Spodosol Also known as Podsol (also spelled Podzol) is the typical soil of coniferous, or Boreal forests. The name is Russian for "under ash" (pod=under, zola=ash)
Spodosols are acid soils characterized by a subsurface accumulation of humus that is complexed with Al and Fe. These photogenic soils typically form in coarse-textured parent material and have a light-colored E horizon overlying a reddish-brown spodic horizon. The process that forms these horizons is known as podzolization.
Many Spodosols support forest. Because they are naturally infertile, Spodosols require additions of lime in order to be productive agriculturally.
Spodosols often occur under coniferous forest in cool, moist climates. Globally, they occupy ~4% of the ice-free land area. In the US, they occupy ~3.5% of the land area.
Aquods - poorly drained Spodosols with a water table at or near the surface for much of the year. Formed mainly in sandy materials of Pleistocene age in any temperature regime. Water loving plants of a very wide variety, ranging from sphagnum in cold areas, to palms in the tropics, grow on these soils.
Gelods - Spodosols of very cold cimates (mean annual soil temperature <0°C)
Cryods - Spodosols of high latitude or high elevations. In the US, they occur in southeast Alaska, and in the mountains of Washington and Oregon. Some are found in the mountians of northern New England. Many formed in volcanic as or glacial drift. High organic carbon content is often found in the soil horizon. Vegetation supported is mostly coniferous forest or alpine tundra.
Humods - well-drained Spodosols that contain relatively large quantities of organic matter. Formed predominantly in Pleistocene or Holocene deposits. In the US, these soils developed under a coniferous forest, and in western Europe, commonly found in sandy materials where heather is or used to be dominant. In the tropics, most Humods have supported a rain forest. Not extensive in the US, they are known in Maine and the Pacific Northwest and may occur in the Southeast.
Orthods - common Spodosols that are the most common Spodosols in the northern parts of Europe and in the US. Formed predominantly in course, acid Pleistocene or Holocene deposits under a mostly coniferous forest vegetation. The soil temperature regimes range from frigid to hyperthermic. Orthods are extensive in the southeastern part of the US, the Northeast, the Great Lakes States and the mountains of the West.