Ecological site group DX035X01EESG02
Green River Desert - Bottoms and Flats - run in
Last updated: 09/01/2021
Accessed: 05/02/2024
Ecological site group description
Key Characteristics
- Green River Desert
- Bottoms and Flats
- Extra water is from run-in or local water table
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 alluvial valleys, alluvial fans, flood plains, valleys, stream terraces, and valley flats. It typicallyoccurs on run-in sites that receive extra moisture from surrounding uplands, and may have a seasonally high water table within 72 inches of the soil surface. Run off is typically low. Slopes range from 0-8% and elevations are generally 4000-6600 ft.
Climate
The climate is characterized by hot summers and cool to warm winters, which can be slightly modified by local topographic conditions, such as aspect. Large fluctuations in daily temperatures are common. Mean annual high temperatures range from 63-71 degrees Fahrenheit and mean annual low temperatures range from 32-40 degrees Fahrenheit. Approximately 70-75% occurs as rain from March through October. On the average, April, May, and June are the driest months and August through October are the wettest months. Precipitation is extremely variable from month to month and from year to year but averages between 7-12 inches a year. Much of the summer precipitation occurs as convection thunderstorms. This is a run-in site that receives additional moisture from surrounding sites. Rare to occasional flooding occurs from April to September.
Soil features
The soils are very deep and moderately well to somewhat excessively well drained. Surface and subsurface textures can range from clay loams to sands. Typically soil surface fragments range from 0-8%. The soil temperature is regime mesic. The soil moisture regime is typically aridic (torric), but can be aridic ustic. Surface and subsurface textures range from silty loams and clays to sand. When a seasonally high water table and high salt content is present, high production of halophytic plants is possible. When this group is dominated by greasewood, soil salinities are high. When dominated by grasses, soil salinities are lower. Sandy soils in this group are generally less saline than the more loamy soils.
Vegetation dynamics
This group was historically dominated by shrubs, greasewood on the loamy sites and fourwing saltbush on sandy soils, and a diverse perennial understory, including seepweed, pale evening primrose, Indian ricegrass, Sporobolus spp, and James' galleta. The historic fire return interval is presumed to be about 35-100 years (Anderson 2004). Shrubs and native grasses would have resprouted within one year following fire and maintained dominance of the site. There is no evidence that prolonged drought would dramatically alter the species composition of the site in reference condition, although production is expected to be lower.
Today this site often burns less frequently due to fire suppression efforts and reduced fine fuel loads resulting from livestock grazing. In addition, excessive livestock grazing during the spring and summer can cause native grasses and forbs to lose vigor or disappear from the community completely.
Cheatgrass and Russian thistle commonly establish on this site, and Tamarisk can become dominant when the site occurs near stream and drainage corridors. When the ecological processes are altered due to improper grazing, prolonged drought, altered fire regime, invasive species dominance, or other disturbances, alternative states can occur that differ from the historic reference state in both plant community structure and ecological function.
Major Land Resource Area
MLRA 035X
Colorado Plateau
Subclasses
Stage
Provisional
Contributors
Vic Parslow
Keith Crossland
Harry Hosler
Jim Harrigan
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