Biological productivity of ecosystems.
Source: training manual “Island”, lecture 4.
Answer:
Autotrophic ecosystems, using the energy of the Sun, carbon dioxide and minerals, produce various organic substances - wood, leaves, fruits, i.e. living biomass. Ecosystem productivity is measured by the amount of organic matter that is created per unit time per unit area, and is called biological productivity.
The total annual production of dry organic matter on the planet is 150-200 billion tons. 1/3 of this production is formed in the ocean, 2/3 on land. Almost all of the net primary production of the planet serves to support the life of heterotrophs. Unused energy is stored in their bodies, in the organic sediments of water bodies, in the humus of the soil.
Distinguish primary, gross, clean, secondary production of communities.
Biological production is measured by the amount of dry or wet weight of organic matter (plants) produced per unit time per unit area (t / ha per year, g / m 2 per day) or in energy units - the equivalent number of joules.
Plants create primary production, community recycled products(created by heterotrophs) - an increase in the mass of consumers per unit time. . Secondary production is calculated separately for each trophic level, since the mass gain at each of them occurs due to the energy coming from the previous level. Heterotrophs live off the net primary production of the community.
Primary production is divided into gross primary production - the amount of substance created by plants per unit of time at a given photosynthesis rate, that is, the total production of photosynthesis (spent on the processes of vital activity, excretion, growth of the biomass of organic matter), and net primary production- the value of the growth of plants (biomass of organic matter).
When moving from one trophic level to another, 90% of the energy is lost. Therefore, the amount of secondary biological products is 20-50 times less than the primary.
The productivity of the main ecosystems of the planet is shown in table. 2 to 4.
Under biomass they understand the mass of an organism, organisms of a certain group, the whole community as a whole or ecosystem. By biomass is meant all living organic matter that is contained in an ecosystem or its elements, regardless of how long it has formed and accumulated. There are phytomass (mass of living plants), zoomass, microbial mass, dead substance mass. Also distinguish biomass aboveground, underground, water.
table 2
Annual environmental performance
Ecosystems are distinguished by their productivity, which, first of all, depends on their geographic position on the surface of the globe. The most productive sushi biomes are rainforests, and the World Ocean - coral reefs. It is in these ecosystems that organic matter is produced and transported the most in a unit of time. The high potential of these ecosystems is explained by their close proximity to the equator - here the largest solar radiation and constantly high temperature, therefore, biochemical reactions in the cells pass very quickly, and photosynthesis is carried out throughout the year.
Biocenoses may differ in their productivity and within the same biome. Multi-tiered mature ecosystems, which include a large number of species of organisms that occupy a variety of ecological niches, are more productive than single-tiered ones with a poor species composition. However, the most productive and species-rich communities of organisms are on the borders of two biomes (for example, broad-leaved forest and steppe zones), landscapes (forests and fields), and habitats (marine and freshwater). This is due to the fact that such places are very densely populated. Here, there are both species confined to each type of ecosystem, and organisms that inhabit only such border areas. The increase in species diversity and productivity in the border spaces is often called the "edge effect", and such places - ecotones (from Greek oikos - home and tonos - voltage). They have a specific structure and are extremely important for the conservation of species and biological diversity (Fig. 138). Material from the site
Ecotones - not only the edges of forests, but also floodplains of rivers, sea coasts and estuaries - places where fresh river and salty sea water collide. In such desalinated areas live marine, migratory and even freshwater fish. The largest ecotone of Ukraine is the Sea of \u200b\u200bAzov. It is more correct to call this reservoir not the sea, but the huge estuary of the Don. It is no accident that the ancient Greeks called it the Meiotic swamp.
Ecosystems are distinguished by their productivity. The most productive are tropical ecosystems, as well as border communities of organisms in ecotones - transition zones between different ecosystems, landscapes, or habitats.
On this page, material on the topics:
Why ecotones gather the most productive communities
Which ecosystem is more productive
The most productive type of ecosystem
Why is the forest more productive
Which ecosystems are more productive and why
Questions about this material:
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.
1. Efficiency and dynamics of ecosystems. 2. People and ecosystems.
One of the most important properties of organisms, their populations and ecosystems as a whole is the ability to create organic matter, which is called production. Product formation per unit time (hour, day, year) per unit area (square meters, hectare) or volume (in aquatic ecosystems), expressed in units of mass (grams, kilograms, tons), characterizes the productivity of ecosystems.Ecological System Productivity- this is the speed with which producers absorb radiant energy during photosynthesis and chemosynthesis, forming organic matter, which can then be used as food. Distinguish between production levelson which primary and secondary products are created. Organic matter created by producers during photosynthesis or chemosynthesis is called primary products of the ecosystem (community). Quantitatively, it is expressed in the wet or dry mass of plants or in energy units - the equivalent number of joules. Primary production determines the total energy flow through the biotic component of the ecosystem. The theoretical possible rate of creation of primary biological products is determined by the capabilities of the photosynthetic apparatus of plants. Primary production is subdivided as it were into two levels - gross and net production. The rate at which plants accumulate chemical energy is called gross primary productivity(GDP). About 20% of this energy is spent by plants on respiration and photo-respiration. The rate of accumulation of organic matter, minus this flow rate, is called net primary productivity(NWP) is the energy that organisms of the following trophic levels can use. The amount of organic matter accumulated by heterotrophic organisms is called secondary products.Secondary production is calculated separately for each trophic level, since the mass increase at each of them occurs due to the energy coming from the previous one. Along with products distinguish biomassorganism, groups of organisms or ecosystems in general. Under her understand all living matter that is contained in the ecosystem or its elements, regardless of how long it was formed and accumulated.The primary production of the Earth’s biosphere is estimated at 170 billion tons, and the secondary - at 4 billion tons of dry organic matter per year. In climatic zones, natural ecosystems are dominated by those that receive energy only from the Sun. Natural energetically subsidized (i.e., receiving additional energy) ecosystems include estuaries, deltas and floodplains, as well as some swamps. They also include agroecosystems and aquaculture, simultaneously cultivated by man and receiving the energy of the Sun. A special category is industrial-urban ecosystems that operate using only fuel energy. The nutrition of people is mainly provided by crops, which occupy about 10% of the land area. In total, a person consumes about 0.2% of the primary production of the Earth. It is especially difficult to provide the population with secondary products. A person’s diet should include at least 30 g of protein per day. Therefore, increasing the biological productivity of ecosystems and especially secondary products is one of the main challenges facing humanity. The manifold changes occurring in any community are classified into two main types: cyclic and translational. Periodically repeating dynamics is called cyclic changes or fluctuations, and directional dynamics is called translational or ecosystem development.Cyclic changescommunities reflect the daily, seasonal, and perennial periodicity of external conditions and the manifestation of endogenous rhythms of organisms. Long cyclemanifested due to climate fluctuations. Fluctuation(from lat. fluctuatio - fluctuations) - relatively short-term changes, when communities without changing their floristic composition deviate from a certain average state due to seasonal and weather changes in climate, as well as changes in the dynamics of the animal component of the ecosystem or in the ways they are used. Translational changesin the ecosystem ultimately lead to a change in one biocenosis to another, with a different set of dominant species. The successive change of one biocenosis to another is called environmentalsuccession. The successive series of gradually and naturally replacing each other in succession of communities is called succession series. According to F. Clementson (1916), the succession process consists of the following stages: 1. The appearance of a site not occupied by life. 2. Migration to it of various organisms or their primordia. 3. Engraft them in this area. 4. Their competition among themselves and the crowding out of individual species. 5. Transformation by living organisms of the habitat, the gradual stabilization of conditions and relationships. Succession with a change of vegetation can be primary and secondary. Primary successionthe process of development is called the change of ecosystems in previously unpopulated areas that begin with their colonization. Secondary succession- This is the restoration of the ecosystem that once existed in this territory. Secondary successions occur, as a rule, faster and easier than the primary ones, since the soil profile, seeds, rudiments, and part of the former population and former ties are preserved in the disturbed habitat. Succession ends with a stage when all species of the ecosystem, reproducing, maintain a relatively constant abundance and no further change in its composition occurs. This equilibrium state is called - menopauseand the ecosystem menopause. The ability of an ecosystem to self-sustain and self-regulate is called homeostasis. In the competition for survival in the natural environment, man began to build his artificial anthropogenic ecosystems.
Agroecosystemscreated by man to increase the high yield - the net production of autotrophs. Simplification of the natural environment of a person from an environmental perspective is very dangerous. Therefore, it is impossible to turn the entire landscape into an agro-economic one, it is necessary to preserve and multiply its diversity, leaving untouched protected areas that could be a source of species for the restored and succession series of the community.
Literature:1. Korobkin V.I. and others. Ecology. - M., 2003.S. 130-150. 2. Nikolaykin N.I. and others. Ecology. - M., 2004.S. 155-163, 171-180. 3. Askarova M.A. General ecology. - Almaty, 2004.S. 86-94. 4. Stepanovskikh A.S. General ecology. - M., 1999. 404-419.
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.