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Patch dynamics is a conceptual approach to ecosystem and habitat analysis that emphasizes dynamics of heterogeneity within a system (i.e. that each area of an ecosystem is made up of a mosaic of small 'sub-ecosystems'). Diverse patches of habitat created by natural disturbance regimes are seen as critical to the maintenance of this diversity (ecology). A ''habitat patch'' is any discrete area with a definite shape, spatial and configuration used by a species for breeding or obtaining other resources. ''Mosaics'' are the patterns within landscapes that are composed of smaller elements, such as individual forest stands, shrubland patches, highways, farms, or towns. == Patches and mosaics == Historically, due to the short time scale of human observation, mosaic landscapes were perceived to be static patterns of human population mosaics. This focus centered around the idea that the status of a particular population, community, or ecosystem could be understood by studying a particular patch within a mosaic. However, this perception ignored the conditions that interact with, and connect patches. In 1979, Bormann and Likens coined the phrase ''shifting mosaic'' to describe the theory that landscapes change and fluctuate, and are in fact dynamic. This is related to the battle of cells that occurs in a Petri dish. ''Patch dynamics'' refers to the concept that landscapes are dynamic.〔 There are three states that a patch can exist in: ''potential'', ''active'', and ''degraded''. Patches in the ''potential'' state are transformed into active patches through colonization of the patch by dispersing species arriving from other ''active'' or ''degrading'' patches. Patches are transformed from the ''active'' state to the ''degraded'' state when the patch is abandoned, and patches change from ''degraded'' to ''potential'' through a process of recovery.〔 〕 Logging, fire, farming, and reforestation can all contribute to the process of colonization, and can effectively change the shape of the patch. ''Patch dynamics'' also refers to changes in the structure, function, and composition of individual patches that can, for example, effect the rate of nutrient cycling. Patches are also linked, although separated from other patches, migration occurs from one patch to another. This migration maintains the population of some patches, and can be the mechanism by which some plant species spread. This implies that ecological systems within landscapes are open, rather than closed and isolated. (Pickett, 2006) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「patch dynamics」の詳細全文を読む スポンサード リンク
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