How such ecosystems are different than fragile ecosystems . Can be asked to any reputed ecological science experts .
Running water ecosystems (riverine or marine) are inherently dynamic, both physically and biologically. For example, running water ecosystems are constantly perturbed by changes in catchment geomorphology and land-use, local physico-chemical parameters, and changes in timings of extreme events relative to the normal seasonal cycle. Again, although extreme events may generally viewed as one end of a gradient of fluctuations, anthropogenic influences are increasingly altering their intensity, frequency and duration, with potentially dramatic consequences for running
waters. It has been more intensified under ongoing changing climatic regime and mutiple stressors interactions and impacts on the running water ecosystem.
What about terrestrial ecosystems ? As far as I understand there is great difference in perturbation department ecosystems and fragile ecosystems. People without knowing structure and functions of a particular degraded ecosystem just use to terms such ecosystem as fragile ecosystem.
Perturbation-dependent, also known as disturbance-dependent, require certain types, frequencies, and severities of disturbance in order to persist or to maintain or provide certain ecological functions. Probably the best-known perturbation dependent ecosystems are the ones that depend on fire, such as many dry forests and savannas around the world. In the absence of fire, species composition often changes from a dominance of species that are fire-adapted to a dominance of species that are fire sensitive. Stand density often increases as well. The system often changes from one that typically experienced frequent, low severity fire to one that experiences infrequent, high severity fire. Many streams are dependent on periodic influxes of sediment and downed wood in order to maintain healthy fish habitat by providing nutrients and rearranging the pool:riffle ratio. Perturbation-dependent systems may or may not also be fragile systems, but usually are not considered fragile in the sense that key characteristics or functions are easily lost. The sagebrush steppe in the US Great Basin can be divided into parts that are perturbation dependent and fragile. The higher elevation sagebrush steppe is fire-dependent with fire needed to keep conifers from encroaching and taking dominance. The lower elevation sagebrush steppe is fragile in that it is easily invaded by exotic annual grasses that burn more readily and frequently, preventing a return to the native plant community. High interannual variability in precipitation and low precipitation amounts makes the lower elevation sagebrush steppe very difficult to restore, whereas the higher elevation sagebrush steppe can be restored relatively easily by removing the conifers and returning fire as an ecosystem process.
Thank you very much Lousia for such a clearcut examples to draw a line between fragile and perturbation dependent ecosystems . Great ! Your reply is very educative . Regards.
Dear Sir,
Please have a look at this useful link and PDF attachment for insights.
https://academic.oup.com/bioscience/article/49/3/193/242486/How-Ecosystems-Respond-to-StressCommon-properties