Semantic Scholar extracted view of "The meaning of stability." by Richard C. Lewontin. Author: Lewontin RC, Journal: Brookhaven symposia in biology. concerned with neighbourhood stability (Lewontin, ; May, ). In ecological useage the word stability has had two different meanings. Stability.
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State shifts via the community perspective have been induced experimentally by the addition or removal of predators, such as in Paine's work on keystone predators lewontin the meaning of stability.
Also, Beisner et al. Once a fish population falls below a certain threshold, it will inevitably go extinct when low population densities make replacement of adults impossible due to, for example, the inability to find mates or density-dependent mortality.
Since populations cannot return from extinction, this is an example of an irreversible state shift.
Although alternative stable state theory is still in its infancy, empirical evidence has been collected from a variety of biomes: The Sahara region, once vegetated, suddenly collapsed into a desert about 5, to 6, years ago due to climate lewontin the meaning of stability Scheffer and Carpenter Recent alteration of disturbance states via fire suppression has caused state shifts in fire-adapted ecosystems of the southeastern United States Peterson In the northeastern Lewontin the meaning of stability States alternative stable states have been experimentally documented in hardwood forest food webs Schmitz Spiders exhibit top-down control on generalist herbivore grasshoppers, causing them to hide in and forage on a competitively dominant plant species.
Herbivory on the superior plant competitor reduces dominance, thereby increasing plant diversity. Under experimental removal of spiders, grasshoppers were released from predation and consumed plants without preference for the competitively-superior species.
This top competitor outcompeted other species, resulting in lower overall plant diversity. Furthermore, reintroductions of spiders failed to return the system to high plant diversity, indicating ecological thresholds.
Ponds, lakes, and other small bodies of water are ideal for studying alternative stable states because they are relatively self-contained Holling There has been great interest in state shifts in shallow temperate lakes between clear-water and turbid-water states.
The meaning of stability. - Semantic Scholar
Nutrient loading can shift clear lakes to turbid systems by causing phytoplankton blooms Scheffer Feedbacks maintaining the turbid state include shading out benthic macrophytes, which otherwise stabilize sediments and reduce rapid nutrient cycling.
Hysteresis may occur if reductions in nutrient input do not return the clear-water state.
Alternative stable states have also been shown for freshwater faunal lewontin the meaning of stability. Ecological theory differentiates rainforest and open vegetation in many regions as functionally divergent alternative stable states with transitional ecotonal vegetation between the two forming transient unstable states.
Our study suggests that consumer density and identity are key in regulating both plant and animal community recovery and that physical conditions can determine the functional forms of these consumer effects.
The theory of these systems, known as multiple stable states, is well understood, but whether multiple stable states actually exist in nature has remained a hotly debated subject.
Resistance and inertia persistence [ edit ] Resistance and inertia deal with a system's inherent response to some perturbation.
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A perturbation is any externally imposed change in conditions, usually happening in a short time period. In ecological studies in the Lewontin the meaning of stability Islands, the presence and absence of dense sea otter populations can instigate state shifts between two alternately stable nearshore communities, one dominated by kelp and the other by sea urchins [11—13].
With sea otters present, sea urchins are reduced to sparse populations enabling kelps to flourish.