Ecotone
Encyclopedia
An ecotone is a transition area between two biomes but different patches of the landscape, such as forest and grassland. It may be narrow or wide, and it may be local (the zone between a field and forest) or regional (the transition between forest and grassland ecosystem
s). An ecotone may appear on the ground as a gradual blending of the two communities across a broad area, or it may manifest itself as a sharp boundary line.
The word ecotone was coined from a combination of eco(logy) plus -tone, from the Greek
tonos or tension – in other words, a place where ecologies are in tension.
and cleared land
(Krummholz
). Elsewhere, a more gradually blended interface area will be found, where species from each community will be found together as well as unique local species. Mountain range
s often create such ecotones, due to the wide variety of climatic conditions experienced on their slope
s. They may also provide a boundary between species due to the obstructive nature of their terrain
. Mont Ventoux
in France
is a good example, marking the boundary between the flora
and fauna
of northern and southern France
. Most wetland
s are ecotones.
Plants in competition extend themselves on one side of the ecotone as far as their ability to maintain themselves allows. Beyond this competitors of the adjacent community take over. As a result the ecotone represents a shift in dominance. Ecotones are particularly significant for mobile animals, as they can exploit more than one set of habitat
s within a short distance. The ecotone contains not only species common to the communities on both sides; it may also include a number of highly adaptable species that tend to colonize such transitional areas. This can produce an edge effect
along the boundary line, with the area displaying a greater than usual diversity of species.
The phenomenon of increased variety of plants as well as animals at the community junction is called the "edge effect" and is essentially due to a locally broader range of suitable environmental conditions or ecological niche
s.
or salinity
gradient
), or microclimatically (hydrothermal gradient) between two ecosystems.
In contrast:
that connects the Thai-Malay Peninsula with mainland Asia
is an example of a regional scale ecotone. It marks the transition zone between the moist deciduous
forest in the mainland Southeast Asia
biogeographical region in the north and the wet seasonal dipterocarp forest in the Sundaland
region in the south. It has been shown to be the biogeographical transition between Indochinese and Sundaic faunas. Approximately 152 species of bird were found to have northern or southern range limits between these latitudes. Population genetics
studies have also found that the Kra ecotone is the major physical barrier that limits gene flow in the honeybees Apis cerana
and Apis dorsata
and the stingless bees Trigona collina
and Trigona pagdeni.
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
s). An ecotone may appear on the ground as a gradual blending of the two communities across a broad area, or it may manifest itself as a sharp boundary line.
The word ecotone was coined from a combination of eco(logy) plus -tone, from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
tonos or tension – in other words, a place where ecologies are in tension.
Formation
Changes in the physical environment may produce a sharp boundary, as in the example of the interface between areas of forestForest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
and cleared land
Land clearing in Australia
Land clearing in Australia describes the removal of native vegetation and deforestation and in Australia. Land clearing involves the removal of native vegetation and habitats, including the bulldozing of native bushlands, forests, savannah, woodlands and native grasslands and the draining of...
(Krummholz
Krummholz
Krummholz or Krumholtz formation — also called Knieholz — is a particular feature of subarctic and subalpine tree line landscapes. Continual exposure to fierce, freezing winds causes vegetation to become stunted and deformed...
). Elsewhere, a more gradually blended interface area will be found, where species from each community will be found together as well as unique local species. Mountain range
Mountain range
A mountain range is a single, large mass consisting of a succession of mountains or narrowly spaced mountain ridges, with or without peaks, closely related in position, direction, formation, and age; a component part of a mountain system or of a mountain chain...
s often create such ecotones, due to the wide variety of climatic conditions experienced on their slope
Slope
In mathematics, the slope or gradient of a line describes its steepness, incline, or grade. A higher slope value indicates a steeper incline....
s. They may also provide a boundary between species due to the obstructive nature of their terrain
Terrain
Terrain, or land relief, is the vertical and horizontal dimension of land surface. When relief is described underwater, the term bathymetry is used...
. Mont Ventoux
Mont Ventoux
Mont Ventoux is a mountain in the Provence region of southern France, located some 20 km northeast of Carpentras, Vaucluse. On the north side, the mountain borders the Drôme département. It is the largest mountain in the region and has been nicknamed the "Giant of Provence", or "The Bald...
in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
is a good example, marking the boundary between the flora
Flora
Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...
and fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
of northern and southern France
Southern France
Southern France , colloquially known as le Midi is defined geographical area consisting of the regions of France that border the Atlantic Ocean south of the Gironde, Spain, the Mediterranean, and Italy...
. Most wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....
s are ecotones.
Plants in competition extend themselves on one side of the ecotone as far as their ability to maintain themselves allows. Beyond this competitors of the adjacent community take over. As a result the ecotone represents a shift in dominance. Ecotones are particularly significant for mobile animals, as they can exploit more than one set of habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s within a short distance. The ecotone contains not only species common to the communities on both sides; it may also include a number of highly adaptable species that tend to colonize such transitional areas. This can produce an edge effect
Edge effect
The edge effect in ecology is the effect of the juxtaposition or placing side by side of contrasting environments on an ecosystem.This term is commonly used in conjunction with the boundary between natural habitats, especially forests, and disturbed or developed land. Edge effects are especially...
along the boundary line, with the area displaying a greater than usual diversity of species.
The phenomenon of increased variety of plants as well as animals at the community junction is called the "edge effect" and is essentially due to a locally broader range of suitable environmental conditions or ecological niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
s.
Ecotones and ecoclines
An ecotone is often associated with an ecocline: a "physical transition zone" between two systems. The ecotone and ecocline concepts are sometimes confused: an ecocline can signal an ecotone chemically (ex: pHPH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
or salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
gradient
Gradient
In vector calculus, the gradient of a scalar field is a vector field that points in the direction of the greatest rate of increase of the scalar field, and whose magnitude is the greatest rate of change....
), or microclimatically (hydrothermal gradient) between two ecosystems.
In contrast:
- an ecocline is a variation of the physicochemicalPhysical chemistryPhysical chemistry is the study of macroscopic, atomic, subatomic, and particulate phenomena in chemical systems in terms of physical laws and concepts...
environment dependent of one or two physico-chemical factors of life, and thus presence/absence of certain species. An ecocline can be a thermoclineThermoclineA thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...
, chemoclineChemoclineA chemocline is a cline caused by a strong, vertical chemistry gradient within a body of water. A chemocline is analogous to a thermocline, the border at which warmer and cooler waters meet in an ocean, sea, lake, or other body of water...
(chemical gradient), haloclineHaloclineIn oceanography, a halocline is a subtype of chemocline caused by a strong, vertical salinity gradient within a body of water. Because salinity affects the density of seawater, it can play a role in its vertical stratification...
(salinity gradient) or pycnoclinePycnoclineA pycnocline is the cline or layer where the density gradient is greatest within a body of water. An ocean current is generated by the forces such as breaking waves, terms of temperature and salinity differences, wind, Coriolis effect, and tides caused by the gravitational pull of the Moon and the...
(variations in density of water induced by temperature or salinity). - an ecotone describes a variation in species prevalenceRelative species abundanceRelative species abundance is a component of biodiversity and refers to how common or rare a species is relative to other species in a defined location or community...
and is often not strictly dependent a major physical factor separating an ecosystem from another, with resulting habitat variability. An ecotone is often unobtrusive and harder to measure.
Examples
The Kra ecotone between 11°N and 13°N latitude just north of the Kra IsthmusKra Isthmus
The Kra Isthmus is the narrow land bridge which connects the Malay Peninsula with the mainland of Asia, and popularly named "The Devil's Neck".-Geography:...
that connects the Thai-Malay Peninsula with mainland Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
is an example of a regional scale ecotone. It marks the transition zone between the moist deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
forest in the mainland Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
biogeographical region in the north and the wet seasonal dipterocarp forest in the Sundaland
Sundaland
Sundaland is a biogeographical region of Southeastern Asia which encompasses the areas of the Asian continental shelf that was exposed during the last ice age. It included the Malay Peninsula on the Asian mainland, as well as the large islands of Borneo, Java, and Sumatra and their surrounding...
region in the south. It has been shown to be the biogeographical transition between Indochinese and Sundaic faunas. Approximately 152 species of bird were found to have northern or southern range limits between these latitudes. Population genetics
Population genetics
Population genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. It also takes into account the factors of recombination, population subdivision and population...
studies have also found that the Kra ecotone is the major physical barrier that limits gene flow in the honeybees Apis cerana
Apis cerana
Apis cerana, or the Asiatic honey bee , is a species of honey bee found in southern and southeastern Asia, such as China, India, Japan, Malaysia, Nepal, Bangladesh and Papua New Guinea. This species is the sister species of Apis koschevnikovi, and both are in the same subgenus as the Western honey...
and Apis dorsata
Apis dorsata
Apis dorsata, the giant honey bee, is a honey bee of southern and southeastern Asia mainly in forested areas like the Terai of Nepal...
and the stingless bees Trigona collina
Trigona collina
Trigona collina is a one of the stingless bee species with reported nesting sites in Thailand.-External links:*, Hymenoptera collection of the Slovenian Museum of Natural History, Ljubljana**...
and Trigona pagdeni.