Ecotone
An ecotone is a transitional zone between two different ecosystems, characterized by the presence of species and features from both bordering communities, as well as unique organisms that may not be found in either. These areas can vary in size from just a few centimeters to thousands of kilometers and can exist in both terrestrial and aquatic environments. Ecotones arise from various natural factors, such as soil composition and topography, as well as human activities like deforestation and urban development. They are known for exhibiting high biodiversity and are often distinguished by a phenomenon called the "edge effect," where species thrive due to the diverse resources available. Historically defined in the early 20th century, ecotones have gained attention for their ecological significance, particularly in understanding climate change and species conservation. Current research on ecotones aims to enhance our knowledge of ecological interactions and improve conservation strategies, as these zones can serve as critical pathways for species and nutrients between ecosystems. Consequently, studying ecotones is essential for addressing environmental challenges and maintaining biodiversity in a changing world.
Ecotone
An ecotone is the transitional boundary between two ecosystems. In most cases, ecotones contain elements of both bordering ecosystems and unique plant and animal species not found in either bordering ecosystem. Ecotones occur on varying scales, ranging from broad zones where one ecological community gradually transitions into another to narrower boundaries where the change from one ecosystem to the next is defined more sharply. Consequently, the spatial size of ecotones may vary from mere centimeters to thousands of kilometers. In addition, ecotones occur in both terrestrial and aquatic communities. First formally defined by environmental scientists in the early twentieth century, ecotones continue to be an intriguing subject of study that some modern ecologists believe could yield critical information about the effects of global climate change.
Causes and Types
Ecotones result from both natural and man-made causes. Some natural causes of ecotones include soil mineral content, soil salinity, pH, and topographical and meteorological transition zones. Naturally occurring ecotones also may result from floods, fires, or volcanic activity. Man-made ecotones result from human activities such as soil pollution, controlled burning, forest clearing, and over-drafting of groundwater.
Three basic types of ecotones are directional ecotones, shifting ecotones, and stationary ecotones. Directional ecotones change in a unidirectional fashion over time. Shifting ecotones exhibit relatively little change over long periods. Stationary ecotones generally remain stable over long periods.
Characteristics
Ecotones may occur in any area where two ecosystems or plant communities meet. Naturally occurring ecotones include forest/grassland, grassland/desert, tundra/forest, forest/marsh, land/salt water, land/freshwater, groundwater/surface water, and forest riparian zones. Anthropogenic ecotones, or ecotones that arise from human activities, include everything from agricultural-pastoral boundaries to urban-rural spaces and more.
Most ecotones exhibit a number of key characteristics. At the simplest and most easily observable level, an ecotone usually differs in overall appearance from either of the distinct ecological communities it borders. Among other things, plant height is one visual element that typically distinguishes ecotones from their neighboring ecological communities.
More often than not, ecotones tend to have a greater degree of biodiversity, with a larger number of species and a greater population density than either of the ecosystems they border. This trend is known as the edge effect. Accordingly, those species that live predominantly or most abundantly in ecotones typically are referred to as edge species. Some edge species may even exist in an ecotone exclusively and might not be found in the bordering ecological communities at all. Others may simply rely on ecotones as a place to conduct important biological activities such as mating, nesting, or foraging. Typically, species that do not require a high degree of stability or habitat continuity are most likely to thrive in an ecotone. Abiotic factors affected by ecotones, such as sediment deposition, erosion, snow accumulation, salinity, and nutrient availability, also tend to determine which species will thrive in a given ecotone.
Generally, most ecotones exhibit a conspicuous variability in vegetation. Often plant species that flourish on one side of an ecotone will not fare as well on the opposite side. Exotic species also are known to be especially common in ecotones.
History
Ecotones were first described in the early twentieth century by Burton Edward Livingston and Frederic Clements, a pair of scientists who specialized in what was then the newly emergent field of ecology. Livingston, in a 1903 study of the plant life of Kent County, Michigan, was the first to describe the existence of transitional zones found between different plant communities. Two years later, Clements coined the term ecotone and formally defined it as "the line that connects the points of accumulated or abrupt change in the symmetry [of a habitat]." In the 1930s, Aldo Leopold invented the term edge effects and suggested that many species were attracted to the edges of ecological communities, or ecotones, because of the broader variety of resources available in these areas. From there, many scientists further expanded upon the concept of ecotones by studying specific transitional zones and documenting their unique characteristics. Today ecotones remain an engaging subject of study for ecologists around the world.
Ecotones and the Modern World
In the future, the study of ecotones may help humans to conserve endangered plant and animal species and develop a refined understanding of climate change. Studies have shown that ecotones may play a key role in enabling the exchange of various plant and animal species, as well as important nutrients, between separate ecological communities. Scientists also know that the specific characteristics of an ecotone can improve or diminish the broader permeability of a landscape and that plant and animal species interact with ecotones in many ways on different scales. Therefore, by conducting further studies aimed at strengthening understanding of how various plant and animal species interact with ecotones, scientists can perhaps learn how best to conserve and manage endangered species.
The continued study of ecotones also may prove essential to dealing with the problem of global climate change. Because ecotones are often especially sensitive to the effects of climate change, scientists can observe these transitional zones to learn more about the specific patterns and consequences of climate change and perhaps even develop methods to minimize the harmful effects of the global climate crisis.
Bibliography
Graves, Rose, and Deane Wang. "Ecotone." The Encyclopedia of Earth. The Encyclopedia of Earth, 13 Mar. 2011. Web. 18 Feb. 2016. http://www.eoearth.org/view/article/152345/
Myster, Randall W., ed. Ecotones Between Forest and Grassland. New York: Springer Science+Business Media, 2012. Print.
Solomon, Eldra P., et al. "Ecotones." Biology. 7th ed. Belmont, CA: Brooks/Cole - Thomson Learning, 2005. Print.
Walker, Susan J., et al. "Properties of Ecotones: Evidence from Five Ecotones Objectively Determined from a Coastal Vegetation Gradient." Journal of Vegetation Science. IAVS; Opulus Press Uppsala, 2003: 579–590. Web. 18 Feb. 2016. http://onlinelibrary.wiley.com/doi/10.1111/j.1654-1103.2003.tb02185.x/epdf