Soil Survey Technical Note No' 9

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Soil Survey Technical Note No. 9

• Populating Taxonomic Moisture Class and Subclass
  in NASIS

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• Moisture class and subclass are useful for
  general correlation purposes
• Also used in some NASIS forestry interpretations

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• NASIS Moisture class Moisture regime
• NASIS Definition
• Soil moisture classes are unique to the family
  classification, though not included specifically
  in the name, this is a mechanism to provide clear
  identification of the actual moisture regime.

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• NASIS Moisture subclass loosely equivalent to
  the taxonomic subgroup
• NASIS Definition
• Soil moisture subclasses identify soil moisture
  regime intergrades or extragrades, except for
  typic, and are taxonomic subgroup criteria
  whether included or not in the name of the
  subgroup.
• The definition of each subclass is
  dependent upon the specific taxonomic great group
  to which it is attached.
• ( TH Typic is an allowed subclass but it is
  neither an intergrade nor extragrade. )

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Moisture Regimes

• Not always apparent in the class name
  (Cryopsamments can have aridic, ustic, xeric, or
  udic regime)
• Ustolls may have an aridic or ustic regime
• Xerolls may have an aridic or xeric regime
• May need to refer to the series concept (OSD)

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Moisture Subclass

• The subclass is apparent from the taxonomic class
  when it is the subgroup name
• Ustic Haplargids Oxyaquic Haplustolls
• When not part of the taxonomic class name, it is
  whatever subgroup criteria that it fits when the
  keying sequence is disregarded.
• A Haplustoll fits the Oxyaquic subgroup, but
  Cumulic Haplustolls keys out first Moisture
  subclass is Oxyaquic
• -A Haplustalf fits the Udic subgroup, but
  Lamellic Haplustalfs keys out first Moisture
  subclass is Udic

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Moisture Subclass

• Sometimes the classification allows more than one
  possible class-subclass
• Aridic Calciustolls have either an aridic
  taxonomic moisture class and an ustic subclass or
  an ustic taxonomic moisture class and an aridic
  subclass. You must consider the series concept
  to determine for sure.
• When the soil does not fit any of the
  moisture-related subgroups, it is in the typic
  subclass.

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Moisture Subclass

• In general if a moisture subclass is not defined
  for a great group, it is not proper to use the
  subclass for any soils in that great group.
• A udic subgroup (udic-xeric) is not defined for
  any of the Xerolls great groups
• A udic subgroup (udic-ustic) is not defined for
  frigid soils in any of the Ustolls great groups
• An aridic subgroup (aridic-ustic or aridic-xeric)
  is not defined for any of the Cryolls or Cryepts
  great groups.

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Moisture Subclass

• Cryic Soils Pose Special Challenges
• Cryolls and Cryepts may cover a wide range in
  climate, but few moisture-related subgroups are
  recognized.
• Cryolls may have an aridic, ustic, xeric, or udic
  regime.
• The only recognized moisture subgroups
  (well-drained) are xeric and ustic

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Possible Moisture Subclasses for Cryolls

• (Ustic/Xeric Cryolls have an ustic/xeric
  regime)
• Classification subclass regime
• Ustic Cryolls typic ustic
• oxyaquic ustic
• aquic ustic
• Xeric Cryolls typic xeric
• oxyaquic xeric
• aquic xeric
• Typic Cryolls typic udic
• oxyaquic udic
• aquic udic

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Possible Moisture Subclasses for Cryalfs and
Cryepts

• (Ustic Cryalfs/Cryepts dry for gt45 days
• (Xeric Cryalfs/Cryepts have a xeric regime)
• Classification subclass regime
• Ustic Cryalfs/Cryepts typic ustic
• ustic udic
• oxyaquic ustic
• aquic ustic
• Xeric Cryalfs/Cryepts typic xeric
• oxyaquic xeric
• aquic xeric
• Typic Cryalfs/Cryepts typic udic
• oxyaquic udic
• aquic udic

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Ustic Cryalfs
Typic Cryalfs
USTIC REGIME
UDIC REGIME
dry
moist
Typic Cryolls
Ustic Cryolls
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• Ustic Cryalfs can have a udic regime
• Ustic Cryolls cannot have a udic regime
• Ustic Cryalfs could be mapped with Typic Cryolls,
  each having the same soil climate.