# Alfisol

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{{Short description|Clay soil rich in aluminium (Al) and iron (Fe)}}
{{Infobox soil
|name=Alfisol
|alternative_name=
|image=Alfisol profile.jpg
|image_size=250px
|image_caption=An Alfisol profile
|classification_system=[USDA soil taxonomy](/source/USDA_soil_taxonomy)
|profile=
|parent_material=
|code=
|process=
|climate=various 
}}

thumb|upright=1.6|Alfisols of the world
[[File:A_deciduous_beech_forest_in_Slovenia.jpg|thumb|upright=1.6|One of the environments in which Alfisols can develop is the [Temperate deciduous forest](/source/Temperate_deciduous_forest)]]

'''Alfisols''' are a soil order in [USDA soil taxonomy](/source/USDA_soil_taxonomy). Alfisols form in semi-arid to humid areas, typically under a [hardwood](/source/hardwood) forest cover. They have a clay-enriched [subsoil](/source/subsoil) and relatively high native fertility. "Alf" refers to aluminium (Al) and iron (Fe).  Because of their productivity and abundance, Alfisols represent one of the more important soil orders for food and fiber production. They are widely used both in agriculture and forestry, and are generally easier to keep fertile than other humid-climate soils, though those in [Australia](/source/Australia) and [Africa](/source/Africa) are still very deficient in [nitrogen](/source/nitrogen) and available [phosphorus](/source/phosphorus). Those in [monsoon](/source/monsoon)al tropical regions, however, have a tendency to acidify when heavily cultivated, especially when nitrogenous fertilizers are used.

In the [World Reference Base for Soil Resources](/source/World_Reference_Base_for_Soil_Resources) (WRB), most Alfisols are classified as [Luvisol](/source/Luvisol)s or [Lixisol](/source/Lixisol)s, but some are classed as [Retisol](/source/Retisol)s or [Nitisol](/source/Nitisol)s. Aqualfs are mainly [Stagnosol](/source/Stagnosol)s or [Planosol](/source/Planosol)s. Alfisols with a natric horizon are mainly [Solonetz](/source/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>

Alfisols occupy around one-tenth of the Earth's ice-free land surface. They are dominant in many areas, such as the [Ohio River](/source/Ohio_River) basin in the United States, [southern](/source/southern_Europe) and unglaciated [Western Europe](/source/Western_Europe), the Baltic region and central [European Russia](/source/European_Russia), the drier parts of [Peninsular India](/source/Peninsular_India), [Sudan](/source/Sudan) in Africa, and many parts of [South America](/source/South_America).

Alfisols have undergone only moderate leaching. By definition, they have at least 35% base saturation, meaning calcium, magnesium, and potassium are relatively abundant. This is in contrast to [Ultisols](/source/Ultisols), which are the more highly leached forest soils having less than 35% base saturation. In eastern [North America](/source/North_America), Alfisols are commonly found in glaciated areas while Ultisols are restricted to the areas south of the limit of maximum glaciation.

The [fossil record](/source/paleopedological_record) of Alfisols begins in the Late [Devonian](/source/Devonian). Probably owing to their fertility, they are the oldest forest soils; vegetation on weathered [Oxisol](/source/Oxisol)s, by contrast, is not known earlier than [Middle Permian](/source/Guadalupian). Fossil Alfisols remain common from the [Carboniferous](/source/Carboniferous) and all periods since the [Eocene](/source/Eocene).{{Citation needed|date=December 2007}}

==Suborders==
* [Aqualfs](/source/Aqualfs) – This suborder is saturated with water long enough to cause oxygen depletion.  Almost all of this suborder is thought to have been forested at some point. [Redoximorphic features](/source/Redoximorphic_features) are present.  
* [Cryalfs](/source/Cryalfs) – This suborder occurs mainly in high elevations which tend to be cold with temperatures ranging from greater than 0 C to less than 8 C.
* [Udalfs](/source/Udalfs) – This suborder is located in humid or subhumid climates. All of this word is thought to have been forested at some point. 
* Ustalfs – This suborder is located in semiarid climates with wet summers and dry winters. 
* [Xeralfs](/source/Xeralfs) – This suborder is located in mediterranean climates with very dry summers and wet winters.

==Fossil record of Alfisols==
thumb|upright=1.2|Alfisol between flows of middle Miocene Picture Gorge Basalt in Picture Gorge, Oregon
The fossil record of Alfisols extends back to the Late Devonian. The Alfisol paleosols were woodland soils and early forest soils. The fertile Alfisols were most likely formed by Devonian forests. The oldest of the Alfisol paleosol forest soils are in the paleosols of the Aztec Siltstone in [Victoria Land](/source/Victoria_Land), Antarctica. In the paleosols of the Aztec Siltstone, the Rosemary paleosol, there is evidence for trees from surficial tree-throwing structures and large drab-haloed root tracers. From the fossil wood and spores found in the Aztec Siltstone, there is a strong indication that the trees were [Archaeopteris](/source/Archaeopteris)-[Callixylon](/source/Callixylon).<ref>{{Cite book|last=Retallack|first=Greg J. |title=Soils of the past : an introduction to paleopedology|date=2019|isbn=978-1-119-53045-9|edition=Third |location=Hoboken, NJ|pages=360–361|oclc=1090696789}}</ref>

In upper [New York](/source/New_York_(state)) State, there have been Devonian trees found in a large variety of paleosols. These Devonian trees help give clues as to what ecological tolerances for various early trees looked like. The paleosols associated with [progymnosperm](/source/progymnosperm) trunks are interpreted to not have grown in soils similar to the type of soils modern seed plants are grown in. The [taxa](/source/taxa) of progymnosperm trunk fossils reproduced by [spore](/source/spore)s. For reproduction, they were more dependent on moisture than modern seed plants. Comparing the ''[Wattieza](/source/Wattieza)'', from New York Devonian paleosols, and the ''Callixylon''{{'s}} [ecotone](/source/ecotone)s to show this dependency on moisture it shows that the Wattieza lived in an ecotone of 571 ± 72&nbsp;mm mean annual precipitation and the Callixylon lived in an ecotone of 611 ± 46 mean annual precipitation. Because the Callixylon grew taller than the ''Wattieza'' it is inferred it was because there was more mean annual moisture available to the ''Callixylon''.<ref name=":0">{{Cite book|last=Retallack|first=Greg J. |title=Soils of the past : an introduction to paleopedology|date=2019|isbn=978-1-119-53045-9|edition=Third |location=Hoboken, NJ|pages=363–364|oclc=1090696789}}</ref>

In the lower [Walton Formation](/source/Walton_Formation), near [Sidney, New York](/source/Sidney%2C_New_York) fossils of ''[Archaeopteris macilenta](/source/Archaeopteris_macilenta)'', ''Callixylon zalesskyi'', and ''[Geminospora](/source/Geminispora) lemurata'' have been found. The tapering geometry of large woody root traces is the most likely cause of the intimate relationship between [Argillic horizon](/source/Argillic_horizon)s, Alfisols, and forests. The large woody root traces can transport water and clay using their large pipes. They are efficient at moving soil into a subsurface horizon when the plant dies and the roots decay.<ref>{{Cite book|last=Retallack|first=Greg J. |title=Soils of the past : an introduction to paleopedology|date=2019|isbn=978-1-119-53045-9|edition=Third |location=Hoboken, NJ|pages=364–365|oclc=1090696789}}</ref> 
thumb|upright=1.15|Alfisol paleosol cut by stream channel sandstone in Middle Devonian Oneonta Formation near East Windham, New York
The [Mata Amarilla Formation](/source/Mata_Amarilla_Formation), a formation in the [Austral Basin](/source/Magallanes_Basin) in southern [Patagonia, Argentina](/source/Patagonia%2C_Argentina) is the location known for the preservation of [podocarp](/source/Podocarpus)-dominated [fossil forests](/source/fossil_forests). In the eastern area of the middle section of the Mata Amarilla Formation, there are vertic Alfisols. In these Alfisols, there is a preservation of fossil forests, whose minimum age is 337 years. The fossil forests in this section are made up of ''[in situ](/source/in_situ)'' trunks. These trunks, in life position, have shallow root systems with well-developed horizontal roots, and have minimal development of vertical roots. A log of ''Podocarpxylon gargiae'' roots was found in the formation as well. The total mean [diameter](/source/diameter) of these trees in the vertic Alfisol paleosol is greater than 60&nbsp;cm and the smallest tree diameter is 26&nbsp;cm.<ref>{{Cite journal|last1=Varela|first1=A. N.|last2=Iglesias|first2=A.|last3=Poiré|first3=D.|last4=Zamuner|first4=A.|last5=Richiano|first5=S.|last6=Brea|first6=M.|date=2016|title=Fossil forests in the Austral Basin (Argentina) marking a Cenomanian heterogeneous forced regressive surface |journal=Geobiology|language=en|volume=14|issue=3|pages=293–313|doi=10.1111/gbi.12169|pmid=26663258 |bibcode=2016Gbio...14..293V |s2cid=25976814 |issn=1472-4669|hdl=11336/11714|hdl-access=free}}</ref>

While Afisol paleosols are known for their woodland soils and fossils, other types of fossils have also been found. The [ichnofacies](/source/ichnofacies) of the ground-nesting bees, ''Celliforma'', was formed in well drained Alfisols as well as [Aridisol](/source/Aridisol)s and [Oxisol](/source/Oxisol)s. The ''Termitichnus'' ichnofacies, which included a large array of termite nests and pellets, is found in Oligocene Alfisols, Aridisols, and Oxisols. All the [tetrapod](/source/tetrapod) bones and tracks from the paleosol sequences of Late Devonian and [Mississippian](/source/Mississippian_(geology)) of New York and Pennsylvania, U.S.A. are found in Aridisols and Alfisols. The Alfisols in the Texas High Plains have evidence for fossilized pollen and beetles.<ref>{{Cite book|last=Retallack|first=Greg J. |title=Soils of the past : an introduction to paleopedology|date=2019|isbn=978-1-119-53045-9|edition=Third |location=Hoboken, NJ|pages=373–374|oclc=1090696789}}</ref>  
center|thumb|535x535px|Multicolored rock strata in shades of red and yellow comprise a set of low, bare, rounded hills

== See also ==
{{commons category}}
*[Paleosol](/source/Paleosol)
*[Paleopedology](/source/Paleopedology)
*[Pedogenesis](/source/Pedogenesis)
*[Pedology (soil study)](/source/Pedology_(soil_study))
*[Soil classification](/source/Soil_classification)
*[Soil science](/source/Soil_science)
*[Soil type](/source/Soil_type)

==References==
{{reflist}}

==External links==
*{{cite web|url=https://www.nrcs.usda.gov/conservation-basics/natural-resource-concerns/soil/soil-science|title=Alfisols|publisher=United States Department of Agriculture|access-date=2008-01-04|url-status=live|archive-url=https://web.archive.org/web/20071018091104/http://soils.usda.gov/technical/classification/orders/alfisols.html|archive-date=2007-10-18}}
*{{cite web| url =http://soils.ag.uidaho.edu/soilorders/alfisols.htm| title =Alfisols| publisher =University of Idaho| access-date =2006-05-14| archive-url =https://web.archive.org/web/20060901063801/http://soils.ag.uidaho.edu/soilorders/alfisols.htm| archive-date =2006-09-01| url-status =dead}}

{{Soil type}}

Category:Pedology
Category:Types of soil

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Adapted from the Wikipedia article [Alfisol](https://en.wikipedia.org/wiki/Alfisol) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Alfisol?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.