Patch dynamics is an ecological perspective that the structure, function, and dynamics of ecological systems can be understood through studying their interactive patches. Patch dynamics, as a term, may also refer to the spatiotemporal changes within and among patches that make up a landscape. Patch dynamics is ubiquitous in terrestrial and aquatic systems across organizational levels and spatial scales. From a patch dynamics perspective, populations, communities, ecosystems, and landscapes may all be studied effectively as mosaics of patches that differ in size, shape, composition, history, and boundary characteristics. The idea of patch dynamics dates back to the 1940s when plant ecologists studied the structure and dynamics of vegetation in terms of the interactive patches that it comprises. A mathematical theory of patch dynamics was developed by Simon Levin and Robert Paine in the 1970s, originally to describe the pattern and dynamics of an intertidal community as a patch mosaic created and maintained by tidal disturbances. Patch dynamics became a dominant theme in ecology between the late 1970s and the 1990s. Patch dynamics is a conceptual approach to

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

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 on the idea that the status of a particular

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

community A community is a social unit (a group of people) with a shared socially-significant characteristic, such as place, set of norms, culture, religion, values, customs, or identity. Communities may share a sense of place situated in a given g ...

, or

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 475px, Map of the year each country achieved List of sovereign states by date of formation, independence. Colonization (British English: colonisation) is a process of establishing occupation of or control over foreign territories or peoples f ...

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 ''active'' 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, affect the rate of

nutrient cycling A nutrient cycle (or ecological recycling) is the movement and exchange of inorganic and organic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cyc ...

. Patches are also linked. Although patches may be separated in space, migration can occur 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)

Conservation efforts

Recognizing the patch dynamics within a system is needed for conservation (ecology) efforts to succeed. Successful conservation includes understanding how a patch changes and predicting how they will be affected by external forces. These externalities include natural effects, such as

land use Land use is an umbrella term to describe what happens on a parcel of land. It concerns the benefits derived from using the land, and also the land management actions that humans carry out there. The following categories are used for land use: fo ...

, disturbance, restoration, and succession, and the effects of human activities. In a sense, conservation is the active maintenance of patch dynamics (Pickett, 2006). The analysis of patch dynamics could be used to predict changes in biodiversity of an ecosystem. When patches of species can be tracked, it has been shown that fluctuations on the biggest patch (the most dominant species) can be used as an early warning of a

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

collapse. That means that if external conditions, like

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

and

habitat fragmentation Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological proces ...

, change the internal dynamics of patches, a sharp reduction in biodiversity can be detected before it is produced.

Patches and mosaics

Conservation efforts

See also

References

Further reading