1 activity that is an intrusion or interruption; "he looked around for the source of the disturbance"; "there was a disturbance of neural function" [syn: perturbation]
2 an unhappy and worried mental state; "there was too much anger and disturbance"; "she didn't realize the upset she caused me" [syn: perturbation, upset]
3 a disorderly outburst or tumult; "they were amazed by the furious disturbance they had caused" [syn: disruption, commotion, stir, flutter, hurly burly, to-do, hoo-ha, hoo-hah, kerfuffle]
5 the act of disturbing something or someone; setting something in motion
6 (psychiatry) a psychological disorder of thought or emotion; a more neutral term than mental illness [syn: mental disorder, mental disturbance, psychological disorder, folie]
act of disturbing, being disturbed
- Hebrew: הפרעה (hafra'a)
In ecology, a disturbance is a temporary change in average environmental conditions that causes a pronounced change in an ecosystem. Outside disturbance forces often act quickly and with great effect, sometimes resulting in the removal of large amounts of biomass. Ecological disturbances include fires, flooding, windstorm, insect outbreaks, as well as anthropogenic disturbances such as forest clearing and the introduction of exotic species. Disturbances can have profound immediate effects on ecosystems and can, accordingly, greatly alter the natural community. Because of these and the impacts on populations, these effects can continue for an extended period of time.
Specific conditions are often required for disturbances. With natural disturbances such as fire and flooding, conditions are influenced mainly by climate, weather, and location. Spruce, fir, and younger pines, which are unaffected by the beetles, thrive in canopy openings. Eventually pines grow into the canopy and replace those lost. Younger pines are often able to ward off beetle attacks but, as they grow older, pines become less vigorous and more susceptible to infestation. This cycle of death and re-growth creates a temporal mosaic of pines in the forest. Similar cycles occur in association with other disturbances such as fire and windthrow.
Species adapted to disturbance
A disturbance changes forests significantly. Afterwards, the forest floor is often littered with dead material. This decaying matter and abundant sunlight promote an abundance of new growth. In the case of forest fires a portion of the nutrients previously held in plant biomass is returned quickly to the soil as biomass burns. Many plants and animals benefit from the conditions created by disturbances.
Some species are particularly suited for exploiting recently disturbed sites. Vegetation with the potential for rapid growth can quickly take advantage of the lack of competition. In the northeastern United States, shade-intolerant trees like pin cherry and aspen quickly fill in forest gaps created by fire or windthrow (or human disturbance). Silver maple and eastern sycamore are similarly well adapted to floodplains. They are highly tolerant of standing water and will frequently dominate floodplains where other species are periodically wiped out.
Another species which is well adapted to a particular disturbance is the Jack Pine in boreal forests exposed to crown fires. They, as well as some other pine species, have specialized serotinous cones that only open and disperse seeds with sufficient heat generated by fire. As a result, this species often dominates in areas where competition has been reduced by fire.
Species that are well adapted for exploiting disturbance sites are referred to as pioneers or early successional species. These shade-intolerant species are able to photosynthesize at high rates and as a result grow quickly. Their fast growth is usually balanced by short life spans. Furthermore, although these species often dominate immediately following a disturbance, they are unable to compete with shade-tolerant species later on and replaced by these species through succession.
While plants must deal directly with disturbances, animals are not as heavily affected by them. Most animals can successfully evade fires, and many thrive afterwards on abundant new growth on the forest floor. New conditions support a wider variety of plants, often rich in nutrients compared to pre-disturbance vegetation. The plants in turn support a variety of wildlife, temporarily increasing biological diversity in the forest.
disturbance in Estonian: Häiritus (ökoloogia)
disturbance in Japanese: 擾乱
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