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Ecological site R067BY063CO

Gravel Breaks

Last updated: 9/08/2023
Accessed: 11/23/2024

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General information

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.

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Figure 1. Mapped extent

Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.

MLRA notes

Major Land Resource Area (MLRA): 067B–Central High Plains, Southern Part

MLRA 67B occurs in eastern Colorado and consists of rolling plains and river valleys. Some canyonlands occur in the southeast portion. The major rivers are the South Platte and Arkansas which flow from the Rocky Mountains to Nebraska and Kansas. Other rivers in the MLRA include the Cache la Poudre and Republican and associated tributaries. This MLRA is traversed by Interstate 25, 70 and 76; and U.S. Highways 50 and 287. Major land uses include 54 percent rangeland, 35 percent cropland, and 2 percent pasture and hayland. Urban, developed open space, and miscellaneous land occupy approximately 9 percent. Major Cities in this area include Fort Collins, Greeley, Sterling, and Denver. Other cities include Limon, Cheyenne Wells, and Springfield. Land ownership is mostly private. Federal lands include Pawnee and Comanche National Grasslands (U.S. Forest Service), Sand Creek Massacre National Historic Site (National Park Service), and Rocky Mountain Arsenal National Wildlife Refuge (U.S. Fish & Wildlife Service). State Parks include Cherry Creek and Chatfield Reservoirs, and Barr and Jackson Lakes.

This region is periodically affected by severe drought, including the historic “Dust Bowl” of the 1930s. Dust storms may form during drought years in windy periods. Elevations range from 3,400 to 6,000 feet. The Average annual precipitation ranges from 14 to17 inches per year and ranges from 13 inches to over 18 inches, depending upon location. Precipitation occurs mostly during the growing season, often during rapidly developing thunderstorms. Mean annual air temperature (MAAT) is 48 to 52 degrees Fahrenheit. Summer temperatures may exceed 100 degrees Fahrenheit. Winter temperatures may be sub-zero, and snowfall varies from 20 to 40 inches per year. Snow cover frequently melts between snow events.

LRU notes

Land Resource Unit (LRU) A is the northeast portion of MLRA 67B, to an extent of approximately 9 million acres. Most of the LRU is rangeland, and includes the Pawnee National Grassland. Dryland winter wheat/fallow rotations (that may include dryland corn, sunflowers, and sorghum) are grown in most counties. Irrigated cropland is utilized in the South Platte Valley. Small acreage and urban ownership are more concentrated on the Front Range. This LRU is found in portions of Adams, Arapahoe, Elbert, Kit Carson, Larimer, Lincoln, Logan, Washington, and Weld counties. Other counties include Boulder, Cheyenne, Denver, Jefferson, and Yuma. The soil moisture regime is aridic ustic. The mean annual air temperature (MAAT) is 50 degrees Fahrenheit.

LRU B is in the southeast portion of MLRA 67B (2.6 million acres) and includes portions of Baca, Bent, Cheyenne, Kiowa, Las Animas, and Prowers counties. Most of the LRU remains in rangeland and includes the Comanche National Grassland. On the farmed land, a system of dryland winter wheat/fallow rotations (that may include dryland corn, sunflowers, and sorghum) is implemented. Irrigated cropland is found in the Arkansas Valley. The soil moisture regime is aridic ustic and the MAAT is 52 degrees Fahrenheit.

LRU C occurs in portions of Morgan and Weld counties (approximately 1.2 million acres). Most of LRU C is in rangeland. On the farmed land, a system of dryland winter wheat/fallow rotations (that may include dryland corn, sunflowers, and sorghum) is implemented. The soil moisture regime is ustic aridic and the MAAT is 48 degrees Fahrenheit.

Classification relationships

MLRA 67B is in the Colorado Piedmont and Raton Sections of the Great Plains Province (USDA, 2006). The MLRA is further defined by Land Resource Units (LRUs) A, B, and C. Features such as climate, geology, landforms, and key vegetation further refine these concepts and are described in other sections of the Ecological Site Description (ESD). NOTE: To date, these LRUs are DRAFT.

Relationship to Other Hierarchical Classifications:
NRCS Classification Hierarchy: Physiographic Division, Physiographic Province, Physiographic Section, Land Resource Region, Major Land Resource Area, Land Resource Unit (Fenneman, 1946).
USFS Classification Hierarchy: Domain, Division, Province, Section, Subsection,
Land Type Association: Land Type, Land Type Phase (Cleland et al, 1997).

REVISION NOTES:
The Gravel Breaks Ecological Site was developed by an earlier version (2004, revised 2007). This earlier version was based on input from Natural Resources Conservation Service (formerly Soil Conservation Service) and historical information obtained from the Gravel Breaks Range Site descriptions (1975). This ESD meets the Provisional requirements of the National Ecological Site Handbook (NESH). This ESD will continue refinement towards an Approved status according to the NESH.

Ecological site concept

This site is a run-off site with soils deeper than 40 inches to bedrock. It has greater than 15 percent rock fragments on the soil surface or in the subsoil.

Associated sites

R067BY002CO	Loamy Plains This ecological site is commonly adjacent.
R067BY009CO	Siltstone Plains This ecological site is commonly adjacent.
R067BY024CO	Sandy Plains This ecological site is commonly adjacent.
R067BY045CO	Shaly Plains This ecological site is commonly adjacent.
R067BY056CO	Sandstone Breaks This ecological site is commonly adjacent.

Similar sites

R067BY056CO	Sandstone Breaks The Sandstone Breaks Ecological Site lies over sandstone bedrock at a depth less than 40 inches from the soil surface.
R067BY060CO	Limestone Breaks The Limestone Breaks Ecological Site lies over limestone bedrock at a depth less than 40 inches from the soil surface.

R067BY056CO

Sandstone Breaks

The Sandstone Breaks Ecological Site lies over sandstone bedrock at a depth less than 40 inches from the soil surface.

R067BY060CO

Limestone Breaks

The Limestone Breaks Ecological Site lies over limestone bedrock at a depth less than 40 inches from the soil surface.

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Rhus trilobata (2) Krascheninnikovia lanata
Herbaceous	(1) Schizachyrium scoparium (2) Bouteloua curtipendula

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Physiographic features

This site occurs on summits or shoulders of the hills or knobs and on crests or nose slopes of the scarps or escarpments on dissected plains or canyonlands.

Figure 2. The distribution of the Gravel Breaks site in MLRA 67B.

Table 2. Representative physiographic features

Landforms	(1) Hill (2) Knob (3) Scarp
Runoff class	Very low to medium
Flooding frequency	None
Ponding frequency	None
Elevation	1,036 – 1,829 m
Slope	1 – 30%
Ponding depth	0 cm
Water table depth	203 cm
Aspect	Aspect is not a significant factor

Climatic features

Average annual precipitation across the MLRA extent is 14 to 17 inches, and ranges from 13 to over 18 inches, depending on location. Precipitation increases from north to south. Mean Annual Air Temperature (MAAT) is 50 degrees Fahrenheit in the northern part and increases to 52 degrees Fahrenheit in the southern part. Portions of Morgan and Weld counties are cooler and drier, the MAAT is 48 degrees Fahrenheit, and average precipitation is 13 to14 inches per year.

Two-thirds of the annual precipitation occurs during the growing season from mid-April to late September. Snowfall averages 30 inches per year, area-wide, but varies by location from 20 to 40 inches per year. Winds are estimated to average 9 miles per hour annually. Daytime winds are generally stronger than at night, and occasional strong storms may bring periods of high winds with gusts to more than 90 mph. High-intensity afternoon thunderstorms may arise. The average length of the freeze-free period (28 degrees Fahrenheit) is 155 days from April 30th to October to 3rd. The average frost-free period (32 degrees Fahrenheit) is 136 days from May 11th to September 24th. July is the hottest month, and December and January are the coldest months. Summer temperatures average 90 degrees Fahrenheit and occasionally exceed 100 degrees Fahrenheit. Summer humidity is low and evaporation is high. Winters are characterized with frequent northerly winds, producing severe cold with temperatures occasionally dropping to -30 degrees Fahrenheit or lower. Blizzard conditions may form quickly. For detailed information, visit the Western Regional Climate Center website:
Western Regional Climate Center Historical Data Western U.S. Climate summaries, NOAA Coop Stations Colorado http://www.wrcc.dri.edu/summary/Climsmco.html.

Table 3. Representative climatic features

Frost-free period (characteristic range)	119-129 days
Freeze-free period (characteristic range)	134-151 days
Precipitation total (characteristic range)	356-432 mm
Frost-free period (actual range)	102-132 days
Freeze-free period (actual range)	126-156 days
Precipitation total (actual range)	356-432 mm
Frost-free period (average)	121 days
Freeze-free period (average)	142 days
Precipitation total (average)	381 mm

Characteristic range

Actual range

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Figure 3. Monthly precipitation range

Characteristic range

Actual range

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Figure 4. Monthly minimum temperature range

Characteristic range

Actual range

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Figure 5. Monthly maximum temperature range

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Figure 6. Monthly average minimum and maximum temperature

Figure 7. Annual precipitation pattern

Figure 8. Annual average temperature pattern

Climate stations used

(1) LIMON WSMO [USW00093010], Limon, CO
(2) BRIGHTON 3 SE [USC00050950], Brighton, CO
(3) BYERS 5 ENE [USC00051179], Byers, CO
(4) CHEYENNE WELLS [USC00051564], Cheyenne Wells, CO
(5) SPRINGFIELD 7 WSW [USC00057866], Springfield, CO
(6) FLAGLER 1S [USC00052932], Flagler, CO
(7) FT MORGAN [USC00053038], Fort Morgan, CO
(8) KIT CARSON [USC00054603], Kit Carson, CO
(9) BRIGGSDALE [USC00050945], Briggsdale, CO
(10) GREELEY UNC [USC00053553], Greeley, CO
(11) NUNN [USC00056023], Nunn, CO

Soil features

The soils on this site are very deep, well to excessively drained soils that formed from old, gravelly alluvium or from old outwash. They typically have a moderate to rapid permeability class, but ranges to very rapid in some soils. The available water capacity is very low to low. The soil moisture regime is typically aridic ustic. The soil temperature regime is mesic.

The surface layer of the soils in this site are typically gravelly loamy sand, gravelly sandy loam, or gravelly loam, but may include very gravelly texture modifiers. The surface layer ranges from a depth of 2 to 10 inches thick. The subsoil is typically gravelly coarse sand, very gravelly coarse sand, gravelly sand, or very gravelly sand, but may include gravelly loamy sand, very gravelly loamy sand, or extremely gravelly texture modifiers. Soils in this site vary to the depth of carbonates, some soils are calcareous at the surface or leached from 3 to 30 inches; other soils are leached of carbonates throughout the entire profile. Exposed areas of gravel are inherent to this site. The amount of bare ground varies with the amount of surface gravel. Areas with little or no surface gravels are susceptible to erosion by water and wind. The potential for water erosion accelerates with increasing slope.

Major soil series correlated to this ecological site include: Cascajo, Dix, Eckley, Karval, Orsa, Peetz, Schamber, and Yoder.

Other soil series that have been correlated to this site, but may eventually be re-correlated include: Chicosa, Gravelly Land, Humbarsprings, and Potter.

Note: Revisions to soil surveys are on-going. For the most recent updates, visit the Web Soil Survey, the official site for soils information: http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx.

The attributes listed below represent 0 to 40 inches in depth or to the first restrictive layer.

Table 4. Representative soil features

Parent material	(1) Alluvium (2) Outwash
Surface texture	(1) Gravelly loamy sand (2) Gravelly sandy loam (3) Gravelly loam
Drainage class	Well drained to excessively drained
Permeability class	Moderate to very rapid
Soil depth	203 cm
Surface fragment cover <=3"	0 – 35%
Surface fragment cover >3"	0 – 15%
Available water capacity (0-101.6cm)	2.03 – 10.16 cm
Calcium carbonate equivalent (0-101.6cm)	0 – 40%
Electrical conductivity (0-101.6cm)	0 – 2 mmhos/cm
Sodium adsorption ratio (0-101.6cm)	0
Soil reaction (1:1 water) (0-101.6cm)	6.6 – 8.4
Subsurface fragment volume <=3" (Depth not specified)	15 – 80%
Subsurface fragment volume >3" (Depth not specified)	0 – 30%

Ecological dynamics

The Gravel Breaks ecological site is characterized by three states: Reference, Warm-Season Shortgrass, and Increased Bare Ground. The Reference State is characterized by warm-season mid and tallgrasses with a variety of forbs and shrubs. The Warm-Season Shortgrass State is characterized by a warm-season short bunchgrass (blue grama) and grass-like (threadleaf sedge). The Increased Bare Ground State is characterized by annual grasses and forbs, cushion plants, and soapweed yucca.

Continuous, heavy grazing that does not allow for adequate recovery periods causes this site to deteriorate. Grasses such as little bluestem, sideoats grama, prairie sandreed, switchgrass, and big bluestem decrease in both frequency and production. Grasses and grass-likes such as blue grama and threadleaf sedge increase. If proper recovery periods between grazing events are not allowed during the growing season, blue grama eventually develops into a patchy sod-bound condition. Mid and tallgrasses are removed from the plant community. Cushion plants such as spiny milkvetch (mat loco) and creeping nailwort (sessile nailwort) in addition to Fendler threeawn, prairie sagewort (fringed sagebrush), soapweed yucca (small soapweed), and cheatgrass increase or invade the site. In time, continuous use in combination with heavy stocking results in large amounts of bare ground. Tillage is not recommended on this site due to steep slopes, gravelly soils, and associated low production potential.

The degree of grazing has a significant impact on the ecological dynamics of the site. This region was historically occupied by large grazing animals, such as bison, elk, pronghorn, and mule deer. Grazing by these large herbivores, along with climatic and seasonal weather fluctuations, had a major influence on the ecological dynamics of the site. Deer and pronghorn are widely distributed throughout the MLRA. Secondary influences of herbivory by species such as prairie dogs and other small rodents, insects, and root-feeding organisms continues to impact the vegetation.

Historically, grazing patterns by herds of large ungulates were driven by water distribution, precipitation events, drought events, and fire. It is believed that grazing periods would have been shorter, followed by longer recovery periods. These large migrating herds impacted the ecological processes of nutrient and hydrologic cycles, by urination, trampling (incorporation of litter into the soil surface), and breaking of surface crust, (which increases water infiltration).

Today, livestock grazing, especially beef cattle has been a major influence on the ecological dynamics of the site. Grazing management, coupled with the effects of annual climatic variations, largely dictates the plant communities for the site.

Recurrent drought has historically impacted the vegetation of this region. Changes in species composition vary depending upon the duration and severity of the drought cycle and prior grazing management. Drought events since 2002 have significantly increased mortality of blue grama and buffalograss in some locales.

This site developed with occasional fire as part of the ecological processes. Historic fire frequency (pre-industrial) is estimated at 10 to14 years (Guyette, 2012), randomly distributed, and started by lightning at various times throughout the growing season. Early human inhabitants also were likely to start fires for various reasons (deliberate or accidental). It is believed that fires were set as a management tool for attracting herds of large migratory herbivores (Stewart, 2002). The impact of fire over the past 100 years has been relatively insignificant due to the human control of wildfires and the lack of acceptance of prescribed fire as a management tool.

Mechanical treatment consisting of contour pitting, furrowing, terracing, chiseling, and disking has been practiced in the past. It was theorized that the use of this high-input technology would improve production and plant composition on rangeland. These high-cost practices have shown to have no significant long-term benefits on production or plant composition and have only resulted in a permanently rough ground surface. Prescribed grazing that mimics the historic grazing of herds of migratory herbivores, as described earlier, has been shown to result in desired improvements based on management goals for this ecological site.

Eastern Colorado was strongly affected by extended drought conditions in the “Dust Bowl” period of the 1930’s, with recurrent drought cycles in the 1950s and 1970s. Extreme to exceptional drought conditions have re-visited the area from 2002 to 2012, with brief interludes of near normal to normal precipitation years. Long-term effects of these latest drought events have yet to be determined. Growth of native cool-season plants begins about April 1 and continues to mid-June. Native warm-season plants begin growth about May 1 and continue to about August 15. Regrowth of cool-season plants occurs in September in most years, depending on the availability of moisture.

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 text

Ecosystem states

1. Reference State

2. Warm-season Shortgrass State

3. Increased Bare Ground State

T1A	-	Excessive grazing. Lack of fire.
T2A	-	Excessive grazing. Lack of fire.

State 1 submodel, plant communities

1.1. Bouteloua curtipendula-Schizachyrium scoparium (sideoats grama-little bluestem).

1.2. Bouteloua gracilis-Schizachyrium scoparium (blue grama-little bluestem).

1.1A	-	Excessive grazing. Lack of fire.
1.2A	-	Prescribed grazing. Prescribed fire.

State 2 submodel, plant communities

2.1. Bouteloua gracilis-Carex filifolia (blue grama-threadleaf sedge).

State 3 submodel, plant communities

3.1. Salsola-Bassia scoparia/Aristida purpurea-Bromus tectorum (Russian thistle-burningbush/Fendler threeawn-cheatgrass).

State 1
Reference State

The Reference State is characterized by two distinct plant community phases. The plant communities and various successional stages between them represent the natural range of variability within the Reference State.

Dominant plant species

skunkbush sumac (Rhus trilobata), shrub
winterfat (Krascheninnikovia lanata), shrub
sideoats grama (Bouteloua curtipendula), grass
little bluestem (Schizachyrium scoparium), grass

Community 1.1
Bouteloua curtipendula-Schizachyrium scoparium (sideoats grama-little bluestem).

This plant community is the interpretive plant community for this site. This community evolved with grazing by large herbivores and is suited to grazing by domestic livestock. Historically, fires likely occurred infrequently. This plant community can be found on areas that are grazed and where the grazed plants receive adequate recovery periods during the growing season. The potential vegetation is about 75 to 85 percent grasses and grass-likes, 10 to15 percent forbs and 5 to10 percent woody plants. The principal mid-grasses are little bluestem and sideoats grama. Secondary grasses include blue grama, big bluestem, prairie sandreed, switchgrass, needle and thread, hairy grama, and western wheatgrass. Threadleaf and sun sedge are common. Dominant forbs are purple prairie clover, dotted blazing star (dotted gayfeather), and upright prairie coneflower. Winterfat, skunkbush sumac, and golden currant are some of the major shrubs found on this plant community. This is a sustainable plant community in terms of soil stability, watershed function, and biological integrity. Litter is properly distributed where vegetative cover is continuous. Some litter movement may occur on steeper slopes. Decadence and natural plant mortality are very low. Community dynamics, nutrient cycle, water cycle, and energy flow are functioning properly. This community is resistant to many disturbances except heavy, continuous grazing, tillage, and development into urban or other uses. Areas having lost all vegetation, such as livestock and vehicle trails, are subject to high erosion rates and extreme runoff. Total annual production, during an average year, ranges from 500 to 1,400 pounds of air-dry weight with a Representative Value of average 950 pounds.

Dominant plant species

skunkbush sumac (Rhus trilobata), shrub
winterfat (Krascheninnikovia lanata), shrub
sideoats grama (Bouteloua curtipendula), grass
little bluestem (Schizachyrium scoparium), grass

Figure 9. Annual production by plant type (representative values) or group (midpoint values)

Table 5. Annual production by plant type

Plant type	Low (kg/hectare)	Representative value (kg/hectare)	High (kg/hectare)
Grass/Grasslike	409	852	1295
Forb	101	135	163
Shrub/Vine	50	78	112
Total	560	1065	1570

Figure 10. Plant community growth curve (percent production by month). CO6709, Warm-season dominant, cool-season subdominant; MLRA-67B; upland coarse textured soils..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
0	0	2	7	25	35	15	10	5	1	0	0

Community 1.2
Bouteloua gracilis-Schizachyrium scoparium (blue grama-little bluestem).

Blue grama has increased. Little bluestem and sideoats grama have been reduced in the community. Big bluestem, switchgrass, prairie sandreed, needle and thread, western wheatgrass, purple prairie clover, and winterfat have been significantly reduced. Hairy grama, sand dropseed, Fendler threeawn, spiny phlox (Hood’s phlox), hairy false goldenweed (hairy goldaster), Cuman ragweed (western ragweed), and slimflower scurfpea have increased. Woody plants include soapweed yucca, and skunkbush sumac. Plant frequency and vigor have decreased. Reduction of tall and mid-grasses, nitrogen fixing forbs, the shrub component, and increased warm-season shortgrass has begun to alter the biotic integrity of this community. Water and nutrient cycles are at risk of becoming impaired. Litter levels have been reduced. Flow paths and rills are more apparent. Pedestalled plants can be observed. Total annual production, during a normal year, ranges from 300 to 800 pounds of air-dry weight and averages 500 pounds.

Dominant plant species

skunkbush sumac (Rhus trilobata), shrub
soapweed yucca (Yucca glauca), shrub
blue grama (Bouteloua gracilis), grass
little bluestem (Schizachyrium scoparium), grass

Figure 11. Plant community growth curve (percent production by month). CO6709, Warm-season dominant, cool-season subdominant; MLRA-67B; upland coarse textured soils..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
0	0	2	7	25	35	15	10	5	1	0	0

Pathway 1.1A
Community 1.1 to 1.2

Heavy, continuous grazing without adequate recovery periods between grazing events and lack of fire shift this plant community to the 1.2 Community. Drought accelerates this process. Recurring spring seasonal grazing decreases cool-season plants. Recurring summer grazing decreases warm-season plants.

Pathway 1.2A
Community 1.2 to 1.1

Grazing that allows for adequate recovery periods between grazing events, proper stocking rates, and prescribed fire shift the 1.2 Community back to the Reference Plant Community.

Conservation practices

Prescribed Burning
Prescribed Grazing

State 2
Warm-season Shortgrass State

Species diversity and production have been severely reduced. Litter levels are very low. Mineral and water cycles are impaired due to the loss of deeper rooted grasses, forbs, and shrubs, and significant biotic and edaphic (soil characteristics) changes. Rills are evident and soil loss is obvious, especially on steeper slopes. Pedestalled plants with exposed roots are common. An ecological threshold has been crossed. The loss of functional/structural groups such as warm-season midgrass reduces the biodiversity and productivity of this site.

Dominant plant species

prairie sagewort (Artemisia frigida), shrub
soapweed yucca (Yucca glauca), shrub
blue grama (Bouteloua gracilis), grass
threadleaf sedge (Carex filifolia), grass

Community 2.1
Bouteloua gracilis-Carex filifolia (blue grama-threadleaf sedge).

Blue grama and threadleaf sedge dominate the community. These species exhibit a mosaic sod-bound appearance. Tallgrasses have been removed. Little bluestem and sideoats grama may remain in remnant amounts on steeper slopes. Forbs and shrubs that have increased are Cuman ragweed (western ragweed), prairie sagewort (fringed sagebrush), hairy false goldenaster, spiny phlox (Hood’s phlox), and soapweed yucca. Cushion plants such as spiny milkvetch (mat loco) and creeping nailwort (sessile nailwort) have increased. Production ranges from 150 to 450 pounds of air-dry vegetation per acre per year and averages 300 pounds during a normal year.

Dominant plant species

prairie sagewort (Artemisia frigida), shrub
soapweed yucca (Yucca glauca), shrub
blue grama (Bouteloua gracilis), grass
threadleaf sedge (Carex filifolia), grass

Figure 12. Plant community growth curve (percent production by month). CO6712, Warm-season/cool-season codominant; MLRA-67B; upland coarse textured soils..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
0	0	0	1	7	48	27	15	2	0	0	0

State 3
Increased Bare Ground State

Soil erosion is severe. An ecological threshold has been crossed. Erosion and loss of organic matter and carbon reserves are concerns. Nutrient and water cycles and energy flow are impaired.

Dominant plant species

soapweed yucca (Yucca glauca), shrub
spiny phlox (Phlox hoodii), shrub
Fendler threeawn (Aristida purpurea var. longiseta), grass
cheatgrass (Bromus tectorum), grass
Russian thistle (Salsola), other herbaceous
burningbush (Bassia scoparia), other herbaceous

Community 3.1
Salsola-Bassia scoparia/Aristida purpurea-Bromus tectorum (Russian thistle-burningbush/Fendler threeawn-cheatgrass).

Bare ground, cushion plants, and cryptogamic crusts have significantly increased. Remnant amounts of blue and hairy grama may still be found. Other plants which may be present are Russian thistle, burningbush, Fendler threeawn, cheatgrass, cushion plants such as spiny milkvetch (mat loco), creeping nailwort (sessile nailwort), spiny phlox (Hood’s phlox), and soapweed yucca. Total annual production varies from 25 to 150 pounds of air-dry vegetation per acre per year.

Dominant plant species

soapweed yucca (Yucca glauca), shrub
spiny phlox (Phlox hoodii), shrub
Fendler threeawn (Aristida purpurea var. longiseta), grass
cheatgrass (Bromus tectorum), grass
Russian thistle (Salsola), other herbaceous
burningbush (Bassia scoparia), other herbaceous

Figure 13. Plant community growth curve (percent production by month). CO6710, Warm-season dominant; MLRA-67B; upland coarse-textured soils..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
0	0	0	5	20	40	20	10	5	0	0	0

Transition T1A
State 1 to 2

Heavy, continuous grazing without adequate recovery periods between grazing events and lack of fire shift this plant community across an ecological threshold to the Warm-season Shortgrass State. Biotic integrity and hydrologic function are impaired as a result of this transition.

Transition T2A
State 2 to 3

Long-term, heavy, continuous grazing without adequate recovery periods between grazing events and lack of fire cause a shift across an ecological threshold to the Increase Bare Ground State. Soil erosion, loss of organic matter and carbon reserves, and invasion by annual plants are constraints to recovery.

Additional community tables

Table 6. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production (kg/hectare)	Foliar cover (%)
Grass/Grasslike
1	Warm Season Mid-Bunch Grass			319–480
	sideoats grama	BOCU	Bouteloua curtipendula	160–267	–
	little bluestem	SCSC	Schizachyrium scoparium	160–267	–
	sand dropseed	SPCR	Sporobolus cryptandrus	11–21	–
2	Warm Season Short Grass			54–106
	blue grama	BOGR2	Bouteloua gracilis	54–106	–
	hairy grama	BOHI2	Bouteloua hirsuta	11–33	–
	buffalograss	BODA2	Bouteloua dactyloides	0–11	–
3	Warm Season Tall Rhizmatous Grass			11–75
	prairie sandreed	CALO	Calamovilfa longifolia	11–75	–
4	Warm Season Tall Bunch Grass			33–106
	big bluestem	ANGE	Andropogon gerardii	21–85	–
	switchgrass	PAVI2	Panicum virgatum	11–54	–
5	Cool Season Mid-Bunch Grass			33–75
	needle and thread	HECOC8	Hesperostipa comata ssp. comata	11–54	–
	Indian ricegrass	ACHY	Achnatherum hymenoides	11–21	–
	squirreltail	ELELE	Elymus elymoides ssp. elymoides	0–11	–
	prairie Junegrass	KOMA	Koeleria macrantha	0–11	–
6	Cool Season Mid-Rhizomatous Grass			11–33
	western wheatgrass	PASM	Pascopyrum smithii	11–33	–
7	Miscellaneous Grasses			0–21
	Fendler threeawn	ARPUL	Aristida purpurea var. longiseta	0–11	–
	plains muhly	MUCU3	Muhlenbergia cuspidata	0–11	–
	ring muhly	MUTO2	Muhlenbergia torreyi	0–11	–
	Fendler threeawn	ARPUL	Aristida purpurea var. longiseta	0–11	–
	plains muhly	MUCU3	Muhlenbergia cuspidata	0–11	–
	ring muhly	MUTO2	Muhlenbergia torreyi	0–11	–
8	Annual Grasses			0–11
	sixweeks fescue	VUOC	Vulpia octoflora	0–11	–
9	Sedges			21–106
	sun sedge	CAINH2	Carex inops ssp. heliophila	11–33	–
	threadleaf sedge	CAFI	Carex filifolia	11–21	–
10	Other Native Grasses			11–54
	purple prairie clover	DAPU5	Dalea purpurea	11–21	–
	purple locoweed	OXLA3	Oxytropis lambertii	0–11	–
	white locoweed	OXSE	Oxytropis sericea	0–11	–
	slimflower scurfpea	PSTE5	Psoralidium tenuiflorum	0–11	–
	twogrooved milkvetch	ASBI2	Astragalus bisulcatus	0–11	–
	spiny milkvetch	ASKE	Astragalus kentrophyta	0–11	–
	woolly locoweed	ASMO7	Astragalus mollissimus	0–11	–
Forb
11	Legumes			21–54
	purple prairie clover	DAPU5	Dalea purpurea	11–21	–
	purple locoweed	OXLA3	Oxytropis lambertii	0–11	–
	white locoweed	OXSE	Oxytropis sericea	0–11	–
	slimflower scurfpea	PSTE5	Psoralidium tenuiflorum	0–11	–
	twogrooved milkvetch	ASBI2	Astragalus bisulcatus	0–11	–
	spiny milkvetch	ASKE	Astragalus kentrophyta	0–11	–
	woolly locoweed	ASMO7	Astragalus mollissimus	0–11	–
12	Warm Season			54–106
	dotted blazing star	LIPU	Liatris punctata	11–21	–
	rush skeletonplant	LYJU	Lygodesmia juncea	0–11	–
	lacy tansyaster	MAPIP4	Machaeranthera pinnatifida ssp. pinnatifida var. pinnatifida	0–11	–
	upright prairie coneflower	RACO3	Ratibida columnifera	0–11	–
	threadleaf ragwort	SEFLF	Senecio flaccidus var. flaccidus	0–11	–
	white heath aster	SYER	Symphyotrichum ericoides	0–11	–
	Colorado greenthread	THAM4	Thelesperma ambiguum	0–11	–
	stiff greenthread	THFI	Thelesperma filifolium	0–11	–
	Cuman ragweed	AMPS	Ambrosia psilostachya	0–11	–
	tarragon	ARDR4	Artemisia dracunculus	0–11	–
	sulphur-flower buckwheat	ERUM	Eriogonum umbellatum	0–11	–
	shaggy dwarf morning-glory	EVNU	Evolvulus nuttallianus	0–11	–
	hairy false goldenaster	HEVI4	Heterotheca villosa	0–11	–
13	Cool Season			0–33
	alpine feverfew	PAAL6	Parthenium alpinum	0–11	–
	New Mexico groundsel	PANEM	Packera neomexicana var. mutabilis	0–11	–
	creeping nailwort	PASE	Paronychia sessiliflora	0–11	–
	beardtongue	PENST	Penstemon	0–11	–
	scarlet globemallow	SPCO	Sphaeralcea coccinea	0–11	–
14	Annuals			0–11
	woolly plantain	PLPA2	Plantago patagonica	0–11	–
15	Other Native Forbs			11–54
	skunkbush sumac	RHTR	Rhus trilobata	0–33	–
	golden currant	RIAU	Ribes aureum	0–21	–
	winterfat	KRLA2	Krascheninnikovia lanata	0–21	–
	chokecherry	PRVIV	Prunus virginiana var. virginiana	0–21	–
Shrub/Vine
16	Shrubs			21–85
	skunkbush sumac	RHTR	Rhus trilobata	0–33	–
	golden currant	RIAU	Ribes aureum	0–21	–
	winterfat	KRLA2	Krascheninnikovia lanata	0–21	–
	chokecherry	PRVIV	Prunus virginiana var. virginiana	0–21	–
17	Half-Shrubs			21–43
	prairie sagewort	ARFR4	Artemisia frigida	0–11	–
	spreading buckwheat	EREF	Eriogonum effusum	0–11	–
	rubber rabbitbrush	ERNAG	Ericameria nauseosa ssp. nauseosa var. glabrata	0–11	–
	spinystar	ESVIV	Escobaria vivipara var. vivipara	0–11	–
	broom snakeweed	GUSA2	Gutierrezia sarothrae	0–11	–
	plains pricklypear	OPPO	Opuntia polyacantha	0–11	–
	spiny phlox	PHHO	Phlox hoodii	0–11	–
18	Succulents			0–21
	spinystar	ESVIV	Escobaria vivipara var. vivipara	0–11	–
	plains pricklypear	OPPO	Opuntia polyacantha	0–11	–
19	Evergreen			0–11
	soapweed yucca	YUGL	Yucca glauca	0–11	–
20	Other Native Shrubs			11–54

Interpretations

Animal community

WILDLIFE INTERPRETATIONS:

The combination of grasses, forbs, and shrubs found on the ecological site provide habitat for numerous wildlife species. Historic large grazers that influenced these communities were bison, elk, mule deer, and pronghorn. Bison are no longer widely distributed in their historic range. Pronghorn are the most abundant ungulates using this ecological site, followed by mule deer. Domestic grazers share these habitats with wildlife. The grassland communities of eastern Colorado are home to many bird species. Changes in the composition of the plant community when moving from the Reference Community to other communities on this ecological site may result in species shifts in bird species. The occasional spring found on this site provides essential seasonal water needed for reproductive habitat by some reptiles and amphibians. Because of a lack of permanent water, fish are not common.

Reference Plant Community: Little Bluestem, Sideoats Grama

The grasses, forbs, and shrubs, in this plant community provide habitat for reptiles such as prairie rattlesnake, bullsnake, and racer. If water is available for breeding, spadefoot toads may be found here. The structural diversity in the plant community on this site provides habitat for Cassin’s and Brewer’s sparrow, lark bunting, and scaled quail. Ferruginous and Swainson’s hawks are commonly seen on this site. The combination of mid and tall grasses and shrubs provides habitat for lesser prairie chicken in the eastern part of this ecological site. Small mammals such as white-tailed jackrabbit, swift fox, and several species of mice are common in this plant community. Pronghorn is a typical ungulate found in this community. The soils are limiting to burrowing animals.

1.2 Community: Increased Blue Grama, Decreased Little Bluestem, Decreased Sideoats Grama

All wildlife species found in the Reference Plant Community are expected in this plant community. However, the loss of some of the vegetative structural diversity in this plant community makes it less attractive to the Reference Plant Community species.

1.3 Community: Blue Grama, Threadleaf Sedge and
Increased Bare Ground, Cryptogams, Annuals:

As these communities develop into an open landscape the wildlife species shift away from Reference Plant Community species and toward the species that prefer unvegetated areas and short plants. Texas short-lizard, six-lined racerunner, and black-tailed jackrabbit would be expected more frequently here than in the Reference Plant Community.

GRAZING INTERPRETATIONS:
The following table lists suggested initial stocking rates for an animal unit (1000-pound beef cow) under continuous grazing (yearlong grazing or growing-season-long grazing) based on normal growing conditions. However, continuous grazing is not recommended. These estimates should only be used as preliminary guidelines in the initial stages of the conservation planning process. Often, the existing plant composition does not entirely match any particular plant community described in this ecological site description. Therefore, field inventories are always recommended to document plant composition, total production, and palatable forage production. Carrying capacity estimates that reflect on-site conditions should be calculated using field inventories.

If the following production estimates are used, they should be adjusted based on animal kind or class and on the specific palatability of the forage plants in the various plant community descriptions. Under a properly stocked, properly applied, prescribed grazing management system that provides adequate recovery periods following each grazing event, improved harvest efficiencies eventually result in increased carrying capacity. See USDA-NRCS Colorado Prescribed Grazing Standard and Specification Guide (528).

The stocking rate calculations are based on the total annual forage production in a normal year multiplied by 25 percent harvest efficiency divided by 912.5 pounds of ingested air-dry vegetation for an animal unit per month (AUM).

Reference PC - (950) (0.26)

1.2 PC - (500) (0.14)

2.1 PC - (300) (0.08)

Grazing by domestic livestock is one of the major income-producing industries in the area. Rangelands in this area provide yearlong forage under prescribed grazing for cattle, sheep, horses and other herbivores.

An on-site inventory is required prior to development of a grazing plan.

Hydrological functions

Water is the principal factor limiting forage production on this site. This site is dominated by soils in hydrologic group A and B. Infiltration varies from moderate to high and runoff potential for this site varies from moderate to low depending on soil hydrologic group and ground cover. Areas where ground cover is less than 50 percent have the greatest potential to have reduced infiltration and higher runoff (refer to NRCS Section 4, National Engineering Handbook (USDA–NRCS, 1972–2012) for runoff quantities and hydrologic curves).

Recreational uses

This site provides hunting, hiking, photography, bird watching, and other opportunities. The wide varieties of plants that bloom from spring until fall have an aesthetic value that appeals to visitors.

Wood products

No appreciable wood products are present on the site.

Other products

This site is a source for gravel.

General Data (MLRA and Revision Notes, Hierarchical Classification, Ecological Site Concept, Physiographic, Climate, and Water Features, and Soils Data):

Updated. All “Required” items complete to Provisional level.

Community Phase Data (Ecological Dynamics, STM, Transition & Recovery Pathways, Reference Plant Community, Species Composition List, Annual Production Table):

Updated. All “Required” items complete to Provisional level.
NOTE: Annual Production Table is from the “Previously Approved” ESD 2004. The Species Composition List is also from the 2004 version, with minor edits. These will need review for future updates at Approved level.

Each Alternative State/Community:

Complete to Provisional level

Supporting Information (Site Interpretations, Assoc. & Similar Sites, Inventory Data References, Agency/State Correlation, References):

Updated. All “Required” items complete to Provisional level.

Livestock Interpretations updated to reflect Total Annual Production revisions in each plant community.

Wildlife interpretations, general narrative, and individual plant communities updated to the Provisional level. Hydrology, Recreational Uses, Wood Products, Other Products, Plant Preferences table, and Rangeland Health Reference Sheet carried over from previously “Approved” ESD 2004.

Reference Sheet

The Reference Sheet was previously approved in 2007.
It will be updated at the next “Approved” level.

“Future work, as described in a project plan, to validate the information in this provisional ecological site description is needed. This will include field activities to collect low and medium intensity sampling, soil correlations, and analysis of that data. Annual field reviews should be done by soil scientists and vegetation specialists. A final field review, peer review, quality control, and quality assurance reviews of the ESD will be needed to produce the final document.” (NI 430_306 ESI and ESD, April, 2015).

Other information

Relationship to Other Hierarchical Classifications:

NRCS Classification Hierarchy:
Physiographic Divisions of the United States (Fenneman, 1946): Physiographic DivisionPhysiographic ProvincePhysiographic SectionLand Resource RegionMajor Land Resource Area (MLRA)Land Resource Unit (LRU).
USFS Classification Hierarchy:
National Hierarchical Framework of Ecological Units (Cleland et al, 181-200):
DomainDivisionProvinceSectionSubsectionLandtype AssociationLandtypeLandtype Phase.

Supporting information

Inventory data references

NRI: references to Natural Resource Inventory data
Information presented here has been derived from data collection on private and federal lands using:
• Double Sampling (clipped 2 of 5 plots)*
• Rangeland Health (Pellant et al., 2005)
• Soil Stability (Pellant et al., 2005)
• Line Point Intercept : Foliar canopy, basal cover (Forb, Graminoid, Shrub, subshrub, Lichen, Moss, Rock fragments, bare ground, % Litter) (Herrick et al., 2005)
• Soil pedon descriptions collected on site (Schoeneberger et al., 2012)

*NRCS double-sampling method, CO NRCS Similarity Index Worksheet 528(1).
Additional reconnaissance data collection using numerous ocular estimates and other inventory data; NRCS clipping data for USDA program support; Field observations from experienced range trained personnel. Specific data information is contained in individual landowner/user case files and other files located in county NRCS field offices.

Those involved in developing the 2004 site description include: Harvey Sprock, Rangeland Management Specialist, CO-NRCS; Ben Berlinger, Rangeland Management Specialist, CO-NRCS; James Borchert, Soil Scientist, CO-NRCS; Terri Skadeland, Biologist, CO-NRCS.

References

Guyette, R.P., M.C. Stambaugh, D.C. Dey, and R. Muzika. 2012. Predicting Fire Frequency with Chemistry and Climate. Ecosystems 15:322–335.
Stewart, O.C., H.T. Lewis, and M.K. Anderson. 2002. Forgotten Fires: Native Americans and the Transient Wilderness. University of Oklahoma Press, Norman, OK. 351p.

Other references

Data collection for this ecological site was done in conjunction with the progressive soil surveys within the 67B Central High Plains (Southern Part) of Colorado. It has been mapped and correlated with soils in the following soil surveys: Adams County, Arapahoe County, Baca County, Bent County, Boulder County, Cheyenne County, El Paso County Area, Elbert County, Eastern Part, Kiowa County, Kit Carson County, Larimer County Area, Las Animas County Area, Lincoln County, Logan County, Morgan County, Prowers County, Washington County, Weld County, Northern Part, and Weld County, Southern Part.

30 Year Climatic and Hydrologic Normals (1981-2010) Reports. National Water and climate Center: Portland, OR. August 2015

ACIS-USDA Field Office Climate Data (WETS), period of record 1971-2000 http://agacis.rcc-acis.org (powered by WRCC) Accessed March 2016

Andrews, R. and R. Righter. 1992. Colorado Birds. Denver Museum of Natural History, Denver, CO. 442

Armstrong, D.M. 1972. Distribution of mammals in Colorado. Univ. Kansas Museum Natural History Monograph #3. 415.

Butler, LD., J.B. Cropper, R.H. Johnson, A.J. Norman, G.L. Peacock, P.L. Shaver, and K.E. Spaeth. 1997, revised 2003. National Range and Pasture Handbook. National Cartography and Geospatial Center’s Technical Publishing Team: Fort Worth, TX. http://www.glti.nrcs.usda.gov/technical/publications/nrph.html Accessed August 2015

Clark, J., E. Grimm, J. Donovan, S. Fritz, D. Engrstom, and J. Almendinger. 2002. Drought cycles and landscape responses to past Aridity on prairies of the Northern Great Plains, USA. Ecology, 83(3), 595-601.

Cleland, D., P. Avers, W.H. McNab, M. Jensen, R. Bailey, T. King, and W. Russell. 1997. National Hierarchical Framework of Ecological Units, published in Ecosystem Management: Applications for Sustainable Forest and Wildlife Resources, Yale University Press

Cooperative climatological data summaries. NOAA. Western Regional Climate Center: Reno, NV. Web. http://www.wrcc.dri.edu/climatedata/climsum Accessed August 2015

Egan, Timothy. 2006. The Worst Hard Time. Houghton Mifflin Harcourt Publishing Company: New York, NY.

Fitzgerald, J.P., C.A. Meaney, and D.M. Armstrong. 1994. Mammals of Colorado. Denver Museum of Natural History, Denver, CO. 467. Hammerson, G.A. 1986. Amphibians and reptiles in Colorado. CO Div. Wild. Publication Code DOW-M-I-3-86. 131.

Herrick, Jeffrey E., J.W. Van Zee, K.M. Haystad, L.M. Burkett, and W.G. Witford. 2005. Monitoring Manual for Grassland, Shrubland, and Savanna Ecosystems, Volume II. U.S. Dept. of Agriculture, Agricultural Research Service. Jornada Experimental Range, Las Cruces, N.M.

Kingery, H., Ed. (1998) Colorado Breeding Birds Atlas. Dist. CO Wildlife Heritage Foundation: Denver, CO. 636.

National Water & Climate Center. USDA-NRCS. USDA Pacific Northwest Climate Hub: Portland, OR. http://www.wcc.nrcs.usda.gov/ Accessed March 2016

National Weather Service Co-op Program. 2010. Colorado Climate Center. Colorado State Univ. Web. http://climate.atmos.colostate.edu/dataaccess.php March 2016

Pellant, M., P. Shaver, D.A. Pyke, J.E. Herrick. (2005) Interpreting Indicators of Rangeland Health, Version 4. BLM National Business Center Printed Materials Distribution Service: Denver, CO.

PLANTS Database. 2015. USDA-NRCS. Web. http://plants.usda.gov/java/ Accessed August 2015. February 2016

PRISM Climate Data. 2015. Prism Climate Group. Oregon State Univ. Corvallis, OR. http://www.prism.oregonstate.edu/ Accessed August 2015.

Rennicke, J. 1990. Colorado Wildlife. Falcon Press, Helena and Billings, MT and CO Div. Wildlife, Denver CO. 138.

Schoeneberger, P.J., D.A. Wysockie, E.C. Benham, and Soil Survey Staff. 2012. Field book for describing and sampling soils, Version 3.0. Natural Resources Conservation Service, National Soil Survey Center: Lincoln, NE.

The Denver Posse of Westerners. 1999. The Cherokee Trail: Bent’s Old Fort to Fort Bridger. The Denver Posse of Westerners, Inc. Johnson Printing: Boulder, CO

U.S. Dept. of Agriculture, Agricultural Research Service. September 1991. Changes in Vegetation and Land Use I eastern Colorado, A Photographic study, 1904-1986.

U.S. Dept. 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. US Department of Agriculture Handbook 296.

U.S. Dept. of Agriculture, Natural Resources Conservation Service. National Geospatial Center of Excellence. Colorado annual Precipitation Map from 1981-2010, Annual Average Precipitation by State

U.S. Dept. of Agriculture, Natural Resources Conservation Service. 2009. Part 630, Hydrology, National Engineering Handbook

U.S. Dept. of Agriculture, Natural Resources Conservation Service. 1972-2012. National Engineering Handbook Hydrology Chapters. http://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/water/?&cid=stelprdb1043063 Accessed August 2015.

U.S. Dept. of Agriculture, Natural Resources Conservation Service. National Soil Survey Handbook title 430-VI. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ref/?cid=nrcs142p2_054242 Accessed July 2015

U.S. Dept. of Agriculture, Soil Survey Division Staff. 1993. Soil Survey Manual.

U.S. Dept. of Agriculture.1973. Soil Survey of Baca County, Colorado.

U.S. Dept. of Agriculture. 1970. Soil Survey of Bent County, Colorado.

U.S. Dept. of Agriculture. 1968. Soil Survey of Crowley County, Colorado.

U.S. Dept. of Agriculture. 1981 Soil Survey of El Paso County Area, Colorado.

U.S. Dept. of Agriculture. 1995. Soil Survey of Fremont County Area, Colorado.

U.S. Dept. of Agriculture. 1983. Soil Survey of Huerfano County Area, Colorado.

U.S. Dept. of Agriculture.1981. Soil Survey of Kiowa County, Colorado.

Western Regional Climate Center. 2022. Climate of Colorado, climate of the eastern plains. https://wrcc.dri.edu/Climate/narrative_co.php (accessed 9 August 2022).

Additional Literature:

Clark, J., E. Grimm, J. Donovan, S. Fritz, D. Engrstom, and J. Almendinger. 2002. Drought cycles and landscape responses to past Aridity on prairies of the Northern Great Plains, USA. Ecology, 83(3), 595-601.

Collins, S. and S. Barber. (1985). Effects of disturbance on diversity in mixed-grass prairie. Vegetation, 64, 87-94.

Egan, Timothy. 2006. The Worst Hard Time. Houghton Mifflin Harcourt Publishing Company: New York, NY.

Hart, R. and J. Hart. 1997. Rangelands of the Great Plains before European Settlement. Rangelands, 19(1), 4-11.

Hart, R. 2001. Plant biodiversity on shortgrass steppe after 55 years of zero, light, moderate, or heavy cattle grazing. Plant Ecology, 155, 111-118.

Heitschmidt, Rodney K., J.W. Stuth, (edited by). 1991. Grazing Management, an Ecological Perspective. Timberland Press, Portland, OR.

Jackson, D. 1966. The Journals of Zebulon Montgomery Pike with letters & related documents. Univ. of Oklahoma Press, First edition: Norman, OK.

Mack, Richard N., and J.N. Thompson. 1982. Evolution in Steppe with Few Large, Hooved Mammals. The American Naturalist. 119, No. 6, 757-773.

Reyes-Fox, M., Stelzer H., Trlica M.J., McMaster, G.S., Andales, A.A., LeCain, D.R., and Morgan J.A. 2014. Elevated CO2 further lengthens growing season under warming conditions. Nature, April 23 2014.Available online. http://www.nature.com/nature/journal/v510/n7504/full/nature13207.html, accessed March 2017.

Stahl, David W., E.R. Cook, M.K. Cleaveland, M.D. Therrell, D.M. Meko, H.D. Grissino-Mayer, E. Watson, and B.H. Luckman. Tree-ring data document 16th century megadrought over North America. 2000. Eos, 81(12), 121-125.

The Denver Posse of Westerners. 1999. The Cherokee Trail: Bent’s Old Fort to Fort Bridger. The Denver Posse of Westerners, Inc. Johnson Printing: Boulder, CO.

U.S. Dept. of Agriculture. 2004. Vascular plant species of the Comanche National Grasslands in southeastern Colorado. US Forest Service. Rocky Mountain Research Station. Fort Collins, CO.

Zelikova, Tamara Jane, D.M. Blumenthal, D.G. Williams, L. Souza, D.R. LeCain, J.Morgan. 2014. Long-term Exposure to Elevated CO2 Enhances Plant Community Stability by Suppressing Dominant Plant Species in a Mixed-Grass Prairie. Ecology, 2014 issue. Available online. www.pnas.org/cgi/doi/10.1073/pnas.1414659111.

Contributors

Kimberly Diller, Ecological Site Specialist, NRCS MLRA, Pueblo SSO
Andy Steinert, MLRA 67B Soil Survey Leader, NRCS MLRA Fort Morgan SSO
Ben Berlinger, Rangeland Management Specialist, Retired NRCS La Junta, CO
Doug Whisenhunt, Ecological Site Specialist, NRCS MLRA, Pueblo SSO

Approval

Kirt Walstad, 9/08/2023

Acknowledgments

Program Support:
Rachel Murph, NRCS State Rangeland Management Specialist-QC, Denver, CO
David Kraft, NRCS MLRA Ecological Site Specialist-QA, Emporia, KS
Josh Saunders, Rangeland Management Specialist-QC, NRCS Fort Morgan, CO
Patty Knupp, Biologist, Area 3, NRCS Pueblo, CO
Noe Marymor, Biologist, Area 2, NRCS Greeley, CO
Richard Mullaney, Resource Conservationist, Retired., NRCS, Akron, CO
Chad Remley, Regional Director, N. Great Plains Soil Survey, Salina, KS
B.J. Shoup, State Soil Scientist, Denver
Eugene Backhaus, State Resource Conservationist, Denver
Carla Green Adams, Editor, NRCS, Denver, CO

Partners/Contributors:
Rob Alexander, Agricultural Resources, Boulder Parks & Open Space, Boulder, CO
David Augustine, Research Ecologist, Agricultural Research Service, Fort Collins, CO
John Fusaro, Rangeland Management Specialist, NRCS, Fort Collins, CO
Jeff Goats, Resource Soil Scientist, NRCS, Pueblo, CO
Clark Harshbarger, Resource Soil Scientist, NRCS, Greeley, CO
Mike Moore, Soil Scientist, NRCS MLRA Fort Morgan SSO
Tom Nadgwick, Rangeland Management Specialist, NRCS, Akron CO
Dan Nosal, Rangeland Management Specialist, NRCS, Franktown, CO
Steve Olson, Botanist, USFS, Pueblo, CO
Randy Reichert, Rangeland Specialist, retired, USFS, Nunn, CO
Don Schoderbeck, Range Specialist, CSU Extension, Sterling CO
Terri Schultz, The Nature Conservancy, Ft. Collins, CO
Chris Tecklenburg, Ecological Site Specialist, Hutchison, KS

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)	Harvey Sprock, Ben Berlinger, Daniel Nosal
Contact for lead author	Harvey Sprock, Area Rangeland Management Specialist, Greeley, CO
Date	11/17/2004
Approved by	Kirt Walstad
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
None
Presence of water flow patterns:
None to minimal on gentle slopes (< 15 percent). Flow paths should be broken, irregular in appearance. As slope steepness increases, flow paths become more apparent and may be connected.
Number and height of erosional pedestals or terracettes:
None to slight on gentle slopes. Expect some evidence of pedestalled plants when slopes exceed 15 percent.
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
5 percent or less bare ground, with bare patches generally less than 3 inches. Extended drought may increase bare ground 5 to 10 percent.
Number of gullies and erosion associated with gullies:
None
Extent of wind scoured, blowouts and/or depositional areas:
None
Amount of litter movement (describe size and distance expected to travel):
Litter movement is associated with water flow patterns and may move as much as 1 to 3 feet down slope during severe precipitation events, especially on steeper slopes.
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Stability class rating is anticipated to be 4 to 5 in interspaces at soil surface. These values need verification.
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Average SOM ranges from 2 to 4 percent. Soils are typically deep to very deep, excessive to well drained. Surface texture includes gravelly loamy sand, gravelly sandy loam, and gravelly loam that are weakly developed. A-horizon ranges from 0 to 4 inches in depth with a grayish brown color. Structure is moderate to weak fine granular. Rock (gravels) are inherent to the site.
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Raindrop impact is reduced by the diverse grass, forb, shrub functional/structural groups and root structure. This slows overland flow and provides increased time for infiltration to occur. Extended drought, wildfire or both may reduce basal density, canopy cover, and litter amounts (primarily from tall, warm-season bunch and rhizomatous grasses), resulting in decreased infiltration and increased runoff on steep slopes following intense rainfall events.
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
None
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:
Warm-season mid bunchgrass >>

Sub-dominant:
Warm-season short grass > warm-season tall grass > shrubs/half-shrubs > warm-season forbs >

Other:
Cool-season mid bunchgrass

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
None to slight.
Average percent litter cover (%) and depth ( in):
20 to 35 percent litter cover at 0.25 or less inch depth. Litter cover during and following extended drought can range from 10 to 20 percent.
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
500 lbs./ac. low precip years; 950 lbs./ac. average precip years; 1400 lbs./ac. high precip years. After extended drought or the first growing season following wildfire, production may be significantly reduced by 200-400 lbs./ac.
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:
Invasive plants should not occur in the reference plant community. Cheatgrass, Russian thistle, burningbush, other non-native annuals may invade following extended drought or fire assuming a seed source is available.
Perennial plant reproductive capability:
The only limitations are weather-related, wildfire, natural disease, and insects that may temporarily reduce reproductive capability.