A gleysol is a wetland soil (
hydric soil Hydric soil is soil which is permanently or seasonally saturated by water, resulting in anaerobic conditions, as found in wetlands.
Overview
Most soils are aerobic. This is important because plant roots respire (that is, they consume oxygen an ...
) that, unless drained, is saturated with
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...
for long enough to develop a characteristic colour pattern. The pattern is essentially made up of reddish, brownish, or yellowish colours at surfaces of
soil particles and/or in the upper
soil horizons mixed with greyish/blueish colours inside the peds and/or deeper in the soil. Gleysols are also known as ''Gleyzems'', ''meadow soils'', ''Aqu''-suborders of
Entisols
Entisols are soils defined in USDA soil taxonomy that do not show any profile development other than an A horizon. An entisol has no diagnostic horizons, and most are basically unaltered from their parent material, which can be unconsolidated sed ...
,
Inceptisols
Inceptisols are a soil order in USDA soil taxonomy. They form quickly through alteration of parent material. They are more developed than Entisols. They have no accumulation of clays, iron oxide, aluminium oxide or organic matter. They have an ...
and
Mollisols
Mollisol is a soil type which has deep, high organic matter, nutrient-enriched surface soil (a horizon), typically between 60 and 80 cm in depth. This fertile surface horizon, called a mollic epipedon, is the defining diagnostic feature of M ...
(
USDA soil taxonomy
USDA soil taxonomy (ST) developed by the United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters (most commonly their properties) and in ...
), or as ''groundwater soils'' and ''hydro-morphic soils''.
Gleysols occur within a wide range of
unconsolidated materials, mainly
fluvial,
marine and
lacustrine
A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...
sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...
s of
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...
or
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
age, having
basic to
acidic
mineralogy. They are found in
depression areas and low
landscape positions with shallow groundwater.
Wetness is the main limitation on agriculture of virgin gleysols; these are covered with natural
swamp vegetation
Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characte ...
and lie idle or are used for extensive
grazing
In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and other ...
. Farmers use artificially-drained gleysols for
arable cropping,
dairy farming
Dairy farming is a class of agriculture for long-term production of milk, which is processed (either on the farm or at a dairy plant, either of which may be called a dairy) for eventual sale of a dairy product. Dairy farming has a history th ...
and
horticulture
Horticulture is the branch of agriculture that deals with the art, science, technology, and business of plant cultivation. It includes the cultivation of fruits, vegetables, nuts, seeds, herbs, sprouts, mushrooms, algae, flowers, seaweeds and no ...
. Gleysols in the
tropics
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referr ...
and
subtropics are widely planted with
rice
Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
.
Gleysols occupy an estimated 720 million hectares worldwide. They are
azonal soils and occur in nearly all
climate
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...
s. The largest extent of Gleysols is in northern
Russia
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...
,
Siberia
Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive region, geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a ...
,
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
,
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S. ...
,
China and
Bangladesh
Bangladesh (}, ), officially the People's Republic of Bangladesh, is a country in South Asia. It is the eighth-most populous country in the world, with a population exceeding 165 million people in an area of . Bangladesh is among the mos ...
. An estimated 200 million hectares of gleysols are found in the tropics, mainly in the
Amazon
Amazon most often refers to:
* Amazons, a tribe of female warriors in Greek mythology
* Amazon rainforest, a rainforest covering most of the Amazon basin
* Amazon River, in South America
* Amazon (company), an American multinational technolog ...
region, equatorial
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
, and the coastal swamps of
Southeast Asia
Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...
.
They exhibit a greenish-blue-grey
soil color Soil color does not affect the behavior and use of soil; however, it can indicate the composition of the soil and give clues to the conditions that the soil is subjected to.Brady, Nyle C. & Ray R. Weil ''Elements of the Nature and Properties of ...
due to
anoxic
The term anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts:
* Anoxic waters, sea water, fresh water or groundwater that are depleted of diss ...
wetland
A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The p ...
conditions. On exposure, as the iron in the soil
oxidizes colors are transformed to a mottled pattern of reddish, yellow or orange patches. During soil formation (''gleying''), the oxygen supply in the soil profile is restricted due to soil moisture at saturation. Anaerobic micro-organisms support cellular respiration by using alternatives to free oxygen as
electron acceptors to support
cellular respiration
Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive the bulk production of ATP. Cellular respiration may be des ...
. Where
anaerobic organisms reduce
Reduction, reduced, or reduce may refer to:
Science and technology Chemistry
* Reduction (chemistry), part of a reduction-oxidation (redox) reaction in which atoms have their oxidation state changed.
** Organic redox reaction, a redox react ...
ferric oxide
Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturall ...
to
ferrous oxide
Iron(II) oxide or ferrous oxide is the inorganic compound with the formula FeO. Its mineral form is known as wüstite. One of several iron oxides, it is a black-colored powder that is sometimes confused with rust, the latter of which consists of ...
, the reduced mineral compounds produce the typical gleysoil color.
Green rust
Green rust is a generic name for various green crystalline chemical compounds containing iron(II) and iron(III) cations, the hydroxide () anion, and another anion such as carbonate (), chloride (), or sulfate (), in a layered double hydroxide str ...
, a
layered double hydroxide
Layered double hydroxides (LDH) are a class of ionic solids characterized by a layered structure with the generic layer sequence cB Z AcBsub>''n'', where c represents layers of metal cations, A and B are layers of hydroxide () anions, and Z are ...
(LDH) of Fe(II) and Fe(III) can be found as the mineral
fougerite in gleysoils.
Gleysoils may be sticky and hard to work, especially where the gleying is caused by surface water held up on a slowly permeable layer. However, some
ground-water gley soils have
permeable
Permeability, permeable, and semipermeable may refer to:
Chemistry
*Semipermeable membrane, a membrane which will allow certain molecules or ions to pass through it by diffusion
*Vascular permeability, the movement of fluids and molecules betwe ...
lower
horizons, including, for example, some sands in hollows within sand dune systems (known as slacks), and in some
alluvial
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. All ...
situations.
Groundwater gleysoils develop where
drainage
Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging (anaerobic condition ...
is poor because the
water table
The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated.
T ...
(
phreatic
''Phreatic'' is a term used in hydrology to refer to aquifers, in speleology to refer to cave passages, and in volcanology to refer to a type of volcanic eruption.
Hydrology
The term phreatic (the word originates from the Greek , meaning "well" ...
surface) is high, whilst surface-water gleying occurs when
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
input at the surface does not drain freely through the ground. A reducing environment exists in the saturated layers, which become mottled greyish-blue or greyish-brown due to its
ferrous iron
In chemistry, iron(II) refers to the element iron in its +2 oxidation state. In ionic compounds (salts), such an atom may occur as a separate cation (positive ion) denoted by Fe2+.
The adjective ferrous or the prefix ferro- is often used to ...
and organic matter content. The presence of reddish or orange mottles indicates localised re-oxidation of ferrous salts in the soil matrix, and is often associated with root channels, animal burrows, or cracking of the soil material during dry spells.
In the
World Reference Base for Soil Resources The World Reference Base for Soil Resources (WRB) is an international soil classification system for naming soils and creating legends for soil maps. The currently valid version is the fourth edition 2022. It is edited by a working group of the In ...
(WRB),
soils with
redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...
processes due to ascending
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...
belong to the Reference Soil Group Gleysols. Soils with redox processes due to
stagnant water are
Stagnosol
A Stagnosol in the World Reference Base for Soil Resources (WRB) is soil with strong mottling of the soil profile due to redox processes caused by stagnating surface water. Stagnosols are periodically wet and mottled in the topsoil and subsoil, ...
s and
Planosol
A Planosol in the World Reference Base for Soil Resources is a soil with a light-coloured, coarse-textured, surface horizon that shows signs of periodic water stagnation and abruptly overlies a dense, slowly permeable subsoil with significantly ...
s.
See also
*
Pedogenesis
Soil formation, also known as pedogenesis, is the process of soil genesis as regulated by the effects of place, environment, and history. Biogeochemical processes act to both create and destroy order ( anisotropy) within soils. These alterations ...
*
Pedology (soil study)
Pedology (from Greek: πέδον, ''pedon'', "soil"; and λόγος, ''logos'', "study") is a discipline within soil science which focuses on understanding and characterizing soil formation, evolution, and the theoretical frameworks for modeling ...
*
Soil classification
Soil classification deals with the systematic categorization of soils based on distinguishing characteristics as well as criteria that dictate choices in use.
Overview
Soil classification is a dynamic subject, from the structure of the system, ...
*
Anaerobic respiration
Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain.
In aerobic organisms undergoing r ...
*
Fougerite, the natural form of
green rust
Green rust is a generic name for various green crystalline chemical compounds containing iron(II) and iron(III) cations, the hydroxide () anion, and another anion such as carbonate (), chloride (), or sulfate (), in a layered double hydroxide str ...
*
Blue goo
Blue goo is a sticky, plasticky, blueish-grey, clay-textured soil derived from a highly weathered serpentinite mélange. The name derives from the soil's color; a result of undergoing anaerobic conditions and becoming gleyed. A greyer variation i ...
*
Redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...
*
Redox gradient
A redox gradient is a series of reduction-oxidation (redox) reactions sorted according to redox potential. The redox ladder displays the order in which redox reactions occur based on the free energy gained from redox pairs. These redox gradients ...
External links
profile photos (with classification)WRB homepage
profile photos (with classification)IUSS World of Soils
References
# Trolard F., Bourrié G., Abdelmoula M., Refait P. and Feder F. 2007: Fougerite, a new mineral of the pyroaurite-iowaite group: description and crystal structure. Clays and Clay Minerals, vol. 55, no. 3, p. 323-334; .
# Génin J.-M. R., Aïssa R., Géhin A., Abdelmoula M., Benali O., Ernstsen V., Ona-Nguema G., Upadhyay Ch. and Ruby Ch. 2005: Fougerite and Fe
II-III hydroxycarbonate green rust; ordering, deprotonation and/or cation substitution; structure of hydrotalcite-like compounds and mythic ferrosic hydroxide Fe(OH)
2+x. Solid State Sciences, vol. 7., no. 5, p. 545-572. .
Further reading
* W. Zech, P. Schad, G. Hintermaier-Erhard: Soils of the World. Springer, Berlin 2022, Chapter 3.3.2.
{{DEFAULTSORT:Gley Soil
Pedology
Types of soil