Epigeikusak

Epigeikusak is a term used in ecology to describe communities and organisms that inhabit the surface layer of the soil, especially the leaf litter and the uppermost soil horizon. They are contrasted with endogeic organisms that live primarily within the soil and hypogeic groups that dwell deeper.

Etymology and scope: Derived from the root epigeic (from Greek epi- upon and ge- earth), with plural form epigeikusak in certain languages. In English-language ecology the term is less common, and epigeic organisms or epigean biota are preferred. The concept helps describe functional groups based on vertical habitat rather than fixed taxonomy.

Ecology and function: Epigeikusak include a diverse set of organisms such as litter-dwellers, and some organisms that traverse the litter layer, including arthropods, mollusks, and epigeic earthworms (e.g., Eisenia fetida). They contribute to litter decomposition, nutrient cycling, and soil aggregation; their activity depends on moisture, temperature, and vegetation cover.

Distribution and research: These organisms are widespread in temperate and tropical ecosystems. Research on epigeikusak emphasizes microhabitat structure, trophic interactions, and responses to disturbance such as logging or fire.

See also: epigeic, endogeic, hypogeic, litter layer.