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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.
MLRA notes
Major Land Resource Area (MLRA): 034A–Cool Central Desertic Basins and Plateaus
Major Land Resource Area (MLRA): 34A-Cool Central Desertic
Basins and Plateaus
For further information regarding MLRAs, refer to:
http://soils.usda.gov/survey/geography/mlra/index.htmlLRU notes
Land Resource Unit (LRU) 34A-10:
• Moisture Regime: aridic ustic
• Temperature Regime: frigid
• Dominant Cover: rangeland
• Representative Value (RV) Effective Precipitation: 12-16 inches
• RV Frost-Free Days: 75-95 daysClassification relationships
Relationship to Other Established Classification Systems
Ecoregions (EPA):
Level I: 10 North American Deserts
Level II: 10.1 Cold Deserts
Level III: 10.1.4 Wyoming Basin
The potential natural vegetation is classified as Type 235 Cottonwood Willow in Forest Cover Types in North America Society of American Foresters, 1954.Ecological site concept
Site receives additional water.
Soils are:
not saline or saline-sodic.
Deep to very deep, not skeletal within 20” of soil surface.
Season water table <12” along seeps and springs
Not strongly or violently effervescent in surface mineral 10”.
Slope is < 30%.
Clay content is = <35% in surface mineral 4”.
Site does not have an argillic horizon with > 35% clayAssociated sites
R034AY298CO Rolling Loam
occurs on the upper terrace outside of the floodplain
Similar sites
R034AY374WY Subirrigated High Plains Southeast (Sb)
occurs in adjoining LRU in Wyoming
Table 1. Dominant plant species
Tree (1) Populus angustifolia
Shrub Not specified
Herbaceous (1) Leymus cinereus
(2) Hesperostipa comataPhysiographic features
This site will usually occur on level to nearly level land along perennial or intermittent streams near seeps, springs, and sloughs.
Table 2. Representative physiographic features
Landforms (1) Alluvial fan
(2) Stream terrace
(3) Flood plain
Runoff class Negligible to high Flooding frequency Rare to occasional Ponding frequency None Elevation 5500 – 7000 ft Slope 1 – 10 % Water table depth 12 – 60 in Aspect Aspect is not a significant factor Climatic features
The climate is arid to semi-arid. Winters are cold and summers are warm. The average annual precipitation ranges from 12 to 16 inches.
About half of this precipitation comes in the form of winter snow and spring rain. Spring and fall are peak periods of precipitation. July is usually the driest month. The distribution of precipitation and relatively low spring temperatures favor production of cool season plants.
Plants begin growth in late April. The optimum growth period is from mid-May to late June unless summer rains occur and are effective in maintaining plant growth. The growing season for native plants is about 110 days. There may be a second growth period in the fall due to a fall precipitation peak.
The average annual temperature ranges from 42 to 45 degrees Fahrenheit. The frost-free period ranges from 75 to 95 days.Table 3 Representative climatic features
Frost-free period (characteristic range) 60-70 days Freeze-free period (characteristic range) 90-90 days Precipitation total (characteristic range) 10-20 in Frost-free period (actual range) 50-70 days Freeze-free period (actual range) 80-100 days Precipitation total (actual range) 10-20 in Frost-free period (average) 60 days Freeze-free period (average) 90 days Precipitation total (average) 10 in Characteristic rangeActual rangeBarLineFigure 1. Monthly precipitation range
Characteristic rangeActual rangeBarLineFigure 2. Monthly minimum temperature range
Characteristic rangeActual rangeBarLineFigure 3. Monthly maximum temperature range
BarLineFigure 4. Monthly average minimum and maximum temperature
Figure 5. Annual precipitation pattern
Figure 6 Annual average temperature pattern
Climate stations used
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(1) MAYBELL [USC00055446], Maybell, CO
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(2) CRAIG MOFFAT CO AP [USW00024046], Craig, CO
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(3) BROWNS PARK STORE [USC00051018], Maybell, CO
">Influencing water features
The characteristics of these soils have influence from ground water that is within 12 inches of the soil surface and will be just below the surface for all of the growing season. Water over the surface from run-in may occur but only for short periods of time. These soils are moderately deep to deep and poorly to somewhat well drained.
Wetland description
N/A
Soil features
Soils of this type are those bordering major streams and tributaries. Like the vegetation, soils are highly variable. They are commonly mapped as broadly defined units i.e. fluvaquents.
Table 4. Representative soil features
Parent material (1) Alluvium
Surface texture (1) Loam
(2) Clay loam
(3) Sandy loam
Drainage class Somewhat poorly drained to moderately well drained Permeability class Moderately slow to moderate Soil depth 40 – 60 in Surface fragment cover <=3" Not specified Surface fragment cover >3" 0 – 15 % Available water capacity
(Depth not specified)5 – 7.5 in Soil reaction (1:1 water)
(Depth not specified)6.6 – 7.8 Subsurface fragment volume <=3"
(Depth not specified)0 – 20 % Subsurface fragment volume >3"
(Depth not specified)0 – 20 % Ecological dynamics
The plant species composition is highly variable. Successionally it is a sub-climax stage of the hydro-sere or a post-climax association (F. E. Clements). This type occupies the more mature flood-plains of the Green, Yampa, White, Colorado, Dolores, Uncompahgre, Gunnison, La Plata, San Juan, Rio Grande and other major streams and tributaries. Elevations are generally below 7000 feet. For conservation planning purposes, this type will not include the very narrow stream bottoms at higher elevations. Total annual production varies greatly. The under story canopy cover, periodic flooding, sediment, water-table, salinity and soils create significant variability in the nature of the plant communities. Therefore determination of annual production of grazable plants and initial stocking rates must be made on site at the time land users are assisted with resource planning.
State and transition model
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textState 1
ReferenceCottonwood/Cool Season Bunchgrass:
The interpretive plant community for this site is the Reference Plant Community. The major grasses include basin wildrye, needle and thread, western wheatgrass, and, Indian ricegrass. Narrowleaf cottonwood is the major woody plant. Other woody plants that may occur include Wyoming and Mountain big sagebrush, rubber rabbitbrush, and snowberry.
This state is extremely stable and well adapted to the Cool Central Desertic Basins and Plateaus climate. The diversity in plant species allows for high drought resistance. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity).State 2
Mature Cottonwood / Rhizomatous WheatgrassThis plant community is the result of continuous season long grazing of reference. Desirable bunchgrasses such as basin wildrye and needle and thread have been greatly reduced. Young cottonwoods have been browsed and replaced with Wyoming and Mountain big sagebrush, rubber rabbitbrush and snowberry.
The soils of this state are moderately protected. The loss of deep rooted perennial bunchgrasses have affected biotic integrity may be reduced due to low vegetative production. The watershed is functioning ,but is at risk of rapidly degrading with improper management.State 3
Decadent Cottonwood / Introduced or Invasive SpeciesThis plant community is a result of heavy continuous season-long grazing, noxious weed invasion, and flood control. The plant community is primarily composed of smooth brome, Kentucky bluegrass and non native forbs such as burdock, Canada thistle, and leafy spurge. Woody species that remain are tolerant of heavy grazing disturbance and include Wyoming and Mountain big sagebrush, rubber rabbitbrush, and snowberry. Cottonwoods have low vigor and recruitment.
This state is unstable and vulnerable to excessive erosion. The biotic integrity of this plant community is at risk or non-functioning. The watershed is usually at risk or non-functioning as bare ground increases.Transition T1A
State 1 to 2• Continuous Season-long Grazing will convert the plant community to the Mature Cottonwood/Rhizomatous Wheatgrass
Transition T1B
State 1 to 3• Heavy Continuous Season-long Grazing with Noxious weed invasion and flood control will convert the plant community to the Decadent Cottonwood/Introduced or Invasive Species
Restoration pathway R2A
State 2 to 1• Prescribed Grazing or Long-term Prescribed Grazing will return this state to near Historic Climax Plant Community –Cottonwood/Cool Season Bunchgrass.
Transition T2A
State 2 to 3• Heavy Continuous Season-long Grazing with Noxious weed invasion and flood control will convert the plant community to the Decadent Cottonwood/Introduced or Invasive Species
Restoration pathway R3A
State 3 to 1• Long Term Prescribed Grazing, Noxious Weed Control, Return of Flood Water, Reseeding, and Replanting Trees may eventually return this state to near Reference Plant Community-Cottonwood/Cool Season Bunchgrass. Remnants of Introduced species will still be present and returning to Reference may not be economically feasible.
Restoration pathway R3B
State 3 to 2• Long Term Prescribed Grazing, Noxious Weed Control, Return of Flood Water will return this site to a plant community similar to Mature Cottonwood / Rhizomatous Wheatgrass.
Additional community tables
Interpretations
Supporting information
Inventory data references
Information presented here has been derived from NRCS clipping data and other inventory data. Field observations from range trained personnel were also used. Other sources used as references include: USDA NRCS Water and Climate Center, USDA NRCS National Range and Pasture Handbook, and USDA NRCS Soil Surveys from various counties.
Other references
Belnap, J. and S. L. Phillips. 2001. Soil biota in an ungrazed grassland: Response to annual grass (Bromus tectorum) invasion. Ecological Applications: 11: 1261-1275.
Caudle, D., H. Sanchez, J. DiBenedetto, C. Talbot, and M. Karl. 2013. Draft Interagency Ecological Site Handbook for Rangelands. US Dept. of Agriculture. Washington D.C
Cleland, D.T.; Freeouf, J.A.; Keys, J.E., Jr.; Nowacki, G.J.; Carpenter, C; McNab, W.H. 2007. Ecological Subregions: Sections and Subsections of the Conterminous United States.[1:3,500,000], Sloan, A.M., cartog. Gen. Tech. Report WO-76. Washington, DC: U.S. Department of Agriculture, Forest Service.
Musgrave, G.W. 1955. How much of the rain enters the soil? In Water: U.S. Department of Agriculture Yearbook. Washington, D.C. P. 151-159.
National Engineering Handbook. US Department of Agriculture, Natural Resources Conservation Service. Available: http://www.info.usda.gov/CED/Default.cfm#National%20Engineering%20Handbook. Accessed February 25, 2008.
Passey, H. B., W. K. Hugie, E. W. Williams, and D. E. Ball. 1982. Relationships between soil, plant community, and climate on rangelands of the Intermountain west. USDA, Soil Conservation Service, Tech. Bull. No. 1669.
Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov/. Accessed [8/10/2015].
United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.
Western Regional Climate Center. Retrieved from http://www.wrcc.dri.edu/summary/Climsmco.html on May 17, 2018.Contributors
Colorado NRCS State Office
Approval
Kirt Walstad, 9/07/2023
Acknowledgments
This site was derived from historic Range Site in the State of Colorado.
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
Author(s)/participant(s) Contact for lead author Date 06/04/2026 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Sub-dominant:
Other:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
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Perennial plant reproductive capability:
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