Spodosols (from the Greek spodos – wood ash) are among the most attractive soils. They often have a dark surface underlain by an ashy, gray layer, which is subsequently underlain by a reddish, rusty, coffee-colored, or black subsoil horizon.
These soils form as rainfall interacts with acidic vegetative litter, such as the needles of conifers, to form organic acids. These acids dissolve iron, aluminum, and organic matter in the topsoil and ashy gray (eluvial) horizons. The dissolved materials then move (illuviate) to the colorful subsoil horizons.
Spodosols most often develop in coarsely textured soils (sands and loamy sands) under coniferous vegetation in humid regions of the world. They tend to be acidic, and have low fertility and low clay content.
Spodosols occupy about 4% of the world’s glacier-free land surface.