Histosols - Keys to Soil Taxonomy

168 Keys to Soil Taxonomy

layers of mineral soil material of any thickness in the control section, below the surface tier.

Fluvaquentic Cryofibrists BCAE. Other Cryofibrists in which three-fourths or more of the fiber volume in the surface tier is derived from Sphagnum.

Sphagnic Cryofibrists BCAF. Other Cryofibrists.

Typic Cryofibrists

Haplofibrists

Key to Subgroups

BCCA. Haplofibrists that have a layer of water within the control section, below the surface tier.

Hydric Haplofibrists BCCB. Other Haplofibrists that have a lithic contact at the lower boundary of the control section.

Lithic Haplofibrists BCCC. Other Haplofibrists that have one or more limnic layers with a total thickness of 5 cm or more within the control section.

Limnic Haplofibrists BCCD. Other Haplofibrists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within the control section, below the surface tier.

Terric Haplofibrists BCCE. Other Haplofibrists that meet both of the following:

1. Have a total thickness of less than 50 cm of human-transported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer of mineral soil material 5 cm or more thick or two or more layers of mineral soil material of any thickness in the control section, below the surface tier.

Fluvaquentic Haplofibrists BCCF. Other Haplofibrists that have one or more layers of hemic and sapric materials with a total thickness of 25 cm or more in the control section, below the surface tier.

Hemic Haplofibrists BCCG. Other Haplofibrists.

Typic Haplofibrists

Sphagnofibrists

Key to Subgroups

BCBA. Sphagnofibrists that have a layer of water within the control section, below the surface tier.

Hydric Sphagnofibrists BCBB. Other Sphagnofibrists that have a lithic contact at the lower boundary of the control section.

Lithic Sphagnofibrists BCBC. Other Sphagnofibrists that have one or more limnic layers with a total thickness of 5 cm or more within the control section.

Limnic Sphagnofibrists BCBD. Other Sphagnofibrists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within the control section, below the surface tier.

Terric Sphagnofibrists BCBE. Other Sphagnofibrists that meet both of the following:

1. Have a total thickness of less than 50 cm of human-transported material in the surface horizons; and

Fluvaquentic Sphagnofibrists BCBF. Other Sphagnofibrists that have one or more layers of hemic and sapric materials with a total thickness of 25 cm or more in the control section, below the surface tier.

Hemic Sphagnofibrists BCBG. Other Sphagnofibrists.

Typic Sphagnofibrists

Folists

Key to Great Groups

BAA. Folists that have a cryic soil temperature regime.

Cryofolists, p. 169 BAB. Other Folists that have an aridic (or torric) soil moisture regime.

Torrifolists, p. 169 BAC. Other Folists that have an ustic or xeric soil moisture regime.

Ustifolists, p. 169

Histosols 169

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BAD. Other Folists.

Udifolists, p. 169

Cryofolists

Key to Subgroups

BAAA. Cryofolists that have a lithic contact within 50 cm of the soil surface.

Lithic Cryofolists BAAB. Other Cryofolists.

Typic Cryofolists

Torrifolists

Key to Subgroups

BABA. Torrifolists that have a lithic contact within 50 cm of the soil surface.

Lithic Torrifolists BABB. Other Torrifolists.

Typic Torrifolists

Udifolists

Key to Subgroups

BADA. Udifolists that have a lithic contact within 50 cm of the soil surface.

Lithic Udifolists BADB. Other Udifolists.

Typic Udifolists

Ustifolists

Key to Subgroups

BACA. Ustifolists that have a lithic contact within 50 cm of the soil surface.

Lithic Ustifolists BACB. Other Ustifolists.

Typic Ustifolists

Hemists

Key to Great Groups

BEA. Hemists that have a sulfuric horizon within 50 cm of the soil surface.

Sulfohemists, p. 170

BEB. Other Hemists that have sulfidic materials within 100 cm of the soil surface.

Sulfihemists, p. 170 BEC. Other Hemists that have a horizon 2 cm or more thick in which humilluvic material constitutes one-half or more of the volume.

Luvihemists, p. 170 BED. Other Hemists that have a cryic soil temperature regime.

Cryohemists, p. 169 BEE. Other Hemists.

Haplohemists, p. 169

Cryohemists

Key to Subgroups

BEDA. Cryohemists that have a layer of water within the control section, below the surface tier.

Hydric Cryohemists BEDB. Other Cryohemists that have a lithic contact at the lower boundary of the control section.

Lithic Cryohemists BEDC. Other Cryohemists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within the control section, below the surface tier.

Terric Cryohemists BEDD. Other Cryohemists that meet both of the following:

1. Have a total thickness of less than 50 cm of human-transported material in the surface horizons; and

Fluvaquentic Cryohemists BEDE. Other Cryohemists.

Typic Cryohemists

Haplohemists

Key to Subgroups

BEEA. Haplohemists that have a layer of water within the control section, below the surface tier.

Hydric Haplohemists

170 Keys to Soil Taxonomy

BEEB. Other Haplohemists that have a lithic contact at the lower boundary of the control section.

Lithic Haplohemists BEEC. Other Haplohemists that have one or more limnic layers with a total thickness of 5 cm or more within the control section.

Limnic Haplohemists BEED. Other Haplohemists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within the control section, below the surface tier.

Terric Haplohemists BEEE. Other Haplohemists that meet both of the following:

1. Have a total thickness of less than 50 cm of human-transported material in the surface horizons; and

Fluvaquentic Haplohemists BEEF. Other Haplohemists that have one or more layers of fibric materials with a total thickness of 25 cm or more in the control section, below the surface tier.

Fibric Haplohemists BEEG. Other Haplohemists that have one or more layers of sapric materials with a total thickness of 25 cm or more below the surface tier.

Sapric Haplohemists BEEH. Other Haplohemists.

Typic Haplohemists

Luvihemists

Key to Subgroups

BECA. All Luvihemists (provisionally).

Typic Luvihemists

Sulfihemists

Key to Subgroups

BEBA. Sulfihemists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within the control section, below the surface tier.

Terric Sulfihemists BEBB. Other Sulfihemists.

Typic Sulfihemists

Sulfohemists

Key to Subgroups

BEAA. All Sulfohemists (provisionally).

Typic Sulfohemists

Saprists

Key to Great Groups

BDA. Saprists that have a sulfuric horizon within 50 cm of the soil surface.

Sulfosaprists, p. 171 BDB. Other Saprists that have sulfidic materials within 100 cm of the soil surface.

Sulfisaprists, p. 171 BDC. Other Saprists that have a cryic soil temperature regime.

Cryosaprists, p. 170 BDD. Other Saprists.

Haplosaprists, p. 171

Cryosaprists

Key to Subgroups

BDCA. Cryosaprists that have a lithic contact at the lower boundary of the control section.

Lithic Cryosaprists BDCB. Other Cryosaprists that have one or more limnic layers with a total thickness of 5 cm or more within the control section.

Limnic Cryosaprists BDCC. Other Cryosaprists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within the control section, below the surface tier.

Terric Cryosaprists BDCD. Other Cryosaprists that meet both of the following:

1. Have a total thickness of less than 50 cm of human-transported material in the surface horizons; and

Fluvaquentic Cryosaprists BDCE. Other Cryosaprists.

Typic Cryosaprists

Histosols 171

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Haplosaprists

Key to Subgroups

BDDA. Haplosaprists that have a lithic contact at the lower boundary of the control section.

Lithic Haplosaprists BDDB. Other Haplosaprists that have one or more limnic layers with a total thickness of 5 cm or more within the control section.

Limnic Haplosaprists BDDC. Other Haplosaprists that have both:

1. Throughout a layer 30 cm or thick that has its upper boundary within the control section, an electrical conductivity of 30 dS/m or more (1:1 soil:water) for 6 months or more during normal years; and

2. A layer of mineral soil material 30 cm or more thick that has its upper boundary within the control section, below the surface tier.

Halic Terric Haplosaprists BDDD. Other Haplosaprists that have, throughout a layer 30 cm or more thick that has its upper boundary within the control section, an electrical conductivity of 30 dS/m or more (1:1 soil:water) for 6 months or more during normal years.

Halic Haplosaprists BDDE. Other Haplosaprists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within the control section, below the surface tier.

Terric Haplosaprists BDDF. Other Haplosaprists that meet both of the following:

1. Have a total thickness of less than 50 cm of human-transported material in the surface horizons; and

Fluvaquentic Haplosaprists BDDG. Other Haplosaprists that have one or more layers of fibric or hemic materials with a total thickness of 25 cm or more in the control section, below the surface tier.

Hemic Haplosaprists BDDH. Other Haplosaprists.

Typic Haplosaprists

Sulfisaprists

Key to Subgroups

BDBA. Sulfisaprists that have a layer of mineral soil material 30 cm or more thick that has its upper boundary within the control section, below the surface tier.

Terric Sulfisaprists BDBB. Other Sulfisaprists.

Typic Sulfisaprists

Sulfosaprists

Key to Subgroups

BDAA. All Sulfosaprists (provisionally).

Typic Sulfosaprists

Wassists

Key to Great Groups

BBA. Wassists that have, in all horizons within 100 cm of the soil surface, an electrical conductivity of less than 0.2 dS/m in a 1:5 (soil:water), by volume, supernatant (not extract).

Frasiwassists, p. 171 BBB. Other Wassists that have a horizon or horizons, with a combined thickness of at least 15 cm within 50 cm of the soil surface, that contain sulfidic materials.

Sulfiwassists, p. 172 BBC. Other Wassists.

Haplowassists, p. 172

Frasiwassists

Key to Subgroups

BBAA. Frasiwassists that:

1. Have more thickness of fibric soil materials than any other kind of organic soil materials either:

a. In the organic parts of the subsurface tier if there is no continuous layer of mineral soil material 40 cm or more thick that has its upper boundary within the subsurface tier; or

b. In the combined thickness of the organic parts of the surface and subsurface tiers and there is a continuous layer of mineral soil material 40 cm or more thick that has its upper boundary within the subsurface tier; and

172

2. Do not have sulfidic materials within 100 cm of the soil surface.

Fibric Frasiwassists BBAB. Other Frasiwassists that have more thickness of sapric soil materials than any other kind of organic soil materials either:

1. In the organic parts of the subsurface tier if there is no continuous layer of mineral soil material 40 cm or more thick that has its upper boundary within the subsurface tier; or 2. In the combined thickness of the organic parts of the surface and subsurface tiers and there is a continuous layer of mineral soil material 40 cm or more thick that has its upper boundary within the subsurface tier.

Sapric Frasiwassists BBAC. Other Frasiwassists.

Typic Frasiwassists

Haplowassists

Key to Subgroups

BBCA. Haplowassists that have a horizon or horizons, with a combined thickness of 15 cm within 100 cm of the soil surface, that contain sulfidic materials.

Sulfic Haplowassists BBCB. Other Haplowassists that have more thickness of fibric soil materials than any other kind of organic soil materials either:

Fibric Haplowassists BBCC. Other Haplowassists that have more thickness of sapric soil materials than any other kind of organic soil materials either:

Sapric Haplowassists BBCD. Other Haplowassists.

Typic Haplowassists

Sulfiwassists

Key to Subgroups

BBBA. Sulfiwassists that have more thickness of fibric soil materials than any other kind of organic soil materials either:

1. In the organic parts of the subsurface tier if there is no continuous layer of mineral soil material 40 cm or more thick that has its upper boundary within the subsurface tier;

2. In the combined thickness of the organic parts of the surface and subsurface tiers and there is a continuous layer of mineral soil material 40 cm or more thick that has its upper boundary within the subsurface tier.

Fibric Sulfiwassists BBBB. Other Sulfiwassists that have more thickness of sapric soil materials than any other kind of organic soil materials either:

Sapric Sulfiwassists BBBC. Other Sulfiwassists.

Typic Sulfiwassists

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NI C

Key to Suborders

KA. Inceptisols that have one or more of the following:

1. In a layer above a densic, lithic, or paralithic contact or in a layer at a depth between 40 and 50 cm from the mineral soil surface, whichever is shallower, aquic conditions for some time in normal years (or artificial drainage) and one or more of the following:

a. A histic epipedon; or

b. A sulfuric horizon within 50 cm of the mineral soil surface; or

c. A layer directly under the epipedon, or within 50 cm of the mineral soil surface, that has, on faces of peds or in the matrix if peds are absent, 50 percent or more chroma of either:

(1) 2 or less if there are redox concentrations; or (2) 1 or less; or

d. Within 50 cm of the mineral soil surface, enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being irrigated; or

2. An exchangeable sodium percentage (ESP) of 15 or more (or a sodium adsorption ratio [SAR] of 13 or more) in half or more of the soil volume within 50 cm of the mineral soil surface, a decrease in ESP (or SAR) values with increasing depth below 50 cm, and ground water within 100 cm of the mineral soil surface for some time during the year.

Aquepts, p. 173 KB. Other Inceptisols that have a gelic soil temperature regime.

Gelepts, p. 185 KC. Other Inceptisols that have a cryic soil temperature regime.

Cryepts, p. 180 KD. Other Inceptisols that have an ustic soil moisture regime.

Ustepts, p. 195 KE. Other Inceptisols that have a xeric soil moisture regime.

Xerepts, p. 203

KF. Other Inceptisols.

Udepts, p. 187

Aquepts

Key to Great Groups

KAA. Aquepts that have a sulfuric horizon within 50 cm of the mineral soil surface.

Sulfaquepts, p. 179 KAB. Other Aquepts that have, within 100 cm of the mineral soil surface, one or more horizons in which plinthite or a cemented diagnostic horizon either forms a continuous phase or constitutes one-half or more of the volume.

Petraquepts, p. 179 KAC. Other Aquepts that have either:

1. A salic horizon; or

2. In one or more horizons with a total thickness of 25 cm or more within 50 cm of the mineral soil surface, an exchangeable sodium percentage (ESP) of 15 or more (or a sodium adsorption ratio [SAR] of 13 or more) and a decrease in ESP (or SAR) values with increasing depth below 50 cm.

Halaquepts, p. 178 KAD. Other Aquepts that have a fragipan within 100 cm of the mineral soil surface.

Fragiaquepts, p. 177 KAE. Other Aquepts that have a gelic soil temperature regime.

Gelaquepts, p. 177 KAF. Other Aquepts that have a cryic soil temperature regime.

Cryaquepts, p. 174 KAG. Other Aquepts that have, in one or more layers at least 25 cm thick (cumulative) within 100 cm of the mineral soil surface, 25 percent or more (by volume) recognizable bioturbation, such as filled animal burrows, wormholes, or casts.

Vermaquepts, p. 179

Inceptisols

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