Thin Claypan

Description

The Reference State (1.0) represents what is believed to show the natural range of variability that dominated the dynamics of this ecological site prior to European settlement. This site in the Reference State (1.0) is dominated by a mix of cool-season and warm-season grasses and shrubs. In pre-European times, the primary disturbance mechanisms included periodic fire and grazing by large herding ungulates. Timing of fires and grazing coupled with weather events dictated the dynamics that occurred within the natural range of variability. Taller cool-season grasses would have declined and a corresponding increase in short statured grass and clubmoss would have occurred. Today, a similar state can be found on areas that are properly managed with grazing and sometimes on areas receiving occasional short periods of rest.

Submodel

Description

The Shrub/Sod State (2.0) is dominated by shortgrass species, cactus, clubmoss, and shrubs. This State is the result of grazing management that does not provide adequate recovery time for mid-statured cool-season grasses. The hydrologic function of this state is dramatically altered. This State is very resistant to change through grazing management alone.

Submodel

Description

The soils definition of a slick spot is a small area of soil having a puddled, crusted, or smooth surface and an excess of exchangeable sodium. The soil is generally silty or clayey, is slippery when wet, and is low in productivity.

Sodium naturally occurs in the parent materials and soils of this site. Sodium accumulates at the surface of the slick spots through the processes of evaporation and evapotranspiration. When water stands on this site, it will eventually evaporate and draw more sodium near or to the surface. It can also be caused by evapotranspiration, wherein vegetation draws moisture from the soil profile, leaving sodium at or near the surface.

Slick spots are currently considered a unique and separate sodium-affected soil component, occurring in a soil map unit, and is identified as a “Non-Site.” Slick spots will typically be seen intermingled within the Thin Claypan ecological site. A vegetation transition to and from the Slick Spot may or may not exist.

The plant community on these soils is typically very sparse, and consists of shallow-rooted perennial grasses, grass-likes, forbs, and shrubs. Brittle cactus and pricklypear tend to persist on these soils, as do Sandberg bluegrass, sedges, blue grama, and inland saltgrass. Wyoming big sagebrush often persists on slick spots, as will black greasewood. The vegetative production will vary from almost none to 100 to 300 pounds per acre. Nostoc, a common genus of cyanobacteria, will almost always be found on slick spots. When dry, it is dark-colored and tends to look like a small, dry forb leaf. When wet, it swells up into a conspicuous, dark green jellylike mass. Nostoc species are native and are not considered a noxious plant or pest.