Natural Resources
Conservation Service
Ecological site R052XC223MT
Silty-Steep (SiStp)
10-14" p.z.
Last updated: 4/14/2025
Accessed: 08/20/2026
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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): 052X–Brown Glaciated Plains
The Brown Glaciated Plains, MLRA 52, is an expansive and agriculturally and ecologically significant area. It consists of around 14.5 million acres and stretches across 350 miles from east to west, encompassing portions of 15 counties in north-central Montana. This region represents the southwestern limit of the Laurentide Ice Sheet and is considered to be the driest and westernmost area within the vast network of glacially derived prairie pothole landforms of the northern Great Plains. Elevation ranges from 2,000 feet (610 meters) to 4,600 feet (1,400 meters).
Soils are primarily Mollisols, but Entisols, Inceptisols, Alfisols, and Vertisols are also common. Till from continental glaciation is the predominant parent material, but alluvium and bedrock are also common. Till deposits are typically less than 50 feet thick, and in some areas glacially deformed bedrock can be found at or near the soil surface (Soller, 2001). Underlying sedimentary bedrock largely consisting of Cretaceous shale, sandstone, and mudstone (Vuke et al., 2007) is commonly exposed on hillslopes, particularly along drainageways. Significant alluvial deposits occur along glacial outwash channels and major drainages, including portions of the Missouri, Teton, Marias, Milk, and Frenchman Rivers. Large glacial lakes, particularly in the western half of the MLRA, deposited clayey and silty lacustrine sediments (Fullerton et al., 2013).
Much of the western portion of this MLRA was glaciated towards the end of the Wisconsin age, and the maximum glacial extent occurred approximately 20,000 years ago (Fullerton et al., 2004). The result is a geologically young landscape that is predominantly a level till plain interspersed with lake plains and dominated by soils in the Mollisol and Vertisol orders. These soils are very productive and generally are well suited to dryland farming. Much of this area is aridic-ustic. Crop-fallow dryland wheat farming is the predominant land use. Areas of rangeland typically are on steep hillslopes along drainages.
The rangeland, much of which is native mixedgrass prairie, increases in abundance in the eastern half of the MLRA. The Wisconsin-age till in the north-central part of this area typically formed large disintegration moraines with steep slopes and numerous poorly drained potholes. A large portion of Wisconsin-age till occurring on the type of level terrain that would typically be optimal for farming has large amounts of less-suitable sodium-affected Natrustalfs. Significant portions of Blaine, Phillips, and Valley Counties were glaciated approximately 150,000 years ago during the Illinoisan age. Due to erosion and dissection of the landscape, many of these areas have steeper slopes and more exposed bedrock than areas glaciated during the Wisconsin age (Fullerton and Colton, 1986).
While much of the rangeland in the aridic-ustic portion of MLRA 52 is classified as belonging to the “dry grassland” climatic zone, sites in portions of southern MLRA 52 may belong to the “dry shrubland” climatic zone. The dry shrubland zone represents the northernmost extent of the big sagebrush (Artemisia tridentata) steppe on the Great Plains. As similar soils occur in both southern and northern portions of the MLRA, it is currently hypothesized that climate is the primary driving factor affecting big sagebrush distribution in this area. However, the precise factors are not fully understood at this time.
Sizeable tracts of largely unbroken rangeland in the eastern half of the MLRA and adjacent southern Saskatchewan are home to the Northern Montana population of greater sage-grouse (Centrocercus urophasianus), and large portions of this area are considered to be a Priority Area for Conservation (PAC) by the U.S. Fish and Wildlife Service (U.S. Fish and Wildlife Service, 2013). This population is unique among sage grouse populations because many individuals overwinter in the big sagebrush steppe (dry shrubland) in the southern portion of the MLRA and then migrate to the northern portion of the MLRA, which lacks big sagebrush (dry grassland), to live the rest of the year (Smith, 2013).
Areas of the till plain near the Bearpaw and Highwood Mountains as well as the Sweetgrass Hills and Rocky Mountain foothills are at higher elevations, receive higher amounts of precipitation, and have a typic-ustic moisture regime. These areas have significantly more rangeland production than the drier aridic-ustic portions of the MLRA and have enough moisture to produce crops annually rather than just bi-annually, as in the drier areas. Ecological sites in this higher precipitation area are classified as the moist grassland climatic zone.Classification relationships
NRCS Soil Geography Hierarchy
• Land Resource Region: Northern Great Plains
• Major Land Resource Area (MLRA): 052 Brown Glaciated Plains
• Climate Zone: Dry Grassland
National Hierarchical Framework of Ecological Units (Cleland et al., 1997; McNab et al., 2007)
• Domain: Dry
• Division: Temperate Steppe
• Province: Great Plains-Palouse Dry Steppe Province 331
• Section: Northwestern Glaciated Plains 331D
• Subsection: Montana Glaciated Plains 331Dh
• Landtype association/Landtype phase: N/A
National Vegetation Classification Standard (Federal Geographic Data Committee, 2008)
• Class: Mesomorphic Shrub and Herb Vegetation Class (2)
• Subclass: Temperate and Boreal Grassland and Shrubland Subclass (2.B)
• Formation: Temperate Grassland, Meadow, and Shrubland Formation (2.B.2)
• Division: Great Plains Grassland and Shrubland Division (2.b.2.Nb)
• Macrogroup: Hesperostipa comata – Pascopyrum smithii – Festuca hallii Grassland Macrogroup (2.B.2.Nb.2)
• Group: Pascopyrum smithii - Hesperostipa comata - Schizachyrium scoparium - Bouteloua spp. Mixedgrass Prairie Group (2.B.2.Nb.2.c)
• Alliance: Pascopyrum smithii – Nassella viridula Northwestern Great Plains Herbaceous Alliance
• Association: Pascopyrum smithii – Hesperostipa comata Central Mixedgrass Herbaceous Vegetation
EPA Ecoregions
• Level 1: Great Plains (9)
• Level 2: West-Central Semi-Arid Prairies (9.3)
• Level 3: Northwestern Glaciated Plains (42)
• Level 4: North Central Brown Glaciated Plains (42o) & Glaciated Northern Grasslands (42j)Ecological site concept
Silty Steep 10-14" p.z. occurs on hillslopes, hills, and till plains where slopes are 15 percent or greater. This site is typically found on linear or concave backslopes.
The distinguishing characteristics of this site are moderately steep to very steep slopes, a relatively well developed soil profile, and less than 5 percent calcium carbonate (lime) concentration in the upper 5 inches of soil. Soils are typically moderately deep to very deep (greater than 20 inches to bedrock) and derived from glacial till. They commonly have a mollic epipedon. Soil surface horizons fall within the fine-loamy textural family and contain 18 to 35 percent clay. Underlying horizons typically, but not always, have an argillic horizon that contains between 18 to 45 clay, depending on the soil series. In general, growing conditions are relatively favorable on this site and species diversity is commonly high. Production is slightly less than on similar soils on gentler slopes due to increased runoff potential.Associated sites
R052XC212MT Sandy (Sy) 10-14" p.z.
Is not located on steep slopes, different species composition and soil texture.
R052XC217MT Silty (Si) 10-14" p.z.
Slopes <15%; more forage production; different species composition.
R052XC207MT Overflow (Ov) 10-14" p.z.
Receives additional run-in moisture from surrounding landscape; different species composition, higher productivity.
R052XC214MT Shallow (Sw) 10-14" p.z.
Soil depth less than or equal to 20 inches to a restrictive layer; less forage production.
Similar sites
R052XN168MT Silty-Steep (SiStp) 10-14" p.z.
No little bluestem present.
R053AE058MT Loamy Steep (Lostp) (Legacy) RRU 53AE
Little bluestem more persistent in HCPC. Still have bluebunch wheatgrass,but not as prevalent.
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Krascheninnikovia lanata
Herbaceous (1) Pseudoroegneria spicata
(2) Schizachyrium scopariumPhysiographic features
This site occurs on slopes of rolling till plains, hills and hill slopes. Slopes are in excess of 15%. This site occurs on all exposures. Elevations normally range from 2000 to 3500 feet.
Table 2. Representative physiographic features
Landforms (1) Till plain
(2) Hill
(3) Hillslope
Runoff class Medium to very high Flooding frequency None Ponding frequency None Elevation 2000 – 3500 ft Slope 15 – 60 % Aspect Aspect is not a significant factor Table 3. Representative physiographic features (actual ranges)
Runoff class Not specified Flooding frequency Not specified Ponding frequency Not specified Elevation 1875 – 3800 ft Slope 0 % Climatic features
A semi-arid, temperate climate characterizes the Glaciated Plains. The predominance of cool season species has evolved to take advantage of the precipitation regime that peaks in late spring-early summer (June). Seventy-five percent of the annual precipitation usually falls as steady, soaking, frontal system rains. Summer rains usually come with thunderstorms. Precipitation is the most important factor influencing production (Heitschmidt et al 2005). Severe drought occurs on average in two out of every ten years (Cooper, et al., 2001).
Table 4 Representative climatic features
Frost-free period (characteristic range) 90-120 days Freeze-free period (characteristic range) 120-140 days Precipitation total (characteristic range) 10-10 in Frost-free period (average) 90 days Freeze-free period (average) 130 days Precipitation total (average) 10 in Characteristic rangeActual rangeBarLineFigure 1. Monthly precipitation range
Characteristic rangeActual rangeBarLineFigure 2. Monthly minimum temperature range
Characteristic rangeActual rangeBarLineFigure 3. Monthly maximum temperature range
BarLineFigure 4. Monthly average minimum and maximum temperature
Figure 5. Annual precipitation pattern
Figure 6 Annual average temperature pattern
Climate stations used
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(1) CHESTER [USC00241692], Chester, MT
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(2) GLASGOW [USW00094008], Glasgow, MT
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(3) HAVRE CITY CO AP [USW00094012], Havre, MT
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(4) SHELBY [USC00247500], Shelby, MT
">Influencing water features
This site is not influenced by water from streams.
Wetland description
This site is not influenced by water from wetlands.
Soil features
These soils formed in glacial till. The surface layer of these soils vary from 0-3 inches in depth and typically have loam, silt loam, gravelly loam or silty clay loam texture. Underlying material, to a depth of 60 inches or more, has a clay loam texture. Permeability is moderate to moderately slow, and available water capacity is high. Effective rooting depth is >60 inches. Where this soil is under native vegetation, the average wetting depth is about 24 inches. Runoff is medium to very high rapid, and the hazard of water erosion is high. The hazard of soil blowing is also high. Soils are often calcareous. The following soil taxonomic units characterize this site: Zahill and Hillon. Soil ph normally ranges from 7.4 to 8.4.
Table 5. Representative soil features
Parent material (1) Till
Surface texture (1) Gravelly loam
(2) Silt loam
(3) Clay loam
Family particle size (1) Fine-loamy
Drainage class Well drained Permeability class Moderate Soil depth 20 – 78 in Surface fragment cover <=3" 0 – 35 % Surface fragment cover >3" 0 – 5 % Available water capacity
(Depth not specified)4 – 7 in Calcium carbonate equivalent
(Depth not specified)0 – 15 % Electrical conductivity
(Depth not specified)0 – 4 mmhos/cm Sodium adsorption ratio
(Depth not specified)0 – 8 Soil reaction (1:1 water)
(Depth not specified)7.4 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)0 – 10 % Subsurface fragment volume >3"
(Depth not specified)0 – 5 % Ecological dynamics
This ecological site developed under Northern Great Plains climatic conditions, the natural influence of herbivory and a fire frequency of 5-7 years (Frost 1998). Plant community interpretations are based on the Historic Climax Plant Community (HCPC).
Changes in the HCPC are brought about by frequency, timing and intensity of past grazing use, series of dry or wet years, or disturbances by fire, insect infestations, noxious weed colonization and recruitment, etc. As the HCPC regresses to lower seral stages, the deep-rooted perennial grasses are replaced by blue grama, sandberg bluegrass, fringed sagewort, hoods phlox, threadleaf sedge, hairy goldaster, and dense clubmoss. The dominance of these short grasses, warm season forbs and half-shrubs in the plant community disrupts ecological processes, impairs the biotic integrity of the site, and adversely affects resiliency. The system’s ability to recover to higher seral states is restricted or impeded.
State and Transition Diagram
Traditional theories of plant succession leading to a single climax community are inadequate for understanding the complex successional pathways of this ecological site in the glaciated plains (Stringham et al. 2003). This ecological site is more aptly described using state-and-transition vegetation dynamics in a non-linear framework. A “state” is an alternative, persistent vegetation community that is not simply reversible in the linear successional framework. States are depicted as seral stages, while pathways between states are “transitions.” The latter can be transient or persisting (crosses a threshold). Transitions may be triggered by climatic events, fire, grazing, farming, etc.
Three important plant communities and associated successional pathways for the Reference state (State 1), and the transitions across a threshold to State 2 are illustrated below for the Silty-Steep 10-14” p.z. site in the Glaciated Plains.State and transition model
Custom diagramStandard diagram
More interactive model formats are also available. View Interactive Models
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
T1A - Extended drought (greater than 7 years), non-prescribed grazing, no fire R2A - Prescribed grazing, fire (natural interval 5 to 7 years), extended favorable precipitation. State 1 submodel, plant communities
1.1A - No fire, non-prescribed grazing, drought (3 to 5 years) 1.2A - Fire (natural interval 5 to 7 years), prescribed grazing, normal precipitation 1.2B - No fire, prescribed grazing, prolonged drought (5 to 7 years) 1.3A - Fire (natural interval 5 to 7 years), prescribed grazing, favorable precipitation State 1
ReferenceCommunity 1.1
Historic Climax Plant Community (HCPC) Tall- and medium-height cool-season perennial grasses with less than or equal to 5 percent native perennial forbs and less than or equal to 10 percent native shrubs.Tall- and medium-height cool-season perennial grasses with less than or equal to 5 percent native perennial forbs and less than or equal to 10 percent native shrubs.
The interpretive plant community for this site is the Historic Climax Plant Community (HCPC). Cool and warm season tall and mid-grasses (such as little bluestem, bluebunch wheatgrass, green needlegrass, western wheatgrass, thickspike wheatgrass, porcupine grass and needle and thread grass) dominate the HCPC. These cool season grasses represent about 75% of the total annual plant production in the community. Bluebunch wheatgrass and little bluestem are the dominant indicator species on Silty-Steep 10-14” p.z. sites in the central Glaciated Plains. As one moves east toward the eastern Glaciated Plains, bluebunch wheatgrass production and percent composition is reduced. In contrast, little bluestem (a warm season species) is much more common on Silty-Steep 10-14” p.z. sites in the eastern Glaciated Plains.
Less common species in the HCPC include short grasses and sedges (plains muhly, prairie junegrass, threadleaf sedge, plains reedgrass and blue grama). These short grasses and grasslike plants contribute about 10% of the annual production. Dotted gayfeather, black Sampson, scurfpeas, and prairie clovers are important warm season forbs. American vetch may be the most important cool season forb. In addition to being desirable forage, it also fixes nitrogen. Total forb production normally represents less than 5% of the total annual production.
Winterfat is a common warm season shrub that is highly prized as browse for livestock and wildlife. Rose and snowberry, two cool season shrubs often are present on the site. Silver sagebrush and fringed sagewort, two warm season shrubs may also be found on the site. Overall, shrubs account for about 10% of the annual plant production.
Annual production of the Historic Climax Plant Community (HCPC) on Silty-Steep 10-14” p.z. ecological sites in the Glaciated Plains is not fully documented by either range inventory data collected (in 2001 and 2004) on the Fort Peck or Fort Belknap Indian Reservations, or with soil-vegetation correlation data (NRCS-417 Forms) in Northeastern Montana. Inventory data indicates that Similarity indices (SI) of 55-75% were associated with annual production estimates of 925 lbs/ac.
Thus, 1200 lb/ac is accepted as a reasonable average production estimate for the HCPC, as inventoried and reported in the August 1981 range site description. Average annual production is expected to increase and decrease, respectively on more mesic and xeric portions of the central Glaciated Plains.
The HCPC is well adapted to the Glaciated Plains. Precipitation is the most important factor influencing production (Heitschmidt et al 2005). The functional and structural diversity of plant species (annuals, perennials, cool and warm season grasses, forbs and shrubs) optimize the capture of solar energy and maximize subsequent plant growth through the efficient use of available soil water and nutrient cycling. When disturbances reduce the competitiveness of tall cool season grasses of the HCPC, warm season perennial forbs (hairy golden aster, scurfpea), annual forbs (wooly plantain, etc.) half-shrubs (fringed sagewort, etc.) and annual bromes often invade the community. The HCPC is resilient. With proper grazing management and non-drought conditions, the species characteristic of the HCPC will replace these lower successional species within a few years.
Litter is in contact with 50-60% of the soil surface. About 10% of the soil surface is bare ground (i.e., unprotected by litter, rock, moss, and plant canopy). Because of the slope, vegetation and soils, rills, water flow patterns, and some movement of litter are noticeable following a rainfall event.
The major plant species composition and production by dry weight are shown for the HCPC in the following table. Total annual production has been derived from several sources, and has been adjusted to represent a typical annual precipitation cycle.Figure 7. Annual production by plant type (representative values) or group (midpoint values)
Table 6. Annual production by plant type
Plant type Low
(lb/acre)Representative value
(lb/acre)High
(lb/acre)Grass/Grasslike 725 1020 1230 Shrub/Vine 85 120 150 Forb 40 60 70 Total 850 1200 1450 Table 7. Ground cover
Tree foliar cover 0% Shrub/vine/liana foliar cover 0% Grass/grasslike foliar cover 0% Forb foliar cover 0% Non-vascular plants 0-10% Biological crusts 0-0% Litter 50-60% Surface fragments >0.25" and <=3" 0-0% Surface fragments >3" 0-0% Bedrock 0% Water 0% Bare ground 10-20% Table 8. Soil surface cover
Tree basal cover 0% Shrub/vine/liana basal cover 10-10% Grass/grasslike basal cover 20-30% Forb basal cover 0-10% 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% Table 9. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – 0-20% 0-10% 0-40% >0.5 <= 1 – 0-40% 0-40% 0-50% >1 <= 2 – 0-30% 0-40% 0-8% >2 <= 4.5 – 0-10% 0-10% 0-2% >4.5 <= 13 – – – – >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Community 1.2
Plant Community A Shift in species composition, lower production, medium- and tall-height cool-season perennial grasses, about 5 percent native perennial forbs and 10 percent native shrubs.Shift in species composition, lower production, medium- and tall-height cool-season perennial grasses, about 5 percent native perennial forbs and 10 percent native shrubs.
Total plant production averages about 1,000 lbs/ac in this Plant Community, or about 80% of the production in the HCPC. The decrease in production results from a shift in species composition. Needle and thread grass, threadleaf sedge, blue grama and plains reedgrass increased at the expense of the tall, more palatable grasses (bluebunch wheatgrass, green needlegrass, western/thickspike wheatgrasses and little bluestem). In comparison to the HCPC, production of blue grama, prairie junegrass, plains reedgrass, threadleaf sedge and other short grasses increased. They now account for about 20% of the total annual production. Exact response by these species varies with the kind of disturbance (drought, grazing, etc.) and with precipitation (amount and timing).
Total production of native forbs remains at about 5% of annual production of the site. However, the palatable species (prairie clovers, American vetch and dotted gayfeather) decrease in abundance (relative to the HCPC). The open niches allow hairy goldenaster, bastard toadflax, prairie thermopsis, etc. to become more abundant. Shrubs continue to account for about 10% of the total production. However, species such as fringed sagewort and silver sagebrush increase (relative to the HCPC). Similarity index values from 55-75% are associated with this community. In contrast to the HCPC, range conservationists have moderate concerns regarding lower successional plants, lower infiltration rates and potentially higher runoff rates, plant functional/structural group shifts, and decreasing amount of litter.Community 1.3
Plant Community B - Pre-threshold community Medium- and short-height cool- and warm-season perennial grasses, increase of forb species, and greater than 15 percent native shrubs.Medium- and short-height cool- and warm-season perennial grasses, increase of forb species, and greater than 15 percent native shrubs.
Plant Community B is dominated by needle and thread grass, blue grama, plains reedgrass, prairie junegrass and upland sedges. However, individual plants of bluebunch wheatgrass, green needlegrass, western/thickspike wheatgrass and little bluestem remain in the Community. The short grass and grass-like plants make up about 30% of the total production. Total vegetative production declines to about 800 lbs/ac in a normal year.
Hairy goldenaster, scarlet globemallow, scurfpeas and other warm season forbs increase at the expense of the prairie clovers and American vetch. Forbs account for about 10% total annual production. Fringed sagewort, a half-shrub increases at the expense of winterfat. Silver sagebrush and rose also increase on some sites. Shrubs account for about 15% of the total plant production. SI values for this community vary from 35-55%.
Litter provides cover for about 30% of the ground, while bare ground increases to about 25%. Rills, water flow patterns and litter movement are evident on the site.
The tall cool season grasses have poor vigor, with little seed production. Most of the seedlings and young plants appear to represent short grasses and warm season forbs. Lower successional plant species and some invasive species are a significant part of the community. Japanese brome and cheatgrass are usually present wherever rodents or other disturbances create an open niche.
Plant Community B is fairly resilient, but it is not highly resistant to disturbance. It is the “pre-threshold” community. Therefore, it is critical that this community be recognized and strategies implemented to prevent further regression. Community B can readily regress to a lower state, from which succession back to the HCPC community or Plant Community A would be restricted.Pathway 1.1A
Community 1.1 to 1.2No fire, non-prescribed grazing, drought (3 to 5 years) Successional pathways from the HCPC are influenced by frequency, timing and intensity of grazing, precipitation patterns, fire, insect infestations, noxious weed colonization and recruitment, etc. As communities regress from HCPC, medium and short grasses increase at the expense of mid and tall cool season grasses. The medium and short grasses consist of cool (prairie junegrass, upland sedges, and sandberg bluegrass) and warm season grasses (blue grama and plains reedgrass) and grasslike plants.
Pathway 1.2A
Community 1.2 to 1.1Fire (natural interval 5 to 7 years), prescribed grazing, normal precipitation Plant Community A is resilient. Successional processes can readily return Plant Community A to the HCPC during normal precipitation cycles. Succession is facilitated by prescribed grazing, the incorporation of the natural fire regime into the system, etc.
Pathway 1.2B
Community 1.2 to 1.3No fire, prescribed grazing, prolonged drought (5 to 7 years) Plant community A is resistant. However, prolonged drought, non-prescribed grazing, and the removal of fire from the system will result in retrogression to Community B. The causative factors of regression are usually apparent with careful observation.
Pathway 1.3A
Community 1.3 to 1.2Fire (natural interval 5 to 7 years), prescribed grazing, favorable precipitation Favorable precipitation and prescribed grazing are normally required for succession to higher successional communities (Community A or HCPC). Management strategies should focus on grazing deferment to increase vigor and seed production of desirable plants, and to increase litter cover. Increasing litter is extremely critical because of the steep slopes.
State 2
DegradedCommunity 2.1
Plant Community C Short, warm-season perennial grasses, annual forbs, clubmoss, and shrubs greater than 20 percent, invasive species present.Short, warm-season perennial grasses, annual forbs, clubmoss, and shrubs greater than 20 percent, invasive species present.
Plant Community C in State 2 is dominated by blue grama, prairie junegrass, sandberg bluegrass, prairie sandreed, other short grasses, and clubmoss. However, a few individual western wheatgrass, bluebunch wheatgrass, little bluestem, etc. plants seem to persist longer than they do on surrounding ecological sites. The ability of these palatable plants to persist on the Silty-Steep site is probably a reflection of lighter grazing use. Cattle prefer grazing areas with less than 15% slope, and those areas adjacent to livestock water developments. Red threeawn, Japanese brome and cheatgrass often invade this Community.
Wooly plantain, hoods phlox, hairy goldenaster and bastard toadflax are common forbs. Fringed sagewort usually increases. Silver sagebrush and rose may also increase. The most palatable shrubs are nearly absent. SI values of less than 25% are associated with this plant community.
Surface runoff and soil erosion are a serious concern on the Silty-Steep 10-14” p.z. site. The decrease in plant cover and litter increases the susceptibility to erosion. Less vegetative growth is available for transfer to litter, and nutrient cycling is delayed or impeded. As bare ground increases, infiltration decreases and/or surface runoff and soil evaporation increases. Because ecological processes of the site are no longer balanced and sustained, shallow rooted, warm season species continue to gain a competitive advantage over the deep rooted, cool season species. The biotic integrity of the site is degraded.
In comparison to the State 1 communities, State 2 is less efficient in capturing solar energy and converting it to carbohydrates for plant growth. Total vegetative production averages about 400 lbs/ac. The absence of tall and mid cool season perennial grasses, plus the shift from cool season plants to warm season plants, indicates that the structural and functional processes of this site have been disrupted. However, if the soil surface is stable and does not erode, site potential may not be significantly impaired.Transition T1A
State 1 to 2Extended drought (greater than 7 years), non-prescribed grazing, no fire Plant Community B will regress to a lower state with any combination of extended drought, non-prescribed grazing and unfavorable climatic patterns. This transition from Community B to State 2 represents a threshold, or a point in space and time at which one or more of the primary ecological processes responsible for maintaining the sustained equilibrium of the state degrades beyond the point of self-repair.
Restoration pathway R2A
State 2 to 1Prescribed grazing, fire (natural interval 5 to 7 years), extended favorable precipitation. Plant community succession across a threshold to a higher state is ecologically difficult in most ecosystems. A significant input of energy is often required for succession to occur. In instances of prolonged favorable climatic conditions combined with proper management, the significant input of energy that is normally required to move this site across the threshold (from State 2 to State 1) may not be needed. Because of the steep slopes, mechanical treatments and range seeding are not recommended. Ranchers should be aware of the limitations of this site. Rather than trying to change nature, managers must learn to live within the environmental boundaries of this site. Prescribed grazing management should be a requirement for this site.
Additional community tables
Table 10. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Cool-season Bunchgrasses 420–900 bluebunch wheatgrass PSSP6 Pseudoroegneria spicata 120–450 – needle and thread HECO26 Hesperostipa comata 120–240 – green needlegrass NAVI4 Nassella viridula 90–180 – porcupinegrass HESP11 Hesperostipa spartea 90–180 – 1 Rhizomatous Wheatgrasses 180–360 western wheatgrass PASM Pascopyrum smithii 90–180 – tufted wheatgrass ELMA7 Elymus macrourus 90–180 – 3 Warm-season Bunchgrasses 210–420 little bluestem SCSC Schizachyrium scoparium 120–240 – plains muhly MUCU3 Muhlenbergia cuspidata 90–180 – 4 Miscellaneous Grasses 0–120 threadleaf sedge CAFI Carex filifolia 0–60 – Sandberg bluegrass POSE Poa secunda 0–60 – prairie Junegrass KOMA Koeleria macrantha 0–60 – blue grama BOGR2 Bouteloua gracilis 0–60 – plains reedgrass CAMO Calamagrostis montanensis 0–60 – Grass, native 2GN Grass, native 0–60 – Forb5 Dominant Forbs 24–120 dotted blazing star LIPU Liatris punctata 12–60 – American vetch VIAM Vicia americana 12–60 – 2 Clovers 24–120 white prairie clover DACA7 Dalea candida 12–60 – purple prairie clover DAPU5 Dalea purpurea 12–60 – 7 Miscellaneous Forbs 0–60 Missouri goldenrod SOMI2 Solidago missouriensis 0–60 – aster ASTER Aster 0–60 – scarlet globemallow SPCO Sphaeralcea coccinea 0–60 – scurfpea PSORA2 Psoralidium 0–60 – hairy false goldenaster HEVI4 Heterotheca villosa 0–60 – upright prairie coneflower RACO3 Ratibida columnifera 0–60 – prairie thermopsis THRH Thermopsis rhombifolia 0–60 – pussytoes ANTEN Antennaria 0–60 – bastard toadflax COUM Comandra umbellata 0–60 – milkvetch ASTRA Astragalus 0–60 – beardtongue PENST Penstemon 0–60 – spiny phlox PHHO Phlox hoodii 0–60 – buckwheat ERIOG Eriogonum 0–60 – lesser spikemoss SEDE2 Selaginella densa 0–60 – plains pricklypear OPPO Opuntia polyacantha 0–60 – Forb, native 2FN Forb, native 0–60 – Shrub/Vine8 Dominant Shrubs 15–60 winterfat KRLA2 Krascheninnikovia lanata 15–60 – 9 Miscellaneous Shrubs 0–120 snowberry SYMPH Symphoricarpos 0–60 – rose ROSA5 Rosa 0–60 – rubber rabbitbrush ERNA10 Ericameria nauseosa 0–60 – silver sagebrush ARCA13 Artemisia cana 0–60 – prairie sagewort ARFR4 Artemisia frigida 0–60 – creeping juniper JUHO2 Juniperus horizontalis 0–60 – Shrub (>.5m) 2SHRUB Shrub (>.5m) 0–60 – broom snakeweed GUSA2 Gutierrezia sarothrae 0–1 – plains pricklypear OPPO Opuntia polyacantha 0–1 – Table 11. Community 1.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 12. Community 1.3 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 13. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
Livestock Management
This site evolved with trampling, defoliation (ungulates, grasshoppers and jackrabbits, and other herbivores), fire and drought. Its plant communities are moderately resistant to disturbances which may alter ecological processes. They are also moderately resilient. Following perturbations such as drought, which allows blue grama and other increasers to increase at the expense of the mid and tall grasses, succession occurs with subsequent rainfall. Thus, the HCPC, or Communities A and B may be present at any given time in State 1. During “average” years, the site has the potential to produce 1200 lbs of forage per acre.
Forage production shows far greater variations in response to changes in annual precipitation than to different grazing intensities (Heitschmidt et al 2005) However, proper stocking rates and prescribed grazing is needed to ensure that the site remains in a high seral or HCPC state. Without proper grazing management the mid-to-tall grass community will regress to a blue grama, prairie junegrass, dense clubmoss community. In comparison to the high seral state, suggested stocking rates on sites in the early seral state represent a 4-fold reduction. Experience indicates that prescribed grazing prevents further deterioration in State #2. Furthermore, significant plant succession may occur within a reasonable time frame. Very few livestock losses are reported from poisonous plants.
Similarity index values of 35-55% characterized most of the Silty-Steep 10-14” p.z. sites inventoried on the Fort Peck and Fort Belknap Reservations in 2001-2004. SI values of less than 25% were not encountered. In contrast, SI’s of less than 25% were frequently associated with adjacent Silty 10-14” p.z. sites. Similar observations occur on other ranches in the Glaciated Plains. In contrast to adjacent Silty 10-14” p.z. site (often near water) where very few highly palatable cool season grasses remain because of repeated, frequent grazing events, a fairly diverse mix of desirable, cool season plants often grow on the Silty-Steep 10-14” p.z. site. The higher range health rating of this site probably results from less livestock grazing. Utilization of plants growing on slopes and on sites more distant from water developments is normally less than it is for plants growing on lower, more gently sloping terrain that is situated near watering facilities.
This site is suitable for livestock grazing from May through October. The grass-dominant plant community is better suited for cattle, rather than sheep grazing. However, sheep are better adapted to grazing the steep slopes, especially if watering facilities are relatively distant. Therefore, a mix of cattle and sheep usage often merits consideration.
Wildlife Interpretations
State #1 of the Silty-Steep 10-14” p.z. ecological site includes the HCPC and two additional communities. This state provides forage for mule deer during most of the year. However, the overall forage potential is limited by the relatively low production and diversity of forbs and shrubs. Low shrub cover also limits the potential of the site for thermal and escape cover. Most deer use occurs along the edges of the site where it borders deciduous wooded draws, badland sites, etc.
Species diversity and cover associated with the HCPC or other communities in the Reference State also provide habitat for sharp-tailed grouse and other upland birds. Most wildlife usage occurs along the “ecotones” between the Silty-Steep 10-14” p.z. site and wooded draws. The relative absence of big sagebrush limits the potential of this site for sage grouse habitat. The few sage grouse that exist in the Glaciated Plains are associated with silver sagebrush.
Species diversity and litter also provide favorable habitats for deer mice, rabbits and other small mammals. Golden eagles, redtail and ferruginous hawks are often circling over the landscape searching for prey.
Communities that are in State #2 are much less suitable for big game, upland birds and most species of small mammals. Prairie dogs usually are not a problem on Silty-Steep 10-14” p.z. sites because slopes are greater than 15%. Prairie dogs prefer slopes of 1-10%.
Plant Preferences by Animal Kind
Refer to NRCS Field Office Technical Guide, Section IIE, General Information, for tables displaying plant preferences by livestock and wildlife.Hydrological functions
Soils associated with this ecological site are in Hydrologic Soil Groups B and C. Infiltration rates are generally moderate. The runoff potential is medium to very high, varying with slope and ground cover.
Good hydrologic conditions exist on Silty-Steep 10-14” p.z. sites that are either in a high seral state or at the HCPC (State 1). Canopy cover (grass, forbs and shrubs) is greater than 90% in these communities, which is conducive to high infiltration rates and minimizes runoff and erosion.
Communities in early seral states (State 2) are generally considered to be in poor hydrologic condition. Concerns are valid. The excessive amount of bare ground results from inadequate plant cover and litter. Therefore, infiltration decreases and surface runoff increases. The desirable tall and mid-grasses are unable to effectively utilize available moisture. Water and wind erosion are major concerns on Silty-Steep 10-14” p.z. sites. Prescribed grazing management is needed to restore vigor of the higher-successional plants and to replenish or maintain about 50% litter to protect the soil resource.Recreational uses
Hunters are probably the most common recreational user this ecological sites. The site is also used by hikers and photographers. Many of these sites show symptoms of exuberant off-road ATV use. ATV use should be discouraged on these sites.
Wood products
This site has no significant value for wood products.
Other information
The Silty-Steep 10-14” p.z. ecological site in the central Glaciated Plains is resistant to perturbations. However, the site loses its resiliency when the plant community regresses from State 1 to State 2. Reproductive capability of the higher successional plants and annual production declines as the site moves toward the threshold separating State 1 from State 2. Annual production in early seral states is less than 1/4 of the potential at HCPC. Thus, litter and the number of structural/functional groups are adversely affected.
Supporting information
Inventory data references
Data Source Number of Records Sample Period State County SCS-Range-417 2 (#513, #514) 1991--1992 MT Phillips ECS-1 Modified Double Sampling 18 2001-2004 MT Blaine, Roosevelt, Sheridan, Phillips, Valley USDA-SCS-MT. 1981. Technical Range Site Description
Other references
Branson, F. A., and R. F. Miller. 1981. Effects of increased precipitation and grazing management on Northeastern Montana rangelands. J. Range Manage. 34: 3-10.
Dyksterhuis, E. J. 1949. Condition and management of rangeland based on quantitative ecology. J. Range Manage.2:104-115.
Frost, Cecil C. 1998. Presettlement fire frequency regimes of the United States: a first approximation. Pages 70-81 in Teresa L. Pruden and Leonard A. Brennan (eds.). Fire in ecosystem management: shifting the paradigm from suppression to prescription. Tall Timbers Fire Ecology Conference Proceedings, No. 20. Tall Timbers Research Station, Tallahassee, Fl.
Heitschmidt, R. K., K. D. Klement, and M. R. Haferkamp. 2005. Interactive effects of drought and grazing on Northern Great Plains rangelands. Rangeland Ecol. Manage. 58: 11-19.
Stringham, T. K., W. C. Krueger, and P. L. Shaver. 2003. State and transition modeling: an ecological process approach. J. Range Manage. 56:106-113.
USDI BLM USGS and USDA NRCS. 2000. Interpreting indicators of rangeland health. Tech. Ref. 1734-6.Contributors
Kirt Walstad
Approval
Kirt Walstad, 4/14/2025
Acknowledgments
Site Description Revisions The 2005 Silty-Steep 10-14” p.z. ecological site description replaces earlier dated versions of Silty-Steep 10-14” p.z., Thin Silty 10-14” p.z. and Thin Hilly 10-14” p.z. descriptions in Rangeland Resource Unit 52XC. This 2005 revision incorporates the State and Transition Model theory, additional data on site productivity, and an improved understanding of many rangeland health indicators. The USDA-SCS-MT Technical Range Site Description (August 1981), which this site description partially replaces, reports that total annual production averages about 1200 lbs/ac on the Thin Hilly 10-14” p.z. ecological site. Production varies from 850 lbs/ac in an unfavorable year to 1450 lbs in a favorable year. The Thin Hilly site was based on the concept that slope was the key factor characterizing the site, soil texture and other factors were considered less important. Because the earlier approach did not provide the site specific information required for management of some landscapes, the current effort of separating the Thin Hilly site into Silty-Steep 10-14” p.z., Clayey-Steep 10-14” p.z., and Sandy-Steep 10-14” p.z. ecological sites is justified. Site Description Approval This ecological site description is approved with the understanding that it is no more than another step in our continual effort to update the NRCS technical guide. In order to facilitate the process, NRCS field personnel are encouraged to forward existing information and/or new data that can be used to improve the utility of this site description. Please forward the information and data to the State Rangeland Management Specialist. Authors Date Approval Date Dr. John Lacey 02/28/2005 Loretta J. Metz 03/19/2005 Maxine Rasmussen, Area RMS, Glasgow, MT Jon Siddoway, Area RMS, Great Falls, MT Rick Bandy, Area RSS, Great Falls, MT Greg Snell, Area RSS, Glasgow, MT
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) Loretta Metz, Maxine Rasmussen, Jon Siddoway Contact for lead author Area Rangeland Management Specialist, Glasgow Area Office, MT Reference site used? No Date 05/04/2005 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
Careful examination will yield slight evidence of rills following a rainfall event in HCPC. If in Plant community A, careful examination will yield slight evidence of rills regardless of precipitation event. In HCPC and in plant community A, rill would be less than ½ inch deep, linear, but short in length. If in Plant community B, rills are readily observed; regularly spaced, ½ inch deep, linear and exceeding 1 foot but not exceeding 3 feet. -
Presence of water flow patterns:
Careful examination will yield slight evidence of water flow patterns following a rainfall event in HCPC. If in Plant community A, careful examination will yield slight evidence of water flow patterns regardless of precipitation event. If in Plant community B, water flow patterns are readily observed. -
Number and height of erosional pedestals or terracettes:
Pedestals or terracettes would essentially be nonexistent in HCPC. If in Plant community A, careful examination will yield occasional pedestals and terracettes approximately ¼ inch above the soil surface. If in Plant community B, pedestals and terracettes are frequent and ½ - ¾ inch above the soil surface. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Up to 10% of the soil surface is bare ground in HCPC & Plant community A. If in Plant Community B, 11 to 25% of the soil surface is bare ground. -
Number of gullies and erosion associated with gullies:
None. -
Extent of wind scoured, blowouts and/or depositional areas:
None. -
Amount of litter movement (describe size and distance expected to travel):
Some litter movement is evident following a rainfall event in HCPC. If in Plant community A, some litter movement is evident regardless of precipitation event. If in Plant community B, litter movement is readily observable. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Stability class anticipated to be 3 to 5. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
The surface layer is 1-7” thick and typically has loam, silt loam, gravelly loam or silty clay loam texture. Surface color ranges from dark grayish brown to dark brown. Soil organic matter ranges from 0.5-4%. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
In HCPC, 85-90% plant canopy and 75-80% basal cover with small gaps between plants should reduce raindrop impact and slow overland flow, providing increased time for infiltration to occur. Healthy, deep rooted native grasses enhance infiltration and reduce runoff. Infiltration rate is moderate to moderately slow. If in plant community A, 85-90% plant canopy and 75-80% basal cover with small gaps between plants will still reduce raindrop impact and decrease overland flow. If in plant community B, 30-60% plant canopy and 50-75% basal cover with moderate gaps between plants, intensifies raindrop impact and increases overland flow. The site tends to be more xeric as runoff increases. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
None. -
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:
HCPC: Tall and mid-stature, cool season bunch grasses = mid-stature warm season bunch grasses > mid-stature, cool season rhizomatous grasses> short stature, warm season rhizomatous grasses> shrubs > forbs. Plant community A: Mid-stature, cool season bunch grasses > mid-stature, cool season rhizomatous grasses> short stature, warm season rhizomatous > shrubs > forbs. Plant community B: Mid-stature cools season bunch grasses > mid-stature, cool season rhizomatous grasses > short stature, warm season rhizomatous grasses > shrubs > forbs. -
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Plant mortality and decadence very low in HCPC and Plant community A. In periods of drought, shrubs would exhibit decadence in the state 1 reference communities. -
Average percent litter cover (%) and depth ( in):
Litter cover is in contact with soil surface. Litter decreases in Plant community A to 40-50% and depth is reduced to 0.5 inch. Litter decreases to about 10% in Plant community B and is less than ¼ inch deep. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
800 - 1450 #/acre from Plant community B to HCPC. -
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:
Needleandthread, threadleaf sedge, Hood’s phlox, prickly pear, creeping juniper, fringed sagewort, blue grama. -
Perennial plant reproductive capability:
All species are capable of reproducing in HCPC and Plant community A. In Plant community B, plant seedlings will be weighed in favor of marginal and undesirable species. Replacement of desirable species will be very few.
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