Gray Brown Luvisol (GBL)
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. A transitional AB or BA horizon having gray coatings on structural aggregates is generally present, particularly in medium and fine-textured soils. Although the Bt horizon is generally immediately underlain by calcareous materials, a transitional BC horizon may be present.
Under cultivated conditions the Ah and commonly part of the Ae horizon are mixed to form an Ap horizon. However the Bt and part of the Ae horizon usually remain intact under the Ap horizon unless either cultivation greatly exceeds 15 cm in depth or surface erosion has caused the Ap horizon to be developed in the Ae or Bt horizons or both.
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.
The great group is divided into eight subgroups based on the profile developed above the Bt horizon, the presence of Vertic features, and evidence of gleying.
Orthic Gray Brown Luvisol (O.GBL)
Common horizon sequence: Ah, Ae, Bt, Ck
These soils have the properties specified for the Luvisolic order and the Gray Brown Luvisol great group. They have well-developed Ah, eluvial, and Bt horizons, and usually calcareous C horizons. Faint mottling may occur immediately above or within the Bt horizon.
Orthic Gray Brown Luvisols are identified by the following properties:
- These soils have either a forest-mull Ah horizon more than 5 cm thick or a dark-colored (moist) Ap horizon.
- These soils have an Ae horizon of which the upper 5 cm is light colored with a chroma of 3 or less. The difference in chroma between the upper and lower part of the Ae is less than 1.
- These soils have a Bt horizon and lack a Bf horizon.
- Distinct mottling indicative of gleying does not occur within 50 cm of the mineral surface, and prominent mottling does not occur at depths of 50-100 cm.
Brunisolic Gray Brown Luvisol (BR.GBL)
Common horizon sequence: Ah, Ae, Bm or Bf, Ae, Bt, BC, Ck
These soils have the properties specified for the Luvisolic order and the Gray Brown Luvisol great group. They differ from Orthic Gray Brown 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. If disturbance results in the Bm or Bf horizon being incorporated into the Ap, the disturbed soil is classified as an Orthic Gray Brown Luvisol.
Podzolic Gray Brown Luvisol (PZ.GBL)
Common horizon sequence: LFH, Ah, Ae, Bf, Ae, Bt, BC, Ck
These soils have the properties specified for the Luvisolic order and the Gray Brown Luvisol great group. They differ from Orthic Gray Brown Luvisols by having a Bf horizon at least 10 cm thick in the upper solum. These soils may or may not have an Ae horizon. 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. If disturbance results in the Bf horizon being incorporated into the Ap, the disturbed soil is classified as an Orthic Gray Brown Luvisol.
Vertic Gray Brown Luvisol (V.GBL)
Ah, Ae, Bm or Bf, Bt, Bvj, Bss or Ckss, Ck
These soils have the general properties specified for the Luvisolic order and the Gray Brown Luvisol great group. They may have any horizons in the upper solum common to other subgroups within the Gray Brown Luvisol great group. However, they differ from other subgroups by having properties indicative of intergrading to the Vertisolic order. Specifically, they have a slickenside horizon (Bss, Bkss, or Ckss), the upper boundary of which occurs within 1 m of the mineral surface. They may have a weak vertic horizon (Bvj).
Gleyed Gray Brown Luvisol (GL.GBL)
Common horizon sequence: Ah, Aegj, Btgj, Ckg
These soils have the properties specified for the Luvisolic order and the Gray Brown Luvisol great group. They differ from Orthic Gray Brown 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 Gray Brown Luvisols generally have thicker and darker Ah horizons than well-drained subgroups on similar parent materials. The color and textural differences between the Ae and Bt horizons are generally less marked in the gleyed than in the orthic subgroup.
Gleyed Brunisolic Gray Brown Luvisol (GLBR.GBL)
Common horizon sequence: Ah, Bmgj, Aegj, Btgj, Ckg
These soils have the properties specified for the Luvisolic order and the Gray Brown Luvisol great group. They differ from Brunisolic Gray Brown 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 Podzolic Gray Brown Luvisol (GLPZ.GBL)
Common horizon sequence: Ah, Ae, Bfgj, Aegj, Btgj, Ckg
These soils have the properties specified for the Luvisolic order and the Gray Brown Luvisol great group. They differ from Podzolic Gray Brown 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. Besides a forest-mull Ah horizon, they have a Bf horizon at least 10 cm thick and a gleyed Bt horizon of which the upper boundary is within 50 cm of the mineral surface.
Gleyed Vertic Gray Brown Luvisol (GLV.GBL)
Common horizon sequence: Ah, Ae, Bmgj, or Bfgj, Btgj, Bgjvj, Bgjss or Ckgjss, Ckgj or Ckg
These soils have the general properties specified for the Luvisolic order and the Gray Brown Luvisol great group. Also, they have properties that indicate intergrading to the Vertisolic order. Specifically, they have a slickenside horizon (Bgjss or Ckgjss), the upper boundary of which occurs within 1 m of the mineral surface. These soils may have a weak vertic horizon (Bgjvj). They differ from Vertic Gray Brown 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.