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 in the drainage or bottom positions on the landscape that have the potential to flood following storm events. The surface textures are loamy. The soils are deep and well drained. Slopes range from 0 to 5 percent.

Climate

The 35.2 Colorado Plateau Cold Desert Shrub - Grassland common resource area has a very dry and windy climate that is hot in the summer and cold in the winter. The annual precipitation averages between 6 and 10 inches. The soil moisture regime is typic-aridic and the soil temperature regime is mesic. A slight majority of the precipitation arrives during the late fall, winter, and early spring. This winter season moisture originates in the Pacific Ocean and arrives as rain, or sometimes snow, during widespread frontal storms of generally low intensity. The majority of the snow (average range of 1 to 17 inches) falls from December through February, but rarely lasts more than a few days. A seasonal drought occurs from late May through early July. Summer rains occur from July through September during brief intense local thunderstorms. The rain is sporadic in intensity and location. The moisture originates from the Gulf of Mexico in the early summer and the Gulf of California in the late summer/early fall. Windy conditions are common year round, but the winds are strongest and most frequent during the spring.

Soil features

These soils are stratified flow deposited soils that are deep and well drained, formed from mixed alluvium. The surface layer texture range from very fine sandy loam to sandy clay loam. The subsurface textures are typically loamy, but may have stratified layers coarser and finer textures. The soils are saline and/or sodic throughout the profile. Available water capacity is 6 to 13 inches. Effective rooting depth is more than 60 inches. Permeability is moderately slow to slow. Runoff is very slow to moderate.
Soil survey map unit components that have been correlated to this ecological site include:

Vegetation dynamics

This site has higher levels of accumulated salts due to position on the landscape and the underlying geology. Areas of increased salts seal the soil surface and prevent most plants from germinating. These areas become depressional and become sites for precipitation to accumulate, evaporate, and increase the salt content. The natural plant community of shrubs and grasses grow at the edges of these sites and in drifts of eolian sand that have accumulated, which allow the plants to germinate. The plant community is primarily made up
of mid and short grasses and shrubs with a relatively small percentage of forbs. In the original plant community there is a mixture of both cool and warm season grasses.

Major Land Resource Area

MLRA 035X
Colorado Plateau

Subclasses

• R035XB211AZ–Loamy Wash 6-10" p.z. Saline-Sodic

Correlated Map Unit Components

22341166, 22353903, 22353905, 22353909, 22353910, 22353912, 22353939, 22353941, 22354010, 22354012, 22353396, 22353455, 22396718, 22396719, 22396708, 22396816, 22484760, 22484761, 22484731

Stage

Provisional

Contributors

Curtis Talbot