Get their name from the Greek word histos meaning tissue Histosols http://passel.unl.edu/Image/mmamo3/TimKettler/histosolsLG.gif
General Characteristics • Dark soils, without permafrost, made up of accumulated organic matter which ranges from slightly to well decomposed. • Decomposition is slowed due to wet or cold conditions. • Contain at least 20-30% organic matter by weight and are more than 40 cm thick. • Organics include: sedges, grasses, leaves, hydrophytic plants and woody materials. • Soil acts as a sponge and remain saturated for most of their existence.
General Characteristics cont. • Form many areas of valuable wetlands. • Poorly decomposed Histosols- Peat - used in greenhouses and nurseries. • Well decomposed Histosols- Muck – used for specialized farming(vegetables, turf) • Highly porous(>85% pore space by volume) causing high rates of subsidence(~1ft/year ) when drained and tilled.
Diagnostic Horizons • Histosols diagnostic feature is its Histic or Folic Epipedon. • A HisticEpipedon is made up of a O horizon 20-60cm thick above mineral soil. • Subdivided by degree of decomposition • Oi- fibric - least decomposed • Oe- hemic – moderate decomposition • Oa- sapric – most decomposed • A Folic Epipedon is similar to Histic except it remains freely drained and is underlain by fragmented rock within 15cm of the surface.(Alpine regions)
Typical Environments • Formed by topographic elements; usually in wet, cool, low-lying areas such as basins, depressions, swamps, coastal marshes, deltas, and areas with a high precipitation to evapotranspiration ratio. • Can be found in variety of regions; from Alpine where low temperatures slow organic decay to the tropical islands(10% of all Histosols) where soil remain saturated.
Distribution (World) • Covers ~1.2% of ice free land area of the world(325 - 375 million hectares). • Majority is located in the boreal, subarctic and low arctic regions of the Northern Hemisphere. • Can be found in the U.S. and Canada, western Europe, and northern Scandinavia, and in northern regions east of the Ural mountain range.
Distribution (U.S.) • Can be found scattered throughout northern MN, WI, MI, and upstate NY; as well as all along the southeastern coastline of the U.S. (Mississippi delta, Florida Everglades) • Covers ~1.6% of the U.S. land area.
Distribution (MN) • Histosols occupy ~5.3 % of Minnesota or about 3 million acres. • Most extensive in the north, in areas where glacial lakes used to be.
Photos • Lower Coastal Plain,North Carolina http://soils.cals.uidaho.edu/SoilORDERS/histosols_01.htm • LimnicHaplosaprist,southern Michigan http://soils.cals.uidaho.edu/SoilORDERS/histosols_02.htm
Photos Subsidence in drained Histosol,Everglades, Florida • TypicHaplosaprist,northern Idaho http://soils.cals.uidaho.edu/SoilORDERS/histosols_06.htm http://soils.cals.uidaho.edu/SoilORDERS/histosols_04.htm
Photo • LithicTorrifolist,southern Idaho http://soils.cals.uidaho.edu/SoilORDERS/histosols_09.htm