Edge effects

Source: Wikipedia, the free encyclopedia.

In ecology, edge effects are changes in population or community structures that occur at the boundary of two or more habitats.[1] Areas with small habitat fragments exhibit especially pronounced edge effects that may extend throughout the range. As the edge effects increase, the boundary habitat allows for greater biodiversity.

Urbanization is causing humans to continuously fragment landscapes and thus increase the edge effect. This change in landscape ecology is proving to have consequences.[2] Generalist species, especially invasive ones, have been seen to benefit from this landscape change whilst specialist species are suffering.[3] For example, the alpha diversity of edge-intolerant birds in Lacandona rainforest, Mexico, is decreasing as edge effects increase.[4]

Edges arise where two or more habitat types come into contact as here in Pennsylvania, United States.

Types

  • Inherent – Natural features stabilize the border location.
  • Induced – Transient natural disturbances (e.g., fire or flood) or human related activities, subject borders to successional changes over time.
  • Narrow – One habitat abruptly ends and another begins (e.g., an agricultural field.)
  • Wide (ecotone) – A large distance separates the borders of two clearly and purely definable habitats based upon their physical conditions and vegetation, and in between there exists a large transition region.
  • Convoluted – The border is non-linear.
  • Perforated – The border has gaps that host other habitats.

Height can create borders between patches as well.[5]

Biodiversity

Environmental conditions enable certain species of plants and animals to colonize habitat

cottontail rabbits, blue jays, and robins.[citation needed] Some animals travel between habitats, while edge species are restricted to edges. Larger patches have increased native species biodiversity compared to smaller patches.[7]
The width of the patch also influences diversity: an edge patch must be more pronounced than just a stark border in order to develop gradients of edge effects.

Animals traveling between communities can create travel lanes along borders, which in turn increases light reaching plants along the lanes and promotes primary production. As more light reaches the plants, greater numbers and sizes can thrive. Increased primary production can increase numbers of herbivorous insects, followed by nesting birds and so on up the trophic levels.

In the case of wide and/or overgrown borders, some species can become restricted to one side of the border despite having the ability to inhabit the other. Sometimes, the edge effects result in

abiotic
and biotic conditions which diminish natural variation and threaten the original ecosystem. Detrimental edge effects are also seen in physical and chemical conditions of border species. For instance, fertilizer from an agricultural field could invade a bordering forest and contaminate the habitat. The three factors affecting edges can be summarized:

  • Abiotic effect—Changes in the environmental conditions that result from the proximity to a structurally dissimilar matrix
  • Direct biological effects—Changes in
    species abundance
    and distribution caused directly by physical conditions near the edge
  • Indirect biological effects which involve changes in species interactions such as
    herbivory, and biotic pollination and seed dispersal[9]

Human effects

Human activity creates edges through development and agriculture. Often, the changes are detrimental to both the size of the habitat and to species. Examples of human impacts include:

Examples

When edges divide any

vapor pressure deficit, soil moisture, light intensity and levels of photosynthetically active radiation
(PAR) all change at edges.

Amazon rainforest

One study estimated that the amount of

Amazon Basin area modified by edge effects exceeded the area that had been cleared.[10] "In studies of Amazon forest fragments, micro-climate effects were evident up to 100m (330ft.) into the forest interior."[11] The smaller the fragment, the more susceptible it is to fires spreading from nearby cultivated fields. Forest fires are more common close to edges due to increased light availability that leads to increased desiccation and increased understory growth. Increased understory biomass provides fuel that allows pasture fires to spread into the forests. Increased fire frequency since the 1990s is among the edge effects that are slowly transforming Amazonian forests. The changes in temperature, humidity and light levels promote invasion of non-forest species, including invasive species. The overall effect of these fragment processes is that all forest fragments tend to lose native biodiversity depending on fragment size and shape, isolation from other forest areas, and the forest matrix.[11]

North America

The amount of

poison ivy. [13]

Conversely,

Douglas-fir
all thrive in edge habitats.

In the case of developed lands juxtaposed to wild lands, problems with

multiflora rose have damaged natural ecosystems. Beneficially, the open spots and edges provide places for species that thrive where there is more light and vegetation that is close to the ground. Deer and elk benefit particularly[citation needed
] as their principal diet is that of grass and shrubs which are found only on the edges of forested areas.

Effects on succession

Edge effects also apply to succession, when vegetation spreads rather than losing to competitors. Different species are suited either to the edges or to central sections of the habitat, resulting in a varied distribution. Edges also vary with orientation: edges on the north or south receive less or more sun than the opposite side (depending on hemisphere and convex or concave relief), producing varying vegetation patterns.

Other usage

The phenomenon of increased variety of plants as well as animals at the community junction (ecotone) is also called the edge effect and is essentially due to a locally broader range of suitable environmental conditions or ecological niches.

Edge effects in

biological assays refer to artifacts in data that are caused by the position of the wells on a screening plate rather than a biological effect.[citation needed
]

The edge effect in

scanning electron microscopy is the phenomenon in which the number of secondary and/or backscattered electrons that escape the sample and reach the detector is higher at an edge than at a surface. The interaction volume spreads far below the surface, but secondary electrons can only escape when close to the surface (generally about 10 nm, although this depends on the material). However, when the electron beam impacts an area close to the edge, electrons that are generated below an impact point that is close to an edge but that is far below the surface may be able to escape through the vertical surface instead.[citation needed
]

See also

References

  1. ISBN 9780691128399
    .
  2. S2CID 13546312. Archived
    from the original on 2023-07-31. Retrieved 2022-04-01.
  3. doi:10.1016/j.biocon.2004.06.005. Archived
    from the original on 2022-01-20. Retrieved 2022-04-01.
  4. doi:10.1016/j.biocon.2015.01.014. Archived
    from the original on 2022-06-19. Retrieved 2022-04-01.
  5. ^ Smith, T.M.; Smith, R.L. (2009). "Elements of Ecology": 391–411. {{cite journal}}: Cite journal requires |journal= (help)
  6. JSTOR 1942167. Archived
    from the original on 2023-02-14. Retrieved 2023-02-14.
  7. S2CID 8683460
    .
  8. S2CID 91309233
    .
  9. PMID 21236953. Archived
    from the original on 2023-07-31. Retrieved 2011-12-06.
  10. S2CID 12853752
    .
  11. ^
    ISBN 978-1-4443-3254-4.{{cite book}}: CS1 maint: location (link) CS1 maint: multiple names: authors list (link
    )
  12. S2CID 2775157. Archived
    from the original on 2023-07-31. Retrieved 2023-02-14.
  13. ISSN 1523-1739. Archived from the original
    on 2021-01-31. Retrieved 2021-01-27.

External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Edge_effects&oldid=1171087890"