Biological productivity - the total amount of organic matter produced per unit time per unit area.
The total mass of individuals of one species, group of species, or community as a whole, per unit surface or habitat volume is called biomass. It is expressed in the mass of raw or dry matter, as well as carbon or nitrogen. It is expressed in g / cm 2, kg / ha, g / m 3, in raw or dry form, or in units of energy - in calories, joules, etc. . The biomass of plants is called phytomass, animals - zoomass. The biomass of the individual components is used to judge the quantitative ratios of the masses of organisms.
The increase in the biomass of organisms of a species or the entire community for a certain period is called production.
Distinguish between primary and secondary products of the community.
Primary production - biomass created per unit time of producers. It is divided into gross and net. Gross primary production (general assimilation) is the total biomass created by plants during photosynthesis. Part of it is spent on maintaining the vital activity of plants - expenditure on respiration (40-70%). Net primary production (pure assimilation) is the rate of accumulation of the created organic matter in excess of that spent on respiration. It is later used by consumers and reducers, or accumulates in the ecosystem.
Secondary products - biomass created per unit of time by consumers. It is different for each subsequent trophic level.
Theoretically, the rate of creation of primary biological products is determined by the capabilities of the photosynthetic apparatus of plants. It is known that every minute 2 calories of solar energy (solar constant or constant) are received per 1 cm 2 of the earth's atmosphere. Plants use only 21-46% of the solar energy received by the earth's surface. The most admissible in nature efficiency photosynthesis of 10-12% of the energy of PAR. On the whole, on the globe, the assimilation of solar energy by plants does not exceed 0.1% due to the limitation of the photosynthetic activity of plants by various factors (lack of heat, moisture, adverse soil properties, etc.)
For most types of vegetation cover, efficiency absorbed PAR is on average 1-2%. Desert shrubs have an efficiency 0.03%; grassy alpine plants - 0.15-0.75%. Highest Efficiency in forest ecosystems - 2-4%. Average efficiency for the territory of Russia - 0.8%, in the European part it is 1.0-1.2%, in the eastern regions - 0.4-0.8%.
The average value of primary production in the world is 3 t / ha. The maximum amounts are concentrated in the evergreen tropical rain forests (more than 500 t / ha), the lowest desert (7 t / ha) and the tundra (6 t / ha). Marine plants photosynthesize annually up to 3.0 10 10 tons of organic substances, and terrestrial plants - 5.3 10 10 tons. In general, up to 8.3 10 10 tons of organic substances are created on the planet every year by photosynthesis. Of the 5.3 10 10 tons produced on land, 2.84 10 10 tons are forests, the rest is synthesized by grassy and cultivated vegetation.
If in the ecosystem, the growth rate of plants (the formation of primary production) is higher than the rates of processing by its consumers and reducers, then this leads to an increase in biomass of producers. If at the same time there is insufficient utilization of the litter products in the decomposition chains, then the accumulation of dead organic matter occurs. This leads to peat bogs, overgrowing shallow ponds, the formation of thick forest litter, etc. In stable ecosystems, biomass remains constant, since almost all production is consumed in food chains.
By productivity, communities are divided into 4 classes:
1. Communities higherproductivity 2-3 kg / m 2 / year. These are tropical forests, rice and sugar cane crops, reed beds in the deltas of the Volga, Don;
2. Communities high productivity 1-2 kg / m 2 / year. This class includes deciduous forests of the temperate zone, meadows when applying fertilizers, crops of corn;
3. Communities moderate productivity, 0, 25-1 kg / m 2 year. This class includes crops of the bulk of cultivated agricultural crops, pine and birch forests, hay meadows, steppes;
4. Communities low productivity, below 0.25 kg / m 2 / year - deserts, semi-deserts, tundra.
Table 4 - Biomass of different types of ecosystems (N.F. Reimers, 1990)
Table 5 - Primary biological production of the main ecosystems of the globe
(N.F. Reimers, 1990)
The nutrition of people for the most part provides communities with moderate productivity, i.e. crop communities. The annual growth of cultivated plants is approximately 16% of all land productivity. About 1/4, which is about 9 billion tons of agricultural products, enter the anthropogenic channel formed by people and animals. production. About 90% of the energy contained in these products is provided by crop products. Of the known 80 thousand edible plants, a little more than 80 species are cultivated on the globe (the cultural flora of the CIS is more than 50 species). The most widespread are: rice, wheat, corn, potatoes, barley, sweet potato, cassava, soy, oats, sorghum, millet, sugarcane, sugar beets, rye, peanuts. Rice and wheat account for more than 40%. Cereals provide almost 50% of the protein consumed by humans.
Ecosystem productivity - This is the accumulation by the ecosystem of organic matter in the process of its life. Ecosystem productivity is measured by the amount of organic matter created per unit time per unit area.
There are different levels of production at which primary and secondary products are created. Organic mass created by producers per unit time is called primary products, and the gain per unit time mass of consumers - secondary products.
Primary production is divided into two levels - gross and net production. Gross primary production is the total mass of gross organic matter produced by a plant per unit of time at a given rate of photosynthesis, including respiration.
Plants spend from breathing from 40 to 70% of gross production. Planktonic algae spend it the least - about 40% of all energy used. That part of the gross output that has not been used up “by breath” is called net primary production; it represents the value of the growth of plants, and it is precisely this production that is consumed by consumers and reducers.
Secondary products are no longer divided into gross and net, as consumers and reducers, i.e. all heterotrophs increase their mass due to primary production, i.e. use previously created products.
Secondary production is calculated separately for each trophic level, since it is formed due to the energy coming from the previous level.
All living components of the ecosystem - producers, consumers and reducers - make up total biomass (live weight) community as a whole or its individual parts, of various 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 allows us to identify the relationship between the amount of incoming energy and, for example, the average biomass.
In terms of biological productivity, ecosystems are divided into 4 classes:
- ecosystems of very high productivity -\u003e 2 kg / m 2per year (rainforests, coral reefs);
- ecosystems of high productivity - 1-2 kg / m 2 per year (linden-oak forests, coastal thickets of cattail or reed on lakes, crops of corn and perennial grasses under irrigation and high doses of fertilizers);
- ecosystems of moderate productivity - 0.25-1 kg / m 2per year (pine and birch forests, hay meadows and steppes overgrown with water plants of the lake);
- low productivity ecosystems -< 0,25 кг/м 2 в год (пустыни, тундра, горные степи, большая часть морских экосистем). Средняя биологическая продуктивность экосистем на планете равна 0,3 кг/м 2 в год.
35. Productivity of ecological systems. The most productive ecosystems of the globe, their environmental problems.
Biological production is the amount of biological substance that is created per unit time per unit area (g / m², kg / m²).
Biological products:
Primary (gross); Secondary (net).
Gross production is that production that plants create in the process of photosynthesis.
Net production is that part of the energy that remains after the cost of breathing.
The average productivity of the earth’s ecosystems does not exceed 0.3 kg / m². When energy is transferred from one level to another, approximately 90% of energy is lost, therefore, secondary production is 20-50 times less than primary
Ecosystem productivity, measured by the amount of organic matter that is created per unit time per unit area, is called biological productivity. Units of productivity: g / m² per day, kg / m² per year, t / km ² per year.
Distinguish between primary biological products that producers produce and secondary biological products that consumers and reducers create.
Primary production is divided into: gross - this is the total amount of organic matter created, and clean - this is what remains after consumption for respiration and root secretions.
According to productivity, ecosystems are divided into four classes:
1. Ecosystems of very high biological productivity - over 2 kg / m² per year. These include reed beds in the deltas of the Volga, Don and Urals.
2. Ecosystems of high productivity - 1-2 kg / m² per year. These are linden-oak forests, thickets of cattail or reed on the lake, corn crops.
3. Ecosystems of average biological productivity - 0.25-1 kg / m² per year. These include pine, birch forests, hay meadows, steppes.
4. Ecosystems of low biological productivity - less than 0.25 kg / m² per year.
These are arctic deserts, tundra, most of marine ecosystems.
The average productivity of the earth’s ecosystems is 0.3 kg / m² per year, that is, medium and low-productivity ecosystems prevail on Earth.
When moving from one trophic level to another, 90% of energy is lost.
An example of increased productivity at the junctions of ecosystems is the transitional ecosystems between forest and field (the “edge effect”), and in aquatic environments, ecosystems that arise in river estuaries (places where they flow into the seas, oceans, and lakes, etc.).
These same patterns largely determine the above-mentioned local thickening of large masses of living matter (the most highly productive ecosystems).
Usually the following thickenings of life are distinguished in the ocean:
1. Coastal. They are located at the contact of the water and ground-air environment. Especially highly productive ecosystems of estuaries. The extent of these thickenings is greater, the greater the removal by rivers of organic and mineral substances from land.
2. Coral reefs. The high productivity of these ecosystems is primarily associated with favorable temperature conditions, the filtration type of nutrition of many organisms, the species richness of communities, symbiotic bonds and other factors.
3. Sargasso condensation. They are created by large masses of floating algae, most often Sargassian (in the Sargasso Sea) and phyllophore (in the Black Sea).
4. Upwelling. These condensations are confined to areas of the ocean where there is an upward movement of water masses from the bottom to the surface (upwelling). They carry many bottom organic and mineral deposits and, as a result of active mixing, are well provided with oxygen. These highly productive ecosystems are one of the main fishing areas for fish and other seafood.
5. Rift deep-sea (abyssal) thickening. These ecosystems were discovered only in the 70s of this century. They are unique in nature: they exist at great depths (2-3 thousand meters). The primary production in them is formed only as a result of chemosynthesis due to the release of energy from sulfur compounds coming from bottom faults (rifts). High productivity here is due primarily to favorable temperature conditions, since faults are simultaneously foci of exit from the bowels of heated (thermal) waters. These are the only ecosystems that do not use solar energy. They live off the energy of the bowels of the earth.
On land, the most highly productive ecosystems (thickening of living matter) include: 1) ecosystems of the shores of the seas and oceans in areas well provided with heat; 2) floodplain ecosystems periodically flooded with river waters that deposit sludge, and with it organic and nutrient substances, 3) small inland water ecosystems rich in nutrients, and 4) tropical forest ecosystems. The productivity of other ecosystems is seen from Table 3. We have already noted above that people should strive to preserve highly productive ecosystems - this is the most powerful framework of the biosphere. Its destruction is associated with the most significant negative consequences for the entire biosphere.
As for secondary (animal) production, it is noticeably higher in the ocean than in terrestrial ecosystems. This is due to the fact that on land only about 10% of primary production is included in the consumer link (herbivore) on average, and up to 50% in the ocean. Therefore, despite the lower primary productivity of the ocean than land, these ecosystems are approximately equal in mass of secondary production.
In terrestrial ecosystems, the main products (up to 50%) and especially biomass (about 90%) are forest ecosystems. At the same time, the bulk of these products goes directly to the link of destructors and reducers. Such ecosystems are characterized by a predominance of detrital (due to dead organic matter) food chains. In grassy ecosystems (meadows, steppes, prairies, savannahs), as well as in the ocean, a significant part of primary production is alienated in vivo by phytophages (herbivores). Such chains are called pasture or grazing chains.
Ecosystem productivity is closely related to the flow of energy passing through an ecosystem. In each ecosystem, part of the incoming energy that enters the trophic network is accumulated in the form of organic compounds. The 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 the wet 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. 12.33).
Theoretically, the possible rate of creation of primary biological products is determined by the capabilities of the photosynthetic apparatus of plants. And as you know, only part of the energy of light received by the green surface can be used by plants. Of the short-wave radiation of the Sun, only 44% belong to photosynthetically active radiation (PAR) - wavelength light suitable for photosynthesis.
The rate of accumulation of organic matter minus this flow rate is called net primary productivity (NWP). This is the energy that organisms of the following trophic levels can use. The amount of organic matter accumulated by heterotrophic organisms is called secondary production. Secondary production is calculated separately for each trophic level, since the mass gain on each of them occurs due to the energy coming from the previous one. Heterotrophs, including in trophic chains, ultimately live off the net primary production of the community. The completeness of its consumption in different ecosystems is different. A steady increase in the total biomass of producers is noted if the rate of primary product withdrawal in food chains is behind the growth rate of plants.
The global distribution of primary biological products is very uneven. Net production varies from 3,000 g / m2 / year to zero in extra-arid deserts lacking plants or in Antarctica with its eternal ice on the land surface, and biomass stocks, respectively, from 60 kg / m2 to zero. R. Whittaker (1980) divides all communities into four classes by productivity.
1. Communities of the highest productivity, 3000-2000 g / m2 / year. These include rainforests, rice and sugar cane crops. The biomass stock in this productivity class is very different and exceeds 50 kg / m2 in forest communities and is equal to the productivity of annual crops.
2. Communities of high productivity, 2000-1000 g / m2 / year. This class includes deciduous forests of temperate strip, meadows when applying fertilizers, crops of corn. The maximum biomass approaches the biomass of the first class. The minimum biomass is accordingly equal to the net biological production of annual crops.
3. Communities of moderate productivity, 1000-250 g / m2 / year. This class includes the bulk of cultivated crops, shrubs, steppes. The biomass of the steppes varies between 0.2-5 kg \u200b\u200b/ m2.
4. Communities of low productivity, below 250 g / m ^ year - deserts, semi-deserts (in Russian literature they are often called desert steppes), tundra.
The total annual productivity of dry organic matter on Earth is 150-200 billion tons. Two-thirds of it is formed on land, a third - in the ocean.
Almost all of the pure primary production of the Earth serves to support the life of all heterotrophic organisms. Energy underutilized by consumers is stored in their bodies, soil humus and organic sediments of water bodies. The nutrition of people is mainly provided by crops, which occupy about 10% of the land area. The annual growth of cultivated plants is approximately 16 \\% of all land productivity, most of which is in forests.
Half of the crop goes directly to human nutrition, the rest goes to pet food, is used in industry and is lost in waste. In total, a person consumes about 0.2 \\% of the primary production of the Earth. The resources available on Earth, including livestock products and the results of fishing on land and in the ocean, can provide annually only 50% of the needs of the modern population of the Earth.
Therefore, increasing the biological productivity of ecosystems and especially secondary products is one of the main challenges facing humanity.
Changes in ecosystems - 2 types:
1. Cyclic - reflect the daily, seasonal, multi-year periodicity (change of season, day, etc.);
2. Translational - lead to the change of one biocenosis to another, dominant. Most often, these changes are negative (example: gradual pollution of water bodies as a result of land reclamation, which leads to soil changes - the water body dries up and the biocenosis changes).
The successive change of one biocenosis to another is called ecological succession - an incomplete ecological cycle in the biocenosis.
Ecosystem productivity is closely related to the flow of energy passing through it. Organic matter created by producers in the process of photosynthesis is called the primary production of ecosystems. It is expressed in calories.
Calorie is the mass of organic matter created by producers per unit time per unit area. The more primary production, the more productive the ecosystem.
In prehistoric times, man was part of the biosphere. His interaction took place through her. Gradually, a person was distinguished from the natural environment and the formation of a special system - society.This system is characterized by the presence of social formations, the formation of society, public relations, social regulation and economic activity.
Currently, a person occupies a dual position.
On the one hand, man is a biological object and participates in the circulation of substances; on the other hand, a person forms a social system in which there are cultural, everyday, technical and other a. That is, Vernadsky's theory is included in human life as it develops.
It lies in the fact that, as humanity develops, the era of the human mind should come at a certain time, that is, a person, guided by knowledge, must transform the biosphere from a reasonable point of view. According to Vernadsky, man is one of the species of the animal kingdom with a complex social organization and labor activity. Man cannot exist in natural conditions, as it was before, therefore he interacts with the environment and acts on it.
Therefore, a person depends on many facts: for example, the life of a person is affected by cold, heat, drought, dry wind; human heredity is affected by migration, mutations, natural selection. Human population growth is limited by natural resources, as well as socio-economic and genetic processes.
The main task of mankind is to accept principle of environmental imperative,which means that human survival is possible only if life on Earth is preserved.
A person’s life is closely connected with his health. Health - This is not only the absence of disease, but a state of complete physical, psychological and social well-being. Health depends on the stability of the energy potential: the greater the power and capacity of the realized energy potential, as well as the efficiency of its expenditure, the higher the level of health.
The human environment consists of two systems: natural and technogenic.
It for a person is a complex of conditions that affect the life of a person. The human environment is the atmosphere, hydrosphere, lithosphere. Technogenic environment - buildings, structures, factories, factories, cities, transport, building systems, etc.
For the normal functioning of the human body, the satisfaction of needs, extracted from the environment, is necessary. All human needs are satisfied by natural resources.
Natural resources -objects and phenomena that a person uses to create wealth, providing not only the maintenance of his existence, but also a gradual improvement in the quality of life. Natural objects and phenomena include bodies and phenomena used by man as resources.
All natural resources are divided by source of origin into:
1. Biological - all living environment-forming components of the biosphere (producers, reducers, cosumets).
2. Mineral - all usable natural components of the lithosphere, which are used in the economy as mineral raw materials or an energy source.
3. Energy - the aggregate energy of the sun and space (atomic energy, etc.).
According to their use, natural resources are divided into:
1. Land fund - all land within the country and the world (total 13.4 billion hectares). Z. f. divided into categories:
A) agricultural value
B) lands of settlements,
C) industrial land,
D) land transport,
D) mountain lands.
2. Forest fund - part of the land fund on which the forest grows or may grow.
3. Water resources - the amount of groundwater and surface water.
4. Minerals - a natural accumulation of minerals in the earth's crust.
Natural resources are divided by exhaustibility:
1. Inexhaustible - solar energy (and the natural forces caused by it),
2. Exhaustible.
The main factor limiting the use of natural resources by humans is their limited and exhaustible nature.
As you already know, substances in the ecosystem are used repeatedly, turning according to the principle of the cycle. Moreover, living organisms participate in the movement of substances, so the circulation of substances is biogenic. It begins with the entry of chemical elements from the soil (water and mineral salts) and the atmosphere (carbon dioxide) into living organisms - producers. Producers synthesize organic substances, some of which are passed on to the consumers along the food chain, and some remain unused. A certain amount of organic matter of producers and consumers is returned to the soil with cadaveric material, excrement (detritus). As a result of the activity of reducers, they turn into mineral substances, the atoms of which are again involved in the cycle by producers. But the cycle of substances cannot be completely closed. The atoms of some chemical elements can be removed from the cycle for a long time, accumulating in the lithosphere as a part of limestone (chalk), coal, natural gas, oil, peat, ores of various metals.
The transformation of energy in an ecosystem is somewhat different than the conversion of substances. The flow of solar energy entering the ecosystem, as it were, is divided into two channels - pasture and detrital. In each of them, energy is spent on maintaining the vital activity of organisms. The ratio of the amount of energy passing through pasture and detrital chains varies in different types of ecosystems. The loss of energy in food chains can only be made up by the addition of new portions of solar energy or finished organic matter (feed energy). Therefore, in the ecosystem there cannot be a cycle of energy similar to a cycle of substances. The ecosystem operates only due to the directed flow of energy.
Thanks to the repeated use of matter and the constant influx of energy, ecosystems are able to maintain a stable existence for a long time. At the same time, producers, consumers and reducers living in them ensure the renewal of their biomass, despite the fact that the supply of substances in the biosphere is limited and not replenished. The rate of renewal of the biomass of ecosystem organisms is called biological productivity. It is expressed by the number of products formed.
Ecosystem production - the amount of biomass generated in the ecosystem per unit area or per unit volume of the biotope per unit time.
Ecosystems vary greatly in the number of products produced. It decreases in the following sequence: tropical forest - subtropical forest - forest in the temperate zone - steppe - ocean - desert.
The resulting products can be consumed in different ways in different ecosystems. If the rate of its consumption lags behind the rate of formation, then this leads to an increase ecosystem biomass and accumulation of excess detritus. As a result, peat formation in swamps, overgrowing of shallow reservoirs, litter stock in taiga forests, etc. will be observed. In stable ecosystems, almost all of the resulting production is spent in food networks. As a result, the ecosystem biomass remains almost constant.
Ecosystem biomass is the total amount of organic matter of all living organisms accumulated in a given ecosystem over the previous period of its existence.
Ecosystem biomass is expressed in units of wet weight or dry organic matter mass per unit area: in g / m 2, kg / m 2, kg / ha, t / km 2 (terrestrial ecosystems) or per unit volume (aquatic ecosystems).
The biomass of an ecosystem and its biological productivity can vary greatly. For example, in a dense forest, the total biomass of organisms is very large compared to its annual growth - production. Whereas in the pond, the small accumulated biomass of phytoplankton has a high rate of renewal — production of products due to rapid reproduction.
Primary and secondary products
Depending on what substances and energy are used to restore biomass, ecosystems distinguish between primary and secondary productivity. Accordingly, the resulting product is called primary and secondary.
Primary production - biomass created by autotrophic organisms (producers) from minerals in the process of photo- or chemosynthesis. The main amount of organic substances arising in this way is created by green plants. The conversion efficiency of solar energy absorbed by them into the energy of chemical bonds of organic substances is on average 1%. This pattern is called rules 1%. Primary production is a very important characteristic of an ecosystem. It is the energy accumulated in it that allows all heterotrophic organisms (consumers and reducers) to exist and create their products.
Secondary products - biomass created by heterotrophic organisms (consumers and reducers) from organic matter after its partial splitting.
Both primary and secondary production at trophic levels in pasture chains can be used for different purposes. All primary production created by producers as a result of photosynthesis is called gross primary product (Runway). It is the only source of energy for consumers. That part of the products of the previous trophic level, which is consumed by organisms of the subsequent trophic level, is conventionally called feed (TO). Part of the feed at each trophic level is spent by organisms on the maintenance of vital processes - breathing expenses (TD). And the second part after partial splitting is used to form the biomass of consumers - secondary products (WT). The products of producers, which can be eaten by consumers of the first order, are called net primary products (NWP).
However, not all products formed at the trophic level move to the next level as feed. Part of it, as a rule, remains at the trophic level as a reserve - unused products (NP). The totality of unused products of all trophic levels of the ecosystem is the net production of the community.
Community net products (NPV) is a part of ecosystem production that can be used within the ecosystem itself for its development. It can also be withdrawn by humans without harming the ecosystem. In young ecosystems, where the number of consumers is still small, the stock of net products of the community is large. Such ecosystems can be involved in economic turnover. As the species composition of the ecosystem becomes more complex, the amount of net production of the community gradually decreases. At the final stage of ecosystem development, it approaches zero. Intervention in such equilibrium ecosystems is fraught with disruption of food bonds between organisms and can lead to the destruction of ecosystems.
When distributing primary and secondary products at trophic levels of the ecosystem, balance sheet equality. This means that at each trophic level, the sum of all types of products is equal to the amount of products received from the previous level as feed. When solving the problems of balance equality, the following patterns of distribution of types of products in the ecosystem should be taken into account:
- gross primary production (WFP) \u003d respiratory expenditure (TD I) + net primary production (NWP);
- net primary production (NWP) \u003d unused products (NP I) + feed (K II);
- feed (K II) \u003d expenditure on respiration (TD II) + secondary production (VP II);
- secondary products (WTP II) \u003d unused products (NP II) + feed (K III), etc.
- community net products (NPV) \u003d unused products (NP I) + unused products (NP II) + ... + unused products (NP n).
The Roman numeral in the subscript indicates the trophic level number in the food chain.
In the ecosystem there is a continuous cycle of matter and a directed flow of energy. Due to this, the formation of biomass of organisms. The rate of renewal of biomass is called biological productivity. It is expressed by the amount of production - biomass generated per unit area or unit volume per unit time. Distinguish between primary and secondary products. All unused products are called community products.