RICHARD G. REIDER
RICHARD G. REIDER
Soils play an important role in agriculture, forestry, hydrology, engineering, and recreation
through their affect on runoff, erosion, and biotic productivity. The complex patterns of soil in
Wyoming (Plate 5) have developed through the interplay of geologic factors (rock type and
topography), climate, and biotic factors over time.
Most soils in high mountains and valleys of western, northern, and southern Wyoming are moist
throughout the year. They have formed under cool conditions in residual materials, colluvium,
and glacial deposits (light blue), but some areas have soils formed in alluvium and other
transported materials (blue). Some soils in low mountains of central, southern, and eastern parts
of the state have formed in residual materials under warmer conditions where the soil is moist only
in parts in the summer (gray blue). Others, in the extreme southwest, are usually dry during
summer (purple). These soils are found in association with similar soils (olive green) which are
dry in summer and have formed in residual and transported materials in basins and foothills. The
light-colored mountain and valley soils (gray blue and light blue) are generally Alfisols formed
under coniferous forests; the dark colored soils of the lower mountains are often Mollisols formed
under grassland or are Inceptisols.
Most basin and foothills areas of central and southern Wyoming have soils (tan and yellow) that are usually dry or may be moist in summer where maximum precipitation during the year occurs in the warm season. Many soils are Aridisols, soils of desert climates, but Inceptisols and Entisols are common on young landscapes. Mollisols are common in moist foothills areas under grass vegetation; desert shrubs dominate drier areas. Some have formed in residual materials, but soils in transported materials are common, such as along streams, on alluvial fans in foothills, or on sand dunes. Soils in dune sand are found northeast of Rock Springs.
Much of the Bighorn and Wind River basins have light-colored desert soils (fuschia and orange) similar to those described above for southern and central Wyoming, but the former are usually dry and occur in areas of lower annual precipitation. Desert shrubs are common and grasses are sparse. Similar to central and southern Wyoming, soils of the Bighorn and Wind River basins are often Aridisols. Soils in both residual and transported materials are common. Entisols and Inceptisols frequently occur in transported materials.
Grass-covered plains east of the Bighorn Mountains and Laramie Range have both dark and
light-colored soils (green). Precipitation is greater than in basins farther west. Peak precipitation
usually occurs in spring and summer; therefore, soils often retain some moisture in summer.
Darker colors reflect greater precipitation as well as denser grass vegetation. Mollisols are
dominant in eastern Wyoming on stable landscapes, but Entisols and some Inceptisols occur in
eroded areas or where there is frequent deposition of geologic materials. Some Aridisols occur in
the extreme northeast plains under sparse vegetation on shale.
Plate 5 was digitized from Roberts (1989) and is included with her permission.
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