Patch dynamics

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 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').[1]

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.[2] This focus centered on 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.[1] 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.[3]

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.

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, 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 collapse [4]. That means that if external conditions, like climate change and habitat fragmentation, change the internal dynamics of patches a sharp reduction in biodiversity can be detected before it is produced [4][5].

See also

References

  1. ^ a b Pickett, Steward T.A.; White, P.S. (1985). The Ecology of Natural Disturbance and Patch Dynamics. Academic Press. ISBN 0123960215.
  2. ^ Bogin, Barry (1999). Patterns of human growth (2nd ed.). Cambridge: Cambridge University Press. ISBN 9780521564380.
  3. ^ Wright, Justin P.; Gurney, W.S.C.; C.G., Jones (2004). "Patch dynamics in a landscape modified by ecosystem engineers" (PDF). OIKOS. 105: 336–348. ISSN 0030-1299. Archived from the original (PDF) on 2010-06-26.
  4. ^ a b Saravia, Leonardo A.; Momo, Fernando R. (2017-07-01). "Biodiversity collapse and early warning indicators in a spatial phase transition between neutral and niche communities". Oikos: n/a–n/a. doi:10.1111/oik.04256. ISSN 1600-0706.
  5. ^ Corrado, Raffaele (2014). "Early warning signals of desertification transitions in semiarid ecosystems". Physical Review E. 90 (6). doi:10.1103/physreve.90.062705.

Further reading

  • Forman, R.T.T. 1995. Land Mosaics: The Ecology of Landscapes and Regions. Cambridge University Press, Cambridge, UK.
  • Groom, Martha J., Meffe, Gary K., Carroll, Ronald. 2006. Principles of Conservation Biology, Third Edition. Mosaics and Patch Dynamics by Steward T.A. Pickett
  • Levin, S. A., and R. T. Paine. 1974. Disturbance, patch formation and community structure. Proceedings of the National Academy of Sciences (USA) 71:2744-2747.
  • Levin, S. A., T. M. Powell, and J. H. Steele, editors. 1993. Patch Dynamics. Springer-Verlag, Berlin.
  • Wu, J. G., and O. L. Loucks. 1995. From balance of nature to hierarchical patch dynamics: A paradigm shift in ecology. Quarterly Review of Biology 70:439-466.
  • Patch Dynamics [1]
Bacterivore

Bacterivores are free-living, generally heterotrophic organisms, exclusively microscopic, which obtain energy and nutrients primarily or entirely from the consumption of bacteria. Many species of amoeba are bacterivores, as well as other types of protozoans. Commonly, all species of bacteria will be prey, but spores of some species, such as Clostridium perfringens, will never be prey, because of their cellular attributes.

Copiotroph

A copiotroph is an organism found in environments rich in nutrients, particularly carbon. They are the opposite to oligotrophs, which survive in much lower carbon concentrations.

Copiotrophic organisms tend to grow in high organic substrate conditions. For example, copiotrophic organisms grow in Sewage lagoons. They grow in organic substrate conditions up to 100x higher than oligotrophs.

Decomposer

Decomposers are organisms that break down dead or decaying organisms, and in doing so, they carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and development. While the terms decomposer and detritivore are often interchangeably used, detritivores must ingest and digest dead matter via internal processes while decomposers can directly absorb nutrients through chemical and biological processes hence breaking down matter without ingesting it. Thus, invertebrates such as earthworms, woodlice, and sea cucumbers are technically detritivores, not decomposers, since they must ingest nutrients and are unable to absorb them externally.

Dominance (ecology)

Ecological dominance is the degree to which a taxon is more numerous than its competitors in an ecological community, or makes up more of the biomass.

Most ecological communities are defined by their dominant species.

In many examples of wet woodland in western Europe, the dominant tree is alder (Alnus glutinosa).

In temperate bogs, the dominant vegetation is usually species of Sphagnum moss.

Tidal swamps in the tropics are usually dominated by species of mangrove (Rhizophoraceae)

Some sea floor communities are dominated by brittle stars.

Exposed rocky shorelines are dominated by sessile organisms such as barnacles and limpets.

Equation-free modeling

Equation-free modeling is a method for multiscale computation and computer-aided analysis. It is designed for a class of complicated systems in which one observes evolution at a macroscopic, coarse scale of interest, while accurate models are only given at a finely detailed, microscopic, level of description. The framework empowers one to perform macroscopic computational tasks (over large space-time scales) using only appropriately initialized microscopic simulation on short time and small length scales. The methodology eliminates the derivation of explicit macroscopic evolution equations when these equations conceptually exist but are not available in closed form; hence the term equation-free.

Feeding frenzy

In ecology, a feeding frenzy occurs when predators are overwhelmed by the amount of prey available. For example, a large school of fish can cause nearby sharks, such as the lemon shark, to enter into a feeding frenzy. This can cause the sharks to go wild, biting anything that moves, including each other or anything else within biting range. Another functional explanation for feeding frenzy is competition amongst predators. This term is most often used when referring to sharks or piranhas. It has also been used as a term within journalism.

Kelp forest

Kelp forests are underwater areas with a high density of kelp, which covers about 25% of the world’s coastlines. They are recognized as one of the most productive and dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds.

Kelp forests occur worldwide throughout temperate and polar coastal oceans. In 2007, kelp forests were also discovered in tropical waters near Ecuador.Physically formed by brown macroalgae, kelp forests provide a unique, three-dimensional habitat for marine organisms and are a source for understanding many ecological processes. Over the last century, they have been the focus of extensive research, particularly in trophic ecology, and continue to provoke important ideas that are relevant beyond this unique ecosystem. For example, kelp forests can influence coastal oceanographic patterns and provide many ecosystem services.However, the influence of humans has often contributed to kelp forest degradation. Of particular concern are the effects of overfishing nearshore ecosystems, which can release herbivores from their normal population regulation and result in the overgrazing of kelp and other algae. This can rapidly result in transitions to barren landscapes where relatively few species persist. The implementation of marine protected areas is one management strategy useful for addressing such issues, since it may limit the impacts of fishing and buffer the ecosystem from additive effects of other environmental stressors.

Lithoautotroph

A lithoautotroph or chemolithoautotroph is a microbe which derives energy from reduced compounds of mineral origin. Lithoautotrophs are a type of lithotrophs with autotrophic metabolic pathways. Lithoautotrophs are exclusively microbes; macrofauna do not possess the capability to use mineral sources of energy. Most lithoautotrophs belong to the domain Bacteria, while some belong to the domain Archaea. For lithoautotrophic bacteria, only inorganic molecules can be used as energy sources. The term "Lithotroph" is from Greek lithos (λίθος) meaning "rock" and trōphos (τροφοσ) meaning "consumer"; literally, it may be read "eaters of rock". Many lithoautotrophs are extremophiles, but this is not universally so.

Lithoautotrophs are extremely specific in using their energy source. Thus, despite the diversity in using inorganic molecules in order to obtain energy that lithoautotrophs exhibit as a group, one particular lithoautotroph would use only one type of inorganic molecule to get its energy.

Mesotrophic soil

Mesotrophic soils are soils with a moderate inherent fertility. An indicator of soil fertility is its base status, which is expressed as a ratio relating the major nutrient cations (calcium, magnesium, potassium and sodium) found there to the soil's clay percentage. This is commonly expressed in hundredths of a mole of cations per kilogram of clay, i.e. cmol (+) kg−1 clay.

Metacommunity

An ecological metacommunity is a set of interacting communities which are linked by the dispersal of multiple, potentially interacting species. The term is derived from the field of community ecology, which is primarily concerned with patterns of species distribution, abundance and interactions. Metacommunity ecology combines the importance of local factors (environmental conditions, competition, predation) and regional factors (dispersal of individuals, immigration, emigration) to explain patterns of species distributions that happen in different spatial scales.

There are four theoretical frameworks, or unifying themes, that each detail specific mechanistic processes useful for predicting empirical community patterns. These are the patch dynamics, species sorting, source–sink dynamics (or mass effect) and neutral model frameworks. Patch dynamics models describe species composition among multiple, identical patches, such as islands. In this framework, species are able to persist on patches through tradeoffs in colonization ability and competitive ability, where less competitive species can disperse to unoccupied patches faster than they go extinct in others. Species sorting models describe variation in abundance and composition within the metacommunity due to individual species responses to environmental heterogeneity, such that certain local conditions may favor certain species and not others. Under this perspective, species are able to persist in patches with suitable environmental conditions resulting in a strong correlation between local species composition and the environment. This model represents the classical theories of the niche-centric era of G. Evelyn Hutchinson and Robert MacArthur. Source-sink models describe a framework in which dispersal and environmental heterogeneity interact to determine local and regional abundance and composition. This framework is derived from the metapopulation ecology term describing source–sink dynamics at the population level. High levels of dispersal among habitat patches allows populations to be maintained in environments that are normally outside the species environmental range. Finally, the neutral perspective describes a framework where species are essentially equivalent in their competitive and dispersal abilities, and local and regional composition and abundance is determined primarily by stochastic demographic processes and dispersal limitation. The neutral perspective was recently popularized by Stephen Hubbell following his groundbreaking work on the unified neutral theory of biodiversity.

Mycotroph

A mycotroph is a plant that gets all or part of its carbon, water, or nutrient supply through symbiotic association with fungi. The term can refer to plants that engage in either of two distinct symbioses with fungi:

Many mycotrophs have a mutualistic association with fungi in any of several forms of mycorrhiza. The majority of plant species are mycotrophic in this sense. Examples include Burmanniaceae.

Some mycotrophs are parasitic upon fungi in an association known as myco-heterotrophy.

Organotroph

An organotroph is an organism that obtains hydrogen or electrons from organic substrates. This term is used in microbiology to classify and describe organisms based on how they obtain electrons for their respiration processes. Some organotrophs such as animals and many bacteria, are also heterotrophs. Organotrophs can be either anaerobic or aerobic.

Antonym: Lithotroph, Adjective: Organotrophic.

Overpopulation

Overpopulation occurs when a species' population exceeds the carrying capacity of its ecological niche. It can result from an increase in births (fertility rate), a decline in the mortality rate, an increase in immigration, or an unsustainable biome and depletion of resources. When overpopulation occurs, individuals limit available resources to survive.

The change in number of individuals per unit area in a given locality is an important variable that has a significant impact on the entire ecosystem.

Owenia (plant)

Owenia is a genus of plants, mainly trees in the family Meliaceae. They are endemic to Australia and fairly widespread across the continent. There are five species in the genus, most from New South Wales and living in conditions ranging from wet rainforest to the verges of the desert. Like many plants, it plays its part in patch dynamics.

One species, Owenia cepiodora, is rare, and is renowned for having freshly cut bark that smells of onions. Its common name is onion cedar or bog onion.The species recognised at the Australian Plant Census include

Owenia acidula

Owenia cepiodora

Owenia reliqua

Owenia reticulata

Owenia vernicosa

Patch dynamics (physics)

Patch dynamics is a term used in physics to bridge, using algorithms, the models describing macroscale behavior and to predict large-scale patterns in fluid flow. It uses locally averaged properties of short space-time scales to advance and predict long space-time scale dynamics.

In patch dynamics and finite difference approximations, the macroscale variables are defined at the grid points of a mesh chosen to resolve the solution. The standard PDE adaptive grid methods can be used to resolve gradients in the macroscale solution. Both patch dynamics and finite difference methods generate time derivatives at mesh points; these time derivatives then help advance the solution in time.

Planktivore

A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton.

Recruitment (biology)

In biology, especially marine biology, recruitment occurs when a juvenile organism joins a population, whether by birth or immigration, usually at a stage whereby the organisms are settled and able to be detected by an observer.There are two types of recruitment: closed and open.In the study of fisheries, recruitment is "the number of fish surviving to enter the fishery or to some life history stage such as settlement or maturity".

Relative abundance distribution

In the field of ecology, the relative abundance distribution (RAD) or species abundance distribution describes the relationship between the number of species observed in a field study as a function of their observed abundance. The graphs obtained in this manner are typically fitted to a Zipf–Mandelbrot law, the exponent of which serves as an index of biodiversity in the ecosystem under study.

Windthrow

In forestry, windthrow or blowdown refers to trees uprooted or broken by wind.

Breakage of the tree bole (trunk) instead of uprooting is sometimes called windsnap.

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