow, 1994. - S. 81. - 263 p.
Nicolis G., Prigogine I. Knowledge of the complex. - M.: Mir, 1990. - p. 352. Page 47
MacArthur R.H. Fluctuations of animal populations and a measure of community stability // Ecology, 36, 1955, - pp. 533-536
May R.M. Will a large complex system be stable? // Nature (London), 1972, 238, - pp. 413-414
May R.M Models for single populations. // Theoretical Ecology: Principles and Applications, 2nd edn., R.M. May ed. - pp. 5-29, - Blackwell Scientific Publications, Oxford 1981
May R.M Models for two interacting populations. // Theoretical Ecology: Principles and Applications, 2nd edn., R.M. May ed. - pp.78-104, - Blackwell Scientific Publications, Oxford 1981
May R.M Patterns in multi-species communities. // Theoretical Ecology: Principles and Applications, 2nd edn., R.M. May ed., - Blackwell Scientific Publications, Oxford 1981
DeAngelis D.L. Stability and connectivity in food web models // Ecology 56, 1975, - pp. 238-243
Pimm S.L. The structure of food webs // Theoretical Population Biology, 16, 1979, - pp. 144-158
Pimm S.L. Complexity and stability: another look at MacArthu's original hypothesis // Oikos, 33, 1979, - pp. 351-357
V. F. Levchenko, Ya. I. Starobogatov Physico-ecological approach to the evolution of the biosphere. // "Evolutionary biology: history and theory". St. Petersburg, 1999, - p. 37-46. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Levchenko V.F. The evolution of the biosphere before and after the appearance of man. . St. Petersburg, Institute of Evolutionary Physiology and Biochemistry Russian Academy Sciences, - Publishing house "NAUKA", 2004. Archived from the original on August 22, 2011. Retrieved on August 14, 2010.
primary production. Scientific and information portal VINITI. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
primary productivity. Glossary.ru. Retrieved 14 August 2010.
Mavrischev V.V. Continuum, ecotones, edge effect // Fundamentals of Ecology: textbook. - 3rd ed. correct and additional - Minsk: graduate School, 2007. - 447 p. - ISBN 978-985-06-1413-1
Ecoton. . Dictionary of natural sciences (Yandex dictionaries). Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Ecotone and the concept of the edge (boundary) effect. Bioecology website. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Curvy effect. Ecological encyclopedic dictionary. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Estuary. . Glossary of terms physical geography Institute of Geography RAS. Archived from the original on August 22, 2011. Retrieved August 14, 2010.
Succession. Great Soviet Encyclopedia. Archived from the original on August 22, 2011. Retrieved August 14, 2010.

There are various ecosystems on our planet. Types of ecosystems are classified in a certain way. However, it is impossible to link together the diversity of these units of the biosphere. That is why there are several classifications of ecological systems. For example, they distinguish them by origin. This is:

Natural (natural) ecosystems. These include those complexes in which the circulation of substances is carried out without any human intervention.

Artificial (anthropogenic) ecosystems. They are created by man and can only exist with his direct support.