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Ecological site FX052X01X029

Limy-Steep (Lystp) Dry Grassland

Last updated: 7/10/2019
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 occurs 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, with the maximum glacial extent occurring 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 the 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 yet fully understood.
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 in the fact that 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 spend live 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: Schizachyrium scoparium Northwestern Great Plains Herbaceous Alliance (2.B.2.Nb.2.c)
• Association: Schizachyrium scoparium - Muhlenbergia cuspidata Herbaceous Vegetation (2.B.2.Nb.2.c)

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. Limy-Steep Dry Grassland is an 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 on steep linear or convex backslopes and shoulders.

The distinguishing characteristics of this site are moderately steep to very steep slopes and a relatively young, undeveloped soil profile, which is evidenced by increased calcium carbonate (lime) concentrations in the upper 5 inches and weak structure. Soils are typically moderately deep to very deep (more than 20 inches) and derived from glacial till. Soil surface textures fall within the fine-loamy textural family. Calcium carbonate equivalent in the surface 5 inches is 5 percent or more (as evidenced by strong or violet effervescence) in the upper 5 inches and commonly increases with depth. Characteristic vegetation is plains muhly (Muhlenbergia cuspidata), needle and thread (Hesperostipa comata), and threadleaf sedge (Carex filifolia). Little bluestem (Schizachyrium scoparium) becomes common on this site in the eastern portion of its distribution.

Associated sites

FX052X01X030	Limy (Ly) Dry Grassland This site occurs on gentler slopes (less than 15 percent) adjacent to or upslope from the Limy-Steep Dry Grassland site. It is generally on shoulders or crests with a convex slope shape whereas the Limy-Steep site is in backslope positions with a convex slope shape.
FX052X01X040	Loamy-Steep (Lostp) Dry Grassland This site occurs on moderate to steeply sloping hillslopes adjacent to the Limy-Steep Dry Grassland site. It is generally in backslope positions with a linear or concave slope shape rather than a convex slope shape.
FX052X01X032	Loamy (Lo) Dry Grassland This site is generally adjacent to the Limy-Steep Dry Grassland site. It is most commonly on summits where the slope is less than 15 percent and the slope shape is linear or concave.

FX052X01X030

Limy (Ly) Dry Grassland

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

FX052X01X040

Loamy-Steep (Lostp) Dry Grassland

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

FX052X01X032

Loamy (Lo) Dry Grassland

This site is generally adjacent to the Limy-Steep Dry Grassland site. It is most commonly on summits where the slope is less than 15 percent and the slope shape is linear or concave.

Similar sites

FX052X03X029	Limy-Steep (Lystp) Dry Shrubland This site differs from Limy-Steep Dry Grassland in that it has slightly warmer annual temperatures and supports big sagebrush rather than silver sagebrush.
FX052X01X040	Loamy-Steep (Lostp) Dry Grassland This site differs from Limy-Steep Dry Grassland in that soils contain less than 5 percent calcium carbonate in the upper 5 inches (as evidenced by lack of effervescence).
FX052X01X030	Limy (Ly) Dry Grassland This site differs from Limy-Steep Dry Grassland in that slopes are less than 15 percent.

FX052X03X029

Limy-Steep (Lystp) Dry Shrubland

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

FX052X01X040

Loamy-Steep (Lostp) Dry Grassland

This site differs from Limy-Steep Dry Grassland in that soils contain less than 5 percent calcium carbonate in the upper 5 inches (as evidenced by lack of effervescence).

FX052X01X030

Limy (Ly) Dry Grassland

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

Table 1. Dominant plant species

Tree	Not specified
Shrub	Not specified
Herbaceous	Not specified

Legacy ID

R052XY029MT

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Physiographic features

Limy-Steep Dry Grassland is a common ecological site occurring across the till plains and moraines of MLRA 52. This site is typically found on shoulder and backslope positions on moraines, bluffs, and hillslopes. These areas have high runoff potential and drier conditions compared to adjacent sites. Consequently, soil development is weaker, plant production is lower, and soil organic matter is less. Slopes vary from 15 to 60 percent.

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

Table 2. Representative physiographic features

Hillslope profile	(1) Backslope (2) Shoulder
Landforms	(1) Till plain > Moraine (2) Till plain > Hillslope
Elevation	610 – 1,180 m
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)	305 mm

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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 site is not influenced by a ground-water table or other soil hydrology. Moisture loss through potential evapotranspiration exceeds precipitation for the majority of the growing season. Additional moisture loss occurs as runoff due to the steep slopes. With the exception of May and June, the site is generally in a state of moisture deficit.

Soil features

The Hillon series is the soil that best represents the central concept for this ecological site, but only when it occurs on slopes less than 15 percent. This concept occurs on more than 450,000 acres of MLRA 52 but Hillon soil also occurs on the Limy Dry Shrubland ecological site. Hillon is in the Ustorthents great group and is characterized by a surface horizon that lacks enough organic matter to have a mollic epipedon and by little soil development in the subsurface horizons. It is in the fine-loamy family, meaning it contains between 18 and 35 percent clay in the particle-size control section, and has mixed minerology. The typical parent material, for this series is calcareous glacial till, but this ecological site may also occur on soils derived from glaciofluvial deposits, or till over residuum. The soil moisture regime for this 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 in this site are most frequently loam or clay loam and typically contain between 18 to 35 percent clay. The underlying horizons typically contain 18 to 40 percent clay and also have loam, clay loam, or clay textures. Organic matter content in the surface horizon typically ranges from 1 to 2 percent, and moist colors vary from olive brown (2.5Y 4/3) to very dark grayish brown (2.5Y 3/2). Calcium carbonate equivalent in the upper 5 inches of soil is 5 percent or more and typically increases with depth. In the upper 20 inches, electrical conductivity is less than 4 and the sodium absorption ratio is less than 13. Soil pH is slightly to moderately alkaline in the surface horizon and moderately to strongly alkaline in the subsurface horizons. The soil depth class for this is site can be moderately deep (between 20 to 40 inches to bedrock) in places where bedrock is present but is typically very deep. Content of coarse fragments is less than 35 percent in the upper 20 inches of soil and 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	51 – 183 cm
Available water capacity (0-101.6cm)	14.99 – 17.53 cm
Calcium carbonate equivalent (0-12.7cm)	5 – 15%
Electrical conductivity (0-50.8cm)	0 – 3 mmhos/cm
Sodium adsorption ratio (0-50.8cm)	0 – 12
Soil reaction (1:1 water) (0-101.6cm)	7.4 – 9
Subsurface fragment volume <=3" (0-50.8cm)	0 – 34%
Subsurface fragment volume >3" (0-50.8cm)	0 – 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 Limy-Steep provisional ecological site in MLRA 52 Dry Grassland consists of three states: The Reference State (1.0), the Altered State (2.0), and the Invaded State (3.0). Plant communities associated with the Limy-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). When cool-season graminoids are dominate, annual production is highly dependent upon mid- to late-spring precipitation (Heitschmidt and Vermeire, 2005; Anderson, 2006). In the eastern portion of MLRA 52, the Limy-Steep ecological site commonly supports a significant amount of the warm-season bunchgrass, little bluestem. It is believed that this is due to increased precipitation later in the growing season.

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. 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 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 Limy-Steep ecological site. It is believed that the frequency and intensity of fire would be less than that of adjacent sites due to the broken topography and sparser vegetation. Further investigation of fire dynamics is needed to better assess this.

Drought or 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). Extended periods of drought or long-term improper grazing can eventually reduce threadleaf sedge as well as mid-statured grasses and shift the species composition of this community to one dominated by shortgrasses, such as blue grama and Sandberg bluegrass (Coupland, 1958, 1961).

Due to the increased concentration of calcium carbonate near the soil surface, the weakly developed soil profile, and steep slopes, this ecological site is 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). Limy-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 and threadleaf sedge (Carex filifolia), a deep-rooted densely tufted sedge. 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, it was resilient to grazing and fire, although fire dynamics are not well understood on this site.

Phase 1.1: Plains Muhly - Needle and Thread - Threadleaf Sedge Phase
The reference plant community on this site is plains muhly, needle and thread, and threadleaf sedge. Rhizomatous wheatgrass species are uncommon on this site, generally less than 10 percent of total species composition. Prairie Junegrass (Koeleria macrantha) is common on this site, although cover and production is low. The mat-forming, warm-season perennial grass blue grama commonly occurs in this phase but rarely comprises more than 5 percent of the plant community. The warm-season bunchgrass little bluestem (Schizachyrium scoparium) appears on this site around the Bear Paw Mountains near Havre. It begins to increase moving eastward down the Milk River valley and eventually becomes widespread in central Phillips and Valley Counties. Where present, it occurs in large uniform patches that encompass approximately 10 to 25 percent of the site. Common forbs are spiny phlox (Phlox hoodii) and hairy false goldenaster (Heterotheca villosa). Shrubs and subshrubs are rare on this site; however, the subshrubs prairie sagewort (Artemisia frigida) and broom snakeweed (Gutierrezia sarothrae) can occur at low cover. Lesser spikemoss (Selaginella densa), also known as dense clubmoss, is typically absent on this site. The approximate species composition of the reference plant community is as follows:

Percent composition by weight*
Plains Muhly 20%
Needle and Thread 20%
Threadleaf Sedge 20%
Prairie Junegrass 1-5%
Blue Grama 1-5%
Little Bluestem 0-20%
Other Native Grasses 1-15%
Perennial Forbs 5-10%
Shrubs/Subshrubs 0-5%

Estimated Total Annual Production (lbs/ac)*
Low - 325
Representative Value - 500
High - 675
* Estimated based on current data – subject to revision

Phase 1.2: At Risk Community Phase
The At Risk Community Phase is characterized by a prairie Junegrass–threadleaf sedge plant community. Shortgrasses such as blue grama and Sandberg bluegrass (Poa secunda) have moderate cover and are increasing while needle and thread is reduced to low cover. Other shortgrass species that increase in this phase include prairie Junegrass and Sandberg bluegrass. Bare ground increases in extent, making the site more susceptible to erosion by wind and water.

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
The Reference State (1) transitions to the Altered State (2) when mid-statured graminoids become rare and contribute little to production. Shortgrasses, particularly the warm-season, mat-forming blue grama, dominate the plant community. Threadleaf sedge cover is reduced, and its vigor is low. 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).

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: Altered State
The Altered State (shortgrass state) consists of two community phases. 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 while vigor and production of threadleaf sedge are declining. When little bluestem is present, the Blue Grama – Little Bluestem Phase (2.2) may develop under certain conditions.

Phase 2.1: Shortgrass Community Phase
In the Shortgrass Community Phase, plains muhly and needle and thread have been largely eliminated and replaced by short-statured species, such as blue grama and Sandberg bluegrass. Threadleaf sedge has been reduced to a subdominant or minor component with declining vigor and production. Prairie sagewort may also increase in this phase. There is a high amount of bare ground, and erosional patterns and plant pedestaling are evident.

Phase 2.2: Blue Grama - Little Bluestem Community Phase
In areas where little bluestem is present, the Blue Grama – Little Bluestem Phase (2.2) may develop under certain conditions. Typically, little bluestem is regarded as desirable forage for cattle; however in MLRA 52, this grass is only palatable for a very short time. Pastures are commonly grazed in late summer or fall when little bluestem is mature and unpalatable. Under such conditions, livestock tend to avoid little bluestem. This combined with improper grazing management may result in the Blue Grama – Little Bluestem Phase. Dynamics of this phase are not well understood and require further investigation.

Transition T2A
The Altered State (2) transitions to the Invaded State (3) when aggressive perennial grasses or noxious weeds invade the Altered 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 (3) (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, structural complexity, and soil quality 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

Data for this provisional ecological site was obtained from a total of 4 plots ranging from Tier 1 to Tier 3 intensity. The Reference State (1) was represented by one Tier 3, one Tier 2, and two Tier 1 plots. No other community phases were supported with quantitative data analysis. 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.

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Contributors

Scott Brady
Stuart Veith

Approval

Scott Brady, 7/10/2019

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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