Editing Ecotone

{{Short description|Transition area between two biological communities}}
{{Other uses}}
{{More citations needed|date=October 2015}}
[[File:Blick vom Löns Turm HemmelsdorferSee Ausfluss aalbek.jpg|thumb|[[Reed bed]]s are a common form of lakeside ecotone. The beds tend to accumulate organic matter which is then colonised by trees, forcing the reeds further into the lake.]]
An '''ecotone''' is a transitional area between two plant communities,<ref>{{cite book|title=Species Diversity Patterns at Ecotones|first=Amanda|last=Senft|url=http://www.bio.unc.edu/faculty/peet/lab/theses/Senft_MS_2009.pdf|year=2009|format=Master's thesis|publisher=University of North Carolina|access-date=2011-01-07|archive-date=2011-09-30|archive-url=https://web.archive.org/web/20110930235343/http://www.bio.unc.edu/faculty/peet/lab/theses/Senft_MS_2009.pdf|url-status=dead}}</ref> where these meet and integrate.<ref>{{cite book|first1=Solomon Eldra|last1=Pearl|first2=Linda R.|last2=Berg|first3=Diana W.|last3=Martin|title=Biology|location=Belmont, California|publisher=Brooks/Cole|year=2011}}{{page needed|date=October 2017}}</ref> Examples include areas between grassland and forest, estuaries and lagoon, freshwater and sea water etc. An ecotone 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).<ref name=smith>{{cite book|title=Ecology and Field Biology|url=https://archive.org/details/ecologyfieldbiol00robe|url-access=registration|edition=2nd|first=Robert Leo|last=Smith|year=1974|publisher=Harper & Row|page=[https://archive.org/details/ecologyfieldbiol00robe/page/251 251]|isbn=978-0-06-500976-7}}</ref> 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.

==Etymology==
The word ''ecotone'' was coined (and its etymology given) in 1904 in "The Development and Structure of Vegetation" (Lincoln, Nebraska: Botanical Seminar) by Frederic E. Clements.  It is formed as a combination of ''ecology'' plus ''-tone'', from the [[Greek language|Greek]] ''tonos'' or tension – in other words, a place where ecologies are in tension.

==Features==
[[File:ÉcotoneLamiotCommons4.jpg|thumb|right|upright=1.3|Fig.1 & 2 show simple ecotones with equal and homogeneous surfaces in both cases. Fig.3 shows an inclusion of each medium in the other, creating multiple ecotones, which are shown in a more complex form in figure 4. Fig. 5 & 6 show the edges of forests or banks treated in such a way as to lengthen the ecotone considerably without excessively modifying the environment. Fig.7 shows a common interpenetration of media (such as that found at the edge of a forest). Fig.8 shows an ecotone that could have been formed by an animal modifying its environment.]]

There are several distinguishing features of an ecotone. First, an ecotone can have a sharp vegetation transition, with a distinct line between two communities.<ref>The Editors of Encyclopædia Britannica. "Ecotone." ''Encyclopædia Britannica'', Encyclopædia Britannica, inc., 23 Jan. 2012, www.britannica.com/science/ecotone.</ref>  For example,
a change in colors of grasses or plant life can indicate an ecotone. Second, a change in [[physiognomy]] (physical appearance of a plant species) can be a key indicator. Water bodies, such as estuaries, can also have a region of transition, and the boundary is characterized by the differences in heights of the  macrophytes or plant species present in the areas because this distinguishes the two areas' accessibility to light.<ref>{{cite journal |doi=10.1016/S0304-3770(97)00047-8 |title=Macrophytes, hydrology, and aquatic ecotones: A GIS-supported ecological survey |journal=Aquatic Botany |volume=58 |issue=3–4 |pages=379–91 |year=1997 |last1=Janauer |first1=G.A |bibcode=1997AqBot..58..379J }}</ref> Scientists look at color variations and changes in plant height. Third, a change of species can signal an ecotone. There will be specific organisms on one side of an ecotone or the other.

Other factors can illustrate or obscure an ecotone, for example, [[Seed dispersal|migration]] and the establishment of new plants. These are known as spatial mass effects, which are noticeable because some organisms will not be able to form self-sustaining populations if they cross the ecotone. If different species can survive in both communities of the two biomes, then the ecotone is considered to have [[species richness]]; ecologists measure this when studying the [[food chain]] and success of organisms. Lastly, the abundance of [[introduced species]] in an ecotone can reveal the type of biome or efficiency of the two communities sharing space.<ref>{{cite journal |doi=10.1111/j.1654-1103.2003.tb02185.x |title=Properties of ecotones: Evidence from five ecotones objectively determined from a coastal vegetation gradient |journal=Journal of Vegetation Science |volume=14 |issue=4 |pages=579–90 |year=2003 |last1=Walker |first1=Susan |last2=Wilson |first2=J. Bastow |last3=Steel |first3=John B |last4=Rapson |first4=G.L |last5=Smith |first5=Benjamin |last6=King |first6=Warren McG |last7=Cottam |first7=Yvette H |doi-access=free |bibcode=2003JVegS..14..579W }}</ref> Because an ecotone is the zone in which two communities integrate, many different forms of life have to live together and compete for space. Therefore, an ecotone can create a diverse ecosystem.

==Formation==
Changes in the physical environment may produce a sharp [[wikt:boundary|boundary]], as in the example of the interface between areas of [[forest]] and [[Land clearing in Australia|cleared land]]. 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]].<ref>{{cite journal| pmc=5395556 | pmid=28469633 | doi=10.3389/fpls.2017.00602 | volume=8 | title=Fine Root Abundance and Dynamics of Stone Pine (''Pinus cembra'') at the Alpine Treeline Is Not Impaired by Self-shading | year=2017 | journal=Front Plant Sci | page=602 | last1 = Kubisch | first1 = P | last2 = Leuschner | first2 = C | last3 = Coners | first3 = H | last4 = Gruber | first4 = A | last5 = Hertel | first5 = D| doi-access=free }}</ref> Most [[wetland]]s are ecotones. The spatial variation of ecotones often form due to disturbances, creating patches that separate patches of vegetation. Different intensity of disturbances can cause landslides, land shifts, or movement of sediment that can create these vegetation patches and ecotones.<ref>{{cite book |last1=Swanson |first1=F. J. |last2=Wondzell |first2=S. M. |last3=Grant |first3=G. E. |chapter=Landforms, Disturbance, and Ecotones |title=Landscape Boundaries |series=Ecological Studies |date=1992 |volume=92 |pages=304–323 |doi=10.1007/978-1-4612-2804-2_15 |isbn=978-1-4612-7677-7 |chapter-url=https://andrewsforest.oregonstate.edu/sites/default/files/lter/pubs/pdf/pub1056.pdf |access-date=11 November 2022 |language=en}}</ref>

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.<ref name=smith/> 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.

==Ecotones and ecoclines==
An ecotone is often associated with an [[Cline (biology)|ecocline]]: a "physical transition zone" between two systems. The ecotone and ecocline concepts are sometimes confused: an ecocline can signal an ecotone chemically (ex: [[pH]] or [[salinity]] [[gradient]]), or microclimatically ([[hydrothermal]] gradient) between two ecosystems.

In contrast:
* an ecocline is a variation of the [[physical chemistry|physicochemical]] environment dependent of one or two physico-chemical factors of life, and thus presence/absence of certain species.<ref>{{cite journal |doi=10.2307/3236065 |jstor=3236065 |title=Ecotones and ecoclines are different |journal=Journal of Vegetation Science |volume=1 |issue=1 |pages=135–8 |year=1990 |last1=Maarel |first1=Eddy |bibcode=1990JVegS...1..135V |author-link1=Eddy van der Maarel }}</ref> An ecocline can be a [[thermocline]], [[chemocline]] (chemical gradient), [[halocline]] (salinity gradient) or [[pycnocline]] (variations in density of water induced by temperature or salinity).
* ecocline transitions are less distinct (less clear-cut), have more stable conditions within, hence a higher plant species richness.<ref name=jstor2845672>{{cite journal |doi=10.2307/2845672 |jstor=2845672 |title=Ecotone Versus Ecocline: Vegetation Zonation and Dynamics Around a Small Reservoir in Tanzania |journal=Journal of Biogeography |volume=20 |issue=2 |pages=209–18 |year=1993 |last1=Backeus |first1=Ingvar |bibcode=1993JBiog..20..209B }}</ref>
* an ecotone describes a variation in [[relative species abundance|species prevalence]] and is often not strictly dependent on a major physical factor separating one ecosystem from another, with resulting habitat variability. An ecotone is often unobtrusive and harder to measure.
* an ecotone is the area where two communities interact. Ecotones can be easily identified by distinct change in soil gradient and soil composition between two communities.<ref>{{cite journal |doi=10.1556/168.2015.16.2.11 |title=Ecotones as indicators: Boundary properties in wetland-woodland transition zones |journal=Community Ecology |volume=16 |issue=2 |pages=235–43 |year=2015 |last1=Brownstein |first1=G |last2=Johns |first2=C |last3=Fletcher |first3=A |last4=Pritchard |first4=D |last5=Erskine |first5=P. D |doi-access=free |bibcode=2015ComEc..16..235B }}</ref>
* ecotone transitions are more clear-cut (distinct), conditions are less stable, hence they have a low species richness.<ref name=jstor2845672/>

==Examples==
* The Kra ecotone between 11°N and 13°N latitude just north of the [[Kra Isthmus]] that connects the [[Thai-Malay Peninsula]] with mainland [[Asia]] is an example of a regional scale ecotone.<ref name=HoA2011>{{cite book |doi=10.1007/978-3-642-16422-4_4 |chapter=Asian Honeybees and Mitochondrial DNA |title=Honeybees of Asia |pages=69–93 |year=2011 |last1=Smith |first1=Deborah R |isbn=978-3-642-16421-7 }}</ref> 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.<ref name=HoA2011/> It has been shown to be the biogeographical transition between Indochinese and Sundaic faunas.<ref name=Hughes2003/> Approximately 152 species of bird were found to have northern or southern range limits between these latitudes.<ref name=Hughes2003>{{cite journal |doi=10.1046/j.1365-2699.2003.00847.x |title=The Indochinese-Sundaic faunal transition at the Isthmus of Kra: An analysis of resident forest bird species distributions |journal=Journal of Biogeography |volume=30 |issue=4 |pages=569–80 |year=2003 |last1=Hughes |first1=Jennifer B |last2=Round |first2=Philip D |last3=Woodruff |first3=David S |bibcode=2003JBiog..30..569H |s2cid=55953315 }}</ref> [[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]]''.<ref name=Theeraapisakkun2010>{{cite journal |doi=10.4238/vol9-2gmr775 |pmid=20486087 |title=Development of a species-diagnostic marker and its application for population genetics studies of the stingless bee Trigona collina in Thailand |journal=Genetics and Molecular Research |volume=9 |issue=2 |pages=919–30 |year=2010 |last1=Theeraapisakkun |first1=M |last2=Klinbunga |first2=S |last3=Sittipraneed |first3=S |doi-access=free }}</ref>
* The [[Wallace Line]] running through the [[Lombok Strait]] between the [[Indonesia]]n islands of [[Bali]] and [[Lombok]] is a faunal boundary that separates the [[Indomalayan realm]] from [[Wallacea]].<ref>{{cite journal |doi=10.1128/JVI.00723-16 |pmid=27384662 |pmc=5008096 |title=Endogenous Gibbon Ape Leukemia Virus Identified in a Rodent (Melomys burtoni subsp.) from Wallacea (Indonesia) |journal=Journal of Virology |volume=90 |issue=18 |pages=8169–80 |year=2016 |last1=Alfano |first1=Niccolò |last2=Michaux |first2=Johan |last3=Morand |first3=Serge |last4=Aplin |first4=Ken |last5=Tsangaras |first5=Kyriakos |last6=Löber |first6=Ulrike |last7=Fabre |first7=Pierre-Henri |last8=Fitriana |first8=Yuli |last9=Semiadi |first9=Gono |last10=Ishida |first10=Yasuko |last11=Helgen |first11=Kristofer M |last12=Roca |first12=Alfred L |last13=Eiden |first13=Maribeth V |last14=Greenwood |first14=Alex D }}</ref> It is named for [[Alfred Russel Wallace]], who first observed the abrupt boundary between the two [[biomes]] in 1859. Biologists believe it was the depth of the Lombok Strait itself that kept the animals on either side isolated from one another.  However, it has been found that some flightless animals such as certain weevil species have, in the past, been involved in several transgression events in which species from land east of the Wallace Line relocated to Bali.<ref>{{cite journal |doi=10.1098/rspb.2013.2528 |pmid=24648218 |pmc=3973253 |title=Multiple transgressions of Wallace's Line explain diversity of flightless Trigonopterus weevils on Bali |journal=Proceedings of the Royal Society B: Biological Sciences |volume=281 |issue=1782 |pages=20132528 |year=2014 |last1=Tanzler |first1=R |last2=Toussaint |first2=E. F. A |last3=Suhardjono |first3=Y. R |last4=Balke |first4=M |last5=Riedel |first5=A }}</ref> When sea levels dropped during the [[Pleistocene]] [[ice age]], the islands of Bali, [[Java (island)|Java]] and [[Sumatra]] were all connected to one another and to the mainland of [[Asia]].  They shared the Asian fauna.  The Lombok Strait's deep water kept Lombok and the [[Lesser Sunda Islands|Lesser Sunda archipelago]] isolated from the Asian mainland.  These islands were, instead, colonized by Australasian fauna.
* [[Mbam Djerem National Park]]'s ecotone in [[Cameroon]] is up to 1,000&nbsp;km wide in places and differences within species are believed to be precursors to [[speciation]].<ref>{{cite magazine|magazine=New Scientist|date=11 June 2016|author=Steve Nadis|title=Life on the edge}}</ref>
* General examples of ecotones include [[salt marsh]]es and [[riparian zone]]s.

==See also==
{{portal|Ecology|Biology|Environment}}
* [[Cline (biology)]] - ''Ecocline''
* [[Ecotype]]
* [[Phylogenetic niche conservatism]]
* [[Plant functional type]]
* [[Satoyama]]
* [[Biogeographic realm]]

==References==
{{reflist}}

==External links==
{{wiktionary}}

{{modelling ecosystems|expanded=none}}

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[[Category:Landscape ecology]]
[[Category:Habitats]]
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[[Category:Biogeography]]
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