Swamp
A swamp is a wetland, forested. Many swamps occur along large rivers where they are critically dependent upon natural water level fluctuations. Other swamps occur on the shores of large lakes; some swamps have hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodic inundation or soil saturation. The two main types of swamp swamp forests and "transitional" or shrub swamps. In the boreal regions of Canada, the word swamp is colloquially used for what is more termed a bog, fen, or muskeg; the water of a swamp may be brackish water or seawater. Some of the world's largest swamps are found along major rivers such as the Amazon, the Mississippi, the Congo. A marsh is a wetland composed of grasses and reeds found near the fringes of lakes and streams, serving as a transitional area between land and aquatic ecosystems. A swamp is a wetland composed of shrubs found along large rivers and lake shores. Swamps are characterized by slow-moving to stagnant waters.
Many adjoin rivers or lakes. Swamps are features of areas with low topographic relief. Humans have drained swamps to provide additional land for agriculture and to reduce the threat of diseases borne by swamp insects and similar animals. Many swamps have undergone intensive logging, requiring the construction of drainage ditches and canals; these ditches and canals contributed to drainage and, along the coast, allowed salt water to intrude, converting swamps to marsh or to open water. Large areas of swamp were therefore degraded. Louisiana provides a classic example of wetland loss from these combined factors. Europe has lost nearly half its wetlands. New Zealand lost 90 percent of its wetlands over a period of 150 years. Ecologists recognise that swamps provide valuable ecological services including flood control, fish production, water purification, carbon storage, wildlife habitat. In many parts of the world authorities protect swamps. In parts of Europe and North America, swamp restoration projects are becoming widespread.
The simplest steps to restoring swamps involve plugging drainage ditches and removing levees. Swamps and other wetlands have traditionally held a low property value compared to fields, prairies, or woodlands, they have a reputation for being unproductive land that cannot be utilized for human activities, other than hunting and trapping. Farmers, for example drained swamps next to their fields so as to gain more land usable for planting crops. Many societies now realize that swamps are critically important to providing fresh water and oxygen to all life, that they are breeding grounds for a wide variety of species. Indeed, floodplain swamps are important in fish production. Government environmental agencies are taking steps to protect and preserve swamps and other wetlands. In Europe, major effort is being invested in the restoration of swamp forests along rivers. Conservationists work to preserve swamps such as those in northwest Indiana in the United States Midwest that were preserved as part of the Indiana Dunes.
The problem of invasive species has been put into greater light such as in places like the Everglades. Swamps can be found on all continents except Antarctica; the largest swamp in the world is the Amazon River floodplain, significant for its large number of fish and tree species. The Sudd and the Okavango Delta are Africa's best known marshland areas; the Bangweulu Floodplains make up Africa's largest swamp. The Tigris-Euphrates river system is a large swamp and river system in southern Iraq, traditionally inhabited in part by the Marsh Arabs. In Asia, tropical peat swamps are located in mainland East Southeast Asia. In Southeast Asia, peatlands are found in low altitude coastal and sub-coastal areas and extend inland for distance more than 100 km along river valleys and across watersheds, they are to be found on the coasts of East Sumatra, West Papua, Papua New Guinea, Peninsular Malaya, Sarawak, Southeast Thailand, the Philippines. Indonesia has the largest area of tropical peatland. Of the total 440,000 km2 tropical peat swamp, about 210,000 km2 are located in Indonesia.
The Vasyugan Swamp is a large swamp in the western Siberia area of the Russian Federation. This is one of the largest swamps in the world; the Atchafalaya Swamp at the lower end of the Mississippi River is the largest swamp in the United States. It is an important example of southern cypress swamp but it has been altered by logging and levee construction. Other famous swamps in the United States are the forested portions of the Everglades, Okefenokee Swamp, Barley Barber Swamp, Great Cypress Swamp and the Great Dismal Swamp; the Okefenokee is located in extreme southeastern Georgia and extends into northeastern Florida. The Great Cypress Swamp is in Delaware but extends into Maryland on the Delmarva Peninsula. Point Lookout State Park on the southern tip of Maryland contains a large amount of swamps and marshes; the Great Dismal Swamp lies in extreme southeastern Virginia and extreme northeastern North Carolina. Both are National Wildlife Refuges. Another swamp area, Reelfoot Lake of extreme western Tennessee and Kentucky, was created by the 1811–12 New Madrid earthquakes.
Caddo Lake, the Great Dismal and Reelfoot are swamps. Swamps are called bayous in the southeastern United States in the Gulf Coast region; the worl
Municipal solid waste
Municipal solid waste known as trash or garbage in the United States and rubbish in Britain, is a waste type consisting of everyday items that are discarded by the public. "Garbage" can refer to food waste, as in a garbage disposal. In the European Union, the semantic definition is'mixed municipal waste,' given waste code 20 03 01 in the European Waste Catalog. Although the waste may originate from a number of sources that has nothing to do with a municipality, the traditional role of municipalities in collecting and managing these kinds of waste have produced the particular etymology'municipal.' The composition of municipal solid waste varies from municipality to municipality, it changes with time. In municipalities which have a well developed waste recycling system, the waste stream consists of intractable wastes such as plastic film and non-recyclable packaging materials. At the start of the 20th century, the majority of domestic waste in the UK consisted of coal ash from open fires. In developed areas without significant recycling activity it predominantly includes food wastes, market wastes, yard wastes, plastic containers and product packaging materials, other miscellaneous solid wastes from residential, commercial and industrial sources.
Most definitions of municipal solid waste do not include industrial wastes, agricultural wastes, medical waste, radioactive waste or sewage sludge. Waste collection is performed by the municipality within a given area; the term residual waste relates to waste left from household sources containing materials that have not been separated out or sent for processing. Waste can be classified in several ways but the following list represents a typical classification: Biodegradable waste: food and kitchen waste, green waste, paper Recyclable materials: paper, glass, jars, tin cans, aluminum cans, aluminum foil, certain plastics, clothes, batteries, etc. Inert waste: construction and demolition waste, rocks, debris Electrical and electronic waste - electrical appliances, light bulbs, washing machines, TVs, screens, mobile phones, alarm clocks, etc. Composite wastes: waste clothing, Tetra Packs, waste plastics such as toys Hazardous waste including most paints, tires, light bulbs, electrical appliances, fluorescent lamps, aerosol spray cans, fertilizers Toxic waste including pesticides and fungicides Biomedical waste, expired pharmaceutical drugs, etc.
The municipal solid waste industry has four components: recycling, composting and waste-to-energy via incineration. There is no single approach that can be applied to the management of all waste streams, therefore the Environmental Protection Agency, a U. S. federal government agency, developed a hierarchy ranking strategy for municipal solid waste. The Waste Management Hierarchy is made up of four levels ordered from most preferred to least preferred methods based on their environmental soundness: Source reduction and reuse; the functional element of collection includes not only the gathering of solid waste and recyclable materials, but the transport of these materials, after collection, to the location where the collection vehicle is emptied. This location may be a materials processing facility, a transfer station or a landfill disposal site. Waste handling and separation involves activities associated with waste management until the waste is placed in storage containers for collection. Handling encompasses the movement of loaded containers to the point of collection.
Separating different types of waste components is an important step in the handling and storage of solid waste at the source of collection. The types of means and facilities that are now used for the recovery of waste materials that have been separated at the source include curbside collection, drop-off and buy-back centers; the separation and processing of wastes that have been separated at the source and the separation of commingled wastes occur at a materials recovery facility, transfer stations, combustion facilities and treatment plants. This element involves two main steps. First, the waste is transferred from a smaller collection vehicle to larger transport equipment; the waste is transported over long distances, to a processing or disposal site. Today, the disposal of wastes by land filling or land spreading is the ultimate fate of all solid wastes, whether they are residential wastes collected and transported directly to a landfill site, residual materials from materials recovery facilities, residue from the combustion of solid waste, compost, or other substances from various solid waste processing facilities.
A modern sanitary landfill is not a dump. In the recent years environmental organizations, such as Freegle or Freecycle Network, have been gaining popularity for their online reuse networks; these networks provide a worldwide online registry of unwanted items that would otherwise be thrown away, for individuals and nonprofits to reuse or recycle. Therefore, this free Internet-based service reduces landfill pollution and promotes the gift economy. Landfills are created by land dumping. Land dumping methods vary, most it involves the mass dumping of waste into a designated area a hole or sidehill. After the waste is dumped, it is then
Porous medium
A porous medium or a porous material is a material containing pores. The skeletal portion of the material is called the "matrix" or "frame"; the pores are filled with a fluid. The skeletal material is a solid, but structures like foams are also usefully analyzed using concept of porous media. A porous medium is most characterised by its porosity. Other properties of the medium can sometimes be derived from the respective properties of its constituents and the media porosity and pores structure, but such a derivation is complex; the concept of porosity is only straightforward for a poroelastic medium. Both the solid matrix and the pore network are continuous, so as to form two interpenetrating continua such as in a sponge. However, there is a concept of closed porosity and effective porosity, i.e. the pore space accessible to flow. Many natural substances such as rocks and soil, biological tissues, man made materials such as cements and ceramics can be considered as porous media. Many of their important properties can only be rationalized by considering them to be porous media.
The concept of porous media is used in many areas of applied science and engineering: filtration, engineering, geosciences and biophysics, material science. Fluid flow through porous media is a subject of common interest and has emerged a separate field of study; the study of more general behaviour of porous media involving deformation of the solid frame is called poromechanics. The theory of porous flows has applications in inkjet printing and nuclear waste disposal technologies, among others. There are many idealized models of pore structures, they can be broadly divided into three categories: networks of capillaries arrays of solid particles trimodalPorous materials have a fractal-like structure, having a pore surface area that seems to grow indefinitely when viewed with progressively increasing resolution. Mathematically, this is described by assigning the pore surface a Hausdorff dimension greater than 2. Experimental methods for the investigation of pore structures include confocal microscopy and x-ray tomography.
One of the Laws for porous materials is the generalized Murray's law. The generalized Murray’s law is based on optimizing mass transfer by minimizing transport resistance in pores with a given volume, can be applicable for optimizing mass transfer involving mass variations and chemical reactions involving flow proceses, molecule or ion diffusion. For connecting a parent pipe with radius of r0 to many children pipes with radius of ri, the formula of generalized Murray's law is: r o a = 1 1 − X ∑ i = 1 N r i a, where the X is the ratio of mass variation during mass transfer in the parent pore, the exponent α is dependent on the type of the transfer. For laminar flow α =3. Cenocell Nanoporous materials NMR in porous media Percolation theory Reticulated foam
Smouldering
Smouldering or smoldering is the slow, low-temperature, flameless form of combustion, sustained by the heat evolved when oxygen directly attacks the surface of a condensed-phase fuel. Many solid materials can sustain a smouldering reaction, including coal, wood, tobacco, peat, plant litter, synthetic foams, charring polymers including polyurethane foam and some types of dust. Common examples of smouldering phenomena are the initiation of residential fires on upholstered furniture by weak heat sources, the persistent combustion of biomass behind the flaming front of wildfires; the fundamental difference between smouldering and flaming combustion is that smouldering occurs on the surface of the solid rather than in the gas phase. Smouldering is a surface phenomenon but can propagate to the interior of a porous fuel if it is permeable to flow; the characteristic temperature and heat released during smouldering are low compared to those in the flaming combustion. Smouldering propagates in a creeping fashion, around 0.1 mm/s, about ten times slower than flames spread over a solid.
In spite of its weak combustion characteristics, smouldering is a significant fire hazard. Smouldering emits toxic gases at a higher yield than flaming fires and leaves behind a significant amount of solid residue; the emitted gases are flammable and could be ignited in the gas phase, triggering the transition to flaming combustion. Many materials can sustain a smouldering reaction, including coal, decaying wood and sawdust, biomass fuels on the forest surface and subsurface, cotton clothing and string, polymeric foams. Smouldering fuels are porous, permeable to flow and formed by aggregates; these aggregates facilitate the surface reaction with oxygen by allowing gas flow through the fuel and providing a large surface area per unit volume. They act as thermal insulation, reducing heat losses; the most studied materials to date are polyurethane foams. The characteristics of smouldering fires make them a threat of new dimensions, taking the form of colossal underground fires or silent fire safety risks, as summarized below.
Fire safety: The main hazards posed by smouldering arise from the fact that it can be initiated and is difficult to detect. Fire statistics draw attention to the magnitude of smouldering combustion as the leading cause of fire deaths in residential areas. A common fire scenario is a cigarette igniting a piece of upholstered furniture; this ignition leads to a smouldering fire that lasts for a long period of time and silently until critical conditions are attained and flames erupt. Smouldering combustion is a fire-safety concern aboard space facilities, because the absence of gravity is thought to promote smouldering ignition and propagation. Wildfires: Smouldering combustion of the forest ground does not have the visual impact of flaming combustion. Smouldering of biomass can linger for days or weeks after flaming has ceased, resulting in large quantities of fuels consumed and becoming a global source of emissions to the atmosphere; the slow propagation leads to prolonged heating and might cause sterilizations of the soil or the killing of roots and plant stems at the ground level.
Subsurface fires: Fires occurring many meters below the surface are a type of smouldering event of colossal magnitude. Subsurface fires in coal mines, peat lands and landfills are rare events, but when active they can smoulder for long periods of time, emitting enormous quantities of combustion gases into the atmosphere, causing deterioration of air quality and subsequent health problems; the oldest and largest fires in the world, burning for centuries, are smouldering fires. These fires are fed by the oxygen in the small but continuous flow of air through natural pipe networks, fractured strata, openings or abandoned mine shafts which permit the air to circulate into the subsurface; the reduced heat losses and high thermal inertia of the underground together with high fuel availability promote long-term smouldering combustion and allow for creeping but extensive propagation. These fires prove difficult to detect, frustrate most efforts to extinguish them; the dramatic 1997 peatland fires in Borneo caused the recognition of subsurface smouldering fires as a global threat with significant economic and ecological impacts.
The summer of 2006 saw the resurgence of the Borneo peat fires. World Trade Center debris: After the attack and subsequent collapse of the Twin Towers on September 11, 2001, the colossal pile of debris left on the site smouldered for more than five months, it resisted attempts by fire fighters to extinguish it. The effects of the gaseous and aerosolized products of smouldering on the health of the emergency workers were significant but the details are still a matter of debate. Smouldering combustion has some beneficial applications. Biochar is the charcoal produced from the smouldering and/or pyrolysis of biomass, it has the potential to be a short-term
Marsh
A marsh is a wetland, dominated by herbaceous rather than woody plant species. Marshes can be found at the edges of lakes and streams, where they form a transition between the aquatic and terrestrial ecosystems, they are dominated by grasses, rushes or reeds. If woody plants are present they tend to be low-growing shrubs; this form of vegetation is what differentiates marshes from other types of wetland such as swamps, which are dominated by trees, mires, which are wetlands that have accumulated deposits of acidic peat. Marshes provide a habitat for many species of plants and insects that have adapted to living in flooded conditions; the plants must be able to survive in wet mud with low oxygen levels. Many of these plants therefore have aerenchyma, channels within the stem that allow air to move from the leaves into the rooting zone. Marsh plants tend to have rhizomes for underground storage and reproduction. Familiar examples include cattails, sedges and sawgrass. Aquatic animals, from fish to salamanders, are able to live with a low amount of oxygen in the water.
Some can obtain oxygen from the air instead, while others can live indefinitely in conditions of low oxygen. Marshes provide habitats for many kinds of invertebrates, amphibians and aquatic mammals. Marshes have high levels of biological production, some of the highest in the world, therefore are important in supporting fisheries. Marshes improve water quality by acting as a sink to filter pollutants and sediment from the water that flows through them. Marshes are able to absorb water during periods of heavy rainfall and release it into waterways and therefore reduce the magnitude of flooding; the pH in marshes tends to be neutral to alkaline, as opposed to bogs, where peat accumulates under more acid conditions. Marshes differ depending on their location and salinity. Both of these factors influence the range and scope of animal and plant life that can survive and reproduce in these environments; the three main types of marsh are salt marshes, freshwater tidal marshes, freshwater marshes. These three can be found worldwide and each contains a different set of organisms.
Saltwater marshes are found around the world in mid to high latitudes, wherever there are sections of protected coastline. They are located close enough to the shoreline that the motion of the tides affects them, sporadically, they are covered with water, they flourish where the rate of sediment buildup is greater than the rate at which the land level is sinking. Salt marshes are dominated by specially adapted rooted vegetation salt-tolerant grasses. Salt marshes are most found in lagoons, on the sheltered side of shingle or sandspit; the currents there carry the fine particles around to the quiet side of the spit and sediment begins to build up. These locations allow the marshes to absorb the excess nutrients from the water running through them before they reach the oceans and estuaries; these marshes are declining. Coastal development and urban sprawl has caused significant loss of these essential habitats. Although considered a freshwater marsh, this form of marsh is affected by the ocean tides.
However, without the stresses of salinity at work in its saltwater counterpart, the diversity of the plants and animals that live in and use freshwater tidal marshes is much higher than in salt marshes. The most serious threats to this form of marsh are the increasing size and pollution of the cities surrounding them. Ranging in both size and geographic location, freshwater marshes make up the most common form of wetland in North America, they are the most diverse of the three types of marsh. Some examples of freshwater marsh types in North America are: Wet meadows occur in areas such as shallow lake basins, low-lying depressions, the land between shallow marshes and upland areas, they occur on the edges of large lakes and rivers. Wet meadows have high plant diversity and high densities of buried seeds, they are flooded but are dry in the summer. Vernal pools are a type of marsh found only seasonally in shallow depressions in the land, they can be covered in shallow water, but in the summer and fall, they can be dry.
In western North America, vernal pools tend to form in open grasslands, whereas in the east they occur in forested landscapes. Further south, vernal pools form in pine flatwoods. Many amphibian species depend upon vernal pools for spring breeding. An example is the endangered gopher frog. Similar temporary ponds occur in other world ecosystems. However, the term vernal pool can be applied to all such temporary pool ecosystems. Playa lakes are a form of shallow freshwater marsh that occurs in the southern high plains of the United States. Like vernal pools, they are only present at certain times of the year and have a circular shape; as the playa dries during the summer, conspicuous plant zonation develops along the shoreline. Prairie potholes are found in the northern parts of North America as the Prairie Pothole Region; these landscapes were once covered by glaciers, as a result shallow depressions were formed in great numbers. These depressions fill with water in the spring, they provide important breeding habitats for many species of waterfowl.
Some pools only occur seasonally. Many kinds of marsh occur along the fringes of large rivers; the different types are produced by factors such as water level, ice scour, waves. Large tracts of marshland have been embanked and ar
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula H2S. It is a colorless chalcogen hydride gas with the characteristic foul odor of rotten eggs, it is poisonous and flammable. Hydrogen sulfide is produced from the microbial breakdown of organic matter in the absence of oxygen gas, such as in swamps and sewers. H2S occurs in volcanic gases, natural gas, in some sources of well water; the human body uses it as a signaling molecule. Swedish chemist Carl Wilhelm Scheele is credited with having discovered hydrogen sulfide in 1777; the British English spelling of this compound is hydrogen sulphide, but this spelling is not recommended by the International Union of Pure and Applied Chemistry or the Royal Society of Chemistry. Hydrogen sulfide is denser than air. Hydrogen sulfide burns in oxygen with a blue flame to form sulfur water. In general, hydrogen sulfide acts as a reducing agent in the presence of base, which forms SH−. At high temperatures or in the presence of catalysts, sulfur dioxide reacts with hydrogen sulfide to form elemental sulfur and water.
This reaction is exploited in the Claus process, an important industrial method to dispose of hydrogen sulfide. Hydrogen sulfide is soluble in water and acts as a weak acid, giving the hydrosulfide ion HS−. Hydrogen sulfide and its solutions are colorless; when exposed to air, it oxidizes to form elemental sulfur, not soluble in water. The sulfide anion S2− is not formed in aqueous solution. Hydrogen sulfide reacts with metal ions to form metal sulfides, which are insoluble dark colored solids. Lead acetate paper is used to detect hydrogen sulfide because it converts to lead sulfide, black. Treating metal sulfides with strong acid liberates hydrogen sulfide. At pressures above 90 GPa, hydrogen sulfide becomes a metallic conductor of electricity; when cooled below a critical temperature this high-pressure phase exhibits superconductivity. The critical temperature increases with pressure. If hydrogen sulfide is pressurized at higher temperatures cooled, the critical temperature reaches 203 K, the highest accepted superconducting critical temperature as of 2015.
By substituting a small part of sulfur with phosphorus and using higher pressures, it has been predicted that it may be possible to raise the critical temperature to above 0 °C and achieve room-temperature superconductivity. Hydrogen sulfide is most obtained by its separation from sour gas, natural gas with high content of H2S, it can be produced by treating hydrogen with molten elemental sulfur at about 450 °C. Hydrocarbons can serve as a source of hydrogen in this process. Sulfate-reducing bacteria generate usable energy under low-oxygen conditions by using sulfates to oxidize organic compounds or hydrogen. A standard lab preparation is to treat ferrous sulfide with a strong acid in a Kipp generator: FeS + 2 HCl → FeCl2 + H2SFor use in qualitative inorganic analysis, thioacetamide is used to generate H2S: CH3CNH2 + H2O → CH3CNH2 + H2SMany metal and nonmetal sulfides, e.g. aluminium sulfide, phosphorus pentasulfide, silicon disulfide liberate hydrogen sulfide upon exposure to water: 6 H2O + Al2S3 → 3 H2S + 2 Al3This gas is produced by heating sulfur with solid organic compounds and by reducing sulfurated organic compounds with hydrogen.
Water heaters can aid the conversion of sulfate in water to hydrogen sulfide gas. This is due to providing a warm environment sustainable for sulfur bacteria and maintaining the reaction which interacts between sulfate in the water and the water heater anode, made from magnesium metal. Hydrogen sulfide can be generated in cells via non enzymatic pathway. H2S in the body acts as a gaseous signaling molecule, known to inhibit Complex IV of the mitochondrial electron transport chain which reduces ATP generation and biochemical activity within cells. Three enzymes are known to synthesize H2S: cystathionine γ-lyase, cystathionine β-synthetase and 3-mercaptopyruvate sulfurtransferase; these enzymes have been identified in a breadth of biological cells and tissues, their activity has been observed to be induced by a number of disease states. It is becoming clear that H2S is an important mediator of a wide range of cell functions in health and in disease. CBS and CSE are the main proponents of H2S biogenesis.
These enzymes are characterized by the transfer of a sulfur atom from methionine to serine to form a cysteine molecule. 3-MST contributes to hydrogen sulfide production by way of the cysteine catabolic pathway. Dietary amino acids, such as methionine and cysteine serve as the primary substrates for the transulfuration pathways and in the production of hydrogen sulfide. Hydrogen sulfide can be synthesized by non-enzymatic pathway, derived from proteins such as ferredoxins and Rieske proteins. H2S has been shown to be involved in physiological processes like vasoconstriction in animals, increasing seed germination and stress responses in plants. Hydrogen sulfide signaling is innately intertwined with physiological processes that are known to be moderated by reactive oxygen species and reactive nitrogen species. H2S has been shown to interact with NO resulting in severa
Ecosystem
An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy is incorporated into plant tissue. By feeding on plants and on one-another, animals play an important role in the movement of matter and energy through the system, they influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used by plants and other microbes. Ecosystems are controlled by internal factors. External factors such as climate, the parent material which forms the soil and topography, control the overall structure of an ecosystem, but are not themselves influenced by the ecosystem. Ecosystems are dynamic entities—they are subject to periodic disturbances and are in the process of recovering from some past disturbance.
Ecosystems in similar environments that are located in different parts of the world can end up doing things differently because they have different pools of species present. Internal factors not only control ecosystem processes but are controlled by them and are subject to feedback loops. Resource inputs are controlled by external processes like climate and parent material. Resource availability within the ecosystem is controlled by internal factors like decomposition, root competition or shading. Although humans operate within ecosystems, their cumulative effects are large enough to influence external factors like climate. Biodiversity affects ecosystem functioning, as do the processes of disturbance and succession. Ecosystems provide a variety of services upon which people depend; the term ecosystem was first used in 1935 in a publication by British ecologist Arthur Tansley. Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.
He refined the term, describing it as "The whole system... including not only the organism-complex, but the whole complex of physical factors forming what we call the environment". Tansley regarded ecosystems not as natural units, but as "mental isolates". Tansley defined the spatial extent of ecosystems using the term ecotope. G. Evelyn Hutchinson, a limnologist, a contemporary of Tansley's, combined Charles Elton's ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky; as a result, he suggested. This would, in turn, limit the abundance of animals. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson's students, brothers Howard T. Odum and Eugene P. Odum, further developed a "systems approach" to the study of ecosystems; this allowed them to study the flow of material through ecological systems. Ecosystems are controlled both by internal factors. External factors called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem.
The most important of these is climate. Climate determines the biome. Rainfall patterns and seasonal temperatures influence photosynthesis and thereby determine the amount of water and energy available to the ecosystem. Parent material determines the nature of the soil in an ecosystem, influences the supply of mineral nutrients. Topography controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. For example, ecosystems can be quite different if situated in a small depression on the landscape, versus one present on an adjacent steep hillside. Other external factors that play an important role in ecosystem functioning include time and potential biota; the set of organisms that can be present in an area can significantly affect ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things differently because they have different pools of species present; the introduction of non-native species can cause substantial shifts in ecosystem function.
Unlike external factors, internal factors in ecosystems not only control ecosystem processes but are controlled by them. They are subject to feedback loops. While the resource inputs are controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading. Other factors like disturbance, succession or the types of species present are internal factors. Primary production is the production of organic matter from inorganic carbon sources; this occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels, it drives the carbon cycle, which influences global climate via the greenhouse effect. Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen.
The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production. About half of the GPP is consumed in plant respiration; the remainder, that portion of GPP, not used up by respirati
