Ecological site group description

Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.

Physiography

This site occurs on summits of mesas, structural benches, and dip-slopes of cuestas on undulating plateaus. Slopes range from 1-15%, with occasional slopes up to 35%. It does not benefit from run-in moisture from adjacent areas nor does it suffer from excessive runoff. It occurs on all exposures. It is associated with sandstone rock outcrops.

Climate

The climate of the land resource unit is arid with warm summers and cool winters. Average annual precipitation ranges from 6 to 10 inches per year. 40 to 50 percent of the precipitation is received from October through early May. This precipitation comes as gentle rain or snow from frontal storms coming out of the Pacific Ocean. Snow is common from November through February. Generally no more than an inch or two of snow accumulates and usually melts within a day or two. The remaining precipitation, approximately 50 to 60 percent, is received from July through September as spotty, violent thunderstorms. The moisture for this precipitation originates in the Gulf of Mexico and the Pacific Ocean. Late May through late June is the driest period. The mean annual temperature ranges from 53 to 56 degrees Fahrenheit (F). The frost-free period (air temperature > 32 degrees F) ranges from 135 to 160 days (@ 50 percent probability). Strong winds are common, especially in the spring.

Soil features

Soils on this site are very shallow and well drained. They are formed in eolian, residuum and alluvium derived from sandstone. Surface textures include fine sand and channery loamy fine sand. Subsoil has textures of fine sandy loam, channery fine sandy loam, and channery loamy fine sand. Hard sandstone is at depths ranging from 8 to 10 inches. Permeability based on the most restrictive horizon above 20 inches is slow to very slow. Avaiable water capacity is very low. Runoff is medium to very high and the hazard of water erosion is moderate to severe. The hazard of soil blowing is severe. The soils are mildly to moderately alkaline (pH 7.4-8.4), non-saline to very slightly saline (EC 0-4), and non-to slightly sodic (SAR 0-13).

Vegetation dynamics

Reference State
The plant community on this site is primarily grasses and shrubs with some forbs. There is a mixture of both cool and warm season plants.
Plant species most likely to invade or increase on this site when it deteriorates are broom snakeweed, alkali sacaton, shadscale and annual forbs.

Major Land Resource Area

MLRA 035X
Colorado Plateau

Stage

Provisional