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Ecological site R052XY005MT

Clayey-Steep (Cystp) Dry Grassland

Last updated: 7/09/2019
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.

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 occurs at or near the soil surface (Soller, 2001). Underlying the till is sedimentary bedrock largely consisting of Cretaceous shale, sandstone and mudstone (Vuke et al. 2007). It is commonly exposed on hillslopes, particularly along drainage ways. 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 mixed grass 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 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. Because 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 - Nassella viridula 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. Clayey Steep Dry Grassland is a moderately extensive ecological site occurring on most landscapes in MLRA 52. This ecological site occurs on hillslopes, badlands, and bluffs where clay content of the soil is greater than 35 percent. Slopes vary from 15 to 60 percent.

The distinguishing characteristics of this site are moderately steep to very steep slopes, a relatively well developed soil profile, and clayey textures in the upper 4 inches of soil. Soils are typically moderately deep to very deep (between 20 to 60 inches to bedrock), are derived from shale residuum or clayey till, and typically have an ochric epipedon. Textures in the upper 4 inches of soil are in the fine textural family and contains greater than 35 percent, but not more than 45 percent, clay. Sometimes the underlying horizons exhibit shrink swell characteristics such as slickensides. This site is typically nonacid, with pH values greater than 5.6 throughout the soil profile. In general, plant production is relatively good on this site and species diversity can be high. Characteristic vegetation is western wheatgrass (Pascopyrum smithii) and green needlegrass (Nassella viridula). Thickspike wheatgrass (Elymus lanceolatus) becomes more common in the northern extent of MLRA 52. The principal shrub on this site is silver sagebrush (Artemisia cana), which typically comprises 5 percent canopy cover or less.

Preliminary studies indicate that there may also be an acid variant of this site. This variant appears to exhibit retarded shrub growth, reduced cover of cool season bunchgrasses, and increased cover of creeping juniper and prairie sandreed. At this time, this variant cannot be consistently identified as a separate ecological site concept and further investigation is required.

Associated sites

R052XY001MT	Clayey (Cy) Dry Grassland Clayey Dry Grassland is adjacent to Clayey Steep on slopes of less than 15 percent. It typically occupies a summit position upslope from the Clayey Steep Dry Grassland ecological site.
R052XY131MT	Shallow Clay (Swc) Dry Grassland Shallow Clay Dry Grassland is adjacent to Clayey Steep where bedrock occurs near the soil surface. It typically occupies a backslope position similar to the Clayey Steep Dry Grassland ecological site.
R052XY007MT	Coarse Clay (Coc) Dry Grassland This site occurs on moderate to steeply sloping hillslopes adjacent to the Clayey Steep Dry grassland site. It is commonly in the same landscape positions but has different soil structure.

R052XY001MT

Clayey (Cy) Dry Grassland

Clayey Dry Grassland is adjacent to Clayey Steep on slopes of less than 15 percent. It typically occupies a summit position upslope from the Clayey Steep Dry Grassland ecological site.

R052XY131MT

Shallow Clay (Swc) Dry Grassland

Shallow Clay Dry Grassland is adjacent to Clayey Steep where bedrock occurs near the soil surface. It typically occupies a backslope position similar to the Clayey Steep Dry Grassland ecological site.

R052XY007MT

Coarse Clay (Coc) Dry Grassland

This site occurs on moderate to steeply sloping hillslopes adjacent to the Clayey Steep Dry grassland site. It is commonly in the same landscape positions but has different soil structure.

Similar sites

R052XY703MT	Clayey-Steep (Cystp) Dry Shrubland This site differs from Clayey Steep Dry Grassland in that annual temperatures are slightly warmer and it supports big sagebrush rather than silver sagebrush.
R052XY131MT	Shallow Clay (Swc) Dry Grassland This site differs from Clayey Steep Dry Grassland in that depth to bedrock is less than 20 inches.
R052XY007MT	Coarse Clay (Coc) Dry Grassland This site differs from Clayey Steep Dry Grassland in that the soil structure in the surface horizon is coarse granular rather than fine.

R052XY703MT

Clayey-Steep (Cystp) Dry Shrubland

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

R052XY131MT

Shallow Clay (Swc) Dry Grassland

This site differs from Clayey Steep Dry Grassland in that depth to bedrock is less than 20 inches.

R052XY007MT

Coarse Clay (Coc) Dry Grassland

This site differs from Clayey Steep Dry Grassland in that the soil structure in the surface horizon is coarse granular rather than fine.

Table 1. Dominant plant species

Tree	Not specified
Shrub	Not specified
Herbaceous	Not specified

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Physiographic features

Clayey 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 backslope positions on hillslopes, badlands, and bluffs. Slopes vary from 15 to 60 percent.

Figure 1. Figure 1 General distribution of the Clayey Steep Dry Grassland ecological site by mapunit extent

Table 2. Representative physiographic features

Landforms	(1) Till plain > Hillslope (2) Till plain > Bluff (3) Badlands
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 2. Monthly precipitation range

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Figure 3. 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 ecological 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

Soil series that best represent the central concept of this ecological site are Bascovy and Megonot. The Bascovy series is in the Haplusterts great group and the Megonot series is in the Haplustepts great group. Both of these soils are characterized by a surface horizon that lacks enough organic matter to have a mollic epipedon. The Megonot series has weakly developed underlying horizons that exhibit some shrink-swell properties. The Bascovy series has underlying horizons that exhibit strong shrink-swell characteristics evidenced by slickensides (USDA-NRCS 2016). The particle size family for both of these soils is fine, which means that the soils contain between 35 and 60 percent clay in the particle size control section. The soil minerology is smectitic. The soil moisture regime for these and all other 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 on this site are typically clay, silty clay, clay loam, or silty clay loam. The upper 4 inches of soil typically contains greater than 35 percent, but not more than 45 percent clay. The underlying horizons typically contain 35 to 60 percent clay and have clay, clay loam, or silty clay loam textures. Organic matter content in the surface horizon typically ranges from 1 to 2 percent, and moist colors vary from grayish brown (2.5Y 5/2) to dark grayish brown (2.5Y 4/2). Calcium carbonate equivalent is typically less than 15 percent throughout the soil profile. In the upper 20 inches, electrical conductivity is less than 4 and the sodium absorption ratio is less than 13. Soil pH class is moderately acid to slightly alkaline in the surface horizon and neutral to strongly alkaline in the subsurface horizons. The soil depth class for this site can be moderately deep (between 20 to 60 inches to bedrock) in places where bedrock is present 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. Lower horizons may contain 15 to 60 percent soft parafragments.

Table 4. Representative soil features

Parent material	(1) Residuum (2) Till
Surface texture	(1) Clay loam (2) Silty clay (3) Clay (4) Silty clay loam
Drainage class	Well drained
Soil depth	20 – 72 in
Available water capacity (0-40in)	3.5 – 4.7 in
Calcium carbonate equivalent (0-5in)	14%
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 Clayey 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 Clayey 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. American 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.) also 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 also experienced relatively frequent lightning-caused fires with estimated fire return intervals of 6-25 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 Clayey 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 more) 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). It can invade relatively undisturbed grasslands, reducing cover and production of native cool-season midgrasses (Heidinga and Wilson, 2002; Henderson and Naeth, 2005). Clayey 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. Land owners 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 cool-season rhizomatous grasses, mid-statured cool-season bunchgrasses, and short statured grasses. This state evolved under the combined influences of climate, grazing, and fire with climatic variation having the greatest influence on cover and production (Coupland, 1958, 1961; Biondini et al. 1998). In general, this state was resilient to grazing and fire, although these factors could influence species composition in localized areas.

Community Phase 1.1: Mixedgrass Phase
The reference plant community on this site is characterized by mid-statured cool-season rhizomatous grasses and mid-statured cool-season bunchgrasses. The most abundant species are western wheatgrass and green needlegrass. Thickspike wheatgrass may also be present, becoming abundant in the northern extent of this ecological site. Short-statured grasses such as prairie Junegrass (Koeleria macrantha) and blue grama (Bouteloua gracilis) are not abundant in this phase but are generally present at low cover. Needleleaf sedge (Carex duriuscula) and plains muhly (Muhlenbergia cuspidata) may also be present at low cover. Common forbs are American vetch (Vicia americana), and spiny, or Hood’s, phlox (Phlox hoodii). Shrubs and subshrubs are rare on this site, however, prairie, or fringed, 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*
Rhizomatous Wheatgrass 40%
Green Needlegrass 20%
Plains Muhly 5%
Blue Grama 5%
Prairie Junegrass 5%
Other Native Grasses 10%
Perennial Forbs 10%
Shrubs/Subshrubs 5%

Estimated Total Annual Production (lbs/ac)*
Low - 300
Representative Value - 550
High - 800
*Estimated based on current observation – subject to revision

Community Phase 1.2: At Risk Community Phase
In the At Risk Community Phase, mid-statured bunchgrasses, especially green needlegrass, have been nearly eliminated. Rhizomatous wheatgrasses are in decline and are in nearly equal proportion to shortgrasses. Shortgrasses such as prairie Junegrass, Sandberg bluegrass, and blue grama are increasing. Needleleaf sedge and prairie, or fringed, sagewort (Artemisia frigida) may also increase in this phase.

Community Phase Pathway 1.1a
Drought, improper grazing management, or a combination of these factors can shift the Mixedgrass Phase (1.1) to the At Risk Community Phase (1.2). These factors favor a decrease in cool-season midgrasses and an increase in shortgrasses (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 (approximately 3 years or more), 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 transitions to the Shortgrass State when cool-season midgrasses become rare and contribute little to production. Shortgrasses, particularly prairie Junegrass, Sandberg bluegrass, and 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 and 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 shortgrasses while mid-statured grasses have been eliminated or nearly so. Blue grama is common, but does not appear to dominate on clayey soils as it does on loamy soils. In some cases, prairie Junegrass will significantly increase (Clarke et al., 1947), but this requires further investigation. Reductions in stocking rates can reduce shortgrass cover and increase the cover of cool-season midgrasses, although this recovery may take decades (Dormaar and Willms, 1990; Dormaar et al, 1994).

Community Phase 2.1 Shortgrass Community Phase
In the Shortgrass Community Phase mid-statured grasses such as green needlegrass 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 and 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
A reduction in livestock grazing pressure alone may not be sufficient to reduce the cover of blue grama in the Shortgrass State (3) (Dormaar and Willms, 1990). Intensive management treatments may be necessary (Hart et al., 1985), but practices such as grazing land mechanical treatment 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.

Invaded State 3
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 seedbank 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 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. These species are very aggressive. They typically displace native species and dominate ecological function when they invade a site. Sometimes, these species can 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

Custom diagram

Standard diagram

More interactive model formats are also available. View Interactive Models

Supporting information

Inventory data references

No specific field data was available for this site. A review of the scientific literature was the primary source of information. One historical (417) plot for the Clayey Steep Dry Shrubland was available for comparison with available literature but the data were not used directly. Information for alternate states was obtained from professional experience and a review of the scientific literature. All community phases are considered provisional based the sources identified in the narratives associated with each community phase.

Other references

Adams, B.W., J. Richman, L. Poulin-Klein, K. France, D. Moisey, and R.L. McNeil. 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 135pp.

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.

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Contributors

Scott Brady
Stuart Veith

Approval

Scott Brady, 7/09/2019

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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