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Draft. A draft ecological site description is either incomplete or has not undergone quality control and quality assurance review.
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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 35.3 – Colorado Plateau Sagebrush – Grasslands
Elevations range from 4800 to 6700 feet, and precipitation averages 10 to 14 inches. Vegetation includes Wyoming big sagebrush, Utah juniper, Colorado pinyon - cliffrose, Mormon tea, fourwing saltbush, blackbrush, Indian ricegrass, needle and thread, western wheatgrass, Galleta, black grama, blue grama, and sand dropseed. The soil temperature regime is mesic, and the soil moisture regime is ustic 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) Coleogyne ramosissima
(2) Yucca baccataHerbaceous (1) Bouteloua eriopoda
(2) Tridens muticusPhysiographic features
This site occurs on undulating hills of mesas and plateaus. The soil is shallow. The soil surface texture ranges from extremely gravelly loam to extremely gravelly sandy loam. Subsurface textures include very gravelly loam, extremely cobbly loam, and extremely gravelly sandy loam. Slopes range from 1 to 15 percent, but may on occasion may go up to 25%. The site occurs on all aspects.
Table 2. Representative physiographic features
Landforms (1) Hill
(2) Mesa
(3) Plateau
Flooding frequency None Ponding frequency None Elevation 4800 – 6700 ft Slope 1 – 15 % Aspect Aspect is not a significant factor Climatic features
Winter summer moisture ratios range from 70:30 to 60:40. Late spring is usually the driest period, 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 December through February. Accumulations above 12 inches are not common but can occur. Snow usually lasts for 3-4 days but can persist much longer. Summer daytime temperatures are commonly 95 - 100 F and on occasion exceed 105 F. Winter air temperatures can regularly go below 10 F and have been recorded below - 20 F.
Table 3 Representative climatic features
Frost-free period (average) 170 days Freeze-free period (average) 190 days Precipitation total (average) 10 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
The soil of this ecological site is shallow and has been formed from limestone alluvium and residuum. The surface texture ranges from extremely gravelly loam to extremely gravelly sandy loam. A cover of pebbles (60%) is found on the surface. Subsurface textures include very gravelly loam, extremely cobbly loam, and extremely gravelly sandy loam. Calcium carbonate content averages from 20 to 35 percent.
Typical taxonomic units on this site include:
SSA 699 Hualapai-Havasupai Area MU 8 Curhollow.
Table 4. Representative soil features
Parent material (1) Alluvium – limestone
Surface texture (1) Extremely gravelly loam
(2) Extremely gravelly sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderate Soil depth 10 – 20 in Surface fragment cover <=3" 60 – 0 % Available water capacity
(0-40in)0.56 – 1.7 in Calcium carbonate equivalent
(0-40in)20 – 35 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Soil reaction (1:1 water)
(0-40in)7.4 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)25 – 85 % Subsurface fragment volume >3"
(Depth not specified)0 – 25 % 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.
The State and Transition model shows the most common occurring plant communities likely to be encountered on this ecological site. This model may not show every possible plant community, but only those that are most prevalent and observed through field inventory. As more data is collected and research is available, these plant communities may be revised, removed, and even added to reflect the ecological dynamics of this site.State and transition model
Custom diagramStandard diagram
Figure 4. R035XC350AZ
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 CommunityThe dominant aspect of the site is a shrub-grassland. The major shrubs include blackbrush and banana yucca. Grasses are black grama and slim tridens. Forbs are few.
Plants that are likely to increase or invade with severe degradation include blackbrush, broom snakeweed, red brome and cheatgrass.Figure 5. 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)Shrub/Vine 309 – 357 Grass/Grasslike 119 – 166 Forb 5 – 24 Tree 0 – 5 Total 433 – 552 Table 6. Ground cover
Tree foliar cover 0% Shrub/vine/liana foliar cover 0% Grass/grasslike foliar cover 0% Forb foliar cover 0% Non-vascular plants 0% Biological crusts 0% Litter 0% Surface fragments >0.25" and <=3" 60% Surface fragments >3" 0% Bedrock 0% Water 0% Bare ground 0% Table 7. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – – – – >0.5 <= 1 – – – – >1 <= 2 – – – – >2 <= 4.5 – – – – >4.5 <= 13 – – – – >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Figure 6. Plant community growth curve (percent production by month). AZ3504 , 35.3 10-14" p.z. bottlebrush squirreltail. Growth occurs in late winter, spring, and fall. Plants often remain green through the winter..
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 5 15 35 25 10 0 0 5 5 0 0 Figure 7. Plant community growth curve (percent production by month). AZ3531 , 35.3 10-14" 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 1 3 17 18 10 19 20 10 1 1 0 Community 1.2
Native/Non-native Shrub-Grass CommunityThis site functions like phase 1.1, but it contains trace amounts of non-native species. The shrub-grass community will benefit from a prescribed grazing system that will allow native species to compete with the non-native species.
State 2
Native/Non-native Shrub Dominated Community with Scattered GrassesContinual disturbance has formed this site by decreasing the desirable native grasses and increasing the less desirable native shrubs like blackbrush. The non-native species have increased enough to change the function of previous state into this current state. The chance of erosion increases due to increased bareground. Resting this site will provide potential for the native grasses to revegetate.
Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 5–24 squirreltail ELELE Elymus elymoides ssp. elymoides 5–24 – 2 24–48 black grama BOER4 Bouteloua eriopoda 24–48 – 3 24–48 slim tridens TRMU Tridens muticus 24–48 – 4 0–24 Indian ricegrass ACHY Achnatherum hymenoides 0–24 – 5 0–5 muttongrass POFE Poa fendleriana 0–5 – 6 0–5 needle and thread HECOC8 Hesperostipa comata ssp. comata 0–5 – 7 0–14 sideoats grama BOCU Bouteloua curtipendula 0–14 – 8 5–10 burrograss SCBR2 Scleropogon brevifolius 5–10 – 9 0–10 Fendler's threeawn ARPUF Aristida purpurea var. fendleriana 0–10 – 10 0 Grass, perennial 2GP Grass, perennial 5–24 – Forb11 0–5 mariposa lily CALOC Calochortus 0–5 – 12 5–19 Forb, perennial 2FP Forb, perennial 5–19 – 13 0–4 Forb, annual 2FA Forb, annual 0–4 – Shrub/Vine14 238–285 blackbrush CORA Coleogyne ramosissima 238–285 – 15 5–24 banana yucca YUBA Yucca baccata 5–24 – 16 5–14 mormon tea EPVI Ephedra viridis 5–14 – 17 5–10 fourwing saltbush ATCA2 Atriplex canescens 5–10 – 18 0–10 Mexican cliffrose PUME Purshia mexicana 0–10 – 19 0–5 broom snakeweed GUSA2 Gutierrezia sarothrae 0–5 – 20 0–5 Fremont's mahonia MAFR3 Mahonia fremontii 0–5 – 21 0–5 tulip pricklypear OPPH Opuntia phaeacantha 0–5 – 22 5–24 Shrub (>.5m) 2SHRUB Shrub (>.5m) 5–24 – Table 9. Community 1.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Supporting information
Type locality
Location 1: Coconino County, AZ Township/Range/Section T27N. R12W. S27 General legal description Hindu Canyon Quad. - 3 miles north of Plain Tank; Sec. 27, T. 27 N., R. 12 W.; Hualapai Indian Reservation, Arizona. Contributors
Harmon Hodgkinson
Larry D. Ellicott
Stephen CassadyRangeland 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) Karlynn Huling Contact for lead author State Rangeland Management Specialist, NRCS-Arizona State Office, Phoenix,AZ Date 04/17/2006 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
Very minor rill formation is possible on the steepest slopes due to loamy textures, moderate permeability, shallow soils, and rapid runoff, but it is not likely due to extensive cover of rock fragment armor on the surface and in the profile. -
Presence of water flow patterns:
A few water flow patterns are possible due to moderate permeability and low water holding capacity of the soil (cuased by a high volume of rock fragments and shallow depth). There will be more water flow patterns in areas with a lot of bare ground (lacking rock fragment armor) on steeper slopes, especially if they are surrounded by very shallow soils and rock outcrop. -
Number and height of erosional pedestals or terracettes:
Pedestals and terracettes should be very uncommon. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground should not exceed 30% due to high surface cover of rock fragments and bedrock. This site has only 1 inch of available water capacity, so the potential to produce plant cover is very low. Drought may cause an increase in bare ground. -
Number of gullies and erosion associated with gullies:
None -
Extent of wind scoured, blowouts and/or depositional areas:
None -
Amount of litter movement (describe size and distance expected to travel):
Herbaceous and fine woody litter will be transported in water flow pathways. Coarse woody litter will remain under shrub and tree canopies. Litter movement may be greater in areas with very shallow soils and lots of rock outcrop. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
The soil aggregate stability values in one area averaged six under plant canopies and five in the interspaces. Surface texture is generally loam, with a significant amount of gravel. The soil is generally covered with an average of 60% (range 40-80) rock fragments (usually gravels). When well vegetated or covered with rock armor, the soils have a high resistance to both water and wind erosion. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Soil surface structure is platy (weak, thick). Surface thickness is about 2 inches. Color is variable depending upon parent material. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
This site is characterized by a relatively uniform distribution of mostly shrubs with some grasses and a few forbs. There may be up to 15% cover of trees at higher elevations. Canopy cover ranges from 20-30%, with shrubs usually dominant. Basal cover ranges from 2-4%, with shrubs usually dominant. The plant cover (especially basal cover) is reduced by the amount of rock fragment and/or bedrock ground cover. Both cover values (especially canopy cover) decrease during a prolonged drought. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
None. Due to loamy surface textures, soils may be easily compacted, but they are generally protected by a significant amount of rock fragment armor on the surface and within the surface horizons. The soils have a naturally platy surface structure. -
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:
shrubs >>Sub-dominant:
cool season bunchgrasses >Other:
minor: warm season colonizing grasses > forbs = Agave family > trace: warm season bunchgrasses = trees = cactiAdditional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
All plant functional groups are adapted to survival except during the most severe droughts. Severe winter droughts affect shrubs and trees the most. Severe summer droughts affect grasses the most. -
Average percent litter cover (%) and depth ( in):
Mostly herbaceous litter with some woody litter. Litter amounts increase during the first few years of drought, then decrease in later years. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
350-400 pounds per acre (dry weight) in drought years, 400-550 pounds per acre in median years, 550-700 pounds per acre in wet years. -
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:
Broom snakeweed and pricklypear cactus are native to the site, but have the potential to increase and dominate after overgrazing. Utah juniper is another native that can increase and dominate higher elevation areas as a result of overgrazing and fire exclusion. Red brome, cheatgrass and redstem filaree aer exotic annuals that are becoming endemic to the site, regardless of management. -
Perennial plant reproductive capability:
All plants native to the site are adapted to the climate and are capable of producing seeds, stolons and rhiqomes except during the most severe droughts.
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