Natural Resources
Conservation Service
Ecological site R035XB229AZ
Cobbly Slopes 6-10" p.z. Saline
Accessed: 11/21/2024
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 35.2 - Colorado Plateau Shrub – Grasslands
Elevations range from 3500-5500 feet and precipitation averages 6 to 10 inches per year. Vegetation includes shadscale, fourwing saltbush, Mormon tea, blackbrush, Indian ricegrass, galleta, blue grama, and black grama. 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 confertifolia |
| Herbaceous |
(1) Pleuraphis jamesii |
Physiographic features
This site occurs on side slopes of fan remnants and risers of stream terraces.
This site occurs in an upland position. It neither benefits significantly from run-in moisture nor does ir suffer from excessive loss of moisture from runoff, unless denuded of its vegetative cover.
Table 2. Representative physiographic features
| Landforms |
(1)
Fan remnant
(2) Stream terrace |
|---|---|
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation | 1,494 – 1,524 m |
| Slope | 20 – 50% |
| Aspect | N |
Climatic features
Area has a very dry and windy climate that is hot in the summer and cold in the winter. Average annual precipitation is from 6 to 10 inches. Soil moisture regime is typic aridic and the soil temperature regime is mesic. A slight majority of the precipitation arrives during the late fall, winter, and early spring. this winter season moisture originates in the Pacific Ocean and arrives as rain, or sometimes snow, during widespread frontal storms of generally low intensity. The majority of the snow falls from December through February, but rarely lasts more than a few days. The driest period is from late May to early July. Summer rains occur from July through September during brief intense local thunderstorms. The rain is sporadic in intensity and location. Windy conditions are common year round with the strongest most frequently in the spring.
Table 3. Representative climatic features
| Frost-free period (average) | 181 days |
|---|---|
| Freeze-free period (average) | 207 days |
| Precipitation total (average) | 254 mm |
Figure 2. Monthly precipitation range
Figure 3. Monthly average minimum and maximum temperature
Influencing water features
Soil features
Soils on this site consist of soils that are moderately deep to shale.
Surface textures are very cobbly fine sandy loam.
Subsurface textures are gravelly fine sandy loam, sandy clay loam and clay loam.
These soils formed in alluvium and residuum derived from quartz diorite and shale. Slopes are 20 to 50 percent. These soils are well drained.
Typical taxonomic units include:
SSA 717 Shiprock NM - MU's 102 & 265 Camac & 506 Grazane.
Table 4. Representative soil features
| Parent material |
(1)
Alluvium
–
quartz-diorite
(2) Residuum – shale |
|---|---|
| Surface texture |
(1) Very cobbly fine sandy loam |
| Family particle size |
(1) Loamy |
| Drainage class | Moderately well drained to well drained |
| Permeability class | Very slow to moderately slow |
| Soil depth | 51 – 102 cm |
| Surface fragment cover <=3" | 10 – 20% |
| Surface fragment cover >3" | 25 – 35% |
| Available water capacity (0-101.6cm) |
2.54 – 5.08 cm |
| Calcium carbonate equivalent (0-101.6cm) |
5 – 10% |
| Electrical conductivity (0-101.6cm) |
2 – 8 mmhos/cm |
| Sodium adsorption ratio (0-101.6cm) |
5 – 13 |
| Soil reaction (1:1 water) (0-101.6cm) |
8.4 – 9 |
| Subsurface fragment volume <=3" (Depth not specified) |
0 – 10% |
| 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 broom snakeweed and annuals. Continuous grazing during the winter and spring periods will decrease 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 | 163 | 219 | 291 |
| Shrub/Vine | 56 | 78 | 101 |
| Forb | 8 | 10 | 13 |
| Total | 227 | 307 | 405 |
Figure 5. Plant community growth curve (percent production by month). AZ3509, 35.3 10-14" p.z. shadscale saltbush. Growth begins in spring and extends through the summer. Seed set occurs in summer to early 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 | 5 | 25 | 25 | 15 | 15 | 10 | 5 | 0 | 0 | 0 |
Figure 6. Plant community growth curve (percent production by month). AZ3521, 35.2 6-10" p.z. all sites. Growth begins in the spring and continues through the summer. Most growth in this CRA occurs in the spring using stored winter moisture..
| 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 | 27 | 14 | 10 | 11 | 5 | 3 | 0 | 0 |
Figure 7. Plant community growth curve (percent production by month). AZ5104, 35.3 10-14" p.z. sand dropseed. Growth begins in spring and extends into 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 | 0 | 5 | 10 | 5 | 30 | 35 | 15 | 0 | 0 | 0 |
Figure 8. Plant community growth curve (percent production by month). AZ5201, 35.2 6-10" p.z. galleta. Growth begins in spring, most growth occurs during summer rains..
| 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 | 10 | 20 | 10 | 15 | 35 | 5 | 0 | 0 | 0 |
Figure 9. Plant community growth curve (percent production by month). AZ5202, Indian ricegrass, 35.2 6-10" p.z.. Growth begins in spring, most growth occurs in May, goes dormant during summer heat..
| 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 | 15 | 40 | 20 | 0 | 0 | 10 | 5 | 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 (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | Grasses | 202–235 | ||||
| Indian ricegrass | ACHY | Achnatherum hymenoides | 67–84 | – | ||
| James' galleta | PLJA | Pleuraphis jamesii | 67–84 | – | ||
| sand dropseed | SPCR | Sporobolus cryptandrus | 17–34 | – | ||
| Grass-like, perennial | 2GLP | Grass-like, perennial | 3–17 | – | ||
| black grama | BOER4 | Bouteloua eriopoda | 3–17 | – | ||
| squirreltail | ELELE | Elymus elymoides ssp. elymoides | 3–17 | – | ||
| alkali sacaton | SPAI | Sporobolus airoides | 0–7 | – | ||
| Fendler's threeawn | ARPUF | Aristida purpurea var. fendleriana | 0–7 | – | ||
| needle and thread | HECOC8 | Hesperostipa comata ssp. comata | 0–3 | – | ||
|
Forb
|
||||||
| 2 | Forbs | 3–17 | ||||
| Forb, perennial | 2FP | Forb, perennial | 3–10 | – | ||
| Forb, annual | 2FA | Forb, annual | 3–7 | – | ||
|
Shrub/Vine
|
||||||
| 3 | Shrubs | 67–84 | ||||
| shadscale saltbush | ATCO | Atriplex confertifolia | 11–22 | – | ||
| broom snakeweed | GUSA2 | Gutierrezia sarothrae | 3–17 | – | ||
| Shrub (>.5m) | 2SHRUB | Shrub (>.5m) | 0–10 | – | ||
| Torrey's jointfir | EPTO | Ephedra torreyana | 0–7 | – | ||
| bud sagebrush | PIDE4 | Picrothamnus desertorum | 0–7 | – | ||
| plains pricklypear | OPPO | Opuntia polyacantha | 0–3 | – | ||
Interpretations
Animal community
This site is not favorable for grazing by all classes of livestock due to steep slopes and surface cover of cobbles and stones and when snow cover restricts availability of forage.
Wildlife diversity on this site is quite limited due to difficulty of topography and vegetative form and ephemeral waters. This site does provide significant forage for adapted species.
Recreational uses
This site is typified by steep cobbly slopes and north aspect.
Winters are cold, however, moderate spring, fall and summer temperatures are attractive to recreational users.
Site lends itself to activities such as hunting, photography, hiking, rock collecting, and wildlife observation.
Supporting information
Type locality
| Location 1: Apache County, AZ | |
|---|---|
| Township/Range/Section | T41N R30E S20 |
| General legal description | Cow Butte Quad - Section 20, T41N, R30E; 2.5 miles northwest of Toh Dahstini Spring; Navajo Indian Reservation, AZ. |
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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