Histosols and Gelisols at Moose Pass, Alaska
Moose Pass is an Alaska community nestled on the shores of Trail Lake in on the Kenai Peninsula, Alaska. The trails of the Chugach National Forest lead along pristine mountain lakes, bountiful berry patches, and breathtaking alpine vistas. Located one hundred miles south of Anchorage and thirty miles north of Seward.
The valleys are dominated by Histosols and Gelisols. In both the World Reference Base for Soil Resources (WRB) and the USDA soil taxonomy, a Histosol--or an organic soil--is a soil consisting primarily of decomposed plant material. They are defined as having 40 centimeters (16 in) or more of organic soil material in the upper 80 centimeters (31 in). Organic soil material has an organic carbon content (by weight) of 12 to 18 percent, or more, depending on the clay content of the soil. These materials include muck (sapric soil material), mucky peat (hemic soil material), or peat (fibric soil material). Aquic conditions or artificial drainage are required.
Histosols have very low bulk density and are poorly drained because the organic matter holds water very well. Most are acidic and many are very deficient in major plant nutrients which are washed away in the consistently moist soil. Histosols are known by various other names in other countries, such as peat or muck. In the Australian Soil Classification, Histosols are called Organosols. Histosols form whenever organic matter forms at a more rapid rate than it is destroyed. This occurs because of restricted drainage precluding aerobic decomposition, and the remains of plants and animals remain within the soil.
Gelisols are underlain by permafrost. Freezing and thawing are important processes in Gelisols. Diagnostic horizons may or may not be present. Permafrost influences pedogenesis by acting as a barrier to the downward movement of the soil solution. Cryoturbation (frost mixing) is an important process in many Gelisols and results in irregular or broken horizons, involutions, organic matter accumulation on the permafrost table, oriented rock fragments, and silt caps on rock fragments. Cryoturbation occurs when two freezing fronts, one from the surface and the other from the permafrost, merge during freeze-back in the autumn. Ice segregation is an important property of gelic materials and occurs when the soil solution migrates toward ice, increasing the volume of ice. Volume changes also occur as the water freezes.
For additional information about soil classification using USDA-NRCS Soil Taxonomy, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/keys-...
or;
www.nrcs.usda.gov/resources/guides-and-instructions/soil-...
For more information about Hydric Soils and their Field Indicators, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/field...
For more photos related to soils and landscapes visit:
Histosols and Gelisols at Moose Pass, Alaska
Moose Pass is an Alaska community nestled on the shores of Trail Lake in on the Kenai Peninsula, Alaska. The trails of the Chugach National Forest lead along pristine mountain lakes, bountiful berry patches, and breathtaking alpine vistas. Located one hundred miles south of Anchorage and thirty miles north of Seward.
The valleys are dominated by Histosols and Gelisols. In both the World Reference Base for Soil Resources (WRB) and the USDA soil taxonomy, a Histosol--or an organic soil--is a soil consisting primarily of decomposed plant material. They are defined as having 40 centimeters (16 in) or more of organic soil material in the upper 80 centimeters (31 in). Organic soil material has an organic carbon content (by weight) of 12 to 18 percent, or more, depending on the clay content of the soil. These materials include muck (sapric soil material), mucky peat (hemic soil material), or peat (fibric soil material). Aquic conditions or artificial drainage are required.
Histosols have very low bulk density and are poorly drained because the organic matter holds water very well. Most are acidic and many are very deficient in major plant nutrients which are washed away in the consistently moist soil. Histosols are known by various other names in other countries, such as peat or muck. In the Australian Soil Classification, Histosols are called Organosols. Histosols form whenever organic matter forms at a more rapid rate than it is destroyed. This occurs because of restricted drainage precluding aerobic decomposition, and the remains of plants and animals remain within the soil.
Gelisols are underlain by permafrost. Freezing and thawing are important processes in Gelisols. Diagnostic horizons may or may not be present. Permafrost influences pedogenesis by acting as a barrier to the downward movement of the soil solution. Cryoturbation (frost mixing) is an important process in many Gelisols and results in irregular or broken horizons, involutions, organic matter accumulation on the permafrost table, oriented rock fragments, and silt caps on rock fragments. Cryoturbation occurs when two freezing fronts, one from the surface and the other from the permafrost, merge during freeze-back in the autumn. Ice segregation is an important property of gelic materials and occurs when the soil solution migrates toward ice, increasing the volume of ice. Volume changes also occur as the water freezes.
For additional information about soil classification using USDA-NRCS Soil Taxonomy, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/keys-...
or;
www.nrcs.usda.gov/resources/guides-and-instructions/soil-...
For more information about Hydric Soils and their Field Indicators, visit:
www.nrcs.usda.gov/resources/guides-and-instructions/field...
For more photos related to soils and landscapes visit: