Natural Resources
Conservation Service
Ecological site R046XC598MT
Shallow Clay (SwC) RRU 46-C 13-19 PZ
Last updated: 7/19/2023
Accessed: 11/13/2024
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.
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.
Associated sites
| R046XC506MT |
Shallow (Sw) RRU 46-C 13-19 PZ |
|---|---|
| R046XC516MT |
Silty Steep (SiStp) RRU 46-C 13-19 PZ |
Similar sites
| R046XC506MT |
Shallow (Sw) RRU 46-C 13-19 PZ The Shallow site differs by having a different texture, and generally being over different parent materials/bedrock. |
|---|
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
Not specified |
| Herbaceous |
(1) Pseudoroegneria spicata |
Physiographic features
This ecological site can occur on nearly level to very steep uplands. It often occurs in complex with other ecological sites, particularly in rougher terrain. This site occurs on sedimentary plains, hills, and escarpments of all slopes and exposures and aspect sometimes becomes significant. Variations in plant community composition and production can result due to aspect. The amount of exposed rock outcrop tends to increase as slopes increase. Runoff and the potential for water erosion can be important features of this site.
Table 2. Representative physiographic features
| Landforms |
(1)
Plain
(2) Hill (3) Escarpment |
|---|---|
| Flooding frequency | None |
| Ponding frequency | None |
| Slope | 70% |
| Water table depth | 60 in |
| Aspect | Aspect is not a significant factor |
Climatic features
See Climatic Data Sheet for more details (Section II of the Field Office Technical Guide) or reference the following climatic web site: http://www.wrcc.sage.dri.edu/ .
Table 3. Representative climatic features
| Frost-free period (characteristic range) | 67-87 days |
|---|---|
| Freeze-free period (characteristic range) | 111-124 days |
| Precipitation total (characteristic range) | 15-17 in |
| Frost-free period (actual range) | 53-88 days |
| Freeze-free period (actual range) | 104-126 days |
| Precipitation total (actual range) | 14-19 in |
| Frost-free period (average) | 76 days |
| Freeze-free period (average) | 116 days |
| Precipitation total (average) | 17 in |
Figure 2. Monthly precipitation range
Figure 3. Monthly minimum temperature range
Figure 4. Monthly maximum temperature range
Figure 5. Monthly average minimum and maximum temperature
Figure 6. Annual precipitation pattern
Figure 7. Annual average temperature pattern
Climate stations used
-
(1) RAYNESFORD 2 NNW [USC00246902], Raynesford, MT
-
(2) STANFORD [USC00247864], Stanford, MT
-
(3) LEWISTOWN MUNI AP [USW00024036], Lewistown, MT
-
(4) ZORTMAN [USC00249900], Zortman, MT
-
(5) DENTON [USC00242347], Denton, MT
-
(6) HOBSON [USC00244193], Hobson, MT
Influencing water features
Soil features
These are clayey soils that are 10 to 20 inches deep to underlying shale or nearly impervious clays. They developed on alluvium or colluvium over residuum from semiconsolidated or consolidated shale. Texture varies between granular clay loam, silty clay loam, silty clay, sandy clay, or clay. Few roots penetrate deeper than 20 inches.
Table 4. Representative soil features
| Surface texture |
(1) Silty clay loam (2) Silty clay (3) Sandy clay |
|---|---|
| Drainage class | Well drained to somewhat excessively drained |
| Permeability class | Slow to very slow |
| Soil depth | 10 – 20 in |
| Available water capacity (0-40in) |
2 – 4 in |
| Electrical conductivity (0-40in) |
Not specified |
| Soil reaction (1:1 water) (0-40in) |
6.6 – 8.4 |
| Subsurface fragment volume <=3" (Depth not specified) |
5% |
| Subsurface fragment volume >3" (Depth not specified) |
5% |
Ecological dynamics
This site developed under Northern Rocky Mountain foothills climatic conditions, which included the natural influence of large herbivores and occasional fire. The plant community upon which interpretations are primarily based is the Historic Climax Plant Community (HCPC). The Historic Climax Plant Community is described as a reference to understand the original potential of this site, and is not considered to be the management goal for every acre of rangeland. The following descriptions should enable the landowner/ manager to better understand which plant communities occupy their land, and assist with setting goals for vegetation management. It can also be useful to understand the environmental and economic values of each plant community.
This site is considered moderately resilient to disturbance as it has only moderate soil limitations for plant growth. Changes may occur to the Historic Climax Plant Community due to management actions and/or climatic conditions. Under continued adverse impacts, a moderate decline in vegetative vigor and composition will occur. Under favorable vegetative management treatments, this site can more readily return to the Historic Climax Plant Community (HCPC).
Continual adverse impacts to the site over a period of years results in a departure from the HCPC, with a decrease of the taller, more palatable species such as bluebunch wheatgrass, plains muhly, and the taller needlegrasses. These plants will be replaced by Idaho fescue, western or thickspike wheatgrass, Sandberg bluegrass, plains reedgrass, threadleaf sedge, various increaser forbs, and mountain big sagebrush. Continued deterioration results in increased amounts of fringed sagewort, threeawns, and weedy forbs. Rubber rabbitbrush may also increase at some locations.
Plants that are not a part of the reference community that are most likely to invade are annuals,
broom snakeweed, and thistles. There are several noxious weeds that are also likely to invade this site including spotted knapweed, leafy spurge, dalmation toadflax, and sulphur cinquefoil.
State and transition model
Figure 8. State and Transition Model
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Click on state and transition labels to scroll to the respective text
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 4 submodel, plant communities
State 1
Tall and Medium Grasses, Forbs, Half-Shrub
Community 1.1
Tall and Medium Grasses, Forbs, Half-Shrub
This is the interpretive plant community and is considered to be the Historic Climax Plant Community (HCPC) for this site. This plant community contains a high diversity of tall and medium height, cool and warm season grasses (bluebunch wheatgrass, green or Columbia needlegrasses, thickspike or western wheatgrass and, plains muhly), and short grasses and sedges (Idaho fescue, Cusick bluegrass, Sandberg bluegrass, plains reedgrass, threadleaf and needleleaf sedge). There are abundant forbs (prairie clovers, dotted gayfeather) which occur in smaller percentages. Half shrubs such as winterfat should also be common. Shrubs such as mountain big sagebrush can also be present. This plant community is well adapted to the Northern Rocky Mountain foothills climatic conditions. The diversity in plant species allows for drought tolerance. Individual species can vary greatly in production depending on growing conditions (timing and amount of precipitation, and temperature). This plant community is well suited to managed livestock grazing and provides diverse habitat for many wildlife species. Plants on this site have strong, healthy root systems that allow production to increase significantly with favorable moisture conditions. This plant community provides for soil stability and a properly functioning hydrologic cycle. Abundant plant litter is available for soil building and moisture retention. Plant litter is properly distributed with very little movement off-site and natural plant mortality is very low. The soils associated with this site provide a limited soil-water-plant relationship.
Figure 9. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
| Plant type | Low (lb/acre) |
Representative value (lb/acre) |
High (lb/acre) |
|---|---|---|---|
| Grass/Grasslike | 935 | 1063 | 1190 |
| Forb | 110 | 125 | 140 |
| Shrub/Vine | 0 | 35 | 70 |
| Total | 1045 | 1223 | 1400 |
Table 6. Ground cover
| Tree foliar cover | 0% |
|---|---|
| Shrub/vine/liana foliar cover | 5-10% |
| Grass/grasslike foliar cover | 20-40% |
| Forb foliar cover | 1-5% |
| Non-vascular plants | 0-1% |
| Biological crusts | 0% |
| Litter | 0% |
| Surface fragments >0.25" and <=3" | 0% |
| Surface fragments >3" | 0% |
| Bedrock | 0% |
| Water | 0% |
| Bare ground | 0% |
Table 7. Soil surface cover
| Tree basal cover | 0% |
|---|---|
| Shrub/vine/liana basal cover | 0-2% |
| Grass/grasslike basal cover | 14-21% |
| Forb basal cover | 1-2% |
| Non-vascular plants | 0-1% |
| Biological crusts | 0% |
| Litter | 50-60% |
| Surface fragments >0.25" and <=3" | 0% |
| Surface fragments >3" | 5-15% |
| Bedrock | 0% |
| Water | 0% |
| Bare ground | 10-20% |
State 2
Medium and Short Grasses, Sedge, and Increaser Forbs
Community 2.1
Medium and Short Grasses, Sedge, and Increaser Forbs
Early stages of degradation, including non-prescribed grazing, will tend to change the HCPC to a community dominated by medium and short grasses and sedges such as Idaho fescue, thickspike/western wheatgrass, Sandberg bluegrass, threadleaf sedge, Cusick bluegrass, and prairie junegrass. Bluebunch wheatgrass can still be relatively abundant. Most of the othe taller and more palatable plants (tall needlegrasses, winterfat) will still be present but in smaller amounts. There may be an increase in the amount of some shrubs, particularly mountain big sagebrush. Palatable and nutritious forbs will be replaced by less desirable and more aggressive species such as fringed sagewort. This plant community will readily respond to improved grazing management, but a significant amount of time can be necessary to move it toward a higher successional stage and a more productive plant community similar to community 1. Biomass production and litter become slightly reduced on the site with Community 2 as the taller grasses become replaced by shorter ones. Evapotranspiration tends to increase, moisture retention is reduced, and soil surface temperatures increase. Some natural ecological processes will be altered. These plant communities provide for moderate soil stability. Increased amounts of bare ground can result in undesirable species invading. Common invaders can include spotted knapweed, leafy spurge, dalmation toadflax, and sulphur cinquefoil.
State 3
Shrub, Short and Mid Increaser Grasses, Fringed Sagewort, Increaser Forbs Cactus
Community 3.1
Shrub, Short and Mid Increaser Grasses, Fringed Sagewort, Increaser Forbs Cactus
With continued heavy disturbance, the site will become dominated by species such as mountain big sagebrush, short and medium increaser grasses such as Sandberg bluegrass, plains reedgrass, prairie junegrass, western or thickspike wheatgrass, and Idaho fescue, fringed sagewort, and increaser forbs such as scarlet globemallow and Hood’s phlox. There may still be remnant amounts of some of the late-seral species such as bluebunch wheatgrass and green/Columbia needlegrass present. The taller grasses will occur only occasionally, often under sagebrush plants. Palatable forbs will be mostly absent. Plains pricklypear cactus and rubber rabbitbrush may become common. Plant community 3 is often less productive than 1 or 2. The lack of litter and short plant heights result in higher soil temperatures, poor water infiltration rates, and higher evapotranspiration rates, thus eventually favoring species that are more adapted to drier conditions. These communities have lost many of the attributes of a healthy rangeland, including good infiltration, minimal erosion and runoff, nutrient cycling and energy flow. This plant community is the result of long-term, heavy, continuous grazing and/or annual, early spring seasonal grazing. Repeated spring grazing depletes stored carbohydrates, resulting in weakening and eventual death of the cool season tall and medium grasses. This plant community can occur throughout the pasture, on spot grazed areas, and around water sources where season-long grazing patterns occur. This community will respond positively to improved grazing management, but significant economic inputs along with a significant amount of time are usually required to move it toward a higher successional stage and a more productive plant community. Practices such as prescribed burning and brush management are generally needed, along with extended rest and prescribed grazing once the community has degraded to this point. There are limitations to using mechanical treatment on this site due to the shallow soils. Periodic wild fire will result in a community similar to number 3, but with a smaller component of big sagebrush for a few years. There may also be a slight decrease in the amount of fringed sagewort, depending on frequency, timing, and severity of the fire. However, these will soon return if there’s no change in grazing management.
State 4
Shrub, Half Shrubs, Weedy Forbs, Annuals, and Short Grasses
Community 4.1
Shrub, Half Shrubs, Weedy Forbs, Annuals, and Short Grasses
Further deterioration of community 3 results in a plant community dominated by mountain big sagebrush and undesirable plants such as fringed sagewort, broom snakeweed, plains pricklypear, weedy forbs (e.g., pussytoes and thistles), annuals such as cheatgrass and Japanese bromes and sixweeks fescue. Many increaser short grasses such as Sandberg bluegrass and plains reedgrass will be abundant. Frequently, a remnant population of climax species such as bluebunch wheatgrass will occur under sagebrush plants. Rubber rabbitbrush can be abundant in some locations. Plant community 4 produces less usable forage than the others described. The continuation of the downward trend and degradation of this site has resulted in higher soil surface temperatures, reduced water infiltration, and higher evapotranspiration. This has resulted in plant species that are more adapted to drier conditions, such as cactus. A thick canopy cover (e.g., 20% or more) of big sagebrush often results in precipitation being intercepted, thus not reaching the soil. Most of the attributes of a healthy rangeland, including good infiltration, minimal erosion and runoff, nutrient cycling and energy flow, have been lost. This community can respond positively to improved grazing management but it will take additional inputs to move it towards communities similar in production and composition to others that have been described. Once plants such as mountain big sagebrush become established, they are very difficult to remove and replace by grazing management alone. Additionally, the chances for success are significantly reduced. Practices such as prescribed burning or brush management can reduce the amount of sagebrush, as well as some of the other susceptible plant species. The potential for success depends on the composiiion of the rest of the plant community. Because of the shallow soils (and sometimes, steeper slopes) associated with this ecological site, other practices such as mechanical treatment or seeding are generally not feasible nor recommended.
Additional community tables
Table 8. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (lb/acre) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Shrub/Vine
|
||||||
| 1 | Shrubs and Half-shrubs | 0–70 | ||||
| Shrub, broadleaf | 2SB | Shrub, broadleaf | 0–70 | – | ||
| silver sagebrush | ARCAV2 | Artemisia cana ssp. viscidula | 0–70 | – | ||
| prairie sagewort | ARFR4 | Artemisia frigida | 0–70 | – | ||
| mountain big sagebrush | ARTRV | Artemisia tridentata ssp. vaseyana | 0–70 | – | ||
| rubber rabbitbrush | ERNAN5 | Ericameria nauseosa ssp. nauseosa var. nauseosa | 0–70 | – | ||
| winterfat | KRLA2 | Krascheninnikovia lanata | 0–70 | – | ||
| plains pricklypear | OPPO | Opuntia polyacantha | 0–1 | – | ||
|
Grass/Grasslike
|
||||||
| 2 | Grasses and Sedges | 935–1190 | ||||
| bluebunch wheatgrass | PSSP6 | Pseudoroegneria spicata | 440–980 | – | ||
| Idaho fescue | FEID | Festuca idahoensis | 55–210 | – | ||
| plains muhly | MUCU3 | Muhlenbergia cuspidata | 55–140 | – | ||
| green needlegrass | NAVI4 | Nassella viridula | 27–70 | – | ||
| western wheatgrass | PASM | Pascopyrum smithii | 27–70 | – | ||
| Cusick's bluegrass | POCU3 | Poa cusickii | 0–70 | – | ||
| Sandberg bluegrass | POSE | Poa secunda | 0–70 | – | ||
| prairie Junegrass | KOMA | Koeleria macrantha | 0–70 | – | ||
| Grass, perennial | 2GP | Grass, perennial | 0–70 | – | ||
| Columbia needlegrass | ACNEN2 | Achnatherum nelsonii ssp. nelsonii | 27–70 | – | ||
| needleleaf sedge | CADU6 | Carex duriuscula | 0–70 | – | ||
| threadleaf sedge | CAFI | Carex filifolia | 0–70 | – | ||
| plains reedgrass | CAMO | Calamagrostis montanensis | 0–70 | – | ||
| tufted wheatgrass | ELMA7 | Elymus macrourus | 27–70 | – | ||
| purple threeawn | ARPU9 | Aristida purpurea | 0–1 | – | ||
| Fendler's threeawn | ARPUF | Aristida purpurea var. fendleriana | 0–1 | – | ||
|
Forb
|
||||||
| 3 | Forbs | 110–140 | ||||
| common starlily | LEMO4 | Leucocrinum montanum | 0–70 | – | ||
| dotted blazing star | LIPU | Liatris punctata | 1–70 | – | ||
| desertparsley | LOMAT | Lomatium | 0–70 | – | ||
| spiny phlox | PHHO | Phlox hoodii | 0–70 | – | ||
| scarlet globemallow | SPCO | Sphaeralcea coccinea | 0–70 | – | ||
| American vetch | VIAM | Vicia americana | 0–70 | – | ||
| Forb, perennial | 2FP | Forb, perennial | 0–70 | – | ||
| prairie clover | DALEA | Dalea | 1–70 | – | ||
| lupine | LUPIN | Lupinus | 0–5 | – | ||
| deathcamas | ZIGAD | Zigadenus | 0–1 | – | ||
| larkspur | DELPH | Delphinium | 0–1 | – | ||
Interpretations
Animal community
Livestock Grazing Interpretations: Managed livestock grazing is suitable on this site as it has the potential to produce a limited amount of high quality forage. Grazing must be managed carefully on this site to be sure livestock drift onto the better, more productive sites is not excessive. Management objectives should include maintenance or improvement of the plant community.
Using shorter grazing periods and providing for adequate re-growth after grazing are recommended for plant maintenance, health, and recovery. Continual over stocking and season-long use of this site can be detrimental and will alter the plant composition and production over time. The result will be plant communities that resemble numbers 3 and 4, depending on how long this grazing management is used as well as other circumstances such as weather conditions and fire frequency.
Whenever Plant Community 2 (medium and short grasses) occurs, grazing management strategies that will prevent further degradation need to be implemented. This community is still stable, productive, and healthy provided it receives proper management. It will respond fairly quickly to improved grazing management, including increased growing season rest of key forage plants. Grazing management alone can usually move this back towards the potential / historic climax community.
Plant community 3 is the result of long-term, heavy, continuous grazing and/or annual, early spring seasonal grazing. Repeated heavy early spring grazing, especially during stem elongation (generally mid May through mid June), can also have detrimental affects on the taller, key forage species. Repeated spring grazing depletes stored carbohydrates, resulting in weakening and eventual death of the cool season tall and medium grasses. This plant community can occur throughout the pasture, on spot grazed areas, and around water sources where season-long grazing patterns occur.
Plant Communities 3 and 4 have a high percentage of aggressive, less-desirable species. Once these have become established, it is significantly more difficult using grazing management alone to restore the site to one that resembles the HCPC. The management objective at this point to implement a grazing strategy that will restore the stability and health of the site. Additional rest, sometimes for the growing season, or more probable for a full year or more, is often necessary for re-establishment of the desired species. There are limitations to using mechanical treatment on this site due to the shallow soils.
Calculating Safe Stocking Rates: Proper stocking rates should be incorporated into a grazing
management strategy that protects the resource, maintains or improves rangeland health, and is consistent with management objectives. Safe stocking rates will be based on useable forage production, and should consider ecological condition and trend of the site, and past grazing use history.
Calculations used to determine a safe stocking rate are based on the amount of useable forage available,
taking into account the harvest efficiency of the animal and the grazing strategy to be implemented. Average annual production must be measured or estimated to properly assess useable forage production and stocking rates.
The following is an example of how to calculate the recommended stocking rate. This example does not use production estimates from this specific ecological site. You will need to adjust the annual production values and run the calculations using total annual production values from the ecological sites encountered on each individual ranch/pasture. Before making specific recommendations, an on-site evaluation must be made.
Example of total annual production amounts by type of year:
Favorable years = 2200 lbs/acre
Normal years = 1480 lbs/acre
Unfavorable years = 1200 lbs/acre
It is recommended that on slopes of 30% or less, stocking rate should be derived from the total annual production pounds minus 500 pounds for residual dry matter and 25% harvest efficiency. On slopes over 30%, stocking rate is derived from total annual production pounds minus 800 pounds for residual dry matter and 25% harvest efficiency. Refer to the NRCS National Range and Pasture Handbook for a list of Animal Unit Equivalents.
Sample Calculations using Favorable Year production amounts:
< 30% slopes: AUM/AC = [(2200-500)(0.25)]/915 lbs/month for one AU = 0.46 AUM/AC
AC/AUM = (1.0 AU)/(0.46AUM/AC) = 2.2 AC/AUM
> 30% slopes: AUM/AC = [(2200-800)(0.25)]/915 lbs/month for one AU = 0.38 AUM/AC
AC/AUM = (1.0 AU)/(0.38 AU! M/AC) = 2.6 AC/AUM
NOTE: 915 lbs/month for one Animal Unit is used as the baseline for maintenance requirements. This equates to 30 lbs/day of air-dry forage (1200 lb cow at 2.5% of body weight).
Hydrological functions
The soils associated with this ecological site are generally in Hydrologic Soil
Group D. The infiltration rates for these soils will normally be slow to very slow. The runoff potential for
this site is moderate to high, depending on slope and ground cover/health. Runoff curve numbers generally range from 79 to 94.
Good hydrologic conditions exist on rangelands if plant cover (grass, litter, and brush canopy) is greater than 70%. Fair conditions exist when cover is between 30 and 70%, and poor conditions exist when cover is less than 30%. Sites in high similarity to HCPC (Plant Communities 1 and 2) generally have enough plant cover and litter to optimize infiltration, minimize runoff and erosion, and have a good hydrologic condition. The deep root systems of the potential vegetation help maintain or increase infiltration rates and reduce runoff.
Sites in low similarity (Plant Communities 3 and 4) are generally considered to be in poor hydrologic condition as the majority of plant cover is from shallow-rooted species such as Sandberg bluegrass.
Erosion is minor for sites in high similarity. Rills and gullies should not be present. Water flow patterns, if present, will be barely observable. Plant pedestals are essentially non-existent. Plant litter remains in place and is not moved by erosion. Soil surfaces should not be compacted or crusted. Plant cover and litter helps retain soil moisture for use by the plants. Maintaining a healthy stand of perennial vegetation will optimize the amount of precipitation that is received. (Reference: Engineering Field Manual, Chapter 2 and Montana Supplement 4).
Recreational uses
This site provides some recreational opportunities for hiking,
horseback riding, big game and upland bird hunting. The forbs have flowers that appeal to photographers.
This site provides valuable open space and visual aesthetics. Caution should be used during wet weather
Wood products
None
Supporting information
Contributors
Robert Leinard; Barbara Gibbons; Loretta Metz; Peter Husby
Approval
Kirt Walstad, 7/19/2023
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) |
G. Petersen K. Walstad |
|---|---|
| Contact for lead author | grant.petersen@usda.gov |
| Date | 03/01/2020 |
| Approved by | Kirt Walstad |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
Rills are rarely present in the reference condition, if present will be short and inconspicuous on the steeper slopes -
Presence of water flow patterns:
Water flow patterns are rarely present in the reference condition but may be present on the steeper, south facing slopes when runoff exceeds infiltration. These patterns will be short and infrequent across gentle slopes and increasingly more common on steeper slopes. -
Number and height of erosional pedestals or terracettes:
Pedestals are extremely rare in the reference condition, if present will be on slopes greater than 25% and associated with waterflow patterns. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground is 10-20%. It consists of small, randomly scattered patches. -
Number of gullies and erosion associated with gullies:
Gullies are not present in the reference condition. -
Extent of wind scoured, blowouts and/or depositional areas:
Wind scoured, or depositional areas are not evident in the reference condition. -
Amount of litter movement (describe size and distance expected to travel):
Litter movement is not evident in the reference condition. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
The average soil stability rating is 4-6 under plant canopies and plant interspaces. The A horizon is 2-4 inches thick. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Soil Structure at the surface is typically weak fine to strong fine granular. A Horizon should be 2-4 inches thick with color, when wet, typically ranging in Value of 5 or less and Chroma of 3 or less.
Local geology may affect color, it is important to reference the Official Series Description (OSD) for characteristic range. https://soilseries.sc.egov.usda.gov/osdname.aspx -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Infiltration of the Shallow Clay ecological site is slow to very slow. This site is well drained. An even distribution of mid stature grasses (75-80%), cool season bunchgrasses (10-15%) along with rhizomatous grass (<5%), forbs (5-10%), and shrubs (0-3%) -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
A compaction layer is not present in the reference condition. Soil profile may contain an abrupt transition to an Argillic horizon which can be misinterpreted as compaction, however, the soil structure will be fine to medium subangular blocky, where a compaction layer will be platy or structureless (massive). -
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:
Mid-statured, cool season, perennial bunchgrasses (Primarily bluebunch wheatgrass and green needlegrass)Sub-dominant:
shortgrass grasses/grasslikes (needle and thread, prairie Junegrass) ≥ forbs > rhizomatous grasses > ShrubsOther:
Additional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Mortality in herbaceous species is not evident. Species with bunch growth forms may have some natural mortality in centers is 3% or less. -
Average percent litter cover (%) and depth ( in):
Total litter cover ranges from 50-60%. Most litter is irregularly distributed on the soil surface and is not at a measurable depth. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Average annual production is 1223. Low: 1045 High 1400. Production varies based on effective precipitation and natural variability of soil properties for this ecological site. -
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:
Potential invasive (including noxious) species (native and non-native). Invasive species on this ecological site include (but not limited to) annual brome spp., spotted knapweed, yellow toadflax, leafy spurge, crested wheatgrass
Native species such as Rocky Mountain juniper, ponderosa pine, Douglas fir, lupine, broom snakeweed, Sandberg bluegrass, etc. when their populations are significant enough to affect ecological function, indicate site condition departure. -
Perennial plant reproductive capability:
In the reference condition, all plants are vigorous enough for reproduction either by seed or rhizomes in order to balance natural mortality with species recruitment.
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