The concept of the ecosystem by the British ecologist Tansley (AGTansley, 1871-1955) proposed in 1935, he believes that "the basic concept of ecosystem physics using 'system' as a whole and this system includes not only organic complexes, but also the formation of the entire physical environment factor complex. " "Our basic view of the living body, it must be recognized that a fundamental, the organism can not be separated from their environment, but with their environment to form a natural systems." "This system is the nature of the earth's surface the basic unit, They come in various sizes and types. "
With the development of ecology, people continued to deepen understanding of the ecosystem. 1940s, the United States ecologist Lindemann (RLLindeman) lake ecosystems in the study, the subject of "small fish eat shrimp, shrimp eating mud," the proverb inspired proposed food chain concept. He has been "a mountain can not save tigers, inspired proposed ecological pyramid theory, to raise awareness of the ecosystem trophic structure and energy flow characteristics. Today, people's understanding of the concept of ecosystem are: Ecosystem is in a certain range of space and time, as well as between the various organisms and their inorganic environment biomes between energy flow and nutrient cycling through the interaction of a unified whole. ecosystem is a biological and environmental energy conversion between and material cycles of the basic functional units.
To survive and thrive, each creature must draw from the surrounding environment air, water, sunlight, heat and nutrients; biological growth, breeding and activities in the process and constantly released to the surrounding environment and excretion of various substances, death After residues have reverted to the environment. For any kind of creature, the surrounding environment, including other organisms. For example, green plants use microbial activity released from the soil of nitrogen, phosphorus, potassium and other nutrients, herbivores in green plants for food, Youyi carnivores herbivores for food, a variety of plant and animal residues are both insects and other small animals for food, but also a source of nutrition for microorganisms. The results of microbial activity and the release of plant nutrients needed for growth. After a long-term natural evolution of each region between organisms and the environment, biological and bio-between, have formed a relatively stable structure, with the corresponding function, which is commonly ecosystem.
1 The concept of ecosystem
Ecosystems (ecosystem) is a British ecologist Tansley first put up in 1935, and refers to a certain space and abiotic components of biological component material circulation and energy flow through the interaction, interdependence and ecological functional unit consisting of a . It is the integration of biological and non-biological environment as influence each other, interdependent unified whole. Ecosystems, whether natural or artificial, are with the following common features: (1) on the ecology ecosystem is a major structural and functional units, belonging to the highest level of ecological studies. (2) within the ecosystem self-regulation. Its structure is more complex, the number of species, the more self-regulating capacity of the stronger. (3) energy flow and nutrient cycling are two functions of ecosystems. (4) The number of ecosystem trophic level due to the fixed energy producers and energy flow limit value of energy loss process, generally no more than 5 to 6. (5) ecosystem is a dynamic system, to undergo a from simple to complex, from immature to mature developmental processes.
Proposal of the concept of ecosystem ecology research and development has laid a new foundation, greatly promoted the development of ecology. Ecosystem ecology is a contemporary ecological research frontier.
(2) the composition of the ecosystem
There are four major ecosystem components. Ie abiotic environment, producers, consumers and decomposers.
(A) the abiotic environment include: climatic factors, such as light, temperature, humidity, wind, rain, snow, etc.; inorganic substances, such as C, H, O, N, CO2 and various inorganic salts. Organic substances, such as proteins, carbohydrates, lipids, and humus.
(2) producers (producers) mainly refers to the green plants, including blue-green algae and some bacteria, are able to use simple inorganic substances autotrophic organisms in food production. In ecosystems play a leading role.
(3) consumers (consumers) heterotrophic organisms, mainly refers to the other creatures that feed on a variety of animals, including herbivores, carnivores, omnivores and parasitic animals.
(4) decomposers (decomposers) heterotrophic organisms, mainly bacteria and fungi, including certain protozoa and earthworms, termites, vultures and other large saprophagous animals. They break down animal and plant debris, feces and a variety of complex organic compounds, absorb some of the decomposition products of decomposition of organic matter eventually be able to simple inorganic substances, and these inorganic material circulation after being involved in autotrophic organisms reused.
3 ecosystem structure
Ecosystem structure understood from two aspects. One is the morphological structure, such as species, populations, population spatial pattern, the time variation of the population, as well as the vertical and horizontal community structure. Morphology and structure of plant communities consistent, plus soil, atmosphere and abiotic components of the consumer, decomposers morphology. The other is nutrition structure, nutrition structure is based on nutrition as a link to biotic and abiotic closely integrated functional units, constituted by producers, consumers and decomposers as the center of the three functional groups, which occurred between environment close material circulation and energy flow.
4 ecosystem primary production and secondary production
Energy flow in ecosystems began in photosynthesis of green plants. Photosynthesis is the accumulated energy into the ecosystem of the primary energy, which is the primary production process of accumulation. Primary production rate of accumulation of energy is called primary productivity (primary productivity), the manufacture of organic matter is called primary production or primary production (primary production).
In primary production, there is a part of their breathing by plants consumed, the rest was to be seen in the form of organic matter for plant growth and reproduction, we call this part of the production capacity of net primary production (net primary production , NPP), which includes the energy consumed by respiration (R), including all production is called gross primary production (gross primary production, GPP). The relationship between them is GPP = NPP + R. GPP and NPP usually produced per square meter per dry weight of organic matter (g/m2.a) or fixed energy value (J/m2.a) to indicate, at this time they called the total (net) primary productivity, The concept of productivity is the rate, while the production capacity is the amount of concept.
At a given moment ecosystems unit area accumulated organic quality of life called biomass (biomass). Biomass accumulation of net production, biomass is a time past, the ecosystem is the accumulated amount of living organic material. Biomass usually mean dry weight of organisms per square meter (g/m2) or energy value (J/m2) to represent. Biomass and production are two different concepts, the former is the concept of ecosystem structure, while the latter is a functional concept. If the GP-R> O, biomass increase; GP-R <O, biomass reduction; GP = R, then the biomass constant, where GP represents a trophic level of production. Trophic level within a certain period change in biomass (dB / dt) can be calculated by the following formula: dB / dt = GP-RHD, where H represents the feeding by the next trophic level biomass, D is the death biomass loss. Biomass in the ecosystem with a clear vertical distribution phenomenon.
Secondary production is in addition to other organisms outside the producer of the production, namely the use of consumers and decomposers for assimilation of primary production, the performance of animals and other heterotrophic organisms growth, reproduction and nutrient storage. Animals and other heterotrophic organisms by consuming manufacturing plant primary production of organic matter or fixed energy, called secondary production or secondary production (secondary production), or a fixed rate of its production, said secondary (second sex) Productivity (secondary productivity). The secondary production of animals by the next equation: P = C-FU-R, wherein, P is the secondary production capacity, C represents the energy intake from outside animals, FU representative of feces and urine of energy lost, R represents the energy lost during respiration.
5 decomposition ecosystem
Ecosystem decomposition (or called decomposition) (decomposition) refers to the gradual dead organic matter degradation process. Decomposition of the inorganic element is released from the organic matter, to obtain mineralized, inorganic elements and photosynthesis fixing process is just the opposite. From the energy point of view, the former is put to, which is the energy storage. From the material point of view, they are the material cycle regulator, the decomposition process is actually very complex, which includes physical crushing, shredding, chemical and biological degradation, leaching, animal feed, the wind shifted and sometimes human interference and almost simultaneously the various roles. The simplification will be seen as fragmentation, alienation and leaching three integrated process. Since the physical and biological effects, the dead litter decomposition of residual particulate debris known as fragmentation; organic matter decomposition under the action of the enzyme from the polymer into a monomer, for example, cellulose into glucose, and then to become mineral composition, called alienation; leaching is leached out by water soluble substances, is a purely physical process. Decomposition process, these three processes are cross, mutual influence.
The rate and characteristics of the decomposition process, depending on the quality of the resource, decomposers types and environmental conditions, three physicochemical aspects. Resource quality including physical and chemical properties, physical properties, including surface properties and mechanical and chemical properties, such as C: N ratio, lignin, cellulose content, etc., are all in the decomposition process plays an important role. Decomposers include bacteria, fungi and soil fauna (aquatic ecosystems for small aquatic animals). Physical environment mainly refers to temperature, humidity, etc.
6 Energy Flow in Ecosystems
Energy is an ecosystem basis, all life exists energy flow and transformation. No flow of energy, there is no life and ecosystems. Traffic flow is one of the important functions of ecosystems, energy flow and conversion is subject to the first and second laws of thermodynamics, because the laws of thermodynamics is the study of energy transfer and energy form into the laws of science.
Energy flow in ecosystems, food chains and populations were analyzed on three levels. Ecosystem-level energy flow analysis is based on the same trophic level to estimate the total amount of each species, that is the property of each population belongs to a particular trophic levels (based on their main diet), and then precisely determined for each trophic level of energy input and output values. This analysis is more common in aquatic ecosystems, its boundaries clear, closed strong, stable internal environment. Levels of the food chain on the energy flow analysis is to each population as the energy moves from the producer to the consumer during the climax of a link, when the energy along a food chain in several species flow, measured on every aspect of the food chain of the energy values, we can provide a range of ecosystem energy flow at specific points detailed and accurate information. Experimental population levels of energy flow analysis, it is nothing to do in the laboratory to control various variables to study the process of energy flow and energy storage energy loss affecting a variety of important environmental factors.
Here we also introduce the food chain, food web, trophic levels, ecological pyramids concepts. Fixed energy plants through a series of feeding and the feeding relationships in an ecosystem transfer, transfer relationship between this creature called the food chain (food chains). General food chain is composed of four to five aspects, such as grass → insects → Birds → Snake → Hawk. But between organisms in ecosystems feeding and feeding relationships are complex, this link is like an invisible net of all organisms are included, so that between them have a certain relationship, directly or indirectly, , this is the food web (food web). In general, the more complex food webs, ecosystem's ability to resist external interference, the stronger, and vice versa. In any ecosystem, there are two main food chain, namely predator food chain (grazing food chain) and detritus food chain (detrital food chain), the former is a living plant and animal food chain as a starting point, the latter were dead biological or detritus as a starting point. In most terrestrial and shallow water ecosystems, detritus food chain is the most important, such as a poplar plant biomass in addition to 6 percent is animal feeding, and the remaining 94% are dead after being broken by those who litter decomposition. A trophic level (trophic levels) is a link in the food chain on the sum of all living species in the ecosystem energy flow analysis, in order to facilitate, often to every living species placed in a certain trophic levels . Producers are the first trophic level, herbivores case of a second trophic level, and the third trophic level includes all herbivores eating carnivores, usually a number of ecosystem trophic level of 3 to 5. Ecological pyramid (ecological pyramids) refers to various quantitative relationship between trophic level, this relationship between the number of units of biomass can be used, the number of energy units and individual units, respectively, constitute the biomass pyramid, energy pyramid and number pyramid.
7 ecosystem nutrient cycling
Ecosystem nutrient cycling (circulation of materials), also known as biogeochemical cycles (biogeochemical cycle), refers to a variety of chemical elements on Earth, from the surrounding environment to the organism, and then returned to the surrounding environment from the organism periodically cycle. Energy flow and nutrient cycling are two basic processes of ecosystems, which allow ecosystems between each trophic level between the organization and the various components of a complete functional unit. But the energy flow and nutrient cycling are different in nature, the energy flows through ecosystems final form of heat dissipation, energy flow in one direction, so the ecosystem must constantly get energy from the outside; and material flows are cyclic, and each substances may be able to return to the environment in the form of plant use. While the two are closely related and indivisible.
Biogeochemical cycles libraries and circulation rate can be described in two concepts. Libraries (pools) is present in some of biotic and abiotic ecosystem components a certain amount of certain chemicals posed. These libraries by means of related substances in the transfer between libraries and interrelated, substances in the ecosystem unit area (or volume) and the amount of movement per unit time is called the flow rate (flux rates). A library circulation rate (units / day), and the library in which the ratio of the total nutrient turnover (turnover rates), the reciprocal of turnover turnaround time (turnover times).
Biogeochemical cycle can be divided into three types, namely water cycle (water cycles), the gas circulating (gaseous cycles) and sedimentary cycles (sedimentary cycles). The water cycle is the main route from the Earth's surface into the atmosphere through evaporation, while continuously from the atmosphere through precipitation and return to the Earth's surface, H and O, mainly through the water cycle in biogeochemical cycles. In the gas circulating in the main repository of substances in the atmosphere and oceans, the atmosphere and the ocean circulation and its closely related, with a significant global cycling performance the most perfect. The substance is a gas circulating O2, CO2, N, Cl, Br, F and so on. Substances involved sedimentary cycle, mainly through the weathering of rocks and sediments can be decomposed into the ecosystem use of the material, which is the main repository of soil, sediment and rock cycle gas circulating globally as obvious, cycling performance generally far from perfect. Deposition cycles are substances P, K, Na, Ca, Ng, Fe, Mn, I, Cu, Si, Zn, Mo, etc., where P is more typical sedimentary circulating element. Gas circulating and sedimentary cycles are driven by energy flow, and are dependent on the water cycle.
Biogeochemical cycles is an open cycle, the time span bigger. Ecological systems, within the system there is a soil, air and biological elements between the periodic cycle, called biological cycle (biocycles). Nutrient cycling is also known as nutrient cycling (nutrient cycling), which generally includes the following processes: absorption (absorption), ie nutrients from the soil and transferred to the vegetation; retention (retention), refers to the flora and fauna in nutrient retention in ; restitution (return), ie, return nutrients to the surface of the plant community driven process, mainly in the dead residue litter, precipitation leaching, root exudates and other forms completed; released (release), refers to the release of nutrients through decomposition process, while accumulation on the surface a (accumulation) process; store (reserve), i.e. stored nutrients in the soil, the soil is nutrient pool, in addition to N are from outside of soil nutrients. Among them, the absorption rate = retention volume + Restitution.
Knowledge of the biosphere
The concept of the biosphere, the following points are recognized: ① earth biodistribution area all belong to the biosphere; ② biosphere is composed of biological and non-biological environment of a certain structure and function of a unified whole, is highly complex and orderly system, rather than loose unordered set; ③ mobility of the species continuity with inorganic environment changing its structure and function, and tend to be relatively stable state constantly. Earth's largest ecosystem is the biosphere, the largest ecosystem on land is forest ecosystems, the country's largest ecosystem grassland ecosystem.
The role of forest ecosystems forest coverage rate is a measure of a country and an important indicator of ecological environment. If a regional forest coverage rate reached 30%, and more evenly distributed, will be able to effectively regulate the climate, reducing the occurrence of natural disasters. The specific role of forests in the following areas:
① regulating biosphere relative balance of O2 and CO2 in the growing season broadleaf forest one day per hectare can absorb 1000 kg of CO2, emit 730 kg of O2. The average person has 10 m2 of forest, which can meet the needs of multi-oxygen environment.
② air purification plant foliage can absorb soot, dust and other pollutants and toxic gases such as SO2, such as oleander, sycamore, cedar, acacia trees can absorb SO2, pine needles secretions can kill Mycobacterium tuberculosis and diphtheria bacilli and so on.
③ eliminate noise 30 m wide belt can absorb and reduce noise 6-8 decibels.
④ water conservation, soil and water, wind and sand.
⑤ regulating climate, increasing precipitation, beautify the environment.
Ancient forest coverage rate up to 60% of China's forest coverage is now only 16.55 percent, plantation area ranks first in the world.
The principle of agro-ecosystems
The first is the ecosystem energy and material use of multi-stage recycling. Food chain ecosystem energy flow and nutrient cycling of the main channel, it is both an energy conversion chain, transport chain is a substance, or a value-added chain. Followed by agro-ecosystems follow interdependence between various organisms, the principle of mutual restraint. In agro-ecosystems, people use the relationship between the biological populations. Regulation of biological populations artificially increase the natural enemies of pest populations can reduce pests. Such as stocking Trichogramma medinalis prevent pesticide contamination.
The design and layout of ecological agriculture mainly from the plane, vertical, time, food chains and other aspects. Graphic Design juice is in a certain area. Determine the type and variety of various crops the proportion of agricultural industrialization and distribution areas, namely agriculture or agricultural zoning layout. Vertical design is the use of ecological principles. The populations of the various combinations of composite production system in a reasonable, to the fullest and most rational use of environmental resources. Vertical structure includes two parts above and below ground, above ground, including different crops at different levels space stems, leaves the rational allocation in order to maximize the use of light, heat, water, gas and other natural resources. Underground part of the complex roots of crops in different layers of the distribution, in order to make better use of soil water and mineral elements. The design is based on the time range of agricultural resources, time rhythm, the design of effective use of agricultural resources, production patterns. Populations of various crops including chimeric design, such as intercropping, multiple cropping, transplanting seedlings, changing crop growth regulation designs. The design is based on the food chain, ecological principles and the actual situation of local agro-ecosystems scientifically designed structure within the food chain. To achieve multi-level material and energy utilization, and improve overall economic efficiency. The focus is the introduction of the food chain in the original or add new links. For example, the introduction of natural enemies to control animals, the number of insect pests. Adding new production processes can not be directly used to bring people into organic matter can be directly utilized agricultural and sideline products.
Reducing a biological ecosystem changes caused by other species.
In the food chain in the first trophic levels decrease as a result of changes in other species: in a food chain, if in the first trophic levels decrease, then the other organisms in the food chain are reduced. This is because the first trophic level is a variety of other biological survival of direct or indirect source of food, the reduction of the trophic levels will cause a chain reaction, resulting in the following trophic levels were reduced.
"Enemies" Party reduced, and the effects of changes in the number of eaters: If a food chain in the "predators" status to reduce the number of organisms, the number of eaters were thus rapidly increased, but this increase is not unlimited. But with the increasing number of population density increased, intraspecific struggle is bound to increase, coupled with no natural enemies of the "pressure" prey own qualities (such as running speed, alertness, sensitivity, etc.) must be reduced , resulting in the spread of epidemics, old and sick persons increases, eventually leading to the density decreases, until relatively stable, that predators reduced, resulting in the food side first increased and then decreased, and finally stabilized.
If you are in the "middle" trophic levels decrease, changes in another organism should be determined depending on the specific food chain. Study, from a high trophic level according to the direction of lower trophic levels and order of consideration.
Answer :2007 -10-29 15:53
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