<P> Other factors can illustrate or obscure an ecotone, for example, 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 exotic species in an ecotone can reveal the type of biome or efficiency of the two communities sharing space . 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 . </P> <P> Changes in the physical environment may produce a sharp boundary, as in the example of the interface between areas of forest and 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 ranges often create such ecotones, due to the wide variety of climatic conditions experienced on their slopes . 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 wetlands 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 . </P> <P> 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 habitats 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 . 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 niches . </P> <P> 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: pH or salinity gradient), or microclimatically (hydrothermal gradient) between two ecosystems . </P>

Why is the greatest number of species found in the ecotone