Chapter 4: Brunisolic Order

Great Group	Subgroup
Melanic Brunisol	Orthic Melanic Brunisol O.MB
	Eluviated Melanic Brunisol E.MB
	Gleyed Melanic Brunisol GL.MB
	Gleyed Eluviated Melanic Brunisol GLE.MB
Eutric Brunisol	Orthic Eutric Brunisol O.EB
	Eluviated Eutric Brunisol E.EB
	Gleyed Eutric Brunisol GL.EB
	Gleyed Eluviated Eutric Brunisol GLE.EB
Sombric Brunisol	Orthic Sombric Brunisol O.SB
	Eluviated Sombric Brunisol E.SB
	Duric Sombric Brunisol DU.SB
	Gleyed Sombric Brunisol GL.SB
Dystric Brunisol	Orthic Dystric Brunisol O.DYB
	Eluviated Dystric Brunisol E.DYB
	Duric Dystric Brunisol DU.DYB
	Gleyed Dystric Brunisol GL.DYB
	Gleyed Eluviated Dystric Brunisol GLE.DYB

A diagrammatic representation of profiles of some subgroups of the Brunisolic order is given in Figure 28. Individual subgroups may include soils that have horizon sequences different from those shown. In the description of each subgroup, presented later in this chapter, a common horizon sequence is given; diagnostic horizons are underlined and some other commonly occurring horizons are listed.

Soils of the Brunisolic order have sufficient development to exclude them from the Regosolic order, but they lack the degree or kind of horizon development specified for soils of other orders. The central concept of the order is that of soils formed under forest and having brownish-colored Bm horizons, but the order also includes soils of various colors with both Ae horizons and B horizons having slight accumulations of either clay (Btj), or amorphous Al and Fe compounds (Bfj), or both. Soils having a Bf horizon less than 10 cm thick are a part of this order.

A Bm horizon may have any or all of the following: stronger chroma and redder hue than the underlying material, partial or complete removal of carbonates, slight illuviation based mainly on the occurrence of an overlying Ae horizon, a change in structure from that of the original material.

A Bm horizon may develop in materials of any color, such as gray, brown, black or red, and which vary in texture from gravel to clay.

Brunisolic soils include some that are calcareous to the surface and very slightly weathered, and others that are strongly acid and apparently weathered to about the same extent as the associated Podzolic soils. Most Brunisolic soils are well to imperfectly drained, but some that have been affected by seepage water are poorly drained although not strongly gleyed. They occur in a wide range of climatic and vegetative environments including Boreal Forest; mixed forest, shrubs, and grass; and heath and tundra.

Brunisolic soils have a Bm, Bfj, thin Bf, or Btj horizon at least 5 cm thick. They lack the diagnostic properties specified for soils of other orders. Thus they do not have any of the following: a solonetzic or podzolic B horizon, a Bt horizon, evidence of gleying as specified for soils of the Gleysolic order, organic horizons thicker than 40 cm if mesic or humic or 60 cm if fibric, permafrost within 1 m of the surface or 2 m if cryoturbated. Some Brunisolic soils have an Ah horizon, but it does not meet the specifications for a chernozemic A either because of its inherent properties or the associated soil climate.

Distinguishing Brunisolic Soils from Soils of Other Orders

Guidelines for distinguishing Brunisolic soils from soils of other orders with which they might be confused follow. To a degree the Brunisolic order can be considered as an intergrade order between Regosolic soils and soils of several other orders. The distinctions are based more upon the degree than the kind of development.

Chernozemic Some Brunisolic soils and many Chernozemic soils have an Ah or dark- colored Ap horizon and either a Bm or a Btj horizon. These soils are classified as Chernozemic only if they have a chernozemic A horizon as defined in Chapter 2. For example, Melanic Brunisols of the St. Lawrence Lowlands have a chernozemic-like A horizon but are excluded from the Chernozemic order because their soil moisture regime is humid.

Soils of subalpine, alpine, northern boreal, and subarctic areas having Ah and Bm horizons are classified as Chernozemic if they have a chernozemic A horizon. Many similar soils in these areas do not have a chernozemic A either because of a soil moisture regime that is humid or wetter, a mean annual soil temperature that is colder than 0°C, or because of some inherent property of the Ah horizon such as low base saturation. These soils are classified as Brunisolic. Further studies of these soils may lead to improved criteria for differentiating Brunisolic and Chernozemic soils. Current information indicates that many Ah horizons of soils at high altitudes and latitudes have the following characteristics that differ from the Ah horizons of Chernozemic soils:

• Low degree of incorporation of organic matter with mineral material, moder. This includes the turfy A horizons of some alpine soils with bulk density less than 1.0 Mg m^-3.

In addition, some of these soils at high elevations have the following properties that differ from those of Chernozemic soils:

• Appreciable content of pyrophosphate-extractable Al and Fe in the Ah horizon, especially in soils containing volcanic ash.
• More than 1% organic C in the B horizon.

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.

Cryosolic Cryosolic soils have permafrost within 1 m of the mineral surface or 2 m if strongly cryoturbated, but Brunisolic soils do not.

Vertisolic Vertisolic soils have both a vertic horizon (v) and a slickenside horizon (ss), but Brunisolic soils do not.

The Brunisolic order is divided into four great groups: Melanic Brunisol, Eutric Brunisol, Sombric Brunisol, and Dystric Brunisol based on soil reaction and the presence or absence of an Ah horizon, as indicated in the Brunisolic order chart.

Subgroups are separated on the basis of the kind and sequence of the horizons. Some former subgroup features (lithic, andic, turbic, and cryic) are now recognized taxonomically at either the family or series level, but different names are used for some of them. Alternatively, these features may be indicated as phases of subgroups, great groups, or orders.

Brunisolic Order
	Melanic Brunisol	Eutric Brunisol	Sombric Brunisol	Dystric Brunisol
Horizon	thick Ah or Ap (≥10 cm)	no (or thin) Ah or Ap (<10 cm)	thick Ah or Ap (≥10 cm)	no (or thin) Ah or Ap (<10 cm)
pH	≥5.5	≥5.5	<5.5	<5.5
Ap colour value	moist <4	moist ≥4	moist <4	moist ≥4

Melanic Brunisol

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.

Melanic Brunisols have an Ah horizon at least 10 cm in thickness or an Ap horizon 10 cm or more in thickness with a moist color value of less than 4, and either a Bm, Bfj, or Btj horizon at least 5 cm thick. The pH (0.01 M CaCl₂) is 5.5 or more in some part or all of the uppermost 25 cm of the B horizon, or in 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. Melanic 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. The Ah horizons of some Melanic Brunisols have all of the properties diagnostic of a chernozemic A except the associated soil climate. If cultivated, these soils are classified as Melanic Brunisols if part of the Bm, Btj or Bfj horizon remains below the Ap and as Humic Regosols if the Ap includes all of the former B horizon.

Orthic Melanic Brunisol (O.MB)
Common horizon sequence: LF, Ah^[1], Bm, Ck or C

These soils have the general properties specified for the Brunisolic order and the Melanic Brunisol great group. Characteristically, they have a forest mull Ah horizon with fine to medium granular structure and a brownish-colored Bm horizon with a chroma of 3 or more. The color of the B horizon normally fades with depth. Commonly the C horizon is calcareous.

Orthic Melanic Brunisols are identified by the following properties:

1. They have either an Ah horizon 10 cm thick or more or an Ap horizon at least 10 cm thick with a moist color value less than 4. The A horizon does not meet the requirements of a chernozemic A.
2. They have a pH (0.01 M CaCl₂) of 5.5 or more as specified for the great group.
3. They have a Bm horizon at least 5 cm thick.
4. They lack an eluvial horizon, Ae or Aej, at least 2 cm thick.
5. They lack mottles that indicate gleying as specified for Gleyed Melanic Brunisols.

Orthic Melanic Brunisols and all other subgroups of Brunisolic soils may have a lithic contact within 50 cm of the surface or have turbic or andic features. These features are separated taxonomically at the family (lithic, some andic) or series (turbic) levels, or as phases of any taxonomic level above the family.

Eluviated Melanic Brunisol (E.MB)

Common horizon sequence: LF, Ah, Ae or Aej, Bm or Btj, Ck or C

These soils have the general properties specified for soils of the Brunisolic order and the Melanic Brunisol great group. They differ from Orthic Melanic Brunisols by having an eluvial horizon, Ae or Aej, at least 2 cm thick. The underlying horizon may be a Btj with thin clay skins on some surfaces or, less commonly, a Bfj. Otherwise, they have the diagnostic properties of Orthic Melanic Brunisols.

Gleyed Melanic Brunisol (GL.MB)

Common horizon sequence: LF, Ah, Bmgj, Cgj or Cg or Ckg

These soils have the general properties specified for soils of the Brunisolic order and the Melanic Brunisol great group. They differ from Orthic Melanic Brunisols by having faint to distinct mottles within 50 cm of the mineral surface, or distinct or prominent mottles at depths of 50-100 cm. Otherwise, they have the diagnostic properties of Orthic Melanic Brunisols.

Gleyed Eluviated Melanic Brunisol (GLE.MB)

Common horizon sequence: LF, Ah, Ae or Aej, Bmgj or Btgj, Cgj or Cg or Ckg

These soils have the general properties specified for soils of the Brunisolic order and the Melanic Brunisol great group. They differ from Eluviated Melanic Brunisols by having mottles that indicate gleying. Gleyed Eluviated Melanic Brunisols have either an Ae or an Aej horizon at least 2 cm thick, and mottles as specified for Gleyed Melanic Brunisols.

Eutric Brunisol

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. Eutric Brunisols may have L, F, and H horizons, Ae or Aej horizons, and an Ah horizon less than 10 cm thick, but they do not have either Bt or podzolic B horizons. If cultivated, these soils are classified as Melanic Brunisols if the Ap horizon is at least 10 cm thick and has a moist color value less than 4 and part of the Bm, Bfj, or Btj remains below the Ap. They are classed as Eutric Brunisols if the Ap horizon does not meet the above specifications and part of the Bm horizon remains below the Ap. If the Ap includes all of the former B horizon, they are classified as Humic Regosols or Regosols, depending on the Ap.

Orthic Eutric Brunisol (O.EB)

Common horizon sequence: LFH, Bm, Ck or C

These soils have the general properties specified for the Brunisolic order and the Eutric Brunisol great group. Usually they have one or more organic surface horizons overlying a brownish-colored, base-saturated B horizon. The C horizon is commonly calcareous.

Orthic Eutric Brunisols are identified by the following properties:

1. They have a pH (0.01 M CaCl₂) of 5.5 or more as specified for the great group.
2. They have a Bm horizon at least 5 cm thick.
3. They lack an eluvial horizon, Ae or Aej, at least 2 cm thick.
4. They lack mottles that indicate gleying as specified for Gleyed Melanic Brunisols.
5. They lack an Ah horizon at least 10 cm thick and an Ap horizon at least 10 cm thick with a moist color value of 4 or less.

Eluviated Eutric Brunisol (E.EB)

Common horizon sequence: LFH, Ae or Aej, Bm or Btj, Ck or C

These soils have the general properties specified for soils of the Brunisolic order and the Eutric Brunisol great group. They differ from Orthic Eutric Brunisols by having an eluvial horizon, Ae or Aej, at least 2 cm thick. The underlying horizon may be a Btj with thin clay skins on some surfaces or, less commonly, a Bfj. Otherwise, they have the diagnostic properties of Orthic Eutric Brunisols.

Gleyed Eutric Brunisol (GL.EB)

Common horizon sequence: LFH, Bmgj, Cgj or Cg or Ckg

These soils have the general properties specified for soils of the Brunisolic order and the Eutric Brunisol great group. They differ from Orthic Eutric Brunisols by having faint to distinct mottles within 50 cm of the mineral surface, or distinct or prominent mottles at depths of 50-100 cm. Otherwise, they have the diagnostic properties of Orthic Eutric Brunisols.

Gleyed Eluviated Eutric Brunisol (GLE.EB)

Common horizon sequence: LFH, Ae or Aegj, Bmgj or Btjgj, Cgj or Cg or Ckg

These soils have the general properties specified for soils of the Brunisolic order and the Eutric Brunisol great group. They differ from Eluviated Eutric Brunisols by having mottles that indicate gleying. Gleyed Eluviated Eutric Brunisols have either an Ae or an Aej horizon at least 2 cm thick and mottles as specified for Gleyed Eutric Brunisols.

Sombric Brunisol

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.

Orthic Sombric Brunisol (O.SB)

Common horizon sequence: LFH, Ah, Bm, C

These soils have the general properties specified for the Brunisolic order and the Sombric Brunisol great group. Usually they have an organic layer at the surface, a dark grayish brown to black Ah horizon, a brown acid B horizon, and an acid C horizon.

Orthic Sombric Brunisols are identified by the following properties:

1. They have an Ah horizon at least 10 cm thick or an Ap horizon at least 10 cm thick with a moist color value less than 4.
2. They have a pH (0.01 M CaCl₂) of less than 5.5 as specified for the great group.
3. They have a Bm horizon at least 5 cm thick.
4. They lack an eluvial horizon, Ae or Aej, at least 2 cm thick.
5. They lack mottles that indicate gleying as specified for Gleyed Sombric Brunisols.
6. They lack a duric horizon.

Eluviated Sombric Brunisol (E.SB)

Common horizon sequence: LFH, Ah, Ae or Aej, Bm or Bfj, C

These soils have the general properties specified for soils of the Brunisolic order and the Sombric Brunisol great group. They differ from Orthic Sombric Brunisols by having an eluvial horizon, Ae or Aej, at least 2 cm thick. The underlying horizon may be a Btj with thin clay skins on some surfaces or, more commonly, a Bfj. Otherwise, these soils have the diagnostic properties of Orthic Sombric Brunisols.

Duric Sombric Brunisol (DU.SB)

Common horizon sequence: LFH, Ah, Bm or Bfj, Bc or BCc, C

These soils have the general properties specified for the Brunisolic order and the Sombric Brunisol great group. They differ from Orthic Sombric Brunisols by having a duric horizon within the control section. They may also have Ae and Btj or Bfj horizons and mottles that indicate gleying. A duric horizon is a strongly cemented acidic horizon that does not meet the requirements of a podzolic B and usually has a color similar to that of the parent material. This horizon has either an abrupt or a clear upper boundary and a diffuse lower boundary usually at least 50 cm below. Air-dry clods do not slake when immersed in water.

Gleyed Sombric Brunisol (GL.SB)

Common horizon sequence: LFH, Ah, Bmgj or Bfjgj, Cgj or Cg

These soils have the general properties specified for soils of the Brunisolic order and the Sombric Brunisol great group. They differ from Orthic Sombric Brunisols by having faint to distinct mottles within 50 cm of the mineral surface or distinct or prominent mottles at depths of 50-100 cm. Otherwise, these soils have the diagnostic properties of Orthic Sombric Brunisols.

Gleyed Eluviated Sombric Brunisol (GLE.SB)

Common horizon sequence: LFH, Ah, Aej or Aegj, Bmgj or Bfjgj, Cgj or Cg

These soils have the general properties specified for soils of the Brunisolic order and the Sombric Brunisol great group. They differ from Eluviated Sombric Brunisols by having mottles that indicate gleying. Gleyed Eluviated Sombric Brunisols have either an Ae or an Aej horizon at least 2 cm thick and mottles as specified for Gleyed Sombric Brunisols.

Dystric Brunisol

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 10 cm thick, but they do not have either a Bt or a podzolic B horizon. If cultivated, these soils are classified as Sombric Brunisols when the Ap horizon is at least 10 cm thick and has a moist color value less than 4 and part of the B horizon remains below the Ap. If the Ap horizon does not meet the above specifications but part of the B horizon remains below the Ap, then the soils are Dystric Brunisols. If the Ap includes all of the former B horizon, the soils are classified as Humic Regosol or Regosol, depending on the Ap horizon.

Orthic Dystric Brunisol (O.DYB)

Common horizon sequence: LFH, Bm, C

These soils have the general properties specified for the Brunisolic order and the Dystric Brunisol great group. Usually they have organic surface horizons and brownish-colored, acid B horizons overlying acid C horizons.

Orthic Dystric Brunisols are identified by the following properties:

1. They have a pH (0.01 M CaCl₂) of less than 5.5 as specified for the great group.
2. They have a Bm horizon at least 5 cm thick.
3. They lack an eluvial horizon, Ae or Aej, at least 2 cm thick.
4. They lack mottles that indicate gleying as specified for Gleyed Dystric Brunisols.
5. They lack a duric horizon.
6. They lack an Ah horizon at least 10 cm thick and an Ap horizon at least 10 cm thick with a moist color value of 4 or less.

Eluviated Dystric Brunisol (E.DYB)

Common horizon sequence: LFH, Ae or Aej, Bm or Bfj, C

These soils have the general properties specified for soils of the Brunisolic order and the Dystric Brunisol great group. They differ from Orthic Dystric Brunisols by having an eluvial horizon, Ae or Aej, at least 2 cm thick. The underlying horizon is commonly a Bfj, but it may be a Btj or a Bm. Otherwise, they have the diagnostic properties of Orthic Dystric Brunisols.

Duric Dystric Brunisol (DU.DYB)

Common horizon sequence: LFH, Bm or Bfj, Bc or BCc, C

These soils have the general properties specified for soils of the Brunisolic order and the Dystric Brunisol great group. They differ from Orthic Dystric Brunisols by having a duric horizon within the control section. Also they may have Ae and Btj or Bfj horizons and mottles that indicate gleying.

Gleyed Dystric Brunisol (GL.DYB)

Common horizon sequence: LFH, Bmgj or Bfjgj, Cgj or Cg

These soils have the general properties specified for soils of the Brunisolic order and the Dystric Brunisol great group. They differ from Orthic Dystric Brunisols by having faint to distinct mottles within 50 cm of the mineral surface, or distinct or prominent mottles at depths of 50-100 cm. Otherwise, they have the diagnostic properties of Orthic Dystric Brunisols.

Gleyed Eluviated Dystric Brunisol (GLE.DYB)

Common horizon sequence: LFH, Ae or Aej, Bmgj or Bfjgj, Cgj or Cg

These soils have the general properties specified for soils of the Brunisolic order and the Dystric Brunisol great group. They differ from Eluviated Dystric Brunisols by having mottles that indicate gleying. Gleyed Eluviated Dystric Brunisols have either an Ae or an Aej horizon at least 2 cm thick and mottles as specified for Gleyed Dystric Brunisols.