By Dr. Robert Norman, Clinical Professor, Dermatology, Nova Southeastern University
While hiking with my friend Ed along Cowhouse Creek, we noted a very clear transition between hardwood forest and the land bordering the creek. The forest land was filled with maples, pines, palmettos and sabal palms on high and dry land. We also saw fences and barbed wire, indicating the land had probably been used previously as a ranch or farm.
The land near the creek was muddy and populated with cypress knees and exposed cypress tree roots. We located several water locust trees (Gleditsia aquatica). The water locust or swamp locust has a habitat on river swamps and slough margins. It is a tree native to the Southeastern United States and adjacent regions.
An ecotone is an area that acts as a boundary or a transition between two ecosystems and is of great environmental importance. Because the area is a transition between two ecosystems or biomes, it is natural that it contains a large variety of species of fauna and flora as the area is influenced by both the bordering ecosystems. Most wetlands are ecotones.
Ecotones include marshlands (between dry and wet ecosystems), mangrove forests (between terrestrial and marine ecosystems), grasslands (between desert and forest), and estuaries (between saltwater and freshwater). Mountain ranges can also create ecotones due to the changes in the climatic conditions on the slopes.
An ecotone may be wide or narrow. It has conditions intermediate to the bordering ecosystem or could contain species that are entirely different from those found in the bordering systems.
Ecotones can be natural or man-made. An ecotone between an agricultural field and a forest is a man-made one.
I will outline three distinguishing features of an ecotone. First, an ecotone can have a sharp vegetation transition, with a distinct line between two communities. (1) 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. (2) 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, 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. The abundance of introduced species in an ecotone can reveal the type of biome or efficiency of the two communities sharing space. (3) 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.
What is the edge effect? Edge effects refer to the changes in population or community structures that occur at the boundary of two habitats. Generally, there is a greater number of species found in these regions (ecotones) and this is called the edge effect; the species found here are called edge species.
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.
What is the importance of ecotones?
– They have a greater variety of organisms.
– They also offer a good nesting place for animals coming in search of a nesting place or food.
– They serve as a bridge of gene flow from one population to another because of the larger genetic diversity present.
– They can act as buffer zones offering protection to the bordering ecosystems from possible damage. For example, a wetland can absorb pollutants and prevent them from seeping into the river.
– Ecotones are also a sensitive indicator of global climate change. A shifting of boundaries between ecosystems is thought to be due to climate change. Scientists and environmentalists are studying ecotones with greater interest now.
– Ecotones are an extremely important concept in the study of the environment and ecology—environment, climate change, and biodiversity. (4)
Where can you see ecotones?
Get out and see ecotones in The Great Florida Outdoors
1. The Editors of Encyclopedia Britannica. “Ecotone.” Encyclopedia Britannica
2. Janauer, G.A (1997). “Macrophytes, hydrology, and aquatic ecotones: A GIS-supported ecological survey”. Aquatic Botany. 58 (3–4): 379–91.
3. Walker, Susan; Wilson, J. Bastow; Steel, John B; Rapson, G.L; Smith, Benjamin; King, Warren McG; Cottam, Yvette H (2003). “Properties of ecotones: Evidence from five ecotones objectively determined from a coastal vegetation gradient”. Journal of Vegetation Science. 14 (4): 579–90.
4. UPSC GS 3 Notes: Ecotones
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