View source for Mollisol

{{Short description|Nutrient-rich soil type}}
{{Infobox soil
| name                  = Mollisol
| alternative_name      = 
| type                  = 
| type_link             = 
| image                 = Mollisol.jpg
| image_size            = 200px
| image_caption         = A Mollisol profile
| horizons              = 
| composition_secondary = 
| classification_system = [[USDA soil taxonomy]]
| parent_material       = [[Loess]], [[Limestone]]
| climate               = [[humid continental climate|Humid continental]], [[semi-arid climate|semi-arid]]
}}

[[File:MollisolWorld.jpg|upright=1.6|thumb|Mollisols of the world]]
[[File:Grasslands-menggu.JPG|upright=1.6|thumb|Mollisols are generally associated with the [[steppe]] biome]]

'''Mollisol''' is a [[soil type]] which has deep, high organic matter, nutrient-enriched surface soil (a [[A horizon|horizon]]), typically between 60 and 80&nbsp;cm (24–31&nbsp;in) in depth. This fertile surface horizon, called a mollic epipedon, is the defining diagnostic feature of Mollisols. Mollic epipedons are created by long-term addition of organic materials derived from plant roots and typically have soft, granular soil structure.

Mollisols typically occur in savannahs and mountain valleys (such as Central Asia, and the North American [[Great Plains]]). These environments have historically been strongly influenced by fire and abundant [[pedoturbation]] from organisms such as ants and earthworms. It was estimated that in 2003, only 14 to 26 percent of grassland ecosystems remained in a relatively natural state (that is, they were not used for [[agriculture]] due to the fertility of the horizon). Globally, they represent ~7% of ice-free land area. As the world's agriculturally most productive soil order, the Mollisols represent one of the most economically important soil orders. 
 
Though most other soil orders known today were formed at the beginning of the [[Carboniferous]] [[Ice age|Ice Age]] 280 million years ago, Mollisols are best known from the [[paleopedological record]] possibly as early as the [[Maastrichtian]], though confidently found in the [[Eocene]].<ref>{{Cite journal |last=Bellosi1 Sciutto2 |first=Eduardo1 Juan C.2 |date=January 2002 |title=Laguna Palacios Formation (San Jorge Basin, Argentina): an Upper Cretaceous loess-paleosol sequence from Central Patagonia |url=https://www.researchgate.net/publication/363475405_Laguna_Palacios_Formation_San_Jorge_Basin_Argentina_an_Upper_Cretaceous_loess-paleosol_sequence_from_Central_Patagonia |journal=Argentine Meeting on Sedimentology |via=ResearchGate}}</ref> Their development is very closely associated with cooling and drying of the global climate that occurred during the [[Oligocene]], [[Miocene]] and [[Pliocene]].

== Suborders ==
:Albolls—wet soils; aquic soil moisture regime with an [[eluvial horizon]]
:Aquolls—wet soils; aquic soil moisture regime
:Cryolls—cold climate; frigid or cryic soil temperature regime
:Gelolls—very cold climate; mean annual soil temperature < 0 °C
:Rendolls—lime parent material
:Udolls—humid climate; [[udic moisture regime]]
:Ustolls—subhumid climate; [[ustic]] moisture regime
:Xerolls—Mediterranean climate; xeric moisture regime

Soils which are mostly similar to Mollisols but contain either continuous or discontinuous [[permafrost]], consequently affected by [[cryoturbation]] are common in high mountain plateaus of [[Tibet]] and the Andean [[altiplano]]. Such soils are called '''[[Gelisols|Molliturbels]]''' or '''[[Gelisols|Mollorthels]]''' and provide the best grazing land in such cold climates because they are not acidic like many other soils of very cold climates.

Other soils which have a mollic epipedon are classified as [[Vertisols]] because high shrink swell characteristics and relatively high clay contents dominate over the mollic epipedon. These soils are especially common in parts of South America in the [[Paraná River]] basin receiving abundant but erratic rainfall and extensive deposition of [[clay]]-rich minerals from the [[Andes]]. Mollic epipedons also occur in some [[Andisols]] but the andic properties take precedence.

In the [[World Reference Base for Soil Resources]] (WRB), Mollisols are split up into [[Chernozem]]s, [[Kastanozem]]s and [[Phaeozem]]s. Shallow or gravelly Mollisols may belong to the [[Leptosol]]s. Many Aquolls are [[Gleysol]]s, [[Stagnosol]]s or [[Planosol]]s. Mollisols with a natric horizon belong to the [[Solonetz]].<ref>{{Cite web|url = http://www.fao.org/3/i3794en/I3794en.pdf|title = World Reference Base for Soil Resources 2014, Update 2015|author=IUSS Working Group WRB|year = 2015|publisher = World Soil Resources Reports 106, FAO, Rome}}</ref>

== See also ==
*[[Pedogenesis]]
*[[Pedology (soil study)]]
*[[Soil classification]]
*[[Soil science]]
*[[Soil type]]

== References ==
{{Reflist}}
* Brady, N.C. and Weil, R.R. (1996).  ‘The Nature and Properties of Soils.’  11th edition.  (Prentice Hall, New Jersey).
* Buol, S.W., Southard, R.J., Graham, R.C., and McDaniel, P.A. (2003).  ‘Soil Genesis and Classification.’ 5th edition.  (Iowa State University Press - Blackwell, Ames.)

== External links ==
* {{cite web| url =https://www.nrcs.usda.gov/conservation-basics/natural-resource-concerns/soil/soil-science| title =Mollisols| publisher =USDA-NRCS| access-date =2006-05-14| url-status =live| archive-url =https://web.archive.org/web/20060509223503/http://soils.usda.gov/technical/classification/orders/mollisols.html| archive-date =2006-05-09}}
* {{cite web|url=http://grunwald.ifas.ufl.edu/Nat_resources/soil_orders/mollisols.htm |title=Mollisols |publisher=University of Florida |access-date=2006-05-14 |url-status=dead |archive-url=https://web.archive.org/web/20060404180459/http://grunwald.ifas.ufl.edu/Nat_resources/soil_orders/mollisols.htm |archive-date=April 4, 2006 }}
* {{cite web| url =http://soils.ag.uidaho.edu/soilorders/mollisols.htm| title =Mollisols| publisher =University of Idaho| access-date =2006-05-14| archive-url =https://web.archive.org/web/20060515133106/http://soils.ag.uidaho.edu/soilorders/mollisols.htm| archive-date =2006-05-15| url-status =dead}}

{{Soil type}}

[[Category:Pedology]]
[[Category:Types of soil]]