Semi-terrestrial / Aquatic Humus forms

References:

Criteria:
Substrate / Site poorly or very poorly drained, moisture regime > 5.

See Field Guide to the Substrates of Ontario page 43 for estimating drainage classes. A class > 5 would require organic substrates dominated by peat or >2% mottle coverage in the mottle zone with  gray gley colors.

For a detailed description see the source Field Guide to the Substrates of Ontario

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Mull L, Ah

References:

Criteria:

Diagnostic organic horizons (F and H) lacking intimate association of colloidal organic matter with mineral substrate (well developed Ah).

The mixing of organic material with mineral soil is carried out by soil fauna followed by rapid bacterial decomposition, results in the formation of a mull. The mull is characterized with more complete decomposition and higher nutrient availability than the other two orders Moder and Mor. Generally, mulls are associated with more fertile soil and greater species richness. Macro-fauna create casts and burrows, distributing and providing access to food for smaller organisms. Mulls have Ah horizons where soil organic matter is intermixed with mineral soil in crumbly organo-mineral aggregates resulting from the activities of roots, fauna and microbes. These organo-mineral aggregates are generally associated with earthworm activity but can also result from the actions of other agents such as other animals, roots, white-rot fungi, termites, ants or mechanical disturbances. Soil fauna can increase decomposition by fragmenting or comminuting litter and altering the microbial community.

Summary:

For a detailed description see the source Forest Floor

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Moder L, F, Hi, (Ah)

References:

Criteria:

Hi horizon present, organic horizons not clearly delineated from mineral substrate.

Moders tend to have upper organic horizons with fungal mycelia and faunal castes, overlying Ah horizons of mixed organic faunal castes and mineral soil.


Like mors, the moder order tends to accumulate organic matter above the mineral horizons. However, moders have more faunal activity, similar to the mull order. These characteristics place the moder order as intermediary on a continuum between mor and mull, but also make them distinct from the other orders. Fungal decomposition is important in moders, but bacteria, actinomycetes, protozoa and fauna play a more important role than in mors. Compared with mors, moders have higher pH, lower C:N ratios and greater nutrient availability. Usually, they occur below deciduous forest stands.

Summary:


Distinguish Moder from Mull and Mor:

Luvisolic
Luvisolic soils must have a Bt horizon, but Brunisolic soils do not. However, it is difficult to distinguish a Bt from a Btj horizon and micromorphological examination may be required.

Podzolic
Podzolic soils must have a Podzolic B horizon and Brunisolic soils do not. However, the colors of some Bm and Bfj horizons are within the range of that of Podzolic B horizons, and some of these horizons contain concentrations of amorphous complexes of Al and Fe with organic matter close to the minimum concentration diagnostic for Bf horizons. Therefore, chemical analysis is required to differentiate some Brunisolic soils from Podzolic soils. Soils having a Bf horizon thinner than 10 cm are classified as Brunisolic.

Regosolic
Brunisolic soils must have a Bm, Bfj, thin Bf, or a Btj horizon at least 5 cm thick; Regosolic soils do not.

For a detailed description see the source Forest Floor

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Mor L, F, H

References:

Criteria:

Hi horizon absent, organic horizons sharply delineated from mineral substrate.

In a mor, plant litter is decomposed more slowly and accumulates on top of mineral horizons with a sharp transition between organic and mineral horizons. Fauna are uncommon and undecomposed plant material accumulates over time to form a compact matted Fm horizon containing scarce or no faunal droppings. Without soil fauna, decomposition is often incomplete and accumulation of organic material occurs. A mor forms due to incomplete fungal decomposition, resulting in some immobilization of nutrients in the forest floor – removing them from cycling and accessibility to plants. Mors tend to occur under less optimal climatic conditions over nutrient poor parent material. In boreal and some coastal forests of British Columbia, humus accumulations can immobilize a large portion of the nutrient capital of a site.

For a detailed description see the source Forest Floor

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Peaty Mor(L), (F), O(f,m,h

References:

Criteria:

Soils with a Bt horizon and no Bg horizon or podzolic B horizon if the Bt is > 50cm below mineral surface.

Soils of the Luvisolic order generally have light-colored, eluvial horizons and have illuvial B horizons in which silicate clay has accumulated. These soils develop characteristically in well to imperfectly drained sites, in sandy loam to clay, base-saturated parent materials under forest vegetation.

The Bt horizon must have increase in clay over that in the eluvial horizon, clay skins indicative of translocated clay accounting for 1% or more of the area of a section through the horizon, and be at least 5 cm thick. Luvisolic soils may have Ah, Ahe, or dark-colored Ap horizons.

The genesis of Luvisolic soils is thought to involve the suspension of clay in the soil solution near the soil surface, downward movement of that clay with the soil solution, and the deposition of the translocated clay at a depth where downward movement of the soil solution ceases or becomes very slow.

The eluvial horizon (Ahe, Ae) commonly has platy structure due perhaps to the periodic formation of ice lenses.

For a detailed description see the source CSSC

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Fibric Peaty Mor

References:

Criteria:

Soils with a g horizon within 50cm of the mineral surface.

Gleysolic soils are defined on the basis of color and mottling, which are considered to indicate the influence of periodic or sustained reducing conditions during their genesis.

Gleysolic soils have a horizon or subhorizon, at least 10 cm thick (the upper boundary of which occurs within 50 cm of the mineral surface), with moist colors.

Soils of the Gleysolic order have properties that indicate prolonged periods of intermittent or continuous saturation with water and reducing conditions during their genesis. Saturation with water may result from either a high groundwater table or temporary accumulation of water above a relatively impermeable layer, or both.

In contrast, soils saturated periodically with aerated water or saturated for prolonged cold periods, which restricts biological activity without developing properties associated with reducing conditions, are not classified as Gleysols.

Those that are rarely saturated now presumably had aquic moisture regimes in the past and were once under reducing conditions. Drainage, isostatic uplift, or other factors have resulted in a changed moisture regime in these soils.

For a detailed description see the source CSSC

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Mesic Peaty Mor

References:

Criteria:

Soils composed mainly of undecomposed fibric materials.

Soils of this great group are composed largely of relatively undecomposed fibric organic material.
Fibric material is usually classified on the von Post scale of decomposition as classes 1-4.
Fibrisols occur extensively in Canada, particularly in peat deposits dominated by sphagnum mosses.
Fibrisols have a dominantly fibric middle tier, or middle and surface tiers if a terric, lithic, or hydric contact occurs in the middle tier (40cm - 120cm).
Fibric (f) material undecomposed to weakly decomposed, plant species identifiable, when squeezed no peat escapes through fingers. (vP1 to 4)

For a detailed description see the source CSSC

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Humic Peaty Mor

References:

Criteria:

Soils composed mainly of decomposed mesic materials.

Fibric material is usually classified on the von Post scale of decomposition as classes 1-4.


Fibrisols occur extensively in Canada, particularly in peat deposits dominated by sphagnum mosses.

Fibrisols have a dominantly fibric middle tier, or middle and surface tiers if a terric, lithic, or hydric contact occurs in the middle tier (40cm - 120cm).

Fibric (f) material undecomposed to weakly decomposed, plant species identifiable, when squeezed no peat escapes through fingers.  (vP1 to 4)

For a detailed description see the source CSSC

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Anmor

References:

Criteria:

Soils composed mainly of decomposed humic materials.

Soils of this great group are at the most advanced stage of decomposition of the great groups of Organic soils. Most of the material is humified with few recognizable fibers. Humisols have a dominantly humic middle tier or middle and surface tiers if a terric, lithic, or hydric contact occurs in the middle tier.


Humic (h) material, strongly to completely decomposed, plant structure indistinct to unrecognizable; when squeezed at least half of the peat escapes through fingers, water released is dark. (vP7 to vP10)

For a detailed description see the source CSSC

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Organic --> Folisol Great Group

References:

Criteria:

Soils composed of upland (folic) materials, generally of forest origin.

Soils of the Folisol great group are composed of upland organic (folic) materials, generally of forest origin, that are either 40 cm or more in thickness, or are at least 10 cm thick if overlying bedrock or fragmental material.

Deep Folisols (greater than 40 cm of folic material) occur frequently in cool, moist, and humid forest ecosystems, particularly on the West Coast of Canada.

They also develop in northern regions where soil temperatures are low, but the soil is without permafrost. Shallow Folisols are found throughout Canada and commonly occur on upper slope shedding positions over bedrock and on, or incorporated in, fragmental or skeletal material.


Folic materials: L, F, and H - These organic horizons developed primarily from the accumulation of leaves, twigs, and woody materials with or without a minor component of mosses. They are normally associated with upland forested soils with imperfect drainage or drier.

For a detailed description see the source CSSC

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Regosolic --> Humic Regosol Great Group

References:

Criteria:

Soils with an Ah horizon >10cm thick.

These Regosolic soils have an Ah or dark colored Ap horizon at least 10 cm thick at the mineral surface. They may have organic surface horizons and buried mineral-organic horizons. They do not have a B horizon at least 5 cm thick.

For a detailed description see the source CSSC

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Regosolic -->Regosol Great Group

References:

Criteria:

Other soils

These Regosolic soils do not have an Ah or dark-colored Ap horizon at least 10 cm thick at the mineral soil surface. They may have buried mineral-organic layers and organic surface horizons, but no B horizon at least 5 cm thick.

For a detailed description see the source CSSC

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Brunisolic --> Melanic Brunisol Great Group

References:

Criteria:

Soils with an Ah horizon >10cm thick and a pH >5.5 on the B horizon.
These soils generally contain carbonates within 1m of the soil surface.

These are Brunisolic soils having a dark-colored Ah horizon and a relatively high degree of base saturation as indicated by their pH. They occur typically under deciduous or mixed forest vegetation on materials of high base status in areas of boreal to mesic temperature class and humid moisture subclass, but they are not restricted to such environments.

Many uncultivated Melanic Brunisols have a forest mull Ah horizon associated with the activity of soil fauna, especially earthworms.

For a detailed description see the source CSSC

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Brunisolic --> Sombric Brunisol Great Group

References:

Criteria:

Other soils with an Ah >10cm thick.

These are acid Brunisolic soils having a dark-colored Ah horizon and a relatively low base saturation as indicated by their pH. Minor areas of soils of this great group occur in association with the more widely spread Podzolic soils.

Sombric Brunisols have an Ah 10 cm or more in thickness or an Ap horizon 10 cm or more in thickness with a moist color value of less than 4, and a Bm, Bfj, thin Bf, or Btj horizon at least 5 cm thick.

The pH (0.01 M CaCl2) is less than 5.5 throughout the uppermost 25 cm of the B horizon, or throughout the B horizon and the underlying material to a total depth of at least 25 cm or to a lithic contact above that depth.

Sombric Brunisols may have L, F, and H horizons and Ae or Aej horizons, but they do not have solonetzic or podzolic B horizons or Bt horizons.

For a detailed description see the source CSSC

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Brunisolic --> Eutric Brunisol Great Group

References:

Criteria:

Other soils with a pH >5.5 in the B horizon.
These soils generally contain carbonates within 1m of the soil surface.

These are Brunisolic soils that have a relatively high degree of base saturation as indicated by their pH and lack a well-developed mineral-organic surface horizon. They occur mainly on parent material of high base status under forest or shrub vegetation in a wide range of climates.

Eutric Brunisols have either a Bm, Bfj, or Btj horizon at least 5 cm thick, and a pH (0.01 M CaCl2) of 5.5 or more in some part or all of the uppermost 25 cm of the B horizon, or some part or all of the B horizon and the underlying material either to a total depth of 25 cm or to a lithic contact above that depth.

For a detailed description see the source CSSC

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Brunisolic --> Dystric Brunisol Great Group

References:

Criteria:

Other soils.

These are acid Brunisolic soils that lack a well-developed mineral-organic surface horizon. They occur widely, usually on parent materials of low base status and typically under forest vegetation.

Dystric Brunisols have a Bm,Bfj, thin Bf, or Btj horizon at least 5 cm thick, and a pH (0.01 M CaCl2) of less than 5.5 throughout the upper 25 cm of the B horizon, or throughout the B horizon and the underlying material to a total depth of at least 25 cm or to a lithic contact above this depth.

Dystric Brunisols may have L, F, and H horizons; an Ae or Aej horizon, and an Ah horizon less than 10cm thick, but they do not have either a Bt or a podzolic B horizon.

For a detailed description see the source CSSC

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Podzolic --> Humic Podzol Great Group

References:

Criteria:

Soils with an Bh horizon >10cm thick.

These soils have a dark-colored podzolic B horizon that contains very little extractable Fe.

They occur typically in wet sites so that they are saturated with water during some periods of the year.

Characteristically they occur under heath (shrubland habitat), forest and heath, sphagnum.

Under virgin conditions Humic Podzols usually have thick L, F, and H or O horizons underlain by a light-colored eluvial horizon (Ae), an eluvial horizon darkened by humic material, or by a podzolic B horizon, which is usually a Bh.

The B horizon may include several kinds of podzolic B subhorizons: Bh, Bhf, and Bf, which may be cemented (ortstein, placic) or friable. The material below the podzolic B horizon may be cemented (duric), compact and brittle (fragipan), or friable.

For a detailed description see the source CSSC

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Podzolic --> Ferro Humic Podsol Great Group

References:

Criteria:

Other soils with a Bhf horizon > 10cm thick.

These soils have a dark-colored podzolic B horizon with a high content of organic C and an appreciable amount of extractable Fe and Al. They occur typically in the more humid part of the region of Podzolic soils under forest vegetation, or forest with heath or moss undercover. Under virgin conditions these soils usually have thick L, F, and H or O horizons; they may have an Ah horizon and usually have a light-colored Ae horizon. The podzolic B horizon is usually thick and dark reddish brown in the upper part and grades to lighter colors of higher chroma with depth.

The material below the podzolic B horizon may be cemented (duric), compact and brittle (fragipan), or friable.

Ferro-Humic Podzols have a Bhf horizon at least 10 cm thick and lack a Bh horizon at least 10 cm thick. The Bhf horizon contains 5% or more organic C and 0.6% or more pyrophosphate-extractable Fe+Al (0.4% for sands). It has a ratio of organic C to pyrophosphate-extractable Fe of less than 20, or has 0.3% or more pyrophosphate-extractable Fe, or both.

Ferro-Humic Podzols are generally both strongly acid and less than 50% base saturated (neutral salt). The pH-dependent CEC of the Bhf horizon is usually well above 8 cmol kg-1 and is commonly 25 cmol kg-1 or more. The Bhf horizon of these soils usually has a markedly silty feel when rubbed moist, which is presumably because of its high content of amorphous material.

For a detailed description see the source CSSC

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Podzolic --> Humo Ferric Podsol Great Group

References:

Criteria:

Other podzolic soils.

These soils have a brownish-colored podzolic B horizon with less organic matter than the B horizon of Ferro-Humic Podzols. They occur widely both in less humid sites of the region of Podzolic soils and in humid sites.

Typically they occur under coniferous, mixed, and deciduous forest vegetation but may occur under shrub and grass vegetation. Under virgin conditions these soils usually have L, F, and H horizons and may have an Ah horizon.

Usually they have a light-colored Ae horizon with an abrupt lower boundary to a podzolic B horizon in which the reddest hues or highest chromas and lowest color values usually occur near the top of the horizon and fade with depth.

Humo-Ferric Podzols have a podzolic B horizon at least 10 cm thick but do not have Bh or Bhf horizons at least 10 cm thick. The podzolic B horizon of Humo-Ferric Podzols may include a thin Bhf subhorizon, but usually it is a Bf horizon only.

For a detailed description see the source CSSC

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Luvisolic --> Gray Brown Luvisol Great Group

References:

Criteria:

Soils with an Ah horizon and mean annual soil temperature >8° C.

Soils of this great group have a forest mull Ah horizon and eluvial and Bt horizons as indicated for the order. They occur typically under deciduous or mixed forest vegetation on calcareous materials in areas of mild, humid climate. They occur mainly in the St. Lawrence Lowland.

Under undisturbed conditions the soils may have thin L, F, and H horizons, but, because of high biological activity and the abundance of earthworms, the leaf litter is usually quickly incorporated into the soil and humified.

Gray Brown Luvisols have either a forest-mull Ah horizon more than 5 cm thick or a dark-colored Ap horizon, an eluvial horizon, and a Bt horizon. The mean annual soil temperature is 8°C or higher and the soil moisture regime is humid or wetter.

For a detailed description see the source CSSC

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Luvisolic --> Gray Luvisol Great Group

References:

Criteria:

Other soils.

Soils of this great group have eluvial and Bt horizons as specified for the Luvisolic order. They usually have L, F, and H horizons and may have a degraded Ah or Abe horizon that resembles the upper A horizon of Dark Gray Chernozemic soils.

Commonly below the Ae horizon they have an AB or BA horizon in which the ped surfaces are grayer than the interiors of peds.

The solum of Gray Luvisols is generally slightly to moderately acid but may be strongly acid. The degree of base saturation (neutral salt extraction) is generally high. The parent materials are usually base saturated and commonly calcareous, but some Gray Luvisols have developed in acid materials.

Gray Luvisols have eluvial and Bt horizons. Their mean annual soil temperature is usually less than 8°C.

The dark colored A horizon is underlain by a thicker Ae horizon that extends to a depth greater than 15 cm below the mineral surface. It shows evidence of degradation (Ahe) and is underlain by an Ae horizon at least 5 cm thick below the Ahe or Ap horizon.

For a detailed description see the source CSSC

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Gleysolic --> Luvic Gleysol Great Group

References:

Criteria:

Soils with a Btg horizon.

Soils of this great group have the general properties specified for the Gleysolic order and a horizon of clay accumulation (Btg).

They are similar to Luvisolic soils except that they have dull colors or prominent mottling, or both, which indicates strong gleying.

They may have organic surface horizons and an Ah horizon. Luvic Gleysols occur commonly on poorly drained sites in association with Luvisolic soils.

Luvic Gleysols usually have an eluvial horizon (Ah, Aeg) and a Btg horizon. A Btg horizon is defined based on an increase in silicate clay over that present in the A horizon.

For a detailed description see the source CSSC

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Gleysolic --> Humic Gleysol Great Group

References:

Criteria:

Soils with a Ah horizon > 10cm thick.

Soils of this great group have a dark-colored A horizon in addition to the general properties of soils of the Gleysolic order.

They occur commonly in poorly drained positions in association with some Chernozemic, Luvisolic, Podzolic, and Brunisolic soils.

These soils may have organic surface horizons derived from grass and sedge, moss, or forest vegetation.

Humic Gleysols have no Bt horizon. They have either an Ah horizon at least 10 cm thick or a mixed surface horizon (Ap) at least 15 cm thick

For a detailed description see the source CSSC

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Gleysolic --> Gleysol Great Group

References:

Criteria:

Other soils.

Soils of this great group have the general properties specified for soils of the Gleysolic order, but they lack a well-developed, mineral-organic surface horizon. They occur commonly in poorly drained positions in association with soils of several other orders.

Gleysols lack an Ah or Ap horizon as specified for Humic Gleysols. They also lack a Bt horizon. They may have either an Ah horizon thinner than 10 cm or an Ap horizon

These soils have a gleyed B or C horizon, and they may have an organic surface horizon.

For a detailed description see the source CSSC

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