Ecological site group DX035X01CESG10
Mesas and Benches - Sandy Grasslands and Shrublands - sandy
Last updated: 10/12/2022
Accessed: 05/02/2024
Ecological site group description
Key Characteristics
- Mesa and Benches
- Sandy Grasslands and Shrublands
- Soils are sands
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 ecological site group occurs on dunes, structural benches, plateaus, alluvial fans, mesas, sandsheets, and cuestas. Vegetated dunes are very common. Depending up on plant community and the presences or absence of disturbance, active dunes can become more prevalent. Runoff potential is very low to low.
Climate
The climate is characterized by hot summers and cool winters, which can be slightly modified by local topographic conditions, such as aspect. Large fluctuations in daily temperature are common. Mean annual high temperatures range from 61-71 degrees Fahrenheit and mean annual low temperatures range from 33-43 degrees Fahrenheit. Approximately 70-75% of moisture occurs as rain from October-March as convection thunderstorms and snow. Precipitation is extremely variable from month to month and from year to year but averages between 6 -12 inches. Snow packs are generally light and not persistent.
Soil features
This groups soils are classified as moderately to very deep torripsamments and are excessively drained. Runoff is low or very low on flatter slopes, however, sites with slopes greater than 20% have a medium runoff potential. These soils have a high wind and water erosion potential and are subject to blowing and drifting even when the sites are in the reference state. The soil temperature and moisture regimes are mesic and ustic aridic respectively. Surface and subsurface textures are generally fine sands, sands, and loamy sands. Soils are nonsaline and the water holding capacity is generally low (2 to 3 inches). Surface and subsurface rock fragments are unusual.
Vegetation dynamics
This ecological site group occurs on moderately deep to very deep, poorly developed soils found on vegetated dunes and sandsheets on structural benches, plateaus, mesas, and cuestas in Major Land Resource Area (MLRA) 35-The Colorado Plateau. Fourwing saltbush, sand sagebrush, or winterfat typically forms the dominant visual aspect. Small areas within intact communities may be subject to blowing; these areas are sparsely vegetated with dune vegetation including species such as purple sage, resin bush, and sandhill muhly. Utah juniper (0-5% canopy cover) may be found invading these plant communities when the site is in close proximity to a juniper stand.
These sites developed under Colorado Plateau climatic conditions and included natural influences of herbivory, fire, and climate. The natural disturbance regime consisted of fairly infrequent fires ignited by both natural causes and Native Americans. Fires are normally infrequent due to broken topography (i.e.,large expanses exposed rock in the landscape), the fact that warm season grasses are usually green during the thunderstorm season, and that few lightning strikes actually occur. It is estimated that the historic fire return interval was 35-100+ years depending on fine fuel accumulations (Howard, 2003).
This ecological site group has been grazed by domestic livestock since they were first introduced into the area. This livestock introduction, with its the use of fencing and the development of reliable water sources have influenced the disturbance regime historically associated with these ecological sites. Fires would typically only carry after several good moisture years created continuous fine fuels, however, the introduction of domestic livestock reduced these fine fuels, reducing fires periods. In addition to influencing this sites fire regime, improperly managed livestock grazing (i.e., continuous season long grazing, heavy stocking rates, etc.) can cause these sites to depart for the reference plant community. When this occurs, native perennial grasses and shrubs will decrease while invasive forbs and annual grasses will increase. Continued improper domestic livestock grazing will likely remove the native perennial grasses and shrubs from the system and create large bare interspaces, which can increase erosion, active duning, and opportunities for invasive plants to establish.
Other disturbance mechanisms include extended drought, changes in the site’s drainage patterns, alluvial deposits, insect herbivory, poorly managed off road vehicle (OHV) use, and prolonged rodent activity. These disturbances can either facilitate the transition into different plant communities or the transition from one stable state to another, depending on severity, duration, and ecological site resilience.
As vegetation communities respond to changes in management or natural influences that move them to different ecological states, a return to previous states may not be possible without major energy inputs. The amount of energy needed to affect vegetative shifts depends on present biotic and abiotic features and the desired results.
Major Land Resource Area
MLRA 035X
Colorado Plateau
Correlated Map Unit Components
22960079, 22856739, 22592418, 22592292, 22592539, 22592678, 22592681, 22592558, 22592332, 22592699, 22592588, 22592488, 22592609, 22592490, 22592385, 22592386, 22592393, 22592398, 22592496, 22592744, 22592506, 22592623, 22592512, 22592634, 22966753, 22966750, 22967027, 22966737, 22966915
Stage
Provisional
Contributors
Vic Parslow
Keith Crossland
Harry Hosler
Jim Harrigan
Curtis Talbot
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