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Ecological site R035XY413CO

Alkali Bottom

Accessed: 05/30/2026

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General information

Draft. A draft ecological site description is either incomplete or has not undergone quality control and quality assurance review.

Table 1. Dominant plant species

Tree	Not specified
Shrub	Not specified
Herbaceous	Not specified

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Physiographic features

1. Elevation: Low: 5000 ft High: 6200 ft
2. Aspect: all
3. Percent slope: Low 0% High 6%
4. The landscape consists primarily of steep canyon terrain with gently sloping valley floors frequently dominated by shrubs. Intermittent and perenial streams frequently are deeply incised in the valley floor.

Table 2. Representative physiographic features

Landforms	(1) Canyon
Elevation	5000 – 6000 ft
Slope	0 – 6 %
Aspect	Aspect is not a significant factor

Climatic features

a. Hard freeze period: 175 to 205 days (24 degrees F)
b. Freeze-free period: 150 to 180 days (28 degrees F)
c. Frost-free period: 125 to 155 days (32 degrees F)
d. Mean annual precipitation: 9 to 16 in
e. Mean annual air temperature: 46 to 56 degrees F
f. Mean annual soil temperature: 49 to 58 degrees F

Table 3 Representative climatic features

Frost-free period (average)	160 days
Freeze-free period (average)	180 days
Precipitation total (average)	20 in

Bar

Line

Figure 1. Monthly precipitation range

Bar

Line

Figure 2. Monthly average minimum and maximum temperature

Soil features

Characteristic soils in this site are deep and well drained located on terraces, drainage ways, and alluvial valley floors. They formed in alluvium materials derived mainly from shale and sandstone. Soils are moderately to strongly alkaline. Surface texture is sandy loam, clay loam, or silty clay loam. Subsurface texture is silty clay loam to 60 inches. Permeability is slow. The erosion hazard is high with these soils subject to severe gullying.

List of Soil Taxonomic Units or Soil Mapping Units for all soils included in this site:

Lillings silty clay loam 0-6% slope
Youngston silt loam 1-3% slope
Youngston silty clay loam 3-6% slope
Recapture sandy loam 0-6% slope
Binton clay loam 0-3% slope
Sili silty clay loam 0-3% slope

Ecological dynamics

When this range site is near its potential, alkali sacaton, western wheatgrass, sandberg bluegrass, basin wildrye and inland saltgrass make up over 50 percent of the plant community. Alkali sacaton is dominant on this site making up from 20 to 25 percent of the total annual production on the site. Other grasses that occur in the community are sand dropseed, galleta, foxtail barley and a number of sedges and rushes.

Forbs such as scarlet globemallow, sulphur bukcwheat, tufted eveningprimrose, rosy gilia and fileree make up to 10 percent of the potential plant community.

Shrubs such as black greasewood, nuttall saltbush, spiny hopsage, shadscale, fourwing saltbush, prickly pear and basin big sagebrush make up to 25 to 35 percent of the potential plant community. As the plant community declines in condition the grasses and forbs will decrease while the shrubs black greasewood and basin big sagebrush will increase and dominate the site.

Shrubs and trees less than 4 1/2 feet tall 5 to 15% of total.

State and transition model

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Click on state and transition labels to scroll to the respective text

Ecosystem states

1. HCPC

State 1 submodel, plant communities

1.1. HCPC

State 1
HCPC

Community 1.1
HCPC

Total annual production:

Annual production is distributed as follows:
Grasses and Grasslikes 45-65% of total
Forbs 2-10% of total
Shrubs and Half Shrubs 25-35% of total

In excellent condition, the approximate total annual production (air-dry) is as follows:

Favorable 400 to 500 lbs/ac
Average 300 to 350 lbs/ac
Unfavorable 200 to 250 lbs/ac

Of this production 15 to 25 percent will likely be unpalatable or out of reach to grazing animals.

Growth Curves for this site:

Identity/ Jan/ Feb/ Mar/ Apr/ May/ Jun/ Jul/ Aug/ Sep/ Oct/ Nov/ Dec

Excellent/ 0/ 2/ 3/ 5/ 10/ 20/ 25/ 15/ 15/ 2/ 3/ 0
Good/ 0/ 0/ 2/ 3/ 10/ 25/ 30/ 20/ 5/ 2/ 3/ 0
Fair/ 0/ 0/ 2/
/ 10/ 35/ 30/ 15/ 3/ 2/ 0/ 0

Range site degredation:
Overgrazing with cattle will result in alkali sacaton, western wheatgrass, basin wildrye, shadscale, nuttall saltbush and fourwing saltbush disappearing from the plant community. Red threeawn, black greasewood, and basin big sagebrush will increase to the extent that the site will be dominated by shrubby vegetation. Russian thistle will invade and become part of the understory vegetation. The result is decreased forage production with a corresponding increase in runoff and gully erosion.

Overgrazing with sheep results in the same process with basin big sagebrush also being reduced in the potential plant community. Continued severe overgrazing with sheep and or cattle results in black greasewood dominating the site along with the introduced annuals cheatgrass and Russian thistle.

Figure 3. Annual production by plant type (representative values) or group (midpoint values)

Table 4. Ground cover

Tree foliar cover	0%
Shrub/vine/liana foliar cover	30-40%
Grass/grasslike foliar cover	50-70%
Forb foliar cover	10-20%
Non-vascular plants	0%
Biological crusts	0%
Litter	0%
Surface fragments >0.25" and <=3"	0%
Surface fragments >3"	0%
Bedrock	0%
Water	0%
Bare ground	0%

Additional community tables

Table 5. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production ()	Foliar cover (%)
Grass/Grasslike
1	Grasses			110–275
	alkali sacaton	SPAI	Sporobolus airoides	22–69	–
	saltgrass	DISP	Distichlis spicata	17–55	–
	basin wildrye	LECI4	Leymus cinereus	11–41	–
	Sandberg bluegrass	POSE	Poa secunda	6–28	–
	sand dropseed	SPCR	Sporobolus cryptandrus	0–28	–
	squirreltail	ELEL5	Elymus elymoides	0–14	–
	rush	JUNCU	Juncus	0–14	–
	sedge	CAREX	Carex	0–14	–
	western wheatgrass	PASM	Pascopyrum smithii	0–14	–
Forb
2	Forbs			12–30
	sulphur-flower buckwheat	ERUM	Eriogonum umbellatum	0–1	–
	rosy gilia	GISI	Gilia sinuata	0–1	–
	tufted evening primrose	OECA10	Oenothera caespitosa	0–1	–
	scarlet globemallow	SPCO	Sphaeralcea coccinea	0–1	–
Shrub/Vine
3	Shrub			20–50
	greasewood	SAVE4	Sarcobatus vermiculatus	2–10	–
	big sagebrush	ARTR2	Artemisia tridentata	0–3	–
	fourwing saltbush	ATCA2	Atriplex canescens	0–3	–
	shadscale saltbush	ATCO	Atriplex confertifolia	0–3	–
	Gardner's saltbush	ATGA	Atriplex gardneri	0–3	–
	spiny hopsage	GRSP	Grayia spinosa	0–1	–
	plains pricklypear	OPPO	Opuntia polyacantha	0–1	–

Interpretations

Animal community

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. Forage needs are calculated on the basis of 900 lbs of air-dry forage per animal unit montlh (AUM). To maintain proper use and allow for forage that disappears through trampling, small herbivore use, weathering, etc., 35 percent of the palatable forage produced is considered available for grazing by large herbivores.

Condition Class/ Percent Climax Vegetation/ AUM/Ac/ Ac/AUM/ Ac/AU

Excellent/ 76-100/ .15-.16/ 5-6/ 60-75
Good/ 51-75/ .11-.14/ 7-9/ 76-119
Fair/ 26-50/ .06-.1/ 10-19/ 120-239
Poor/ 0-25/ 0-.05/ 20-30/ 240-360

Adjustments to the initial stocking rates should be made as needed to obtain proper use. With specialized grazing systems, large livestock breeds, uncontrolled big game, inacessability, dormant season use, presence of introduced forage species, seeded rangeland etc., stocking rate adjustments will be required.

Willife species list:
pronghorn, muledeer, coyote, deer mouse, blacktailed jackrabbit, desert cottontail, upland game birds, small mammals, song birds, reptiles

Grazing:
When this site is producing near its potential, it provides good grazing for cattle and sheep as well as providing good habitat for many wildlife species. Forage preferences change as the season progresses. Alkali sacaton, western wheatgrass, and basin wildrye are very palatable during the spring and summer grazing period. Nuttall saltbush, fourwing saltbush and shadscale are used primarily during the fall and winter period as the grasses and forbs become dormant and lose their nutritive value. This site responds very well to deferment during the spring and summer seasons. Planned Grazing Systems are an excellent management tool to maintain or improve the vegetation on this site.

Vegetative palatability will influence proper grazing use considerations. The season of use, weather, kind of grazing animal, past grazing history and the plant compostion will directly influence animal preference and performance.

Major Poisonous Plants to Livestock:
Plant Common Name/ Livestock Affected/ Type of Poisoning/ Season Serious

halogeton/ sheep/ may cause abortion/ spring and early summer

Wildlife Values:
This site has good potential for wildlife habitat because of the mixture of grasses, forbs and shrubs that it produces. The site provides habitat at least for part of the year for cottontail rabbit, blacktailed jackrabbit, pronghorn, deer, reptiles, raptors and rodents. As this site hears in potential plant community, the diversity of wildlife species will also increase.

Hydrological functions

Soils in this site are grouped into the "B" and "C" hydrologic groups, as outlined in the Soils of Colorado Loss Factors and Erodibility Hydrologic Groupings 1979 Handbook. Field investigations are needed to determine hydrologic cover conditions and hydrologic curve numbers. Refer to SCS National Engineering Handbook, Section 4, and Peak Flows in Colorado Handbook for more information.

Recreational uses

This site has god aesthetic appeal and natural beauty because of its setting. This site is found primarily in valleys with steep mountainous canyon terrain adjacent to the site.

Wood products

No known potential production

Other information

Typical Locations:
Bridge Canyon, Montezuma County, Colorado

Endangered Plants and Animals:
Currently no known endangered plants or animals are dependent on this site.

Counties in which this Range Site is Located:
La Plata
Montezuma

Rangeland health reference sheet

Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.

Author(s)/participant(s)
Contact for lead author
Date
Approved by
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Presence of water flow patterns:
Number and height of erosional pedestals or terracettes:
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Number of gullies and erosion associated with gullies:
Extent of wind scoured, blowouts and/or depositional areas:
Amount of litter movement (describe size and distance expected to travel):
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):

Dominant:

Sub-dominant:

Other:

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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:
Perennial plant reproductive capability:

Download reference sheet

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