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Ecological site R052XY040MT

Loamy-Steep (Lostp) Dry Grassland

Last updated: 7/11/2019
Accessed: 11/21/2024

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General information

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.

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Figure 1. Mapped extent

Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.

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

This provisional ecological site occurs in the Dry Grassland climatic zone of MLRA 52. Figure 1 illustrates the distribution of this ecological site based on current data. This map is approximate, is not intended to be definitive, and may be subject to change. Loamy Steep Dry Grassland is a moderately extensive ecological site occurring on most landscapes in MLRA 52. It occurs on hillslopes, till plains, and bluffs 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. Characteristic vegetation is needle and thread (Hesperostipa comata), western wheatgrass (Pascopyrum smithii), and needleleaf sedge (Carex duriuscula).

Associated sites

R052XY032MT	Loamy (Lo) Dry Grassland This site is generally adjacent to Loamy Steep Dry Grassland. It is most commonly on summits where slopes are less than 15 percent and linear or concave in shape.
R052XY029MT	Limy-Steep (Lystp) Dry Grassland This site occurs on moderate to steeply sloping hillslopes adjacent to Loamy Steep Dry Grassland. It is generally in backslope positions with a convex slope shape rather than a linear or concave slope shape.
R052XY030MT	Limy (Ly) Dry Grassland This site occurs on gentler slopes (less than 15 percent) upslope from Loamy Steep Dry Grassland. It is generally on shoulders or crests with a convex slope shape whereas the Loamy Steep site is in backslope positions with a linear or concave slope shape.

R052XY032MT

Loamy (Lo) Dry Grassland

This site is generally adjacent to Loamy Steep Dry Grassland. It is most commonly on summits where slopes are less than 15 percent and linear or concave in shape.

R052XY029MT

Limy-Steep (Lystp) Dry Grassland

This site occurs on moderate to steeply sloping hillslopes adjacent to Loamy Steep Dry Grassland. It is generally in backslope positions with a convex slope shape rather than a linear or concave slope shape.

R052XY030MT

Limy (Ly) Dry Grassland

This site occurs on gentler slopes (less than 15 percent) upslope from Loamy Steep Dry Grassland. It is generally on shoulders or crests with a convex slope shape whereas the Loamy Steep site is in backslope positions with a linear or concave slope shape.

Similar sites

R052XY714MT	Loamy-Steep (Lostp) Dry Shrubland This site differs from Loamy Steep Dry Grassland in that it has slightly warmer annual temperatures and supports big sagebrush rather than silver sagebrush.
R052XY032MT	Loamy (Lo) Dry Grassland This site differs from Loamy Steep Dry Grassland in that slopes are less than 15 percent.
R052XY029MT	Limy-Steep (Lystp) Dry Grassland This site differs from Loamy Steep Dry Grassland in that soils contain 5 percent or greater calcium carbonate in the upper 5 inches (as evidenced by strong or violent effervescence).

R052XY714MT

Loamy-Steep (Lostp) Dry Shrubland

This site differs from Loamy Steep Dry Grassland in that it has slightly warmer annual temperatures and supports big sagebrush rather than silver sagebrush.

R052XY032MT

Loamy (Lo) Dry Grassland

This site differs from Loamy Steep Dry Grassland in that slopes are less than 15 percent.

R052XY029MT

Limy-Steep (Lystp) Dry Grassland

This site differs from Loamy Steep Dry Grassland in that soils contain 5 percent or greater calcium carbonate in the upper 5 inches (as evidenced by strong or violent effervescence).

Table 1. Dominant plant species

Tree	Not specified
Shrub	Not specified
Herbaceous	Not specified

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Physiographic features

Loamy Steep Dry Grassland is a moderately extensive ecological site occurring across the till plains and moraines of MLRA 52. The majority of MLRA 52 is covered by a broad till plain, and this ecological site largely occurs where the till plain has been dissected by streams or rivers. This site is typically in linear or concave backslope positions on bluffs, moraines, and hillslopes. Slopes vary from 15 to 60 percent.

Figure 2. Figure 1. General distribution of the Loamy Steep Dry Grassland ecological site by map unit extent

Table 2. Representative physiographic features

Hillslope profile	(1) Backslope
Landforms	(1) Till plain > Hillslope (2) Till plain > Moraine
Elevation	2,000 – 3,870 ft
Slope	15 – 60%
Aspect	Aspect is not a significant factor

Climatic features

The Brown Glaciated Plains is a semi-arid region with a temperate continental climate that is characterized by frigid winters and warm to hot summers (Cooper et al., 2001). The average frost-free period for this ecological site is 120 days. The majority of precipitation occurs as steady, soaking, frontal system rains in late spring to early summer. Summer rainfall comes mainly from convection thunderstorms that typically deliver scattered amounts of rain in intense bursts. These storms may be accompanied by damaging winds and large-diameter hail and result in flash flooding along low-order streams. Severe drought occurs on average in 2 out of 10 ten years. Annual precipitation ranges from 10 to 14 inches, and 70 to 80 percent of this occurs during the growing season (Cooper et al., 2001). Extreme climatic variations, especially droughts, have the greatest influence on species cover and production (Coupland, 1958, 1961; Biondini et al., 1998).

During the winter months, the western half of MLRA 52 commonly experiences chinook winds, which are strong west to southwest surface winds accompanied by abrupt increases in temperature. The chinook winds are strongest on the western boundary of the MLRA near the Rocky Mountain foothills and decrease eastward. In addition to producing damaging winds, prolonged chinook episodes can result in drought or vegetation kills due to the reaction of plants to a “false spring” (Oard, 1993).

Table 3. Representative climatic features

Frost-free period (average)	120 days
Freeze-free period (average)	140 days
Precipitation total (average)	12 in

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Figure 3. Monthly precipitation range

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Figure 4. Monthly average minimum and maximum temperature

Climate stations used

(1) CARTER 14 W [USC00241525], Floweree, MT
(2) CHESTER [USC00241692], Chester, MT
(3) TIBER DAM [USC00248233], Chester, MT
(4) HARLEM [USC00243929], Harlem, MT
(5) MALTA 7 E [USC00245338], Malta, MT
(6) TURNER 11N [USC00248415], Turner, MT
(7) CONRAD [USC00241974], Conrad, MT
(8) SHELBY [USC00247500], Shelby, MT
(9) GLASGOW [USW00094008], Glasgow, MT
(10) HAVRE CITY CO AP [USW00094012], Havre, MT

Influencing water features

This is a dry upland site and the water budget is normally contained within the soil profile. During intense precipitation events, precipitation rates frequently exceed infiltration rates. Water is typically delivered downslope via surface runoff. Moisture loss through evapotranspiration exceeds precipitation for the majority of the growing season. Soil moisture levels are greatest in May and June but rarely reach field capacity in the upper 40 inches. Soil moisture is the primary limiting factor for plant production on this ecological site.

Soil features

The soil series that best represent the central concept of this ecological site are Joplin and Kevin soils. These soils are in the Argiustolls great group. They have a relatively dark mollic epipedon and an underlying argillic horizon where clay has accumulated through weathering. Both are fine-loamy and have mixed minerology. The soil moisture regime for these and all soils in this ecological site concept is ustic bordering on aridic, which means that the soils are moist in some or all parts for either 180 cumulative days or 90 consecutive days during the growing season but are dry in some or all parts for over 90 cumulative days. These soils have a frigid soil temperature regime (Soil Survey Staff, 2014).

Surface textures found in this site are typically loam or clay and contain 18 to 35 percent clay. Underlying horizons typically, but not always, have an argillic horizon that contains between 18 and 45 clay, depending on the soil series. Organic matter in the surface horizon typically ranges from 1.5 to 3 percent. Moist colors vary from brown (10YR 4/3) to very dark grayish brown (10YR 3/2). Depth to secondary carbonates is typically between 5 and 15 inches below the soil surface. The upper 5 inches of these soils does not typically react with hydrochloric acid and has a calcium carbonate equivalent, if present at all, of less than 5 percent. The soil depth class for this site can be moderately deep (more than 20 inches to bedrock) where bedrock occurs but is typically very deep (greater than 60 inches to bedrock). Content of coarse fragments is less than 35 percent in the upper 20 inches of soil and is typically less than 15 percent.

Table 4. Representative soil features

Parent material	(1) Till (2) Glaciofluvial deposits
Surface texture	(1) Loam (2) Clay loam
Drainage class	Well drained
Soil depth	20 – 72 in
Available water capacity (0-40in)	5.7 – 7 in
Calcium carbonate equivalent (0-5in)	4%
Electrical conductivity (0-20in)	3 mmhos/cm
Sodium adsorption ratio (0-20in)	12
Soil reaction (1:1 water) (0-40in)	5.6 – 9
Subsurface fragment volume <=3" (0-20in)	34%
Subsurface fragment volume >3" (0-20in)	34%

Ecological dynamics

The information in this ecological site description, including the state-and-transition model (STM), was developed based on historical data, current field data, professional experience, and a review of the scientific literature. As a result, all possible scenarios or plant species may not be included. Key indicator plant species, disturbances, and ecological processes are described to inform land management decisions.

The Loamy Steep provisional ecological site in MLRA 52 Dry Grassland consists of three states: The Reference State (1.0), the Shortgrass State (2.0), and the Invaded State (3.0). Plant communities associated with the Loamy Steep ecological site evolved under the combined influences of climate, grazing, and fire. Extreme climatic variability results in frequent droughts, which have the greatest influence on the relative contribution of species cover and production (Coupland, 1958, 1961; Biondini et al., 1998). Due to the dominance of cool-season graminoids, annual production is highly dependent upon mid- to late-spring precipitation (Heitschmidt and Vermeire, 2005; Anderson, 2006).

Native grazers also shaped these plant communities. Bison (Bison bison) were the dominant historic grazer, but pronghorn (Antilocapra americana), elk (Cervus canadensis), and deer (Odocoileus spp.) were also common. Additionally, small mammals such as prairie dogs (Cynomys spp.) and ground squirrels (Urocitellus spp.) influenced this plant community (Salo et al., 2004). Grasshoppers and periodic outbreaks of Rocky Mountain locusts (Melanoplus spretus; Lockwood, 2004) also played an important role in the ecology of these communities.

The historic ecosystem experienced relatively frequent lightning-caused fires with estimated fire return intervals of 6 to 25 years (Bragg, 1995). Historically, Native Americans also set frequent fires. The majority of lightning-caused fires occurred in July and August, whereas Native Americans typically set fires during spring and fall to correspond with the movement of bison (Higgins, 1986). Generally, the mixedgrass ecosystem is resilient to fire and the historic fire return interval had neutral or slightly positive effects on the plant community (Vermeire et al., 2011, 2014). However, studies have shown that shorter fire return intervals can have a negative effect, shifting species composition toward warm-season short-statured grasses (Shay et al., 2001; Smith and McDermid, 2014). It is not known how significant fire was on the Loamy Steep ecological site. It is believed that the frequency of fire would be less than that of adjacent sites due to the broken topography but further investigation of fire dynamics is needed to better assess this.

Improper grazing of this site can result in a reduction in the cover of the mid-statured bunchgrasses and an increase in blue grama (Smoliak et al., 1972; Smoliak, 1974). Improper grazing practices include any practices that do not allow sufficient opportunity for plants to physiologically recover from a grazing event or multiple grazing events within a given year and/or that do not provide adequate cover to prevent soil erosion over time. These practices may include, but are not limited to, overstocking, continuous grazing, and/or inadequate seasonal rotation moves over multiple years. Periods of extended drought (approximately 3 years or greater) can reduce mid-statured cool-season grasses, shifting the species composition of this community to one dominated by blue grama (Coupland, 1958, 1961). Further degradation of the site due to improper grazing can result in a community dominated by shortgrasses such as blue grama and Sandberg bluegrass.

Due to the steep slopes, this ecological site is generally not suitable for cropland. In general, this site has remained intact, although many acres have been invaded by aggressive, perennial introduced grasses, particularly crested wheatgrass. Seeding of introduced grasses, particularly crested wheatgrass (Agropyron cristatum), was a common practice in eroded and abandoned agricultural areas after the droughts of the 1930s (Rogler and Lorenz, 1983). Crested wheatgrass is a highly drought-tolerant and competitive cool-season, perennial bunchgrass (DeLuca and Lesica, 1996). Crested wheatgrass can invade relatively undisturbed grasslands, reducing cover and production of native cool-season midgrasses (Heidinga and Wilson, 2002; Henderson and Naeth, 2005). Loamy Steep ecological sites adjacent to these seeded areas are particularly prone to invasion.

The STM diagram suggests possible pathways that plant communities on this site may follow as a result of a given set of ecological processes and management. The site may also support states not displayed in the STM diagram. Landowners and land managers should seek guidance from local professionals before prescribing a particular management or treatment scenario. Plant community responses vary across this MLRA due to variability in weather, soils, and aspect. The reference community phase may not necessarily be the management goal. The lists of plant species and species composition values are provisional and are not intended to cover the full range of conditions, species, and responses for the site. Species composition by dry weight is provided when available and is considered provisional based on the sources identified in the narratives associated with each community phase.

State 1: Reference State
The Reference State contains two community phases characterized by mid-statured bunchgrasses, sedges, and rhizomatous wheatgrasses. This state evolved under the combined influences of climate, grazing, and fire, with climatic variation having the greatest influence on cover and production. In general, this state was resilient to grazing and fire, although fire dynamics are not well understood on this site. Lesser spikemoss, also known as dense clubmoss (Selaginella densa), is common on this site; however, its abundance may vary greatly from site to site without discernable reason.

Community Phase 1.1: Mixedgrass Phase
The reference plant community on this site is characterized by mid-statured bunchgrasses, sedges, and rhizomatous wheatgrasses. By far, the most abundant bunchgrass is the cool-season needle and thread grass which may constitute up to 50 percent of the total annual production. Plains muhly is also common on this site although its cover is typically low. Green needlegrass (Nassella viridula) may occur where moisture conditions are more favorable due to soil texture or microrelief. Sedges, particularly needleleaf sedge (Carex duriuscula), are common on this site and may contribute significantly to total production. The rhizomatous wheatgrasses may include western wheatgrass or thickspike wheatgrass (Elymus lanceolatus), with thickspike more common in the northern extent of this site. The mat-forming, warm-season perennial grass blue grama is the most common shortgrass in this phase although prairie Junegrass (Koeleria macrantha) is also common. Shortgrasses rarely comprise more than 5 percent of the plant community. Common forbs are Missouri goldenrod (Solidago missouriensis), spiny phlox (Phlox hoodii), and silvery scurfpea (Pediomelum argophyllum). Shrubs and subshrubs are rare on this site; however, prairie sagewort (Artemisia frigida) and silver sagebrush (Artemisia cana) can occur at low cover. The approximate species composition of the reference plant community is as follows:

Percent composition by weight*
Needle and Thread 40%
Sedge spp. 20%
Rhizomatous Wheatgrasses 10%
Blue Grama 5%
Other Native Grasses 10%
Perennial Forbs 10%
Shrubs/Subshrubs 5%

Estimated Total Annual Production (lbs/ac)*
Low - Insufficient data
Representative Value - 730
High - Insufficient data
* Estimated based on current data – subject to revision

Community Phase 1.2: At-Risk Community Phase
The At-Risk Community Phase is characterized by nearly equal proportions of shortgrasses and mid-statured grasses. Shortgrasses, such as blue grama and prairie Junegrass, are increasing in this phase while mid-statured grasses, such as needle and thread and western wheatgrass, are decreasing. Prairie sagewort may also increase in this phase. The amount of bare ground depends on the cover of clubmoss. When present, clubmoss commonly provides significant ground cover and may protect the soil surface from erosion; however, the dynamics of this species are not well understood.

Community Phase Pathway 1.1a
Drought, improper grazing management, or a combination of these factors can shift the reference community phase (1.1) to the At-Risk Community Phase (1.2). These factors favor an increase in blue grama and a decrease in midgrasses (Coupland, 1961).

Community Phase Pathway 1.2a
The At-Risk Community Phase (1.2) can return to the reference community phase (1.1) with normal or above-normal spring precipitation and proper grazing management.

Transition T1A
Prolonged drought, improper grazing practices, or a combination of these factors weaken the resilience of the Reference State (1) and drive its transition to the Shortgrass State (2). The Reference State (1) transitions to the Shortgrass State (2) when mid-statured grasses become rare and contribute little to production. Shortgrasses, particularly the warm-season, mat-forming blue grama, dominate the plant community.

Transition T1B
The Reference State (1) transitions to the Invaded State (3) when aggressive perennial grasses or noxious weeds invade the Reference State (1). Crested wheatgrass, in particular, is a concern when native plant communities are adjacent to seeded pastures. Exotic plant species dominate the site in terms of cover and production. Site resilience has been substantially reduced. In addition, other rangeland health attributes, such as reproductive capacity of native grasses (Henderson and Naeth, 2005) and soil quality (Smoliak and Dormaar, 1985; Dormaar et al., 1995), have been substantially altered from the Reference State.

State 2: Shortgrass State
The Shortgrass State consists of one community phase. The dynamics of this state are driven by long-term drought, improper grazing management, or a combination of these factors. The Shortgrass Community Phase (2.1) is dominated by short-statured grasses such as blue grama. Mid-statured grasses have been eliminated or nearly so, and their vigor and production are low. Once established, blue grama-dominated communities can alter soil properties and create conditions that resist establishment of other grass species (Dormaar and Willms, 1990’ Dormaar et al., 1994). Dense clubmoss may occur in some areas and constitute significant ground cover. Its dynamics are not well understood, and its abundance appears to vary greatly from site to site without discernable reason.

Community Phase 2.1: Shortgrass Community Phase
In the Shortgrass Community Phase, mid-statured grasses, such as needle and thread, and rhizomatous wheatgrasses have been largely eliminated and replaced by short-statured species, such as blue grama and prairie Junegrass. Prairie sagewort also becomes common in this phase.

Transition T2A
The Shortgrass State (2) transitions to the Invaded State (3) when aggressive perennial grasses or noxious weeds invade the Shortgrass State (2). Crested wheatgrass, in particular, is a concern when native plant communities are adjacent to seeded pastures. Exotic plant species dominate the site in terms of cover and production. Site resilience has been substantially reduced. In addition, other rangeland health attributes, such as reproductive capacity of native grasses (Henderson and Naeth, 2005) and soil quality (Smoliak and Dormaar, 1985; Dormaar et al., 1995), have been substantially altered from the Reference State.

Restoration Pathway R2A
Blue grama can resist displacement by other species (Dormaar and Willms, 1990; Laycock, 1991; Dormaar et al., 1994; Lacey et al., 1995). A reduction in livestock grazing pressure alone may not be sufficient to reduce the cover of blue grama in the Shortgrass State (2) (Dormaar and Willms, 1990). Intensive management treatments may be necessary (Hart et al., 1985), but practices such as mechanical treatment of grazing land and range seeding may not be possible on this site due to topography. Therefore, returning the altered state (2) to the Reference State (1) can require considerable energy and cost and may not be feasible within a reasonable amount of time.

State 3: Invaded State
The Invaded State (3) occurs primarily when aggressive, introduced perennial grasses invade adjacent native grassland communities. Crested wheatgrass, in particular, is a concern, especially when native plant communities are adjacent to seeded pastures. An estimated 20 million acres of crested wheatgrass have been planted in the western U.S. (Holechek, 1981). Crested wheatgrass produces abundant seeds that can dominate the seed bank of invaded grasslands (Henderson and Naeth, 2005), although crested wheatgrass cover decreases with increasing distance from seeded areas (Heidinga and Wilson, 2002). The early growth of crested wheatgrass allows this species to take advantage of early season soil moisture, which may result in competitive exclusion of native cool-season rhizomatous wheatgrasses and bunchgrasses, such as needle and thread and prairie Junegrass (Christian and Wilson, 1999; Heidinga and Wilson, 2002; Henderson and Naeth 2005). Once established, monocultures of crested wheatgrass can persist for at least 60 years (Krzic et al., 2000; Henderson and Naeth, 2005). Reduced soil quality (Dormaar et al., 1995), reduced plant species diversity, and simplified structural complexity (Henderson and Naeth 2005) result in a state that is substantially departed from the Reference State (1).

Noxious weeds such as leafy spurge are uncommon on this site but may also invade and displace native species. Although very aggressive, these species can sometimes be suppressed through intensive management (herbicide application, biological control, or intensive grazing management). Control efforts are unlikely to eliminate noxious weeds, but their density can be sufficiently suppressed so that species composition and structural complexity are similar to that of the Reference State (1). However, cessation of control methods will most likely result in recolonization of the site by the noxious species.

State and transition model

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Standard diagram

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Supporting information

Inventory data references

One high-intensity plot and 2 historical (417) plots were available for this provisional ecological site. These data represented the Reference State (1). No other community phases were supported with quantitative data analysis. Information for alternate states was obtained from professional experience and a review of the scientific literature. All community phases are considered provisional based these plots and the sources identified in the narratives associated with each community phase.

Other references

Adams, B.W., et al. 2013. Rangeland plant communities for the dry mixedgrass natural subregion of Alberta. Second approximation. Rangeland Management Branch, Policy Division, Alberta Environment and Sustainable Resource Development, Lethbridge, Pub. No. T/040.

Anderson, R.C. 2006. Evolution and origin of the central grassland of North America: Climate, fire, and mammalian grazers. Journal of the Torrey Botanical Society 133:626-647.

Baskin, J. M., and C.C. Baskin. 1981. Ecology of germination and flowering in the weedy winter annual grass Bromus japonicus. Journal of Range Management 34:369-372.

Biondini, M.E., and L. Manske. 1996. Grazing frequency and ecosystem processes in a northern mixed prairie, USA. Ecological Applications 6:239-256.

Biondini, M.E., B.D. Patton, and P.E. Nyren. 1998. Grazing intensity and ecosystem processes in a northern mixed-grass prairie, USA. Ecological Applications 8:469-479.

Bragg, T.B. 1995. The physical environment of the Great Plains grasslands. In: A. Joern and K.H. Keeler (eds.) The Changing Prairie, Oxford University Press, Oxford, pp. 49–81.

Branson, D.H., and G.A. Sword. 2010. An experimental analysis of grasshopper community responses to fire and livestock grazing in a northern mixed-grass prairie. Environmental Entomology 39:1441-1446.

Bylo, L.N., N. Koper, and K.A. Molloy. 2014. Grazing intensity influences ground squirrel and American badger habitat use in mixed-grass prairies. Rangeland Ecology and Management 67:247-254.

Christian, J.M., and S.D. Wilson. 1999. Long-term ecosystem impacts of an introduced grass in the Northern Great Plains. Ecology 80:2397-2407.

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Contributors

Scott Brady
Stuart Veith

Approval

Scott Brady, 7/11/2019

Acknowledgments

This provisional ecological site description could not have been completed without the contributions of Karen Newlon. She conducted an extensive literature review, which provided most of the background information for this project as well as many of the references. She also co-authored the Loamy and Thin Claypan Dry Grassland ecological sites previously prepared in MLRA 52.

A number of USDA-NRCS and USDI-BLM staff supported this project. Staff contributions are as follows:

Soil Concepts, Soils Information, and Field Descriptions
Charlie French, USDA-NRCS
Josh Sorlie, USDI-BLM

NASIS Reports, Data Dumps, and Soil Sorts
Bill Drummond, USDA-NRCS
Pete Weikle, USDA-NRCS

Peer Review and Beta Testing
Kirt Walstad, USDA-NRCS
Kyle Steele, formerly USDA-NRCS
Kelsey Molloy, USDA-NRCS
Rick Caquelin, USDA-NRCS
Josh Sorlie, USDI-BLM
BJ Rhodes, USDI-BLM

Editing
Ann Kinney, USDA-NRCS
Jenny Sutherland, USDA-NRCS

Quality Control
Jon Siddoway, USDA-NRCS

Quality Assurance
Stacey Clark, USDA-NRCS

Rangeland health reference sheet

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

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

Indicators

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

Dominant:

Sub-dominant:

Other:

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Perennial plant reproductive capability:

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