Secondary productivity of ecosystems. Primary and secondary production

The ability of living organisms to create new biomass is called productivity. The rate of biomass formation per unit time per unit area is called products. Biological products are expressed in joules per 1 m 2 per day, calories per 1 m 2 per day, kilograms per 1 ha per one year.

The organic mass created by a plant per unit of time is called primary products. Gross primary production is the total amount of matter and energy produced by the autotrophs of an ecosystem. Net primary production – the rate of accumulation of organic matter in plant tissues after subtracting the cost of respiration. Consumers can only use pure primary products.

Secondary products in ecosystems are formed by consumers. The secondary production of the community is always less than the primary production. According to the pyramid of biological production at each previous trophic level, the amount of biomass created per unit of time is greater than at the next one.

The amount of energy supplied per year to a certain area depends on the latitude of this area and on the cloud cover, i.e. from factors that promote photosynthesis. The average productivity of land areas corresponds to the assimilation of approximately 0.3% of the light energy reaching the Earth's surface.

Four groups of areas have been identified that differ in the primary productivity of ecosystems:

1) open seas and deserts (productivity is usually less than 500-1000 kcal / m 2 per year;

2) herbaceous semi-arid formations, some agrocenoses, deep lakes, alpine forests, maritime littoral (500-3000 kcal/m 2 per year;

3) moist forests, shallow lakes, pastures and most agrocenoses (300-10000 kcal/m 2 per year);

4) some estuaries, coral reefs (more than 10,000 kcal/m2 per year).

The quality of food and the distribution of energy to perform the various functions of organisms determines the nature of the flow of energy through the community. The strongest differences in this regard exist between aquatic and terrestrial ecosystems. Productivity reaches its highest level in those places where there is an abundance of light, heat, water and mineral nutrients.

Humidity and temperature are usually the first important factors limiting the productivity of terrestrial systems, and mineral elements are the second. The availability of moisture to compensate for such losses is the main determinant of land productivity. There is an almost linear relationship between precipitation and net primary production, increasing with the increase in mean annual precipitation. In temperate and arctic ecosystems, low winter temperatures and long nights reduce productivity. The ecosystems of swamps and marshes are on the verge between terrestrial and aquatic habitats, and in terms of plant productivity they correspond to tropical forests. Plants that live on marches are highly productive, since their roots are constantly under water, and their leaves are in the light and in the air. In addition, they are abundantly supplied with nutrients, because the detritus washed into the marches is quickly decomposed by bacteria.

IN aquatic ecosystems energy is quickly and very efficiently transferred from one trophic level to another, which creates the possibility for the formation of long food chains. The main factor limiting the productivity of aquatic ecosystems is a small amount of mineral nutrients. This limits productivity by almost one order of magnitude compared to the productivity of temperate forests. Phosphorus is one of the most deficient elements of mineral nutrition in the waters of the open ocean.

In the zones of upwelling (where nutrients are carried to the surface from the depths of the sea by vertical currents) and the continental shelf (where there is an active exchange between bottom sediments and surface waters), the production is higher, averaging 500 and 360 g/m2 per year, respectively. The production of shallow estuaries, coral reefs, and coastal kelp beds approaches that of neighboring terrestrial habitats. Freshwater ecosystems have a fairly wide range of products. Productivity is highest at the land-water interface: in certain wet or aquatic terrestrial communities and in some coastal and shallow water communities of aquatic ecosystems.

BIOLOGICAL PRODUCTIVITY - the increase in organic matter of biomass produced by biocenosis per unit of time per unit area.[ ...]

The primary productivity of an ecosystem, community, or any part of them is defined as the rate at which solar energy is absorbed by producing organisms (mainly green plants) during photosynthesis or chemical synthesis (chemoproducers). This energy materializes in the form of organic substances of tissue producers.[ ...]

PRODUCTIVITY (production) PRIMARY - biological productivity (production) of producers (mainly phytocenosis). PRODUCTS - see Biological products.[ ...]

PRIMARY POLLUTANTS - pollutants directly entering or emitted into environment from sources of pollution. P.z.v. can contribute to the formation and accumulation of secondary pollutants in the environment. DISCHARGE OF DRAIN (rivers) - a change in the natural direction of the flow of rivers with its withdrawal to another catchment basin with the help of hydraulic structures (GOST 19185-73). OVERGRADING, overgrazing - uncontrolled grazing of livestock, leading to the degradation of pasture vegetation and a decrease in its productivity and productivity (the so-called pasture digression) and the formation of slaughter.[ ...]

PRIMARY PRODUCTIVITY - see Primary Productivity.[ ...]

The primary productivity of vegetation (producers) of an ecosystem determines the total energy of biochemical processes in an ecosystem and, consequently, the intensity of biogeochemical cycles of both carbon and other biogenic elements. The biogeochemical cycle of carbon, the determining element of living systems, is better studied than the cycles of other elements that are involved in the biogenic cycle with a relatively small part of their presence in earth's crust or atmosphere. Nevertheless, the biogeochemical cycles of nitrogen and oxygen have been studied relatively fully, at least in terms of their exchange in ecosystems and the atmosphere.[ ...]

The primary data of long-term observations, carried out according to a strictly defined program, are entered in the "Chronicle of Nature" of each reserve. From year to year, the dates of opening of rivers, the timing of flowering of plants, the arrival of birds, information on the number of main animal species, crops of seeds, berries, mushrooms and various natural phenomena are recorded in it from year to year. This allows us to judge the degree of constancy of these phenomena, understand the patterns of their change, make forecasts and develop ways to increase the biological productivity of natural biogeocenoses.[ ...]

The productivity of ecosystems is closely related to the flow of energy passing through an ecosystem. In each ecosystem, part of the incoming energy entering the food web is stored in the form of organic compounds. Non-stop production of biomass (living matter) is one of the fundamental processes of the biosphere. Organic matter created by producers in the process of photosynthesis or chemosynthesis is called the primary production of an ecosystem (community). Quantitatively, it is expressed in raw or dry mass of plants or in energy units - the equivalent number of calories or joules. Primary production determines the total energy flow through the biotic component of the ecosystem, and, consequently, the biomass of living organisms that can exist in the ecosystem (Fig. 12.44).[ ...]

PRIMARY PRODUCTIVITY - biomass (aboveground and underground organs), as well as energy and biogenic volatile substances produced by producers per unit area per unit time. Since P. p. depends on the intensity of photosynthesis, and the latter depends on the content of carbon dioxide in the air, an increase in primary productivity was assumed due to an increase in the concentration of CO2 in the Earth's atmosphere. However, due to other anthropogenic impacts (environmental pollution, etc.) and the replacement of more productive biotic communities by less productive ones, the biological productivity on the planet has decreased over Lately by 20%.[ ...]

Net primary productivity (NPP) - the rate of accumulation of organic matter by plants minus the consumption for respiration and photorespiration.[ ...]

Net primary productivity - the rate of accumulation of organic matter in plant tissues minus that part of it that was used for respiration (R) of plants during the study period: Рl / = Рv R.[ ...]

Gross primary productivity (GPP) is the rate at which plants store chemical energy.[ ...]

Gross primary productivity is the rate of accumulation of organic matter in the process of photosynthesis, including that part of it that will be spent on respiration during the measurements. It is designated Ra and expressed in units of mass or energy per unit area or volume per unit time.[ ...]

Tertiary productivity at the level of predators is about 10% of secondary productivity and can rarely reach 20%. Thus, the primary energy is rapidly reduced in the transition from lower to higher levels.[ ...]

Biomass and primary productivity of the main types of ecosystems are presented in Table 12.7 and fig. 12.45.[ ...]

In the most productive areas, the synthesis of organic matter occurs very intensively. Thus, in the Mediterranean Sea, primary production in April is on average at the level of 10 mg C/(m2-day) in the surface water layer and 210 mg C/(m2-day) in the entire photosynthesis layer. Significantly higher productivity - up to 580 mg C/(m2 ■ day) in the photosynthesis layer is observed in the zone of cyclonic circulation. A similar value is also typical for upwelling areas: the average daily production integrated over a depth of 0-2000 m in the Pacific Ocean off the coast of California is at the level of 560 mg C/m2.[ ...]

Indicators of primary and secondary productivity for the main ecosystems are given in Table. 6.1.[ ...]

For plants, the productivity of an environment can depend on whichever resource or condition is most restrictive of growth. In terrestrial communities, a decrease in temperature and a decrease in the duration of the growing season with height generally lead to a decrease in production, while in water bodies, the latter, as a rule, decreases with depth in parallel with temperature and illumination. There is often a sharp decrease in production in arid conditions, where growth can be limited by a lack of moisture, and its increase is almost always when the influx of key nutrients, such as nitrogen, phosphorus and potassium, increases. In the broadest sense, the productivity of the environment for animals follows the same patterns, since it depends on the amount of resources in the base the food chain, temperature and other conditions.[ ...]

Biological productivity - total organic matter (biomass) produced by a population or community per unit of time per unit area. At the same time, a distinction is made between the primary biomass produced in the process of photosynthesis by autotrophs (green plants), and the secondary biomass obtained by heterotrophs per unit of time per unit area. Primary production is divided into gross (equal to the total number of photosynthesis products for a certain period of time) and net (equal to the difference between the gross and the part that was used for plant respiration). In herbaceous plants, 40-50% is used for respiration, and in trees - 70-80% of the gross primary production.[ ...]

Almost all of the net primary production of the Earth serves to support the life of all heterotrophic organisms. Energy, underused by consumers, is stored in their bodies, soil humus and organic sediments of water bodies. Human nutrition is mostly provided by agricultural crops, which occupy about 10% of the land area. The annual growth of cultivated plants is approximately 16% of the total land productivity, most of which falls on forests.[ ...]

Pointing more than 100 years ago to the primary, main significance of the environment in shaping the composition and productivity of the forest, Morozov G.F. acted as a forerunner of modern ecology and biology in forestry.[ ...]

From lines 1a-b of Table. Figure 6.4 shows that the primary production of plant biomass (expressed as carbon) in the ocean is about half that on land. Almost all of these products are related to phytoplankton. The distribution of the biological productivity of the ocean for various types of organisms is given in Table. 6.6 (according to the Institute of Oceanology of the Academy of Sciences of the USSR).[ ...]

From Table. 1.3 clearly shows that land ecosystems are the most productive. Although the land area is half that of the oceans, its ecosystems have an annual primary carbon production more than twice that of the World Ocean (52.8 billion tons and 24.8 billion tons, respectively) with a relative productivity of terrestrial ecosystems 7 times the productivity of ocean ecosystems. From this, in particular, it follows that the hopes that the full development of the biological resources of the ocean will allow mankind to solve the food problem are not very well founded. Apparently, the opportunities in this area are small - even now the level of exploitation of many populations of fish, cetaceans, pinnipeds is close to critical, for many commercial invertebrates - mollusks, crustaceans and others, due to a significant drop in their numbers in natural populations, it has become economically profitable to breed them on specialized marine farms, the development of mariculture. The situation is approximately the same with edible algae, such as kelp (seaweed) and fucus, as well as algae used in industry to obtain agar-agar and many other valuable substances.[ ...]

On the territory of Russia, in zones of sufficient moisture, primary productivity increases from north to south, with an increase in heat inflow and the duration of the growing season (season). The annual growth of vegetation varies from 20 centner/ha on the coast and islands of the Arctic Ocean to more than 200 centner/ha in Krasnodar Territory, on the Black Sea coast of the Caucasus (Fig. 12.46).[ ...]

The stability of plant communities can be characterized by their primary biological productivity (PBP) - the average value of the above-ground and underground organic mass increasing over the year, which is measured in dry mass (c/ha). GGBP depends on the resources of heat and moisture, as well as on the nature of the soil, amounting within Russia for the Arctic tundra 10 c/ha, for the meadow steppe 100-110 and for areas poorly provided with moisture (semi-deserts) 7-10 c/ha. [ . ..]

Not only the organic remains of dead plants (primary organic matter) enter the soil, but also the products of their microbiological transformation, as well as animal remains (secondary organic matter). The primary productivity of various terrestrial ecosystems is not the same and ranges from 1-2 t/ha per year of dry organic matter ( different kinds tundra) up to 30-35 t/ha per year (moist tropical forests) (see Table 3). In agroecosystems, plant residues enter the soil from 2-3 t/ha per year (row crops) to 7-9 t/ha per year (perennial grasses). Almost all soil organic matter is processed by microorganisms and representatives of the soil fauna. The final products of this processing are mineral compounds. However concrete ways transformations of primary organic compounds and the formation of organic products of various stability and complexity, their participation at various stages of transformation in soil formation and plant nutrition remain largely unexplored.[ ...]

The second type of anthropogenic influence - the enrichment of the reservoir with biogenic substances - increases the productivity of not only phytoplankton, but also other aquatic communities, including fish, and it should be considered as a process that is favorable from an economic point of view. However, in many cases, spontaneous anthropogenic enrichment of water bodies with primary nutrients occurs on such a scale that the water body as an ecological system is overloaded with nutrients. The consequence of this is an excessively rapid development of phytoplankton (“blooming” of water), during the decomposition of which hydrogen sulfide or other toxic substances are released. This leads to the death of the animal population of the reservoir and makes the water undrinkable.[ ...]

All studied BGCs were identified typologically, after which they were ordinated according to the productivity gradient and the successional age factor. On drained ecotopes, 4 succession rows were identified with a common scheme: river willow forests - ■ floodplain forest types (pine forests, birch forests, oak forests, gray alder forests) - ■ floodplain spruce forests -»■ sorrel spruce forests (climax). For each succession series, the computer approximated and equalized the values ​​of primary net production P, stocks of live phytomass M, and total biomass stock B along the ordinate of successional age (g). Having calculated the first derivative of the functions M and B with respect to m, we obtained the current change in the stocks of live phytomass of the DM and the entire biomass of the DW. Then, for each decade of the successional age, the average value of the annual litter and mortality of the phytomass L was calculated using the formula A = P - DM and the cost of heterotrophic respiration H/1 using the formula R = P - DV. The value of b represents the dissipation (scattering) of the energy reserves of the autotrophic block, and d/, - the heterotrophic block of BHC. The value of b also characterizes the input flow of chemical energy into the heterotrophic block. After approximating the values ​​of stocks in the BGC of dead organic matter and the biomass of destructors (detritus) - £detr obtained from the equation detr = V - M, the values ​​of DAde™ - the current change in the stocks of dead biomass and destructors . The adequacy check was carried out by comparing the results with the values ​​obtained from the equation

Each biogeocenosis is characterized by species diversity, population size and density of each species, biomass and productivity. The number is determined by the livestock of animals or the number of plants in a given territory (river basin, sea area, etc.). This is a measure of the abundance of a population. Density is characterized by the number of individuals per unit area. For example, 800 trees per 1.ha of forest or the number of people per 1 km2. Primary productivity is the increase in plant biomass per unit of time per unit area. Secondary productivity is the biomass formed by heterotrophic organisms per unit of time per unit area. Biomass is the total set of plant and animal organisms present in the biogeocenosis at the time of observation.[ ...]

One of the promising approaches to assessing the state of the natural environment is to control the biogenic cycle of substances and the productivity of biota. The state of biogeocenosis, according to D.A. Krivolutsky and E.A. Fedorov (1984), objectively characterize such indicators as the stock of nutrients available to plants (nitrogen, phosphorus); primary and secondary productivity of ecosystems. With prolonged exposure to pollutants, even at very low concentrations, possible environmental impact may appear after a long time. To predict these consequences and their timely prevention, one can use such sensitive indicators as the amount of pollen and seeds, the frequency of chromosome disorders in meristem cells, the fractional composition of plant tissue proteins.[ ...]

As already mentioned, the total amount of a substance formed during photosynthesis in a certain period of time is called gross primary production. Part of the primary production is used by plants as an energy source. The difference between gross primary production and the fraction of organic matter used by plants is called net primary production and is available for consumption by organisms at higher trophic levels. In table. 17.1 shows data on the productivity of the North Sea. The total total fish catch contains less than 0.1% of the energy value in the gross primary production. This surprising, at first glance, fact is explained by the large loss of energy at each level of the food chain and the large number of trophic levels between the first trophic level and the level whose products are used by people, in this case, fish. The ratio of net primary production to the installed stock is called the renewal rate constant, which shows how many times a year the population changes.[ ...]

The process of photosynthesis is the main source of the appearance of all organic substances in natural waters, their range and concentration. As is known, phytoplankton is characterized by the highest productivity, which, along with forests, determines the oxygen content in the atmosphere. The destruction of phytoplankton (detritus and its decomposition products) is the first and main source of organic matter in natural waters. Therefore, it is no coincidence that in the general list of water indicators to be determined, an important place is occupied by the measurement of primary production and destruction and the determination of the number of bacterial and phytoplankton cells associated with this measurement. It is obvious that the magnitude of primary production and destruction largely determines the magnitude of the independently determined concentration of oxygen dissolved in water. The second source of organic matter in natural waters is surface and subsoil runoff, which contains degradation products of tree leaves and vegetation cover. A clear illustration of the significance of this source can be the high-colored left-bank tributaries of the Volga, flowing through peatlands, as well as the high content of organic substances in the melt waters of floods.[ ...]

It should be emphasized that in Table. Table 5 shows generalized data on "long-term" energy transfers, i.e., for a year or for an even longer period of time. During the most productive time of the growing season, especially during long summer days in the north, more than 5% of the total daily solar energy input can turn into gross output, and more than 50% of the gross output can turn into net primary production per day (Table 6). But even under the most favorable conditions, such a high daily productivity cannot be maintained throughout the year, and it is impossible to obtain such high yields on large agricultural areas (compare the data given in Table 6 with the figures in the last column of Table 11).[ ... ]

Biomass is understood as the usual number of organisms (by mass or volume) per 1 m3 or per 1 m2 of area. The amount of biomass formed in a certain time is called productivity. In the modern era, the primary productivity of living organisms is determined by the photosynthesis of autotrophic plants. But everything is involved in the retention and transformation of energy resources created by autotrophic plants. living matter planets. The total mass of the living matter of the Earth, according to the calculations of V. I. Vernadsky, amounts to hundreds of billions of tons and includes 500 thousand plant species and about 2 million animal species.[ ...]

In mixed and broad-leaved forests, there is a large reserve of organic matter, in which the living biomass is about 45% (90% of plants). Forests have high soil fertility. The value of the primary productivity of phytomass is very significant, broad-leaved forests are able to effectively maintain the oxygen regime.[ ...]

Soils of agroecosystems degrade to the greatest extent. The reason for the unstable state of agroecosystems is due to their simplified phytocenosis, which does not provide optimal self-regulation, structure and productivity constancy. And if in natural ecosystems biological productivity is ensured by the action of natural laws of nature, then the yield of primary production (crop) in agroecosystems depends entirely on such a subjective factor as a person, the level of his agronomic knowledge, technical equipment, socio-economic conditions, etc., and therefore remains inconsistent.[ ...]

The main requirements for the well completion processes are given, the technology and technique of opening, fixing, and testing the development of wells are outlined. The properties of drilling and cement slurries, materials and chemicals are described in relation to the primary and secondary opening of productive formations. The methods of stimulation of inflow and exploration of wells, methods of influencing the bottomhole zone are highlighted. Methods for assessing the quality of opening, fixing, testing and development of wells are outlined. Particular attention is paid to the preservation of the reservoir properties of productive objects.[ ...]

The input of the system is the flow of solar energy. Most of it is dissipated as heat. Part of the energy effectively absorbed by plants is converted during photosynthesis into the energy of chemical bonds of carbohydrates and other organic substances. This is the gross primary production of the ecosystem. Part of the energy is lost during plant respiration, and part is used in other biochemical processes in the plant and eventually also dissipated in the form of heat. The remaining part of the newly formed organic matter determines the increase in plant biomass - the net primary productivity of the ecosystem.[ ...]

Over billions of years of evolution, nature has developed the most effective ways restoration of the Le Chatelier principle in the shortest possible time. The decisive role in this process is played by virgin territories with undistorted biota, characterized by complete closure of the circulation of substances and high productivity. Therefore, in order to reduce anthropogenic disturbance and restore the operation of the Le Chatelier principle in the biosphere, it is necessary to stop the expansion of economic activity on a global scale and stop the development of natural areas of the biosphere that have not yet been distorted by civilization, which should become real sources of restoration of the biosphere. The most productive communities on the continents are forests and swamps, among which tropical communities have the highest productivity. The productivity of these communities is 4 times higher than the productivity of the corresponding communities of temperate zones. Therefore, from the point of view of the efficiency of disturbance compensation external environment, according to Le Chatelier's principle, a unit area of ​​primary tropical forests and marshes is equivalent to four units of area occupied by forests and marshes in the temperate zone. The secondary forest growing on clearings has about a thousand times worse closure of the cycle of substances and the ability to compensate for environmental disturbances than virgin forests and swamps. Only about 300 years after cutting down, the restoration process ends and the forest returns to its original undisturbed state. Periodic deforestation, which now takes place on average 50 years later, as economically viable timber is formed, interrupts the process of restoration of the primary forest with a closed cycle of substances and the ability to compensate for external disturbances.[ ...]

There are calculations showing that 1 hectare of some forest annually receives an average of 2.1 109 kJ of solar energy. However, if all the plant matter stored during the year is burned, then as a result we will receive only 1.1 106 kJ, which is less than 0.5% of the energy received. This means that the actual productivity of photosynthetics (green plants), or primary productivity, does not exceed 0.5%. Secondary productivity is extremely low: 90-99% of energy is lost during the transfer from each previous link of the trophic chain to the next. If, for example, per 1 m2 of the soil surface, plants created an amount of a substance equivalent to approximately 84 kJ per day, then the production of primary consumers will be 8.4 kJ, and secondary ones will not exceed 0.8 kJ. There are specific calculations that for the formation of 1 kg of beef, for example, 70-90 kg of fresh grass is needed.[ ...]

Solar energy can be converted into the energy of organic matter with an efficiency close to unity. However, the observed efficiency of photosynthesis is much lower than this value. The reason for this situation is explained by the fact that in natural ecosystems the efficiency of photosynthesis is limited by other factors. Thus, in the ocean, primary productivity is limited by the concentrations of nitrogen and phosphorus, which cannot be increased by biota. On land, the productivity of plants is limited by moisture, the reserves of which are regulated by biota only within certain limits.[ ...]

Apparently, the most rational way to control the population is the territoriality of animals. Each territory belongs to only one self-reproducing individual, which protects it from all competitors (by sound signals, through scent marks, etc.). The size of the territory and their possible correlation with primary productivity is fixed genetically.[ ...]

The total energy flow that characterizes an ecosystem consists of solar radiation and long-wave thermal radiation received from nearby bodies. Both types of radiation determine the climatic conditions of the environment (temperature, the rate of water evaporation, air movement, etc.), but photosynthesis, which provides energy to the living components of the ecosystem, uses only a small part of the energy of solar radiation. Due to this energy, the main, or primary, products of the ecosystem are created. Therefore, the primary productivity of an ecosystem is defined as the rate at which radiant energy is used by producers in the process of photosynthesis, accumulating in the form of chemical bonds of organic substances. Primary productivity P is expressed in units of mass, energy or equivalent units per unit time.[ ...]

The development of stratification generally causes oxygen leakage from the hypolimnion, which may result in the formation of anaerobic bottom waters incapable of oxidation. bottom sediments. Under such conditions, a large amount of organic matter can be preserved. The surface waters of stratified lakes are usually depleted in phosphorus and nitrogen due to the incorporation of these elements into the tissues of planktonic organisms, which sink and accumulate below the thermocline. This removal of nutrients from surface water strongly affects their primary productivity. The primary productivity of Lake Kivu, which has a well-defined constant thermocline, is only one quarter of that of Lake Edward or Mobutu Sese Seko in East Africa, which are approximately the same size and chemically similar but less sharply stratified.

produced by the ecosystem. Distinguish: total primary production(gross production) - the total amount of organic matter and energy recorded by all autotrophs of the ecosystem; pure primary products(net production) - the same, minus the substances spent on respiration by autotrophs; secondary products- the amount of organic matter produced by consumers (phytotrophs and zootrophs); net secondary products- the same, minus the substances used for breathing by consumers; product stock- the amount of biomass accumulated by organisms in the community. From an economic point of view, a distinction is made between total products in the form of valuable organic matter, useful products and the stock of useful products.

Ecological encyclopedic Dictionary. - Chisinau: Main edition of the Moldavian Soviet encyclopedia . I.I. Grandpa. 1989

See what "ECOSYSTEM PRODUCTION" is in other dictionaries:

Ecological dictionary

See Art. Ecosystem products. Ecological encyclopedic dictionary. Chisinau: Main edition of the Moldavian Soviet Encyclopedia. I.I. Grandpa. 1989... Ecological dictionary

1) net primary production of the ecosystem; 2) increase in phytomass used by humans. Ecological encyclopedic dictionary. Chisinau: Main edition of the Moldavian Soviet Encyclopedia. I.I. Grandpa. 1989. Net production of biocenosis ... Ecological dictionary

- (gross) the same as Biological production of the ecosystem. Ecological dictionary, 2001 ... Ecological dictionary

- (B.p.) the ability of organisms to produce organic matter in the course of their life. B.p. measured by the amount of organic matter created per unit time per unit area (t/ha/year, g/m2/day, etc.). Distinguish… … Ecological dictionary

The ability of organisms to produce organic matter in the course of their life. B.p. measured by the amount of organic matter created per unit time per unit area (t/ha/year, g/m2/day, etc.). Distinguish between primary... Glossary of business terms

- (USSR) the most peculiar, but relatively low-productive ecosystems of a sharply continental arid climate. Low xerophilic, psammoxerophilic and haloxerophyllic semi-trees (up to 8 m high), semi-shrubs and shrubs dominate,… … Ecological dictionary

- (USSR) ecosystems of arid continental climate dominated by xerophilous narrow-leaved grasses (feather grass, oats, fescue). Subdominants are forb species, and in the most continental areas and rare low xerophilous shrubs ... ... Ecological dictionary

CORAL REEFS Submerged or partially surface calcareous structures formed primarily by the skeletons of colonial coral polyps (see CORAL POLYPS) in shallow areas of tropical seas. Within an ecosystem (see ... ... encyclopedic Dictionary

Ecosystem, or ecological system (from other Greek οἶκος dwelling, location and σύστημα system) a biological system consisting of a community of living organisms (biocenosis), their habitat (biotope), a system of connections, ... ... Wikipedia

Every year, people are depleting the resources of the planet more and more. It is not surprising that recently an assessment of how many resources a particular biocenosis can provide has become of great importance. Today, the productivity of the ecosystem is of decisive importance when choosing a method of management, since the economic feasibility of the work directly depends on the amount of production that can be obtained.

Here are the main questions facing scientists today:

• How much solar energy is available and how much is assimilated by plants, how is this measured?
• Which have the highest productivity and which give the most primary production?
• What is the quantity locally and worldwide?
• What is the efficiency with which energy is converted by plants?
• What are the differences between assimilation efficiency, net production and ecological efficiency?
• How Ecosystems Differ in Biomass Amount or Volume
• How much energy is available to people and how much do we use?

We will try to at least partially answer them within the framework of this article. First, let's deal with the basic concepts. So, the productivity of an ecosystem is the process of accumulation of organic matter in a certain volume. What organisms are responsible for this work?

Autotrophs and heterotrophs

We know that some organisms are capable of synthesizing organic molecules from inorganic precursors. They are called autotrophs, which means "self-feeding". Actually, the productivity of ecosystems depends on their activities. Autotrophs are also referred to as primary producers. Organisms that are able to produce complex organic molecules from simple inorganic substances (water, CO2) most often belong to the class of plants, but some bacteria have the same ability. The process by which they synthesize organics is called photochemical synthesis. As the name implies, photosynthesis requires the presence of sunlight.

We must also mention the pathway known as chemosynthesis. Some autotrophs, mainly specialized bacteria, can convert inorganic nutrients into organic compounds without access to sunlight. There are several groups in the maritime and fresh water, and they are especially common in environments with a high content of hydrogen sulfide or sulfur. Like chlorophyll-bearing plants and other organisms capable of photochemical synthesis, chemosynthetic organisms are autotrophs. However, the productivity of the ecosystem is rather the activity of vegetation, since it is she who is responsible for the accumulation of more than 90% of organic matter. Chemosynthesis plays an incommensurably smaller role in this.

Meanwhile, many organisms can obtain the necessary energy only by eating other organisms. They are called heterotrophs. In principle, these include all the same plants (they also “eat” ready-made organic matter), animals, microbes, fungi and microorganisms. Heterotrophs are also called "consumers".

The role of plants

As a rule, the word "productivity" in this case refers to the ability of plants to store a certain amount of organic matter. And this is not surprising, since only plant organisms can convert inorganic substances into organic ones. Without them, life itself on our planet would be impossible, and therefore the productivity of the ecosystem is considered from this position. In general, the question is extremely simple: so how much organic matter can plants store?

What biocenoses are the most productive?

Oddly enough, but human-created biocenoses are far from the most productive. Jungles, swamps, selva of large tropical rivers are far ahead of them in this regard. In addition, it is these biocenoses that neutralize a huge amount of toxic substances, which, again, enter nature as a result of human activity, and also produce more than 70% of the oxygen contained in the atmosphere of our planet. By the way, many textbooks still state that the Earth's oceans are the most productive "breadbasket". Oddly enough, but this statement is very far from the truth.

"Ocean Paradox"

Do you know what the biological productivity of the ecosystems of the seas and oceans is compared to? With semi-deserts! Large volumes of biomass are explained by the fact that it is water expanses that occupy most of the planet's surface. So the repeatedly predicted use of the seas as the main source of nutrients for all mankind in the coming years is hardly possible, since the economic feasibility of this is extremely low. However, low productivity ecosystems of this type in no way detracts from the importance of the oceans for the life of all living things, so they need to be protected as carefully as possible.

Modern environmentalists say that the possibilities of agricultural land are far from being exhausted, and in the future we will be able to get more abundant harvests from them. Special hopes are placed on which they can produce a huge amount of valuable organic matter due to their unique characteristics.

Basic information about the productivity of biological systems

In general, the productivity of an ecosystem is determined by the rate of photosynthesis and the accumulation of organic matter in a particular biocenosis. The mass of organic matter that is created per unit of time is called primary production. It can be expressed in two ways: either in Joules, or in the dry mass of plants. Gross production is its volume created by plant organisms in a certain unit of time, at a constant rate of the photosynthesis process. It should be remembered that part of this substance will go to the vital activity of the plants themselves. The remaining organics after this is the net primary productivity of the ecosystem. It is she who goes to feed heterotrophs, which include you and me.

Is there an "upper limit" to primary production?

In short, yes. Let's take a quick look at how efficient the process of photosynthesis is in principle. Recall that the intensity of solar radiation reaching the earth's surface is highly dependent on location: the maximum energy return is characteristic of the equatorial zones. It decreases exponentially as it approaches the poles. Approximately half of the solar energy is reflected by ice, snow, oceans or deserts, and absorbed by gases in the atmosphere. For example, the ozone layer of the atmosphere absorbs almost all ultraviolet radiation! Only half of the light that hits the leaves of plants is used in the photosynthesis reaction. So the biological productivity of ecosystems is the result of the transformation of an insignificant part of the sun's energy!

What is secondary production?

Accordingly, secondary production is the increase in consumers (that is, consumers) for a certain period of time. Of course, the productivity of the ecosystem depends on them to a much lesser extent, but it is this biomass that plays the most important role in human life. It should be noted that secondary organics are separately calculated at each trophic level. Thus, the types of ecosystem productivity are divided into two types: primary and secondary.

The ratio of primary and secondary production

As you might guess, the ratio of biomass to total plant mass is relatively low. Even in the jungle and swamps, this figure rarely exceeds 6.5%. The more herbaceous plants in the community, the higher the rate of accumulation of organic matter and the greater the discrepancy.

On the rate and volume of formation of organic substances

In general, the limiting rate of formation of organic matter of primary origin completely depends on the state of the photosynthetic apparatus of plants (PAR). The maximum value of photosynthesis efficiency, which was achieved in laboratory conditions, is 12% of the PAR value. Under natural conditions, a value of 5% is considered extremely high and practically does not occur. It is believed that on Earth the assimilation of sunlight does not exceed 0.1%.

Distribution of primary production

It should be noted that productivity natural ecosystem- the thing is extremely uneven on the scale of the entire planet. The total mass of all organic matter, which is formed annually on the Earth's surface, is about 150-200 billion tons. Remember what we said about the productivity of the oceans above? So, 2/3 of this substance is formed on land! Just imagine: gigantic, incredible volumes of the hydrosphere form three times less organic matter than a tiny part of the land, a large part of which are deserts!

More than 90% of the accumulated organic matter in one form or another is used as food for heterotrophic organisms. Only a tiny fraction of solar energy is stored in the form of soil humus (as well as oil and coal, which are being formed even today). On the territory of our country, the increase in primary biological production varies from 20 centners per hectare (near the Arctic Ocean) to more than 200 centners per hectare in the Caucasus. In desert areas, this value does not exceed 20 c/ha.

In principle, on the five warm continents of our world, the intensity of production is practically the same, almost: in South America, vegetation accumulates one and a half times more dry matter, which is due to excellent climatic conditions. There, the productivity of natural and artificial ecosystems is maximum.

What feeds people?

Approximately 1.4 billion hectares are planted on the surface of our planet with cultivated plants that provide us with food. This is about 10% of all ecosystems on the planet. Oddly enough, but only half of the resulting products go directly to human food. Everything else is used as pet food and goes to the needs industrial production(not related to food production). Scientists have been sounding the alarm for a long time: the productivity and biomass of our planet's ecosystems can provide no more than 50% of humanity's needs for protein. Simply put, half of the world's population lives in conditions of chronic protein starvation.

Biocenoses-record holders

As we have already said, equatorial forests are characterized by the highest productivity. Just think about it: more than 500 tons of dry matter can fall on one hectare of such a biocenosis! And this is far from the limit. In Brazil, for example, one hectare of forest produces from 1200 to 1500 tons (!) of organic matter per year! Just think: there are up to two centners of organic matter per square meter! In the tundra on the same area, no more than 12 tons are formed, and in the forests of the middle belt - within 400 tons. Agricultural enterprises in those parts actively use this: the productivity of an artificial ecosystem in the form of a sugarcane field, which can accumulate up to 80 tons of dry matter per hectare, nowhere else can physically produce such yields. However, the Orinoco and Mississippi bays, as well as some areas of Chad, differ little from them. Here, for a year, ecosystems “give out” up to 300 tons of matter per hectare!

Results

Thus, the evaluation of productivity should be carried out precisely on the basis of the primary substance. The fact is that secondary production is no more than 10% of this value, its value fluctuates greatly, and therefore detailed analysis this indicator is simply impossible.

Autotrophic ecosystems can be compared to an industrial enterprise that produces various organic substances. Using solar energy, carbon dioxide and mineral nutrients, ecosystems produce biological products - wood, leaf mass of plants, fruits, animal biomass. The productivity of an ecosystem, measured by the amount of organic matter that is created per unit time per unit area, is called biological productivity. Productivity units: g/m 2 per day, kg/m 2 per year, t/km 2 per year.

On fig. the structure of the biological production of the ecosystem is shown.

Rice. The structure of the biological products of the ecosystem

There are different levels of production at which primary secondary products are created. The organic mass created by producers per unit of time is called primary products, and the increase per unit time of the mass of consumers - secondary products.

Primary production is subdivided, as it were, into two levels - gross and net production. Gross primary production is the total mass of gross organic matter created by a plant per unit time at a given rate of photosynthesis, including respiration costs.

Plants spend on breathing from 40 to 70% of the gross output. Planktonic algae spend the least - about 40% of all energy used. That part of gross output that is not spent "for breathing" is called net primary production: it represents the value of plant growth and it is this product that is consumed by consumers and decomposers.

Secondary production is no longer divided into gross and net, since consumers and decomposers, i.e. all heterotrophs increase their mass due to primary production, i.e. using previously created products.

During the transition of energy from one trophic level to another (from plants to phytophages, from phytophages to first-order predators, from first-order predators to second-order predators), about 90% of energy is lost with excrement and breathing costs. In addition, phytophages eat only about 10% of the plant biomass, the rest replenishes the supply of detritus and then it is destroyed by decomposers. Therefore, secondary biological production is 20-50 times less than primary.

Ecosystems are divided into four classes according to their productivity.

1. Ecosystems of very high biological productivity - over 2 kg/m 2 per year. These include thickets of reeds in the deltas of the Volga, Don and Ural. In terms of productivity, they are close to the ecosystems of tropical forests and coral reefs.

2. Ecosystems of high biological productivity - 1 - 2 kg / m 2 per year. These are linden-oak forests, coastal thickets of cattail or reeds on the lake, crops of corn and perennial grasses with irrigation and fertilization with high doses of mineral fertilizers.

3. Ecosystems of moderate biological productivity - 0.25 - 1 kg / m 2 per year. Many crops, pine and birch forests, hay meadows and steppes, lakes overgrown with aquatic plants, and “sea meadows” of algae in the Sea of ​​Japan have such productivity.

4. Ecosystems of low biological productivity - less than 0.25 kg/m 2 per year. These are the arctic deserts of the islands of the Arctic Ocean, tundra, deserts, semi-deserts of the Caspian Sea, steppe pastures trampled down by cattle with low and sparse herbage, mountain steppes. The same low productivity is found in most of the marine ecosystems.

The average productivity of the Earth's ecosystems does not exceed 0.3 kg / m 2 per year, since the planet is dominated by low-productive ecosystems of deserts and oceans.

The biological productivity of an ecosystem is different from biomass stock. Some organisms in the ecosystem live for many years (trees, large animals), and their biomass passes from year to year as some kind of capital.

On fig. the ratio of biomass stock and biological productivity in some ecosystems is shown.

Rice. Ratio of biomass stock and biological productivity in some ecosystems

The biomass of the forest is high due to perennial parts of trees - trunks, branches, roots. Therefore, the annual increase in biological products - new leaves, young twigs and roots, the next annual tree ring and grass cover - is 30-50 times less than the biomass reserve. In the meadow, the biomass reserve is much less, and it is formed mainly by roots that live in the soil for several years, and plant rhizomes. It is more than biological productivity only 3-5 times. In the fields, biological productivity and biomass stock are almost equal, since the crop of the aboveground parts of plants (and underground, if these are root crops) is harvested, and the crop residues of rye or wheat are plowed into the soil, where they rot by spring. Both in the meadow system and in the field ecosystem, the lifespan of numerous soil invertebrates is measured in weeks and months. Their biological productivity is either equal to the biomass stock or more. Algae and small invertebrates in water bodies live for several days or weeks and therefore give several generations during the summer. At any given moment, the biomass of organisms in a lake or pond is less than their biological production during the growing season.

In some aquatic ecosystems, due to the fact that fish live for several years, and the life of phytoplankton organisms is short, the stock of animal biomass may be higher than the stock of plant biomass. An excess of animal biomass over plant biomass in marine ecosystems (excluding "algal meadows") is the rule.

All living components of the ecosystem - producers, consumers and decomposers - make up a common biomass("live weight") of the community as a whole or its individual parts, certain groups of organisms. Biomass is usually expressed in terms of wet and dry weight, but can also be expressed in energy units - in calories, joules, etc., which makes it possible to reveal the relationship between the amount of incoming energy and, for example, average biomass.

Not all energy is spent on the formation of biomass, but the energy that is used creates primary production and can be spent differently in different ecosystems. If the rate of its removal by consumers lags behind the rate of plant growth, then this leads to a gradual increase in the biomass of producers and an excess of dead organic matter. The latter leads to the peating of swamps, the overgrowth of shallow water bodies, the creation of a large supply of bedding in taiga forests, and so on.

In stable communities, almost all production is spent in food webs, and biomass remains constant.