Gray Luvisol (GL)
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 occur typically under boreal or mixed forest vegetation and in forest-grassland transition zones in a wide range of climatic areas. Their main area of occurrence is in the subhumid central to northern part of the Interior Plains, but they occur also in humid and perhumid areas of eastern Canada. In the latter climatic area, they occur mainly on medium- to fine-textured parent materials.
Gray Luvisols have eluvial and Bt horizons. Their mean annual soil temperature is usually less than 8°C. If the soil moisture regime is subhumid, any dark-colored A horizon must satisfy one or more of the following conditions:
- It is not a chernozemic A.
- It 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.
The great group is divided into 14 subgroups based on the kind and sequence of horizons and evidence of gleying.
Orthic Gray Luvisol (O.GL)
Common horizon sequence: LFH, Ae, AB, Bt, C or Ck
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They have well-developed Ae and Bt horizons and usually have organic surface horizons. Faint mottling may occur immediately above or within the Bt horizon.
Orthic Gray Luvisols are identified by the following properties:
- They have an Ae horizon with a chroma of less than 3 unless the chroma of the parent material is 4 or more.
- They have a Bt horizon.
- They lack a Bf horizon.
- They lack a fragipan.
- They may have a dark-colored, mineral-organic surface horizon (Ah or Ahe) less than 5 cm thick.
- They may have an Ap horizon, but its dry color value must be 5 or higher.
- Distinct mottling, that indicates gleying does not occur within 50 cm of the mineral surface. Prominent mottling does not occur at depths of 50-100 cm.
Dark Gray Luvisol (D.GL)
Common horizon sequence: LFH, Ah or Ahe, Ae, Bt, C or Ck
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Orthic Gray Luvisols by having an Ah or Ahe horizon 5 cm or more in thickness. These horizons generally have eluvial features, such as gray streaks or splotches when dry, or platy structure. In the case of disturbed soils, the dry color value of the Ap horizon is 3.5-5.0 and some of the Ae horizon remains below the Ap. The differentiation of Dark Gray Luvisols from Dark Gray Chernozemic soils was outlined previously in this chapter. Dark Gray Luvisols have a mean annual soil temperature less than 8°C. They may have a Btnj or a Bm horizon above the Bt horizon.
Brunisolic Gray Luvisol (BR.GL)
Common horizon sequence: LFH, Bm or Bf, Ae, Bt, BC, C or Ck
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Orthic Gray Luvisols by having in the upper solum, either a Bm horizon at least 5 cm thick with a chroma of 3 or more, or a Bf horizon less than 10 cm thick that does not extend below 15 cm. Such Bm or Bf horizons are thought to have developed in a former Ae horizon. These soils do not have a dark-colored Ah or Ahe horizon 5 cm or more in thickness.
Podzolic Gray Luvisol (PZ.GL)
Common horizon sequence: LFH, Ae, Bf, Ae, Bt, BC, C or Ck
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Orthic Gray Luvisols by having a Bf horizon at least 10 cm thick in the upper solum. They may also have a dark-colored Ah or Ahe horizon 5 cm or more in thickness. The upper boundary of the Bt horizon must be within 50 cm of the mineral surface or the soil is classified in the Podzolic order.
Solonetzic Gray Luvisol (SZ.GL)
Common horizon sequence: LFH, Ae, AB, Btnj, BC, C or Csk
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Orthic Gray Luvisols by having a Btnj horizon that indicates an intergrade to the Solonetzic order. The Btnj horizon usually has a harder consistence, more pronounced coatings on the prismatic or blocky peds, and a lower ratio of exchangeable Ca:Na than the Bt horizons of most Gray Luvisols. This subgroup is associated with saline parent materials. Solonetzic Gray Luvisols do not have an Ah or Ahe horizon 5 cm or more in thickness, and so the surface horizons do not meet the criteria for Dark Gray Luvisols.
Fragic Gray Luvisol (FR.GL)
Common horizon sequence: LFH, Ahe, Ae, Bt, Btx or BCx, C
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Orthic Gray Luvisols by having a fragipan either within or below the Bt horizon.
Vertic Gray Luvisol (V.GL)
Common horizon sequence: LFH, Ah or Ahe, Ae, AB, Bt or Btnj, Btvj, Btss or Ckss, Ck
These soils have the general properties specified for the Luvisolic order and the Gray Luvisol great group. They may have any horizons in the upper solum common to other subgroups within the Gray Luvisol great group. However, they differ from other subgroups by having properties that indicate intergrading to the Vertisolic order. Specifically, they have a slickenside horizon (Btss or Ckss), the upper boundary of which occurs within 1 m of the mineral surface. They may have a weak vertic horizon (Btvj).
Gleyed Gray Luvisol (GL.GL)
Common horizon sequence: LFH, Ae, Btgj, Cg
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Orthic Gray Luvisols by having either distinct mottles that indicate gleying within 50 cm of the mineral surface, or prominent mottles at depths of 50-100 cm. Commonly the matrix colors are of lower chroma than those of associated, well-drained soils.
Gleyed Dark Gray Luvisol (GLD.GL)
Common horizon sequence: LFH, Ah or Ahe, Ae, Btgj, Cg or Ckg
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Dark Gray Luvisols by having either distinct mottles that indicate gleying within 50 cm of the mineral surface, or prominent mottles at depths of 50-100 cm.
Gleyed Brunisolic Gray Luvisol (GLBR.GL)
Common horizon sequence: LFH, Bm or Bf, Aegj, Btgj, BCgj, Cg
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Brunisolic Gray Luvisols by having either distinct mottles that indicate gleying within 50 cm of the mineral surface, or prominent mottles at depths of 50-100 cm. They do not have Ah or Ahe horizons 5 cm or more in thickness.
Gleyed Podzolic Gray Luvisol (GLPZ.GL)
Common horizon sequence: LFH, Ae, Bf, Aegj, Btgj, BCgj, Cg
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Podzolic Gray Luvisols by having either distinct mottles that indicate gleying within 50 cm of the mineral surface, or prominent mottles at depths of 50-100 cm. They may have a dark-colored A horizon 5 cm or more in thickness.
Gleyed Solonetzic Gray Luvisol (GLSZ.GL)
Common horizon sequence: LFH, Ae, ABgj, Btnjgj, Cgj or Csag
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Solonetzic Gray Luvisols by having either distinct mottles that indicate gleying within 50 cm of the mineral surface, or prominent mottles at depths of 50-100 cm. They do not have an Ah or Ahe horizon 5 cm or more in thickness.
Gleyed Fragic Gray Luvisol (GLFR.GL)
Common horizon sequence: LFH, Ahe, Aegj, Btgj, Btxgj, or BCxg, Cg
These soils have the properties specified for the Luvisolic order and the Gray Luvisol great group. They differ from Fragic Gray Luvisols by having either distinct mottles that indicate gleying within 50 cm of the mineral surface, or prominent mottles at depths of 50-100 cm. They may have a dark-colored A horizon 5 cm or more in thickness.
Gleyed Vertic Gray Luvisol (GLV.GL)
Common horizon sequence: LFH, Ah or Ahe, Ae, AB, Btgj, or Btnjgj, Btgjvj, Btgjss or Ckgjss, Ckgj or Ckg
These soils have the general properties specified for the Luvisolic order and the Gray Luvisol great group. They also have properties that indicate intergrading to the Vertisolic order. Specifically, they have a slickenside horizon (Btgjss or Ckgjss), the upper boundary of which occurs within 1 m of the mineral surface. These soils may have a weak Vertic horizon (Btgjvj). They differ from Vertic Gray Luvisols by having either distinct mottles that indicate gleying within 50 cm of the mineral surface, or prominent mottles at depths of 50-100 cm.
Note: Diagnostic horizons are underlined.