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Concept
Ephemerality
Résumé
Ephemerality (from the Greek word ἐφήμερος, meaning 'lasting only one day') is the concept of things being transitory, existing only briefly. Academically, the term ephemeral constitutionally describes a diverse assortment of things and experiences, from digital media to types of streams. "There is no single definition of ephemerality". With respect to unique performances, for example, it has been noted that "[e]phemerality is a quality caused by the ebb and flow of the crowd's concentration on the performance and a reflection of the nostalgic character of specific performances". Because different people may value the passage of time differently, ephemerality may be a relative, perceptual concept: "In brief, what is short-lived may not be the object itself, but the attention we afford it".
An ephemeral stream is that which only exists following precipitation. They are not the same as intermittent or seasonal waterbodies, which exist for longer periods, but not all year round. Ephemeral streams can be difficult to "conceptually defin[e]"; those that are discontinuous, due to altering between aggradation or degradation, have the appearance of continual change. Furthermore, the characteristics of terrain and rainfall are profound in affecting ephemeral streams. Ephemeral waterbodies experience formative change upon the end of a hydroperiod. "Due to lack of continuous hydrology data, the designation of sites as ephemeral or intermittent is necessarily tenuous". Ephemeral streams feature a low degree of hydrological connectivity.
Small wetlands are often ephemeral and ephemeral ecosystems are often aquatic; ephemeral wetlands, streams and ponds are a varied and global occurrence. In northeastern United States, ephemeral freshwater systems are abundant and are "critical to the maintenance of forest biodiversity". Hydroperiod, predation, competition and food availability are among the "highly heterogeneous" elements of these features.
Source officielle
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