DISTINGUISHING BRUNISOLIC ORDER

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 the 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 Ap horizon and either a Em 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 lack a chernozemic A and so are excluded from the Chernozemic order because their soil moisture subclass is humid.

Soils of subalpine, alpine, and very cold northern areas having Ah and Em 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 soil climate that is humid or colder than O°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 of differentiation of 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. Bulk density less than 1.0.

 

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 + Fe in the Ah horizon, especially in soils containing volcanic ash. More than 1% organic carbon 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 Em 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 3 m of the mineral surface or 2 m if strongly cryoturbated, 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 acidity and the presence or absence of an Ah horizon, as indicated below.

DISTINGUISHING CHERNOZEMIC ORDER

Throughout the major area of Chernozemic soils in Canada there is little difficulty in distinguishing them from soils of other orders. However, soils of several other orders may have dark-colored Ah horizons. The bases for distinguishing Chernozemic soils from such soils are outlined below.

Solonetzic. These soils have a solonetzic B horizon, but Chernozemic soils do not.

Luvisolic. Some Dark Gray Luvisols and some Chernozemic soils have all of the following : a chernozemic A horizon, an Ae horizon, a Bt horizon, and a subhumid soil moisture regime. The classification of these soils at the order level is done according to these guidelines:

  1. If the chernozemic A horizon is eluviated as evidenced by gray streaks and splotches when the soil is dry, and if the Ae extends to a depth of at least 5 cm below the overlying Ah, Ahe, or Ap, the soil is Luvisolic (Dark Gray Luvisol).
  2. If the chernozemic A is not eluviated as described above, the soil is classified as Chernozemic unless the Ae horizon has a dry color value higher than 5 and a thickness greater than that of the Ah. In the latter case, the soil is classified as Luvisolic (Dark gray Luvisol).

Podzolic. These soils have a podzolic B horizon, but Chernozemic soils do not.

Brunisolic. Brunisolic soils having dark-colored, mineral-organic surface horizons are distinguished from Chernozemic soils. They do not have a chernozemic A horizon because their mean annual temperature is below O°C, or because their moisture subclass is humid or wetter, or the A horizon is acid or has a high C:N ratio. A degree of ambiguity remains on the basis of separation of some Melanic Brunisols from Chernozemic soils, especially in subalpine and alpine areas. Further work on these soils may disclose definitive differences between their A horizons and those of Chernozemic soils (see Chapter 4, Brunisolic order).

Regosolic. These soils do not have a chernozemic A horizon.

Gleysolic. Some of these soils have a chernozemic A horizon. They are excluded from the Chernozemic order because of evidence of reduction and poor drainage as specified in the Gleysolic order definition.

Chernozemic soils are divided into four great groups: Brown, Dark Brown, Black, and Dark Gray mainly on the basis of the color of the chernozemic A horizon, which reflects differences in the nature and amount of organic matter incorporated with the mineral material because of differences in climate and vegetation. The bases of the great group separations are tabulated below.

DISTINGUISHING CRYOSOLIC ORDER

Permafrost within 1 m or 2 m with cryoturbation.

DISTINGUISHING GLEYSOLIC ORDER

Listed below are guidelines for distinguishing Gleysolic soils from soils of other orders with which they might be confused.

Brunisolic. Gleyed subgroups of Brunisolic soils are differentiated from Gleysolic soils on the evidence that gleying is too weakly expressed to meet the specifications of Gleysolic soils.

Chernozemic. Some soils have a chernozemic A horizon and dull colors or mottling, indicating gleying within the control section. Those meeting the requirements specified for Gleysolic soils are classified in the Gleysolic order. Gleyed subgroups of the appropriate great group of Chernozemic soils have one or more of the following characteristics: gley features within 50 cm, although the soils fail to meet criteria of the Gleysolic order; and low chromas or mottles (or both) below a depth of 50 cm.

Cryosolic. Some Cryosolic soils have matrix colors of low chroma and prominent mottling within 50 cm of the surface similar to Gleysolic soils. Gleysolic soils, however, do not have permafrost within 1 m of the surface or 2 m if the soil is strongly cryoturbated.

Luvisolic. Some soils have eluvial horizons, Bt horizons, and colors that indicate gleying within 50 cm of the mineral surface. Such soils are classified as Luvic Gleysols if gley colors as specified for the Gleysolic order occur in the Btg horizon within 50 cm of the mineral soil surface.

If such gley colors occur only in the Aeg horizon (with the exception of thick Ae horizons as specified) or only below a depth of 50 cm, the soil is classified as a Gleyed subgroup of the appropriate great group in the Luvisolic order.

Organic. Gleysolic soils may have organic surface layers, but they are too thin to meet the minimum limits specified for soils of the Organic order.

Podzolic. Soils having both a podzolic B horizon and evidence of gleying that satisfies the specifications of Gleysolic soils are classified as Podzolic.

Regosolic. Soils with no horizon differentiation apart from evidence of gleying as specified for Gleysolic soils are classified as Gleysolic.

Solonetzic. Soils with both a En or Bnt horizon and evidence of gleying as specified for Gleysolic soils are classified as Solonetzic subgroups of the appropriate great groups of the Gleysolic order.

Gleysolic soils are divided into three great groups: Luvic Gleysol, Humic Gleysol, and Gleysol, which are separated on the basis of the development of the Ah horizon and the presence or absence of a Ht horizon as shown.

 

 

 

DISTINGUISHING LUVISOLIC ORDER

Guidelines for the distinction of Luvisolic from soils of other orders with which they might be confused follow.

Chernozemic. Some Chernozemic soils have Ah, Ae, and Bt horizons as do some Luvisolic soils. A basis of differentiation of these soils is the nature of the Ah and Ae horizons as follows :

  1. If the Ah is not a chernozemic A, the soil is Luvisolic.
  2. If the soil has a chernozemic A and a light-colored Ae that is thicker than the Ah or Ap and extends to a depth below 15 cm, the soil is Luvisolic.
  3. If the soil has an eluviated, dark-colored A horizon (Ahe or Ap· and a distinct Ae horizon thicker than 5 cm or that extends below the Ap, it is Luvisolic.

Solonetzic. Solonetzic soils have a solonetzic B horizon, but Luvisolic soils do not.

Podzolic. Some soils have both a podzolic B and a Bt horizon. The soil is classified as Luvisolic if the upper boundary of the Bt horizon is within 50 cm of the mineral surface and as Podzolic if the boundary is more than 50 cm below the surface.

Brunisolic. Luvisolic soils have a Bt horizon, but Brunisolic soils do not.

Gleysolic. Some Gleysolic soils have Ae and Bt horizons, but unlike Luvisolic soils they also have colors of low chroma or prominent mottling indicative of strong gleying.

Luvisolic soils are divided into two great groups, Gray Brown Luvisol and Gray Luvisol as shown below. The latter accounts for most of the area of Luvisolic soils.

 

 

DISTINGUISHING ORGANIC ORDER

Many soils of other orders may have organic horizons at the surface. The distinction between Organic soils and soils of other orders is based on:

  1. The thickness and the organic C content of organic-rich surface horizons in the case of soils with O horizons.
  2. The thickness of the folic material for soils with L, F, and H horizons.
  3. The depth to permafrost; organic materials having permafrost at depths of 1 m or less are classified as Cryosolic soils.

Organic soils are divided into four great groups based on the degree of decomposition of organic matter. Three of these great groups are commonly saturated with water, and the fourth is only briefly saturated.

 

 

 

 

DISTINGUISHING PODZOLIC ORDER

Guidelines for distinguishing Podzolic soils from soils of other orders with which they might be confused are as follows:

Luvisolic. Some Podzolic and some Luvisolic soils have Ae, Bf, and Bt horizons. These soils are classified as Podzolic if the upper boundary of the Bt horizon is at a depth below 50 cm and as Luvisolic if it is at a depth less than 50 cm.

Brunisolic. In the continuum of soils in nature many pedons have properties close to the arbitrary boundary line between Podzolic soils and acid Brunisolic soils. If the B horizon meets the requirements of a podzolic B, the soils are classified Podzolic.

Gleysolic. A podzolic B horizon takes precedence over gley features. Thus a soil having both a podzolic B horizon and gley colors as specified for soils of the Gleysol order is classified as Podzolic.

 

Organic. Some soils have podzolic soil B horizons underlying a thick layer of peat or folic materials. The soil is classified as Organic if the peat layer is greater than 60 cm or if the folic layer is greater than 40 cm.

The Podzolic order is divided into three great groups: Humic Podzol, Fero-Humic Podzol, and Humo-Ferric Podzol on the basis of organic C content and the organic C to pyrophosphate-extractable Fe ratio of the podzolic B horizon as shown below.

Subgroups are separated on the basis of the kind and sequence of the horizons indicating conformity with the central concept of the great group, the presence of additional horizons, or intergrading to soils of other orders. Some former subgroup features are now recognized taxonomically at either the family (lithic, some cryic) or series (turbic) level. They may be indicated also as phases of subgroups, great groups, or orders.

DISTINGUISHING REGOSOLIC ORDER

 

Guidelines for distinguishing Regosolic soils from soils of other orders with which they might be confused follow:

Chernozemic. Some Humic Regosols might be confused with Rego subgroups of Chernozemic soils. Such soils (usually Ah, C profiles) are classified as Humic Regosols if the Ah horizon fails to satisfy the requirements of a chernozemic A because of any of the following:

  1. It is a moder rather than a mull Ah.
  2. It lacks structure
  3. The soil climate is outside the range specified for a chernozemic A.
  4. Low base saturation or any other reason.

Brunisolic. Brunisolic soils must have a B horizon (Bm, Btj, Bfj) at least 5 cm thick. Regosolic soils usually do not have a B horizon and in those that do it is less than 5 cm thick.

 

Gleysolic. Some Gleysolic soils resemble Regosolic soils by having very weakly developed horizons. However, Gleysolic soils must have dull colors or mottles indicative of strong gleying; Regosolic soils do not.

Cryosolic. Cryosolic soils have permafrost within 1 m of the surface or 2 m if strongly cryoturbated; Regosolic soils do not.

The Regosolic order is divided into two great groups based on the presence or absence of a significant development of an Ah horizon as shown below.

Subgroups are based upon evidence of either relative stability of the material or periodic deposition of material and of gleying. Regosols with saline, cryic, turbic, and lithic features are differentiated taxonomically either at the family (lithic, some cryic) or the series (saline, turbic) levels. These features may also be indicated as phases of a subgroup, great group, or order.

DISTINGUISHING SOLONETZIC ORDER

Chernozemic. Soils having a chernozemic A horizon and a solonetzic B horizon are classified as Solonetzic. However, some Bnt horizons of Solonetzic soils are similar to the Btnj horizons of some Solonetzic subgroups of Chernozemic soils. In borderline cases the ratio of exchangeable Ca to Na determines the classification.

Luvisolic. Some Luvisolic soils are similar to Gray and Dark Gray Solods. The soils having a Bnt horizon rather than a Btnj are classified as Solonetzic.

Gleysolic. Some soils have solonetzic B horizons, dull colors, and mottling indicative of strong gleying. These soils are classified as Gleysolic.

The Solonetzic order includes three great groups: Solonetz, Solodized Solonetz, and Solod. They are separated on the basis of the degree of expression of the Ae horizon and the breakdown of the upper part of the B horizon.

Subgroups are separated on the basis of features indicating different climatic zones as reflected in the color of the A horizon and on the presence or absence of gleying. Lithic features are now recognized taxonomically at the family level or as a phase of subgroups, great groups, or orders.

 

 

 

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