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

The ecological sites in this group occur on structural benches, hillslopes, escarpments and dipslopes of cuestas. Run off is high (due to the shallow depth). Slopes typically range from 2-25%, but can be as steep as 70%. Elevations are generally 4800-8000 ft but range as low as 4200 ft.

Climate

The climate is characterized by hot summers and cool to warm winters. Large fluctuations in daily temperatures are common. Mean annual high temperatures range from 60-70 degrees Fahrenheit and mean annual low temperatures range from 32-40 degrees Fahrenheit. Approximately 70-75% of moisture occurs as rain from March through October. On the average, February, May, and June are the driest months and July through October are the wettest months. Precipitation is extremely variable from month to month and from year to year but averages between 9-16 inches. Much of the summer precipitation occurs as convection thunderstorms.

Soil features

The soils of this group are very shallow to shallow and well drained or somewhat excessively drained. They usually form in residuum derived from sandstone and siltstone, but may also form in colluvium, slope alluvium or eolian deposits over sandstone residuum. Textures range from to loamy sands to loams and may have few to many rock fragments on the soil surface and throughout the profile. The soil temperature and moisture regimes are mesic and ustic aridic (torric) or aridic ustic respectively. Soils are nonsaline to slightly saline, and the water holding capacity ranges from 0.4 to 2.5 inches of water for the entire profile. These soils are often in complex with rock outcrop.

Vegetation dynamics

The sites in this group are generally dominated by Utah juniper and twoneedle pinyon. There is no evidence to indicate that these sites historically maintained a short burn frequency. However, due to modern disturbances such as brush treatments, invasive species, and OHV use, the resilience of the plant communities may be at risk. Disturbances that reduce the presence of perennial grasses result in an opportunity for invasive annuals to enter into the system and may produce a fuel load for fire to become an ecological driver.

Drought and insects appear to be the main driving factors in many of the Pinyon/Juniper communities of Utah. Currently there is no documentation to indicate that this ecological site is affected by drought and/or insects, however, managers should be aware of the possible impacts of drought and insects on this ecological site. Betancourt et al. (1993), noted that Pinyon and Juniper woodlands in the southwest appear to be more susceptible to large die offs during droughts, than in other locations. As severe droughts persist, the Pinyon trees, being more susceptible to drought and insects, seem to die out, while the Utah juniper trees survive.

Major Land Resource Area

MLRA 035X
Colorado Plateau

Subclasses

• R035XY221UT–Semidesert Shallow Loam (Utah Juniper-Pinyon)
• R035XY315UT–Upland Shallow Loam (Pinyon-Utah Juniper) AWC <3

Correlated Map Unit Components

22960053, 22856705, 22857868, 22934173, 22933799, 22933803, 22934206, 22933849, 22933864, 22933866, 22933996, 22934117, 22934001, 22592654, 22592705, 22592703, 22592730

Stage

Provisional

Contributors

Vic Parslow
Keith Crossland
Curtis Talbot