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Ecological site EX049X01X210

Sandy Foothill Palmer Divide

Last updated: 4/07/2025
Accessed: 04/27/2025

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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.

MLRA notes

Major Land Resource Area (MLRA): 049X–Southern Rocky Mountain Foothills

Major Land Resource Area (MLRA) 49, Southern Rocky Mountain Foothills, comprises approximately 11,130 square miles running north to south, from south-central Wyoming (27 percent), the length of the Front Range of Colorado (58 percent), and into north-central New Mexico (15 percent). Almost half of this area occurs in the Southern Rocky Mountains and Wyoming Basin provinces in the Rocky Mountain system. The remainder is in the Colorado Pediment, Raton, and High Plains Section of the Great Plains Province of the Interior Plains. The northern part consists of the Laramie Mountains. The central and southern parts generally are bounded on the east by the Great Plains and on the west by the Southern Rocky Mountains (USDA Ag. Handbook 296). The average elevation ranges from 5,000 to 8,000 feet. Annual precipitation ranges from 10 to 35 inches.

LRU notes

The Palmer Divide Land Resource Unit (LRU) is a transition zone between the mountains and plains and describes the central Colorado foothills of the Front Range, including the Palmer Divide. It includes the cities of Highlands Ranch, Castle Rock, and Kiowa in Douglas and Elbert counties. The Black Forest-Palmer Divide area is central, while Cheyenne Mountain State Park at Colorado Springs is the southernmost extent in El Paso County. It is characterized by Gambel oak (Quercus gambelii) and ponderosa pine (Pinus ponderosa), with ponderosa pine increasing at higher elevations. The ponderosa pine transitions into grasslands on the drier eastern fringes as it transitions into the plains. This area was historically used for ranching, limited farming, logging, mining, and quarry activities.

The area experienced an influx of people during the Colorado Gold Rush of 1859. Because of its proximity to Denver and Colorado Springs, many of the original ranches and small towns have been converted to subdivisions, small acreages, and suburbs. Some cities, such as Castle Rock, have zoned "open space" for recreation.

Ecological site concept

The Sandy Foothill site is a run-off site that receives no extra water beyond normal precipitation. It is not influenced by rock fragments in the surface horizon and has sandy surface textures. Positioned on gently sloping to rolling hills and uplands the site ranges from 5,500 to 7,000 feet in elevation and is usually on slopes that vary from nearly level to 10 percent. The soils are moderately deep to very deep. They are typically well-drained with moderate to moderately high permeability. The surface layer is most commonly sandy loam, and occasionally loamy sand.

Associated sites

EX049X01X214	Gravelly Foothill Palmer Divide This site is intermixed with and often positioned higher on the landscape than the sandy site.

EX049X01X214

Gravelly Foothill Palmer Divide

This site is intermixed with and often positioned higher on the landscape than the sandy site.

Similar sites

EX049X01X202	Loamy Foothill Palmer Divide This site has a fine-loamy family particle size and has surface texture of loam, silt loam or fine sandy loam and is 20 to 60 inches in depth.
EX049X01X208	Clayey Foothill Palmer Divide This site has a fine family particle size and has surface textures of clay loam, clay, silty clay, or silty clay loam.

EX049X01X202

Loamy Foothill Palmer Divide

This site has a fine-loamy family particle size and has surface texture of loam, silt loam or fine sandy loam and is 20 to 60 inches in depth.

EX049X01X208

Clayey Foothill Palmer Divide

This site has a fine family particle size and has surface textures of clay loam, clay, silty clay, or silty clay loam.

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Prunus pumila var. besseyi (2) Atriplex canescens
Herbaceous	(1) Andropogon gerardii (2) Calamovilfa longifolia

Legacy ID

R049XC210CO

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Physiographic features

This site is commonly found on gently sloping to rolling hills and uplands on hills, valley sides, and alluvial fan remnants. It is usually on slopes that vary from nearly level to 10 percent. Elevation ranges from 5,500 feet to 7,000 feet.

Table 2. Representative physiographic features

Landforms	(1) Hills > Hill (2) Hills > Upland slope (3) Alluvial plain remnant > Alluvial fan (4) Hills > Valley side
Flooding duration	Extremely brief (0.1 to 4 hours) to very brief (4 to 48 hours)
Flooding frequency	None to very rare
Ponding frequency	None
Elevation	5,500 – 6,820 ft
Slope	10%
Water table depth	60 in
Aspect	Aspect is not a significant factor

Table 3. Representative physiographic features (actual ranges)

Flooding duration	Extremely brief (0.1 to 4 hours) to very brief (4 to 48 hours)
Flooding frequency	None to very rare
Ponding frequency	None
Elevation	5,500 – 7,000 ft
Slope	22%
Water table depth	60 in

Climatic features

The average annual precipitation is 14 to 19 inches per year but can vary from 11 to 20 inches depending upon the year and location within the LRU. Approximately 60 to 75 percent of the annual precipitation occurs during the growing season from late April to late September. The Rocky Mountains to the west intercept much of the precipitation from Pacific storms during the winter. Snowfall can vary from 39 inches to 75 inches, depending upon elevation and location. Snowfall averages 63 inches annually across the LRU. Wind speeds average 10 miles per hour annually. Daytime winds are generally stronger than nighttime, and occasional strong storms may bring brief periods of high winds with gusts to more than 60 miles per hour.

The average length of the freeze-free period is 142 days but varies from 111 to 172 days in five (5) out of 10 years. The average date of first freeze (28 degrees or below) in the fall is September 22, and the average last freeze in the spring is May 17. July is the hottest month and January is the coldest. Summer temperatures are moderate, with average highs in the low 80s and occasionally reaching the mid-90s.

Summer nights are comfortably cool, with lows averaging in the 50s. Higher elevations can receive a dusting of snow in early September. Severe cold is normally of short duration. Summer humidity is low and evaporation is high.

Cool-season plants generally begin growth from April 1 to April 15. Native warm-season plants typically begin growth about May 1 to May 15. Cool-season plants generally continue to grow through the summer and fall, in comparison to the warmer and drier eastern plains where cool-season plants exhibit summer dormancy.

Table 4. Representative climatic features

Frost-free period (characteristic range)	104-119 days
Freeze-free period (characteristic range)	133-139 days
Precipitation total (characteristic range)	14-19 in
Frost-free period (actual range)	101-125 days
Freeze-free period (actual range)	131-143 days
Precipitation total (actual range)	11-20 in
Frost-free period (average)	112 days
Freeze-free period (average)	136 days
Precipitation total (average)	17 in

Characteristic range

Actual range

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Figure 1. Monthly precipitation range

Characteristic range

Actual range

Bar

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Figure 2. Monthly minimum temperature range

Characteristic range

Actual range

Bar

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Figure 3. Monthly maximum temperature range

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Figure 4. Monthly average minimum and maximum temperature

Figure 5. Annual precipitation pattern

Figure 6. Annual average temperature pattern

Climate stations used

(1) CASTLE ROCK [USC00051401], Castle Rock, CO
(2) COLORADO SPRINGS MUNI AP [USW00093037], Colorado Springs, CO
(3) RUSH 1N [USC00057287], Rush, CO
(4) ELIZABETH 2NW [USC00052631], Elizabeth, CO
(5) PARKER 6 E [USC00056326], Parker, CO

Soil features

The soils of this site are typically very deep but also include deep and moderately deep soils. They are well drained with moderate to moderately high permeability. These soils are normally formed in alluvium, eolian deposits, and sandstone residuum. They occur frequently on hills, valley sides, and alluvial fan remnants and less frequently on ridges, active alluvial fans, and stream terraces. The available water capacity is typically moderate or low. Low available water capacity is more likely on sites with moderately deep soils and/or high sand contents. The soil surface layer ranges from five to 17 inches thick and is most commonly sandy loam and occasionally loamy sand. Subsurface textures are typically loamy or sandy. Rock fragments are not high on most sites. However, fragments (dominantly in the less than 3-inch fraction) can occasionally cover as much as 25 percent of the surface and comprise up to 50 percent by volume of the subsoil.

The soil taxonomic order is predominantly mollisols with dark surfaces and high organic matter in the surface and upper subsoil. Less frequently Aridisols characterized by dryer conditions and less organic matter are found. The soil moisture regime is typically ustic (aridic subgroup) and occasionally aridic (ustic subgroup) soils. The soil temperature regime is mesic. The pH of these soils ranges from slightly acidic to moderately alkaline.

Major soil series correlated to this ecological site include:
Ascalon sandy loam, Blakeland sandy loam, Blakeland loamy sand, Blendon sandy loam, Bresser sandy loam, Nelson fine sandy loam, Tassel fine sandy loams, Stapleton sandy loam, Terry sandy loam, Truckton sandy loam, and Truckton loamy sand.
Other soil series that have been correlated to this site include:
Bijou sandy loam, Bressner loamy sand, Gove sandy loam, Kutch sandy loam, Orsa coarse sandy loam, Renohill sandy loam (reddish variant), and Paymaster sandy loam.

Figure 7. Bresser Series Profile.

Table 5. Representative soil features

Parent material	(1) Alluvium – sandstone (2) Residuum – sedimentary rock (3) Eolian deposits
Surface texture	(1) Gravelly sandy loam (2) Loamy sand
Drainage class	Well drained to excessively drained
Permeability class	Moderate to rapid
Soil depth	40 – 60 in
Surface fragment cover <=3"	50%
Surface fragment cover >3"	10%
Available water capacity (0-40in)	3 – 8 in
Calcium carbonate equivalent (0-40in)	10%
Electrical conductivity (0-40in)	2 mmhos/cm
Sodium adsorption ratio (0-40in)	Not specified
Soil reaction (1:1 water) (0-40in)	6.1 – 8.4

Table 6. Representative soil features (actual values)

Drainage class	Well drained to excessively drained
Permeability class	Moderate to rapid
Soil depth	40 – 60 in
Surface fragment cover <=3"	50%
Surface fragment cover >3"	10%
Available water capacity (0-40in)	3 – 8 in
Calcium carbonate equivalent (0-40in)	10%
Electrical conductivity (0-40in)	2 mmhos/cm
Sodium adsorption ratio (0-40in)	Not specified
Soil reaction (1:1 water) (0-40in)	6.1 – 8.4

Ecological dynamics

The Sandy Foothill ecological site is characterized by four states: Reference, Altered, Invaded, and Degraded states. Transitions between states and their respective communities are primarily driven by natural disturbance regimes. The most significant of these are periodic drought, grazing that results in chronic defoliation, and the natural fire regime. The timing and magnitude of these disturbances affect the various stages of the vegetative communities as described in the state-and-transition model (STM).

The historical fire frequency of the the Palmer Divide LRU ranges from 6 to 10 years (Guyette, et al 2012). The impact of fire over the past 50 years has been relatively insignificant due to wildfire suppression and the lack of acceptance of prescribed fire as a management tool. Prolonged drought and fire suppression have increased the frequency and intensity of periodic wildfires in the area.

Most of this ecological site has been fragmented due to tillage and urban development.

The state and transition model (STM) diagram for this ecological site is depicted in this section. Thorough descriptions of each state, transition, plant community, and pathway are found following model. This STM is based on available experimental research, field observations, professional consensus, and interpretations. While based on the best available information, creating the STM is a dynamic process. The document may be modified as knowledge of the specific ecological processes increases.

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

R2A	-	Prescribed Grazing. Prescribed Burning.

State 1 submodel, plant communities

1.1. Big Bluestem, Prairie Sandreed, and Switchgrass

1.2. Decadent Big Bluestem, Switchgrass, and Prairie Sandreed

1.3. Blue Grama, Prairie Sandreed, Switchgrass, and Big Bluestem

1.2A	-	Prescribed Grazing. Prescribed Burning.
1.3A	-	Prescribed Grazing. Prescribed Burning.

State 1
Reference

The Reference state of the Sandy Foothill Palmer Divide ecological site is characterized by three distinct plant communities. These communities represent the natural range of variability and fluctuate within the parameters that define the state. Precipitation patterns and management strategies regarding herbivory and fire frequency are the primary drivers that determine the distribution of these communities throughout this state (Anderson et al, 1982).

Characteristics and indicators. This state has not been sod-busted or overly eroded and has slight to moderate vegetative deviation from the historical mixed-grass prairie community.

Resilience management. The Reference state can be maintained by managing herbivory with appropriate stocking rates, and the timing and duration of grazing periods. Maintaining a natural fire regime with appropriately timed prescribed burning also contributes to this resilience.

Dominant plant species

western sandcherry (Prunus pumila var. besseyi), shrub
spreading buckwheat (Eriogonum effusum), shrub
big bluestem (Andropogon gerardii), grass
prairie sandreed (Calamovilfa longifolia), grass
switchgrass (Panicum virgatum), grass
Indiangrass (Sorghastrum nutans), grass
purple prairie clover (Dalea purpurea), other herbaceous
scarlet globemallow (Sphaeralcea coccinea), other herbaceous

Community 1.1
Big Bluestem, Prairie Sandreed, and Switchgrass

The potential vegetation for the Big Bluestem, Prairie Sandreed, and Switchgrass community is about 70 to 85 percent grasses and grass-like plants, 10 to 15 percent forbs, and five to 15 percent woody plants. The major grasses include big bluestem (Andropogon gerardii), prairie sandreed (Calamovilfa longifolia), switchgrass (Panicum virgatum), and Indiangrass (Sorghastrum nutans). Needle and thread (Hesperostipa comata) and western wheatgrass (Pascopyrum smithii) are major cool-season mid-grasses in this plant community and are valuable forage plants in late spring and early summer. Sub-dominant grasses include blue grama (Bouteloua gracilis), little bluestem (Schizachryium scoparium), sideoats grama, (Bouteloua curtipendula), and sand dropseed (Sporobolus cryptandrus). Major forbs are purple prairieclover, upright prairie coneflower (Ratibida columnifera), scarlet globemallow, and dotted gayfeather (Liatris punctata). A minor amount of shrubs such as western sandcherry, spreading buckwheat, and soapweed yucca (Yucca glauca) may also occur. This plant community is diverse, stable, and productive. Litter is uniformly distributed with very little movement off site, and natural plant mortality is very low. It is well suited to carbon sequestration, water infiltration, wildlife use by many species, livestock use, and is aesthetically pleasing. Community dynamics, nutrient cycle, water cycle, and energy flow are functioning properly. This community is resistant to many disturbances with the exceptions of excessive herbivory, tillage, and development. Total annual production averages 1,900 pounds pounds of air-dry vegetation per acre and ranges from 1,000 to 2,700.

Resilience management. This community can be maintained by managing herbivory with appropriate stocking rates and timing and duration of grazing periods. Maintaining a natural fire regime with appropriately timed prescribed burning also contributes to resilience.

Dominant plant species

western sandcherry (Prunus pumila var. besseyi), shrub
spreading buckwheat (Eriogonum effusum), shrub
big bluestem (Andropogon gerardii), grass
prairie sandreed (Calamovilfa longifolia), grass
switchgrass (Panicum virgatum), grass
Indiangrass (Sorghastrum nutans), grass
purple prairie clover (Dalea purpurea), other herbaceous
upright prairie coneflower (Ratibida columnifera), other herbaceous
scarlet globemallow (Sphaeralcea coccinea), other herbaceous

Figure 8. Annual production by plant type (representative values) or group (midpoint values)

Table 7. Annual production by plant type

Plant type	Low (lb/acre)	Representative value (lb/acre)	High (lb/acre)
Grass/Grasslike	775	1475	2100
Forb	125	235	330
Shrub/Vine	100	190	270
Total	1000	1900	2700

Table 8. Ground cover

Tree foliar cover	0-1%
Shrub/vine/liana foliar cover	3-10%
Grass/grasslike foliar cover	50-80%
Forb foliar cover	1-15%
Non-vascular plants	0-1%
Biological crusts	0-1%
Litter	0-15%
Surface fragments >0.25" and <=3"	0-1%
Surface fragments >3"	0-1%
Bedrock	0%
Water	0%
Bare ground	0-10%

Table 9. Soil surface cover

Tree basal cover	0-1%
Shrub/vine/liana basal cover	0-5%
Grass/grasslike basal cover	7-15%
Forb basal cover	0-5%
Non-vascular plants	0-1%
Biological crusts	0-1%
Litter	0%
Surface fragments >0.25" and <=3"	0-5%
Surface fragments >3"	0-1%
Bedrock	0%
Water	0%
Bare ground	50-90%

Figure 9. Plant community growth curve (percent production by month). CO4902, Warm season tallgrass dominant; MLRA 49C; upland sandy 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
			5	15	35	25	15	5

Community 1.2
Decadent Big Bluestem, Switchgrass, and Prairie Sandreed

This plant community occurs when grazing is removed for long periods of time in the absence of fire. Plant composition is similar to the 1.1 community but plant vigor and individual species production arereduced. White sagebrush (Artemisia ludoviciana) and prairie sagebrush (Artemisia frigida) increase. The semiarid environment and the absence of animal impact to break down litter slows nutrient recycling. Excessive litter also limits sunlight from reaching plant crowns, reducing seed germination and seedling establishment. In advanced stages, plant mortality increases and erosion occurs as bare ground increases.

Resilience management. To sustain this community, occasional light disturbance from herbivory or prescribed fire is recommended.

Dominant plant species

western sandcherry (Prunus pumila var. besseyi), shrub
spreading buckwheat (Eriogonum effusum), shrub
big bluestem (Andropogon gerardii), grass
prairie sandreed (Calamovilfa longifolia), grass
switchgrass (Panicum virgatum), grass
purple prairie clover (Dalea purpurea), other herbaceous
upright prairie coneflower (Ratibida columnifera), other herbaceous

Figure 10. Plant community growth curve (percent production by month). CO4904, Warm season tallgrass excess litter; MLRA 49C; upland sandy 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
				15	30	25	20	10

Community 1.3
Blue Grama, Prairie Sandreed, Switchgrass, and Big Bluestem

Blue grama has increased with a corresponding decrease in the relative amount of warm-season tallgrasses such as big bluestem, prairie sandreed, and switchgrass. Sand dropseed, hairy false goldenaster (Heterotheca villosa), Cuman ragweed (Ambrosia psilostachya), white locoweed (Oxytropis sericea), and Drummond's milkvetch (Astragalus drummindii) have also increased. Spring grazing and summer deferment reduces the cool-season component (needle and thread and western wheatgrass), of this plant community and increases the warm-season component. Spring deferment and summer grazing increases the cool-season component and decreases the warm-season component (big bluestem, prairie sandreed, switchgrass) of this plant community. This plant community is relatively stable but at risk of losing some of the tallgrass species, palatable forbs, and shrubs. The reduction of tallgrass species, nitrogen-fixing forbs, key shrubs, and the increase of warm-season short-grasses has altered the biotic integrity of this plant community. The nutrient cycle, water cycle, and energy flow are at risk of becoming impaired.

Resilience management. Seasonal, moderate herbivory and maintenance of the historic fire regime sustains this plant community.

Dominant plant species

spreading buckwheat (Eriogonum effusum), shrub
western sandcherry (Prunus pumila var. besseyi), shrub
blue grama (Bouteloua gracilis), grass
prairie sandreed (Calamovilfa longifolia), grass
switchgrass (Panicum virgatum), grass
big bluestem (Andropogon gerardii), grass
Cuman ragweed (Ambrosia psilostachya), other herbaceous
hairy false goldenaster (Heterotheca villosa), other herbaceous

Figure 11. Plant community growth curve (percent production by month). CO4903, Warm season shortgrass dominant; MLRA 49C; upland sandy 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
				10	40	25	20	5

Pathway 1.1A
Community 1.1 to 1.2

Lack of disturbances such as herbivory, mowing, and periodic fire moves this plant community to the Decadent Big Bluestem, Switchgrass, and Prairie Sandreed community. This community is characterized by excessive litter, low plant density, and increased plant mortality.

Context dependence. The amount of growing season precipitation affects the rate and degree of this community shift.

Pathway 1.1B
Community 1.1 to 1.3

Excessive herbivory without adequate recovery periods between grazing events, and interruption of the historical fire regime shift this community to the Blue Grama, Prairie Sandreed, Switchgrass, and Big Bluestem community.

Context dependence. The amount of growing season precipitation affects the rate and magnitude of this transition.

Pathway 1.2A
Community 1.2 to 1.1

Prescribed grazing with adequate recovery periods and proper stocking rate restore this plant community to the Big Bluestem, Prairie Sandreed, and Switchgrass community. Prescribed burning accelerates this process.

Context dependence. Abundant growing season precipitation accelerates this process, while drought hampers recovery.

Conservation practices

Prescribed Burning
Prescribed Grazing

Pathway 1.2B
Community 1.2 to 1.3

Excessive long-term herbivory causes this community to transition to the 1.3 community.

Context dependence. Local precipitation patterns affect the rate and magnitude of this shift.

Pathway 1.3A
Community 1.3 to 1.1

Herbivory with adequate recovery periods restores this community to the 1.1 community. Appropriately timed prescribed burning accelerates this transition.

Context dependence. Adequate seasonal precipitation accelerates this process while drought hampers the restoration.

Conservation practices

Prescribed Burning
Prescribed Grazing

State 2
Altered

The Altered state is characterized by the Blue Grama plant community. An ecological threshold has been crossed relative to the Reference state resulting in loss of resilience. This state is relatively resistant to disturbances due to this sod forming growth form of blue grama.

Characteristics and indicators. This state has a lack of diversity due to the dominance of blue grama and a corresponding reduction in the amount of warm-season tallgrasses. The structure of the plant community has changed from tallgrasses to shortgrass.

Resilience management. Light to moderate herbivory maintains this state.

Dominant plant species

spreading buckwheat (Eriogonum effusum), shrub
soapweed yucca (Yucca glauca), shrub
blue grama (Bouteloua gracilis), grass
sand dropseed (Sporobolus cryptandrus), grass
scarlet globemallow (Sphaeralcea coccinea), other herbaceous
Cuman ragweed (Ambrosia psilostachya), other herbaceous

Community 2.1
Blue Grama

Big bluestem, prairie sandreed, switchgrass, Indiangrass, needle and thread, and western wheatgrass have all significantly decreased. Blue grama dominates the plant community. Sand dropseed, along with forbs and shrubs such as hairy goldaster, Cuman ragweed, prairie sagewort, small soapweed (Yucca glauca) , and plains pricklypear (Opuntia polyacantha), have increased. This plant community remains stable but has lost significant production and biologic diversity. Nutrient and hydrologic cycles and energy flow are impaired. Desertification is advanced.

Resilience management. Light to moderate herbivory maintains this community.

Dominant plant species

prairie sagewort (Artemisia frigida), shrub
soapweed yucca (Yucca glauca), shrub
plains pricklypear (Opuntia polyacantha), shrub
blue grama (Bouteloua gracilis), grass
sand dropseed (Sporobolus cryptandrus), grass
hairy false goldenaster (Heterotheca villosa), other herbaceous
Cuman ragweed (Ambrosia psilostachya), other herbaceous

Figure 12. Plant community growth curve (percent production by month). CO4903, Warm season shortgrass dominant; MLRA 49C; upland sandy 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
				10	40	25	20	5

State 3
Degraded

The Blue Grama, Sleepygrass, Yucca, and Broom Snakeweed community characterizes this state. A further ecological threshold has been crossed as shown by a loss of resilience and resistance to disturbance.

Characteristics and indicators. An increase in the amount of bare ground is readily distinguishable. Plant community structure appears as patchy areas of blue grama and sleepygrass (Achnatherum robustum) with scattered shrubs such as soapweed yucca (Yucca glauca), broom snakeweed (Gutierrezia sarothrae), and plains pricklypear.

Resilience management. Light herbivory maintains this state.

Dominant plant species

broom snakeweed (Gutierrezia sarothrae), shrub
soapweed yucca (Yucca glauca), shrub
blue grama (Bouteloua gracilis), grass
sleepygrass (Achnatherum robustum), grass
hairy false goldenaster (Heterotheca villosa), other herbaceous
prairie sagewort (Artemisia frigida), other herbaceous

Community 3.1
Blue Grama, Sleepygrass, Yucca, and Broom Snakeweed

During the first stages of regression, less palatable forbs and shrubs like hairy goldaster, fringed sagebrush, and yucca increase. Under continued heavy grazing, sleepygrass and six weeks fescue replace blue grama . The amount of bare ground increases. This plant community phase is unstable. Desertification is well advanced and wind and water erosion are concerns.

Resilience management. This community is unstable, but light herbivory may maintain it's current condition.

Dominant plant species

soapweed yucca (Yucca glauca), shrub
broom snakeweed (Gutierrezia sarothrae), shrub
sleepygrass (Achnatherum robustum), grass
sixweeks fescue (Vulpia octoflora), grass

Dominant resource concerns

Sheet and rill erosion
Wind erosion
Ephemeral gully erosion
Classic gully erosion

Figure 13. Plant community growth curve (percent production by month). CO4923, Snakeweed, Pioneer Annual/Perennials, Bare Ground; MLRA 49. Warm/cool season, annual/perennial forbs.

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
		5	10	20	25	30	10

State 4
Invaded

The Invaded state is characterized by the Cheatgrass, Russian Thistle, and Broom Snakeweed community. An ecological threshold has been crossed as shown by a significant degradation of biologic integrity, and impaired hydrologic function.

Characteristics and indicators. The distinguishing characteristic is the dominance of invasive species.

Resilience management. This state is unstable.

Dominant plant species

broom snakeweed (Gutierrezia sarothrae), shrub
plains pricklypear (Opuntia polyacantha), shrub
cheatgrass (Bromus tectorum), grass
knapweed (Centaurea), other herbaceous
Russian thistle (Salsola), other herbaceous
Canada thistle (Cirsium arvense), other herbaceous

Community 4.1
Cheatgrass, Russian Thistle, and Broom Snakeweed

The community is dominated by invasive species. Production varies greatly depending on the plant density and weather conditions in any year.

Resilience management. This condition is not stable and desertification is well advanced. Wind and water erosion are concerns.

Dominant plant species

plains pricklypear (Opuntia polyacantha), shrub
soapweed yucca (Yucca glauca), shrub
sleepygrass (Achnatherum robustum), grass
cheatgrass (Bromus tectorum), grass
knapweed (Centaurea), other herbaceous
Russian thistle (Salsola), other herbaceous
Canada thistle (Cirsium arvense), other herbaceous

Dominant resource concerns

Sheet and rill erosion
Wind erosion
Ephemeral gully erosion
Classic gully erosion

Transition T1A
State 1 to 2

Excessive herbivory without adequate recovery periods and disruption of the natural fire regime.

Constraints to recovery. Impaired hydrologic function, reduced nutrient cycle, and altered energy flow due to the shallow root-pan that developed under the sod-bound blue grama.

Context dependence. Drought accelerates this transition.

Transition T1B
State 1 to 4

Excessive herbivory without adequate recovery periods and disruption of the natural fire regime. Tillage or disturbance and fragmentation associated with residential construction also causes this transition.

Constraints to recovery. Interruption of the hydrologic cycle and the complete loss of the historical structural functional groups make recovery to the Reference state highly unlikely.

Context dependence. Local precipitation patterns greatly influence the response of the vegetative community.

Restoration pathway R2A
State 2 to 1

Prescribed grazing management that allows adequate recovery and proper stocking facilitate recovery to the Reference state. Appropriately timed prescribed burning accelerates this process.

Context dependence. Local precipitation patterns influence the rate of recovery.

Conservation practices

Prescribed Burning
Prescribed Grazing

Transition T2A
State 2 to 3

Excessive herbivory without adequate recovery periods causes this transition. Interruption of the natural fire regime accelerates this process.

Constraints to recovery. Loss of a natural revegetation source, presence of a compaction layer in the soil due to lack of deep-rooted native grasses, reduced water infiltration, and increased surface runoff are all constraints to recovery once this threshold has been crossed.

Context dependence. Local precipitation patterns influence the development of the vegetative community.

Additional community tables

Table 10. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production (lb/acre)	Foliar cover (%)
Grass/Grasslike
1	Grass and Grasslike Plants			775–2100
	big bluestem	ANGE	Andropogon gerardii	285–475	20–35
	prairie sandreed	CALO	Calamovilfa longifolia	190–285	15–25
	switchgrass	PAVI2	Panicum virgatum	190–285	15–25
	Indiangrass	SONU2	Sorghastrum nutans	60–190	5–15
	blue grama	BOGR2	Bouteloua gracilis	35–135	5–15
	sideoats grama	BOCU	Bouteloua curtipendula	20–95	1–10
	needle and thread	HECO26	Hesperostipa comata	35–95	3–10
	western wheatgrass	PASM	Pascopyrum smithii	20–95	1–10
	little bluestem	SCSC	Schizachyrium scoparium	35–95	3–10
	mountain muhly	MUMO	Muhlenbergia montana	20–95	1–10
	sand dropseed	SPCR	Sporobolus cryptandrus	20–35	1–5
	thickspike wheatgrass	ELLA3	Elymus lanceolatus	20–35	1–5
	hairy grama	BOHI2	Bouteloua hirsuta	20–35	1–5
	Indian ricegrass	ACHY	Achnatherum hymenoides	20–35	1–5
	prairie Junegrass	KOMA	Koeleria macrantha	20–35	1–5
	Geyer's sedge	CAGE2	Carex geyeri	20–35	1–5
	threadleaf sedge	CAFI	Carex filifolia	0–20	0–1
	squirreltail	ELEL5	Elymus elymoides	0–20	0–1
Forb
2	Forbs			125–330
	purple prairie clover	DAPU5	Dalea purpurea	60–95	5–20
	scarlet globemallow	SPCO	Sphaeralcea coccinea	0–20	0–1
	upright prairie coneflower	RACO3	Ratibida columnifera	0–20	0–1
	Drummond's milkvetch	ASDR3	Astragalus drummondii	0–20	0–1
	Cuman ragweed	AMPS	Ambrosia psilostachya	0–20	0–1
	lacy tansyaster	MAPIP	Machaeranthera pinnatifida ssp. pinnatifida	0–20	0–1
	textile onion	ALTE	Allium textile	0–20	0–1
	red dome blanketflower	GAPI	Gaillardia pinnatifida	0–20	0–1
	threadleaf ragwort	SEFLF	Senecio flaccidus var. flaccidus	0–20	0–1
	tarragon	ARDR4	Artemisia dracunculus	0–20	0–1
	slimflower scurfpea	PSTE5	Psoralidium tenuiflorum	0–20	0–1
	hairy false goldenaster	HEVI4	Heterotheca villosa	0–20	0–1
	scarlet gilia	IPAG	Ipomopsis aggregata	0–20	0–1
	common starlily	LEMO4	Leucocrinum montanum	0–20	0–1
	dotted blazing star	LIPU	Liatris punctata	0–20	0–1
	sand lupine	LUAM	Lupinus ammophilus	0–20	0–1
	white locoweed	OXSE	Oxytropis sericea	0–20	0–1
	broadbeard beardtongue	PEAN4	Penstemon angustifolius	0–20	0–1
	prairie spiderwort	TROC	Tradescantia occidentalis	0–20	0–1
	grassy deathcamas	ZIVEG	Zigadenus venenosus var. gramineus	0–20	0–1
	twolobe larkspur	DENU2	Delphinium nuttallianum	0–20	0–1
	western wallflower	ERAS2	Erysimum asperum	0–20	0–1
	white sagebrush	ARLU	Artemisia ludoviciana	0–20	0–1
Shrub/Vine
3	Shrubs and Half-Shrubs			100–270
	western sandcherry	PRPUB	Prunus pumila var. besseyi	60–95	3–15
	Shrub, other	2S	Shrub, other	20–60	1–10
	spreading buckwheat	EREF	Eriogonum effusum	20–40	1–5
	soapweed yucca	YUGL	Yucca glauca	0–20	0–1
	plains pricklypear	OPPO	Opuntia polyacantha	0–20	0–1
	prairie rose	ROAR3	Rosa arkansana	0–20	0–1
	prairie sagewort	ARFR4	Artemisia frigida	0–20	0–1

Interpretations

Animal community

GRAZING INTERPRETATIONS:
This site provides excellent spring and summer forage for cattle, horses, sheep, antelope, deer, and small mammals.

The animal forage preference changes as the growing season progresses. This coupled with the fact that this site has a good complement of cool- and warm-season plants, make it important that planned deferment and rotation be scheduled.

Cool-season plants are very nutritious during the early spring. It is therefore necessary to periodically defer grazing in the spring so that these grasses are not grazed out and replaced by less desirable species. Warm-season plants benefit by deferment from grazing during the late spring and early summer months.

Vegetative palatability influences proper use considerations. The season of use, species of grazing animal, past grazing use, and plant composition directly influence animal preference and performance.

Guide to Initial Stocking Rates:
Stocking rates given below are based on continuous use for the entire growing season and are intended only as an initial guide. However, continuous grazing is not recommended. Forage needs are calculated based on 912.5 pounds of ingested air-dry forage per animal unit month (AUM). Useable production is based on total annual production in a normal year with a harvest efficiency of 25 percent.

Plant Community (PC) Production (lbs./acre) and Suggested Initial Stocking Rate (AUM/acre)

1.1 community - (1500) (0.41)

1.3 community - (1200 ) (0.33 )

2.1 community - (800 ) (0.22 )

Adjustments to the initial stocking rates should be made as needed to obtain proper use. A field inventory must be conducted before establishing a grazing plan and assigning stocking rates.

WILDLIFE INTERPRETATIONS:
This site provides habitat for pronghorn, deer, cottontail, jackrabbit, small mammals, non-gamebirds, quail, and doves.

This site has a high value for wildlife because of the excellent habitat produced. This is due to the amount of cover and protection afforded by the taller grasses, and the abundance of forbs produced. If range condition declines from overgrazing with cattle, pronghorn, and mule deer numbers are reduced due to lack of quality forage. Other small mammals, quail, and cottontail also decline in numbers.

Hydrological functions

Soils in this site are grouped into "A" and "B" hydrologic groups. Field investigations are needed to determine hydrologic cover conditions and hydrologic curve numbers.

Recreational uses

This site has good to excellent aesthetic appeal and natural beauty due to the numerous forbs and shrubs that bloom from spring to early summer. The recreation provided through hunting, hiking, photography, bird watching, and other opportunities is of high value on this site.

Wood products

Wood products are extremely limited on this site.

Other products

This site has limited potentials for other products.

Supporting information

Inventory data references

A minimum of 20 low or medium intensity observations are required to meet verification level status. This ESD has NRI and 417 data that meet these minimums. Individual observations are listed in EDIT and are viewable behind the login. A corresponding tracking sheet is available in the MLRA office that links the list to the actual observations used in the analysis.

53 Confidential NRI-GL on-site data points collected in Arapahoe, Douglas, Elbert, El Paso, Fremont, Huerfano, and Pueblo counties in Colorado in this ESD from 2003 to 2020 were reviewed in 2024 and accepted by Doug Whisenhunt.

Five 417 field data observations from 1968 to 1970 collected in El Paso and Elbert counties were analyzed in 2024 by Doug Whisenhunt.

References

Anderson, R.C. 1982. An evolutionary model summarizing the roles of fire, climate, and grazing animals in the origin and maintenance of grasslands. Pages 297–308 in , , and , editors. Grasses and grasslands: systematics and ecology.
Cleland, D.T., J.A. Freeouf, J.E. Keys, G.J. Nowacki, C. Carpenter, and W.H. McNab. 2007. Ecological Subregions: Sections and Subsections of the Coterminous United States. USDA Forest Service, General Technical Report WO-76. Washington, DC. 1–92.
Fenneman, N.M. 1917. Physiographic Subdivision of the United States. Proceedings of the National Academy of Sciences 3:17–22.
Guyette, R.P., M.C. Stambaugh, D.C. Dey, and R. Muzika. 2012. Predicting Fire Frequency with Chemistry and Climate. Ecosystems 15:322–335.
United States Department of Agriculture, . 2022. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin.

Contributors

Ben P. Berlinger
Revised by Doug Whisenhunt

Approval

Kirt Walstad, 4/07/2025

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)	Ben Berlinger Daniel Nosal
Contact for lead author	Ben.Berlinger@co.usda.gov
Date	11/29/2018
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:
Typically none, if present short and disconnected.
Number and height of erosional pedestals or terracettes:
Pedestalled plants caused by wind erosion, if present, are few.
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Three (3) percent or less bare ground. Bare patches range from two to four inches in diameter. Prolonged drought or fire cause bare ground to increase to three to seven percent with bare patches ranging from seven to 10 inches in diameter.
Number of gullies and erosion associated with gullies:
None.
Extent of wind scoured, blowouts and/or depositional areas:
None. A minor amount of wind scouring is evident on disturbed areas with minor deposition adjacent to the disturbed area. Fire or extended drought exacerbates the appearance.
Amount of litter movement (describe size and distance expected to travel):
Litter is uniformly distributed with none to slight movement. On steep slopes or knolls, litter moves from a few inches to one foot depending on the intensity of wind and rainfall events.
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Average Soil Stability Class rating is anticipated to be four or five in the plant interspaces at the soil surface. The soil surface is stabilized by decomposing organic matter.
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Modal soils have A horizon ranges from six to 10 inches in depth. The A horizon color is typically grayish brown (10YR 5/2), with sandy loam texture. Soil surface structure is moderate fine granular.
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Cover from sod forming grasses, bunchgrasses, forbs, and shrubs reduce bare ground. Raindrop impact is reduced as well as overland flow, providing increased time for infiltration to occur. Dense stands of blue grama can limit infiltration due to high root densities. Extended drought may reduce short and mid-statured bunchgrass basal cover resulting in decreased infiltration and increased runoff following intense storms.
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
No compaction layer present.
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 tall bunchgrass

Sub-dominant:
Warm-season tall rhizomatous grass>warm-season mid- bunchgrass>cool season mid- bunchgrass/grasslikes>warm-season short bunchgrass >shrubs = forbs

Other:
leguminous forbs

Additional:
Biological Crust: Trace (based on cover not composition by weight)
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Typically minimal. Expect slightly more bunchgrass mortality during and following drought. Lack of disturbance increases occurrence of decadence.
Average percent litter cover (%) and depth ( in):
Litter cover averages 30 to 45 percent at 0.25 to 0.50 inch depth. Litter cover during and following drought ranges from 20 to 30 percent and five to 15 percent following wildfire.
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
1,000 lbs./ac. during low precipitation years; 1,900 lbs./ac. during average precipitation years; 2,700 lbs./ac. during high precipitation years. After extended drought or the first growing season following wildfire, production may be significantly reduced by 200 to 500 pounds per acre or more.
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 1.1 plant community. Annuals may temporarily occupy the site following extended fire or drought if 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.