Physiographic features

This site is in high mountainous country where physical and climatological conditions are extremely severe. Various phases of geological erosion are pronounced. Blowing soil particles and snow-blast injure plants; very high intensity sunlight prevails. This site is on slopes from 10 to 60 percent and has a southerly exposure. Elevation ranges from about 11,500 to 13,000 feet.

Table 2. Representative physiographic features

Climatic features

The climate is harsh and cold. Due to the elevation, summers are wet and short. The plant growth period is less than 60 days. The average annual precipitation ranges from 30 to 50 inches. Of this, approximately 80-90% falls as snow, and 10-20% falls as rain between middle of June to and the middle of September 1. Summer moisture is mostly from thundershowers in July, and August. The driest period is usually from May to June; and June is normally the driest month. The average annual total snowfall is 435 inches. The snow depth usually ranges from 16 to 67 inches during November thru May. The highest winter snowfall record in this area is 807 inches which occurred in 1978-1979. The lowest snowfall record is 205 inches during the 1995-1996 winter. The frost-free period typically ranges from 54 to 96 days. The last spring frost is the middle of June to the end of June. The first fall frost is the last week of August to the middle of September. Mean daily annual air temperature is about 21.5ºF to 45.9ºF, averaging about 21.5ºF for the winter and 54.4ºF in the summer. Summer high temperatures of mid-70ºF to 80ºF are not unusual. The coldest winter temperature recorded was -40ºF on February 5, 1982 and the warmest winter temperature recorded was 63ºF on February 20, 1958. The coldest summer temperature recorded was 9ºF on June 26, 1969 and the warmest was 80 ºF on July 6, 1989. The hottest day on record is 81ºF on September 14, 1990. Wide yearly and seasonal fluctuations are common for this climatic zone. Data taken from Western Regional Climate Center (2018) for Wolf Creek Pass 1 E, Colorado Climate Station. There are only 2 climate stations in the zone in the state of Colorado. Wolf Creek Pass 1 E and Wolf Creek Pass 4 W; they are at the lower precipitation end of this zone.

The grasses generally start growth in late June. Generally forbs start their growth about June 15, while the shrub species start growth at the end of June. Plant growth usually stops in September. The optimum growth period is generally between July and September for most of these plants. c. The average annual temperature is 26 to 34ºF. Frost can occur any day of the year during the growing season. Plant growth is seldom hampered by moisture stress but strong winds can induce drought-like conditions. Wind velocities for the area average 5 to 25 miles per hour. Strong winds during the winter and spring create snow cornices.

Table 3. Representative climatic features

Climate stations used

• (1) WOLF CREEK PASS 1 E [USC00059181], Creede, CO

Influencing water features

None

Soil features

The soils in this site are shallow to deep, well drained soils that formed in slope alluvium and colluvium from volcanic and sedimentary rocks. Typically the surface is loam or very gravelly loam. Permeability of the soil is moderate. Available water capacity is low to very low. Effective rooting depth is 20 inches or more. Runoff is medium to high, and the hazard of water erosion is moderate to high. Content of rock fragments is 35 t percent or greater in the soil profile.

Soil Series associated with this site:

Henson and Whitecross.

Table 4. Representative soil features

Animal community

This site provides excellent summer and fall forage for domestic sheep, bighorn sheep, and elk. The animal forage preference generally changes as the season progresses into summer and fall. The dominant grasses, Thurber fescue, alpine fescue, alpine bluegrass, and artic bluegrass, are desirable the entire grazing season along with the excellent variety of forbs which this site provides.

Since sheep grazing occurs during the time of flowering and seed setting, a heavily grazed range may be marked by a scarcity of alpine forbs especially the upright and relatively succulent species. Grasses, because of their higher palatability at this elevation, also may be thinned out. On such a range various alpine sedges and less palatable grasses are frequently the dominant vegetation. However, the natural succession is toward Thurber fescue, alpine bluegrass, artic bluegrass, and alpine fescue.

The date when alpine ranges are ready to graze varies with elevation, exposure, and seasonal climatic conditions. Generally speaking most of these ranges should not be grazed before July 15 except for minor local areas in the subalpine area. In some places where snowbanks are prevalent, grazing may need to be deferred until as late as August 15. Grazing should not begin until the major feed areas are firm and free from excessive snowmelt water. Flower heads on alpine fescue, alpine bluegrass, and artic bluegrass should be well developed.

Grazing after September 15 is hazardous because of the suddenness of fall storms. Because of these conditions, sheep allotments should be so designed that they will have one or more camps in suitable areas below timberline for grazing before July 15 and after September 1. If this is not feasible, the grazing season should be adjusted accordingly.

Areas of any size containing patches of forage on very steep slopes and on developing soil on talus slopes should not be included in the estimate of grazing capacity. The damage resulting from trailing to and from such areas and along excessively steep slopes is not commensurate with the value of the forage. This point cannot be overemphasized.

Generally alpine areas suitable for sheep grazing should represent more or less continuous or connected areas of forage sufficient for a band of 600 to 1000 ewes with lambs for the prevailing season, including low range in the allotment. Because feed areas are often small and discontinuous, small bands are usually best. Permanent sheep allotments should be considered only where prevailing slopes are generally moderate.

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 month (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 Percent Climax
Class Vegetation AUM/Ac Ac/AUM
Excellent 76-100 1.10 .9
Good 51-75 .83 1.2
Fair 26-50 .55 1.8
Poor 0-25 .27 3.7

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 herbivores, inaccessibility, dormant season use, presence of introduced species, etc., stocking rate adjustments will be required.

Annual Production:
If the range is in excellent condition, the approximate total annual production (air-dry) ranges are:
Favorable Years 3200 lb/Ac
Normal Years 2800 lb/Ac
Unfavorable Years 2500 lb/Ac

Of this production, 10-15 percent will likely be unpalatable or out of reach of grazing animals.

Native Animal Community Associated with the Potential Plant Community:
This site is part of the normal habitat for Rocky Mountain goats and ptarmigan. Elk and bighorn sheep remain year round in some areas. More frequently these animals along with deer remain in this area only during the summer. Snowshoe rabbits, blue grouse, pica, songbirds, and other animals depend on this site for their needs for at least part of the year.

Wildlife Values:
As forage quality declines from overuse and excessive trailing, big game animals such as elk, deer, bighorn sheep, and Rocky Mountain goats are the most affected species. Poor nutrition will result in declines of Rocky Mountain goats and bighorn sheep. Elk and deer will move to other accessible forage if available in the vicinity. Ptarmigan, blue grouse, and snowshoe rabbits will also decline in numbers as range conditions deteriorates. Pica, songbirds, and small mammals are the least affected by a reduction of the potential plant community.

Hydrological functions

Soils in this site are grouped into the “B” hydrologic group, 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 NRCS National Engineering Handbook, Section 4, and Peak Flows in Colorado Handbook for more information.

Recreational uses

Recreation and Natural Beauty:
In the field of recreation, the alpine type has appeal and is a source of inspiration to many people through its attractions as an area for mountain climbing, photography, pack trips, and fishing in high elevation lakes. Overgrazing and other uses that destroy the vegetation will impinge on recreational values including use of alpine flower fields, strategic pastures for horse feed, and denudation of camp sites and lake shoes. Hunting for ptarmigan and snowshoe rabbits is generally good to excellent on this site.

Wood products

No potential production on this range site.

Other information

Major Poisonous Plants to Livestock:
No poisonous plants are present on this site when vegetation is at or near its potential.

Endangered Plants and Animals:
No endangered or threatened species have been identified. Species names to be included as reliable information becomes available.

This range site occurs in the Alamosa, Archuleta, Boulder, Chaffee, Clear Creek, Conejos, Costilla, Custer, Delta, Delores, Eagle, El Paso, Fremont, Garfield, Gilpin, Grand, Gunnison, Hinsdale, Huerfano, Jackson, Lake, La Plata, Larimer, Mesa, Mineral, Montrose, Ouray, Park, Pitkin, Pueblo, Rio Blanco, Rio Grande, Routt, Saguache, San Juan, San Miguel, Summit, and Teller Counties.

Type locality

Other references

References
Chapman, S.S., G.E. Griffith, J.M. Omernik, A.B. Price, J. Freeouf, and D.L. Schrupp. 2006. Ecoregions of Colorado. (2-sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, VA. Scale 1:1,200,000.

Cleland, D.T.; Freeouf, J.A.; Keys, J.E.; Nowacki, G.J.; Carpenter, C.A.; and McNab, W.H. 2007. Ecological Subregions: Sections and Subsections for the conterminous United States. Gen. Tech. Report WO-76D [Map on CD-ROM] (A.M. Sloan, cartographer). Washington, DC: U.S. Department of Agriculture, Forest Service, presentation scale 1:3,500,000; colored.

Soil Conservation Service (SCS). May 1987. Range Site Description for Warm Alpine #309. : USDA, Denver Colorado.

United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.

Western Regional Climate Center. Retrieved from http://www.wrcc.dri.edu/summary/Climsmco.html on December 10, 2018

Contributors

Suzanne Mayne-Kinney

Approval

Kirt Walstad, 3/05/2024

Acknowledgments

Project Staff:
Suzanne Mayne-Kinney, Ecological Site Specialist, NRCS MLRA, Grand Junction SSO
Chuck Peacock, MLRA Soil Survey Leader, NRCS MLRA Grand Junction SSO

Program Support:
Rachel Murph, NRCS CO State Rangeland Management Specialist, Denver
Scott Woodhall, NRCS MLRA Ecological Site Specialist-QA Phoenix, AZ
Eva Muller, Regional Director, Rocky Mountain Regional Soil Survey Office, Bozeman, MT
B.J. Shoup, CO State Soil Scientist, Denver
Eugene Backhaus, CO State Resource Conservationist, Denver

Those involved in developing earlier versions of this site description include: Bob Rayer, retired NRCS Soil Scientist; Herman Garcia, retired CO State RMS and NRCS MLRA Ecological Site Specialist-QA Phoenix, AZ.

--Site Development and Testing Plan--:

Future work to validate and further refine the information in this Provisional Ecological Site Description is necessary. This will include field activities to collect low-, medium-, and high-intensity sampling, soil correlations, and analysis of that data.

Additional information and data is required to refine the Plant Production and Annual Production tables for this ecological site. The extent of MLRA 48A must be further investigated.

Field testing of the information contained in this Provisional ESD is required. As this ESD is moved to the Approved ESD level, reviews from the technical team, quality control, quality assurance, and peers will be conducted.