Transcript Histosols
Histosols Get their name from the Greek word histos meaning tissue http://passel.unl.edu/Image/mmamo3/TimK ettler/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 Histic Epipedon is made up of a O horizon 2060cm 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 •Limnic Haplosaprist, southern Michigan http://soils.cals.uidaho.edu/SoilORDERS/histosols_02.htm • Typic Haplosaprist, northern Idaho Photos Subsidence in drained Histosol, Everglades, Florida http://soils.cals.uidaho.edu/SoilORDERS/histosols_06.htm http://soils.cals.uidaho.edu/SoilORDERS/histosols_04.htm Photo • Lithic Torrifolist, southern Idaho http://soils.cals.uidaho.edu/SoilORDERS/histosols_09.htm