Natural Resources
Conservation Service
Ecological site R035XG708AZ
Limestone Hills 14-18" p.z.
Accessed: 12/12/2024
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 35.7 – Colorado Plateau Woodland – Grassland
Elevations range from 5000 to 7000 feet and precipitation averages 14 to 18 inches per year. Vegetation includes one-seed juniper, Colorado pinyon, Stansbury cliffrose, Apache plume, four-wing saltbush, green Mormon tea, needle and thread, sideoats grama, blue grama, black grama, galleta, bottlebrush squirreltail, and muttongrass. The soil temperature regime is mesic and the soil moisture regime is aridic ustic. 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) Purshia mexicana |
| Herbaceous |
(1) Bouteloua curtipendula |
Physiographic features
This site occurs on very low hills, plateaus and steep escarpments. Due to the shallow soils and very steep slopes, this site is subject to a significant amount of runoff. Slopes on the hills range from 30 to 80% while the canyon walls may be practically vertical.
Table 2. Representative physiographic features
| Landforms |
(1)
Hill
(2) Plateau (3) Escarpment |
|---|---|
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation | 1,676 – 2,134 m |
| Slope | 30 – 80% |
| Aspect | Aspect is not a significant factor |
Climatic features
The climate of the land resource unit is semiarid with warm summers and cool winters. The mean annual precipitation ranges from 14 to 18 inches, but is very erratic, often varying substantially from year to year. The majority of the precipitation is received from October through April. This precipitation comes as gentle rain or snow from frontal storms coming out of the Pacific Ocean. Snow is common from November through February. Generally no more than a few inches of snow accumulates, melting within a few days, but may last a week or more. The remaining precipitation, approximately 40 percent, is received from July through September as spotty, unreliable and sometimes violent thunderstorms. The moisture for this precipitation originates in the Gulf of Mexico (and the Pacific Ocean in the fall) and flows into the area on the north end of the Mexican monsoon. Late May through late June is generally a dry period. The mean annual temperature ranges from 46 to 52 degrees Fahrenheit (F). The frost-free period (air temperature > 32 degrees F) ranges from 108 to 151 days (@ 50 percent probability). Strong winds are common, especially in the spring.
Table 3. Representative climatic features
| Frost-free period (average) | 151 days |
|---|---|
| Freeze-free period (average) | 170 days |
| Precipitation total (average) | 457 mm |
Figure 2. Monthly precipitation range
Figure 3. Monthly average minimum and maximum temperature
Influencing water features
Soil features
The soils of this site are well drained, very shallow and shallow to limestone bedrock. Surface textures are gravelly loam to very stony loam. The underlying layers are loam to clay loam. Gravel, cobbles and stones cover 10 to 70% of the soil surface and occupy 35 to 60% of the soil profile. These soils are fertile, and usually have good structure, and take in water readily. Their available water capacity is limited by soil depth. Fissures in the bedrock generally contain fine soil particles and store some moisture. Plant roots penetrate these cracks and crevices, and thus have access to more moisture and plant nutrients than are apparent in the soil. There is a severe erosion hazard when the soil is not properly protected by a good plant cover.
Typical taxonomic unit is;
SSA-631 Coconino County Central MU 54 Tovar;
SSA-707 Little Colorado River area MU 59 Suzmayne.
Table 4. Representative soil features
| Surface texture |
(1) Gravelly loam (2) Very stony loam |
|---|---|
| Family particle size |
(1) Loamy |
| Drainage class | Well drained to somewhat excessively drained |
| Permeability class | Moderate to moderately rapid |
| Soil depth | 13 – 51 cm |
| Surface fragment cover <=3" | 20 – 40% |
| Surface fragment cover >3" | 10 – 30% |
| Available water capacity (0-101.6cm) |
2.54 – 6.35 cm |
| Calcium carbonate equivalent (0-101.6cm) |
40 – 60% |
| Soil reaction (1:1 water) (0-101.6cm) |
7.4 – 8.4 |
| Subsurface fragment volume <=3" (Depth not specified) |
10 – 40% |
| Subsurface fragment volume >3" (Depth not specified) |
25 – 60% |
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 large percentage of trees and shrubs. In the original plant community there is a mixture of both cool and warm season grasses. As retrogression occurs, brushy species increase until they dominate the site. Plant species most likely to invade or increase on this site when it deteriorates are broom snakeweed, annuals, rabbitbrush, and juniper. Continuous grazing during the winter and spring periods will decrease cool season species, which are replaced with 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 | 291 | 346 | 401 |
| Shrub/Vine | 146 | 202 | 256 |
| Tree | 73 | 110 | 146 |
| Forb | 37 | 55 | 73 |
| Total | 547 | 713 | 876 |
Figure 5. Plant community growth curve (percent production by month). AZ3921, 35.7 14-18" p.z. all sites. Growth begins in the spring and continues through the 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 | 14 | 21 | 17 | 18 | 14 | 8 | 3 | 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 (%) | |
|---|---|---|---|---|---|---|
|
Tree
|
||||||
| 0 | 73–146 | |||||
| oneseed juniper | JUMO | Juniperus monosperma | 28–56 | – | ||
| Utah juniper | JUOS | Juniperus osteosperma | 22–45 | – | ||
| twoneedle pinyon | PIED | Pinus edulis | 22–45 | – | ||
|
Shrub/Vine
|
||||||
| 0 | 95–331 | |||||
| Apache plume | FAPA | Fallugia paradoxa | 8–39 | – | ||
| winterfat | KRLA2 | Krascheninnikovia lanata | 8–39 | – | ||
| Mexican cliffrose | PUME | Purshia mexicana | 11–39 | – | ||
| fourwing saltbush | ATCA2 | Atriplex canescens | 8–39 | – | ||
| desert sweet | CHMI2 | Chamaebatiaria millefolium | 8–39 | – | ||
| jointfir | EPHED | Ephedra | 8–39 | – | ||
| bastardsage | ERWR | Eriogonum wrightii | 8–34 | – | ||
| Bigelow sage | ARBI3 | Artemisia bigelovii | 8–28 | – | ||
| 5 | 8–39 | |||||
| rabbitbrush | CHRYS9 | Chrysothamnus | 2–11 | – | ||
| broom snakeweed | GUSA2 | Gutierrezia sarothrae | 2–11 | – | ||
| spineless horsebrush | TECA2 | Tetradymia canescens | 2–9 | – | ||
| threadleaf ragwort | SEFL3 | Senecio flaccidus | 2–6 | – | ||
| 6 | 45–95 | |||||
| Fremont's mahonia | MAFR3 | Mahonia fremontii | 39–73 | – | ||
| pale desert-thorn | LYPA | Lycium pallidum | 11–22 | – | ||
|
Grass/Grasslike
|
||||||
| 0 | 146–286 | |||||
| sideoats grama | BOCU | Bouteloua curtipendula | 73–219 | – | ||
| blue grama | BOGR2 | Bouteloua gracilis | 39–112 | – | ||
| desert needlegrass | ACSP12 | Achnatherum speciosum | 39–73 | – | ||
| 1 | 39–185 | |||||
| needle and thread | HECOC8 | Hesperostipa comata ssp. comata | 22–101 | – | ||
| New Mexico feathergrass | HENE5 | Hesperostipa neomexicana | 17–84 | – | ||
| 2 | 56–224 | |||||
| Indian ricegrass | ACHY | Achnatherum hymenoides | 8–39 | – | ||
| squirreltail | ELELE | Elymus elymoides ssp. elymoides | 8–39 | – | ||
| common wolfstail | LYPH | Lycurus phleoides | 8–39 | – | ||
| James' galleta | PLJA | Pleuraphis jamesii | 8–39 | – | ||
| muttongrass | POFEL | Poa fendleriana ssp. longiligula | 8–39 | – | ||
| muttongrass | POFE | Poa fendleriana | 8–22 | – | ||
| spike muhly | MUWR | Muhlenbergia wrightii | 8–22 | – | ||
| 3 | 11–78 | |||||
| spike dropseed | SPCO4 | Sporobolus contractus | 2–22 | – | ||
| sand dropseed | SPCR | Sporobolus cryptandrus | 2–19 | – | ||
| mesa dropseed | SPFL2 | Sporobolus flexuosus | 2–19 | – | ||
| threeawn | ARIST | Aristida | 2–17 | – | ||
| ring muhly | MUTO2 | Muhlenbergia torreyi | 2–17 | – | ||
|
Forb
|
||||||
| 4 | 39–73 | |||||
| globemallow | SPHAE | Sphaeralcea | 8–20 | – | ||
| brickellbush | BRICK | Brickellia | 6–17 | – | ||
| Forb, annual | 2FA | Forb, annual | 6–17 | – | ||
| Forb, perennial | 2FP | Forb, perennial | 8–17 | – | ||
| aster | ASTER | Aster | 4–13 | – | ||
Interpretations
Animal community
On the less severe slopes, this site is suitable for light grazing during any season of the year by all types of livestock. As the soils are shallow and the slopes steep, grazing should be light in order to protect the native plant community and soils. Heavy use on this site could indicate that more accessible sites are badly abused. This site is very susceptible to erosion, when the native plant cover is removed. This site is usually associated with a canyon that has a riparian area in the bottom.
This site has excellent diversity in the plant community. The trees and shrubs found on the site provide wildlife with important winter cover and food. The pinyon and other winter browse components of the vegetative complex are expecially important for many species of wildlife. As this is a critical site for wildlife, any brush management should be very carefully planned.
Recreational uses
Since this site occurs on rolling hills and steep escarpments the primary recreational activity for this site is hunting.
The site is characterized by shrubs and scattered trees with an understory of grasses and forbs.
The climate is warm summers and cold winters with high winds often experienced during the winter and spring months.
Other activities include hiking, wildlife observation, photography and backpacking.
Other information
The golden eagle and prairie falcon may use this site for hunting.
Supporting information
Type locality
| Location 1: Coconino County, AZ | |
|---|---|
| Township/Range/Section | T32N R4W S15 |
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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