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Draft. A draft ecological site description is either incomplete or has not undergone quality control and quality assurance review.
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous Not specified
Physiographic features
This site is commonly on nearly level flood plains, nearly level terraces, gently sloping uplands, and alluvial fans. In Colorado, it is usually on slopes less than 20 percent. The site occurs on all exposures. Elevation ranges from 4500-7500 feet.
Table 2. Representative physiographic features
Landforms (1) Alluvial fan
(2) Terrace
Elevation 4500 – 7500 ft Slope 0 – 20 % Aspect Aspect is not a significant factor Climatic features
The climate is semi-arid. Winters are cold and snowy, summers are warm and dry. The average annual precipitation ranges from 7.9 – 15 inches. Peak period of precipitation generally occurs in the spring and early summer. The site is also enhanced by receiving run-in water during periods of high runoff.
Plants begin to grow from April 15 to May 15. Short grasses (less than 18” tall) dominate the site. The cool-season grasses generally start growth from April 15 to May 1. The warm-season grasses usually start growing from May 1 to May 15. Generally forbs start their growth about April 25 to May 10 while the shrub species start growing from May 5 to May 15. The optimum growth period is generally between April 15 and July 1 for most of these plants. Frost-free period ranges from 100 to 135 days.
Table 3 Representative climatic features
Frost-free period (average) 140 days Freeze-free period (average) 0 days Precipitation total (average) 20 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
The soils in this site are deep and well drained, with a light brownish-gray to gray (air-dry) surface layer. Underlying layers are heavy sandy clay loams to clays and in places contain some gravel.
These soils are on flood plains, low terraces, nearly level to sloping uplands, and alluvial fans. They formed in thick medium to moderately fine textured sediments derived from sedimentary rocks or pedisediments of mixed origin, alkaline marine shales, clay shales and deltaic sediments derived from mixed parent materials. Salinity and alkalinity range from slight to strong. Soil reaction varies between a 7.4 and 9.0 pH. The intake rate is slow to rapid, and water movement through the soil is moderate to slow. Roots penetrate the soils readily. These soils have a low to high water holding capacity, ranging from 8 to10 inches in a 5 feet profile. Gravel fragments are variable throughout most of the soil profiles that are listed below but average less than 15 percent, by volume.
Under proper management, these soils have little surface runoff and slight or no erosion. However, if the vegetation is depleted, accelerated runoff and erosion can be expected.
Soils associated with this site are:
Arvada Loam 0-20%
Billings silty clay loam 0-20%
Billings silty clay loam gullied0-6%
Limon silty clay loam 0-12%
Uffens loam 0-12%
Table 4. Representative soil features
Surface texture (1) Fine sandy loam
(2) Loam
(3) Silty clay loam
Drainage class Moderately well drained to well drained Permeability class Moderately slow to very slow Soil depth 60 – 0 in Available water capacity
(0-40in)5.8 – 0 in Calcium carbonate equivalent
(0-40in)1 – 25 % Sodium adsorption ratio
(0-40in)25 – 0 Ecological dynamics
The plant community is about 55 to 65 percent grasses, 10 to 15 percent forbs, and 35 to 45 percent shrubs, air-dry weight. Alkali sacaton dominates the plant species, making up from 20 to 25 percent of the total annual production on the site. Inland saltgrass, western wheatgrass, basin wildrye are subdominate. Sandberg bluegrass, basin wildrye, fourwing saltbush, greenmolly summercypress, mat saltbush, and shadscale are important indigenous components. Many other grasses, numerous forbs, and shrubs enhance the wildlife habitat, and add color to the site, and variety to the diet of grazing animals.
If ecological retrogression is cattle induced, desirable grasses will decrease. However, if retrogression is caused by sheep, desirable grasses, forbs, and shrubs may be reduced. Deterioration of the site will decrease alkali scaton, inland saltgrass, fourwing saltbush, and Nuttall saltbush.
Retrogradation of the site will increase inland saltgrass, silky milkvetch, greenmolly summerchpress, two grooved milkvetch, basin big sagebrush, and black greasewood.
Plant species likely to invade this site and become part of the plant community when the range is in a degenerated condition are, Russian thistle, greenmolly summercypress, halogeton, mustard, Canada thistle, and other plants ecologically undesirable to the site.
If the range is in excellent condition, the approximate total annual production (air-dry) ranges are:
Favorable years 1100 lb/ac
Normal years 770 lb/ac
Unfavorable years 550 lb/ac
Of this production, 15 to 25 percent will likely be unpalatable or our of reach of grazing animals.
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 textEcosystem states
State 1 submodel, plant communities
State 1
Historic Climax Plant Community (HCPC)Community 1.1
Historic Climax Plant Community (HCPC)Vegetation density is approximately 5 to 10 percent.
Figure 3. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
Plant type Low
(lb/acre)Representative value
(lb/acre)High
(lb/acre)Grass/Grasslike 285 365 530 Shrub/Vine 230 325 450 Forb 35 75 120 Total 550 765 1100 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Grasses 310–500 alkali sacaton SPAI Sporobolus airoides 155–195 – saltgrass DISP Distichlis spicata 115–155 – basin wildrye LECI4 Leymus cinereus 75–115 – western wheatgrass PASM Pascopyrum smithii 40–75 – Sandberg bluegrass POSE Poa secunda 40–75 – squirreltail ELEL5 Elymus elymoides 0–75 – foxtail barley HOJU Hordeum jubatum 0–40 – toad rush JUBU Juncus bufonius 0–40 – sand dropseed SPCR Sporobolus cryptandrus 0–40 – Grass-like, perennial 2GLP Grass-like, perennial 0–40 – James' galleta PLJA Pleuraphis jamesii 0–40 – marsh muhly MURA Muhlenbergia racemosa 0–40 – Forb2 Forbs 40–115 twogrooved milkvetch ASBI2 Astragalus bisulcatus 0–115 – sulphur-flower buckwheat ERUM Eriogonum umbellatum 0–115 – tufted evening primrose OECA10 Oenothera caespitosa 0–115 – scarlet globemallow SPCO Sphaeralcea coccinea 0–115 – Shrub/Vine3 Shrubs 230–425 basin big sagebrush ARTRT Artemisia tridentata ssp. tridentata 75–115 – fourwing saltbush ATCA2 Atriplex canescens 75–115 – shadscale saltbush ATCO Atriplex confertifolia 40–75 – greasewood SAVE4 Sarcobatus vermiculatus 40–75 – winterfat KRLA2 Krascheninnikovia lanata 0–40 – mat saltbush ATCO4 Atriplex corrugata 0–40 – Nuttall's saltbush ATNU2 Atriplex nuttallii 0–40 – green molly BAAM4 Bassia americana 0–40 – rubber rabbitbrush ERNA10 Ericameria nauseosa 0–15 – smooth woodyaster XYGL Xylorhiza glabriuscula 0–15 – broom snakeweed GUSA2 Gutierrezia sarothrae 0–10 – Interpretations
Animal community
INTERPRETATIONS FOR GRAZING:
This site provides fair to good early summer and fall forage for cattle, horses, and small mammals. The animal forage preference generally changes as the spring season progresses into summer, fall, and winter. The dominant grass species, alkali sacaton and sand dropseed, are most desirable in the early summer and fall, while western wheatgrass and Sandberg bluegrass are most desirable in the spring. In addition, fourwing saltbush and winterfat are excellent forage throughout most of the year, especially during the winter season.
The vegetative palatability of each species will influence proper use considerations. Type of grazing animal, season, past grazing use, and associated plant species will directly influence the variation in animal preference for forages under various climatic conditions.
INTERPRETATIONS FOR WILDLIFE:
This site has a high potential for wildlife habitat because of the great variety and abundance of grasses, forbs, and shrubs produced. The site provides habitat, at least for part of the year for cottontail rabbit, waterfowl, antelope, deer, upland gamebirds, nongamebirds, small mammals, and reptiles.
Hydrological functions
Soils in this site are grouped into “C” hydrologic group, except Arvada loam which is “D”, as outlined in the “Soils of Colorado Loss Factors and Erodibility Hydrologic Groupings 1979”, handbook. Field investigations are needed to determine hydrological cover conditions and hydrologic curve numbers. The Hydrologic curve number for group C soil is about 74 and group D is about 80, when hydrologic conditions are good, as shown in “Peak Flows in Colorado” handbook.
Refer to SCS National Engineering Handbook, Section 4, to determine runoff quantities from the curves.
Recreational uses
This site has many forbs and shrubs that bloom from early spring to midsummer, which are aesthetically pleasing. Hunting for upland gamebirds and cottontail rabbit is generally good to excellent on this site.
Wood products
None.
Other information
THREATENED AND ENDANGERED PLANTS AND ANIMALS:
None are identified at this time.
MAJOR POISONOUS PLANTS TO LIVESTOCK:
Twogrooved milkvetch is poisonous year long especially in the spring. All livestock are affected.
Effects and symptoms:
Poisoning is “accumulative.” Signs of poisoning are rough coat, abnormal growth of long mane and tail hair, lack of coordination of muscles, constipation, and a peculiar gait.
Greasewood is poisonous in the spring. Cattle and sheep are affected.
Effects and symptoms:
Poisoning is “acute”. Early signs of poisoning (4-6 hours after animals eat toxic amounts) are dullness, loss of appetite, lowering of the head, reluctance to follow the band and irregular gait. Advanced signs are drooling, nasal discharge, progressive weakening, rapid shallow breathing, and coma. Cattle may die after eating 3 to 3.5 pounds in a short time.
Sheep may die after consuming 2 pounds of green leaves and fine stems in a short period of time without other forage.
Halogeton is poisonous when growing rapidly in spring (April-June). Sheep are affected.
Effects and symptoms:
Poisoning is “acute”. Signs of poisoning occur in 2 to 6 hours after an animal eats a fatal amount and death occurs in 9 to 11 hours. Early signs are dullness, loss of appetite, lowering of the head, and reluctance to follow the band. Advanced signs are drooling with white or reddish froth about the mouth, Progressive weakening, animals unable to stand, rapid and shallow breathing, and coma followed by violent struggle for air.
Sheep can tolerate small amounts when eaten with other forage. About .75 pounds will kill sheep that have been without feed for a day. It takes 1.1 pounds to kill sheep that have been feeding on other forage.
“Accumulative” - Poisoning effect increases in severity by successive additions of the poisonous plant. Symptoms appear weeks or months after poisonous plants are first eaten.
“Acute” – Symptoms appear within a few hours after poisonous plant has been eaten.
Supporting information
Type locality
Location 1: Delta County, CO General legal description Along highway 50, 4.5 miles west and ½ mile north of Delta, Delta County. Location 2: Moffat County, CO General legal description Flats near Craig, Moffat County. Other references
This site occurs in the following Field Offices:
Cortez
Craig
Delta
Durango
Eagle
Glenwood Springs
Grand Junction
Meeker
Montrose
Norwood
Steamboat SpringsRangeland 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 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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