Physiographic features

This site occurs on nearly level lava plains, terraces, and benchlands, and on rolling and somewhat broken foothills. Slopes range from 1 to 30 percent. Small lava rock outcrop areas may be scattered throughout the site. Elevations range from 4000 to 5500 feet (1200-1680 meters). It occurs on all aspects.

Table 2. Representative physiographic features

Climatic features

The Upper Snake River Plain, MLRA 11B, is part of the Northwestern Wheat and range Region. It has a mean elevation of 4841 feet above sea level, and varies from 4177 to 4841 feet. In general, it is a geologically young, level to gently sloping lava plateau. In places larger streams have cut deep, steep-walled canyons. The average annual precipitation, based on 10 long term climate stations located throughout the MLRA, is 10.88 inches. The averaged low is 8.74 inches and the maximum average is 12.69. Monthly precipitation usually peaks in May, then drop off rapidly to reach its low in July and August. The climate station at Aberdeen Experiment Station (1000010) has records of zero precipitation in 11 months of the year, and as low as 0.03 inches in December, the lone non-zero month.
Temperatures can be extremely variable across the year. Highs of up to 104° and lows down to -42° Fahrenheit have been recorded. The average annual temperature from ten climate stations is 44.75° F. The frost-free period ranges from 91 to 115 days. The freeze-free period can last from 123 to 146 days.
Both morning and afternoon average relative humidity values reach their low in August, and are far below the national average. Wind speed peaks in the Spring, and is generally somewhat above the national average. The average number of sunny, cloud-free days is above average for the summer months, but below average for the period from November through February. The average total snowfall is approximately 29 inches.

Table 3. Representative climatic features

Influencing water features

This site is not influenced by adjacent wetlands, streams or run on.

Soil features

Soils of light colored loams, silt loams, fine sandy loams over 20 inches deep. They may be gravelly or stony but not in sufficient amounts to limit production. Subsoils are medium textured and have a lime accumulation at depths of 7-18 inches. Substratum may be sand, gravel, basalt or hardpan. Organic matter content is low, permeability moderate, and available water holding capacity (AWC) about 2 inches per foot of effective depth. Erosion hazard is moderate, especially when plant cover is scarce or lacking. Lime may be present within 7 inches of the surface. These soils have an aridic moisture regime and a mesic or frigid temperature regime.

Table 4. Representative soil features

Animal community

Wildlife Interpretations.
Animal Community – Wildlife Interpretations

This rangeland ecological site provides diverse habitat for many native wildlife species. Large herbivore use of this ecological site is by mule deer, pronghorn antelope, and elk. Important seasonal habitat is provided for resident and migratory animals including western toad, sagebrush lizard, western rattlesnake, shrews, bats, jackrabbits, ground squirrels, mice, coyote, red fox, badger, sage-grouse, Ferruginous hawk, prairie falcon, horned lark, and western meadowlark. Area sensitive species include pygmy rabbit, burrowing owl, great basin ground squirrel, and Townsend pocket gopher. Changes in the plant community composition can reduce the number and diversity of wildlife species in the area. With reduced shrub cover, shrub obligate avian and mammal species become rare including sage-grouse, brewer’s sparrow, sage sparrow, sage thrasher, and pygmy rabbits. Encroachment of noxious and invasive plant species (cheatgrass, Rush skeleton weed, and knapweed) can replace native plant species which provide critical feed, brood-rearing, and nesting cover for a variety of native wildlife. Water features are sparse provided by seasonal streams, artificial water catchments, and springs. This rangeland ecological site is commonly associated with pre-historic lava flows which provide unique cave habitats for several sensitive animal species, including the Blind Cave Leiodid Beetle, Cave Obligate Mite, Bats, and the Cave Obligate Harvestman.


State 1 Phase 1.1 - Wyoming Big Sagebrush/ Bluebunch Wheatgrass/ Thurber’s Needlegrass Reference Plant Community (RPC): This plant community provides a diversity of grasses, forbs, and shrubs, used by native insect communities that assist in pollination. The reptile and amphibian community is represented by leopard lizard, short horned lizard, sagebrush lizard, western skink, western rattlesnake, western toad, boreal chorus frog, and northern leopard frog. Amphibians are associated with springs and isolated water bodies adjacent to this plant community. Spring developments that capture all available water would preclude the use of these sites by amphibians. Shrub-steppe obligate avian species include the Brewer’s sparrow, sage sparrow, sage thrasher, and sage- grouse. Critical habitat (lek sites, nesting areas, winter cover and food) for sage-grouse is provided by this diverse plant community. The plant community supports seasonal (spring through early winter) needs of large mammals (mule deer, antelope, and elk), with Wyoming big sagebrushproviding food and cover. A diverse small mammal population including golden-mantled ground squirrels, chipmunks, yellow-bellied marmots, and pygmy rabbits would utilize this plant community.

State 1 Phase 1.2 - Wyoming Big Sagebrush/ Sandberg Bluegrass/ Bottlebrush Squirreltail Plant Community: This plant community is the result of improper grazing management. An increase in canopy cover of sagebrush contributes to a sparse herbaceous understory. An increase in threetip sagebrush may occur leading to a further increase in sagebrush canopy cover. The reduced herbaceous understory results in lower diversity of insects. Diversity of reptiles may decline due to a less diverse prey base. Reduced herbaceous understory is a key factor in limiting the use of this plant community by ground nesting bird species. Shrub-steppe obligate avian species include Brewer’s sparrow, sage sparrow, sage thrasher, and sage-grouse. Habitat (lek sites, nesting areas, winter cover and food) for sage-grouse is limited due to a less diverse herbaceous plant community. A decrease in herbaceous understory and increase in three-tip sagebrush reduces the forage value of the plant community for mule deer, antelope, and elk. Thermal and young of year cover would be provided for large mammals. A diverse small mammal population including golden-mantled ground squirrels, chipmunks, yellow-bellied marmots, and pygmy rabbits would utilize this plant community.

State 1 Phase 1.3 - Bluebunch Wheatgrass/ Sandberg Bluegrass/ Bottlebrush Squirreltail Plant Community: This plant community is the result of frequent fire. The plant community, dominated by herbaceous vegetation with little or no sagebrush provides less vertical structure and limits use by animals dependent on shrub cover. Insect diversity would be reduced but a diverse native forb plant community would still support select pollinators. Reptile use, including short horned lizard, sagebrush lizard and western rattlesnakes would be limited or excluded due to the absence of sagebrush. The dominance of herbaceous vegetation with little sagebrush canopy cover would prevent use of these areas for nesting by Brewer’s sparrow, sage sparrow, sage thrasher, and sage- grouse. This plant community provides limited brood-rearing habitat for sage-grouse if sagebrush cover is adjacent to the site. The site would not provide suitable winter or nesting cover for sage-grouse. The herbaceous vegetation improves habitat for grassland avian species (horned lark and western meadowlark). Large mammal (mule deer, antelope, and elk) use for foraging would be seasonal (spring through fall) but the site would offer little thermal cover and young of year cover. Small mammal diversity would be reduced and the plant community would not provide suitable habitat for pygmy rabbits. This plant community could exhibit an increase in three-tip sagebrush. When the three-tip cover increases a limited amount of cover would be provided for reptiles, birds and large mammals listed above.

State 2 - Sandberg Bluegrass/ Cheatgrass and Annual Plant Community: This plant community is the result of continued improper grazing management and/or frequent fire. The loss of the native shrub and herbaceous plant community would not support a diverse insect community. The reduced forb component in the plant community would support a very limited population of pollinators. Most native reptilian species are not supported with food, water, or cover. This plant community does not support the habitat requirements for sage-grouse, sage thrasher, Brewer’s sparrow, or sage sparrow. Diversity of grassland avian species is reduced due to poor cover and food. Birds of prey including hawks and falcons may range throughout these areas looking for prey species. Large mammals may utilize the herbaceous vegetation in the early part of the year when the invasive annuals (cheatgrass) are more palatable. At other times of the year large mammals would not regularly utilize these areas due to poor food and cover conditions. The populations of small mammals would be dominated by grassland species like the Columbian ground squirrel. This plant community could exhibit an increase in three-tip sagebrush. When the three-tip cover increases a limited amount of cover would be provided for reptiles, birds, and large mammals listed above.

State 3 - Range Seeding Plant Community: The seeding mixture (native or non-native) determines the animal species that utilize this site. A diverse seed mixture of grasses and forbs would provide similar habitat conditions as in the plant community described in State 1 phase 1.3. A diverse seed mixture of grasses, forbs and shrubs would provide similar habitat conditions as described in State 1 phase 1.1 or 1.2. A monoculture of non-native grass species would not support diverse populations of insects, reptiles, avians, mammals, or sagebrush obligate species. Grassland animal species including western meadowlark, horned lark, savannah sparrow, deer mouse, kangaroo rat, and elk would utilize this site for nesting and/or foraging. Birds of prey including hawks and falcons may range throughout this community looking for prey species.

Grazing Interpretations:

There are few limitations to grazing. The site is suited for grazing in the spring, early summer, and fall for livestock. The distance to water may be a problem in some areas and water developments may be necessary. Water hauling is also an option. This site is often the key area in a management program.
Estimated initial stocking rate will be determined with the landowner or decision-maker. They will be based on the inventory which includes species, composition, similarity index, production, past use history, season of use and seasonal preference.

Hydrological functions

The hydrologic condition of rangelands is the result of complex interrelationships of soil, vegetation, topography and climate. The hydrology of this site is characterized by low intensity frontal storms from October through April, and occasional high intensity thunderstorms during summer. Approximately 50 percent comes during the plant growing season, with May and June as the wettest months. About 25 to 35 percent of the precipitation falls as snow, and snow depth especially at lower elevations is not sufficient to insulate the soils from freezing. Soil frost influences runoff and infiltration, and freezing and thawing cycles can maintain a saturated soil condition which leads to breakdown of soil aggregates. Wyoming big sagebrush sites at elevations ranging from 4,000 to 5,500 feet on these loamy sites typically generate little runoff. Macropore flow is an important process on this site, where water flows in interspace “channels” or low areas, and is intercepted by shrub coppices with higher infiltration rates. Runoff averages less than 2% of the annual water budget. Ponding and flooding generally do not occur on this site. Run-on from adjacent sites normally does not occur.

State 1, Community Phase 1.1
In HCPC, especially on less steep slopes, the majority of rainfall and snowmelt infiltrates into the soil profile and the erosion potential is very low. Shrub canopy zones (coppices) generally have higher rates of infiltration than shrub interspaces because of differences in soil morphology, organic matter and surface litter cover. Moss and lichens dominate most coppices as ground cover. Interspaces between shrubs are either bare or partially covered with rock or litter. Moss in the sagebrush understory is a good indicator of proper hydrologic function. Dominance of bluebunch wheatgrass in the understory is also an indicator of good hydrologic condition. When soil surface condition is dry, and undecomposed litter biomass accumulates, water repellency can develop on lighter textured soils. Little runoff occurs from this site at lower slopes. When runoff does occur, modeling indicates it is typically in late spring and is associated with snowmelt or rainfall on frozen soils. Occasional large thunderstorms will generate runoff in summer. Potential for runoff increases as aerial cover and microtopography decrease. Higher runoff volumes are positively correlated with increasing bare ground and steepness of slope, and may occur on sites with these characteristics. Typically, very little sediment is delivered off-site. When sediment loss does occur, it is usually in late winter when soil aggregate stability is lowest, or in summer when dry conditions increase repellency. Rill erosion is the dominant process on steeper sites, but sediment is usually deposited on lower slopes and does not reach area streams. Deep percolation (<1% of water budget) does not generally occur on these low precipitation sites, especially where soils are deeper or underlain by bedrock. . Good grazing management that addresses frequency, duration, and intensity of grazing can keep fine fuels from developing, maintain normal levels of litter, and promote the production and vigor of existing native bunchgrasses. Trampling and overgrazing can result in rapid and possibly permanent loss of the cryptogam cover, which can increase the potential for wind erosion, and open crusts are a microenvironment for the establishment of winter annual aliens.

State 1, Community Phase 1.2
Increasing sagebrush density and cover, due to the lack of fire or improper grazing management, is associated with a change in hydrologic function. Increasing water repellency and subsequently higher runoff rates are associated with litter buildup in decadent Wyoming big sagebrush coppice microsites. Repellency typically increases during dry conditions, so that runoff and erosion are more likely to occur from smaller and/or less intense storm events. Studies show increasing cover of sagebrush is typically correlated with greater sediment/runoff ratios when runoff does occur. The loss of vigorous deep-rooted bunchgrasses in conjunction with invading annual grasses will typically increase the seasonal variability of infiltration and runoff as compared to HCPC. Dominance of Sandberg bluegrass in the understory is also correlated with higher runoff rates. The presence of increased shrub cover, including taller shrubs, increases the chance of interception loss. Chemical brush management should have minimal impact on sagebrush hydrology if other factors remain undisturbed (coppice characteristics remain intact, with little impact on litter cover), and will invigorate native bunchgrasses if managed properly. Prescribed burns are best used to create mosaics on these Wyoming big sage brush sites, where it may take 20 to 40 years for recovery following fire, regardless of intensity. Disturbance increases the risk of invasion by annuals, which could alter hydrologic function over time.

State 1, Community Phase 1.3
Fire can reduce infiltration and increase runoff and erosion causing reduced site productivity and contributing to water quality impacts in the short term. Runoff can be generated more quickly and in greater volume after fire, leading to erosion and flooding concerns. Fire reduces random roughness and significantly reduces plant cover, litter biomass, and organic matter in the soil surface. Burning also reduces macrofauna populations that contribute to increased aggregate stability through secreted compounds and fungal hyphae production. Where litter cover remains intact, fire impacts are reduced. The effects of fire on the risk of runoff and erosion will be significant on steeper sites until ground and canopy cover recover. Amount of runoff and erosion will depend on the weather pattern during the recovery period. After fire, water repellency often occurs on the soil surface, with burned coppices being most impacted. Mosaic burn patterns on a pre-fire HCPC site will somewhat mitigate erosion and runoff effects. Repellency is typically gone after two to three seasons following fire, and hydrologic function improves significantly as vegetation cover increases. Recovered sites with bluebunch wheatgrass dominating the understory have good hydrologic function. Gradual increases in Wyoming big sagebrush along with fine fuels management will reduce fire frequency over time. These sites typically take 20 to 40 years for sagebrush canopy to regain pre-fire cover levels.


State 2
Litter cover can be reduced by 50% and bare ground can increase to over 70% immediately following fire. Repeated fires significantly reduce site productivity. Dominance of annual grass and forbs is typical, and is associated with unstable hydrologic conditions. Due to diffuse basal characteristics, annual grasses generally do not have the capacity to catch and hold sediment like bunchgrass clumps. There is no shrub cover and little understory to mitigate the impact of rainfall on soil, which leads to increased soil detachment and availability for transport. While rock cover, when present, may reduce detachment, it reduces infiltration and speeds delivery and transport of sediment. Wyoming big sagebrush sites often have higher erodibility than other sagebrush sites, and have the potential to produce significant amounts of sediment loss during larger storm events. This is correlated with less litter, grass cover, and more bareground on these frequently burned sites. In heavy stands of cheatgrass and other annual species, runoff potential is reduced during spring and early summer. However, these sites will demonstrate significant variability in infiltration and runoff due to seasonal changes in cover. Fire risk can be high, especially when conditions are dry. More frequent fires result in increased bare ground conditions which are highly susceptible to water and wind erosion. Repeated cycles of annual grass regeneration and repeated fire can result in severe depletion of the surface soil horizon and organic matter. Reductions in organic matter lead to reduced aggregate stability, reducing infiltration and plant available water, and increasing the risks of runoff and soil loss. Reduced cover and reduced random roughness due to repeated burns provide interconnected flow paths for runoff and associated erosion. Snow accumulation may be reduced since there are insufficient shrubs to prevent drifting, and earlier meltoff is probable without shrub cover. Sediment yields increase as rill processes become dominant, even on lower slopes. With improper grazing management, trail areas become compacted, leading to further rilling and gully creation.


State 3
Seeding is not likely to reduce runoff or erosion in the year following a burn. Seeding of native or desired species, if successful, will help stabilize the erosion process and improve hydrologic conditions over time. As sagebrush and other shrubs establish, hydrologic function of this state will approach HCPC if significant soil loss has not occurred prior to seeding. Where shrubs successfully establish or increase naturally into the seeding, the site will be less prone to freeze-thaw processes and some snow will accumulate during winter storms. Seeding and restoration of the site will be dependent on how far the site productivity and hydrologic condition has diminished before management.

Recreational uses

This site has very little recreational value except for off-road vehicle use. It has some spring blooming flowers which offer slight aesthetic value and some photographic opportunities. It has some value for hunting of antelope, coyotes, and rabbits. The site has very little value for picnicking or camping. It has little aesthetic appeal or natural beauty except where it is adjacent to lava flows.

Wood products

None

Other products

None

Inventory data references

Information presented here has been derived from NRCS clipping and other inventory data. Also, field knowledge of range-trained personnel was used. Those involved in developing this site description include:
Dave Franzen, co-owner, Intermountain Rangeland Consultants, LLC
Jacy Gibbs, co-owner, Intermountain Rangeland Consultants, LLC
Jim Cornwell, Range Management Specialist, IASCD
Leah Juarros, Resource Soil Scientist, NRCS, Idaho
Joe May, State Rangeland Management Specialist, NRCS, Idaho
Lee Brooks, Range Management Specialist, IASCD

Type locality

Other references

Hironaka, M., M.A. Fosberg, A. H. Winward. 1983. Sagebrush- Grass Habitat Types of Southern Idaho. University of Idaho. Moscow, Idaho. Bulletin Number 35

USDA Forest Service, Rocky Mountain Research Station. 2004. Restoring Western Ranges and Wildlands. General Technical Report RMRS-GTR-136-vols. 1-3.

USDA, NRCS.2001. The PLANTS Database, Version 3.1 (http://plants.usda.gov.). National Plant Data Center, Baton Rouge, LA 70874-4490 USA
USDA, Forest Service, Fire Effects Information Database. 2004. www.fs.fed.us/database/feis

USDI Bureau of Land Management, US Geological Survey; USDA Natural Resources Conservation Service, Agricultural Research Service; Interpreting Indicators of Rangeland Health. Technical Reference 1734-6; version 4-2005.

Contributors

Dave Franzen
DLF

Approval

Kirt Walstad, 5/14/2024