Physiographic features

This site occurs on gently undulating to somewhat rolling and broken foothills. Slopes predominantly range from 8-20 percent, occasionally to 35 percent. Elevation ranges from 4800-7000 feet.

Table 2. Representative physiographic features

Climatic features

MLRA 13, the Eastern Idaho Plateaus, is part of the Northwestern Wheat and Range Region. Its elevation ranges from 4209 to 9331 feet above sea level, with an average elevation of 5787 feet. The average annual precipitation is 16.41 inches, with a range of 13.56 to 18.75 inches, based on ten long term climate stations located throughout the MLRA. A spike in precipitation amount often occurs in late spring, usually in May.
Temperatures vary widely in the MLRA throughout the year. A maximum temperature of 103° Fahrenheit occurred at the McCammon climate station (# 105716; elevation 4770 feet), while a minimum of -41° was recorded at the Kilgore station (#104908). At all stations temperatures throughout the year are usually below the national average. Kilgore also recorded the greatest annual snowfall amount of 217 inches. The average temperature is 41.4 degrees F. with an average high of 55.3 degrees and an average low of 27.5 degrees.
The frost-free period ranges from 64 to 90 days, while the freeze-free period can be 98 to 123 days.

Table 3. Representative climatic features

Influencing water features

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

Soil features

Soils are dark colored, medium textured, moderately deep to deep silt loams, silty clay loams, and clay loams that are moderately high in organic matter with medium to high permeability. These soils have good available water holding capacity (AWC). Coarse fragments may be present but do not significantly affect vegetation. Erosion hazard ranges from slight to severe, depending upon slope and ground cover.

Table 4. Representative soil features

Animal community

Wildlife Interpretations.
Animal Community – Wildlife Interpretations

The rangeland ecological site provides diverse habitat for many native wildlife species. The plant community exhibits a diverse mixture of forbs throughout the growing season offering excellent habitat for invertebrates. Mule deer, pronghorn antelope and elk may utilize the site at different times of the year. The rangeland habitat provides seasonal habitat for resident and migratory animals including western toad, shrews, bats, ground squirrels, mice, coyote, red fox, badger, Ferruginous hawk, prairie falcon. Area sensitive bird species include Brewer’s sparrow, sage thrasher, sage sparrow and sage-grouse. Water features are sparse provided by seasonal runoff, artificial water catchments and springs.

State 1 Phase 1.1 – Mountain Big Sagebrush/ Idaho Fescue/ Bluebunch Wheatgrass Reference Plant Community (RPC): This plant community provides a diversity of grasses, forbs and shrubs, used by native insect communities that assist in pollination. An extensive array of forbs is represented throughout the growing season leading to a diverse insect community. Many avian and mammal species utilize this habitat based on the availability of invertebrate prey species. The reptile and amphibian community is represented by common sagebrush lizard, western rattlesnake, Great Basin spadefoot, western toad and northern leopard frog. Amphibians are associated with springs and isolated water bodies adjacent to this plant community. Development of spring sites that collect all available water would exclude amphibian use on these sites. Native shrub-steppe obligate avian species utilizing the habitat include the Brewer’s sparrow, sage sparrow and sage thrasher. Sage-grouse habitats (leks, nesting, brood-rearing and winter) are provided by this plant community. The plant community provides seasonal food and cover for large mammals including mule deer, pronghorn antelope and elk. A diverse small mammal population including golden-mantled ground squirrels, jackrabbits, deer mice and Great Basin pocket mice utilize this plant community.

State 1 Phase 1.2- Mountain Big Sagebrush/ Utah Juniper/ Sandberg Bluegrass Plant Community: This plant community is the result of improper grazing management and no fire. An increase in canopy of sagebrush and junipers contributes to a sparse herbaceous understory. A reduced herbaceous understory results in less diversity and numbers of insects. The reptile and amphibian community will be similar to State 1 Phase 1.1 community represented by common sagebrush lizard, western rattlesnake, Great Basin spadefoot and western toad. The reduced diversity of insects and loss of understory cover may reduce quality of food and cover for reptile populations. As juniper increases, habitat cover for Brewer’s sparrow, sage thrasher and sage sparrow may increase. Remaining sagebrush provides brood-rearing, winter cover and winter food for sage-grouse but as juniper encroaches the quality of this habitat is severely reduced or eliminated. The plant community supports limited seasonal habitat for mule deer, elk and pronghorn antelope. As juniper encroaches the site will provide additional thermal cover for large mammals. A small mammal population would be similar to State 1, Phase 1.1 animal community.

State 1 Phase 1.3 – Bluebunch Wheatgrass/ Sandberg Bluegrass/ Bottlebrush Squirreltail/ Streambank Wheatgrass Plant Community: The plant community is a result of recent wildfire, prescribed burning or brush management. The plant community, dominated by herbaceous vegetation with little or no sagebrush would provide less vertical structure for animals. Patches of root sprouting shrubs (snowberry and rabbitbrushes) may be present and provide limited vertical structure for wildlife over time. Insect diversity would be reduced but a native forbs plant community similar to State 1 Phase 1.1 would still support select pollinators. Habitat for sagebrush lizard, Great Basin spadefoot and western toad would be limited or excluded due to the loss of sagebrush. Amphibian habitat would be tied to permanent spring sites in the area. Development of spring sites that collected all available water would exclude the use of amphibians on these sites. The dominance of herbaceous vegetation with little sagebrush would limit use of these areas as nesting habitat by Brewer’s sparrow, sage sparrow and sage thrasher. The dominant herbaceous vegetation improves habitat for grassland avian species (horned lark, savannah sparrow, vesper sparrow and western meadowlark). Mule deer and elk use would be seasonal and offer little thermal cover and young of year cover with the loss of shrub cover. The diversity and populations of small mammals would be dominated by open grassland species. Large blocks of this plant community would fragment historic plant community and reduce the quality of habitat for shrub-steppe obligate animal species.

State 1 Phase 1.4 – Mountain Big Sagebrush/ Sandberg Bluegrass/ Bottlebrush Squirreltail Plant Community: This plant community is the result of improper grazing management and no fire. An increase in canopy of sagebrush contributes to a sparse herbaceous understory. Grasses, forbs and shrubs, are used by native insects that assist in pollination but the reduced herbaceous understory results in less diversity of insects. The reptile and amphibian community will be similar to State 1 Phase 1.1 and 1.2 community represented by common sagebrush lizard, western rattlesnake, Great Basin spadefoot and western toad. The reduced diversity of insects may reduce reptile diversity and populations. Reduced herbaceous understory is a key factor in limiting the use of this plant community by avian species. Key shrub-steppe obligate birds include Brewer’s sparrow, sage sparrow, sage thrasher and sage-grouse. Critical habitats (brood-rearing and nesting cover) for sage-grouse are limited due to a less diverse herbaceous plant community. Winter habitat (cover and food) for sage-grouse is provided. The reduced vigor of understory vegetation provides for a shorter forage season for mule deer, elk and pronghorn antelope. Young of year cover would be provided for deer and antelope. Small mammal diversity and populations would be similar to State 1 Phase 1.1.

State 2 – Sandberg/ Annuals Plant Community:
The community has developed due to continued improper grazing management and frequent fire. The plant community does not support a diverse insect community. The reduced forb and shrub component in the plant community would support a very limited population of pollinators. Most reptilian species are not supported with food, water or cover. This plant community does not support the life requisites for sage thrasher, Brewer’s sparrow, sage-grouse or sage sparrow. Diversity of grassland avian species is reduced due to poor cover and available 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 spring and summer when herbaceous vegetation is more palatable. The diversity and populations of small mammals would be dominated by open grassland species. Large blocks of this plant community would fragment historical plant community and reduce the quality of habitat for shrub-steppe obligate animal species.

State 3 - Utah Juniper/ Sandberg Bluegrass/ Annuals Plant Community: This site has developed due to improper grazing management and no fire. The loss of native forbs and understory vegetation will reduce insect diversity on the site. Habitat for sagebrush lizard, Great Basin spadefoot and western toad would be limited due to the loss of brush cover. This plant community does not support life requisites for sage-grouse. Birds using this site as resident or migratory habitat include Juniper titmouse, western bluebird and Virginia’s warbler. The Juniper titmouse relies heavily on juniper seeds for winter food. Hunting success by raptors may decrease due to heavy overstory of juniper. The plant community supports limited seasonal habitat for mule deer and elk in spring and fall. As juniper encroaches the site will provide additional thermal cover for large mammals.

State 4 – Rangeland 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 herbaceous 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, 1.2 or 1.4. A monoculture of non-native grass species would not support diverse populations of insects, reptiles, birds, mammals or sagebrush obligate animal species. Grassland animal species including western meadowlark, horned lark, savannah sparrow, deer mouse, kangaroo rat, mule deer 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. Large areas of State 4 with no shrubs in the plant community would fragment the historical plant community and would severely reduce the quality of habitat for shrub obligate animal species.



Grazing Interpretations.

This site is most suitable for livestock grazing in the spring, early summer, and fall. It is often the key grazing area in a pasture.
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 and early fall. About 50 percent of the precipitation falls as snow, and the site has snow cover during much of the winter. Productive mountain big sagebrush sites at elevations ranging from 4,800 to 7,000 feet generate most runoff from snowmelt. The site is typically protected by vegetation when snowmelt and runoff occur, from mid spring through summer. Shallow subsurface flow to drainages, especially on steeper slopes, is common. Runoff averages about 15% of the annual water budget, but this is quite variable from year to year. Ponding and flooding generally do not occur on this site. Run-on from adjacent sites normally does not occur.


State 1, 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 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 have sufficient aerial and ground cover in HCPC to protect the site from runoff and erosion. Moss in the sagebrush understory is a good indicator of proper hydrologic function. Dominance of bunchgrasses (bluebunch wheatgrass and Idaho fescue) in the stand is also an indicator of good hydrologic condition. When soil surface condition is dry, and undecomposed litter biomass is great, water repellency can develop on lighter textured soils. Modeling indicates that greatest runoff under undisturbed conditions typically occurs during high intensity summer storms, or during late spring or fall from frozen soil or rain-on-snow conditions on lower elevation sites. Erosion rarely exceeds 0.5 ton/acre, and very little sediment is delivered off-site. Higher runoff volumes are positively correlated with increasing bare ground and steepness of slope, but some studies have also shown reduced runoff on steeper slopes due to increased component of subsurface flow. Differences in runoff potential will be dependent on the interaction of site characteristics (soils, slopes, vegetation, aspect, and microtopography). Rill erosion is the dominant process on steeper slopes where erosion is more likely, but sediment is usually deposited on lower slopes and does not reach area streams. Little deep percolation occurs on these deeper soils (5% of water budget), unless there is greater than average winter snow cover. 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, Phase 1.2.
Increasing sagebrush density and cover, along with the establishment of juniper seedlings, is a result of lack of fire or improper grazing management, with proximate seed source of juniper. Increasing water repellency and subsequently higher runoff rates are associated with litter buildup in decadent Mountain 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. Increasing shrub cover, including taller shrubs, may impact snow hydrology. Greater shrub cover increases the chance of interception loss, but may also increase potential snow accumulation and reduce snowmelt rate. The preponderance of small, low intensity events coupled with greater shrub cover reduces the effective precipitation during the growing season, since the interception loss can be a significant proportion (> 30%) of seasonal precipitation. Changes in the hydrology of the site will occur as juniper continues to encroach. Brush management (chemical or prescribed burn) 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 fire treatments can produce desirable results when there is an abundance of natives in the understory.

State 1, Phase 1.3.
Fire can reduce infiltration, subsurface water recharge 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. 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 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 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 sagebrush and bitterbrush, along with fine fuels management, will reduce fire frequency over time.

State 1, Phase 1.4
Increasing sagebrush density and cover is a result of lack of fire or improper grazing management. This state is usually associated with deteriorating hydrologic condition. Increasing water repellency and subsequently higher runoff rates are associated with litter buildup in decadent Mountain 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. Increases in Sandberg bluegrass is correlated with higher runoff rates. Increasing shrub cover, including taller shrubs, may impact snow hydrology. Greater shrub cover increases the chance of interception loss, but may also increase potential snow accumulation and reduce snowmelt rate. The preponderance of small, low intensity events coupled with greater shrub cover reduces the effective precipitation during the growing season, since the interception loss can be a significant proportion (> 30%) of seasonal precipitation. Brush management (chemical or prescribed burn) 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.


State 2
Litter cover can be reduced by 50% or more, and bare ground can increase significantly immediately following fire. Repeated fires significantly reduce site productivity. Dominance of annual grass and forbs are associated with unstable hydrologic conditions Annual grass dominated sites will not have sufficient cover when runoff typically occurs. Due to diffuse basal characteristics, annual grasses generally do not have the capacity to catch and hold sediment like bunchgrass clumps. Heavy stands of annual grasses may contribute to increased infiltration in spring and early summer, but will not have sufficient cover during other times to protect the site. These sites will demonstrate significant variability in infiltration and runoff due to seasonal changes in cover. Snow accumulation may be reduced since there are insufficient shrubs to prevent drifting, and earlier melt off is probable without shrub cover. Likewise, there is no shrub cover to mitigate the impact of rainfall on soil, which leads to increased soil detachment and availability for transport. 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 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. Sediment yields increase as rill erosion processes become dominant, even on lower slopes. With improper grazing management, trail areas become compacted, leading to further rilling and gully creation.

State 3
The site is transitioning from shrub-steppe to woodland, with significant changes to hydrology as a result of altered community composition and decreased structural diversity. As juniper invades and trees become large in stature, understory plants may be out-competed for water and decrease significantly on sites where water is a limiting factor (shallow soils, south slopes, coarse textured soils/increased rock content, etc.). Deep-rooted perennials remaining are primarily within the juniper canopy zone. Interspaces are largely bare ground, with increased evaporative loss. Soils in bare interspaces are more susceptible to raindrop impact, which can lead to reduction in aggregate stability and infiltration capacity. Effective precipitation is reduced with high interception losses as the site approaches stand closure. Increased bare ground and the water repellent nature of juniper litter in coppice zones increase overland flow connectivity and hence runoff. Erosion can be significant from high intensity storms as rilling becomes the dominant process for sediment loss. This increases the risk of gully formation, especially on steeper slopes. Potential for restoration decreases as stand ages and desirable species are lost. If juniper removal is utilized, leaving juniper debris on the ground after mechanical treatment can reduce runoff and evaporative soil water loss.

State 4
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

Recreational uses

Recreation opportunities include hunting, hiking, off-road vehicles, horseback riding and photography.

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
Brendan Brazee, 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.

Petersen, S.L., 2004. A Landscape-Scale Assessment of Plant Communities, Hydrologic Processes, and State-and-Transition Theory in a Western Juniper Dominated Ecosystem. PhD Dissertation. Oregon State University, Corvallis, Oregon.

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

D. Edgerton
Dave Franzen And Jacy Gibbs

Approval

Kendra Moseley, 12/11/2019