Ecosystem Boundaries

Abstract

Ecosystem boundaries are zones of transitions between two adjacent habitats. They occur naturally in all biomes but the extent of boundaries has been greatly increased by anthropogenic habitat modification. Transition zones are characterized by a profound change in the composition of plant and animal communities and that transition may be abrupt, gradual or even occur via a series of intermediate habitat types. Naturally occurring ecosystem boundaries sometimes form a unique habitat to which species are specifically adapted, whereas anthropogenically created ecosystem boundaries typically contain a mixture of species from the two adjacent ecosystems and often exert a negative influence on natural habitats. Adjacent ecosystems are connected via flows of energy, material and organisms across ecosystem boundaries, and these flows can exert strong influences on the fertility and productivity of ecosystems. The magnitude of cross‐system fluxes is mediated by a wide range of variables.

Key concepts:

  • Ecosystem boundaries are the locations exhibiting gradients of change in environmental conditions and a related shift in the composition of plant and/or animal communities.

  • Naturally occurring ecosystem boundaries can represent unique habitats to which many species are specifically adapted.

  • Anthropogenically created ecosystem boundaries often support high species diversity, but the combination of species present at edges is very different to the one found deep inside the adjacent ecosystems.

  • Neighbouring ecosystems experience flows of organisms, materials and energy across the shared boundary.

Keywords: ecotone; edge effect; habitat edge; intertidal zone; spatial subsidy

Figure 1.

Examples of four ecosystem boundaries. (a) Natural ecosystem boundaries occur between a tropical evergreen and riparian forest, and between the riparian forest and the river that it borders. (b) Natural boundaries occur across the gradient from marine to intertidal to foreshore environments near the shore in temperate coastal regions. (c) Anthropogenic boundaries occur between the ginger plantation and the yam plantation, and between the latter and the tropical secondary forest. (d) Anthropogenic boundaries occur between a regenerating forest and an open field in a temperate region.

Figure 2.

Example of stunted forest vegetation at the boundary between a terrestrial and marine ecosystem. The architecture of the trees has been greatly altered by the environmental conditions at the ecosystem boundary, resulting in the stunted, windswept form that is commonly observed in coastal forests.

Figure 3.

Schematic representation of cross‐system flows between adjacent habitats in a tropical landscape disturbed by human use. Arrows represent the direction of cross‐system flows and arrow thickness represents the magnitude of edge effects. (a) Edge effects between a mature tropical forest and a clear‐cut area are very strong, whereas in (b) edge effects between mature and early successional forest are weaker. (c) Edge effects between early successional forest and unmaintained pasture are expected to be weak, as are those between (d) unmaintained pasture and a clear‐cut. (e) Edge effects between early successional forest and clear‐cut area are expected to be strong, although less than those between the clear‐cut and mature forest.

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Further Reading

Laurance WF and Bierregaard RO (1997) Tropical Forest Remnants: Ecology, Management, and Conservation of Fragmented Communities. Chicago: The University of Chicago Press.

Laurance WF, Didham RK and Power ME (2001) Ecological boundaries: a search for synthesis. Trends in Ecology and Evolution 16: 70–71.

Lindenmayer D and Fische J (2006) Habitat Fragmentation and Landscape Change: An Ecological and Conservation Synthesis. Washington: Island Press.

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How to Cite close
Banks‐Leite, Cristina, and Ewers, Robert M(Sep 2009) Ecosystem Boundaries. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0021232]