Natural Resources
Conservation Service
Ecological site R035XD418AZ
Clay Loam Bottom 7-11" p.z.
Accessed: 12/22/2024
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.
MLRA notes
Major Land Resource Area (MLRA): 035X–Colorado Plateau
AZ CRA 35.4 – Colorado Plateau Cold Sagebrush – Grasslands
Elevations range from 4200 to 5100 feet and precipitation averages 7 to 11 inches. Vegetation includes winterfat, fourwing saltbush, buckwheat species, needlegrass, bottlebrush squirreltail, Indian ricegrass, black grama, blue grama, sideoats grama, gyp dropseed, and galleta. The soil temperature regime is mesic and the soil moisture regime is typic aridic. This unit occurs within the Colorado Plateau Physiographic Province and is characterized by a sequence of flat to gently dipping sedimentary rocks eroded into plateaus, valleys and deep canyons. Sedimentary rock classes dominate the plateau with volcanic fields occurring for the most part near its margin.
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Atriplex canescens |
| Herbaceous |
(1) Pascopyrum smithii |
Physiographic features
This site occurs in a bottom position with no entrenched channel. Therefore, it benefits from run-in moisture from adjacent areas.
Table 2. Representative physiographic features
| Landforms |
(1)
Alluvial fan
(2) Flood plain |
|---|---|
| Flooding duration | Brief (2 to 7 days) to long (7 to 30 days) |
| Flooding frequency | Occasional to frequent |
| Ponding duration | Brief (2 to 7 days) to long (7 to 30 days) |
| Ponding frequency | Occasional to frequent |
| Elevation | 1,433 – 1,676 m |
| Slope | 0 – 2% |
| Aspect | Aspect is not a significant factor |
Climatic features
Winter-Summer moisture ratios are typically 70:30 on the west side of this LRU and shift to 60:40 on the east side. Late spring is usually the driest period, and early fall moisture can be sporadic. Summer rains fall June-September; moisture originates in the Gulf of Mexico and creates convective, usually brief, intense thunderstorms. Cool season moisture October-May tends to be frontal; it originates in the Pacific and the Gulf of California and falls in widespread storms with longer duration and lower intensity. Precipitation generally comes as snow December-February. Accumulations above 10 inches are not common, but can occur. Snow usually lasts 3-4 days, but can persist much longer. Summer daytime temperatures are commonly 95-100 F and, on occasion, exceed 105F. Winter air temperatures can regularly go below 15 F and have been recorded below -15 F.
Table 3. Representative climatic features
| Frost-free period (average) | 220 days |
|---|---|
| Freeze-free period (average) | 150 days |
| Precipitation total (average) | 279 mm |
Figure 2. Monthly precipitation range
Figure 3. Monthly average minimum and maximum temperature
Influencing water features
Soil features
Soils on this site are characterized as deep to any plant root restriction layer. The surface texture is generally a silty clay loam and the subsurface textures are silty clay loam, silt loam, or loam. The water erosion hazard is slight.
Typical taxonomic units include:
SSA623 Shivwits Area - MU 79 Tours;
SSA625 Mohave County NE part - MU 21 Jocity;
SSA629 Coconino County North Kaibab part - MU 18 Jocity.
Table 4. Representative soil features
| Parent material |
(1)
Alluvium
–
sandstone and shale
|
|---|---|
| Surface texture |
(1) Silty clay loam (2) Sandy clay loam |
| Family particle size |
(1) Loamy |
| Drainage class | Moderately well drained to well drained |
| Permeability class | Moderately slow to moderate |
| Soil depth | 102 – 152 cm |
| Surface fragment cover <=3" | 0% |
| Calcium carbonate equivalent (0-101.6cm) |
0 – 15% |
| Electrical conductivity (0-101.6cm) |
5 – 30 mmhos/cm |
| Sodium adsorption ratio (0-101.6cm) |
2 – 30 |
| Soil reaction (1:1 water) (0-101.6cm) |
7.4 – 8.4 |
| Subsurface fragment volume <=3" (Depth not specified) |
0 – 5% |
Ecological dynamics
The plant communities found on an ecological site are naturally variable. Composition and production will vary with yearly conditions, location, aspect, and the natural variability of the soils. The historical climax plant community represents the natural potential plant communities found on relict or relatively undisturbed sites. Other plant communities described here represent plant communities that are known to occur when the site is disturbed by factors such as grazing, fire, or drought.
Production data provided in this site description is standardized to air-dry weight at the end of the summer growing season. The plant communities described in this site description are based on near normal rainfall years.
NRCS uses a Similarity Index to compare existing plant communities to the plant communities described here. Similarity Index is determined by comparing the production and composition of a plant community to the production and composition of a plant community described in this site description. To determine Similarity Index, compare the production (air-dry weight) of each species to that shown in the plant community description. For each species, count no more than the maximum amount shown for the species, and for each group, count no more than the maximum shown for the group. Divide the resulting total by the total normal year production shown in the plant community description. If rainfall has been significantly above or below normal, use the total production shown for above or below normal years. If field data is not collected at the end of the summer growing season, then the field data must be corrected to the end of the year production before comparing it to the site description. The growth curve can be used as a guide for estimating production at the end of the summer growing season.
State and transition model
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Ecosystem states
State 1 submodel, plant communities
State 1
Historic Climax Plant Community
Community 1.1
Historic Climax Plant Community
The plant community is made up primarily of mid and short grasses with a relatively small percentage of forbs and shrubs. In the original plant community there is a mixture of both cool and warm season grasses. Plant species most likely to invade or increase on this site when it deteriorates are shadscale, annuals, and cacti. Continuous grazing during the winter and spring periods will decrease or eliminate the cool season grasses, which are replaced by warm season, lower forage value grasses and shrubs.
Figure 4. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
| Plant type | Low (kg/hectare) |
Representative value (kg/hectare) |
High (kg/hectare) |
|---|---|---|---|
| Grass/Grasslike | 841 | 925 | 1009 |
| Shrub/Vine | 112 | 168 | 224 |
| Forb | 34 | 62 | 90 |
| Total | 987 | 1155 | 1323 |
Figure 5. Plant community growth curve (percent production by month). AZ0004, 35.4 7-11" p.z. fourwing saltbush. Some growth in spring, most growth in summer to early fall rainy season..
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 0 | 0 | 10 | 15 | 30 | 40 | 5 | 0 | 0 | 0 |
Figure 6. Plant community growth curve (percent production by month). AZ0005, 35.4 7-11" p.z. Indian ricegrass. Most growth occurs in the spring, some growth occurs in the fall..
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 10 | 40 | 40 | 0 | 0 | 0 | 5 | 5 | 0 | 0 |
Figure 7. Plant community growth curve (percent production by month). AZ3541, 35.4 7-11" p.z. all sites. Most growth occurs in the spring and during the summer rainy season..
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 1 | 9 | 20 | 15 | 5 | 16 | 25 | 6 | 2 | 1 | 0 |
Figure 8. Plant community growth curve (percent production by month). AZ3543, 35.4 7-11" p.z. western wheatgrass. Growth begins in the spring and continues into fall during the rainy season..
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 5 | 20 | 30 | 20 | 5 | 5 | 10 | 5 | 0 | 0 |
Figure 9. Plant community growth curve (percent production by month). AZ3566, 35.4 7-11" p.z. winterfat. Growth occurs from spring through summer..
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 5 | 30 | 30 | 10 | 10 | 10 | 5 | 0 | 0 | 0 |
Figure 10. Plant community growth curve (percent production by month). AZ0001, 35.4 7-11" p.z. galleta. Growth begins in the spring, most growth occurs during the summer rainy season..
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| J | F | M | A | M | J | J | A | S | O | N | D |
| 0 | 0 | 0 | 3 | 15 | 5 | 25 | 40 | 10 | 2 | 0 | 0 |
Additional community tables
Table 6. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (kg/hectare) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Shrub/Vine
|
||||||
| 0 | 112–224 | |||||
| fourwing saltbush | ATCA2 | Atriplex canescens | 56–112 | – | ||
| winterfat | KRLA2 | Krascheninnikovia lanata | 56–112 | – | ||
| shadscale saltbush | ATCO | Atriplex confertifolia | 0–56 | – | ||
| rabbitbrush | CHRYS9 | Chrysothamnus | 11–34 | – | ||
| 3 | 11–34 | |||||
| broom snakeweed | GUSA2 | Gutierrezia sarothrae | 6–22 | – | ||
| threadleaf ragwort | SEFL3 | Senecio flaccidus | 6–22 | – | ||
| plains pricklypear | OPPO | Opuntia polyacantha | 2–11 | – | ||
|
Grass/Grasslike
|
||||||
| 0 | 841–1009 | |||||
| blue grama | BOGR2 | Bouteloua gracilis | 224–392 | – | ||
| western wheatgrass | PASM | Pascopyrum smithii | 168–280 | – | ||
| alkali sacaton | SPAI | Sporobolus airoides | 112–168 | – | ||
| James' galleta | PLJA | Pleuraphis jamesii | 56–112 | – | ||
| vine mesquite | PAOB | Panicum obtusum | 56–112 | – | ||
| Indian ricegrass | ACHY | Achnatherum hymenoides | 56–90 | – | ||
| squirreltail | ELELE | Elymus elymoides ssp. elymoides | 34–56 | – | ||
| sand dropseed | SPCR | Sporobolus cryptandrus | 11–56 | – | ||
| 1 | 11–56 | |||||
| threeawn | ARIST | Aristida | 6–28 | – | ||
| mat muhly | MURI | Muhlenbergia richardsonis | 6–28 | – | ||
| burrograss | SCBR2 | Scleropogon brevifolius | 6–28 | – | ||
|
Forb
|
||||||
| 0 | 11–34 | |||||
| menodora | MENOD | Menodora | 6–22 | – | ||
| globemallow | SPHAE | Sphaeralcea | 6–22 | – | ||
| 2 | 22–56 | |||||
| Forb, perennial | 2FP | Forb, perennial | 17–34 | – | ||
| Forb, annual | 2FA | Forb, annual | 11–28 | – | ||
Interpretations
Animal community
This site is suitable for yearlong grazing by any class of livestock. The close proximity of livestock water calls for special management techniques for sustained production of high quality forage without sacrificing the site because of overuse.
This site offers a fair diversity in the vegetative complex for wildlife. In higher condition classes the site is most suitable to grassland wildlife species. As retrogression occurs the woody species increase and wildlife species utilizing the site may change.
Recreational uses
The site is located on non-entrenched swales and bottoms. It has good aesthetic appeal and in high ecological condition it has a grassland dominance with pockets of brush or scattered brushy species.
Winters are cold and summers are quite warm. Spring and fall are the dry seasons and are typically cool and windy.
Recreational activities most likely to occur are hunting, cross-country riding, photography and wildlife observation.
Other information
Threatened and Endangered Species: Golden eagles and Prairie falcons occasionally use the site for feeding areas.
Supporting information
Type locality
| Location 1: Mohave County, AZ | |
|---|---|
| Township/Range/Section | T40N R10W S7 |
| General legal description | Mohave County; about 8.5 miles south of the Arizona-Utah state line and 4 miles west of the Hurricane Cliffs; Section 7, T40N, R10W. |
Contributors
Larry D. Ellicott
Steve Barker
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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