Thin Claypan

Description

The Reference State represents the best estimate of the natural range of variability that dominated the dynamics in the Thin Claypan ecological site prior to European settlement. This site, in the Reference State, is dominated by a mix of cool-season rhizomatous wheatgrasses and warm-season shortgrasses. Heavy grazing will cause the plant community to transition to a community dominated by warm-season shortgrasses and a minor amount of cool-season rhizomatous wheatgrasses and needlegrasses. Cactus can increase dramatically and, in the western portion of the MLRA, greasewood can also establish. Erosion of the surface horizon is a potential outcome with heavy grazing. In pre-European times the primary disturbances included grazing by large ungulates and small mammals, and drought. Favorable growing conditions occurred during the spring and the warm months of June through August. Today a similar state can be found in areas where proper livestock use has occurred. Non-native cool-season grasses typically will not make up more than 20 percent of any plant community within this State.

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 soil(s) 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 State 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 gramma, buffalograss, and inland saltgrass. The 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.

Submodel