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Musicals
In the 2017 Broadway musical Anastasia, based on the 1997 film, the bridge is seen in the second half of the musical and in the closing scene. Anastasia was the granddaughter of Alexander III, who is mentioned in the musical.
Sports
In June 2017, with Paris competing against Los Angeles to host the 2024 Summer Olympics (the latter would went on to host the 2028 edition) , Paris turned some of its world-famous landmarks over to sports and installed diving boards on the Alexandre III bridge that spanned the Seine. The swimming leg of the triathlon and marathon swimming events was held here.
Gallery
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Eucalyptol (also called cineole) is a monoterpenoid colorless liquid, and a bicyclic ether. It has a fresh camphor-like odor and a spicy, cooling taste. It is insoluble in water, but miscible with organic solvents. Eucalyptol makes up about 70–90% of eucalyptus oil. Eucalyptol forms crystalline adducts with hydrohalic acids, o-cresol, resorcinol, and phosphoric acid. Formation of these adducts is useful for purification.
In 1870, F. S. Cloez identified and ascribed the name "eucalyptol" to the dominant portion of Eucalyptus globulus oil.
Uses
Because of its pleasant, spicy aroma and taste, eucalyptol is used in flavorings, fragrances, and cosmetics. Cineole-based eucalyptus oil is used as a flavoring at low levels (0.002%) in various products, including baked goods, confectionery, meat products, and beverages. In a 1994 report released by five top cigarette companies, eucalyptol was listed as one of the 599 additives to cigarettes. It is claimed to be added to improve the flavor.
Eucalyptol is an ingredient in commercial mouthwashes, and has been used in traditional medicine as a cough suppressant.
Other
Eucalyptol exhibits insecticidal and insect repellent properties.
In contrast, eucalyptol is one of many compounds that are attractive to males of various species of orchid bees, which gather the chemical to synthesize pheromones; it is commonly used as bait to attract and collect these bees for study. One such study with Euglossa imperialis, a nonsocial orchid bee species, has shown that the presence of cineole (also eucalyptol) elevates territorial behavior and specifically attracts the male bees. It was even observed that these males would periodically leave their territories to forage for chemicals such as cineole, thought to be important for attracting and mating with females, to synthesize pheromones.
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Toxicology
Eucalyptol has a toxicity (LD50) of 2.48 grams per kg (rat). Ingestion in significant quantities is likely to cause headache and gastric distress, such as nausea and vomiting. Because of its low viscosity, it may directly enter the lungs if swallowed, or if subsequently vomited. Once in the lungs, it is difficult to remove and can cause delirium, convulsions, severe injury or death.
Biosynthesis
Eucalyptol is generated from geranyl pyrophosphate (GPP) which isomerizes to (S)-linalyl diphosphate (LPP). Ionization of the pyrophosphate, catalyzed by cineole synthase, produces eucalyptol. The process involves the intermediacy of alpha-terpinyl cation.
Plants containing eucalyptol
Aframomum corrorima
Artemisia tridentata
Cannabis
Cinnamomum camphora, camphor laurel (50%)
Eucalyptus globulus
Eucalyptus largiflorens
Eucalyptus salmonophloia
Eucalyptus staigeriana Eucalyptus wandoo Hedychium coronarium, butterfly lily
Helichrysum gymnocephalum Kaempferia galanga, galangal, (5.7%)
S. officinalis subsp. lavandulifolia (syn. S. lavandulifolia), Spanish sage (13%)
Salvia rosmarinus, rosemary
Turnera diffusa, damiana
Umbellularia californica, pepperwood (22.0%)
Zingiber officinale, ginger
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Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about , which is about 20% of Earth's radius or 70% of the Moon's radius.
There are no samples of the core accessible for direct measurement, as there are for Earth's mantle. The characteristics of the core have been deduced mostly from measurements of seismic waves and Earth's magnetic field. The inner core is believed to be composed of an iron–nickel alloy with some other elements. The temperature at its surface is estimated to be approximately , about the temperature at the surface of the Sun.
The inner core is solid at high temperature because of its high pressure, in accordance with the Simon-Glatzel equation.
Scientific history
Earth was discovered to have a solid inner core distinct from its molten Earth's outer core in 1936, by the Danish seismologist Inge Lehmann's study of seismograms from earthquakes in New Zealand, detected by sensitive seismographs on the Earth's surface. She deduced that the seismic waves reflect off the boundary of the inner core and inferred a radius of for the inner core, not far from the currently accepted value of . In 1938, Beno Gutenberg and Charles Richter analyzed a more extensive set of data and estimated the thickness of the outer core as with a steep but continuous thick transition to the inner core, implying a radius between for the inner core.
A few years later, in 1940, it was hypothesized that this inner core was made of solid iron. In 1952, Francis Birch published a detailed analysis of the available data and concluded that the inner core was probably crystalline iron.
The boundary between the inner and outer cores is sometimes called the "Lehmann discontinuity", although the name usually refers to another discontinuity. The name "Bullen" or "Lehmann-Bullen discontinuity", after Keith Edward Bullen, has been proposed, but its use seems to be rare. The rigidity of the inner core was confirmed in 1971.
Adam Dziewonski and James Freeman Gilbert established that measurements of normal modes of vibration of Earth caused by large earthquakes were consistent with a liquid outer core. In 2005, shear waves were detected passing through the inner core; these claims were initially controversial, but are now gaining acceptance.
Data sources
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Seismic waves
Almost all measurements that scientists have about the physical properties of the inner core are the seismic waves that pass through it. Deep earthquakes generate the most informative waves, 30 km or more below the surface of the Earth (where the mantle is relatively more homogeneous) and are recorded by seismographs as they reach the surface, all over the globe.
Seismic waves include "P" (primary or pressure) compressional waves that can travel through solid or liquid materials, and "S" (secondary or shear) shear waves that can only propagate through rigid elastic solids. The two waves have different velocities and are damped at different rates as they travel through the same material.
Of particular interest are the so-called "PKiKP" waves—pressure waves (P) that start near the surface, cross the mantle-core boundary, travel through the core (K), are reflected at the inner core boundary (i), cross the liquid core (K) again, cross back into the mantle, and are detected as pressure waves (P) at the surface. Also of interest are the "PKIKP" waves, that travel through the inner core (I) instead of being reflected at its surface (i). Those signals are easier to interpret when the path from source to detector is close to a straight line—namely, when the receiver is just above the source for the reflected PKiKP waves, and antipodal to it for the transmitted PKIKP waves.
While S waves cannot reach or leave the inner core as such, P waves can be converted into S waves, and vice versa, as they hit the boundary between the inner and outer core at an oblique angle. The "PKJKP" waves are similar to the PKIKP waves, but are converted into S waves when they enter the inner core, travel through it as S waves (J), and are converted again into P waves when they exit the inner core. Thanks to this phenomenon, it is known that the inner core can propagate S waves, and therefore must be solid.
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Other sources
Other sources of information about the inner core include
the Earth's magnetic field. While it seems to be generated mostly by fluid and electric currents in the outer core, those currents are strongly affected by the presence of the solid inner core and by the heat that flows out of it. (Although made of iron, the core is not ferromagnetic, due to being above the Curie temperature.)
the Earth's mass, its gravitational field, and its angular inertia. These are all affected by the density and dimensions of the inner layers.
the natural oscillation frequencies and modes of the whole Earth oscillations, when large earthquakes make the planet "ring" like a bell. These oscillations also depend strongly on the inner layers' density, size, and shape.
Physical properties
Seismic wave velocity
The velocity of the S waves in the core varies smoothly from about 3.7 km/s at the center to about 3.5 km/s at the surface. That is considerably less than the velocity of S waves in the lower crust (about 4.5 km/s) and less than half the velocity in the deep mantle, just above the outer core (about 7.3 km/s).
The velocity of the P-waves in the core also varies smoothly through the inner core, from about 11.4 km/s at the center to about 11.1 km/s at the surface. Then the speed drops abruptly at the inner-outer core boundary to about 10.4 km/s.
Size and shape
On the basis of the seismic data, the inner core is estimated to be about 1221 km in radius (2442 km in diameter), which is about 19% of the radius of the Earth and 70% of the radius of the Moon.
Its volume is about 7.6 billion cubic km (), which is about (0.69%) of the volume of the whole Earth.
Its shape is believed to be close to an oblate ellipsoid of revolution, like the surface of the Earth, only more spherical: the flattening is estimated to be between and , meaning that the radius along the Earth's axis is estimated to be about 3 km shorter than the radius at the equator. In comparison, the flattening of the Earth as a whole is close to , and the polar radius is 21 km shorter than the equatorial one.
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Pressure and gravity
The pressure in the Earth's inner core is slightly higher than it is at the boundary between the outer and inner cores: It ranges from about .
The acceleration of gravity at the surface of the inner core can be computed to be 4.3 m/s2; which is less than half the value at the surface of the Earth (9.8 m/s2).
Density and mass
The density of the inner core is believed to vary smoothly from about 13.0 kg/L (= g/cm3 = t/m3) at the center to about 12.8 kg/L at the surface. As it happens with other material properties, the density drops suddenly at that surface: The liquid just above the inner core is believed to be significantly less dense, at about 12.1 kg/L. For comparison, the average density in the upper 100 km of the Earth is about 3.4 kg/L.
That density implies a mass of about 1023 kg for the inner core, which is (1.7%) of the mass of the whole Earth.
Temperature
The temperature of the inner core can be estimated from the melting temperature of impure iron at the pressure which iron is under at the boundary of the inner core (about 330 GPa). From these considerations, in 2002, D. Alfè and others estimated its temperature as between and . However, in 2013, S. Anzellini and others obtained experimentally a substantially higher temperature for the melting point of iron, .
Iron can be solid at such high temperatures only because its melting temperature increases dramatically at pressures of that magnitude (see the Clausius–Clapeyron relation).
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Magnetic field
In 2010, Bruce Buffett determined that the average magnetic field in the liquid outer core is about 2.5 milliteslas (25 gauss), which is about 40 times the maximum strength at the surface. He started from the known fact that the Moon and Sun cause tides in the liquid outer core, just as they do on the oceans on the surface. He observed that motion of the liquid through the local magnetic field creates electric currents, that dissipate energy as heat according to Ohm's law. This dissipation, in turn, damps the tidal motions and explains previously detected anomalies in Earth's nutation. From the magnitude of the latter effect he could calculate the magnetic field. The field inside the inner core presumably has a similar strength. While indirect, this measurement does not depend significantly on any assumptions about the evolution of the Earth or the composition of the core.
Viscosity
Although seismic waves propagate through the core as if it were solid, the measurements cannot distinguish a solid material from an extremely viscous one. Some scientists have therefore considered whether there may be slow convection in the inner core (as is believed to exist in the mantle). That could be an explanation for the anisotropy detected in seismic studies. In 2009, B. Buffett estimated the viscosity of the inner core at 1018 Pa·s, which is a sextillion times the viscosity of water, and more than a billion times that of pitch.
Composition
There is still no direct evidence about the composition of the inner core. However, based on the relative prevalence of various chemical elements in the Solar System, the theory of planetary formation, and constraints imposed or implied by the chemistry of the rest of the Earth's volume, the inner core is believed to consist primarily of an iron–nickel alloy.
At the estimated pressures and temperatures of the core, it is predicted that pure iron could be solid, but its density would exceed the known density of the core by approximately 3%. That result implies the presence of lighter elements in the core, such as silicon, oxygen, or sulfur, in addition to the probable presence of nickel. Recent estimates (2007) allow for up to 10% nickel and 2–3% of unidentified lighter elements.
According to computations by D. Alfè and others, the liquid outer core contains 8–13% of oxygen, but as the iron crystallizes out to form the inner core the oxygen is mostly left in the liquid.
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Laboratory experiments and analysis of seismic wave velocities seem to indicate that the inner core consists specifically of ε-iron, a crystalline form of the metal with the hexagonal close-packed () structure. That structure can still admit the inclusion of small amounts of nickel and other elements.
Structure
Many scientists had initially expected that the inner core would be found to be homogeneous, because that same process should have proceeded uniformly during its entire formation. It was even suggested that Earth's inner core might be a single crystal of iron.
Axis-aligned anisotropy
In 1983, G. Poupinet and others observed that the travel time of PKIKP waves (P waves that travel through the inner core) was about 2 seconds less for straight north–south paths than straight paths on the equatorial plane. Even taking into account the flattening of the Earth at the poles (about 0.33% for the whole Earth, 0.25% for the inner core) and crust and upper mantle heterogeneities, this difference implied that P waves (of a broad range of wavelengths) travel through the inner core about 1% faster in the north–south direction than along directions perpendicular to that.
This P wave speed anisotropy has been confirmed by later studies, including more seismic data and study of the free oscillations of the whole Earth. Some authors have claimed higher values for the difference, up to 4.8%; however, in 2017 Daniel Frost and Barbara Romanowicz confirmed that the value is between 0.5% and 1.5%.
Non-axial anisotropy
Some authors have claimed that P wave speed is faster in directions that are oblique or perpendicular to the N−S axis, at least in some regions of the inner core. However, these claims have been disputed by Frost and Romanowicz, who instead claim that the direction of maximum speed is as close to the Earth's rotation axis as can be determined.
Causes of anisotropy
Laboratory data and theoretical computations indicate that the propagation of pressure waves in the crystals of ε-iron are strongly anisotropic, too, with one "fast" axis and two equally "slow" ones. A preference for the crystals in the core to align in the north–south direction could account for the observed seismic anomaly.
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One phenomenon that could cause such partial alignment is slow flow ("creep") inside the inner core, from the equator towards the poles or vice versa. That flow would cause the crystals to partially reorient themselves according to the direction of the flow. In 1996, S. Yoshida and others proposed that such a flow could be caused by higher rate of freezing at the equator than at polar latitudes. An equator-to-pole flow then would set up in the inner core, tending to restore the isostatic equilibrium of its surface.
Others suggested that the required flow could be caused by slow thermal convection inside the inner core. T. Yukutake claimed in 1998 that such convective motions were unlikely. However, B. Buffet in 2009 estimated the viscosity of the inner core and found that such convection could have happened, especially when the core was smaller.
On the other hand, M. Bergman in 1997 proposed that the anisotropy was due to an observed tendency of iron crystals to grow faster when their crystallographic axes are aligned with the direction of the cooling heat flow. He, therefore, proposed that the heat flow out of the inner core would be biased towards the radial direction.
In 1998, S. Karato proposed that changes in the magnetic field might also deform the inner core slowly over time.
Multiple layers
In 2002, M. Ishii and A. Dziewoński presented evidence that the solid inner core contained an "innermost inner core" (IMIC) with somewhat different properties than the shell around it. The nature of the differences and radius of the IMIC are still unresolved as of 2019, with proposals for the latter ranging from 300 km to 750 km.
A. Wang and X. Song proposed, in 2018, a three-layer model, with an "inner inner core" (IIC) with about 500 km radius, an "outer inner core" (OIC) layer about 600 km thick, and an isotropic shell 100 km thick. In this model, the "faster P wave" direction would be parallel to the Earth's axis in the OIC, but perpendicular to that axis in the IIC. However, the conclusion has been disputed by claims that there need not be sharp discontinuities in the inner core, only a gradual change of properties with depth.
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In 2023, a study reported new evidence "for an anisotropically-distinctive innermost inner core" – a ~650-km thick innermost ball – "and its transition to a weakly anisotropic outer shell, which could be a fossilized record of a significant global event from the past." They suggest that atoms in the IIC atoms are [packed] slightly differently than its outer layer, causing seismic waves to pass through the IIC at different speeds than through the surrounding core (P-wave speeds ~4% slower at ~50° from the Earth’s rotation axis).
Lateral variation
In 1997, S. Tanaka and H. Hamaguchi claimed, on the basis of seismic data, that the anisotropy of the inner core material, while oriented N−S, was more pronounced in "eastern" hemisphere of the inner core (at about 110 °E longitude, roughly under Borneo) than in the "western" hemisphere (at about 70 °W, roughly under Colombia).
Alboussère and others proposed that this asymmetry could be due to melting in the Eastern hemisphere and re-crystallization in the Western one. C. Finlay conjectured that this process could explain the asymmetry in the Earth's magnetic field.
However, in 2017 Frost and Romanowicz disputed those earlier inferences, claiming that the data shows only a weak anisotropy, with the speed in the N−S direction being only 0.5% to 1.5% faster than in equatorial directions, and no clear signs of E−W variation.
Other structure
Other researchers claim that the properties of the inner core's surface vary from place to place across distances as small as 1 km. This variation is surprising since lateral temperature variations along the inner-core boundary are known to be extremely small (this conclusion is confidently constrained by magnetic field observations).
Growth
The Earth's inner core is thought to be slowly growing as the liquid outer core at the boundary with the inner core cools and solidifies due to the gradual cooling of the Earth's interior (about 100 degrees Celsius per billion years).
According to calculations by Alfé and others, as the iron crystallizes onto the inner core, the liquid just above it becomes enriched in oxygen, and therefore less dense than the rest of the outer core. This process creates convection currents in the outer core, which are thought to be the prime driver for the currents that create the Earth's magnetic field.
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The existence of the inner core also affects the dynamic motions of liquid in the outer core, and thus may help fix the magnetic field.
Dynamics
Because the inner core is not rigidly connected to the Earth's solid mantle, the possibility that it rotates slightly more quickly or slowly than the rest of Earth has long been entertained. In the 1990s, seismologists made various claims about detecting this kind of super-rotation by observing changes in the characteristics of seismic waves passing through the inner core over several decades, using the aforementioned property that it transmits waves more quickly in some directions. In 1996, X. Song and P. Richards estimated this "super-rotation" of the inner core relative to the mantle as about one degree per year. In 2005, they and J. Zhang compared recordings of "seismic doublets" (recordings by the same station of earthquakes occurring in the same location on the opposite side of the Earth, years apart), and revised that estimate to 0.3 to 0.5 degree per year. In 2023, it was reported that the core stopped spinning faster than the planet's surface around 2009 and likely is now rotating slower than it. This is not thought to have major effects and one cycle of the oscillation is thought to be about seven decades, coinciding with several other geophysical periodicities, "especially the length of day and magnetic field".
In 1999, M. Greff-Lefftz and H. Legros noted that the gravitational fields of the Sun and Moon that are responsible for ocean tides also apply torques to the Earth, affecting its axis of rotation and a slowing down of its rotation rate. Those torques are felt mainly by the crust and mantle, so that their rotation axis and speed may differ from overall rotation of the fluid in the outer core and the rotation of the inner core. The dynamics is complicated because of the currents and magnetic fields in the inner core. They find that the axis of the inner core wobbles (nutates) slightly with a period of about 1 day. With some assumptions on the evolution of the Earth, they conclude that the fluid motions in the outer core would have entered resonance with the tidal forces at several times in the past (3.0, 1.8, and 0.3 billion years ago). During those epochs, which lasted 200–300 million years each, the extra heat generated by stronger fluid motions might have stopped the growth of the inner core.
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Age
Theories about the age of the core are part of theories of the history of Earth. It is widely believed that the Earth's solid inner core formed out of an initially completely liquid core as the Earth cooled. However, the time when this process started is unknown.
Two main approaches have been used to infer the age of the inner core: thermodynamic modeling of the cooling of the Earth, and analysis of paleomagnetic evidence. The estimates yielded by these methods vary from 0.5 to 2 billion years old.
Thermodynamic evidence
One of the ways to estimate the age of the inner core is by modeling the cooling of the Earth, constrained by a minimum value for the heat flux at the core–mantle boundary (CMB). That estimate is based on the prevailing theory that the Earth's magnetic field is primarily triggered by convection currents in the liquid part of the core, and the fact that a minimum heat flux is required to sustain those currents. The heat flux at the CMB at present time can be reliably estimated because it is related to the measured heat flux at Earth's surface and to the measured rate of mantle convection.
In 2001, S. Labrosse and others, assuming that there were no radioactive elements in the core, gave an estimate of 1±0.5 billion years for the age of the inner core — considerably less than the estimated age of the Earth and of its liquid core (about 4.5 billion years) In 2003, the same group concluded that, if the core contained a reasonable amount of radioactive elements, the inner core's age could be a few hundred million years older.
In 2012, theoretical computations by M. Pozzo and others indicated that the electrical conductivity of iron and other hypothetical core materials, at the high pressures and temperatures expected there, were two or three times higher than assumed in previous research. These predictions were confirmed in 2013 by measurements by Gomi and others. The higher values for electrical conductivity led to increased estimates of the thermal conductivity, to 90 W/m·K; which, in turn, lowered estimates of its age to less than 700 million years old.
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However, in 2016 Konôpková and others directly measured the thermal conductivity of solid iron at inner core conditions, and obtained a much lower value, 18–44 W/m·K. With those values, they obtained an upper bound of 4.2 billion years for the age of the inner core, compatible with the paleomagnetic evidence.
In 2014, Driscoll and Bercovici published a thermal history of the Earth that avoided the so-called mantle thermal catastrophe and new core paradox by invoking 3 TW of radiogenic heating by the decay of in the core. Such high abundances of K in the core are not supported by experimental partitioning studies, so such a thermal history remains highly debatable.
Paleomagnetic evidence
Another way to estimate the age of the Earth is to analyze changes in the magnetic field of Earth during its history, as trapped in rocks that formed at various times (the "paleomagnetic record"). The presence or absence of the solid inner core could result in different dynamic processes in the core that could lead to noticeable changes in the magnetic field.
In 2011, Smirnov and others published an analysis of the paleomagnetism in a large sample of rocks that formed in the Neoarchean (2.8–2.5 billion years ago) and the Proterozoic (2.5–0.541 billion). They found that the geomagnetic field was closer to that of a magnetic dipole during the Neoarchean than after it. They interpreted that change as evidence that the dynamo effect was more deeply seated in the core during that epoch, whereas in the later time currents closer to the core-mantle boundary grew in importance. They further speculate that the change may have been due to growth of the solid inner core between 3.5–2.0 billion years ago.
In 2015, Biggin and others published the analysis of an extensive and carefully selected set of Precambrian samples and observed a prominent increase in the Earth's magnetic field strength and variance around 1.0–1.5 billion years ago. This change had not been noticed before due to the lack of sufficient robust measurements. They speculated that the change could be due to the birth of Earth's solid inner core. From their age estimate they derived a rather modest value for the thermal conductivity of the outer core, that allowed for simpler models of the Earth's thermal evolution.
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In 2016, P. Driscoll published a numerical evolving dynamo model that made a detailed prediction of the paleomagnetic field evolution over 0.0–2.0 Ga. The evolving dynamo model was driven by time-variable boundary conditions produced by the thermal history solution in Driscoll and Bercovici (2014). The evolving dynamo model predicted a strong-field dynamo prior to 1.7 Ga that is multipolar, a strong-field dynamo from 1.0–1.7 Ga that is predominantly dipolar, a weak-field dynamo from 0.6–1.0 Ga that is a non-axial dipole, and a strong-field dynamo after inner core nucleation from 0.0–0.6 Ga that is predominantly dipolar.
An analysis of rock samples from the Ediacaran epoch (formed about 565 million years ago), published by Bono and others in 2019, revealed unusually low intensity and two distinct directions for the geomagnetic field during that time that provides support for the predictions by Driscoll (2016). Considering other evidence of high frequency of magnetic field reversals around that time, they speculate that those anomalies could be due to the onset of formation of the inner core, which would then be 0.5 billion years old. A News and Views by P. Driscoll summarizes the state of the field following the Bono results. New paleomagnetic data from the Cambrian appear to support this hypothesis.
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Notonectidae is a cosmopolitan family of aquatic insects in the order Hemiptera, commonly called backswimmers because they swim "upside down" (inverted). They are all predators and typically range from in length. They are similar in appearance to Corixidae (water boatmen), but can be separated by differences in their dorsal-ventral coloration, front legs, and predatory behavior. Their dorsum is convex, lightly colored without cross striations. Their front tarsi are not scoop-shaped and their hind legs are fringed for swimming. There are about 350 species in two subfamilies: Notonectinae with seven genera, and Anisopinae with four genera. Members in the former subfamily are often larger than those in the latter.
Backswimmers swim on their backs, vigorously paddling with their long, hair-fringed hind legs and attack prey as large as tadpoles and small fish. They can inflict a painful "bite" on a human being, actually a stab with their sharp tubular mouthparts (proboscis). They inhabit still freshwater, e.g. lakes, ponds, marshes, and are sometimes found in garden ponds and even swimming pools. Although primarily aquatic, they can fly well and so can disperse easily to new habitats.
The best-known genus of backswimmers is Notonecta – streamlined, deep-bodied bugs up to long, green, brown, or yellowish in colour. The common backswimmer, N. glauca, is widespread in Europe, including the United Kingdom where it is known as the greater water boatman. Another of the same region, N. maculata, is distinguished by its mottled brick-coloured forewings.
In contrast to other aquatic insects that cling to submerged objects, the two genera Anisops and Buenoa uses a unique system to stay submerged: using the extra oxygen supply from haemoglobin in their abdomen, instead of using oxygen dissolved in the water. The size of these air bubbles, which provide buoyancy, changes as the nitrogen dissolves into the blood and the oxygen is used in respiration. This allows for regulation of the size of the air bubbles and their concentration of oxygen.
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Gloss is an optical property which indicates how well a surface reflects light in a specular (mirror-like) direction. It is one of the important parameters that are used to describe the visual appearance of an object. Other categories of visual appearance related to the perception of regular or diffuse reflection and transmission of light have been organized under the concept of cesia in an order system with three variables, including gloss among the involved aspects. The factors that affect gloss are the refractive index of the material, the angle of incident light and the surface topography.
Apparent gloss depends on the amount of specular reflection – light reflected from the surface in an equal amount and the symmetrical angle to the one of incoming light – in comparison with diffuse reflection – the amount of light scattered into other directions.
Theory
When light illuminates an object, it interacts with it in a number of ways:
Absorbed within it (largely responsible for colour)
Transmitted through it (dependent on the surface transparency and opacity)
Scattered from or within it (diffuse reflection, haze and transmission)
Specularly reflected from it (gloss)
Variations in surface texture directly influence the level of specular reflection. Objects with a smooth surface, i.e. highly polished or containing coatings with finely dispersed pigments, appear shiny to the eye due to a large amount of light being reflected in a specular direction whilst rough surfaces reflect no specular light as the light is scattered in other directions and therefore appears dull. The image forming qualities of these surfaces are much lower making any reflections appear blurred and distorted.
Substrate material type also influences the gloss of a surface. Non-metallic materials, i.e. plastics etc. produce a higher level of reflected light when illuminated at a greater illumination angle due to light being absorbed into the material or being diffusely scattered depending on the colour of the material. Metals do not suffer from this effect producing higher amounts of reflection at any angle.
The Fresnel formula gives the specular reflectance, , for an unpolarized light of intensity , at angle of incidence , giving the intensity of specularly reflected beam of intensity , while the refractive index of the surface specimen is .
The Fresnel equation is given as follows :
Surface roughness
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Surface roughness influences the specular reflectance levels; in the visible frequencies, the surface finish in the micrometre range is most relevant. The diagram on the right depicts the reflection at an angle on a rough surface with a characteristic roughness height variation . The path difference between rays reflected from the top and bottom of the surface bumps is:
When the wavelength of the light is , the phase difference will be:
If is small, the two beams (see Figure 1) are nearly in phase, resulting in constructive interference; therefore, the specimen surface can be considered smooth. But when , then beams are not in phase and through destructive interference, cancellation of each other will occur. Low intensity of specularly reflected light means the surface is rough and it scatters the light in other directions. If the middle phase value is taken as criterion for smooth surface, , then substitution into the equation above will produce:
This smooth surface condition is known as the Rayleigh roughness criterion.
History
The earliest studies of gloss perception are attributed to Leonard R. Ingersoll who in 1914 examined the effect of gloss on paper. By quantitatively measuring gloss using instrumentation Ingersoll based his research around the theory that light is polarised in specular reflection whereas diffusely reflected light is non-polarized. The Ingersoll "glarimeter" had a specular geometry with incident and viewing angles at 57.5°. Using this configuration gloss was measured using a contrast method which subtracted the specular component from the total reflectance using a polarizing filter.
In the 1930s work by A. H. Pfund, suggested that although specular shininess is the basic (objective) evidence of gloss, actual surface glossy appearance (subjective) relates to the contrast between specular shininess and the diffuse light of the surrounding surface area (now called "contrast gloss" or "luster").
If black and white surfaces of the same shininess are visually compared, the black surface will always appear glossier because of the greater contrast between the specular highlight and the black surroundings as compared to that with white surface and surroundings. Pfund was also the first to suggest that more than one method was needed to analyze gloss correctly.
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In 1937 R. S. Hunter, as part of his research paper on gloss, described six different visual criteria attributed to apparent gloss. The following diagrams show the relationships between an incident beam of light, I, a specularly reflected beam, S, a diffusely reflected beam, D and a near-specularly reflected beam, B.
Specular gloss – the perceived brightness and the brilliance of highlights
Defined as the ratio of the light reflected from a surface at an equal but opposite angle to that incident on the surface.
Sheen – the perceived shininess at low grazing angles
Defined as the gloss at grazing angles of incidence and viewing
Contrast gloss – the perceived brightness of specularly and diffusely reflecting areas
Defined as the ratio of the specularly reflected light to that diffusely reflected normal to the surface;
Absence of bloom – the perceived cloudiness in reflections near the specular direction
Defined as a measure of the absence of haze or a milky appearance adjacent to the specularly reflected light: haze is the inverse of absence-of-bloom
Distinctness of image gloss – identified by the distinctness of images reflected in surfaces
Defined as the sharpness of the specularly reflected light
Surface texture gloss – identified by the lack of surface texture and surface blemishes
Defined as the uniformity of the surface in terms of visible texture and defects (orange peel, scratches, inclusions etc.)
A surface can therefore appear very shiny if it has a well-defined specular reflectance at the specular angle. The perception of an image reflected in the surface can be degraded by appearing unsharp, or by appearing to be of low contrast. The former is characterised by the measurement of the distinctness-of-image and the latter by the haze or contrast gloss.
In his paper Hunter also noted the importance of three main factors in the measurement of gloss:
The amount of light reflected in the specular direction
The amount and way in which the light is spread around the specular direction
The change in specular reflection as the specular angle changes
For his research he used a glossmeter with a specular angle of 45° as did most of the first photoelectric methods of that type, later studies however by Hunter and D. B. Judd in 1939, on a larger number of painted samples, concluded that the 60 degree geometry was the best angle to use so as to provide the closest correlation to a visual observation.
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Standard gloss measurement
Standardisation in gloss measurement was led by Hunter and ASTM (American Society for Testing and Materials) who produced ASTM D523 Standard test method for specular gloss in 1939. This incorporated a method for measuring gloss at a specular angle of 60°. Later editions of the Standard (1951) included methods for measuring at 20° for evaluating high gloss finishes, developed at the DuPont Company (Horning and Morse, 1947) and 85° (matte, or low, gloss).
ASTM has a number of other gloss-related standards designed for application in specific industries including the old 45° method which is used primarily now used for glazed ceramics, polyethylene and other plastic films.
In 1937, the paper industry adopted a 75° specular-gloss method because the angle gave the best separation of coated book papers. This method was adopted in 1951 by the Technical Association of Pulp and Paper Industries as TAPPI Method T480.
In the paint industry, measurements of the specular gloss are made according to International Standard ISO 2813 (BS 3900, Part 5, UK; DIN 67530, Germany; NFT 30-064, France; AS 1580, Australia; JIS Z8741, Japan, are also equivalent). This standard is essentially the same as ASTM D523 although differently drafted.
Studies of polished metal surfaces and anodised aluminium automotive trim in the 1960s by Tingle, Potter and George led to the standardisation of gloss measurement of high gloss surfaces by goniophotometry under the designation ASTM E430. In this standard it also defined methods for the measurement of distinctness of image gloss and reflection haze.
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The Guangzhou Metro () is the rapid transit system of the city of Guangzhou in the Guangdong Province of China. It is operated by the state-owned Guangzhou Metro Corporation and was the fourth metro system to be built in mainland China, after those of Beijing, Tianjin, and Shanghai.
The earliest efforts to build an underground rapid transit system in Guangzhou date back to 1960. In the two decades that followed, the project was brought into the agenda five times but ended up abandoned each time due to financial and technical difficulties. Preparation of what would lead to today's Guangzhou Metro did not start until the 1980s, and it was not until 1993 that construction of the first line, Line 1, officially began. Line 1 opened four years later in 1997 with five stations in operation.
, Guangzhou Metro has 17 lines in operation, namely: Line 1, Line 2, Line 3, Line 4, Line 5, Line 6, Line 7, Line 8, Line 9, Line 11, Line 13, Line 14, Line 18, Line 21, Line 22, Guangfo Line, and Zhujiang New Town APM reaching both the urban core and surrounding suburbs. Guangfo Line connects Guangzhou and Foshan and is the first metro line between two cities in the country. Daily service hours start at 6:00 am and end at midnight and daily ridership averages over 7 million. Having delivered 3.029 billion rides in 2018, Guangzhou Metro is the third busiest metro system in the world and the 3rd largest in terms of length, after the metro systems of Beijing and Shanghai. Guangzhou Metro operates 320 stations and of lines.
Extensive development of the metro network has been planned for the next decade, with construction started on Line 10, Line 12, and Line 24, and extensions of Line 8, Line 13, Line 14, Line 18, as well as the extension of Line 22 to Baiyun Airport.
Some of the system's lines were designed to operate much faster than traditional metro lines, with stations far apart and faster trainsets regularly running at . Lines 18 and 22 are the fastest metro lines in China, a title previously held by Line 11 of the Shenzhen Metro.
History
Forays of the 1960s and 1970s
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Chen Yu (), Governor of Guangdong in 1957–1967, was the first to have proposed an underground metro system for Guangzhou. In the summer of 1960, he ordered a secret geological survey of groundwater levels of Guangzhou. Six holes with an accumulated depth of were drilled in the karst and alluvial plains in the city. The geological conditions of Guangzhou, despite their complexity, did not preclude the possibility of an underground metro system. Analysis of the survey data resulted in a confidential report titled Geological Survey for Guangzhou Underground Railway Project dated July 1961, the earliest one of such reports.
In 1965, Chen Yu along with Tao Zhu (), who had been the Governor of Guangdong and First Secretary of Guangdong Committee of the Chinese Communist Party, proposed in the wake of the Gulf of Tonkin incident that a tunnel is built in Guangzhou for wartime evacuations and post-war metro development. Approved by the central government, the project started in the spring of 1965. Due to its confidentiality in the context of intensification of the Vietnam War, the project adopted the obscure name of "Project Nine" (), where "Nine" was the number of strokes in "", the Chinese word for "underground".
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As envisaged by Chen Yu, the metro system of Guangzhou would consist of two lines: a north–south line that would connect Nanfang Building to Sanyuanli via Renmin Lu and Jiefang Beilu, and an east–west line that would run from Xichang to Dongshan along today's Dongfeng Lu. The two lines roughly parallelled Line 2 and Line 1 of the modern days, respectively. The east–west line was never built, while Project Nine was dedicated to the north–south line. Over ten teams of miners were recruited for a project filled with hazards and perils. Constrained by extreme scarcity of time, monetary and material resources, the ambition to build a tunnel for the metro operation was scaled back— the capability to run trolleybuses was deemed acceptable. For ¥13 million, an long tunnel was completed in 1966. The tunnel was planned to be used as an air-raid shelter and eventual metro line; however, with a cross-section merely 3 m wide and 2.85 m tall, and exposed rocks and wooden trestles scattered everywhere, it was unusable for public transit. In the two decades that followed, four attempts were made to revive and expand Project Nine, first in 1970, next in 1971, then in 1974, and last in 1979. Due to lack of funds and complex geotechnical conditions, none of these efforts materialized.
Construction of Line 1
The metro project of Guangzhou was launched for the sixth time in 1984 as the Preparation Office of Guangzhou Metro, established back in 1979 as part of the last attempt to resurrect Project Nine, was moved out of the civil air-defense system and became a subordinate body of the Construction Commission of Guangzhou, bringing Guangzhou Metro into the scope of urban infrastructure development. Before the 1980s, war preparedness was the dominant tenet of underground infrastructure projects in mainland China. The construction of Guangzhou Metro marked the first deviation from the old doctrine as traffic itself became the prime consideration of the project.
The design of the initial metro network was a collaborative effort between China and France (SYSTRA). Four tentative designs were published on 14 March 1988 edition of Guangzhou Daily. From the four designs, one was selected based on expert and mass feedback. The selected design, featuring two intersecting lines, was the baseline typology for today's Line 1 and Line 2.
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Construction of Line 1 officially commenced on 28 December 1993, although work on a trial section at Huangsha had begun in October 1992, five months before the feasibility study of the line was ratified by the State Planning Commission in March 1993. Various technologies novel to China's construction industry at the time were adopted in different sections of the project, notably including immersed tubes (Pearl River Tunnel) and tunnel boring machines (Huangsha–Martyrs' Park section). As the most massive urban infrastructure project in the history of Guangzhou, Line 1 required funding of ¥12.75 billion, all of which was raised by the local government. Use of cut-and-cover tunnels aggressively backed by then-mayor Li Ziliu necessitated the relocation of approximately 100,000 residents in 20,000 households and demolition of buildings totalling in the area and earned Li the nickname "Li the Demolisher" ().
Three and a half years after construction started, the section from Xilang to Huangsha opened for trial operation on 28 June 1997. The remaining , from Huangsha to Guangzhou East railway station, was completed eighteen months later on 28 December 1998. The entire line opened for sightseeing tours between 16 February and 2 March 1999, delivering 1.39 million rides 15 days before closing for final testing. Operation of Line 1 officially began on 28 June 1999, 34 years after the start of Project Nine in 1965.
Accelerated expansion in the 2000s
The success of Line 1 as a turnkey project acquired from Siemens with 100% imported electromechanical equipment prompted a wave of similar proposals from twelve other cities in mainland China toward the end of the 1990s. The fever for import-centric rapid transit caused the State Planning Committee to temporarily halt approval of rapid transit projects nationwide and regulate the localization rates of rolling stock suppliers. Amid tightened regulation, only Line 2 of Guangzhou Metro received the immediate green light to proceed in June 1998 on the condition that at least 60% of its electromechanical equipment must be sourced domestically.
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Construction of Line 2 started in July 1998. Rolling stock manufacturer Bombardier airlifted the first two train cars in an An-124 from Berlin to Guangzhou in November 2002 after schedule delays. The first section, from to opened on 29 December 2002; the remaining section from Xiaogang to opened on 28 June 2003. At ¥2.13 billion, the equipment cost of Line 2 was 53% lower than that of Line 1. This demonstrated the feasibility of cost reduction through procurement of domestic equipment, revealing a path to project approval to other Chinese cities and reigniting their aspirations to own a rapid transit system.
The renewed craze for rapid transit across the country soon encountered a new round of tightened control on project approval around 2003. But Guangzhou was exempted along with Beijing, Shanghai and Shenzhen. By the time Line 2 was completed, construction of Line 3, Line 4, and Guangfo Line had been underway, among which only Guangfo Line later fell to stringent regulation of approvals.
Lines in operation
Line 1
Line 1 runs from Xilang to Guangzhou East railway station, with a total length of .
Except for Kengkou and Xilang, all stations in Line 1 are underground. Its first section, from Xilang to Huangsha, opened on 28 June 1997, making Guangzhou the fourth city in mainland China to have a metro system. The full line started operation two years later on 28 June 1999. Line 1's color is yellow.
Line 2
Line 2 is a north–south line that runs from Jiahewanggang to Guangzhou South railway station. Until 21 September 2010, it ran from to Wanshengwei. Its first section, between Sanyuanli and , opened on 29 December 2002. It was extended from Xiaogang to on 28 June 2003 and further to Wanshengwei a year later. The section between Xiaogang and Wanshengwei was split off to form part of Line 8 during 22–24 September 2010, when the operation was paused. The latest extension, from to Guangzhou South railway station and from to , opened on 25 September 2010 as the whole line resumed operation. The length of the current line is . All stations in Line 2 are underground. Line 2's color is deep blue.
Line 3
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Line 3 is a Y-shaped line connecting Airport North and Tianhe Coach Terminal to Haibang. All stations in the line are underground. When the line opened on 26 December 2005, trains operated between Guangzhou East railway station and Kecun. Following completion of the Tianhe Coach Terminal–Tiyu Xilu and Kecun–Panyu Square sections, the line was rerouted on 30 December 2006 to offer transfer-free connections between Panyu Square and Tianhe Coach Terminal via Tiyu Xilu. The Guangzhou East railway station–Tiyu Xilu section became a shuttle until it was extended northwards to Airport South on 30 October 2010. Southwards, it was extended from Panyu Square to Haibang on 1 November 2024.
In official distinctions, the main route consists of the entire Airport North–Haibang section, while the Tianhe Coach Terminal–Tiyu Xilu section is a spur line. The spur line will be split off in the long term to form part of Line 10. Line 3 had been notorious for its crowding since it opened, for it ran three-car trains. That was partly relieved when all three-car trains started operating as six-car ones, connected in sets of two, on 28 April 2010. Sectional services between Tonghe to Dashi are added from 7:30 to 8:30 every workday, partly solving the capacity issues. Despite these changes, as of 2018, the line is still severely overcrowded. Line 3's color is orange.
Line 4
Line 4 is a north–south line running parallel to Line 2 along the east of the city. It is long with 24 stations. The section of the line from Huangcun to Xinzao, Feishajiao to Nansha Passenger Port are built underground, while that from Xinzao to Jinzhou is built at the elevated track. It was the first metro line in mainland China to use linear motor trains. Its first section, from Wanshengwei to Xinzao, opened on 26 December 2005. Southwards, it was extended from Xinzao to Huangge on 30 December 2006 and further to Jinzhou on 28 June 2007. Northwards, it was extended to Chebeinan on 28 December 2009. Southwards, it extended from Chebeinan to Huangcun, opened on 25 September 2010. Its latest extension, from Huangcun to Nansha Passenger Port, opened on 27 December 2017. Line 4's color is green.
Line 5
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The long Line 5 starts at Jiaokou and runs to Huangpu New Port. It entered operation on 28 December 2009 between Jiaokou and Wenchong, and on 28 December 2023 between Wenchong and Huangpu New Port. All stations in the line except Jiaokou and Tanwei are underground. Until Line 8 was split off from Line 2, it was the only line that interchanged with all other lines. Similar to Line 4, Line 5 also uses linear motor trains. Line 5's color is red.
Line 6
The first stage of Line 6, a long phase one runs from Xunfenggang to Changban with 22 stations. It began service on 28 December 2013 and contains three elevated stations along the route. Construction of a 10-station, long extension to Xiangxue from Changban is entered revenue service in 2016. The line runs four-car trains, but stations of the east extension starting with South China Botanical Garden will be constructed with a provision to accommodate six-car trains in preparation for a route split in the future. Line 6's color is maroon.
Line 7
The first phase of Line 7 began service on 28 December 2016 and ran from Guangzhou South railway station to Higher Education Mega Center South in Panyu District throughout . The phase 1 west extension opened on 1 May 2022 from Guangzhou South railway station to Meidi Dadao station. Six-car trains are used. All stations are underground. Phase 2 opened on 28 December 2023, and extends the line by and 11 stations to reach north of the Pearl River and go deep to Huangpu district, providing interchanges with Line 13 at , Line 5 at , Line 6 at , Line 21 at and the planned east extension of Line 8 at . Line 7's color is light green.
Line 8
The first section of Line 8, from Xiaogang to Wanshengwei, opened in 2002 and ran as part of Line 2 until the extension to the line was completed in September 2010. Line 8 ran from Fenghuang Xincun to Wanshengwei. The section from Changgang to Wanshengwei opened on 25 September 2010 when the split-off from Line 2 was complete. The section west of Changgang did not open until 3 November 2010 due to disputes over the environmental impact of the cooling facilities at Shayuan. The remaining section from Fenghuang Xincun to Cultural Park and Cultural Park to Jiaoxin are opened on 28 December 2019 and 26 November 2020 separately. Line 8's color is teal.
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Line 9
The long underground route is operated by six-car trains, which runs from Fei'eling to Gaozeng, serving 10 stations. The line, other than Qingtang station, went operational on 28 December 2017. Line 9 mainly serves as a link for the passengers of Huadu District and Guangzhou North railway station to the rest of the system, having only one transfer station with Line 3 at Gaozeng. After the Tianhe Coach Terminal–Tiyu Xilu spur line of Line 3 is split off to form part of Line 10, the line is expected to be connected into Line 3 using the reserved switches at Gaozeng to become a new spur line. Line 9's color is pale green.
Line 11
Line 11 is a loop-shaped line—the first in such shape—connecting and , via Guangzhou railway station, Guangzhou East railway station, , , and . The line was opened on 28 December 2024 at 14:00 local time, with trains stopping in all but the Guangzhou East and s. Line 11's color is gold.
Line 13
Opened on 28 December 2017, Line 13 is the first metro line in Guangzhou built to run eight-car trains. The currently operating first phase runs from Yuzhu to Xinsha, serving passengers of Huangpu and Xintang, Zengcheng. The eleven-station line currently has only one transfer station with Line 5 at Yuzhu. The second phase of Line 13 runs west of the current phase, which cuts through popular areas of Huangpu, Tianhe, and Liwan Districts, and is currently under construction. Line 13's color is olive.
Line 14
Two sections of Line 14 are currently in service. The Knowledge City Branch Line, a ten-station long route located mainly within Huangpu, opened on 28 December 2017. The branch line operates primarily within Huangpu between Xinhe and Zhenlong, serving the Sino-Singapore Guangzhou Knowledge City. The mainline segment to Conghua opened a year later on 28 December 2018 and runs from Jiahewanggang in Baiyun District to Dongfeng in Conghua. A southward extension to Guangzhou railway station is currently under construction. Line 14 was the first Guangzhou Metro line to run express services. Line 14's color is brown.
Line 18
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The section from to of Line 18 opened on 28 September 2021. The section is 58.3 km in length. It will be extended 3 km to . A further 39.6 km extension to is also planned. Line 18's color is blue.
Line 21
The long Line 21 runs between Tianhe Park in Tianhe and Zengcheng Square in Zengcheng with six-car trains. It has of underground tracks, of elevated tracks, and of tracks in mountain tunnels. The section from Yuancun to Tianhe Park is intended as part of Line 11 and constructed to accommodate the eight-car trains of the latter. When the construction of Line 11 is completed, this section will be operated as part of Line 11, making Tianhe Park the west end of Line 21. Express service was also provided after the inauguration of the western section (Yuancun – Zhenlongxi). Line 21's color is dark navy.
Line 22
The section from to of Line 22 opened on 31 March 2022. The section is 18.2 km in length. It will be extended 73.2 km to . Line 22's color is orange.
Guangfo Line
The Guangzhou–Foshan Section of Pearl River Delta Region Intercity Rapid Transit () is an intercity metro line that connects Guangzhou and Foshan. It is commonly known as Guangfo Metro and Guangfo Line of Guangzhou Metro. The section within Foshan also doubles as Line 1 of FMetro (Foshan Metro). The line is operated by Guangdong Guangfo Rail Transit Co., Ltd., a subsidiary co-owned by Guangzhou Metro (51%) and Foshan Metro (49%). Its first section, from Xilang to Kuiqi Lu in Foshan, started operation on 3 November 2010 with of tracks and 14 stations. Eleven of the stations are located in Foshan, while the other three are in Guangzhou. Relocation disputes at Lijiao were not resolved until October 2013 and have delayed completion of the extension from Xilang to Lijiao till December 2015. When the line is completed, it will have of tracks and 21 stations, of which of tracks and 10 stations will be located in Guangzhou. The line runs four-car trains. All its stations are underground.
Zhujiang New Town APM Line
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The Automated People Mover System of Zhujiang New Town Core District Municipal Traffic Project () is an underground automated people mover that serves the central business district of Zhujiang New Town. It is commonly known as Zhujiang New Town Automated People Mover System or the APM for short. At a length of , it connects Linhexi and Canton Tower with nine stations on the line. The operation started on 8 November 2010 with Canton Tower Station named Chigang Pagoda Station until December 2013. The stations of Haixinsha and Chigang Pagoda remained closed during the 2010 Asian Games. Chigang Pagoda Station opened on 28 November 2010, one day after the Asian Games ended; Haixinsha Station remained unopened until 24 February 2011. There is no direct platform-to-platform connection between the APM and Line 3 albeit they share the stations of Linhexi and Canton Tower. Transfer passengers need to exit and reenter with a new ticket. The APM runs two-car rubber-wheeled driverless trains.
Network expansion
Short-term planning
Long-term planning
The Guangzhou Urban Rail Transit Network Planning Scheme (2018–2035) (), which was approved by the Guangzhou Municipal Government in November 2020, shows that a total of 53 metro lines and 2,029 km are planned in Guangzhou. This round of line network planning is divided into three levels: high-speed metro, rapid metro, and regular-speed metro. Among them, there are 5 high-speed metro lines with 452 km in Guangzhou, 11 rapid metro lines with 607 km in Guangzhou, and 37 regular-speed metro lines with 970 km.
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High-speed metro lines:
: Knowledge City – Luogang – Zini (→ Foshan)
: (Zhongshan / Zhuhai →) Shiliuchong – Huachengjie (→ Qingyuan)
: Airport North – Nansha Passenger Port (→ Dongguan)
: (Foshan →) Fangcun – Xintang (→ Dongguan)
spur line: Xintang – Guangzhou Huali College (→ Huizhou)
: Guangzhou East railway station – Liangkou (→ Xinfeng)
Rapid metro lines:
: Airport North – Haiou Island
parallel express line: Pazhou – Jiaomen
: Shuixibei – Meidi Dadao
: Chaoyang – Xinsha
: Guangzhou railway station – Dongfeng
: Xintang – Lichengbei
: Tianhe Park – Guangzhou Huali College
: Guangzhou North railway station – Lijiao
: Longxi – Huangpu Passenger Port
: Taihe – Lanhe (→ Foshan)
: Xinhe – Jiangnan (→ Dongguan)
: Huangpu railway station – Huadu Square
Regular-speed metro lines:
: Xilang – Guangzhou East railway station
: Jiahewanggang – Guangzhou South railway station
: Huangcun – Nansha Passenger Port
: Jiaokou – Huangpu Passenger Port
: Xunfenggang – Guangzhou Middle School
: Jiangfu – Haibang
: Tanzhonglu – Gaozeng
: Gaotangshi – Guanggang New Town (→ Foshan)
: Guangzhou railway station – Pazhou – Guangzhou railway station
Regular-speed metro lines (continued):
: Xunfenggang – Higher Education Mega Center South
spur line: Higher Education Mega Center North – Chenbian
: Jiaomen – Nansha Passenger Port – Jiaomen
: Huangpu railway station – Nanpuxi (→ Foshan)
: Lingnan Square – Jiangnan
: Chishajiao – Xintang Dadao
: Guangzhoudadaobei – Education Park
: Dongchong Town – Nansha Wetland Park
: Nanguolu – Information Technology Park
: Ronggui Railway Station – Qingshengdong
: (Foshan →) Huangjinwei – Toubei
: Dongjing – Huadong Coach Terminal
: Fengcun – Baishantang
: Lianxidadao – Shiliuchong
: Jiahewanggang – Datian
: Shihua – Changping
spur line: Yonghe – Lihu
: Bicun – Fangshi
: Aotou – Conghua Coach Terminal
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: Nanjiao – GAC Base
Foshan : (Foshan →) Guangzhou South Railway Station
Foshan : (Foshan →) Xingyedadao
Foshan : (Foshan →) Guangzhou Railway Station
Foshan : (Foshan →) Baiyun Dongping
Foshan : (Foshan →) Longxi
Foshan : (Foshan →) Fangcun
Foshan : (Foshan →) Hedongdong
Dongguan : Huangpu Passenger Port (→ Dongguan)
Dongguan : Zengcheng Railway Station (→ Dongguan)
Dongguan : Shiqi (→ Dongguan)
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Connections to neighboring cities
The Guangzhou Metro is actively constructing connections to neighboring cities. Foshan is already connected via the Guangfo Metro with connections via Line 7 and Foshan Metro Line 2 is now opened. Dongguan city is proposing connections with Guangzhou Metro Line 13 and the Dongguan Metro. Neighboring Huizhou city proposed in 2016 that Guangzhou Metro Line 16 be extended into Longmen County, achieving the integration of Huizhou and Guangzhou. In January 2018, Huizhou's mayor Mai Jiaomeng revealed that Huizhou was studying two connections with the Guangzhou Metro with Line 16 heading to Yonghan Town, Longmen County and Line 21 extended to Mount Luofu in Boluo County. In 2018, Guangzhou is studying the feasibility of extending Line 18 south into Zhongshan and north into Qingyuan.
Guangzhou–Foshan metro connections
Fares and tickets
Fares
Fares of Guangzhou Metro currently range from ¥2 (a couple of stations) to ¥22 (the longest journeys). A journey shorter than 4 km costs ¥2; ¥1 is charged for every 4 km after 4 km, every 6 km after 12 km, and every 8 km after 24 km. Between 30 October 2010 and 30 October 2011, an additional, undiscountable ¥5 fee was charged for any journey to or from Airport South. Collection of such a fee was approved for one year in July 2010 and expired without extension. The fare for the longest possible journey to the exiting station will be charged if a journey exceeds four hours. Passengers may carry luggage below weight and size limits at no cost or a ¥2 surcharge.
Current ticket types
Single journey ticket
Single journey tickets can be bought at a kiosk at every station or at the automatic ticket vending machines. The ticket itself is a contactless radio-frequency plastic token. The user has to tap it on the sensor on the ticket barrier when entering and insert it into a slot at the exit gate where the token is reclaimed. Full base fares are charged for single journey tickets for individuals. Passengers travelling in groups of 30 or larger can enjoy a 10% discount.
Yang Cheng Tong and Lingnan Pass
Yang Cheng Tong () is a contactless smartcard which can be used on the metro and most other forms of public transport in Guangzhou.
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Yang Cheng Tong offers discounts for rides on buses and the metro. Within each month, bus and metro rides combined, a 5% discount is available for the first 15 journeys and a 40% discount for all journeys beyond.
Full-time students enrolled in primary, secondary, and vocational schools can apply for student passes, which allow them bus and metro rides at half price. Senior citizens can also obtain special passes. Half price is charged for seniors aged 60–64. Seniors aged 65 and above as well as people with major disabilities ride free of charge.
Yang Cheng Tong was rebranded in November 2010 as a type of Lingnan Pass (), a new transport card that is valid in multiple cities across the Pearl River Delta. Lingnan Pass cards issued in Guangzhou are named Lingnan Pass·Yang Cheng Tong. Existing cards were automatically upgraded and need not be replaced.
Day pass
Guangzhou Metro introduced day passes on 1 January 2013. A day pass holder can travel an unlimited number of times in the metro system during a limited period of validity starting from the first use. Two variants are currently available:
One-day pass: ¥20 each and valid for 24 hours
Three-day pass: ¥50 each and valid for 72 hours
Day passes are not rechargeable. They can be fully refunded until the first use, at which time they become nonrefundable. Used passes are not reclaimed, although they can be voluntarily recycled at drop boxes in the stations.
The passes are decorated with illustrations of the Cantonese language and cuisine to promote the local culture. The art design was favored by over 70% of those who responded to public opinion surveys compared to two other competing designs.
Discontinued ticket types
Guangzhou Metro discontinued the following ticket types in favor of Yang Cheng Tong.
Stored value ticket
Stored value tickets were very similar to Yang Cheng Tong. Stored value tickets are not on sale anymore, but they will be presented as souvenirs to VIPs at the activities of the subway company and can have a 5% discount on fares.
Monthly pass
Monthly passes were introduced on 1 November 2008 and abolished on 1 May 2010. There were three types of monthly pass:
¥55 monthly pass for 20 single journeys
¥88 monthly pass for 35 single journeys
¥115 monthly pass for 50 single journeys
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Each journey could travel from one station to any other station regardless of distance. A monthly pass was valid within a calendar month, not the one-month period from the first day it was used. Unused journeys in a month could not be rolled over to a pass for the following month.
Student pass and senior citizen pass
Both were issued by the metro company and used on metro only, allowing the holders to travel free or at half price.
Power supply
Most Guangzhou Metro lines in operation are powered by . For power transmission, lines 1, 2, 3, 7, 8, 9 and 13 as well as Guangfo Line use overhead lines, while lines 4, 5, 6, 14 and 21 use third rails. Lines 18 and 22 also use overhead wires, although at . In contrast to the heavy-rail lines, the light-rail APM runs on 600 V 50 Hz 3-phase AC supplied by third rails.
Controversies
Free rides for relatives of metro employees
Starting from 1997 (Guangzhou Metro) implemented a policy that allowed free rides for, in addition to its employees, their relatives. The policy was exposed to the public after its validity was questioned at a hearing on metro fares in December 2005. At first, it was reported that up to three lineal kins of each metro employee were allowed free access to the metro. Based on Guangzhou Metro having about 6,000 employees at the time, participants of the hearing estimated that up to 18,000 relatives of metro employees could ride free at an approximate cost of ¥13 million per year.
In response to questions on the policy raised at the hearing, Lu Guanglin, then-General Manager of Guangzhou Metro, claimed that relatives of employees with free access would volunteer as security personnel of the metro. He cited counter-terrorism when explaining that the policy was not exclusively an employee benefit but also a safety measure. Guangzhou Metro later clarified that only the spouse and at most one pre-college child under 18 of each employee were allowed free access, limiting the number of such people to about 2,000. Free rides were strictly regulated and tracked, with abuse subject to disciplinary actions. An unnamed metro employee estimated that the actual cost per year was ¥3 million rather than ¥13 million.
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Following its publicity, the policy sparked widespread criticism. A Nanfang Daily editorial criticised the policy as Guangzhou Metro exploiting public resources to its own interests. It also questioned the competence of relatives of metro employees in counter-terrorism. It further argued that if Guangzhou Metro indeed needed voluntary security personnel, it could have recruited them openly from the public. Such criticism was echoed by hearing participants as well as members of the Municipal People's Congress of Guangzhou. Guangzhou Metro officially abandoned the policy under pressure on 16 December 2005.
Ridership under-prediction
The first lines that were constructed, such as Lines 1, 2, and 8, used high capacity 6-car A-type trains in anticipation to heavy ridership. This choice later proved invaluable in the densely populated Guangzhou with all three aforementioned lines today having a peak daily usage of over 1 million passengers each. However, in the early days of operation, ridership of these lines was low. Ridership for Line 1 plateaued at – in the late 1990s and early 2000s even though it was projected to reach in 1998. The under utilization of these lines at the time allowed experts to insist using lower capacity trains on newer lines and even led to the Guangzhou government being criticized for overinflating ridership predictions to approve metro projects. Preference was given small-capacity trains and low-headway operation in the planning of later projects such as Lines 3, 5 and 6. Line 3 was to be built using smaller, lower capacity B-type rolling stock while Lines 5 and 6 was planned to use even lower capacity light metro four car L-type trains.
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Initially the trains of Line 3 would only be three cars long and planned to gradually be extended into six car trains in the long-term future. This was in line with the conservative ridership projections at the time, with the Airport Section of Line 3 predicted in 2007 to have a long term peak demand of just over 20,000 pphpd by 2034. These ideas would soon prove utterly shortsighted with Line 3 trains being plagued with extreme overcrowding with significant sections of the line over 100% capacity only a few years after opening. Line 3 was forced to adopt its final long term configuration of six-car trains and low headway operation only five years after opening. However, as of 2014, with continuing growth in passenger demand, many sections of Line 3 are still over 100% capacity even after conversion to six car trains and low headway operation. The section crossing the Pearl River between Kecun and Canton Tower stations is the most congested, reaching 136% capacity. In June 2017, the ridership of Line 3 averaged over 2 million passengers per day and on 1 March 2019 the line carried 2.54 million passengers in a single day. With the busiest section carrying over 60,000 pphpd of passenger volume in 2018.
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As the controversy surrounding Line 3 unfolded the low capacity design of Line 6, another downscaled line, drew concentrated but late criticism from local media in July 2009. Originally believed to have limited attraction to commuters, Line 6 was intended as an auxiliary line with a projected daily ridership of two years after opening and in nine years, These projections assumed the opening year of Line 6 was still 2010 and Guangzhou was less populated. Such projections were in line with ridership of the, at the time, underutilized Lines 1 and Line 2 prior to 2004. However, with the construction of Line 6 well underway using the original plan of four car L-type trains, a change to longer trains had become unrealistic as it would require modification to stations structures whose construction had been completed. An internal report of Guangzhou Metro also released in 2009 reckoned that using the same six car B-type rolling stock as Lines 3 and 7 would increase the capacity of Line 6 by 50%. Land expropriation and residence relocation would pose even greater challenges as evidenced by severe delays in the construction of the stations of Yide Lu and Shahe. In 2014, one year after opening, daily ridership on Line 6 has grown to 600,000 and continues to increase steadily, peaking at 858,000 passengers on 16 September 2016, a mere two years later. With the opening of Phase II extending the line from Changban to Xiangxue in late 2016 ridership continues to increase, averaging 850,000 passengers per day as of April 2018.
The congestion following the openings of Lines 3 and 6 made a profound impact on the planning and design of metro lines in Guangzhou. Line 5 had an urgent revision during early construction to support longer six car trains but still using a low capacity L-type design. Lines 7 was originally also planned to use the same four car light metro design as Line 6 but was redesigned and constructed to use higher capacity six car B-type trains. Before the opening of Line 6, the mayor of Guangzhou Chen Jianhua publicly admitted that planning of Line 6 lacked foresight and ridership estimates were too conservative. He predicts the line would be very crowded upon opening. He promised to ensure that future lines will be designed to use trains that are six or more cars long. Newer lines around the city center such as the under construction Line 11, Line 12 and in operation Line 13 will all use high capacity eight car A-type trains.
Quality inspection of Line 3 north extension
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Exposure of quality issue
On 11 October 2010, news broke that the concrete structures of two connecting passages in the north extension of Line 3 between Jiahewanggang and Longgui had substandard compressive strength. The quality of the two connecting passages was found to be questionable as early as August 2009. But it not was brought to light until a technician who worked for a company that inspected their quality posted scanned copies of the original inspection reports in his blog in August 2010, and the media picked up the story in October 2010.
The connecting passages were intended as connections between two metro tunnels for the maintenance crew and emergency escape corridors for passengers. Their compressive strength was designed to reach 30 MPa. However, the lowest values measured in two inspections were only 21.9 MPa and 25.5 MPa, respectively. Guangzhou Metro and Beijing Chang Cheng Bilfinger Berger Construction Engineering Co., Ltd. (BCBB), contractor of the Jiahewanggang–Longgui section, commissioned two inspection companies to perform a total of three inspections. All three inspections reported results below standard. According to the technician who disclosed the issue and another technician who participated in the first inspection, possible consequences of weaker-than-standard concrete structures included collapse of the passages, blockage of groundwater drains, and even paralysation of the metro tunnels.
Alleged fraud attempts
According to the two technicians, BCBB rejected a negative inspection report and conspired with their employer company to produce a fraudulent positive report. In response, both the inspection company and BCBB denied their involvement in any fraud attempts. Su Zhenyu, a deputy manager of the Quality and Safety Division of Guangzhou Metro, admitted the quality issue with the connecting passages but maintained the innocence of Guangzhou Metro. According to him (Guangzhou Metro) never received the original inspection reports in 2009 and was unaware of the issue until it received them on 30 September 2010. Su blamed the incident on deceit by BCBB and declared the structures safe for train operation. Su's comments were acknowledged by Guangzhou Metro.
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Reactions
According to Su (Guangzhou Metro) had launched an investigation into the incident and demanded remedial plans for fortifying the structures from the designer after its experts verified that the quality of the passage did not meet the design standard. In its official response (Guangzhou Metro) claimed that it had been monitoring the connecting passages since they were completed in August 2009 and noticed no cracks, deformation or leaks. It also commissioned a re-inspection in September 2010 and obtained results comparable to previous ones. Evaluation by the designer of the connecting passages based on these results recognised their structures as safe. Previously in 2009, the designer also evaluated one of the two connecting passages as safe upon demand of BCBB with the standard for its compressive strength at the lowest permissible value of 25 MPa.
In the wake of widespread media coverage, the Construction Commission of Guangzhou launched an investigation into the incident. The commission invited an independent expert group to inspect the connecting passages. The expert group reaffirmed that despite their quality was indeed below the design standard, the passages were safe for operation and needed not be strengthened or rebuilt. The commission also confirmed that BCBB violated regulations in concealing negative inspection reports from related parties. The cause of weaker-than-standard concrete structures was blamed by deputy mayor Su Zequn on cement being mixed manually instead of using machinery due to space limitation at the construction site.
The scheduled opening of the north extension of Line 3 on 30 October 2010 was eventually unaffected.
Universal free access in November 2010
In January 2010, then-mayor Zhang Guangning revealed to the media that the local government was considering rewarding residents with an "Asian Games gift package" in acknowledgement of their support for the Games. On 27 September 2010, contents of the gift package were officially announced. Included was universal free access to public transit on 30 workdays in November and December 2010 that would coincide with the schedules of the 2010 Asian Games and Asian Para Games in urban areas excluding the districts of Panyu, Nansha and Huadu and the cities of Zengcheng and Conghua. The measure was intended to compensate for the inconvenience caused by a temporary traffic rule that would ban cars from the streets by the parity of the last digits of their license plates during the Games.
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The free rides policy prompted unprecedented enthusiasm from local residents on 1 November 2010, the first day it went into effect. The metro system carried 7.80 million rides, doubling the figure of an average day. Ridership of the day exceeded the previous peak of 5.13 million on National Day 1 October 2010 by a significant margin and set a national record. Metro traffic remained intense in the days that followed. The daily ridership record was refreshed twice on 3 and 5 November 2010, reaching 7.844 million; total ridership amounted to 38.77 million over the entire workweek. Provisional flow control measures were put into force at all stations, but were utterly inadequate to contain traffic far beyond the design capacity of the metro system. Trains were often crammed, and stations were filled with people queuing in swarms to take a free ride. Guangzhou Metro estimated that when the Asian Games opened, daily ridership would surpass 8 million.
Five days after the free rides policy came into force, local authorities decided to rescind the free public transit offer starting from 8 November 2010 and replace it with a cash subsidy program as they deemed the enormous public response a potential security threat to the Games. Registered households and migrant households with presence in the city longer than half a year would each receive a public transit subsidy of ¥150 in cash; individuals in corporate households would each receive ¥50. Residents could claim the subsidies between 12 January and 31 March 2011. Public transit discount policies that were in effect before November 2010 remained unchanged.
Kangwang Lu sinkhole incident
Around 16:40 on 28 January 2013, in the immediate neighbourhood of the construction site of the Cultural Park Station of Line 6 on Kangwang Lu (), a sinkhole of approximately in area and in depth collapsed, consuming several houses and trees. Six collapses occurred within 40 minutes. Two more collapses occurred later at 21:45, when workers were pouring concrete into the sinkhole. Nearby roads were immediately closed for emergency engineering. The affected section of Kangwang Lu remained closed until the Spring Festival holidays and was closed for a second time on 12 February due to discovery of additional risks.
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There were no casualties in the incident because metro construction workers detected geological anomalies 20 minutes before the initial collapse and promptly evacuated the neighbourhood. The sinkhole caused disruptions to electricity, gas and water supplies and drainage pipelines. Preliminary analysis blamed the incident on inaccurate geological drawings used for underground blast operations. In total, 412 households, 103 businesses and 69 warehouses were evacuated, and 257 residents were relocated. Guangzhou Metro offered provisional compensations that amounted to ¥50,000 for each collapsed business and ¥2600 for each resident of the collapsed houses, among other compensations.
Overseas business
On February 25, 2020, the Guangzhou Metro Group and the Punjab Provincial Public Transport Authority of Pakistan signed a service contract for the operation and maintenance of the Orange Line of the Lahore Metro in Pakistan. The bid-winning consortium would undertake the operation and maintenance of the Lahore Metro Orange Line for eight years.
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In physics, the wavefront of a time-varying wave field is the set (locus) of all points having the same phase. The term is generally meaningful only for fields that, at each point, vary sinusoidally in time with a single temporal frequency (otherwise the phase is not well defined).
Wavefronts usually move with time. For waves propagating in a unidimensional medium, the wavefronts are usually single points; they are curves in a two dimensional medium, and surfaces in a three-dimensional one.
For a sinusoidal plane wave, the wavefronts are planes perpendicular to the direction of propagation, that move in that direction together with the wave. For a sinusoidal spherical wave, the wavefronts are spherical surfaces that expand with it. If the speed of propagation is different at different points of a wavefront, the shape and/or orientation of the wavefronts may change by refraction. In particular, lenses can change the shape of optical wavefronts from planar to spherical, or vice versa.
In classical physics, the diffraction phenomenon is described by the Huygens–Fresnel principle that treats each point in a propagating wavefront as a collection of individual spherical wavelets. The characteristic bending pattern is most pronounced when a wave from a coherent source (such as a laser) encounters a slit/aperture that is comparable in size to its wavelength, as shown in the inserted image. This is due to the addition, or interference, of different points on the wavefront (or, equivalently, each wavelet) that travel by paths of different lengths to the registering surface. If there are multiple, closely spaced openings (e.g., a diffraction grating), a complex pattern of varying intensity can result.
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Simple wavefronts and propagation
Optical systems can be described with Maxwell's equations, and linear propagating waves such as sound or electron beams have similar wave equations. However, given the above simplifications, Huygens' principle provides a quick method to predict the propagation of a wavefront through, for example, free space. The construction is as follows: Let every point on the wavefront be considered a new point source. By calculating the total effect from every point source, the resulting field at new points can be computed. Computational algorithms are often based on this approach. Specific cases for simple wavefronts can be computed directly. For example, a spherical wavefront will remain spherical as the energy of the wave is carried away equally in all directions. Such directions of energy flow, which are always perpendicular to the wavefront, are called rays creating multiple wavefronts.
The simplest form of a wavefront is the plane wave, where the rays are parallel to one another. The light from this type of wave is referred to as collimated light. The plane wavefront is a good model for a surface-section of a very large spherical wavefront; for instance, sunlight strikes the earth with a spherical wavefront that has a radius of about 150 million kilometers (1 AU). For many purposes, such a wavefront can be considered planar over distances of the diameter of Earth.
In an isotropic medium wavefronts travel with the same speed in all directions.
Wavefront aberrations
Methods using wavefront measurements or predictions can be considered an advanced approach to lens optics, where a single focal distance may not exist due to lens thickness or imperfections. For manufacturing reasons, a perfect lens has a spherical (or toroidal) surface shape though, theoretically, the ideal surface would be aspheric. Shortcomings such as these in an optical system cause what are called optical aberrations. The best-known aberrations include spherical aberration and coma.
However, there may be more complex sources of aberrations such as in a large telescope due to spatial variations in the index of refraction of the atmosphere. The deviation of a wavefront in an optical system from a desired perfect planar wavefront is called the wavefront aberration. Wavefront aberrations are usually described as either a sampled image or a collection of two-dimensional polynomial terms. Minimization of these aberrations is considered desirable for many applications in optical systems.
Wavefront sensor and reconstruction techniques
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A wavefront sensor is a device which measures the wavefront aberration in a coherent signal to describe the optical quality or lack thereof in an optical system. There are many applications that include adaptive optics, optical metrology and even the measurement of the aberrations in the eye itself. In this approach, a weak laser source is directed into the eye and the reflection off the retina is sampled and processed. Another application of software reconstruction of the phase is the control of telescopes through the use of adaptive optics.
Mathematical techniques like phase imaging or curvature sensing are also capable of providing wavefront estimations. These algorithms compute wavefront images from conventional brightfield images at different focal planes without the need for specialised wavefront optics. While Shack-Hartmann lenslet arrays are limited in lateral resolution to the size of the lenslet array, techniques such as these are only limited by the resolution of digital images used to compute the wavefront measurements. That said, those wavefront sensors suffer from linearity issues and so are much less robust than the original SHWFS, in term of phase measurement.
There are several types of wavefront sensors, including:
Shack–Hartmann wavefront sensor: a very common method using a Shack–Hartmann lenslet array.
Phase-shifting Schlieren technique
Wavefront curvature sensor: also called the Roddier test. It yields good correction but needs an already good system as a starting point.
Pyramid wavefront sensor
Common-path interferometer
Foucault knife-edge test
Multilateral shearing interferometer
Ronchi tester
Shearing interferometer
Although an amplitude splitting interferometer such as the Michelson interferometer could be called a wavefront sensor, the term is normally applied to instruments that do not require an unaberrated reference beam to interfere with.
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Xanthidae is a family of crabs known as gorilla crabs, mud crabs, pebble crabs or rubble crabs. Xanthid crabs are often brightly coloured and are highly poisonous, containing toxins which are not destroyed by cooking and for which no antidote is known. The toxins are similar to the tetrodotoxin and saxitoxin produced by puffer fish, and may be produced by bacteria in the genus Vibrio living in symbiosis with the crabs, mostly V. alginolyticus and V. parahaemolyticus.
Classification
Many species formerly included in the family Xanthidae have since been moved to new families. Despite this, Xanthidae is still the largest crab family in terms of species richness, contanining the following subfamilies and genera:
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Actaeinae
Actaea
Actaeodes
Actaeops †
Allactaea
Eoxanthops †
Epiactaea
Epiactaeodes
Forestiana
Gaillardiellus
Heteractaea
Lambropsis †
Lobiactaea
Meractaea
Novactaea
Odhnea
Paractaea
Paractaeopsis
Phlyctenodes †
Platyactaea
Pseudoliomera
Pseudophlyctenodes †
Rata
Serenius
Banareiinae
Banareia
Calvactaea
Pseudactaea
Trichia
Chlorodiellinae
Chlorodiella
Cyclodius
Liocarpilodes
Luniella
Pilodius
Ratha
Soliella
Sulcodius
Tweedieia
Vellodius
Cymoinae
Cymo
Etisinae
Etisus
Paraetisus
Euxanthinae
Alainodaeus
Batodaeus
Carpoporus
Cranaothus
Crosnierius
Danielea
Edwardsium
Epistocavea
Euxanthus
Gothus
Guinotellus
Hepatoporus
Hypocolpus
Jacforus
Ladomedaeus
Lipaesthesius
Lipkemedaeus
Medaeops
Medaeus
Miersiella
Monodaeus
Olenothus
Palatigum
Paramedaeus
Paraxanthodes
Pilomedaeus
Pleurocolpus
Psaumis
Rizalthus
Takedax
Visayax
Glyptoxanthinae
Glyptoxanthus
Kraussiinae
Garthasia
Kraussia
Palapedia
Liomerinae
Actiomera
Bruciana
Liomera
Lipkemera
Neoliomera
Neomeria †
Paraliomera
Polydectinae
Lybia
Polydectus
Tunebia
Xanthinae
Aldrovandiopanope
Aristotelopanope
Bottoxanthodes
Camilohelleria
Cataleptodius
Coralliope
Cycloxanthops
Demania
Epixanthops
Eurycassiope
Euryxanthops
Gaudichaudia
Guitonia
Juxtaxanthias
Lachnopodus
Leptodius
Liagore
Lioxanthodes
Macromedaeus
Marratha
Megametope
Megamia †
Metaxanthops
Metopoxantho †
Neolioxantho
Neoxanthias
Neoxanthops
Orphnoxanthus
Ovatis
Palaeoxanthops †
Paraxanthias
Paraxanthus
Pestoxanthodes
Pseudomedaeus
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Wardoxanthops
Williamstimpsonia
Xanthias
Xantho
Xanthodius
Zosiminae
Atergatis
Atergatopsis
Lophozozymus
Paratergatis
Platypodia
Platypodiella
Pulcratis
Zosimus
Zozymodes
Incertae sedis
Haydnella †
Nogarolia †
Sculptoplax †
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Desmans are aquatic insectivores of the tribe Desmanini (also considered a subfamily, Desmaninae) in the mole family, Talpidae.
This tribe consists of two living species found in Europe: the Russian desman (Desmana moschata) in European Russia, and the Pyrenean desman (Galemys pyrenaicus) in the northwest of the Iberian Peninsula and the Pyrenees. Both species are endangered, the Russian desman critically so. They have webbed paws and their front paws are not well-adapted for digging. Desmans were much more diverse and widespread during the Miocene, with two genera, Gaillardia and Magnatalpa, being present in North America. Both living species are thought to have derived from the fossil genus Archaeodesmana.
Species
Genus Desmana
Russian desman (D. moschata)
†Desmana kowalskae
†Desmana nehringi
†Desmana inflata
†Desmana thermalis
†Desmana marci
Genus Galemys
Pyrenean desman (G. pyrenaicus)
Genus †Asthenoscapter Miocene, Europe
Genus †Archaeodesmana Miocene-Pliocene, Europe
Genus †Desmanella Miocene, Europe
Genus †Gaillardia Miocene, North America
Genus †Mygalinia Late Miocene, Hungary
Genus †Magnatalpa Miocene-Pliocene, North America
Genus †Ruemkelia
Gallery
In the media
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Oarfish are large and extremely long pelagic lampriform fish belonging to the small family Regalecidae. Found in areas spanning from temperate ocean zones to tropical ones, yet rarely seen, the oarfish family contains three species in two genera. One of these, the giant oarfish (Regalecus glesne), is the longest bony fish alive, growing up to about in length.
The common name oarfish is thought to allude either to their highly compressed and elongated bodies, or to the now discredited belief that the fish "row" themselves through the water with their pelvic fins. The family name Regalecidae is derived from the Latin regalis, meaning "royal". Although the larger species are considered game fish and are fished commercially to a minor extent, oarfish are rarely caught alive; their flesh is not well regarded for eating due to its gelatinous consistency.
Their rarity and large size, and their habit of lingering at the surface when sick or dying, make oarfish a probable source of sea serpent tales. Their beachings after storms have gained them a reputation as harbingers of doom, a folk belief reinforced by the numerous beachings before the disastrous 2011 Tōhoku earthquake and tsunami.
Description
The dorsal fin originates from above the (relatively large) eyes and runs the entire length of the fish. Of the approximately 400 dorsal fin rays, the first 10 to 13 are elongated to varying degrees, forming a trailing crest embellished with reddish spots and flaps of skin at the ray tips. The pelvic fins are similarly elongated and adorned, reduced to one to five rays each. The pectoral fins are greatly reduced and situated low on the body. The anal fin is completely absent and the caudal fin may be reduced or absent as well, with the body tapering to a fine point. All fins lack true spines. At least one account, from researchers in New Zealand, described the oarfish as giving off "electric shocks" when touched.
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As in other members of its order, the mouth can be protruded. The body has no scales. In the streamer fish (Agrostichthys parkeri), the skin is clad with hard tubercles; in Regalecus russelii, there are tubercules along the midline of the belly.
All species lack swim bladders, the number of gill rakers is variable, but R. russellii has more than R. glesne. Oarfish are silver in coloration; the body is marked with small dark spots.
The giant oarfish is by far the largest member of the family, at a length of —with unconfirmed reports of specimens and in length and in weight. The streamer fish reaches in length, while the largest recorded specimen of Regalecus russelii was .
Oarfish frequently practise autotomy, self-amputating the tail, presumably as an anti-predator adaptation. All captured R. russellii over 1.5 m long have autotomized tails; it is thought that they may autotomize their tails repeatedly. The break can occur near the tip of the tail so that only a part of the caudal fin is lost, or it may involve a few caudal vertebrae; in extreme cases the entire tail is lost. The wound heals but the tail does not regenerate.
Hyperossified bones have been documented in several oarfish washed up on the coast of California. These bony rays run along the entire dorsal length of the body. Their function is both to provide structural support to the spine during undulations (tail movement used for locomotion), and to prevent stress fractures that could occur from strong movement. Unlike many deep-sea fish, oarfish have no swim bladders for maintaining depth in the water column. It is likely that this forces more frequent tail undulations as the main mode of depth regulation in oarfish.
Evolution
Phylogeny
Through the analysis of the mitochondrial genome of Regalecus glesne, the phylogenetic placement of the giant oarfish was further verified. Oarfish are Lampriformes, so placed due to their morphology. Analysis of the mitochondrial genome of an R. glesne specimen clusters the species with Trachipterus trachypterus and Zu cristatus, two other Lampriformes.
Taxonomy
Oarfish were first described in 1772. Three extant species in two extant genera are described:
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Giant Oarfish (Regalecus glesne)
Russell's Oarfish (Regalecus russelii)
Streamerfish (Agrostichthys parkeri)
Environment and distribution
The oarfish inhabits the epipelagic to mesopelagic ocean layers, ranging from 250 meters (660 ft) to 1,000 meters (3,300 ft) and is rarely seen on the surface. A few have been found still barely alive, but usually if one floats to the surface, it dies due to depressurisation. At the depths the oarfish live, there are few or no currents. As a result, they build little muscle mass and they cannot survive in shallower turbulent water.
The members of the family have a worldwide range, with tropical, subtropical, and warm temperate distributions. The oarfish typically reside in the mesopelagic area of the sea. However, human encounters with live oarfish are rare, and distribution information is collated from records of oarfish caught or washed ashore.
Ecology and life history
Behaviour
Rare encounters with divers and accidental catches have supplied what little is known of oarfish ethology (behavior) and ecology. In 2001, an oarfish was filmed alive in the wild. The fish was spotted by a group of U.S. Navy personnel during the inspection of a buoy in the Bahamas. The oarfish was observed to propel itself by an amiiform mode of swimming; that is, rhythmically undulating the dorsal fin while keeping the body itself straight. Perhaps indicating a feeding posture, oarfish have been observed swimming in a vertical orientation. In this posture, the downstreaming light would silhouette the oarfishes' prey, making them easier to spot.
An oarfish measuring and was caught in February 2003 using a fishing rod baited with squid at Skinningrove, United Kingdom.
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In July 2008, scientists for the first time captured footage of an oarfish swimming in its natural habitat in the mesopelagic zone in the Gulf of Mexico. The fish was estimated to be between in length. Five observations of apparently healthy oarfish Regalecus glesne by remotely operated vehicles were reported from the northern Gulf of Mexico between 2008 and 2011 at depths within the epipelagic and mesopelagic zones. These observations include the deepest verified record of R. glesne (). In the 2011 sighting, an oarfish has been observed to switch from swimming with a vertical posture to swimming laterally, using lateral undulations of its entire body. Oarfish were found to have late or slow flight responses towards approaching remotely operated vehicles, supporting the hypothesis that they have few natural predators.
From December 2009 to March 2010, unusual numbers of the slender oarfish Regalecus russelii appeared in the waters and on the beaches of Japan.
In 2016, Animal Planet aired an episode of the television series River Monsters named "Deep Sea Demon" in which Jeremy Wade was filmed with a live oarfish. The oarfish at this location seemed to be using a buoy anchor chain as a guide to ascend to the surface. On his second diving attempt, he filmed two live oarfish as they came relatively close to the surface. Wade was able to touch one of the oarfish with his hand.
In January 2019 two oarfish were found alive in the nets of fishermen on the Japanese island of Okinawa.
Feeding ecology
Oarfish feed primarily on zooplankton, selectively straining tiny euphausiids, shrimp, and other crustaceans from the water. Small fish, jellyfish, and squid are also taken. It has been observed that oarfish eat by suctioning prey such as plankton blooms while in the water.
Reproduction and life history
The oceanodromous Regalecus glesne is recorded as spawning off Mexico from July to December; all species are presumed to not guard their eggs, and release brightly coloured, buoyant eggs, up to across, which are incorporated into the zooplankton. Based on their reproductive morphology, oarfish are thought to batch spawn. Within each breeding season that may last one or two months, individuals spawn once or multiple times in discrete spawning events before their gonads enter a long, regressive stage of reproductive development.
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The eggs hatch after about three weeks into highly active larvae that feed on other zooplankton. The larvae have little resemblance to the adults, with long dorsal and pelvic fins and extensible mouths. Larvae and juveniles have been observed drifting just below the surface. In contrast, adult oarfish are rarely seen at the surface when not sick or injured. It is probable that the fishes go deeper as they mature.
From January to February 2019, researchers tested and recorded the first successful instance of artificial insemination and hatching of Regalecus russellii using gonads from two washed-up specimens. Compared to adults, the body structure of newly hatched oarfish larvae look more compressed. The larvae often swam using mainly their pectoral fins, facing downward, with their mouths constantly open. The larvae were invertebrates but had bones in their head area, as well as fins. They died of starvation four days after they hatched.
Female R. russelii have bifurcated ovaries with a cavity through which the eggs pass before they are laid. The testes of male oarfish in the coelomic cavity near the digestive tract. There are two separate, disconnected testes, the left one being longer than the one on the right. A single female can produce hundreds of thousands, to millions of eggs. The eggs are laid in the water column, and they float freely in the water.
Predators and parasites
A 2015 study suggested that the shortfin mako shark and the sperm whale could both be predators of the oarfish, based on patterns of parasite transmission and analysis of oarfish viscera.
In folklore
The slender oarfish, (竜宮の使い "Ryūgū-No-Tsukai"), known in Japanese folklore as the 'Messenger from the Sea God's Palace', is said to portend earthquakes. The oarfish has been nicknamed the "doomsday fish" because, historically, appearances of the fish were linked with subsequent natural disasters, namely earthquakes or tsunamis. After the 2011 Tōhoku earthquake and tsunami which killed over 20,000 people, many in Japan pointed to the 20 oarfish washed up on the country's beaches in 2009 and 2010 in line with this reputation as a harbinger of doom.
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A lobster trap or lobster pot is a portable trap that traps lobsters or crayfish and is used in lobster fishing. In Scotland (chiefly in the north), the word creel was used to refer to a device used to catch lobsters and other crustaceans. A lobster trap can hold several lobsters. Lobster traps can be constructed of wire and wood, metal and netting, or rigid plastic. An opening permits the lobster to enter a tunnel of netting or other one-way device. Pots are sometimes constructed in two parts, called the "chamber" or "kitchen", where there is bait, and exits into the "parlor", which prevents escape. Lobster pots are usually dropped to the sea floor, one or more at a time, sometimes up to 40 or more, and are marked by a buoy so they can be picked up later.
Description
The trap can consist of a wood frame surrounded by mesh. The majority of the newer traps found in the Northeast of the US and the Canadian Maritimes consist of a plastic-coated metal frame. A piece of bait, often fish or chum, is placed inside the trap, and the traps are dropped onto the sea floor. A long rope is attached to each trap, at the end of which is a plastic or styrofoam buoy that bears the owner's license number. The entrances to the traps are designed to be one-way entrances only. The traps are checked every other day by the fisherman and rebaited if necessary. One study indicated that lobster traps are very inefficient and allow almost all lobsters to escape. Automatic rebaiting improves efficiency.
History
The lobster trap was invented in 1808 by Ebenezer Thorndike of Swampscott, Massachusetts. By 1810, the wooden lath trap is said to have originated in Cape Cod, Massachusetts. New England fishermen in the United States used it for years before American companies introduced it to the Canadian fishery through their Atlantic coast canneries.
An 1899 report by the United States Fish Commission on the Lobster Fishery Of Maine, described the local "lath pots" used by Maine lobster fishers:
Safety
Lobster fishermen who become entangled in the trap line are at risk of drowning if they are pulled overboard. Best practices have been developed to prevent and reduce entanglement and to facilitate getting fishermen who have fallen overboard back onto their vessels.
Rope-less lobster traps
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As whales can get entangled in ropes, there is currently research going on into the development of rope-less lobster traps. Some designs have already been developed.
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GDK (GIMP Drawing Kit) is a library that acts as a wrapper around the low-level functions provided by the underlying windowing and graphics systems. GDK lies between the display server and the GTK library, handling basic rendering such as drawing primitives, raster graphics (bitmaps), cursors, fonts, as well as window events and drag-and-drop functionality.
Like GTK Scene Graph Kit (GSK), GDK is part of GTK and licensed under the GNU Lesser General Public License (LGPL).
Software architecture
GTK is implemented on top of an abstraction layer called GDK, freeing GTK from low-level concerns like input gathering, Drag and drop and pixel format conversion. GDK is an intermediate layer which separates GTK from the details of the windowing system.
GDK is an important part of GTK's portability. Since low-level cross-platform functionality is already provided by GLib, all that is needed to make GTK run on other platforms is to port GDK to the underlying operating system's graphics layer. Hence, the GDK ports to the Windows API and Quartz are what enable GTK applications to run on Windows and macOS, respectively.
Starting with GTK+ 2.8, GDK supports Cairo which should be used with GTK+ 3 instead of GDK's drawing functions.
GDK is an intermediate layer which isolates GTK from the details of the windowing system. GDK is a thin wrapper around Xlib. The X Window System comes with a low-level library called Xlib. Almost every function in GDK is a very thin wrapper around a corresponding Xlib function; but some of the complexity (and functionality) of Xlib is hidden, to simplify programming and to make GDK easier to port to other windowing systems, such as Wayland or Microsoft Windows. The concealed Xlib functionality will rarely be of interest to application programmers; for example, many features used solely by window managers are not exposed in GDK.
GDK lets you do low level stuff, like e.g. "blit this pixmap to the screen".
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GDK provides a layer that is much more portable than say the X protocol, without sacrificing any of the low-level accessibility that systems such as X provide. The true power of this abstraction is that if you choose to use it rather than say, X, your software will automatically render on the Linux Framebuffer and Windows.
Having OpenGL (or OpenGL ES) support in GDK, facilitates a slightly better control of the graphics pipeline; OpenGL is well suited for compositing textured data but totally unsuited for drawing.
GdkFrameClock
GdkFrameClock was added in GTK 3.8
While GTK applications remain mainloop driven (cf. Glib event loop), meaning the application is idle inside this main loop most of the time and just waits for something to happen and then calls the appropriate subroutine when it does, GdkFrameClock adds an additional mechanism, that gives a "pulse" to the application. It tells the application when to update and repaint a window. The beat rate can be synchronized with the monitor refresh rate.
GTK Scene Graph Kit
In its history GDK contained and linked with a couple of different Canvases.
https://wiki.gnome.org/Attic/ProjectRidley/CanvasOverview
https://wiki.gnome.org/Attic/ProjectRidley/CanvasOverview/Canvases
https://wiki.gnome.org/Projects/GooCanvas
Developers were also considering new directions for the library, including removing deprecated API components and adding an integrated scene graph (canvas) system, similar to the Clutter graphics library, effectively integrating GTK with OpenGL and Vulkan.
GTK Scene Graph Kit (GSK)
GTK+ Scene Graph Kit (GSK) was released as part of GTK+ 3.90 in March 2017. It is the scene graph and rendering API for GTK. GSK has not been further integrated with GDK (which is also part of GTK) but is kept in its own directory.
Windowing systems
GDK contains back-ends to a couple of windowing systems, namely to the X11 and Wayland protocols, to Quartz and GDI,
and even to the Hypertext Transfer Protocol (HTTP) engine Broadway.
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With the release of GNOME 3.16 in March 2015, GDK obtained an experimental back-end for the Mir display server protocol. The Mir display server protocol is a product by Canonical for their Ubuntu distribution of Linux, which they intend to compete with the Wayland display server protocol; so far, it is implemented only in Ubuntu.
At present, no back-end exists for KMS.
To start an application and force this instance of it to use a certain windowing system, you specify the variable GDK_BACKEND:
GDK_BACKEND=wayland gnome-calculator
GDK_BACKEND=wayland CLUTTER_BACKEND=wayland cheese
gdk-pixbuf
gdk-pixbuf is a toolkit for image loading and pixel buffer manipulation. The library provides image loading and saving facilities, fast scaling and compositing of pixbufs, simple animation loading (i.e. animated GIFs), and rendering the libart image buffer to a GdkDrawable instance.
gdk-pixbuf has a fairly large API.
The fundamental structure in the gdk-pixbuf library is GdkPixbuf, a private, opaque data structure that mirrors many of the same concepts that ArtPixBuf supports. In fact, most of GdkPixbuf's private data fields have the same names and data types as the corresponding ones in ArtPixBuf. This similarity dates back to the earlier days when gdk-pixbuf was a wrapper around libart. Since that time, the libart dependency has been stripped out, and gdk-pixbuf was merged into the GTK+ 2.0 code base. As such, gdk-pixbuf's days as a standalone library are limited to the GNOME 1 release.
With the release of GTK+ 2.22 on 2010-09-23, gdk-pixbuf has been turned back into a standalone library, after being shipped as part of GTK+ since gtk+ 2.0. This was done in preparation for the transition to GTK+ 3.
https://git.gnome.org/browse/gdk-pixbuf/
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The first stand-alone release was 2.22 on 2010-Sep-21, its development started with 2.21.3 on 2010-06-23.
History
GDK was originally developed on the X Window System for the GIMP raster graphics editor.
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Sodium acetate, CH3COONa, also abbreviated NaOAc, is the sodium salt of acetic acid. This salt is colorless deliquescent, and hygroscopic.
Applications
Biotechnological
Sodium acetate is used as the carbon source for culturing bacteria. Sodium acetate can also be useful for increasing yields of DNA isolation by ethanol precipitation.
Industrial
Sodium acetate is used in the textile industry to neutralize sulfuric acid waste streams and also as a photoresist while using aniline dyes. It is also a pickling agent in chrome tanning and helps to impede vulcanization of chloroprene in synthetic rubber production. It is also used to reduce static electricity during production of disposable cotton pads.
Concrete longevity
Sodium acetate is used to mitigate water damage to concrete by acting as a concrete sealant, while also being environmentally benign and cheaper than the commonly used epoxy alternative for sealing concrete against water permeation.
Food
Sodium acetate (anhydrous) is widely used as a shelf-life extending agent and pH-control agent. It is safe to eat at low concentration.
Buffer solution
A solution of sodium acetate (a basic salt of acetic acid) and acetic acid can act as a buffer to keep a relatively constant pH level. This is useful especially in biochemical applications where reactions are pH-dependent in a mildly acidic range (pH 4–6).
Heating pad
Sodium acetate is also used in heating pads, hand warmers, and hot ice. A supersaturated solution of sodium acetate in water is supplied with a device to initiate crystallization, a process that releases substantial heat.
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Sodium acetate trihydrate crystals melt at , and the liquid sodium acetate dissolves in the released water of crystallization. When heated past the melting point and subsequently allowed to cool, the aqueous solution becomes supersaturated. This solution is capable of cooling to room temperature without forming crystals. By pressing on a metal disc within the heating pad, a nucleation center is formed, causing the solution to crystallize back into solid sodium acetate trihydrate. The process of crystallization is exothermic. The latent heat of fusion is about 264–289 kJ/kg. Unlike some types of heat packs, such as those dependent upon irreversible chemical reactions, a sodium acetate heat pack can be easily reused by immersing the pack in boiling water for a few minutes, until the crystals are completely dissolved, and allowing the pack to slowly cool to room temperature.
Preparation
For laboratory use, sodium acetate is inexpensive and usually purchased instead of being synthesized. It is sometimes produced in a laboratory experiment by the reaction of acetic acid, commonly in the 5–18% solution known as vinegar, with sodium carbonate ("washing soda"), sodium bicarbonate ("baking soda"), or sodium hydroxide ("lye", or "caustic soda"). Any of these reactions produce sodium acetate and water. When a sodium and carbonate ion-containing compound is used as the reactant, the carbonate anion from sodium bicarbonate or carbonate, reacts with the hydrogen from the carboxyl group (-COOH) in acetic acid, forming carbonic acid. Carbonic acid readily decomposes under normal conditions into gaseous carbon dioxide and water. This is the reaction taking place in the well-known "volcano" that occurs when the household products, baking soda and vinegar, are combined.
CH3COOH + NaHCO3 → CH3COONa +
→ +
Industrially, sodium acetate trihydrate is prepared by reacting acetic acid with sodium hydroxide using water as the solvent.
CH3COOH + NaOH → CH3COONa + H2O.
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To manufacture anhydrous sodium acetate industrially, the Niacet Process is used. Sodium metal ingots are extruded through a die to form a ribbon of sodium metal, usually under an inert gas atmosphere such as N2 then immersed in anhydrous acetic acid.
2 CH3COOH + 2 Na →2 CH3COONa + H2.
The hydrogen gas is normally a valuable byproduct.
Structure
The crystal structure of anhydrous sodium acetate has been described as alternating sodium-carboxylate and methyl group layers. Sodium acetate trihydrate's structure consists of distorted octahedral coordination at sodium. Adjacent octahedra share edges to form one-dimensional chains. Hydrogen bonding in two dimensions between acetate ions and water of hydration links the chains into a three-dimensional network.
Reactions
Sodium acetate can be used to form an ester with an alkyl halide such as bromoethane:
CH3COONa + BrCH2CH3 → CH3COOCH2CH3 + NaBr
Sodium acetate undergoes decarboxylation to form methane (CH4) under forcing conditions (pyrolysis in the presence of sodium hydroxide):
CH3COONa + NaOH → CH4 + Na2CO3
Calcium oxide is the typical catalyst used for this reaction.
Cesium salts also catalyze this reaction.
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Agroforestry (also known as agro-sylviculture or forest farming) is a land use management system that integrates trees with crops or pasture. It combines agricultural and forestry technologies. As a polyculture system, an agroforestry system can produce timber and wood products, fruits, nuts, other edible plant products, edible mushrooms, medicinal plants, ornamental plants, animals and animal products, and other products from both domesticated and wild species.
Agroforestry can be practiced for economic, environmental, and social benefits, and can be part of sustainable agriculture. Apart from production, benefits from agroforestry include improved farm productivity, healthier environments, reduction of risk for farmers, beauty and aesthetics, increased farm profits, reduced soil erosion, creating wildlife habitat, less pollution, managing animal waste, increased biodiversity, improved soil structure, and carbon sequestration.
Agroforestry practices are especially prevalent in the tropics, especially in subsistence smallholdings areas, with particular importance in sub-Saharan Africa. Due to its multiple benefits, for instance in nutrient cycle benefits and potential for mitigating droughts, it has been adopted in the USA and Europe.
Definition
At its most basic, agroforestry is any of various polyculture systems that intentionally integrate trees with crops or pasture on the same land. An agroforestry system is intensively managed to optimize helpful interactions between the plants and animals included, and “uses the forest as a model for design."
Agroforestry shares principles with polyculture practices such as intercropping, but can also involve much more complex multi-strata agroforests containing hundreds of species. Agroforestry can also utilise nitrogen-fixing plants such as legumes to restore soil nitrogen fertility. The nitrogen-fixing plants can be planted either sequentially or simultaneously.
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History and scientific study
The term “agroforestry” was coined in 1973 by Canadian forester John Bene, but the concept includes agricultural practices that have existed for millennia.
Scientific agroforestry began in the 20th century with ethnobotanical studies carried out by anthropologists. However, indigenous communities that have lived in close relationships with forest ecosystems have practiced agroforestry informally for centuries. For example, Indigenous peoples of California periodically burned oak and other habitats to maintain a ‘pyrodiversity collecting model,’ which allowed for improved tree health and habitat conditions. Likewise Native Americans in the eastern United States extensively altered their environment and managed land as a “mosaic” of woodland areas, orchards, and forest gardens.
Agroforestry in the tropics is ancient and widespread throughout various tropical areas of the world, notably in the form of "tropical home gardens." Some “tropical home garden” plots have been continuously cultivated for centuries. A “home garden” in Central America could contain 25 different species of trees and food crops on just one-tenth of an acre. "Tropical home gardens" are traditional systems developed over time by growers without formalized research or institutional support, and are characterized by a high complexity and diversity of useful plants, with a canopy of tree and palm species that produce food, fuel, and shade, a mid-story of shrubs for fruit or spices, and an understory of root vegetables, medicinal herbs, beans, ornamental plants, and other non-woody crops.
In 1929, J. Russel Smith published Tree Crops: A Permanent Agriculture, in which he argued that American agriculture should be changed two ways: by using non-arable land for tree agriculture, and by using tree-produced crops to replace the grain inputs in the diets of livestock. Smith wrote that the honey locust tree, a legume that produced pods that could be used as nutritious livestock feed, had great potential as a crop. The book's subtitle later led to the coining of the term permaculture.
The most studied agroforestry practices involve a simple interaction between two components, such as simple configurations of hedges or trees integrated with a single crop. There is significant variation in agroforestry systems and the benefits they have. Agroforestry as understood by modern science is derived from traditional indigenous and local practices, developed by living in close association with ecosystems for many generations.
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Benefits
Benefits include increasing farm productivity and profitability, reduced soil erosion, creating wildlife habitat, managing animal waste, increased biodiversity, improved soil structure, and carbon sequestration.
Agroforestry systems can provide advantages over conventional agricultural and forest production methods. They can offer increased productivity; social, economic and environmental benefits, as well as greater diversity in the ecological goods and services provided. These benefits are conditional on good farm management. This includes choosing the right trees, as well as pruning them regularly etc.
Biodiversity
Biodiversity in agroforestry systems is typically higher than in conventional agricultural systems. Two or more interacting plant species in a given area create a more complex habitat supporting a wider variety of fauna.
Agroforestry is important for biodiversity for different reasons. It provides a more diverse habitat than a conventional agricultural system in which the tree component creates ecological niches for a wide range of organisms both above and below ground. The life cycles and food chains associated with this diversification initiate an agroecological succession that creates functional agroecosystems that confer sustainability. Tropical bat and bird diversity, for instance, can be comparable to the diversity in natural forests. Although agroforestry systems do not provide as many floristic species as forests and do not show the same canopy height, they do provide food and nesting possibilities. A further contribution to biodiversity is that the germplasm of sensitive species can be preserved. As agroforests have no natural clear areas, habitats are more uniform. Furthermore, agroforests can serve as corridors between habitats. Agroforestry can help conserve biodiversity, positively influencing other ecosystem services.
Soil and plant growth
Depleted soil can be protected from soil erosion by groundcover plants such as naturally growing grasses in agroforestry systems. These help to stabilise the soil as they increase cover compared to short-cycle cropping systems. Soil cover is a crucial factor in preventing erosion. Cleaner water through reduced nutrient and soil surface runoff can be a further advantage of agroforestry. Trees can help reduce water runoff by decreasing water flow and evaporation and thereby allowing for increased soil infiltration. Compared to row-cropped fields nutrient uptake can be higher and reduce nutrient loss into streams.
Further advantages concerning plant growth:
Bioremediation
Drought tolerance
Increased crop stability
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Sustainability
Agroforestry systems can provide ecosystem services which can contribute to sustainable agriculture in the following ways:
Diversification of agricultural products, such as fuelwood, medicinal plants, and multiple crops, increases income security
Increased food security and nutrition by restored soil fertility, crop diversity and resilience to weather shocks for food crops
Land restoration through reducing soil erosion and regulating water availability
Multifunctional site use, e.g., crop production and animal grazing
Reduced deforestation and pressure on woodlands by providing farm-grown fuelwood
Possibility of reduced chemicals inputs, e.g. due to improved use of fertilizer, increased resilience against pests, and increased ground cover which reduces weeds
Growing space for medicinal plants e.g., in situations where people have limited access to mainstream medicines
According to the United Nations Food and Agriculture Organization (FAO)'s The State of the World’s Forests 2020, adopting agroforestry and sustainable production practices, restoring the productivity of degraded agricultural lands, embracing healthier diets and reducing food loss and waste are all actions that urgently need to be scaled up. Agribusinesses must meet their commitments to deforestation-free commodity chains and companies that have not made zero-deforestation commitments should do so.
Other environmental goals
Carbon sequestration is an important ecosystem service. Agroforestry practices can increase carbon stocks in soil and woody biomass. Trees in agroforestry systems, like in new forests, can recapture some of the carbon that was lost by cutting existing forests. They also provide additional food and products. The rotation age and the use of the resulting products are important factors controlling the amount of carbon sequestered. Agroforests can reduce pressure on primary forests by providing forest products.
Adaptation to climate change
Agroforestry can significantly contribute to climate change mitigation along with adaptation benefits. A case study in Kenya found that the adoption of agroforestry drove carbon storage and increased livelihoods simultaneously among small-scale farmers. In this case, maintaining the diversity of tree species, especially land use and farm size are important factors.
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Poor smallholder farmers have turned to agroforestry as a means to adapt to climate change. A study from the CGIAR research program on Climate Change, Agriculture and Food Security found from a survey of over 700 households in East Africa that at least 50% of those households had begun planting trees in a change from earlier practices. The trees were planted with fruit, tea, coffee, oil, fodder and medicinal products in addition to their usual harvest. Agroforestry was one of the most widespread adaptation strategies, along with the use of improved crop varieties and intercropping.
Tropical
Trees in agroforestry systems can produce wood, fruits, nuts, and other useful products. Agroforestry practices are most prevalent in the tropics, especially in subsistence smallholdings areas such as sub-Saharan Africa.
Research with the leguminous tree Faidherbia albida in Zambia showed maximum maize yields of 4.0 tonnes per hectare using fertilizer and inter-cropped with the trees at densities of 25 to 100 trees per hectare, compared to average maize yields in Zimbabwe of 1.1 tonnes per hectare.
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Hillside systems
A well-studied example of an agroforestry hillside system is the Quesungual Slash and Mulch Agroforestry System in Lempira Department, Honduras. This region was historically used for slash-and-burn subsistence agriculture. Due to heavy seasonal floods, the exposed soil was washed away, leaving infertile barren soil exposed to the dry season. Farmed hillside sites had to be abandoned after a few years and new forest was burned. The UN's FAO helped introduce a system incorporating local knowledge consisting of the following steps:
Thin and prune Hillside secondary forest, leaving individual beneficial trees, especially nitrogen-fixing trees. They help reduce soil erosion, maintain soil moisture, provide shade and provide an input of nitrogen-rich organic matter in the form of litter.
Plant maize in rows. This is a traditional local crop.
Harvest from the dried plant and plant beans. The maize stalks provide an ideal structure for the climbing bean plants. Bean is a nitrogen-fixing plant and therefore helps introduce more nitrogen.
Pumpkins can be planted during this time. The plant's large leaves and horizontal growth provide additional shade and moisture retention. It does not compete with the beans for sunlight since the latter grow vertically on the stalks.
Every few seasons, rotate the crop by grazing cattle, allowing grass to grow and adding soil organic matter and nutrients (manure). The cattle prevent total reforestation by grazing around the trees.
Repeat.
Kuojtakiloyan
The kuojtakiloyan of Mexico is a jungle-landscaped polyculture that grows avocadoes, sweet potatoes, cinnamon, black cherries, , citrus fruits, gourds, macadamia, mangoes, bananas and sapotes.
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Kuojtakiloyan is a Masehual term that means 'useful forest' or 'forest that produces', and it is an agroforestry system developed and maintained by indigenous peoples of the Sierra Norte of the State of Puebla, Mexico. It has become a vital fountain of resources (food, medicinal herbs, fuels, floriculture, etc.) for the local population, but it is also a respectful transformation of the environment, with its biodiversity and nature conservation. The kuojtakiloyan comes directly from the ancestral Nahua and Totonaku knowledge of their natural environment. Despite its unawareness among the mainstream Mexican population, many agronomic experts in the world point it out as a successful case of sustainable agroforestry practiced communally.
The kuojtakiloyan is a jungle-landscaped polyculture in which avocados, sweet potatoes, cinnamon, black cherries, chalahuits, citrus fruits, gourds, macadamia, mangoes, bananas and sapotes are grown. In addition, a wide variety of harvested wild edible mushrooms and herbs (quelites). The jonote is planted because its fiber is useful in basketry, and also bamboo, which is fast growing, to build cabins and other structures. Concurrently to kuojtakiloyan, shade coffee is grown (café bajo sombra in Spanish; kafentaj in Masehual). Shade is essential to obtain high quality coffee. The local population has favored the proliferation of the stingless bee (pisilnekemej) by including the plants that it pollinates. From bees, they get honey, pollen, wax and propolis.
Shade crops
With shade applications, crops are purposely raised under tree canopies within the shady environment. The understory crops are shade tolerant or the overstory trees have fairly open canopies. A conspicuous example is shade-grown coffee. This practice reduces weeding costs and improves coffee quality and taste.
Crop-over-tree systems
Crop-over-tree systems employ woody perennials in the role of a cover crop. For this, small shrubs or trees pruned to near ground level are utilized. The purpose is to increase in-soil nutrients and/or to reduce soil erosion.
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Intercropping and alley cropping
With alley cropping, crop strips alternate with rows of closely spaced tree or hedge species. Normally, the trees are pruned before planting the crop. The cut leafy material - for example, from Alchornea cordifolia and Acioa barteri - is spread over the crop area to provide nutrients. In addition to nutrients, the hedges serve as windbreaks and reduce erosion.
In tropical areas of North and South America, various species of Inga such as I. edulis and I. oerstediana have been used for alley cropping.
Intercropping is advantageous in Africa, particularly in relation to improving maize yields in the sub-Saharan region. Use relies upon the nitrogen-fixing tree species Sesbania sesban, Tephrosia vogelii, Gliricidia sepium and Faidherbia albida. In one example, a ten-year experiment in Malawi showed that, by using the fertilizer tree Gliricidia (G. sepium) on land on which no mineral fertilizer was applied, maize/corn yields averaged as compared to in plots without fertilizer trees or mineral fertilizers.
Weed control is inherent to alley cropping, by providing mulch and shade.
Syntropic systems
Syntropic farming, syntropic agriculture or syntropic agroforestry is an organic, permaculture agroforestry system developed by Ernst Götsch in Brazil. Sometimes this system is referred to as a successional agroforestry systems or SAFS, which sometimes refer to a broader concept originating in Latin America. The system focuses on replicating natural systems of accumulation of nutrients in ecosystems, replicating secondary succession, in order to create productive forest ecosystems that produce food, ecosystem services and other forest products.
The system relies heavily on several processes:
Dense planting mixing perennial and annual crops
Rapid cutting and composting of fast growing pioneer species, to accumulate nutrients and biomass
Creating greater water retention on the land through improving penetration of water into soil and plant water cycling
The systems were first developed in tropical Brazil, but many similar systems have been tested in temperate environments as soil and ecosystem restoration tactics.
The framework for the syntropic agroforestry is advocated for by Agenda Gotsch an organization built to promote the systems.
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Syntropic systems have a number of documented benefits, including increased soil water penetration, increases to productivity on marginal land that has since become and soil temperature moderation.
In Burma
Taungya is a system from Burma. In the initial stages of an orchard or tree plantation, trees are small and widely spaced. The free space between the newly planted trees accommodates a seasonal crop. Instead of costly weeding, the underutilized area provides an additional output and income. More complex taungyas use between-tree space for multiple crops. The crops become more shade tolerant as the tree canopies grow and the amount of sunlight reaching the ground declines. Thinning can maintain sunlight levels.
In India
Itteri agroforestry systems have been used in Tamil Nadu since time immemorial. They involve the deliberate management of multipurpose trees and shrubs grown in intimate association with herbaceous species. They are often found along village and farm roads, small gullies, and field boundaries.
Bamboo-based agroforestry systems (Dendrocalamus strictus + sesame–chickpea) have been studied for enhancing productivity in semi-arid tropics of central India.
In Africa
A project to mitigate climate change with agriculture was launched in 2019 by the "Global EverGreening Alliance". The target is to sequester carbon from the atmosphere. By 2050 the restored land should sequestrate 20 billion tons of carbon annually
Shamba (Swahili for 'plantation') is an agroforestry system practiced in East Africa, particularly in Kenya. Under this system, various crops are combined: bananas, beans, yams and corn, to which are added timber resources, beekeeping, medicinal herbs, mushrooms, forest fruits, fodder for livestock, etc.
In Hawai'i
Native Hawaiians formerly practiced agroforestry adapted to the islands' tropical landscape. Their ability to do this influenced the region's carrying capacity, social conflict, cooperation, and political complexity. More recently, after scientific study of lo’I systems, attempts have been made to reintroduce dryland agroforestry in Hawai’i Island and Maui, fostering interdisciplinary collaboration between political leaders, landowners, and scientists.
Temperate
Although originally a concept in tropical agronomy, agroforestry's multiple benefits, for instance in nutrient cycles and potential for mitigating droughts, have led to its adoption in the USA and Europe.
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The United States Department of Agriculture distinguishes five applications of agroforestry for temperate climates, namely alley cropping, forest farming, riparian forest buffers, silvopasture, and windbreaks.
Alley cropping
Alley cropping can also be used in temperate climates. Strip cropping is similar to alley cropping in that trees alternate with crops. The difference is that, with alley cropping, the trees are in single rows. With strip cropping, the trees or shrubs are planted in wide strips. The purpose can be, as with alley cropping, to provide nutrients, in leaf form, to the crop. With strip cropping, the trees can have a purely productive role, providing fruits, nuts, etc. while, at the same time, protecting nearby crops from soil erosion and harmful winds.
Inga alley cropping
Inga alley cropping is the planting agricultural crops between rows of Inga trees. It has been promoted by Mike Hands.
Using the Inga tree for alley cropping has been proposed as an alternative to the much more ecologically destructive slash and burn cultivation. The technique has been found to increase yields. It is sustainable agriculture as it allows the same plot to be cultivated over and over again thus eliminating the need for burning of the rainforests to get fertile plots.
Inga tree
Inga trees are native to many parts of Central and South America. Inga grows well on the acid soils of the tropical rainforest and former rainforest. They are leguminous and fix nitrogen into a form usable by plants. Mycorrhiza growing within the roots (arbuscular mycorrhiza) was found to take up spare phosphorus, allowing it to be recycled into the soil.
Other benefits of Inga include the fact that it is fast growing with thick leaves which, when left on the ground after pruning, form a thick cover that protects both soil and roots from the sun and heavy rain. It branches out to form a thick canopy so as to cut off light from the weeds below and withstands careful pruning year after year.
History
The technique was first developed and trialled by tropical ecologist Mike Hands in Costa Rica in the late 1980s and early '90s. Research funding from the EEC allowed him to experiment with species of Inga. Although alley cropping had been widely researched, it was thought that the tough pinnate leaves of the Inga tree would not decompose quickly enough.
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The Inga is used as hedges and pruned when large enough to provide a mulch in which bean and corn seeds are planted. This results in both improving crop yields and the retention of soil fertility on the plot that is being farmed. Hands had seen the devastating consequences that are caused by slash and burn agriculture while working in Honduras; this new technique seemed to offer the solution to the environmental and economic problems faced by so many slash and burn farmers.
Although this technique has the potential to save rainforest and lift many out of poverty, Inga alley cropping has not yet reached its full potential, although the charity Inga Foundation, headed by Mike Hands, has been consulted about potential projects in Haiti ( which is almost completely deforested) and the Congo. Discussions have also been mooted about projects in Peru and Madagascar. Another charity, Rainforest Saver formed to promote Inga Alley Cropping, started a project in 2016 in Ecuador, in the area of the Amazon where Inga edulis originates from, and by the end of 2018 more than 60 farms in the area had Inga plots. Rainforest Saver also started a project in Cameroon in 2009, where in late 2018 there were around 100 farms with Inga plots, mainly in Western Cameroon.
Method
For Inga alley cropping the trees are planted in rows (hedges) close together, with a gap, the alley, of about 4m between the rows. An initial application of rock phosphate has kept the system going for many years.
When the trees have grown, usually in about two years, the canopies close over the alley and cut off the light and so smother the weeds.
The trees are then carefully pruned. The larger branches are used for firewood. The smaller branches and leaves are left on the ground in the alleys. These rot down into a good mulch (compost). If any weeds haven't been killed off by lack of light the mulch smothers them.
The farmer then pokes holes into the mulch and plants their crops into the holes.
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The crops grow, fed by the mulch. The crops feed on the lower layers while the latest prunings form a protective layer over the soil and roots, shielding them from both the hot sun and heavy rain. This makes it possible for the roots of both the crops and the trees to stay to a considerable extent in the top layer of soil and the mulch, thus benefiting from the food in the mulch, and escaping soil pests and toxic minerals lower down. Pruning the Inga also makes its roots die back, thus reducing competition with the crops.
Forest farming
In forest farming, high-value crops are grown under a suitably-managed tree canopy. This is sometimes called multi-story cropping, or in tropical villages as home gardening. It can be practised at varying levels of intensity but always involves some degree of management; this distinguishes it from simple harvesting of wild plants from the forest.
Riparian forest buffers
Riparian buffers are strips of permanent vegetation located along or near active watercourses or in ditches where water runoff concentrates. The purpose is to keep nutrients and soil from contaminating the water.
Silvopasture
Trees can benefit fauna in a silvopasture system, where cattle, goats, or sheep browse on grasses grown under trees.
In hot climates, the animals are less stressed and put on weight faster when grazing in a cooler, shaded environment. The leaves of trees or shrubs can also serve as fodder. Similar systems support other fauna. Deer and pigs gain when living and feeding in a forest ecosystem, especially when the tree forage nourishes them. In aquaforestry, trees shade fish ponds. In many cases, the fish eat the leaves or fruit from the trees.
The dehesa or montado system of silviculture are an example of pigs and bulls being held extensively in Spain and Portugal.
Windbreaks
Windbreaks reduce wind velocity over and around crops. This increases yields through reduced drying of the crop and/or by preventing the crop from toppling in strong wind gusts.
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In Switzerland
Since the 1950s, four-fifths of Swiss Hochstammobstgärten (traditional orchards with tall trees) have disappeared. An agroforestry scheme was tested here with trees together with annual crops. Trees tested were walnut (Juglans regia) and cherry (Prunus avium). Forty to seventy trees per hectare were recommended, yields were somewhat decreasing with increasing tree height and foliage. However, the total yield per area is shown to be up to 30 percent higher than for monocultural systems.
Another set of tests involve growing Populus tremula for biofuel at 52 trees a hectare and with grazing pasture alternated every two to three years with maize or sorghum, wheat, strawberries and fallowing between rows of modern short-pruned & grafted apple cultivars ('Boskoop' & 'Spartan') and growing modern sour cherry cultivars ('Morina', 'Coraline' and 'Achat') and apples, with bushes in the rows with tree (dogrose, Cornus mas, Hippophae rhamnoides) intercropped with various vegetables.
Forest gardening
Forest gardening is a low-maintenance, sustainable, plant-based food production and agroforestry system based on woodland ecosystems, incorporating fruit and nut trees, shrubs, herbs, vines and perennial vegetables which have yields directly useful to humans. Making use of companion planting, these can be intermixed to grow in a succession of layers to build a woodland habitat.
Forest gardening is a prehistoric method of securing food in tropical areas. In the 1980s, Robert Hart coined the term "forest gardening" after adapting the principles and applying them to temperate climates.
History
Since prehistoric times, hunter-gatherers might have influenced forests, for instance in Europe by Mesolithic people bringing favored plants like hazel with them. Forest gardens are probably the world's oldest form of land use and most resilient agroecosystem. First Nation villages in Alaska with forest gardens filled with nuts, stone fruit, berries, and herbs, were noted by an archeologist from the Smithsonian in the 1930s.
Forest gardens are still common in the tropics and known as Kandyan forest gardens in Sri Lanka; , family orchards in Mexico; agroforests; or shrub gardens. They have been shown to be a significant source of income and food security for local populations.
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Robert Hart adapted forest gardening for the United Kingdom's temperate climate during the 1980s.
In temperate climates
Hart began farming at Wenlock Edge in Shropshire to provide a healthy and therapeutic environment for himself and his brother Lacon. Starting as relatively conventional smallholders, Hart soon discovered that maintaining large annual vegetable beds, rearing livestock and taking care of an orchard were tasks beyond their strength. However, a small bed of perennial vegetables and herbs he planted was looking after itself with little intervention.
Following Hart's adoption of a raw vegan diet for health and personal reasons, he replaced his farm animals with plants. The three main products from a forest garden are fruit, nuts and green leafy vegetables. He created a model forest garden from a 0.12 acre (500 m2) orchard on his farm and intended naming his gardening method ecological horticulture or ecocultivation. Hart later dropped these terms once he became aware that agroforestry and forest gardens were already being used to describe similar systems in other parts of the world. He was inspired by the forest farming methods of Toyohiko Kagawa and James Sholto Douglas, and the productivity of the Keralan home gardens; as Hart explained, "From the agroforestry point of view, perhaps the world's most advanced country is the Indian state of Kerala, which boasts no fewer than three and a half million forest gardens ... As an example of the extraordinary intensity of cultivation of some forest gardens, one plot of only was found by a study group to have twenty-three young coconut palms, twelve cloves, fifty-six bananas, and forty-nine pineapples, with thirty pepper vines trained up its trees. In addition, the smallholder grew fodder for his house-cow."
Seven-layer system
Further development
The Agroforestry Research Trust, managed by Martin Crawford, runs experimental forest gardening projects on a number of plots in Devon, United Kingdom. Crawford describes a forest garden as a low-maintenance way of sustainably producing food and other household products.
Ken Fern had the idea that for a successful temperate forest garden a wider range of edible shade tolerant plants would need to be used. To this end, Fern created the organisation Plants for a Future which compiled a plant database suitable for such a system. Fern used the term woodland gardening, rather than forest gardening, in his book Plants for a Future.
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Kathleen Jannaway, the cofounder of Movement for Compassionate Living (MCL) with her husband Jack, wrote a book outlining a sustainable vegan future called Abundant Living in the Coming Age of the Tree in 1991. The MCL promotes forest gardening and other types of vegan organic gardening. In 2009 it provided a grant of £1,000 to the Bangor Forest Garden project in Gwynedd, North West Wales.
Permaculture
Bill Mollison, who coined the term permaculture, visited Hart at his forest garden in October 1990. Hart's seven-layer system has since been adopted as a common permaculture design element.
Numerous permaculturalists are proponents of forest gardens, or food forests, such as Graham Bell, Patrick Whitefield, Dave Jacke, Eric Toensmeier and Geoff Lawton. Bell started building his forest garden in 1991 and wrote the book The Permaculture Garden in 1995, Whitefield wrote the book How to Make a Forest Garden in 2002, Jacke and Toensmeier co-authored the two volume book set Edible Forest Gardens in 2005, and Lawton presented the film Establishing a Food Forest in 2008.
Geographical distribution
Forest gardens, or home gardens, are common in the tropics, using intercropping to cultivate trees, crops, and livestock on the same land. In Kerala in south India as well as in northeastern India, the home garden is the most common form of land use and is also found in Indonesia. One example combines coconut, black pepper, cocoa and pineapple. These gardens exemplify polyculture, and conserve much crop genetic diversity and heirloom plants that are not found in monocultures. Forest gardens have been loosely compared to the religious concept of the Garden of Eden.
Americas
The Amazon rainforest, rather than being a pristine wilderness, has been shaped by humans for at least 11,000 years through practices such as forest gardening and terra preta. Since the 1970s, numerous geoglyphs have been discovered on deforested land in the Amazon rainforest, furthering the evidence of pre-Columbian civilizations.
On the Yucatán Peninsula, much of the Maya food supply was grown in "orchard gardens", known as pet kot. The system takes its name from the low wall of stones (pet meaning 'circular' and kot, 'wall of loose stones') that characteristically surrounds the gardens.
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The environmental historian William Cronon argued in his 1983 book Changes in the Land that indigenous North Americans used controlled burning to form ideal habitat for wild game. The natural environment of New England was sculpted into a mosaic of habitats. When indigenous Americans hunted, they were "harvesting a foodstuff which they had consciously been instrumental in creating". Most English settlers, however, assumed that the wealth of food provided by the forest was a result of natural forces, and that indigenous people lived off "the unplanted bounties of nature." Animal populations declined after settlement, while fields of strawberries and raspberries found by the earliest settlers became overgrown and disappeared for want of maintenance.
Plants
Some plants, such as wild yam, work as both a root plant and as a vine. Ground covers are low-growing edible forest garden plants that help keep weeds in control and provide a way to utilize areas that would otherwise be unused.
Cardamom
Ginger
Chervil
Bergamot
Sweet woodruff
Sweet cicely
Projects
El Pilar on the Belize–Guatemala border features a forest garden to demonstrate traditional Maya agricultural practices. A further one acre model forest garden, called Känan K'aax (meaning 'well-tended garden' in Mayan), is funded by the National Geographic Society and developed at Santa Familia Primary School in Cayo.
In the United States, the largest known food forest on public land is believed to be the seven acre Beacon Food Forest in Seattle, Washington. Other forest garden projects include those at the central Rocky Mountain Permaculture Institute in Basalt, Colorado, and Montview Neighborhood farm in Northampton, Massachusetts. The Boston Food Forest Coalition promotes local forest gardens.
In Canada Richard Walker has been developing and maintaining food forests in British Columbia for over 30 years. He developed a three-acre food forest that at maturity provided raw materials for a plant nursery and herbal business as well as food for his family. The Living Centre has developed various forest garden projects in Ontario.
In the United Kingdom, other than those run by the Agroforestry Research Trust (ART), projects include the Bangor Forest Garden in Gwynedd, northwest Wales. Martin Crawford from ART administers the Forest Garden Network, an informal network of people and organisations who are cultivating forest gardens.
Since 2014, Gisela Mir and Mark Biffen have been developing a small-scale edible forest garden in Cardedeu near Barcelona, Spain, for experimentation and demonstration.
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Forest farming
Forest farming is the cultivation of high-value specialty crops under a forest canopy that is intentionally modified or maintained to provide shade levels and habitat that favor growth and enhance production levels. Forest farming encompasses a range of cultivated systems from introducing plants into the understory of a timber stand to modifying forest stands to enhance the marketability and sustainable production of existing plants.
Forest farming is a type of agroforestry practice characterized by the "four I's": intentional, integrated, intensive and interactive. Agroforestry is a land management system that combines trees with crops or livestock, or both, on the same piece of land. It focuses on increasing benefits to the landowner as well as maintaining forest integrity and environmental health. The practice involves cultivating non-timber forest products or niche crops, some of which, such as ginseng or shiitake mushrooms, can have high market value.
Non-timber forest products (NTFPs) are plants, parts of plants, fungi, and other biological materials harvested from within and on the edges of natural, manipulated, or disturbed forests. Examples of crops are ginseng, shiitake mushrooms, decorative ferns, and pine straw. Products typically fit into the following categories: edible, medicinal and dietary supplements, floral or decorative, or specialty wood-based products.
History
Forest farming, though not always by that name, is practiced around the world. For centuries, humans have relied on fruits, nuts, seeds, parts of foliage and pods from trees and shrubs in the forests to feed themselves and their livestock. Over time, certain species have been selected for cultivation near homes or livestock to provide food or medicine. For example, in the southern United States, mulberry trees are used as a feedstock for pigs and often cultivated near pig quarters.
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In 1929, J. Russell Smith, Emeritus Professor of Economic Geography at Columbia University, published "Tree Crops – A Permanent Agriculture" which stated that crop-yielding trees could provide useful substitutes for cereals in animal feeding programs, as well as conserve environmental health. Toyohiko Kagawa read and was heavily influenced by Smith’s publication and began experimental cultivation under trees in Japan during the 1930s. Through forest farming, or three-dimensional forestry, Kagawa addressed problems of soil erosion by persuading many of Japan's upland farmers to plant fodder trees to conserve soil, supply food and feed animals. He combined extensive plantings of walnut trees, harvested the nuts and fed them to the pigs, then sold the pigs as a source of income. When the walnut trees matured, they were sold for timber and more trees were planted so that there was a continuous cycle of economic cropping that provided both short-term and long-term income to the small landowner. The success of these trials prompted similar research in other countries. World War II disrupted communication and slowed advances in forest farming. In the mid-1950s research resumed in places such as southern Africa. Kagawa was also an inspiration to Robert Hart pioneered forest gardening in temperate climates in the sixties in Shropshire, England.
In earlier years, livestock were often considered part of the forest farming system. Now they are typically excluded and agroforestry systems that integrate trees, forages and livestock are referred to as silvopastures. Because forest farming combines ecological stability of natural forests and productive agriculture systems, it is considered to have great potential for regenerating soils, restoring ground water supplies, controlling floods and droughts and cultivating marginal lands.
Principles
Forest farming principles constitute an ecological approach to forest management. Forest resources are judiciously used while biodiversity and wildlife habitat are conserved. Forest farms have the potential to restore ecological balance to fragmented second growth forests through intentional manipulation to create the desired forest ecosystem.
In some instances, the intentional introduction of species for botanicals, medicinals, food or decorative products is accomplished using existing forests. The tree cover, soil type, water supply, land form and other site characteristics determine what species will thrive. Developing an understanding of species/site relationships as well as understanding the site limitations is necessary to utilize these resources for production needs, while conserving adequate resources for the long-term health of the forest.
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Apart from the environmental benefits, forest farming can increase the economic value of forest property and provide short- and long-term benefits to the landowner. Forest farming provides economic return from intact forest ecosystems, but timber sales can remain part of the long-term management strategy.
Methods
Forest farming methods may include: Intensive, yet careful thinning of overstocked, suppressed tree stands; multiple integrated entries to accomplish thinning so that systemic shock is minimized; and interactive management to maintain a cross-section of healthy trees and shrubs of all ages and species. Physical disturbance to the surrounding area should be minimized. The following are forest farming techniques described in the Training Manual produced by the Center for Agroforestry at the University of Missouri.
Level of management that is required
(from most intense to least intense)
1. Forest gardening is the most intensive of forest farming methods. In addition to thinning the overstory, this method involves clearing the understory of undesirable vegetation and other practices that are closely related to agronomy (tillage, fertilization, weeding, and control of disease and insects and wildlife management). Due to input levels, this method often produces lower valued products compared to other methods. Forest gardens take advantage of the vertical levels of light availability and space under the forest canopy so that more than one crop can be grown at once if desired.
2. Wild-simulated seeks to maintain a natural growing environment, yet enriches local NTFP populations to create an abundant renewable supply of the products. Minimal disturbance and natural growing conditions ensure products will be similar in appearance and quality of those harvested from the wild. Rather than till, practitioners often rake leaves to expose soil, sow seed directly onto the ground, and then cover with leaves again. Since this method produces NTFPs that closely resemble wild plants; they often command a higher price than NTFPs produced using the forest gardening method.
3. Forest tending involves adjusting tree crown density to manipulate light levels that favor natural reproduction of desirable NTFPs. This low intensity management approach does not involve supplemental planting to increase populations of desired NTFPs.
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4. Wildcrafting is the harvesting of naturally growing NTFPs. It is not considered a forest farming practice since there is no human involvement in the plant’s establishment and maintenance. However, wildcrafters often take steps to protect NTFPs with future harvests in mind. It becomes agroforestry once forest thinnings, or other inputs, are applied to sustain or maintain plant populations that might otherwise succumb to successional changes in the forest. The most important difference between forest farming and wildcrafting is that forest farming intentionally produces NTFPS, whereas wildcrafting seeks and gathers from naturally growing NTFPs.
Production considerations
Forest farming can be a small business opportunity for landowners and requires careful planning, including a business and marketing plan. Learning how to market the NTFPs on the Internet is an option, but may entail higher shipping costs. Landowners should consider all options for selling their products including, farmer’s markets or restaurants that focus on locally grown ingredients. The development phase should include a forest management plan that states the landowner’s objectives and a resource inventory. Start-up costs should be analyzed as specific equipment may be necessary to harvest or process the product, whereas other crops require minimal initial investment. Local incentives for sustainable forest management, as well as regulations and policies should be explored. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) regulates international trade of certain plant (American ginseng and goldenseal) and animal species. To be legally exported, regulated plants must be harvested and records kept according to CITES rules and restrictions. Many states also have harvesting regulations for certain native plants that are searchable online. Another good source to start with on information is the Medicinal Plants at Risk 2008 report, by the Center for Biological Diversity] in the U.S.
Examples of crops
(from the National Agroforestry Center)
Medicinal herbs:
Ginseng (Panax quinquefolius)
Black Cohosh (Actaea racemosa)
Goldenseal (Hydrastis canadensis)
Bloodroot (Sanguinaria canadensis)
Pacific yew (Taxus brevifolia)
Mayapple (Podophyllum peltatum)
Saw palmetto (Serenoa repens)
American Pokeweed (Phytolacca americana)
Nuts:
Black walnut (Juglans nigra)
Hazelnut (Corylus avellana)
Shagbark hickory (Carya ovata)
Beechnut (Fagus sylvatica)
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Fruit:
Pawpaw (Asimina triloba)
Currants (Ribes spp)
Elderberry (Sambucus spp)
Serviceberry (Amelanchier spp)
Blackberry (Rubus spp)
Huckleberry (Gaylussacia brachycera)
Other food crops:
Ramps (wild leeks) (Allium tricoccum)
Syrups (maple)
Honey
Mushrooms
Other edible roots
Other products: (mulch, decoratives, crafts, dyes)
Pine straw
Willow twigs
Vines
Beargrass (Xerophyllum tenax)
Ferns
Pine cones
Moss
Native ornamentals:
Rhododendron (Rhododendron catawbiense)
Highbush cranberry (Viburnum trilobum)
Flowering dogwood (Cornus florida)
Farmer-managed natural regeneration
Farmer-managed natural regeneration (FMNR) is a low-cost, sustainable land restoration technique used to combat poverty and hunger amongst poor subsistence farmers in developing countries by increasing food and timber production, and resilience to climate extremes. It involves the systematic regeneration and management of trees and shrubs from tree stumps, roots and seeds. FMNR was developed by the Australian agricultural economist Tony Rinaudo in the 1980s in West Africa. The background and development are described in Rinaudo's book The Forest Underground.
FMNR is especially applicable, but not restricted to, the dryland tropics. As well as returning degraded croplands and grazing lands to productivity, it can be used to restore degraded forests, thereby reversing biodiversity loss and reducing vulnerability to climate change. FMNR can also play an important role in maintaining not-yet-degraded landscapes in a productive state, especially when combined with other sustainable land management practices such as conservation agriculture on cropland and holistic management on range lands.
FMNR adapts centuries-old methods of woodland management, called coppicing and pollarding, to produce continuous tree-growth for fuel, building materials, food and fodder without the need for frequent and costly replanting. On farmland, selected trees are trimmed and pruned to maximise growth while promoting optimal growing conditions for annual crops (such as access to water and sunlight). When FMNR trees are integrated into crops and grazing pastures there is an increase in crop yields, soil fertility and organic matter, soil moisture and leaf fodder. There is also a decrease in wind and heat damage, and soil erosion.
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FMNR complements the evergreen agriculture, conservation agriculture and agroforestry movements. It is considered a good entry point for resource-poor and risk-averse farmers to adopt a low-cost and low-risk technique. This in turn has acted as a stepping stone to greater agricultural intensification as farmers become more receptive to new ideas.
Background
Throughout the developing world, immense tracts of farmland, grazing lands and forests have become degraded to the point they are no longer productive. Deforestation continues at a rapid pace. In Africa's drier regions, 74 percent of rangelands and 61 percent of rain-fed croplands are damaged by moderate to very severe desertification. In some African countries deforestation rates exceed planting rates by 300:1.
Degraded land has an extremely detrimental effect on the lives of subsistence farmers who depend on it for their food and livelihoods. Subsistence farmers often make up to 70–80 percent of the population in these regions and they regularly suffer from hunger, malnutrition and even famine as a consequence.
In the Sahel region of Africa, a band of savanna which runs across the continent immediately south of the Sahara Desert, large tracts of once-productive farmland are turning to desert. In tropical regions across the world, where rich soils and good rainfall would normally assure bountiful harvests and fat livestock, some environments have become so degraded they are no longer productive.
Severe famines across the African Sahel in the 1970s and 1980s led to a global response, and stopping desertification became a top priority. Conventional methods of raising exotic and indigenous tree species in nurseries were used. Despite investing millions of dollars and thousands of hours of labour, there was little overall impact. Conventional approaches to reforestation in such harsh environments faced insurmountable problems and were costly and labour-intensive. Once planted out, drought, sand storms, pests, competition from weeds and destruction by people and animals negated efforts. Low levels of community ownership were another inhibiting factor.
Existing indigenous vegetation was generally dismissed as 'useless bush', and it was often cleared to make way for exotic species. Exotics were planted in fields containing living and sprouting stumps of indigenous vegetation, the presence of which was barely acknowledged, let alone seen as important.
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This was an enormous oversight. In fact, these living tree stumps are so numerous they constitute a vast 'underground forest' just waiting for some care to grow and provide multiple benefits at little or no cost. Each stump can produce between 10 and 30 stems each. During the process of traditional land preparation, farmers saw the stems as weeds and slashed and burnt them before sowing their food crops. The net result was a barren landscape for much of the year with few mature trees remaining. To the casual observer, the land was turning to desert. Most concluded that there were no trees present and that the only way to reverse the problem was through tree planting.
Meanwhile, established indigenous trees continued to disappear at an alarming rate. In Niger, from the 1930s until 1993, forestry laws took tree ownership and responsibility for the care of trees out of the hands of the people. Reforestation through conventional tree planting seemed to be the only way to address desertification at the time.
History
In the early-1980s, in the Maradi region of the Republic of Niger, the missionary organisation, Serving in Mission (SIM), was unsuccessfully attempting to reforest the surrounding districts using conventional means. In 1983, SIM began experimenting and promoting FMNR amongst about 10 farmers. During the famine of 1984, a food-for-work program was introduced that saw some 70,000 people exposed to FMNR and its practice on around 12,500 hectares of farmland. From 1985 to 1999, FMNR continued to be promoted locally and nationally as exchange visits and training days were organised for various NGOs, government foresters, Peace Corps volunteers, and farmer and civil society groups. Additionally, SIM project staff and farmers visited numerous locations across Niger to provide training.
By 2004 it was ascertained that FMNR was being practised on over five million hectares or 50 percent of Niger's farmland – an average reforestation rate of 250,000 hectares per year over a 20-year period. This transformation prompted a Senior Fellow of the World Resources Institute, Chris Reij, to comment that "this is probably the largest positive environmental transformation in the Sahel and perhaps all of Africa".
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In 2004, World Vision Australia and World Vision Ethiopia initiated a forestry-based carbon sequestration project as a potential means to stimulate community development while engaging in environmental restoration. A partnership with the World Bank, the Humbo Community-based Natural Regeneration Project involved the regeneration of 2,728 hectares of degraded native forests. This brought social, economic and ecological benefits to the participating communities. Within two years, communities were collecting wild fruits, firewood, and fodder, and reported that wildlife had begun to return and erosion and flooding had been reduced. In addition, the communities are now receiving payments for the sale of carbon credits through the Clean Development Mechanism (CDM) of the Kyoto Protocol.
Following the success of the Humbo project, FMNR spread to the Tigray region of northern Ethiopia where 20,000 hectares have been set aside for regeneration, including 10 hectare FMNR model sites for research and demonstration in each of 34 sub-districts. The Government of Ethiopia has committed to reforest 15 million hectares of degraded land using FMNR as part of a climate change and renewable energy plan to become carbon neutral by 2025.
In Talensi, northern Ghana, FMNR is being practiced on 2,000–3,000 hectares and new projects are introducing FMNR into three new districts. In the Kaffrine and Diourbel regions of Senegal, FMNR has spread across 50,000 hectares in four years. World Vision is also promoting FMNR in Indonesia, Myanmar and East Timor. There are also examples of both independently promoted and spontaneous FMNR movements occurring. In Burkina Faso, for example, an increasing part of the country is being transformed into agro-forestry parkland. And in Mali, an ageing agro-forestry parkland of about six million hectares is showing signs of regeneration.
Key principles
FMNR depends on the existence of living tree stumps or roots in crop fields, grazing pastures, woodlands or forests. Each season bushy growth will sprout from the stumps/roots often appearing like small shrubs. Continuous grazing by livestock, regular burning and/or regular harvesting for fuel wood results in these 'shrubs' never attaining tree stature. On farmland, standard practice has been for farmers to slash this regrowth in preparation for planting crops, but with a little attention this growth can be turned into a valuable resource without jeopardising crop yields.
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For each stump, a decision is made as to how many stems will be chosen to grow. The tallest and straightest stems are selected and the remaining stems culled. Best results are obtained when the farmer returns regularly to prune any unwanted new stems and side branches as they appear. Farmers can then grow other crops between and around the trees. When farmers want wood they can cut the stem(s) they want and leave the rest to continue growing. The remaining stems will increase in size and value each year, and will continue to protect the environment. Each time a stem is harvested, a younger stem is selected to replace it.
Various naturally occurring tree species can be used which may also provide berries, fruits and nuts or have medicinal qualities. In Niger, commonly used species include: Strychnos spinosa, Balanites aegyptiaca, Boscia senegalensis, Ziziphus spp., Annona senegalensis, Poupartia birrea and Faidherbia albida. However, the most important determinants are whatever species are locally available, their ability to re-sprout after cutting, and the value local people place on those species.
Faidherbia albida, also known as the 'fertiliser tree', is popular for intercropping across the Sahel as it fixes nitrogen into the soil, provides fodder for livestock, and shade for crops and livestock. By shedding its leaves in the wet season, Faidherbia provides beneficial light shade to crops when high temperatures would otherwise damage crops or retard growth. Leaf fall contributes useful nutrients and organic matter to the soil.
The practice of FMNR is not confined to croplands. It is being practised on grazing land and in degraded communal forests as well. When there are no living stumps, seeds of naturally occurring species are used. In reality, there is no fixed way of practising FMNR and farmers are free to choose which species they will leave, the density of trees they prefer, and the timing and method of pruning.
In practice
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Benefits
FMNR can restore degraded farmlands, pastures and forests by increasing the quantity and value of woody vegetation, by increasing biodiversity and by improving soil structure and fertility through leaf litter and nutrient cycling. The reforestation also retards wind and water erosion; it creates windbreaks which decrease soil moisture evaporation, and protects crops and livestock against searing winds and temperatures. Often, dried up springs reappear and the water table rises towards historic levels; insect eating predators including insects, spiders and birds return, helping to keep crop pests in check; the trees can be a source of edible berries and nuts; and over time the biodiversity of plant and animal life is increased. FMNR can be used to combat deforestation and desertification and can also be an important tool in maintaining the integrity and productivity of land that is not yet degraded.
Trials, long-running programs and anecdotal data indicate that FMNR can at least double crop yields on low fertility soils. In the Sahel, high numbers of livestock and an eight month dry season can mean that pastures are completely depleted before the rains commence. However, with the presence of trees, grazing animals can make it through the dry season by feeding on tree leaves and seed pods of some species, at a time when no other fodder is available. In northeast Ghana, more grass became available with the introduction of FMNR because communities worked together to prevent bush fires from destroying their trees.
Well designed and executed FMNR projects can act as catalysts to empower communities as they negotiate land ownership or user rights for the trees in their care. This assists with self-organisation, and with the development of new agriculture-based micro-enterprises (e.g., selling firewood, timber and handcrafts made from timber or woven grasses).
Conventional approaches to reversing desertification, such as funding tree planting, rarely spread beyond the project boundary once external funding is withdrawn. By comparison, FMNR is cheap, rapid, locally led and implemented. It uses local skills and resources – the poorest farmers can learn by observation and teach their neighbours. Given an enabling environment, or at least the absence of a 'disabling' environment, FMNR can be done at scale and spread well beyond the original target area without ongoing government or NGO intervention.
World Vision evaluations of FMNR conducted in Senegal and Ghana in 2011 and 2012 found that households practising FMNR were less vulnerable to extreme weather shocks such as drought and damaging rain and wind storms.
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The following table summarises FMNR's benefits which fit the sustainable development model of economic, social and environmental benefits:
Sources:
Key success factors and constraints
While there are numerous accounts of the uptake and spread of FMNR independent of aid and development agencies, the following factors have been found to be beneficial for its introduction and spread:
Awareness creation of FMNR's potential.
Capacity building through workshops and exchange visits.
Awareness of the devastating effects of deforestation. The adoption of FMNR is more likely when communities acknowledge their situation and the need to take action. This perception of need can be supported by education.
An FMNR champion/facilitator from within the community who encourages, challenges and trains peers. This is critical during the first three to five years, and continues to be important for up to 10 years. Regular site visits also ensure early detection and remedial action on resistance and threats to FMNR through deliberate damage to trees and theft.
The buy-in of all stakeholders including their agreement on any by-laws created for FMNR and the consequences for infringements. Stakeholders include FMNR practitioners, local, regional and national government departments of agriculture and forestry, men, women, youth, marginalised groups (including nomadic herders), cultivators and commercial interests.
Stakeholder buy-in is also important to create a critical mass of FMNR adopters in order to change social attitudes from a position of apathy or active participation in deforestation to one of proactive sustainable tree management through FMNR.
Government support through the creation of favourable policies, positive reinforcement of actions facilitating the spread of FMNR, and disincentives for actions working against the spread of FMNR. FMNR practitioners need to be confident that they will benefit from their labours (either private or community ownership of trees, or legally binding user rights).
Reinforcement of existing organisational structures (farmers clubs, development groups, traditional leadership structures) or establishment of new structures which will provide a framework for communities to practise FMNR on a local, district or region-wide basis.
A communications strategy which includes education in schools, radio programs and engagement with religious and traditional leaders to become advocates.
Establishment of a legal, transparent and accessible market for FMNR wood and non-timber forest products, enabling practitioners to benefit financially from their activities.
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Brown et al. suggest that the two main reasons why FMNR has spread so widely in Niger are attitudinal change by the community of what constitutes good land management practices, and farmers' ownership of trees. Farmers need the assurance that they will benefit from their labour. Giving farmers either outright ownership of the trees they protect, or tree-user rights, has made it possible for large-scale farmer-led reforestation to take place.
Current and future directions
Over nearly 30 years, FMNR has changed the farming landscape in some of the poorest countries in the world, including parts of Niger, Burkina Faso, Mali, and Senegal, providing subsistence farmers with the methods necessary to become more food secure and resilient against severe weather events.
The 2011–2012 food crisis in East Africa gave a stark reminder of the importance of addressing root causes of hunger. In the 2011 State of the World Report, Bunch concludes that four major factors – lack of sustainable fertile land, loss of traditional fallowing, cost of fertiliser and climate change – are coming together all at once in a sort of "perfect storm" that will almost surely result in an African famine of unprecedented proportions, probably within the next four to five years. It will most heavily affect the lowland, semi-arid to sub-humid areas of Africa (including the Sahel, parts of eastern Africa, plus a band from Malawi across to Angola and Namibia); and unless the world does something dramatic, 10 to 30 million people could die from famine between 2015 and 2020. Restoration of degraded land through FMNR is one way of addressing these major contributors to hunger.
In recent years FMNR has come to the attention of global development agencies and grassroots movements alike. The World Bank, World Resources Institute, World Agroforestry Center, USAID and the Permaculture movement are amongst those either actively promoting or advocating for the uptake of FMNR and FMNR has received recognition from a number of quarters including:
In 2010, FMNR won the Interaction 4 Best Practice and Innovation Initiative award in recognition of high technical standards and effectiveness in addressing the food security and livelihood needs of small producers in the areas of natural resource management and agro forestry.
In 2011, FMNR won the World Vision International Global Resilience Award for the most innovative initiative in the area of resilient development practice and natural environment and climate issues.
In 2012 WVA was awarded the Arbor Day Award for Education Innovation.
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In April 2012, World Vision Australia – in partnership with the World Agroforestry Center and World Vision East Africa – held an international conference in Nairobi called "Beating Famine" to analyse and plan how to improve food security for the world's poor through the use of FMNR and Evergreen Agriculture. The conference was attended by more than 200 participants, including world leaders in sustainable agriculture, five East African ministers of agriculture and the environment, ambassadors, and other government representatives from Africa, Europe, and Australia, and leaders from non-government and international organisations.
Two major outcomes of the conference were:
The establishment of a global FMNR network of key stakeholders to promote, encourage and initiate the scale-up of FMNR globally.
Country, regional and global level plans as a basis for inter-organisation collaboration for FMNR scale-up.
The conference acted as a catalyst for media coverage of FMNR in some of the world's leading outlets and a noticeable increase in momentum for an FMNR global movement. This heightened awareness of FMNR has created an opportunity for it to spread exponentially worldwide.
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Nephrops norvegicus, known variously as the Norway lobster, Dublin Bay prawn, (compare langostino) or scampi, is a slim, coral colored lobster that grows up to long, and is "the most important commercial crustacean in Europe". It is now the only extant species in the genus Nephrops, after several other species were moved to the closely related genus Metanephrops. It lives in the north-eastern Atlantic Ocean, and parts of the Mediterranean Sea, but is absent from the Baltic Sea and Black Sea. Adults emerge from their burrows at night to feed on worms and fish.
Description
Nephrops norvegicus has the typical body shape of a lobster, albeit narrower than the large genus Homarus. It is pale orange in colour, and grows to a typical length of , or exceptionally long, including the tail and claws. A carapace covers the animal's cephalothorax, while the abdomen is long and segmented, ending in a broad tail fan. The first three pairs of legs bear claws, of which the first are greatly elongated and bear ridges of spines. Of the two pairs of antennae, the second is the longer and thinner. There is a long, spinous rostrum, and the compound eyes are kidney-shaped, providing the name of the genus, from the Greek roots (nephros, "kidney") and ὄψ ("eye").
Distribution
Nephrops norvegicus is found in the north-eastern Atlantic Ocean and North Sea as far north as Iceland and northern Norway, and south to Portugal. It is found in the Mediterranean Sea and is common in the Adriatic Sea, notably the north Adriatic. It is absent from both the Black Sea and the Baltic Sea. Due to its ecological demands for particular sediments, N. norvegicus has a very patchy distribution, and is divided into over 30 populations. These populations are separated by inhospitable terrain, and adults rarely travel distances greater than a few hundred metres.
Ecology
Nephrops norvegicus adults prefer to inhabit muddy seabed sediments, with more than 40 percent silt and clay. Their burrows are semi-permanent, and vary in structure and size. Typical burrows are deep, with a distance of between the front and back entrances. Norway lobsters spend most of their time either lying in their burrows or by the entrance, leaving their shelters only to forage or mate.
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Diet
Nephrops norvegicus is a scavenger and predator that makes short foraging excursions, mainly during periods of subdued light. They feed on active prey, including worms and fish, which they capture with their chelipeds and walking legs, and food is conveyed to the mouth using the anterior walking legs, assisted by the maxillipeds.
There is evidence that Nephrops norvegicus is a major eater of jellyfish.
Parasites and symbionts
Nephrops norvegicus is the host to a number of parasites and symbionts. A number of sessile organisms attach to the exoskeleton of N. norvegicus, including the barnacle Balanus crenatus and the foraminiferan Cyclogyra, but overall Nephrops suffers fewer infestations of such epibionts than other decapod crustaceans do. In December 1995, the commensal Symbion pandora was discovered attached to the mouthparts of Nephrops norvegicus, and was found to be the first member of a new phylum, Cycliophora, a finding described by Simon Conway Morris as "the zoological highlight of the decade". S. pandora has been found in many populations of N. norvegicus, both in the north Atlantic and in the Mediterranean Sea. Individuals may be found on most segments of the lobster's mouthparts, but are generally concentrated on the central parts of the larger mouthparts, from the mandible to the third maxilliped.
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The most significant parasite of N. norvegicus is a dinoflagellate of the genus Hematodinium, which has caused epidemic infection in fished populations of N. norvegicus since the 1980s. Hematodinium is a genus that contains major pathogens of a wide variety of decapod crustaceans, although its internal taxonomy is poorly resolved. The species which attacks N. norvegicus causes a syndrome originally described as "post-moult syndrome", in which the carapace turns opaque and becomes highly pigmented, the haemolymph becomes milky white, and the animal appears moribund. Other parasites of N. norvegicus include the gregarine protozoan Porospora nephropis, the trematode Stichocotyle nephropis and the polychaete Histriobdella homari.
Life cycle
The typical life span of N. norvegicus is 5–10 years, reaching 15 years in exceptional cases. Its reproductive cycle varies depending on geographical position: "the periods of hatching and spawning, and the length of the incubation period, vary with latitude and the breeding cycle changes from annual to biennial as one moves from south to north". Incubation of eggs is temperature-dependent, and in colder climates, the duration of the incubation period increases. This means that, by the time hatching occurs, it may be too late for the females to take part in that year's breeding cycle. In warmer climates, the combined effects of recovery from moulting and ovary maturation mean that spawning can become delayed. This, in turn, has the effect of the female missing out a year of egg carrying.
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Adult male Nephrops norvegicus moult once or twice a year (usually in late winter or spring) and adult females moult up to once a year (in late winter or spring, after hatching of the eggs). In annual breeding cycles, mating takes place in the spring or winter, when the females are in the soft, post-moult state. The ovaries mature throughout the spring and summer months, and egg-laying takes place in late summer or early autumn. After spawning, the berried (egg-carrying) females return to their burrows and remain there until the end of the incubation period. Hatching takes place in late winter or early spring. Soon after hatching, the females moult and mate again.
During the planktonic larval stage (typically 1 to 2 months in duration) the nephrops larvae exhibit a diel vertical migration behaviour as they are dispersed by the local currents. This complex biophysical interaction determines the fate of the larvae; the overlap between advective pathway destination and spatial distributions of suitable benthic habitats must be favourable in order for the larvae to settle and reach maturity.
Fisheries
The muscular tail of Nephrops norvegicus is frequently eaten, and its meat is known as scampi or langoustine. N. norvegicus is eaten only on special occasions in Spain and Portugal, where it is less expensive than the common lobster, Homarus gammarus. N. norvegicus is an important species for fisheries, being caught mostly by trawling. Around 60,000 tonnes are caught annually, half of it in the United Kingdom's waters.
Besides the established trawling fleets, a significant number of fleets using lobster creels have developed. The better size and condition of lobsters caught by this method yield prices three to four times higher than animals netted by trawling. Creel fishing was found to have a reduced impact on the seafloor, require lower fuel consumption, and allow fishermen with smaller boats to participate in this high-value fishery. It has therefore been described as a reasonable alternative to demersal towed gears, and the allocation of additional fishing rights for this type of take has been suggested.
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The North East Atlantic individual biological stocks of Nephrops are identified as functional units. A number of functional units make up the sea areas over which a total allowable catch (TAC) is set annually by the EU Council of Ministers. For example, the TAC set for North Sea Nephrops is based on the aggregate total tonnage of removals recommended by science for nine separate functional unit areas. This method has attracted criticism because it can promote the overexploitation of a specific functional unit even though the overall TAC is under-fished. In 2016, the UK implemented a package of emergency technical measures with the cooperation of the fishing industry aimed at reducing fishing activity to induce recovery of the Nephrops stock in the Farn(e) Deeps off North East England which was close to collapse. A stock assessment completed in 2018 by the International Council for the Exploration of the Sea (ICES) shows that fishing pressure has been cut and this stock is now below FMSY and that stock size is above MSY Btrigger meaning that the Farne Deeps nephrops stock is being fished at a sustainable level. However, ICES also warn that any substantial transfer of the current surplus fishing opportunities from other functional units to the Farne Deeps would rapidly lead to overexploitation. This suggests that controls on fishing effort should continue at least until the biomass reaches a size that is sustainable when measured against the level of fishing activity by all fishermen wanting to target the stock. In July 2023 the area north-east of Farnes Deep was one of three sites designated as a Highly Protected Marine Area.
Discards from Nephrops fishery may account for up to 37% of the energy requirements of certain marine scavengers, such as the hagfish Myxine glutinosa. Boats involved in Nephrops fishery also catch a number of fish species such as plaice and sole, and it is thought that without that revenue, Nephrops fishery would be economically unviable.
Taxonomic history
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Nephrops norvegicus was one of the species included by Carl Linnaeus in his 1758 10th edition of , the starting point for zoological nomenclature. In that work, it was listed as , with a type locality of ("in the Norwegian sea"). In choosing a lectotype, Lipke Holthuis restricted the type locality to the Kattegat at the Kullen Peninsula in southern Sweden (). Two synonyms of the species have been published – "Astacus rugosus", described by the eccentric zoologist Constantine Samuel Rafinesque in 1814 from material collected in the Mediterranean Sea, and "Nephropsis cornubiensis", described by Charles Spence Bate and Joshua Brooking Rowe in 1880.
As new genera were erected, the species was moved, reaching its current position in 1814, when William Elford Leach erected the genus Nephrops to hold this species alone. Seven fossil species have since been described in the genus.
Populations in the Mediterranean Sea are sometimes separated as "Nephrops norvegicus var. meridionalis Zariquiey, 1935", although this taxon is not universally considered valid.
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Porcelain crabs are decapod crustaceans in the widespread family Porcellanidae, which superficially resemble true crabs. They have flattened bodies as an adaptation for living in rock crevices. They are delicate, readily losing limbs when attacked, and use their large claws for maintaining territories. They first appeared in the Tithonian age of the Late Jurassic epoch, 145–152 million years ago.
Description
Porcelain crabs are small, usually with body widths less than . They share the general body plan of a squat lobster, but their bodies are more compact and flattened, an adaptation for living and hiding under rocks. Porcelain crabs are quite fragile animals, and often shed their limbs to escape predators, hence their name. The lost appendage can grow back over several moults. Porcelain crabs have large chelae (claws), which are used for territorial struggles, but not for catching food. The fifth pair of pereiopods is reduced and used for cleaning.
Evolution
Porcelain crabs are an example of carcinisation, whereby a noncrab-like animal (in this case a relative of a squat lobster) evolves into an animal that resembles a true crab. Porcelain crabs can be distinguished from true crabs by the apparent number of walking legs (three instead of four pairs; the fourth pair is reduced and held against the carapace), and the long antennae originating on the front outside of the eyestalks. The abdomen of the porcelain crab is long and folded underneath it, free to move.
Biogeography and ecology
Porcelain crabs live in all the world's oceans, except the Arctic Ocean and the Antarctic. They are common under rocks, and can often be found and observed on rocky beaches and shorelines, startled creatures scurrying away when a stone is lifted. They feed by combing plankton and other organic particles from the water using long setae (feathery hair- or bristle-like structures) on the mouthparts.
Some of the common species of porcelain crabs in the Caribbean Sea are Petrolisthes quadratus, found in large numbers under rocks in the intertidal, and the red-and-white polka-dotted Porcellana sayana, which lives commensally within the shells inhabited by large hermit crabs. In Hong Kong, Petrolisthes japonicus is common.
Diversity
, some 4723 extant species of porcelain crab had been described, divided among these 30 genera:
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Aliaporcellana Nakasone & Miyake, 1969
Allopetrolisthes Haig, 1960
Ancylocheles Haig, 1978
Capilliporcellana Haig, 1978
Clastotoechus Haig, 1960
Enosteoides Johnson, 1970
Euceramus Stimpson, 1860
Eulenaios Ng & Nakasone, 1993
Heteropolyonyx Osawa, 2001
Heteroporcellana Haig, 1978
Liopetrolisthes Haig, 1960
Lissoporcellana Haig, 1978
Madarateuchus Harvey, 1999
Megalobrachium Stimpson, 1858
Minyocerus Stimpson, 1858
Neopetrolisthes Miyake, 1937
Neopisosoma Haig, 1960
Novorostrum Osawa, 1998
Orthochela Glassell, 1936
Pachycheles Stimpson, 1858
Parapetrolisthes Haig, 1962
Petrocheles Miers, 1876
Petrolisthes Stimpson, 1858
Pisidia Leach, 1820
Polyonyx Stimpson, 1858
Porcellana Lamarck, 1801
Porcellanella White, 1852
Pseudoporcellanella Sankarankutty, 1962
Raphidopus Stimpson, 1858
Ulloaia Glassell, 1938
The fossil record of porcelain crabs includes species of Pachycheles, Pisidia, Polyonyx, Porcellana, and a further six genera known only from fossils:
Annieporcellana Fraaije et al., 2008
Beripetrolisthes De Angeli & Garassino, 2002
Eopetrolisthes De Angeli & Garassino, 2002
Lobipetrolisthes De Angeli & Garassino, 2002
Longoporcellana Müller & Collins, 1991
The earliest claimed porcelain crab fossil was Jurellana from the Tithonian aged Ernstbrunn Limestone of Austria. However, it was subsequently determined to be a true crab. With the new oldest porcelain crab being Vibrissalana from the same locality.
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