The biological cycle of substances is. Biological and geological cycles

The cycle of substances in the biosphere is a cyclical, repeatedly repeating process of joint, interconnected transformation and movement of substances. The presence of the cycle of substances is a necessary condition existence of the biosphere. After being used by some organisms, substances must be converted into a form accessible to other organisms. Such a transition of substances from one link to another requires energy expenditure, and therefore is possible only with the participation of solar energy. With the use of solar energy, two interconnected cycles of substances occur on the planet: large - geological and small - biological (biotic).

Geological cycle of substances- the process of migration of substances, carried out under the influence of abiotic factors: weathering, erosion, water movement, etc. Living organisms do not take part in it.

With the emergence of living matter on the planet, biological (biotic) cycle. All living organisms take part in it, absorbing some substances from the environment and releasing others. For example, in the process of life, plants consume carbon dioxide, water, and minerals from the environment and release oxygen. Animals use oxygen released by plants for respiration. They eat plants and, as a result of digestion, assimilate organic substances formed during photosynthesis. They release carbon dioxide and undigested food debris. After plants and animals die, they form a mass of dead organic matter (detritus). Detritus is available for decomposition (mineralization) by microscopic fungi and bacteria. As a result of their vital activity, additional amounts of carbon dioxide enter the biosphere. And organic substances are converted into their original inorganic components- biogens. The resulting mineral compounds, entering water bodies and soil, again become available to plants for fixation through photosynthesis. This process is repeated endlessly and is closed in nature (circulation). For example, all atmospheric oxygen passes along this path in about 2 thousand years, and carbon dioxide takes about 300 years to do this.

The energy contained in organic matter ah, it decreases as it moves through food chains. Most of it is dissipated in the environment in the form of heat or spent on maintaining the vital processes of organisms. For example, on the respiration of animals and plants, the transport of substances in plants, as well as on the processes of biosynthesis of living organisms. In addition, the biogens formed as a result of the activity of decomposers do not contain energy available to organisms. IN in this case we can only talk about the flow of energy in the biosphere, but not about the cycle. Therefore, the condition for the sustainable existence of the biosphere is the constant circulation of substances and energy flow in biogeocenoses.

Geological and biological cycles together form the general biogeochemical cycle of substances, which is based on the cycles of nitrogen, water, carbon and oxygen.

Nitrogen cycle

Nitrogen is one of the most common elements in the biosphere. The bulk of biosphere nitrogen is found in the atmosphere in gaseous form. As you know from a chemistry course, the chemical bonds between atoms in molecular nitrogen (N 2) are very strong. Therefore, most living organisms are not able to use it directly. Hence, an important stage in the nitrogen cycle is its fixation and conversion into a form accessible to organisms. There are three pathways for nitrogen fixation.

Atmospheric fixation. Under the influence of atmospheric electrical discharges(lightning) nitrogen can react with oxygen to form nitrogen oxide (NO) and dioxide (NO 2). Nitric oxide (NO) is very quickly oxidized by oxygen and converted into nitrogen dioxide. Nitrogen dioxide dissolves in water vapor and enters the soil in the form of nitrous (HNO 2) and nitric (HNO 3) acids with precipitation. In the soil, as a result of the dissociation of these acids, nitrite (NO 2 –) and nitrate ions (NO 3 –) are formed. Nitrite and nitrate ions can already be absorbed by plants and be included in the biological cycle. Atmospheric nitrogen fixation accounts for about 10 million tons of nitrogen per year, which is about 3% of annual nitrogen fixation in the biosphere.

Biological fixation. It is carried out by nitrogen-fixing bacteria, which convert nitrogen into forms accessible to plants. Thanks to microorganisms, about half of all nitrogen is bound. The best known bacteria are those that fix nitrogen in the nodules of legumes. They supply nitrogen to plants in the form of ammonia (NH 3). Ammonia is highly soluble in water to form ammonium ion (NH 4 +), which is absorbed by plants. Therefore, legumes are the best predecessors cultivated plants in crop rotation. After the death of animals and plants and the decomposition of their remains, the soil is enriched with organic and mineral nitrogen compounds. Next, putrefactive (ammonifying) bacteria break down nitrogen-containing substances (proteins, urea, nucleic acids) of plants and animals into ammonia. This process is called ammonification. Most of the ammonia is subsequently oxidized by nitrifying bacteria to nitrites and nitrates, which are again used by plants. Nitrogen is returned to the atmosphere through denitrification, which is carried out by a group of denitrifying bacteria. As a result, nitrogen compounds are reduced to molecular nitrogen. Part of the nitrogen in nitrate and ammonium forms enters the surface with surface runoff. aquatic ecosystems. Here nitrogen is absorbed by aquatic organisms or enters bottom organic sediments.

Industrial fixation. A large amount of nitrogen is fixed annually industrially during the production of mineral nitrogen fertilizers. Nitrogen from such fertilizers is absorbed by plants in ammonium and nitrate forms. The volume of nitrogen fertilizers produced in Belarus is currently about 900 thousand tons per year. The largest producer is OJSC GrodnoAzot. This enterprise produces urea, ammonium nitrate, ammonium sulfate and other nitrogen fertilizers.

Approximately 1/10 of artificially applied nitrogen is used by plants. The rest goes into aquatic ecosystems with surface runoff and groundwater. This leads to the accumulation of large amounts of nitrogen compounds in the water, available for absorption by phytoplankton. As a result, rapid proliferation of algae (eutrophication) and, as a result, death in aquatic ecosystems is possible.

Water cycle

Water is the main component of the biosphere. It is a medium for the dissolution of almost all elements during the cycle. Most of the biosphere water is represented by liquid water and water from eternal ice (more than 99% of all water reserves in the biosphere). A small part of the water is in gaseous state is atmospheric water vapor. The biosphere water cycle is based on the fact that its evaporation from the Earth’s surface is compensated by precipitation. When water reaches the land surface in the form of precipitation, it contributes to the destruction of rocks. This makes the minerals that make them available to living organisms. It is the evaporation of water from the surface of the planet that determines its geological cycle. It consumes about half of the incident solar energy. Evaporation of water from the surface of seas and oceans occurs at a faster rate than its return with precipitation. This difference is compensated by surface and deep runoff due to the fact that precipitation prevails over evaporation on the continents.

The increase in the intensity of water evaporation on land is largely due to the vital activity of plants. Plants extract water from the soil and actively transpire it into the atmosphere. Some of the water in plant cells is broken down during photosynthesis. In this case, hydrogen is fixed in the form organic compounds, and oxygen is released into the atmosphere.

Animals use water to maintain osmotic and salt balance in the body and release it into the external environment along with metabolic products.

Carbon cycle

Carbon as a chemical element is present in the atmosphere as carbon dioxide. This determines the mandatory participation of living organisms in the cycle of this element on planet Earth. The main route by which carbon is taken from inorganic compounds passes into the composition of organic substances, where it is an obligatory chemical element - this is the process of photosynthesis. Some carbon is released into the atmosphere as carbon dioxide during the respiration of living organisms and during the decomposition of dead organic matter by bacteria. The carbon absorbed by plants is consumed by animals. In addition, coral polyps and mollusks use carbon compounds to build skeletal structures and shells. After they die and settle, limestone deposits form at the bottom. Thus, carbon can be excluded from the cycle. The removal of carbon from the cycle for a long time is achieved through the formation of minerals: coal, oil, peat.

Throughout the existence of our planet, the carbon removed from the cycle was compensated for by carbon dioxide entering the atmosphere during volcanic eruptions and other natural processes. Currently, a significant amount of carbon has been added to the natural processes of carbon replenishment in the atmosphere. anthropogenic impact. For example, when burning hydrocarbon fuels. This disrupts the carbon cycle on Earth, which has been regulated for centuries.

An increase in carbon dioxide concentration over a century of just 0.01% led to a noticeable manifestation greenhouse effect. The average annual temperature on the planet increased by 0.5 °C, and the level of the World Ocean rose by almost 15 cm. According to scientists, if the average annual temperature increases by another 3-4 °C, the eternal ice will begin to melt. At the same time, the level of the World Ocean will rise by 50-60 cm, which will lead to the flooding of a significant part of the land. This is considered global environmental disaster, because about 40% of the Earth’s population lives in these territories.

Oxygen cycle

Oxygen plays an exclusive role in the functioning of the biosphere important role in metabolic processes and respiration of living organisms. The decrease in the amount of oxygen in the atmosphere as a result of the processes of respiration, fuel combustion and decay is compensated by the oxygen released by plants during photosynthesis.

Oxygen was formed in the Earth's primary atmosphere as it cooled. Due to its high reactivity, it passed from a gaseous state into the composition of various inorganic compounds (carbonates, sulfates, iron oxides, etc.). Today's oxygen-containing atmosphere of the planet was formed exclusively due to photosynthesis carried out by living organisms. The oxygen content in the atmosphere has been rising to current levels for a long time. Maintaining its quantity at a constant level is currently possible only thanks to photosynthetic organisms.

Unfortunately, in last decades Human activities leading to deforestation and soil erosion reduce the intensity of photosynthesis. And this, in turn, disrupts the natural course of the oxygen cycle over large areas of the Earth.

Not most atmospheric oxygen is involved in the processes of formation and destruction of the ozone screen when exposed to ultraviolet radiation Sun.

The basis of the biogenic cycle of substances is solar energy. The main condition for the sustainable existence of the biosphere is the constant circulation of substances and energy flow in biogeocenoses. Living organisms play a major role in the nitrogen, carbon and oxygen cycles. The basis of the global water cycle in the biosphere is provided by physical processes.

Topic 3.4. BIOLOGICAL CYCLE OF ELEMENTS

3.4.1. General concept of the biological cycle of substances

Since the beginning of studying the interaction of living organisms with environment it became clear that the processes of biogenic mass transfer have cyclical nature(see Fig. 2.3.2).

Mass transfer cycles of varying length in space and unequal duration in time form dynamic system biosphere. V.I. Vernadsky believed that the history of the majority chemical elements, forming more than 99% of the mass of the biosphere, can only be understood taking into account circular migrations (cycles). At the same time, he emphasized that “these cycles are reversible only in the main part of the atoms, while some elements inevitably and constantly leave the cycle. This output is natural, i.e. the circular process is not completely reversible.” Incomplete reversibility and imbalance of migration cycles allow certain concentrations of the migrating element, to which organisms can adapt, but at the same time, ensure the removal of excess amounts of the element from a given cycle.

That is, the integrity of the biosphere as a system is due to the continuous exchange of matter between its components, in which processes associated with the synthesis and decomposition of organic matter play a key role. They are realized both in the course of metabolism between living organisms and the environment, and in the processes of mineralization of organic matter after the death of the organism as a whole or the death of its individual organs. In addition, processes of exchange of matter between various components, which are non-biogenic in nature, also contribute to the cycle of matter in the biosphere. geographic envelope.

3.4.2. Elements of biogeochemical cycle of substances.
Parameters of the biological cycle of elements on land and in the ocean

Biological cycle of substances represents a set of admission processes chemical organisms into living organisms, biochemical synthesis of new complex compounds and the return of elements to the soil, atmosphere and hydrosphere (Fig.)

Abiogenic and biological cycles are closely intertwined, forming a planetary geochemical cycle and a system of local cycles of matter. Thus, over billions of years biological history Our planet has developed a great biogeochemical cycle and differentiation of chemical elements in nature, which is the basis for the normal functioning of the biosphere. That is, in the conditions of a developed biosphere, the cycle of substances is directed by the combined action of biological, geological and geochemical factors. The relationship between them may be different, but the action must be joint! It is in this sense that the terms biogeochemical circulation of substances and biogeochemical cycles are used.

The biological cycle is not a fully compensated closed cycle.

The biological, biochemical and geochemical significance of the processes carried out in the biological cycle of substances was first shown by V.V. Dokuchaev. It was further revealed in the works of V.I. Vernadsky, B.B. Polynova, D.N. Pryanishnikova, V.N. Sukacheva, L.E. Rodina, N.I. Bazilevich, V.A. Kovda and other researchers.

Before we begin to study the natural biological cycles of chemical elements, it is necessary to become familiar with the most commonly used terms.

Biomass - the mass of living matter accumulated to at this moment time.

Phytomass (or plant biomass0 - the mass of living and dead organisms of plant communities that have retained their anatomical structure at a given moment in any specific area or on the planet as a whole.

Structure of phytomass - the ratio of underground and aboveground parts of plants, as well as annual and perennial, photosynthetic and non-photosynthetic parts of plants.

Rags – dead parts of plants that have retained a mechanical connection with the plant.

Decay - the amount of organic matter of plants that have died in above-ground and underground parts per unit area per unit of time.

Litter – a mass of perennial deposits of plant residues of varying degrees of mineralization.

Gain – the mass of an organism or community of organisms accumulated per unit area per unit of time.

True Gain – the ratio of the amount of growth to the amount of litter per unit time per unit area.

Primary production – the mass of living matter created by autotrophs (green plants) per unit area per unit time.

Secondary products – the mass of organic matter created by heterotrophs per unit area per unit time.

It is also necessary to distinguish between the capacity and speed of the biological cycle.

Capacity of the biological cycle – the number of chemical elements contained in the mass of a mature biocenosis (phytocenosis).

Intensity of biological cycle – the amount of chemical elements contained in the growth of biomass per unit area per unit time.

Biological turnover rate - the period of time during which an element travels from its absorption by living matter to its release from living matter.

Field. Rodina and N.I. Bazilevich (1965), the full cycle of the biological cycle of elements on land consists of the following components:

1. Absorption of carbon by plants from the atmosphere, and nitrogen, ash elements and water from the soil, their fixation in the bodies of plant organisms, entry into the soil with dead plants or their parts, decomposition of litter and release of the elements contained in them.
2. Eating parts of plants by animals that feed on them, converting them in the bodies of animals into new organic compounds and fixing some of them in animal organisms, their subsequent entry into the soil with the excrement of animals or with their corpses, decomposition of both and the release of the elements contained in them.
3. Gas exchange between plants and the atmosphere (including soil air).
4. Lifetime secretions of certain elements by above-ground plant organs and their root systems directly into the soil.

The structure of the biosphere itself general view represents two largest natural complexes of the first rank - continental and oceanic. IN modern era The land as a whole is an eluvial system, the ocean an accumulative system. The history of the "geochemical relationship" between the ocean and land is reflected in the chemical composition of soils and ocean waters. The elements that are the basis of life - Si, Al, Fe, Mn, C, P, N, Ca, K - accumulate in the soil, and H, O, Na, Cl, S, Mg - form the chemical basis of the ocean.

Plants, animals and soil cover of the world's land form a complex system. By binding and redistributing solar energy, atmospheric carbon, moisture, oxygen, hydrogen, nitrogen, phosphorus, sulfur, calcium and other biophilic elements, this system constantly forms new biomass and generates free oxygen.

There is a second system in the ocean ( aquatic plants and animals), performing on the planet the same functions of binding solar energy, carbon, nitrogen, phosphorus and other biophiles through the formation of phytobiomass and the release of oxygen into the atmosphere.

You already know that there are three forms of accumulation and redistribution of cosmic energy (primarily the energy of the Sun) in the biosphere.

The essence of the first of them is this. That living organisms, and through food chains and associated animals and bacteria, build their tissues using many chemical elements and their compounds. Among the most important of them are macroelements - H, O, N, P, S, Ca, K, Mg, Si, Al, Mn, as well as microelements I, Co, Cu, Zn, Mo, etc. In this case, selective selection of light isotopes occurs carbon, hydrogen, oxygen, nitrogen and sulfur from heavier ones.

Throughout their entire life and even after death, living organisms of land, water and air are in a state of continuous exchange with the environment. In this case, the total mass and volume of the products of intravital metabolism of organisms and the environment (metabolites) are several times higher than the biomass of living matter.

The elements of the biogeochemical cycle are the following components:

1. Continuous or regularly repeating processes of energy influx, formation and synthesis of new compounds.
2. Constant or periodic processes of transfer or redistribution of energy and processes of removal and directional movement of synthesized compounds under the influence of physical, chemical and biological agents.
3. Directed rhythmic processes of sequential transformation: decomposition, destruction of previously synthesized compounds under the influence of biogenic and abiogenic environmental influences.
4. Continuous or periodic formation of the simplest mineral or organomineral components in a gaseous, liquid or solid state, which play the role of initial components for new, regular cycles of substances.

Biological are caused by the vital activity of organisms (nutrition, food connections, reproduction, growth, movement of metabolic products, death, decomposition, mineralization)

Mandatory parameters taken into account during the study biogeochemical cycles are the following main indicators:

1. Total biomass and its actual growth (phyto-, zoo-, microbial mass separately).
2. Organic litter (quantity, composition)
3. Soil organic matter (humus, undecomposed organic matter).
4. Elementary material composition of soils, waters, air, sediments, individual fractions of biomass.
5. Ground and underground reserves biogenic energy.
6. Lifetime metabolites
7. Number of species of living organisms, their numbers, composition
8. Life expectancy of organisms of each species, life dynamics of populations of living organisms and soils.
9. Ecological and meteorological environment: background and assessment of human intervention.
10. Characteristics of various landscapes and their elements.
11. The amount of pollutants, their chemical, physical, biological properties.

The individual significance of a particular chemical element is assessed by the coefficient of biological absorption, which is determined by the ratio of the content of the element in plant ash (by weight) to the content of the same element in the soil (or in the earth’s crust).

In 1966 V.A. Kovda proposed using the ratio of the recorded phytobiomass to the annual photosynthetic increase in phytomass to characterize the average duration of the overall carbon cycle. This coefficient characterizes the average duration of the overall cycle of synthesis-mineralization of biomass in a given area (or on land in general). Calculations have shown that the share of land in general this cycle fits into the period from 300-400 to 1000 years. Accordingly, with this average goes at speed release of mineral compounds bound in biomass, formation and mineralization of humus in the soil.

For a general assessment of the biogeochemical significance of the mineral components of living matter in the biosphere, V.A. Kovda proposed to compare the reserve of mineral substances of biomass, as well as the amount of mineral substances annually involved in circulation with growth and litter, with the annual chemical runoff of rivers. It turned out that these values ​​are comparable. This means that most of the substances dissolved in river waters passed through the biological cycle of the plant-soil system, before it joined the geochemical migration with water in the direction of the ocean or inland depressions.

It turned out that the biogeochemical cycle indices vary greatly in different climatic conditions, under the cover of various plant communities, with different conditions natural drainage, so N.I. Bazilevich and L.E. Rodin proposed to calculate an additional coefficient characterizing the intensity of litter decomposition and the duration of litter preservation under the conditions of a given biogeocenosis, equal to ratio mass of litter to the mass of annual litter. According to these researchers, the phytomass decomposition indices are greatest in the tundra and swamps of the north, and the lowest (about 1) in the steppes and semi-deserts.

B.B. Polynov proposed calculating the water migration index equal to the ratio of the amount of an element in the mineral residue of evaporated river or ground water to the content of the same chemical component in rocks (or the earth’s crust). Calculation of water migration indices showed that the most mobile migrants in the biosphere are chlorine, sulfur, boron, bromine, iodine, calcium, sodium, magnesium, fluorine, strontium, zinc, uranium, and molybdenum. The least mobile are silicon, aluminum, iron, potassium, phosphorus, barium, manganese, rubidium, copper, nickel, cobalt, arsenic, lithium.

Undisturbed biogeochemical cycles are almost circular, i.e. almost reserved character. The degree of reproduction (repetition) of cycles in nature is very high (according to V.A. Kovda - 90-98%). Thus, a certain constancy of the composition, quantity and concentration of the components involved in the cycle is maintained. But the incomplete closure of biogeochemical cycles, as we will see later, has a very important geochemical significance and contributes to the evolution of the biosphere. This is why there is a biogenic accumulation of oxygen in the atmosphere, a biogenic and chemogenic accumulation of carbon compounds in the earth’s crust (oil, coal, limestones)

Let's take a closer look at the main parameters of the biogeochemical cycle on land.

The general biogeochemical cycle of elements includes biogeochemical cycles of individual chemical elements. The most important role in the functioning of the biosphere as a whole and individual geosystems of a lower classification level is played by the cycles of several chemical elements that are most necessary for living organisms due to their role in the composition of living matter and physiological processes. These most essential chemical elements include carbon, oxygen, nitrogen, sulfur, phosphorus, etc.

The outstanding Russian scientist Academician V.I. Vernadsky.

Biosphere- the complex outer shell of the Earth, which contains the entire totality of living organisms and that part of the planet’s substance that is in the process of continuous exchange with these organisms. This is one of the most important geospheres of the Earth, which is the main component of the natural environment surrounding humans.

The earth is made up of concentric shells(geospheres) both internal and external. The internal ones include the core and mantle, and the external ones: lithosphere - the rocky shell of the Earth, including the earth's crust (Fig. 1) with a thickness of 6 km (under the ocean) to 80 km (mountain systems); hydrosphere - water shell of the Earth; atmosphere- the gaseous envelope of the Earth, consisting of a mixture of various gases, water vapor and dust.

At an altitude of 10 to 50 km there is a layer of ozone, with its maximum concentration at an altitude of 20-25 km, protecting the Earth from excessive ultraviolet radiation, which is fatal to the body. The biosphere also belongs here (to the external geospheres).

Biosphere - the outer shell of the Earth, which includes part of the atmosphere up to a height of 25-30 km (up to the ozone layer), almost the entire hydrosphere and the upper part of the lithosphere to a depth of approximately 3 km

Rice. 1. Scheme of the structure of the earth’s crust

(Fig. 2). The peculiarity of these parts is that they are inhabited by living organisms that make up living matter planets. Interaction abiotic part of the biosphere- air, water, rocks and organic matter - biotas caused the formation of soils and sedimentary rocks.

Rice. 2. Structure of the biosphere and the ratio of surfaces occupied by basic structural units

Cycle of substances in the biosphere and ecosystems

All chemical compounds available to living organisms in the biosphere are limited. Exhaustibility of digestible chemicals often inhibits the development of certain groups of organisms in local areas land or ocean. According to academician V.R. Williams, the only way to give ultimate properties infinite is to make it rotate along a closed curve. Consequently, the stability of the biosphere is maintained due to the cycle of substances and energy flows. Available two main cycles of substances: large - geological and small - biogeochemical.

Great Geological Cycle(Fig. 3). Crystalline rocks (igneous) are transformed into sedimentary rocks under the influence of physical, chemical and biological factors. Sand and clay are typical sediments, products of transformation of deep rocks. However, the formation of sediments occurs not only due to the destruction of existing rocks, but also through the synthesis of biogenic minerals - the skeletons of microorganisms - from natural resources- waters of the ocean, seas and lakes. Loose watery sediments, as they are isolated at the bottom of reservoirs with new portions of sedimentary material, immersed to depth, and exposed to new thermodynamic conditions (higher temperatures and pressures), lose water, harden, and are transformed into sedimentary rocks.

Subsequently, these rocks sink into even deeper horizons, where the processes of their deep transformation to new temperature and pressure conditions take place - processes of metamorphism occur.

Under the influence of endogenous energy flows, deep rocks are melted, forming magma - a source of new igneous rocks. After these rocks rise to the surface of the Earth, under the influence of weathering and transport processes, they again transform into new sedimentary rocks.

Thus, great gyre is caused by the interaction of solar (exogenous) energy with the deep (endogenous) energy of the Earth. It redistributes substances between the biosphere and the deeper horizons of our planet.

Rice. 3. Large (geological) cycle of substances (thin arrows) and changes in diversity in the earth’s crust (solid wide arrows - growth, broken arrows - decrease in diversity)

By the Great Gyre The water cycle between the hydrosphere, atmosphere and lithosphere, which is driven by the energy of the Sun, is also called. Water evaporates from the surface of reservoirs and land and then returns to Earth in the form of precipitation. Over the ocean, evaporation exceeds precipitation; over land, it is the opposite. These differences are compensated by river flows. IN global circulation land vegetation plays an important role in water. Transpiration of plants in individual areas earth's surface can account for up to 80-90% of precipitation falling here, and on average for all climatic zones- about 30%. Unlike the large cycle, the small cycle of substances occurs only within the biosphere. The relationship between the large and small water cycles is shown in Fig. 4.

Cycles on a planetary scale are created from countless local cyclic movements of atoms driven by the vital activity of organisms in individual ecosystems, and those movements caused by landscape and geological causes (surface and underground runoff, wind erosion, seabed movement, volcanism, mountain building, etc. ).

Rice. 4. Relationship between the large geological cycle (GGC) of water and the small biogeochemical cycle (SBC) of water

Unlike energy, which once used by the body is converted into heat and lost, substances circulate in the biosphere, creating biogeochemical cycles. Of the more than ninety elements found in nature, living organisms need about forty. The most important ones for them are required in large quantities- carbon, hydrogen, oxygen, nitrogen. The cycles of elements and substances are carried out due to self-regulating processes in which all components participate. These processes are waste-free. Exists law of global closure of the biogeochemical cycle in the biosphere, operating at all stages of its development. In the process of biosphere evolution, the role of biological component in closure biogeochemicals
whom the cycle. Humans have an even greater influence on the biogeochemical cycle. But its role manifests itself in the opposite direction (the gyres become open). The basis of the biogeochemical cycle of substances is the energy of the Sun and the chlorophyll of green plants. The other most important cycles—water, carbon, nitrogen, phosphorus, and sulfur—are associated with and contribute to the biogeochemical cycle.

Water cycle in the biosphere

Plants use hydrogen in water during photosynthesis to build organic compounds, releasing molecular oxygen. In the respiration processes of all living beings, during the oxidation of organic compounds, water is formed again. In the history of life, all free water in the hydrosphere has repeatedly gone through cycles of decomposition and new formation in the living matter of the planet. About 500,000 km 3 of water is involved in the water cycle on Earth every year. The water cycle and its reserves are shown in Fig. 5 (in relative terms).

Oxygen cycle in the biosphere

The Earth owes its unique atmosphere with a high content of free oxygen to the process of photosynthesis. The formation of ozone in high layers of the atmosphere is closely related to the oxygen cycle. Oxygen is released from water molecules and is essentially a byproduct of photosynthetic activity in plants. Abiotically, oxygen occurs in upper layers atmosphere due to the photodissociation of water vapor, but this source constitutes only thousandths of a percent of those supplied by photosynthesis. There is a fluid equilibrium between the oxygen content in the atmosphere and the hydrosphere. In water it is approximately 21 times less.

Rice. 6. Diagram of the oxygen cycle: bold arrows - the main flows of oxygen supply and consumption

The released oxygen is intensively consumed in the respiration processes of all aerobic organisms and in the oxidation of various mineral compounds. These processes occur in the atmosphere, soil, water, silt and rocks. It has been shown that a significant portion of the oxygen bound in sedimentary rocks is of photosynthetic origin. The exchange fund O in the atmosphere makes up no more than 5% of the total photosynthetic production. Many anaerobic bacteria also oxidize organic matter through the process of anaerobic respiration, using sulfates or nitrates.

On complete decomposition The organic matter created by plants requires exactly the same amount of oxygen that was released during photosynthesis. The burial of organic matter in sedimentary rocks, coals, and peats served as the basis for maintaining the oxygen exchange fund in the atmosphere. All the oxygen in it goes through a full cycle through living organisms in about 2000 years.

Currently, a significant portion of atmospheric oxygen is bound as a result of transport, industry and other forms of anthropogenic activity. It is known that humanity already spends more than 10 billion tons of free oxygen out of a total amount of 430-470 billion tons supplied by photosynthesis processes. If we take into account that only a small part of photosynthetic oxygen enters the exchange fund, human activity in this regard begins to acquire alarming proportions.

The oxygen cycle is closely related to the carbon cycle.

Carbon cycle in the biosphere

Carbon as a chemical element is the basis of life. He can in different ways combine with many other elements to form simple and complex organic molecules that make up living cells. In terms of distribution on the planet, carbon ranks eleventh (0.35% of the weight of the earth’s crust), but in living matter it averages about 18 or 45% of dry biomass.

In the atmosphere, carbon is part of carbon dioxide CO 2 and, to a lesser extent, methane CH 4 . In the hydrosphere, CO 2 is dissolved in water, and its total content is much higher than the atmospheric one. The ocean serves as a powerful buffer for the regulation of CO 2 in the atmosphere: as its concentration in the air increases, the absorption of carbon dioxide by water increases. Some of the CO 2 molecules react with water, forming carbonic acid, which then dissociates into HCO 3 - and CO 2- 3 ions. These ions react with calcium or magnesium cations to precipitate carbonates. Similar reactions underlie the ocean's buffer system, maintaining a constant pH of water.

Carbon dioxide in the atmosphere and hydrosphere is an exchange fund in the carbon cycle, from where it is taken by terrestrial plants and algae. Photosynthesis underlies all biological cycles on Earth. The release of fixed carbon occurs during the respiratory activity of the photosynthetic organisms themselves and all heterotrophs - bacteria, fungi, animals that are included in the food chain due to living or dead organic matter.

Rice. 7. Carbon cycle

Particularly active is the return of CO2 to the atmosphere from the soil, where the activity of numerous groups of organisms is concentrated, decomposing the remains of dead plants and animals and the respiration of plant root systems takes place. This integral process is referred to as “soil respiration” and makes a significant contribution to the replenishment of the CO2 exchange fund in the air. In parallel with the processes of mineralization of organic matter, humus is formed in soils - a complex and stable molecular complex rich in carbon. Soil humus is one of the important carbon reservoirs on land.

In conditions where the activities of destructors are inhibited by factors external environment(for example, when an anaerobic regime occurs in soils and at the bottom of reservoirs), organic matter accumulated by vegetation does not decompose, turning over time into rocks such as coal or brown coal, peat, sapropels, oil shale and others rich in accumulated solar energy. They replenish the carbon reserve fund, being disconnected from the biological cycle for a long time. Carbon is also temporarily deposited in living biomass, in dead litter, in dissolved organic matter of the ocean, etc. However the main carbon reserve fund in writing are not living organisms or fossil fuels, but sedimentary rocks - limestones and dolomites. Their formation is also associated with the activity of living matter. The carbon of these carbonates is buried for a long time in the bowels of the Earth and enters the cycle only during erosion when rocks are exposed in tectonic cycles.

IN biogeochemical cycle Only fractions of a percent of carbon from the total amount on Earth are involved. Carbon from the atmosphere and hydrosphere passes through living organisms many times. Land plants are able to exhaust its reserves in the air in 4-5 years, reserves in soil humus - in 300-400 years. The main return of carbon to the exchange fund occurs due to the activity of living organisms, and only a small part of it (thousandths of a percent) is compensated by release from the bowels of the Earth as part of volcanic gases.

Currently, the extraction and combustion of huge reserves of fossil fuels is becoming a powerful factor in the transfer of carbon from the reserve to the exchange fund of the biosphere.

Nitrogen cycle in the biosphere

The atmosphere and living matter contain less than 2% of all nitrogen on Earth, but it is what supports life on the planet. Nitrogen is part of the most important organic molecules- DNA, proteins, lipoproteins, ATP, chlorophyll, etc. In plant tissues, its ratio to carbon is on average 1: 30, and in seaweed I: 6. Biological cycle nitrogen is therefore also closely related to carbon.

Molecular nitrogen of the atmosphere is inaccessible to plants, which can absorb this element only in the form of ammonium ions, nitrates, or from soil or aqueous solutions. Therefore, nitrogen deficiency is often a factor limiting primary production—the work of organisms associated with the creation of organic substances from inorganic ones. Nevertheless, atmospheric nitrogen is widely involved in the biological cycle due to the activity of special bacteria (nitrogen fixers).

In the nitrogen cycle great participation also accept ammonifying microorganisms. They decompose proteins and other nitrogen-containing organic substances into ammonia. In the ammonium form, nitrogen is partly reabsorbed by plant roots, and partly is intercepted by nitrifying microorganisms, which is the opposite of the functions of the group of microorganisms - denitrifiers.

Rice. 8. Nitrogen cycle

Under anaerobic conditions in soils or waters, they use nitrate oxygen to oxidize organic substances, obtaining energy for their life. Nitrogen is reduced to molecular nitrogen. Nitrogen fixation and denitrification are approximately balanced in nature. The nitrogen cycle thus depends primarily on the activity of bacteria, while plants integrate into it, using intermediate products of this cycle and greatly increasing the scale of nitrogen circulation in the biosphere through the production of biomass.

The role of bacteria in the nitrogen cycle is so great that if only 20 of their species are destroyed, life on our planet will cease.

Non-biological fixation of nitrogen and the entry of its oxides and ammonia into soils also occurs with rainfall during atmospheric ionization and lightning discharges. The modern fertilizer industry fixes atmospheric nitrogen at levels greater than natural nitrogen fixation in order to increase crop production.

Currently, human activities are increasingly influencing the nitrogen cycle, mainly in the direction of exceeding its conversion into related forms over the processes of return to the molecular state.

Phosphorus cycle in the biosphere

This element, necessary for the synthesis of many organic substances, including ATP, DNA, RNA, is absorbed by plants only in the form of orthophosphoric acid ions (P0 3 4 +). It belongs to the elements that limit primary production both on land and especially in the ocean, since the exchange fund of phosphorus in soils and waters is small. The cycle of this element on the scale of the biosphere is not closed.

On land, plants draw phosphates from the soil, released by decomposers from decomposing organic residues. However, in alkaline or acidic soil the solubility of phosphorus compounds decreases sharply. The main reserve fund of phosphates is contained in rocks created on the ocean floor in the geological past. During rock leaching, part of these reserves passes into the soil and is washed out into water bodies in the form of suspensions and solutions. In the hydrosphere, phosphates are used by phytoplankton, passing through food chains to other hydrobionts. However, in the ocean, most of the phosphorus compounds are buried with the remains of animals and plants on the bottom, with subsequent transition with sedimentary rocks into the large geological cycle. At depth, dissolved phosphates bind with calcium, forming phosphorites and apatites. In the biosphere, in fact, there is a unidirectional flow of phosphorus from the rocks of the land into the depths of the ocean; therefore, its exchange fund in the hydrosphere is very limited.

Rice. 9. Phosphorus cycle

Terrestrial deposits of phosphorites and apatites are used in the production of fertilizers. The entry of phosphorus into fresh water bodies is one of the main reasons for their “blooming”.

Sulfur cycle in the biosphere

The cycle of sulfur, necessary for the construction of a number of amino acids, is responsible for three-dimensional structure proteins, is supported in the biosphere by a wide range of bacteria. Individual links in this cycle involve aerobic microorganisms that oxidize the sulfur of organic residues to sulfates, as well as anaerobic sulfate reducers that reduce sulfates to hydrogen sulfide. In addition to the listed groups of sulfur bacteria, they oxidize hydrogen sulfide to elemental sulfur and then to sulfates. Plants absorb only SO2-4 ions from soil and water.

The ring in the center illustrates the process of oxidation (O) and reduction (R) that exchanges sulfur between the available sulfate pool and the iron sulfide pool deep in the soil and sediments.

Rice. 10. Sulfur cycle. The ring in the center illustrates the process of oxidation (0) and reduction (R), through which sulfur is exchanged between the pool of available sulfate and the pool of iron sulfides located deep in the soil and sediments

The main accumulation of sulfur occurs in the ocean, where sulfate ions continuously flow from land with river runoff. When hydrogen sulfide is released from water, sulfur is partially returned to the atmosphere, where it is oxidized to dioxide, turning into sulfuric acid in rainwater. Industrial use large amounts of sulfates and elemental sulfur and the combustion of fossil fuels release large volumes of sulfur dioxide into the atmosphere. This harms vegetation, animals, people and serves as a source of acid rain, which aggravates negative effects human intervention in the sulfur cycle.

The rate of circulation of substances

All cycles of substances occur at different speeds (Fig. 11)

Thus, the cycles of all biogenic elements on the planet are supported by the complex interaction of different parts. They are formed by the activity of groups of organisms of different functions, the system of runoff and evaporation connecting the ocean and land, the processes of circulation of water and air masses, the action of gravitational forces, the tectonics of lithospheric plates and other large-scale geological and geophysical processes.

The biosphere acts as one complex system, in which various cycles of substances occur. The main driver of these cycles is the living matter of the planet, all living organisms, providing processes of synthesis, transformation and decomposition of organic matter.

Rice. 11. Rates of circulation of substances (P. Cloud, A. Jibor, 1972)

At the heart of the ecological view of the world is the idea that every living creature surrounded by many different factors influencing it, which together form its habitat - a biotope. Hence, biotope - a section of territory that is homogeneous in terms of living conditions for certain types plants or animals(slope of a ravine, urban forest park, small lake or part of a large lake, but with homogeneous conditions - coastal part, deep-water part).

Organisms characteristic of a particular biotope make up life community, or biocenosis(animals, plants and microorganisms of lakes, meadows, shorelines).

A living community (biocenosis) forms a single whole with its biotope, which is called ecological system (ecosystem). Example natural ecosystems can serve as an anthill, lake, pond, meadow, forest, city, farm. Classic example artificial ecosystem is spacecraft. As you can see, there is no strict spatial structure. Close to the concept of an ecosystem is the concept biogeocenosis.

The main components of ecosystems are:

• nonliving (abiotic) environment. These are water, minerals, gases, as well as organic matter and humus;
• biotic components. These include: producers or producers (green plants), consumers or consumers (living beings that feed on producers), and decomposers or decomposers (microorganisms).

Nature operates extremely economically. Thus, the biomass created by organisms (the substance of the bodies of organisms) and the energy they contain are transferred to other members of the ecosystem: animals eat plants, these animals are eaten by other animals. This process is called food, or trophic, chain. In nature, food chains often intersect, forming a food web.

Examples food chains: plant - herbivore - predator; cereal - field mouse- fox, etc. and the food web are shown in Fig. 12.

Thus, the state of equilibrium in the biosphere is based on the interaction of biotic and abiotic environmental factors, which is maintained through the continuous exchange of matter and energy between all components of ecosystems.

In closed circulations of natural ecosystems, along with others, the participation of two factors is necessary: ​​the presence of decomposers and the constant supply of solar energy. In urban and artificial ecosystems there are few or no decomposers, so liquid, solid and gaseous waste accumulate, polluting the environment.

Rice. 12. Food web and direction of flow of matter

Nowadays, plants and animals transform natural environment. Examples of this include coral reefs in the ocean, peat deposits in swamps, the spread of lichens, the spread of algae that destroy mountains, and microorganisms. Almost all chemical elements participate in the biological cycle periodic table D.I. Mendeleev, but among them the main, vital ones stand out.

Carbon. Sources of carbon in nature are as numerous as they are diverse. Meanwhile, only carbon dioxide, which is either in a gaseous state in the atmosphere or in a dissolved state in water, is the source of carbon that serves as the basis for processing it into the organic matter of living beings. Carbon dioxide captured by plants is converted into sugar during photosynthesis, and is converted into proteins, lipids, etc. by other biosynthetic processes. various substances Serve as carbohydrate food for animals and non-green plants. On the other hand, all organisms respire and release carbon into the atmosphere in the form of carbon dioxide. When death occurs, saprophages decompose and mineralize corpses, forming food chains, at the end of which carbon often reenters the cycle in the form of carbon dioxide (the so-called “soil respiration”). Accumulating dead plant and animal residues slow down the carbon cycle: saprophagous animals and saprophytic microorganisms living in the soil convert the residues accumulated on its surface into humus. The rate of influence of organisms on humus is far from the same, and the chains of fungi and bacteria leading to the final mineralization of carbon are of different lengths. As a rule, humus decomposes quickly.
Sometimes the chain may be short and incomplete. In this case, the chain of consumers is unable to act due to lack of air or too high acidity, as a result of which organic residues accumulate in the form of peat and form peat bogs. In some peat bogs with a lush cover of sphagnum mosses, the peat layer reaches 20 m or more. This is where the cycle stops. Accumulations of fossil organic compounds in the form of petroleum indicate that the cycle has slowed down on geological time scales.

The carbon cycle also slows down in water as carbon dioxide accumulates in the form of chalk, limestone, dolomite or coral. Often these masses of carbon remain outside the cycle for entire geological periods until they rise above sea level. From this moment, as a result of the dissolution of limestone and or under the influence of lichens, as well as the roots of flowering plants, the inclusion of carbon and calcium in the cycle begins.

NITROGEN. The nitrogen cycle is quite complex. contains 78% nitrogen, however, in order for it to be used by the vast majority of living organisms, it must be fixed in the form of certain chemical compounds. Nitrogen fixation occurs during the process volcanic activity, during lightning discharges in the atmosphere, during the combustion of meteorites. However, microorganisms, both free-living and living on the roots and sometimes on the leaves of some plants, are of incomparably greater importance in the process of nitrogen fixation. Of the free-living bacteria, nitrogen is fixed by aerobic organisms (i.e., those living with access to oxygen), as well as anaerobic organisms (i.e., living without access to oxygen). The amount of nitrogen fixed by such free-living bacteria ranges from 2 - 3 kg to 5 - 6 kg per 1 ha per year. Blue-green algae living in the soil apparently play a certain role in nitrogen fixation.

Entering the soil with metabolic products and the remains of plants and animals, organic substances decompose into mineral substances, while bacteria convert the nitrogen of organic substances into ammonium salts.

The ability of nitrogen to change its valence over a wide range determines its specific role in the creation of various organic compounds.

Large on the surface of the globe is well known. Evaporation from water bodies caused by solar energy creates atmospheric moisture. This moisture condenses into clouds carried by the wind. When clouds cool, precipitation falls in the form of rain and snow. Precipitation is absorbed by the soil or flows over its surface. Water returns to the seas and oceans. The amount of water evaporated by plants is usually large. If there is a lot of moisture and water for plants, evaporation increases. One birch tree evaporates 75 liters of water per day, beech - 100 liters, linden - 200 liters, and 1 hectare of forest - from 20 to 50 thousand liters. A birch forest, the mass of foliage per 1 hectare is only 4940 kg, evaporates 47 thousand liters of water per day, while a spruce forest, the mass of needles per 1 hectare is 31 thousand kg. - only 43 thousand liters of oxen in laziness. Wheat uses 3750 tons of water per 1 hectare during the development period, which corresponds to 375 mm of precipitation.

Oxygen in quantitative terms is the main component of living matter. If we take into account the water in the tissues, then, for example, the human body contains 62.8% oxygen and 19.4% carbon. Considered as a whole, oxygen, compared to carbon and hydrogen, is its main element.

The oxygen cycle is complicated by the fact that this element can form numerous chemical compounds. As a result, many intermediate cycles arise between and the atmosphere or between and these two environments.

Oxygen, starting from a certain concentration, is very toxic to cells and tissues, even in aerobic organisms. The French scientist Louis Pasteur (1822 - 1895) proved that no living anaerobic organism can withstand oxygen concentrations exceeding atmospheric oxygen by 1% (Pasteur effect).

The oxygen cycle occurs mainly between the atmosphere and living organisms. The process of producing and releasing oxygen as a gas during photosynthesis is the opposite of the process of consuming it during respiration. In this case, organic substances are destroyed and oxygen interacts with hydrogen. In some respects, the oxygen cycle resembles the reverse cycle of carbon dioxide: the movement of one occurs in the direction opposite movement another.

Sulfur. The predominant part of the cycle of this element is of a sedimentary nature and occurs in soil and water. The main source of sulfur available to living beings is all kinds of sulfates. The good solubility of many sulfates in water facilitates the access of inorganic sulfur to ecosystems. By absorbing sulfates, plants restore them and produce sulfur-containing amino acids.

Various organic wastes of the biocenosis are decomposed by bacteria, which ultimately produce hydrogen sulfide from sulfoproteins contained in the soil. Some bacteria can also produce hydrogen sulfide from sulfates, which they reduce under anaerobic conditions. These bacteria, by utilizing sulfates, obtain the energy necessary for their metabolism.

On the other hand, there are bacteria that can again oxidize hydrogen sulfide to sulfates, which again increases the supply of sulfur available to producers. Such bacteria are called chemosynthetic, since they can produce cellular energy without the participation of light, only through the oxidation of simple chemicals. So, in the biosphere, sedimentary rocks contain the main reserves of sulfur, which is found mainly in the form of pyrite, as well as sulfates, such as gypsum.

Phosphorus. The phosphorus cycle is relatively simple and very incomplete. Phosphorus is one of the main constituent elements of living matter, in which it is contained in fairly large quantities. Phosphorus reserves available to living beings are entirely concentrated in the lithosphere. The main sources of inorganic phosphorus are igneous rocks (for example, apatites) or sedimentary rocks (for example, phosphorites). Mineral phosphorus - rare element in the biosphere, in the earth's crust, it is no more than 1%, which is the main factor limiting the productivity of numerous ecosystems. Inorganic phosphorus from rocks of the earth's crust is involved in circulation by leaching and dissolution in continental waters. It enters terrestrial ecosystems, is absorbed by plants, which, with its participation, synthesize various organic compounds, and are thus included in trophic relationships. Then organic phosphates, along with corpses, waste and secretions of living beings, are returned to the ground, where they are again exposed to microorganisms and converted into mineral orthophosphates, ready for consumption by green plants and other autotrophs (from the Greek autos - itself and trophe - food, nutrition).

Phosphorus is brought into aquatic ecosystems flowing waters. Rivers continuously enrich the oceans with phosphates, which promotes the development of phytoplankton and living organisms located at various levels of the food chains of freshwater or marine waters. The history of any chemical element in the landscape consists of countless cycles, varying in scale and duration. Opposite processes - biogenic accumulation and mineralization - form a single biological cycle of atoms.

Tundra landscapes are formed in cold conditions with a short summer period and are therefore unproductive. Low soils are the root cause of many of the tundra's features. “Waves of life” are also associated with heat deficit: in years with more warm summer the production of living matter increases. Some plants bloom in the tundra only in favorable years (for example, fireweed in the Arctic tundra). Plants in the tundra grow slowly. Lichens grow by 1 - 10 mm per year; juniper with a trunk diameter of 83 mm can have up to 544 annual rings. It’s not just the influence low temperatures, but also the absence sufficient quantity nutritional elements.

In many tundras, mosses and lichens play an important role. There are landscapes in which they predominate.

In the tundra, the plant biomass is 170.3 u/ha, of which 72% is in the underground part. The annual increase in biomass is 23.5 c/ha, and the annual litter is 21.9 c/ha. Thus, the true increase equal to the difference between growth and litter, very small - 1.6 c/ha (in the northern taiga - 10 c/ha, in the southern taiga - 30 c/ha, in the humid tropics - 75 c/ha).

Due to the low temperature, the decomposition of the remains of organisms in the tundra is slow; many groups of microorganisms do not function or work very weakly (bacteria that decompose fiber, etc.). This leads to the accumulation of organic matter on the surface and in the soil.

Broad-leaved forests in Russia are distributed in the European part, on,. These are all regions of a humid temperate-warm climate. The biomass here is not much less than in the humid tropics (3000-5000 c/ha), but the annual production and green assimilating mass are several times less. Products range from 80 to 150 c/ha (in the humid tropics - 300 - 500 c/ha), green assimilating mass in oak forests makes up 1% of the biomass and reaches 40 c/ha (8% and 400 c/ha in the humid tropics).

Broad-leaved trees are relatively rich in ash, especially leaves (up to 5%). There is a lot of Ca in the ash of leaves - up to 20% or 0.6 - 3.8% per dry matter, less K (0.15 - 2.0%) and Si (0.4 - 2.8%), even less Mg , A1, P, as well as Fe, Mn, Na, C1.

In the taiga, the biomass is not much inferior to the humid tropics and deciduous forests. In the southern taiga the biomass exceeds 3000 c/ha and only in the northern taiga it drops to 500 - 1500 c/ha. The zoomass in the taiga is negligible (in the southern taiga - 0.01% of biomass).

More than 60% of the biomass is represented by wood, consisting of fiber (about 50%), lignin (20 - 30%), hemicellulose (more than 10%).

The annual production in the southern taiga is almost the same as in broad-leaved forests (85 c/ha versus 90 c/ha in oak forests), in the northern taiga it is much less (40 - 60 c/ha). Plant litter in the southern taiga is less than in oak forests and is equal to 55 c/ha (in oak forests 65 c/ha); in the northern taiga it is even less - 35 c/ha.

The humid tropics occupy large areas in the equatorial, southern and south-central regions. They were even more widespread in past geological eras (from the end of the Devonian). The abundance of heat is combined here with an abundance of precipitation; heat and moisture do not limit the single biological cycle of atoms. atoms occur with the same intensity throughout the year, the periodicity of migration is weakly expressed.
The abundance of heat and moisture determines the large annual production of living matter in the humid tropics. The amount of production here is 2 - 3 times greater than in deciduous forests and taiga, and reaches 300 - 500 c/ha. According to the ratio of biomass and products, above-ground and underground, green and non-green biomass and many other indicators humid tropics also do not differ significantly from other wet forest landscapes. However, in terms of the amount of potassium in biomass, the humid tropics differ from deciduous forests. The biomass of animals in the humid tropics is about 1% of the biomass (45 c/ha). These are mainly termites, ants and other lower animals. According to this indicator, the humid tropics differ sharply from the taiga, in which only 3.6 c/ha of zoomass accumulates (0.01% of biomass). The decomposition of a large mass of organic matter saturates the water with carbon dioxide and organic acids. The main elements that enter the water during the biological cycle are Si and Ca, K. Mg, Al, Fe, Mn, S. The leaves of tropical trees have a high Si content. During the biological cycle, rainwater washes out a large amount of N, P, K, Ca, Mg, Na, CI, S and other elements from the leaves.

Steppes and deserts are similar in many properties. Biomass in the steppes is an order of magnitude less than in forest landscapes - from 100 to 350 c/ha. Most of it, unlike forests, is concentrated in the roots (70 - 90%). The biomass of animals in the steppes is about 6%. Annual production is 13 - 50 c/ha, i.e. 30 - 50% of biomass.

Every year, hundreds of kilograms of water-soluble substances (per 1 ha) are involved in the biological cycle of atoms in the steppes, i.e. significantly more than in the taiga (meadow steppes - 700 kg/ha; southern taiga - 155 kg/ha). In meadow steppes, 700 kg/ha of water-soluble substances are returned annually with litter, and in dry ones - 150 kg/ha (in the spruce forests of the southern taiga - 120 kg/ha). In litter, bases play an important role, completely neutralizing organic acids.

Unlike forest landscapes, steppe soils accumulate 20 - 30 times more organic matter than biomass (in meadow steppes - up to 8000 c/ha of humus; in dry steppes - 1000 - 1500 c/ha). For steppes and deserts, the most characteristic elements are Ca, Na and Mg, which accumulate during salinization in waters, soils and weathering products.

Based on their mineral composition, all steppe grasses are divided into three groups: grasses with a high Si content and a low N content; legumes with significant accumulation of K, Ca and N; forbs occupying an intermediate position.

Biological cycle of substances - consistent, continuous circulation of chemical elements, which occurs due to solar radiation and is maintained by a collection of organisms united through food chains.

(according to the biological author edited by I.G.Pidoplichko K.M., Sitnik, 1974).

The biological cycle of substances consists of the processes of formation of organic substances from elements contained in air, soil, water and the subsequent decomposition of these substances, as a result of which the elements pass into mineral form.

The biological cycle of substances provides the necessary elements of external and internal environment living organisms and maintains its stability. This is, first of all, the cycle of carbon, oxygen, nitrogen, phosphorus, etc.

The cycle of substances is the repeated participation of substances in processes occurring in the atmosphere, hydrosphere and lithosphere, incl. in those layers that are part of the planet’s biosphere. Of particular importance is the circulation of biophilic elements - nitrogen, phosphorus, sulfur. (after Reimers N.F.D., 1990).

The biological cycle is a continuous, cyclical phenomenon, but uneven in time and space and accompanied by more or less significant losses of the natural redistribution of matter, energy and information within ecosystems of various hierarchical levels of organization from biogeocenosis to the biosphere (N.F. Reimers, 1990). A complete circulation of substances within the biogeocenosis does not occur because Some substances always go beyond its boundaries.

The circle of biotic exchange is large (biospheric) - a non-stop, planetary process of a natural cyclical redistribution of matter, energy, and information, uneven in time and space, repeatedly entering (except for the unidirectional flow of energy) into the continuously renewed ecological systems of the biosphere (Reimers N.F., 1990).

And here the main parameter is the environmental efficiency coefficient. The ratio of the biomass of organisms to the amount of organic matter they consume is sometimes called the environmental efficiency coefficient. This coefficient, as a rule, does not exceed 10-20.

The intensity of metabolic processes (metabolism) per unit weight of a living organism is usually greater, the smaller the organism. The reason for this pattern is the significant dependence of the metabolic process on the rate of diffusion of gases through the surface of organisms, which increases per unit of their biomass as their size decreases.

The total value of biomass for the Earth, according to estimates by V.A. Kovda (1969) = 3.10 (12), and over 95% of this value relates to plants and 5% to animals. Of all this, the bulk falls on the forests of the continents.

Assuming that the total productivity of plants on the continents is 140.10 (9) tons, we conclude that the time of one cycle of the circulation of organic matter on the continents is about 20 years. (This probably applies to forests) for others this cycle is shorter, even less for the oceans - for phytoplankton for several days). The duration of one cycle of animal organic matter circulation is several years (the total biomass of animals is about 10 (11) tons and they absorb 10% of the total productivity of plants - hence this calculation). According to data from Huxley (1962), in African savannas the biomass of large wild animals can reach 15-25 t/km2, in temperate forests - 1 t/km2, in the tundra - 0.8 t/km2 .sq.m., in semi-desert - 0.35t/km.sq.m.

The assessment of the biological mass of people and the calculation of energy consumed during their diet is calculated more accurately.

Now (with more than 4 billion people, the biomass of people is about 0.2.10^19 tons. (And now it is already more than 5 billion). A person consumes 2.5.10^3 kcal of energy daily, then the total energy consumption of people is 1.8.10 ^15kcal/year This value approximately corresponds to the modern productivity of agricultural production, i.e. in the modern era, a person consumes about 0.2%! primary production organic world. Several thousand years ago this figure was well below 0.01%, and will continue to rise.

By consuming products, a person consumes technical energy, this new source of heat for our planet.

Since the process of creating organic matter is based on the absorption of carbon dioxide, often called carbon dioxide, from the atmosphere and hydrosphere by autotrophic plants, it must first be analyzed in the global biological cycle. There is about 2.3.10^12 of it in the atmosphere, i.e. 0.032% of all atmospheric air (volume %). In the hydrosphere there is more than 130.10^12 tons. It varies little in different geographical areas and with altitude. The reason is the independence of carbon dioxide content from temperature. The main components of the carbon dioxide cycle are determined by biological processes, and a little by geological ones. Consumption for photosynthesis per year is 3.10^17 (these are carbonate). The average time for the renewal of carbon dioxide in the atmosphere was about 10 years.

Now let's move on to considering individual cycles in the biosphere. Basic driving force cycles of substances on the planet is living matter. It is living matter, or rather its activity through a system of cycles, that ensures the progressive development of the Earth's biosphere. The cycle of matter and energy is based on two opposing processes - creation and destruction. The first ensures the formation of living matter and the accumulation of energy, the second ensures the destruction of complex organic compounds and their transformation into simple minerals: carbon dioxide, water, various salts, etc. The biosphere exists due to (thanks to) a continuous cycle. We have already noted earlier that the energy basis for the existence of biological cycles is the process of photosynthesis. During this process (it is precisely this process that represents the ascending branch of the biological cycle in energetic terms) huge amount energy (solar) converted into potential chemical energy (chemical) of organic substances. The descending branch (energetically speaking) is all the others life processes, in which the transformations of biological compounds created during photosynthesis and the use of stored energy occur. These processes end with the oxidation and mineralization of organic substances, degradation and conversion into heat of the energy stored in the chemical bonds of these substances.