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16 Cards in this Set
- Front
- Back
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What are the master organic horizons and what are they differentiated by? |
LFH + O - differentiated by: moisture regimes, botanical origins of organics, soil & physiologic materials |
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What is an O horizon? |
- organic horizon developed in a wetland environment - humus formation is influenced by the water table @ or near surface - must be > 17% organic carbon or > 35% organic matter - topography: depressional to level - drainage: poor to very poor - water table: at or near ground surface during frost free time - origin of materials: aquatic (hydrophytic) vegetation |
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What is the master mineral horizon? |
A - < 17% organic carbon forming at or near the soil surface - only mineral horizon used in humus form classification |
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Describe the various properties of an LFH horizon: |
- physiography: sloping to level - drainage: rapid to imperfect - water table: absent (can fluctuate with input) - origin of materials: nonhydrophytic vegetation |
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What is a humus form? |
LFH + Ah |
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What are the characteristics of a mor? |
- matted Fm horizon - abrupt boundary between mineral soil and organic layer - e.g. coniferous forest: low pH, fungal mycorrhizae, slow rate |
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What are the characteristics of a moder? |
- loosely structured Fz and/or Fa horizon - more gradual boundary between mineral soil and organic layer - e.g. deciduous forest: neutral pH, microbial activity, soil fauna, moderate decomposition rate |
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What are the characteristics of a mull? |
- F & H horizons thin or absent - combined thickness of F & H horizons < 2 cm with Ah greater than 2 cm because decomposition is rapid - e.g. grasslands: neutral pH, microbial activity, soil fauna and rapid decomposition rate |
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Of |
- lots of poorly decomposed plant residues - class 1-4 von post |
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Om |
- between Of and Oh - class 5 or 6 von post |
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Oh |
- well decomposed plant residues - class 7 + von post |
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suffixes: - i - p - u - w - y - f |
i = intermixed mineral particles p = plowed u = substantially altered by natural processes w = wood > 35% volume of solids y = affected by cryoturbation (associated with permafrost) f = fragments |
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What characteristics are key when describing soils? |
- mottles (abundance, size, contrast, colour) - structure (structureless, blocklike, platelike, prismlike) + grade, class, kind - consistence: loose to very firm (strength of peds) - root density - coarse fragments - boundary - thickness range |
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What is soil erosion influenced? |
- climate - topography - depth to water restricting layer - surface soil detachability - surface coarse fragments ( fewer % > erosion risk) - subsoil permeability |
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What does soil compaction and puddling do? |
- destroys macropores and reduces soil structure |
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What are some soil characteristics of this area? |
- moist, cool climate with abundant rainfall - high humidity restricts evapotranspiration rates - soil moist to wet throughout the year |
