EEB 4609W: Soil Horizons

O Horizon

Organic horizons, form above the mineral soil, derived from dead organisms, common in forests (“forest floor”). Oi ,fibric materials: recognizable plant remains (L, litter layer). Oe, hemic materials: fragmented and in the middle of decomposition (F, fermentation layer). Oa, sapric materials: very decomposed (H, humified layer).

A Horizon

Topmost mineral horizons, darkened by some decomposed organic material, often have coarse texture due to loss of finer materials to lower horizons.

E Horizon

Zones of maximum leaching or eluviation of clay, iron, and aluminum oxides, leavinging behind minerals that resist weathering like quartz; common in forests but rare in grasslands.

B Horizon

Zone of accumulation or illuviation from overlying horizons, accumulation of iron and aluminum oxides and silicate clays.

C Horizon

Unconsolidated rock beneath the “solum” (A,E, and B) layers, may or may not be parent material from which the solum formed, below the zone of greatest biological activity, relatively unaltered by soil development

R layers

Consolidated rock, with little evidence of weathering