Natural Resources
Conservation Service
Ecological site R035XI905AZ
Loamy Upland
25-33" p.z.
Last updated: 5/19/2025
Accessed: 06/12/2026
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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): 035X–Colorado Plateau
AZ CRA 35.9 - Colorado Plateau Coniferous Forests
Elevations range from 8000 to 9700 feet and precipitation averages 25 to 33 inches per year. Vegetation includes white fir, ponderosa pine, quaking aspen, Engelmann spruce, subalpine fir ,Douglas fir, Blue spruce , muttongrass, upland sedge, big wildrye, redroot buckwheat, creeping mahonia, dwarf juniper, mat muhly, mountain muhly, needlegrasses, and alpine timothy. The soil temperature regime is frigid and the soil moisture regime is udic 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.Associated sites
F035XI902AZ Loamy Hills 25-33" p.z. (ABCO, PIPO, POTR5)
F035XI903AZ Loamy Hills 25-33" p.z. Cold (ABLA, PIEN)
Similar sites
R035XI904AZ Loamy Bottom 25-33" p.z. Subirrigated
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous (1) Muhlenbergia montana
(2) Blepharoneuron tricholepisPhysiographic features
This site occurs on the deep and very deep soils of the valleys and fan terraces along the wider drainageways that separate the plateaus and hills. Surface soil textures are sandy loam and loam, sometimes gravelly. Slope range is typically 1 to 8 percent, but can be as high as 15 percent. The site occurs on all aspects, and it may contain small inclusions of shallow soils and rock outcrop.
Table 2. Representative physiographic features
Landforms (1) Plateau
(2) Valley
(3) Fan
Flooding duration Extremely brief (0.1 to 4 hours) to very brief (4 to 48 hours) Flooding frequency None to very rare Ponding frequency None Elevation 7200 – 9400 ft Slope 1 – 15 % Aspect Aspect is not a significant factor Climatic features
Winter-Summer moisture ratios are typically 70:30. Late spring and summer is usually the driest periods and early fall moisture can be sporadic. Summer rains fall from June through September; moisture originates in the Gulf of Mexico and creates convective, usually brief, intense thunderstorms. Cool season moisture from October through 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 from October into April. Snow pack can persist for 3-4 months, although it may disappear in exposed areas during prolonged dry weather. Summer daytime temperatures are typically 60-70 F but rarely exceed 80 F. Winter temperatures around 10 F are common and can reach -10 F.
Table 3 Representative climatic features
Frost-free period (average) 90 days Freeze-free period (average) Precipitation total (average) 30 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
The soils on this site are typically deep and very deep, with occasional inclusions of moderate depth. Surface gravel content usually ranges from 2 to 5 percent and is occasionally as high as 20 percent. Most soils have a mollic epipedon that is 16 or more inches thick. Surface soil textures are sandy loam and loam; subsurface textures are mainly loam or sandy loam throughout the profile but may become clay loam to clayey below about 30 inches.
Table 4. Representative soil features
Surface texture (1) Gravelly loam
(2) Gravelly sandy loam
Family particle size (1) Loamy
Drainage class Moderately well drained to well drained Permeability class Moderate to moderately rapid Soil depth 40 – 60 in Surface fragment cover <=3" 10 – 20 % Available water capacity
(0-40in)5 – 10 in Calcium carbonate equivalent
(0-40in)0 – 2 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Soil reaction (1:1 water)
(0-40in)5.8 – 7.1 Ecological dynamics
For state and transition model see ecological group DX035X02FESG09, Kaibab Plateau - Typic Udic - Limestone or Loamy Upland.
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
Custom diagramStandard diagram
More interactive model formats are also available. View Interactive Models
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 1
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityThis is a draft site. This site developed under historic Colorado Plateau conditions, and reflects the natural influences of herbivores, climate fluctuations, and occasional fire. This state includes the native plant communities that occurred on the site prior to European immigration and settlement.
This community is a grass/forb site with a great deal of species diversity, especially with regard to perennial and annual forbs. Shrubs and sub-shrubs are infrequent. In the prolonged absence of fire, trees will encroach on this site areound the edges, especially quaking aspen and blue and Engelmann spruce. terraces along the narrower drainageways between the forested hills, which were historically open, may become forested themselves.Figure 4. 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 495 608 720 Forb 180 248 315 Total 675 856 1035 Table 6. Ground cover
Tree foliar cover 0% Shrub/vine/liana foliar cover 0% Grass/grasslike foliar cover 30-40% Forb foliar cover 10-20% Non-vascular plants 0% Biological crusts 0% Litter 0% Surface fragments >0.25" and <=3" 0% Surface fragments >3" 0% Bedrock 0% Water 0% Bare ground 0% Figure 5. Plant community growth curve (percent production by month). AZ3591 , 35.9 25-33" p.z. all sites. Growth begins in late spring and continues 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 0 15 15 20 25 20 5 0 0 Additional community tables
Table 7. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Perennial Dominant Native 135–270 mountain muhly MUMO Muhlenbergia montana 135–270 – 2 Common Native Mid Grasses 90–225 pine dropseed BLTR Blepharoneuron tricholepis 45–135 – sedge CAREX Carex 45–135 – 3 Occasional Native Summer Perennial 10–45 Grass, perennial 2GP Grass, perennial 0–20 – rough bentgrass AGSC5 Agrostis scabra 0–10 – timber oatgrass DAIN Danthonia intermedia 0–10 – slimstem muhly MUFI Muhlenbergia filiculmis 0–10 – creeping muhly MURE Muhlenbergia repens 0–10 – mat muhly MURI Muhlenbergia richardsonis 0–10 – spike muhly MUWR Muhlenbergia wrightii 0–10 – 4 Occasional Native Spring Perennial 45–225 Porter brome BRPO2 Bromus porteri 0–45 – squirreltail ELELE Elymus elymoides ssp. elymoides 0–45 – big squirreltail ELMU3 Elymus multisetus 0–45 – Arizona fescue FEAR2 Festuca arizonica 0–45 – sheep fescue FEOV Festuca ovina 0–45 – muttongrass POFE Poa fendleriana 0–45 – Letterman's needlegrass ACLE9 Achnatherum lettermanii 0–30 – prairie Junegrass KOMA Koeleria macrantha 0–30 – Grass, perennial 2GP Grass, perennial 0–20 – western wheatgrass PASM Pascopyrum smithii 0–10 – Canada bluegrass POCO Poa compressa 0–10 – blue wildrye ELGL Elymus glaucus 0–10 – Canada wildrye ELCA4 Elymus canadensis 0–10 – Forb5 Common Native Perennial Short Forbs 45–90 white sagebrush ARLU Artemisia ludoviciana 5–45 – redroot buckwheat ERRA3 Eriogonum racemosum 5–45 – aspen fleabane ERSPM Erigeron speciosus var. macranthus 5–45 – 6 Occasional Native Perennial Short Forbs 45–135 Forb, perennial 2FP Forb, perennial 0–30 – western yarrow ACMIO Achillea millefolium var. occidentalis 0–30 – pussytoes ANTEN Antennaria 0–30 – Fendler's sandwort ARFE3 Arenaria fendleri 0–30 – Indian paintbrush CASTI2 Castilleja 0–30 – Wheeler's thistle CIWH Cirsium wheeleri 0–30 – chaparral fleabane EROR5 Erigeron oreophilus 0–30 – gentian GENTI Gentiana 0–30 – showy goldeneye HEMU3 Heliomeris multiflora 0–30 – hairy false goldenaster HEVIM3 Heterotheca villosa var. minor 0–30 – pygmy bluet HOWR Houstonia wrightii 0–30 – lupine LUPIN Lupinus 0–30 – cinquefoil POTEN Potentilla 0–30 – goldenweed PYRRO Pyrrocoma 0–30 – heartleaf buttercup RACA4 Ranunculus cardiophyllus 0–30 – Macoun's buttercup RAMA2 Ranunculus macounii 0–30 – Mt. Albert goldenrod SOSI3 Solidago simplex 0–30 – alpine leafybract aster SYFO2 Symphyotrichum foliaceum 0–30 – 7 Occasional Native Annual Short Forbs 10–90 Forb, annual 2FA Forb, annual 0–18 – trailing fleabane ERFL Erigeron flagellaris 0–18 – Cooper's rubberweed HYCO2 Hymenoxys cooperi 0–18 – fineleaf hymenopappus HYFI Hymenopappus filifolius 0–18 – scarlet gilia IPAG Ipomopsis aggregata 0–18 – yellow owl's-clover ORLU2 Orthocarpus luteus 0–18 – purplewhite owl's-clover ORPU2 Orthocarpus purpureoalbus 0–18 – sticky polemonium POVI Polemonium viscosum 0–18 – white prairie aster SYFAC Symphyotrichum falcatum var. commutatum 0–18 – Interpretations
Animal community
This site is suitable for grazing by all classes of livestock. The site is used primarily as late spring to early fall seasonal range. When grazed with sites with less accessibility and productivity it normally becomes a key management area.
This site has relatively poor habitat diversity in the native plant community. It is primarily adapted to grassland wildlife species except at the edge of timber where it is utilized by many species. Large game animals are migratory onto the site primarily for summer use.Recreational uses
This site has a variety of summer flowers. Its open grassland which abruptly joins the timber edge makes the site aesthetically pleasing. Summers are cool and pleasant but winters are harsh and cold.
Activities for which this site is suited include hunting, camping, wildlife observation and photography.Supporting information
Type locality
Location 1: Coconino County, AZ General legal description Approximately 10 miles south of Jacobs Lake, AZ Contributors
Larry D. Ellicott
Steve BarkerApproval
Kendra Moseley, 5/19/2025
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 06/12/2026 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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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:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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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:
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Perennial plant reproductive capability:
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